Over 90% of turbo cams sold did not do the job!

In this, episode 115 of PowerTec 10, DV tells why most cams sold for Turbo motors are not value for money in terms of torque and HP gained. What he is telling of here is especially pertinent to Ford's Ecoboost engine line. If you follow his advice here you can save money and avoid disappointment.

[@leonardrice2830]

Wow. I remember reading your book, Performance with Economy, back in the 80’s. Good to see you, sir!

[@aaronanderson6892]

Without any Dyno or track testing, I found that on my Volvo b234 dohc engine; advancing the exhaust cam and retarding the intake cam produced better low speed response and also smoother idle. This was with stock cams. Also, if you watch Richard holdners videos, he shows the effects of back pressure versus boost pressure. Maintaining atleast 1 to 1 ratio, no more, always resulted the best power figures. Anything more than 1.5 to 1 and you see the power drops off tremendously, as you would see in valve float, per say.

[@Low760]

How much power has your b234 made? And Richard also says, a good na cam is a good turbo cam.

[@aaronanderson6892]

Not exactly sure, I haven't had it on the Dyno or done any track testing. If I was to guess, 400-450 at the wheels, in boost.

[@Saddedude]

Yes but on the street a bit of backpressure makes for a fun car. Spools nicely.

[@aaronanderson6892]

That makes absolutely no sense

[@Saddedude]

@aaronanderson6892 watch what all these low backpressure cars do at rhe strip. On the line, tbake and 2 step for 10 seconds just too build boost. A street car with 1.5-1 backpressure just leaves. Sure looses out up top. But a street car hci setup isint set up for all out hp. Keeping some torque on the bank makes for a more enjoyable car too drive.

[@dinosshed]

Turbochargers are jet engines who's combustion chamber is an engine. How I dearly love them.

[@kylemilligan752]

Considering a 4cyl with 1342 firing order. Given a simple shared "log" exhaust manifold, one cylinder will always be on the overlap cycle with both intake/ex valves open WHEN another cylinder is just cracking open an exhaust valve with high pressure blowdown(the highest pressure in the ex cycle). It introduces an egr effect. Pair 1&4 then 2&3 in a divided turbine the whole system improves

[@rondyechannel1399]

Looking forward to you tweeking the Ecoboost Ford motor with your unique expertise!

[@stephanM5]

Dave with you dealing with the sacred cows with respect to cam development you remind me of this quote: "Each progressive spirit is opposed by a thousand mediocre minds appointed to guard the past." Maurice Maeterlinck. This also necessitates having the least restrictive exhaust system possible. Question: What would a cam profile look like with a Kenne Bell supercharger vs a turbo?

[@davidreed6070]

I think superchargers require a different approach, they have not back pressure.

[@atlasintegrations4114]

Or a Procharger?! Running a D1SC on a full roller fully forged 4 bolt main 4.3L V6 Vortec.

[@michaelblacktree]

Another quote that comes to mind, from Grace Hopper: "One accurate measurement is worth a thousand expert opinions."

[@davidreed6070]

I have been waiting for you to do some talking about turbocharging. I read years ago about your work with nimmo. I remember the cam had - 30 degrees of overlap. I am now building my first turbo engine. I tried to pick the turbos to be even pressure across the sides when the engine is in the range where it will be used. ( 4500 to 6500), the camshaft has 5 degrees of overlap. I remember you talking about that in a book years ago , what you said made sense, but no one else thinks like that. I tried to talk with someone else who tests cams and turbos who's consensus I, throw a Cam in there, it don't matter. Anyone that understands an engine knows better than that. I also kept in mind that the pressures on the back side of the valves is going to try to open them. Daren Morgan has spoken a little about turbo engines, he knows but doesn't go into it much. I hope you speak more on this issue. Thank you DV.

[@MikeyAntonakakis]

Fascinating discussion and highly relevant to my project car with VGT turbo! It's a 1987 BMW 325, using the 325e short block (121hp at 4250rpm, 2.7L) with 325i head (168hp at 5800rpm, 2.5L). Low compression ratio due to the "budget stroker" setup, and has an aftermarket 280/280 "turbo" cam with 112deg separation. The turbo is a Holset HE351VE from a 2008-2012 Dodge Ram with 24V 6.7L Cummins. I think about 60mm compressor inlet and turbine outlet, but the party trick is the adjustable turbine nozzle, something like 2.5cm^2 to 26cm^2. So I essentially have a highly variable A/R. Design goal was to maximize horsepower at moderate boost levels while achieving good mid-range boost response, all on a pretty tight budget. In other words, minimize exhaust manifold pressure at high rpm under boost! The turbo's VGT actuator is electronic and uses CAN messages to command its position, so I ended up building an add-on controller to take data from my engine ECU (via CAN), feeding an algorithm I created to coordinate dome pressure wastegate control (using an onboard air compressor) and VGT control based on the ECU's realtime boost target - in short, when there is a high boost demand (e.g. initial throttle application and spool-up), close the VGT an appropriate amount for the current mass flow and MAP conditions, and apply high pressure to the wastegate dome to keep it shut (I learned from experience that the excess exhaust manifold pressure from the VGT could unseat the wastegate, defeating the whole purpose!). I don't have affordable dyno access, so through somewhat rigorous testing on a quiet highway (and frying a set of brake pads in the process using the brake pedal as a speed-control dyno), I was able to map out the system's boost response across the engine rpm range to find the plateau in boost response (psi per second) versus exhaust manifold pressure and/or drive pressure ratio. As drive pressure ratio increases, boost response increases, eventually dropping off as the small turbine nozzle starts significantly choking mass flow through the engine. As boost builds, the algorithm works to maintain a drive pressure ratio of 1.6-1.7, simultaneously applying high pressure to the wastegate dome, until within maybe 2psi of the target "full boost" level. At that point, it ramps the VGT to fully open as it reaches the full boost target and allows the closed-loop wastegate dome pressure control to activate. I don't achieve a 1.0 drive pressure ratio with boost levels around 12-15psi, more like 1.2-1.4 between midrange and high rpm. Maybe higher boost pressure will result in relatively lower drive pressure ratio. All told, at 6000ft elevation (~81% ambient pressure compared to sea level), the 2.7L engine with 7000rpm redline, with a turbo designed for 6.7L diesel application, will reach my target boost as low as 3000rpm (albeit slowly, 5 seconds or so). At 4000rpm (engine speed after a redline 1-2 shift), the boost response is less than 1 second, and with spark-cut flatshifting I don't lose more than a few PSI during a shift. Due to my low compression ratio, as well as a mismatch between piston and combustion chamber shape (using flat-top pistons with a head designed for domed pistons due to my budget OEM internals setup), and very poor squish area for the same reason, I am planning a new engine build with a longer stroke, pistons that are matched to the combustion chamber, and a resulting good squish band and higher compression ratio. This will result in 2.9L displacement and maybe 9-9.5:1 compression ratio. Based on my data, and the fact that the new engine should make significantly more low-end torque, I think I may end up wanting to change to at least a larger turbine wheel. I still haven't visited a dyno, but I do know that rolling onto the throttle in second gear (nearly 75mph), the tires, sticky Dunlop autocross model, spin to redline at 12psi. It's nice to think that I still have room for more top-end power with a bigger turbine wheel, and if I can get the drive pressure ratio closer to 1:1, with a more aggressive cam too (thankfully cams for this engine are cheap!).

[@MikeyAntonakakis]

Oh, and quick back-of-the-envelope calculation on power. Assuming with weight transfer, 55% of weight on rear axle, vehicle is 3000lb/1360kg with me in it, then 748kg on rear axle. If coefficient of friction is 1, then it would take about 7340N to spin the tires, which at 70mph (31.3m/s) equates to at least 230kW/308hp required to spin the tires at that speed. I know it spins the tires at that speed, so safe to assume I'm making at least 300hp to the rear wheels at 12psi, on an engine that generally makes 145hp at the wheels in stock form.

[@patrickmarcello5103]

Looking forward to the turbine housing video!

[@brentonk461ismylostaccount]

Reminds me of when I Had a standard cam 1988 VL Commodore with the factory fitted Nissan 3.0L RB-30, After rebuilding the Engine to turbo spec the standard Jatco automatic torque converter would stall too around 3000rpm and after messing about with it made more power with a original standard naturally aspirated cam than a factory Nissan turbo cam. The original naturally aspirated intake manifold also made more power than the factory Nissan turbo intake manifold. Payed a considerble amount of money for VL turbo injectors only too find I could piss more than those and after getting 3 different sets flow tested ended up drilling out the originals. The turbo used was a hi-flowed Nissan RB-25 turbocharger, built by mr-turbo with Garrett internals equivalent to a Garret 3037s turbo, Not a big turbo and more suited to a 2.0L but didn't stop it from pushing close too 20lbs boost after I ported the exhaust turbine housing it picked up a considerable amount of power, and made even more when I Also used water too air intercooler and changed the airflow meter from draw through to blo-thru It would then Smoke the tires from a RollOn, block long power skids.. but would Not come even close to beating my 10's for the quarter capable Small Block Chev naturally aspirated combo.

[@Cobalt512]

You have no idea how much I've been looking for this turbo sizing info. What book do you cover this in? Im guessing that porting a turbine housing follows the same logic as head porting. Maximizing flow without decreasing exhaust velocity. By the way, you have no idea how inspiring you've been to me.

[@Low760]

Plenty of others cover this info now.

[@ACDGarage_Racing]

Agreed 100% about pressure ratio being a primary factor for seclecting the ideal camshaft for a given turbo engine, i said that in my last video and in doing so ive been asked to make a video about camshaft & pressure ratios many times but i havent gotten around to it... My most recent camshaft video i bealive is much better than my last video which was the one you had liked... This new video shows many undeniable examples of the positive increase in power across the entire curve via optimal LSA with a explanation how it works dynamicly to produce that increase across the curve... I also gave a full explanation of Duration conversions/adjustments according to optimal LSA & a specific Overlap... Someone commented on that video an said they learned more from my video than they did from Billy Godbolds newest book... It had been a long time since i had posted a video due to health related issues, 2023 has not been a good year... Take Care DV... ~ Adam ~

[@DavidVizard]

You are doing good here. Just keep on trucking as they say. Sorry to hear of your health problems. It sure can put a big dent in whatever your plans are. Take care Adam, DV

[@joeprichard3674]

Thank you DV! Please address LSA considerations for turbo engines.

[@StavTech]

LOVE this. This is the first time I’ve seen someone talk or write about turbo cams and me agree with them, as there’s SO much complete BS out there it’s unreal. Usually the ‘info’ is one of two things. Either “you don’t want any overlap” ie they’ve only ever had experience on cars with small turbos. Or “all cams are turbo cams” AKA all you’ve ever dealt with is massive turbos running relatively low power. You nailed it. It’s all about the boost vs backpressure. ❤

[@davidreed6070]

I have heard that all cams are turbo cams, that's so ridiculous it's not worth talking about, a waste of time.

[@michaelblacktree]

If you just want an engine that runs and makes turbo noises, then you can use just about any cam. But if you're trying to optimize your setup, then obviously you need the right camshaft. Even Richard will admit to that. Edit: Yes, it's annoying when you talk to a "cam guy" about your turbo build, and they immediately think "no overlap." And they refuse to do it any other way. (because that's all they know)

[@bcbloc02]

Technically Richard is right pretty well any cam will also work with a turbo. And he certainly has lots of data to show that cams tend to mimic under boost how they do NA as for as power curves. Now he should probably state that as being true for turbo setups that run 1-1 boost vs drive but most besides race deals will probably be close to that. If you want to fine Tune then David is right the pressure differential makes a huge difference in how the cam needs to be.

[@StavTech]

@@bcbloc02 he’s right for your typical V8 with a big turbo running fairly low boost like he does the tests on. He’s right for that and small stuff with big turbos. He isn’t right for the vast majority of smaller capacity engines with smaller turbos and more boost. They sure as hell don’t mimic n/a as they have a ton of pre turbo backpressure.

[@Low760]

​@@StavTechlol. What about when you don't have pre turbo back pressure on a 4cyl like on rb's and 4g's etc?

[@jseal21]

I may have to listen again but I didn't hear you mention where to take the exhaust back pressure measurements from. The manifold side of the turbo or the cat side??? I would assume the turbo causes a pretty large obstruction that'll increase the back pressure

[@v8packard]

When I tell people they need to know the pressure ratio across the system to get the cam right they usually look at me like I am from another planet.

[@scottk2342]

I’ve always said boost as far as turbos go is just a power multiplier. Cam it like it’s NA and keep the cold side and hot side near a 0 ratio as possible thru sizing and it will run well!General rule is 14.7 is a atmosphere which should double the NA power.

[@trailerparkcryptoking5213]

A zero ratio or do you mean zero delta pressure?!?

[@bcbloc02]

On my truck the turbo setup I run runs positive boost to back pressure up until 2300rpm then it starts to fade off being like 52psi drive and 40psi boost at 3500rpm. At partial loads it tends to be a little better at staying closer to 1-1. On the pulling tractors I often run lift approaching an inch and they pick up power over say .600 mainly because the ports tend to keep picking up with more lift they don't go flat till .800 or better.

[@brianalbrecht4423]

thanks D.V....your presatation is always spot on...!...well done..as always...thank u...stay healthy...

[@tedgay8427]

Fantastic information. Thanks for sharing. This video is immensely helpful. Cheers!

[@Seumu990]

Thank you! Great info and good story 🙏

[@markl6769]

Thanks, please keep them coming.

[@steveguest8028]

Great information David

[@amateurism1]

I need more turbo videos! I’m in the middle of a build and I can change course, if needed, your timing is perfect-You just convinced me to change cams, thanks Mr Vizard!

[@VashSpiegel]

Got your book on the Lima tuning, This is info that would be in volume 2. Great info.

[@tanni57]

Top MAN, knows everything about tuning, well done mate

[@needmoreboost6369]

Your knowledge is gold! Glad you put the time and effort in for us all to see! It’s evident in the use of your formulas for cam profile selection that you have given the world! It’s kept me from ruining my engines! I’d have added too much lsa or lift or just followed trends and ended up with a lemon with an inaccessible power band! Thanks mate!

[@daledavies2334]

Mr.David, I take it you are measuring the pressures in the manifolds, exhaust between the valves and the turbine. Years ago someone had bought Paul Neuman's turbo 3 liter Nissan race car and two turbo Accuras. During initial warmup they motored around the Edmonton City Center Airport track sounding like grandma's Cadillac. That Nissan was blindingly fast once they got on the throttle. Tube chassis. Except the roof and firewall and floorpan, every other body panel came off in less than 5 minutes for access. I guess the guy that bought them had not paid as they were not on track on the Sunday. Word was the sheriff came and had them loaded up Saturday night. I do not know what they had for mufflers, but were quiet. The turbos act like a muffler to a point.

[@crazywickedcustoms7272]

Thank you sir

[@Yobettev]

I have watched several of your videos and been EXTREMELY impressed by your seemingly unparalelled level of knowledge. In one of your previous videos you mentioned that you hold 3 day seminars. I tried to look them up and all I have been able to find was a site that clearly hasn't been updated in quite awhile as a lot of the links are either dead or have dates from 5 or more years ago. I would love to attend one of those seminars... but I do not know when they are or how to sign up. I would be very appreciative if you could let me know how to get signed up for one.

[@rayvarnson8976]

Very interesting, never thought about that aspect.

[@bobwhite4344]

great info.

[@SleeperC10]

After a few years in this hobby I can tell you for sure there are a LOT of people that will sell you pure crap that doesn’t do what they say it will do. I appreciate real proven information in these videos. I am surprised there isn’t much reference to the LS engines with how popular they are these days.

[@Staypuff777]

Thank you Mr. Wizard, I mean Mr. Vizard. :) This video is very timely as I just turbocharged my Firebird and did not make the horsepower expected. I am fairly sure this exhaust situation is happening, too much exhaust backpressure due to small turbine housing. I could push the boost pressure way up but I think I may try a larger ar turbine housing first. My cam is 222/227 with 113lsa with minimal overlap. I could only imagine if I chose a cam with a lot of overlap!

[@danielsullivan9865]

I’ve been telling guys for years the turbine sizing is more important than the compressor sizing. This video goes along with exactly what we found with our experience. 26 pounds of boost now we run one to one pressure versus back pressure. Most important thing on the turbo car is pressure sensor, back pressure sensor and speed sensor on the compressor. Without these sensors, you have no idea why your engine has lost so much power at higher RPM. Thanks, David great video.

[@ChurchAutoTest]

The only issue I take with that statement is that you always size the compressor first according to your power goals. So the compressor has to take precedence. Otherwise, yes, turbine sizing is critical. Chasing cam profiles because your exhaust side is too restrictive is a band aid at best. Interesting story, when we were working on one of the first Honda K-series drag cars, we had a problem with overspeeding the turbo because we were used to spec'ing turbos like we did with the older B-series. The K-series head, valvetrain and overall airflow capability were so much better we had to rethink the entire turbo arrangement. Thank god we had instrumentation. Still amazed at how many racers don't have turbo speed sensors.

[@bill2178]

churchautotest your correct most people oversize compressors and then undersize the turbine to try and spool them its amazing how far a little science goes with matching combos

[@trailerparkcryptoking5213]

Where is the proper place to locate the backpressure sensor? Does the turbo speed number matter in general or relative to what is happening with the intake pressure and/or exhaust backpressure? Does the pressure ratio need to be near “1” without the control of a wastegate? I assume you could reach a ratio of “1” with wastegate adjustment, but it doesn’t seem like that alone would create the most efficient system....

[@bill2178]

@@trailerparkcryptoking5213 backpressure is not a part of the equation once you have the right compressor and the right turbine housing the backpressure is fixed and theres not much you can do to change it

[@trailerparkcryptoking5213]

@@bill2178 will BP vary with RPM due to increased exhaust flow/volume? Just trying to wrap my head around it all.

[@robingroeneveld4169]

Agree with you 100%. The only thing I missed, is that the size of the exhaust valve and port may be a bit bigger in comparison to the intake valve and port (which may be smaller) on a turbo engine, compared to a N/A engine. This also has a positive effect by dropping the exhaust backpressure.....

[@alessandroghizzo972]

Another great tech lesson on engines

[@rlprgp62]

Thanks!

[@BarrackObama-ds4jj]

Keep it up david! Amazing youtube videos.!👍

[@KarriKoivusalo]

Great learning package on turbos, I think it's the first thing to know it's the residual energy of the exhaust gas that drives the turbo; I've seen some argue a turbo leeches crank power just as any mechanical does, just through piston acting through exhaust gas and not crank and belt. Interestingly, the performance turbo cams for Volvo B230 engines I've seen are pretty much universally high-lift, low duration and wide lobe separation designs. My cam from IPD USA was a minor head-scratcher to a veteran engine builder with the tall and pointy lobes.

[@approachingtarget.4503]

Nemo wrote a production at the same time you did David. It was also offered along side your prints in summit parts catalog for some years. Turbo pressure from all angles helps cushion the entire rotating assembly. Primary exhaust size and volume dictate the cams' exhaust design. Keeping the turbine as close to the exhaust valve as possible, drives the response of the entire system. Turbo cams are completely different than N/A or super charged applications.

[@scottwilliams5196]

I really enjoy listening to your experience. Not into this ecoboost stuff. Just a common man. Mission Impossible was the very best. I hope you can get back to that soon.

[@patrickmoore1017]

Outstanding tech right here.

[@williamherring5441]

Thank you DV! v/r wh

[@billlittle4285]

Maybe an NA cam can learn something from this!!?? Good video David!!

[@basedsigma5634]

Porsche , in germany , had that TDC EXH closing cam , LONG BEFORE YOU😂

[@Akya2120]

I appreciate you taking the time to share this information. Does the same advice apply to diesels? Also, is it worth chasing the 1:1 EMAP to IMAP in a diesel? In my build I am using a VGT and I will have both sensors to data log and or map off of. I was considering making a map that targets 1:1 with the exhaust vanes.

[@hoost3056]

The brass tube with the holes, where was it installed? Also, can your program handle 4 valve engines?

[@deancrawford2577]

I remember going through the whole turbo cam debarkle about 20 years ago, On one particular build we found that a fast road n/a cam worked by far the best and had better transient throttle response. Exhaust manifold pressure needs to be measured ideally.

[@hyracer6684]

Looking forward to your next video on tweaking the exhaust housing on the 2.3 ecoboost turbo. I have a 2.3 Focus RS which is similar to the ecoboost Mustang but comes factory with a slightly larger turbo. I have already installed the Ford Performance Camshaft which has minimal intake duration increase and extra exhaust duration increase. According to your video, Ford should have maximised exhaust lift and left the factory intake lift alone. Sadly, Ford did just the opposite with the FP cam.

[@torbenalstrup3902]

I was waiting for that EGR comment ;.)

[@hotrodray6802]

🔔😎🇺🇸 Thanks for sharing your expertise.👍😎

[@lukesimeon5756]

Great video DV! Two questions if I may... would you please explain the brass tube (my mind went straight to an emulsion bleed lol) and just to verify you said at a 1 to 1 boost to back pressure ratio we should treat the cam as naturally aspirated ... does this include the Lobe Separation Angle ... thanks

[@DavidVizard]

Yes!

[@lksf9820]

I've been speccing cams and building them into turbo engines for many years with great success so can only agree with you. Especially about ex valve size although my approach was slightly different (but essentially the same). I'd put the head on the flow bench and when the ex valve stopped giving much increase (with more lift) then that decided the ex valve max cam lift. Up to circa 500bhp (from 2 litres) there was no point in giving it any more than about 9mm lift. Over that output and up into the 750bhp territory then i'd fit bigger ex valves (only) and give the ex valve more duration, open it earlier, but actually not give it much more lift. The ex valves on those engines were a bit on the small side to begin with so benefitted from being bigger at those bigger power increases.

[@mikebrooka9395]

You talked about the pressure difference between hot and cold side. BROVO! I have looked at turbo cam cards and have found nothing but trash. I have been sitting around with a mower engine, degree wheel, and several full notebooks of calculations. Isky and Howard's are close to what I seek. Howard's seems to be the most likely prospect for a custom cam. Mikel

[@pmd7771969]

If we know the pressure ratio then how do we select the best cam

[@greghaupt1818]

How do you measure back pressure and what steps to take to reduce it some.

[@greghaupt1818]

Perhaps at the planning stage of the heads would leaving the inlet valve diameter std and putting in the biggest diameter exhaust valve as possible and machining as needed. Just thinking this would help the imbalance.

[@jumpsuite]

Not a turbo guy but all sed and done I crossed that path just thinking on tubos alone David v.

[@hendersongibbs5615]

Hi David I been a fan from the 70 tees I read you book on the HB vauxhall viva. Now in in the process of building a Honda k24 turbo for quarter mile. I need you advice on where to buy and was to buy to make 1400 hp. Thanks in advance.

[@ambershade8583]

Does this mean also that in a dohc engine I could just rotate the cams until I get it to a more fitting point? With earlier exhaust it should be giving a little less energy to the piston, but still give it to the turbine and if this provides less problems at the intake... or it doesn't because exhaust pressure would also rise and then it'll only get worse?

[@mv6160]

Is there any chance getting help with timing aftermarket cams on stroker 2jz vvti engine?

[@patrickmazzone9066]

would you recomend comp cam lifters 29001 against lifter and cam failure solid flat tappet cam. Would you please let me know

[@justlost2010]

How would an average person measure back pressure? That equipment or tools would be needed? How does variable cam timing affect the turbo and back pressure. 2017 fusion 2.0 turbo

[@edpetrocelli2633]

Mr. Vizard I`ve been meaning to ask you but keep forgetting, when you talk overlap is it at .050 or advertised? This was a good video, your words made a lot of sense.......Thanks

[@cjespers]

Thanks for the video. Best tech anywhere. God bless.

[@chevyluv7216]

@DavidVisard Mr David I have built a 572 bbc and want to run a turbo cam current cam is for a Procharger, I want to run an atypical cam with around .770 lift. What do you recommend?

[@stevenkirk2563]

Richard holdener had the same view as you David. Tested and proven.

[@onegative8887]

How do you know the intake exsgaust ratio

[@adampatterson707]

David does this information work the same for a diesel engine??? I'm going to be rebuilding a diesel engine for my wife's Jetta. Thank you for sharing your vast knowledge.

[@haro997]

What type of cam is good for port fuel injection and a permanent functional hood scoop with a seal. I have a stock high lift cam. It's just a stock cheap cam for my budget build 318 magnum but it's a 1.5 rocker and I'm using 1.65 so it works out to about .455 lift. Melling mc1334. I don't expect an answer just commenting

[@CatDaddyTuning]

TLDR: Bigger exhaust housings and Downpipes tend to make the biggest difference in how much power your engine makes. And how it spools

[@needmoreboost6369]

Yeah turbo size makes a huge difference but As opposed to choosing the correct cam for the desired task? This isn’t about bolt on modifying engines! The engines desired task, Turbo size and cam profile should go hand in hand! Big nasty cam and small turbo? Nah it doesn’t work for crap! A lot of over cammed engines are still chocked by back pressure! They could make a bigger and more useful power band with less spent on the engine and less mechanical stress using a better suited cam! It’s not all about a dyno number! It’s how much of that number is accessible in use! There’s nothing better than driving past bigger cammed engines like they are down on power for some reason lol

[@Adamu98]

I live near san bernardino. In fact its some of my stomping grounds.

[@jpfreeman3906]

Hello DV, question: does this also applies to diesels??

[@trentdawg2832]

Would an ASA cam work with its 225/236 - “.525/.525” - 110LSA…i love the way this cam sounds but i wanna add boost

[@joe-hp4nk]

What is the pressure ratio across a NA engine? If the lift on the intake is 1/3 the valve diameter, what should the exhaust lift be? Thanks.

[@vigor911]

Assumption would be 1/3 of exhaust valve diameter since he didn’t differentiate between calculation for intake and exhaust.

[@salvatorehayes2753]

17:00 Rough Estimate Of Valve Lift Is (Valve Diameter x 0.3) = Lift. Question. Is This Per Each Valve In A 2 Valve Engine. Say Intake Valve Is 1.9" And Exhaust Valve Is 1.56" So Rough Target Gross Lift (After rocker ratio) Would Be 0.570" For Intake And 0.468" ?

[@Drunken_Hamster]

I notice that 0.3d is bigger than your 0.25d spec for camshafts, otherwise. Why is that? If the curtain area is equal to the valve diameter area, won't you still see diminishing returns by going bigger? Also, with turbo cams, should you still consider the LSA the same as you do with NA cams? Lastly, if you were to spec a dual pattern cam, is it better to have more exhaust or more intake duration, assuming the total overlap was unchanged and the two opening events were optimized?

[@trailerparkcryptoking5213]

Maybe I missed it somewhere, but where is the exhaust backpressure measured for this ratio? At the turbine intake?

[@CatDaddyTuning]

Tapped into the exhaust manifold

[@NMX777]

I really feel like I'm lost now. I'm building a Chevy 250 inline 6 and I want to put a turbo on it but I have no idea how to determine what cam or what turbo I should be running. I'm trying to get all of my power from idle up to 4000 I don't care about anything above 4,000. I want it to pull like a bull and hopefully get good mpg.

[@mariusfridlund55]

1:1 is the goal

[@ZEPRATGERNODT]

I’ve been in the parking lot where PT Turbo is (multiple businesses in the center) and have heard about them for years! Great to know that Vizard has a seal of approval for them. I’m looking forward to going there when I decide if I’m going to build a turbo 302 or a 2.3L. Good to know there is a great resource that David approves of being close to home.

[@gedas3419]

Hi David, would you advise adwancing exhaust cam on turbo 4banger dohc engine to maybe find some extra power?

[@CatDaddyTuning]

Usually most stock engines respond best to a little intake advance and a bit more exhaust retard

[@buildingracingvideos4714]

Why would I need a special cam just because the air density has been changed?

[@tehbonehead]

Put a "turbo" cam with decent overlap and duration in my SBC as a way to lower my dynamic CR. worked pretty good for that... 😂

[@Saddedude]

When talking about overlap how do you calculate it. Do you look at 0.006" or 0.05? There are lots of cams that produce negative overlap at 0.05 and grossly positive overlap at 0.006

[@Saddedude]

@PS_00700 yes but there are two different duration figures. .006 and .050 are grossly different when looking at overlap

[@donbrutcher4501]

What effect does advancing or retarding the stock cam have on a street turbo'd engine? Would also seem that changing rockers to ones that have a higher ratio but slower off the seat and faster at mid-lift would be helpful.

[@DavidVizard]

Down the road aways we will be dyno testing that for you guys. If you are a subscriber you will be notified!

[@poncethegayboi]

Amazing and true. Why my turbo build couldn't get off its face. Thought about using nitrous to boost the turbo. Didnt know exhaust was already..... Exhausted

[@hankclingingsmith8707]

I would add that larger ar exuast doesnt loose boost up high, only lower rpm.

[@CatDaddyTuning]

Might lose boost but usually there’s a point where it makes more torque at a lower boost number.

[@hankclingingsmith8707]

@@CatDaddyTuning midrange or upper rpm only. I've run all different ones. The guys that build turbos like kc are spot on with the facts about this

[@amateurism1]

Question Mr. Vizard: If I have a turbocharger that is dampening or removing the air pulses from the intake that make the k&n filter work, should I stay away from the k&n? I’m building my first non naturally aspirated engine and normally go to these filters, but I’m a little wary for this particular build. Any insight is appreciated. I’m assuming a turbo will create a significantly more steady air flow, but that could be a poor assumption.

[@DavidVizard]

Good guess here. Yes the K&N filter does not work quite as well on a turbo motor but they usually add an extra layer of cotton filtration material and control the amount of oiling done to a minimum.

[@amateurism1]

@@DavidVizard thank you sir!

[@rogerstill719]

Are we talking about duration @.050 or advertised duration?

[@Tony-ib2vm]

n/a cams work with superchargers(when IM pissies>EM pissies)... The pressure differential clears the chamber during overlap.

[@DAVEITTERLY]

How does a basic shade tree mechanic measure the pressure ratio? I have Holset hybrid HX35 or HW35 set for a V8. Either 351W platform or big block 460. Project is stalled but I do have a 1970 full size Ford car with a big engine compartment.

[@CatDaddyTuning]

Weld or put a brake line in the exh manifold then run it over to a boost gauge

[@DAVEITTERLY]

A boost gauge? Really? I need to rewatch the video, can't exactly remember. But are you sure?@@CatDaddyTuning

[@stickman-1]

Again, thank you for your knowledge Mr. Vizard. (you should just go ahead and change it to Wizard.) Anyway I have a question: what about an open exhaust turbo car? Ie, out of the turbo, to a downpipe and that's it? Now what do you say about the camshaft and general? (Treat it as a 5000' below sea level N/A engine?)

[@trailerparkcryptoking5213]

The backpressure is measured between the exhaust valve and turbine inlet....you are assuming pressure out the turbine outlet.....😂

[@stickman-1]

So in the header. @@trailerparkcryptoking5213

[@Christdeliverme]

Every one of these guys or anyone makes X claim, they are doing so from the perspective of the generality of their experiences. So in other words there are rules of thumbs we can use to understand things quickly and stay out of the weeds... But engine are nuanced. This is why each platform has their own development curve. Some things are true across every vehicle. But as usual this aren't always an on/off switch but sliding scale each affecting one another. Putting a set of turbo cams on a factory anything these days is a terrible idea because almost all of them run turbos off the map, stock. You increase the VE of the engine as a pump (ignoring ratios) and all you do is absorb more boost from what the turbo generates, putting the turbo even farther out of the maps. Additionally, there are several strategies out there. The Yahmaha head on the 2JZ-GTE for instance was designed primarily for boost. It sacrificed CFM for convergence pressure at the back of the valve and velocity. So when David talks about 20 psi (i assume psig) he forgets the trade in flow for pressure made when intake ports converge. The aggressiveness of this dictates the effects of those sliding scales, those sacrifices. CFM for RPM. Increase in boost changes both the starting and ending pressure. What strategy are you going to use? No intake or exhaust resonance tuning for energy conservation for response, keep overlap high down low where EMAP is lower, make the engine look bigger to the turbo, spool it faster, then phase the cams so there is less overlap but more dynamic pressure, just let octane, direct injection and the side of the engine take over? (Boost is falling off) So many strategies, all can be effective for one reason or purpose. For instance some people want their 4 or 6 to behave like a diesel down low. Others - tuners want there to be urgency allthe way to redline. So cam selection is predicated upon what the ancillary development choices are including smoothness and emissions. But also how did we design the head to begin with. Some people play to the strengths of an engine and others modify it to make the weaknesses less of a downfall In the 2J's instance those cylinders wont fill well below 3800 rpm. That's why one turbo was used in sequence. For people that try to get that engine to make 400 wheel torque below 4000 rpm its really going to sacrifice performance up top without exotic fuels, strokers and compression. Whereas some 3.0 6 cylinders hate making power over 6000 rpm and sizing components for that life might make you the same power at a couple psi less - you've also thrown away 60% of the engines powerband... And at the same time someone might just want just that. So far one of the only engines I've been truly impressed with recently is the RS3 for its displacement. It can spool a turbo and make power just about everywhere at low medium and high horsepower. B58 in the 6 port is nice. Those are some decent modern engines.

[@markhenke6043]

When will you be posting machinery and tooling on your site?

[@DavidVizard]

Soon

[@davidreed6070]

The Nimmo axiam theory.

[@richardsalazar17]

thanks david id like a 1000 rwhp

[@danielsullivan9865]

Easy, if a V8

[@shoominati23]

David you failed to say what this magic tube with holes is and where it should be located? Also, you never posted the follow up video a year or so back when you said you had an ignition system that works on any motor

[@DavidVizard]

Hy Shoom I did not forget to say that - I intentionally left it out so you all keep guessing.

[@lukesimeon5756]

Oh crap lol my mind guessing usually doesn’t add up to much

[@ericabercrombie6780]

Hi David, got a (normally aspirated) cam question here and figured this would be a good place to post it. I noticed in the past you have endorsed Prestige Motorsports in the Charlotte area as a great builder. I have one of their 383 SBC’s that made 450 ft lbs torque (right in line with their advertised figure.). But this is around 1.17 ft-lbs per cube, which is wayyyy off from the numbers you like to see. I’m assuming their cam selection for these 383’s must be way off? Any thoughts?

[@v8packard]

Not to step on DV's toes, but I am curious about your 383. What is the compression ratio, connecting rod length, cam spec, and cylinder heads? I have regularly seen 490 to 530 ft lbs from street 383s with decent to good heads.

[@ericabercrombie6780]

@@v8packard I'd have to pull up the spec sheet on the thumb drive to get exact numbers, but the engine is 9-ish to 1 on compression, 6" rods, I think cam was around a low 220'ish duration with 106 or 108 LSA. Prestige Motorsports uses their own in house as cast heads, but as I understood they're basically copies of AFR's enforcer series (I think 195's) with 2.02/1.60 valves. Probably something like the Chinese Pro Comps?

[@v8packard]

@@ericabercrombie6780 I am familiar with the heads. They are a Chinese copy of a Dart 200 cc head. Which is a very good head, if not a little big for a 383. The copies are sold by many companies, including AFR as their as cast head. They can benefit from proper porting, but I have personally measured the intake runners at a hair over 200 cc as cast. In your combo, going from 9.5:1 compression to 10.5 - 11:1 could give you 20 to 25 lb ft of torque, easily. I say that based in personal experience. I would also use a cam with a 106 to 107 degree LSA with those heads. I actually would use the AFR CNC ported 190 cc heads with the 2.05 intake valve. I would probably install the cam on a 104 degree intake centerline. And I tend to favor a Holley vacuum secondary 4150 that starts out as a 750, but gets an 850 base and modified down leg boosters.

[@ericabercrombie6780]

@@v8packard thanks for the tips. I'll pull up the exact specs when I can get home and look at the sheet to make sure I'm giving you 100% accurate info. I know the engine is advertised as a 10:1 but when everything was cc'd out I recall it being less than that on their build sheet.

[@ericabercrombie6780]

@@v8packard Ok so exact calculated compression is 9.4:1. Heads are 180's AFR/Dart replicas (not 195s). Cam spec says 224/230@.050. LSA is 110 with 106 intake CL. 1.6 ratio roller rockers. Lobe lift on the cam card is listed as .335/.340. Torque peaked at 453 ft-lbs at 4,500. HP was 437 at 5,900.