We can't make any boost!!!

[@ryanlazarus7821]

Everyone of your videos is so informative its crazy. I really appreciate what you're doing for the car community. Keep up the amazing work and thank you.

[@gavwilldo]

I’ve seen a single 80mm on a 346 inch LS that wouldn’t make any boost rear mount until near 7krpm, so a 632 with 2x 80mm turbos sounds about right it would have issues trying to spool up. Exhaust gas expands a lot more than you would think with heat so there is a whole lot less exhaust gas volume just from how much it has cooled by the time it gets to the back of the truck than straight out of the heads

[@jodycordell1972]

I agree 👍 the further you plumb it the less pressure you get turbos are designed to be close to the head.

[@elite6876]

Smaller ar housing and turbine wheel would help it to build boost easier but would limit how much boost it can make

[@jodycordell1972]

@*eLiTe* Yes, exactly why you shouldn't be trying to run turbos 6 feet from engine

[@rotax636nut5]

Spot on

[@elite6876]

@joseph cordell I know. But you can make remote systems work just as good if you have everything set up right, it's just hella harder. But yes I was agreeing, I was just stating an option that could help it but wouldn't solve it. I've had remote mount and also engine mount and had issues and success with both once kinks got worked out. But yes remote is definitely alot more work and harder to be controllable

[@Slazee]

You know its a good day when Steve uploads

[@nickerbocker759]

Sunday’s are usually dead on the tube. Steve to the rescue lol

[@KimiWallrus]

I laughed

[@JeroddDentonBock]

Facts

[@madzzz4416]

I see this comments everywhere idk why its always on the top of comments everytime i see

[@supercheapautotv]

We had this problem on a 427 while designing the rear mount system, the biggest plug in the exhaust is always the turbine, so you need to lower the diameter of the hot side piping, its allowing the gas to expand and lose velocity, i would probably go down a size or 2 rear housing as well, but the location itself should be fine to make 2000+ easily with that 632 we are at 1800ehp in a 427 heat is important but we found the velocity and volume of the hot side had more of an impact on spool time than wrapping the exhaust though it cant hurt to do that to gain a few hundred RPM earlier spool once you have the bones of the system working

[@chriscadman6379]

Steve has a great media/you tube personality. This is good stuff. Always entertaining. Except for Dewy, a real trouble maker!

[@AB-80X]

Here's a suggestion that will look cool. Keep the turbos in the back and put a 14-71 on top. Make a compound setup🙂

[@kdsboosted4954]

Yes I agree! I'm just finishing up a little twin turbo supercharged 396 build can't wait to fire it up.

[@Berm_Blaster]

I've always heard those combos never work

[@bigblockjess617]

That truck is flippin awesome

[@JonHop1]

Thing is crazy! I wish I had money like that to build something of that caliber!

[@rexschimmer7394]

Steve, I think the problem is that the exhaust gases from the engine have lost to much heat, energy, by the time they get to the turbos. You might try double wrapping the exhaust with ceramic tape from the engine back to the turbos to retain some of the exhaust heat (energy) also you could consider using smaller exhaust tubing to get the exhaust velocity higher, again I would double wrap with insulation. I assume that this is a gasoline engine, convert it over to one of your drag and drive methanol/gasoline setups as methanol puts out considerably more exhaust gas volume and should increase the flow and energy in the long exhaust system. That is a great looking pickup and butchering the hood and having the turbos mounted above the hood would really look hookie. Always great to watch your videos!! Rex

[@somethingsomeonesaid6455]

I was thinking the same thing about wrapping/insulating the exhaust tubes from the engine to the turbo; save some of that heat/expansion pressure.

[@MrJermbob]

Slash his dyno wont hold load on the motor allowing it to make boost. Lol. Dynocom dynos are junk. No need for insulation and insulation does not give hundreds of hp gains.

[@ShreverBeaver]

I agree with the smaller tubing. That crossed my mind the minute they talked about mounting distance.

[@MrJermbob]

@@ShreverBeaver Load the motor. Make the heat. The turbos would have spooled even with the over sized exhaust housings.

[@MrJermbob]

​@@ShreverBeaver No need thats a waste of time.

[@tiredofthetyranny9874]

Damn he put a lot/ A LOT of work into that truck!!!!

[@K-Effect]

I’m guessing the further away you put the turbos the more plumbing you’re going to have and that plumbing is like a tank on a air compressor. The bigger the tank the longer it’s going to take to build pressure/boost if any at all, especially if the turbine wheel is big

[@ZZZracing]

It'd be a great test to see if spool valves make a big difference on this application and allow it to spool (They block the 2nd scroll until a certain psi is achieved, then open up for full flow)

[@redpillpirate111]

Just need a blower to build boost to the turbos 😁

[@stevemorrisracing]

😁

[@danhammond8406]

Superturbocharged engines are true monsters

[@brandongreene3213]

Oh hell yes!

[@jarredflynn]

Very surprised the turbos wouldn't spool with so many cubes! Shows what part the piping efficiency plays with turbo set ups at high power applications.

[@approachingtarget.4503]

It's the pressure on the exhaust turbine that builds boost. With the rear mount. The length of total pipe area will not build up pressure enough to build boost. It's like a balloon. It takes a bunch more pressure to make a big grow than a small balloon. I ran the rear mount single turbo system that was mounted behind the rear axle. The pipe size required to produce enough pressure to drive the turbine was 2". Obviously reducing the amount of power the entire combo could make. You could still use a rear inlet position, but the exhaust turban needs to be within the high pressure zone of exhaust. I doubt you want to run a shaft from the engine compartment exhaust turbine to the bed mounted intake turbine.

[@MsLoneWolf4]

i have only three ideas. causing that. one too much volume space build the pressure to spool up the turbos. two the longer pipes adding to much restriction counting both sides. third thought of this while remembering about 2 strokes tuned pipes is the pulse timing is far out that it would never spool large turbos and smaller ones would still be under utilized. im most likely wrong but oh well.

[@pete1208]

Big hello from Ireland to Steve, Kyle and the whole SM Crew. You guys do beautiful work

[@TravisFaley]

That truck is so sick!! 🔥

[@parsonsenergy]

Another great vid Professor!! Perhaps running a smaller exhaust pipe to the turbos Will to get the exhaust velocity up.. also, perhaps running a big single turbo and let the engine run that might be a better option than tearing down months of work.. Love you classes, your son is awesome what a partner to have…

[@stevemorrisracing]

Yep

[@slfrules1]

That makes sense. It's gonna be darn cool when it's sorted!

[@Dont-come-at-me-24]

Do a compound turbo set up , smaller turbos up front that then spool the larger ones at back , so nitrous work well directly feed into the turbos. Volvo use compressed air to get “instant boost” or there’s always the supercharger option

[@tomp538]

my first thought as well.

[@cantstandya1983]

As usual, the “caution” at the beginning of each video is correct…😆….love this channel

[@lewismocaby3646]

Just clicked on, was in Keith’s hometown just 20 minutes ago. Forgot all about this project, looking forward to seeing what y’all come up with. 👍

[@strykerentllc]

Boyes Law applies and when factoring in volume & resistance, or lack thereof, there is a way forward. An easy way to think of a correlation is a simple garden hose with and without a nozzle on it. With a nozzle, water exit velocity increases while volume diminishes. Without, pressure is low and volume is high. The Aussies run rear mounted spoolie-bois in their ute' cars without issue

[@PKpapa-kd1lb]

Try a velocity stack style exhaust and make pressure in the exhaust and then move the turbos to the sub frame near the cross member and u should be good u can also use a smaller output diameter from the boost side and go to a 4 inch large intercooler and come back down to a smaller diameter agian after the intercooler it creates a pressure charged system that spools fast and hold smooth boost and use a gate controller to increase the spring and give u double the boost earlier

[@-Master_Of_Disaster]

Maybe you could downsize the exhaust pipes to the turbos to build up more gas pressure? That was my first thought. Because those pipes are looking incredible big for such a long way from the engine to the turbos in the back. I think you're loosing a lot of power in there.

[@stevebeavers3754]

He's in my neck of the woods. Great looking build!

[@mikehunt8968]

Back mounted is just too big a volume of pipework to build up enough pressure, a bit like fitting a huge aftermarket intercooler will increase lag if nothing else is tuned up to match... when manufacturers fit on turbos, they always fit them right on the exhaust manifold, as close as possible to the exhaust ports....

[@raykaufman7156]

Cool truck. That "wrecker boom" needs a Top Fuel wing mounted on it!

[@saleen367]

Just an observation ... that much length and size of exhaust along with the massive intercooler would be hard to make boost pressures IMO. Thats a lot of volume, twists and turns, especially below 4000 rpm to run 10' back, thru the IC and then forward again. What you're experiencing is a intake/exhaust tubing volume issue. It looks trick as hell though.

[@JonHop1]

You get to work on some of the COOLEST builds and cars ever man! LOVE that truck!

[@daringibbons7010]

Question.... Would it have anything to do with the size of the exhaust pipe running to the turbos? Maybe if you down sized the pipe it would push more pressure through the pipe to spin the turbos? Just a thought?

[@scottholbert2742]

I'm guessing that the turbo guy already had that figured out. But I thought that too during the video myself

[@steveh5587]

That’s what i was thinking also

[@dansmith207]

Well turbo guy apparently thought this setup would also work. 😂😂😂

[@jamesklassen4617]

Don't no what happend to my post maybe because it had a link in it anyway..... I am a mechanical drafter working with hvac systems designing ducting for an engineering company. From what I understand there is not enough energy left to spool the turbos. I think your problem is friction loss. Its the reson port and polish adds hp. The air traveling down the tubing is slowing down to much. This can be reduced by making the tube bigger. Nicking it up to larger size at Heder then down agen at turbos and same with intake side. The other thing is make sure everything is as smooth as possible and get rid of as many corners as you can. If there I'd an intercooler in there get ride of it your loosing more power then gaining at that distens away from the headers. As an alternative location is there too in them big feeders? Anyway hope this helps.

[@mattt83]

Quick test could be to block 1 side of the exhaust housing scroll, if it works get quick spool valves to open the blocked side once spooled up.

[@rodneymunsterman2287]

Hi Steve, great content Here are my observations as a seasoned diesel tech. Turbos are not driven by exhaust flow but by heat energy, they convert heat energy into kinetic energy to spin the shaft. This is proven by measuring exhaust temp before and after the turbine, where does that heat go? Question... Is the exhaust piping completely insulated from the exhaust port to the turbo turbine housing ? With the distance the exhaust gasses need to flow you may be loosing a lot of the heat energy thru thermal rejection before it reaches the turbine.

[@nicksoverhaulandfabworks]

I have researched a lot on rear mounts for big power you have to make an exhaust manifold like a 2 stroke . Small big small in to the turbo in order to spool the turbo

[@thegdfp6447]

Your frustration is clear. Sorry to see that. Having the client change plans makes life tough for a people-pleaser builder. Turbo guy said the smaller V-band housings would work for the power goal. Disagree? If the big ones won't spool, smaller shouldn't be a restriction. Unless the exhaust heats up a lot once it's really spooling? Diverters to push through one side of the turbo inlet until it spools?

[@truegret7778]

Thats a real shame..... it would be awful, to me, to cut into that beautiful hood. I am surprised so much energy is lost with the turbos back there. I have seen a few truck videos with a similar setup (I don't know the motor or turbo combo) and they seem to make a lot of boost. It would be interesting to see what an EGT would tell you if you run a pair near the turbos. Cool ride for sure.

[@scottk3439]

Steve, since i stayed at a Holiday Inn Express last night, I have no clue how to make boost, but man I love your videos.

[@finnroen2334]

It is kind of funny to see you big guyes with high budgett stuff struggle with the same things we civilians struggle with. We had to put modified GT35 V-band turbinehousings on a pair of SX-E269 to get them to spool on a 5.3. :) Delta P is 1:1 at peak power 1150 hp at the hubs.

[@joebloggs2635]

A quad turbo (compound) setup about rear window height would look absolutely sick.

[@MakingStuffUp1]

hot side impeller needs to be a lot tighter fit if its not getting plasma?

[@movingon5951]

Having been in the towing business I love the looks of the truck. I recently sold my 69 Camaro to retire overseas, so now I can only enjoy my love for street rods passively. Steve, your the goat of engine builder's. Thanks for all the Great content....

[@NINEWALKING]

I remember like 15 years ago there were those companies making rear mounting turbokits. One of those that delete end muffler and place there turbo. Epic lag, losing boost, low efficiency. Everything was wrong with those setups. I thought like for the hot side of the turbo you do not need temperature and having way colder gasses pushing the turbine would be easier on oil and turbo would last long time. But as many other things in life I was wrong. Energy is energy. Turbos like hot exhaust gasses and closer to the engine more of the energy of those exhaust gases is converted into the mechanical work and compressor will do more work as well. Result in way efficient turbo and if the pluming is done right way less turbo lag. Then BMW brought Hot V configuration to mass car production and everyone else jumped on it. Well simply it is more efficient setup. Sure it is going to heat up oil more being mere inch from the exhaust runners but it is damn efficient and reduces lag. Sure in racing lag cane be prevented but why having it in the first place? Less lag is better. So yeah I have learned heat lost in the long exhaust is wasted energy that turbo could have used to make more boost. Even those runners wrapping and hot side isolation is not only there to keep your hands, cables and hoses from burning but also to keep the thermal energy in the gasses so more of the energy hits the hot side turbine. After it it sounded logical to me. Less energy wasted on heating the atmosphere more is used to make more work. That was the way I understood that phenomenon.

[@davidwelsh829]

distance from intake adds that much more volume to pressurize, out and in, just like an air compressor tank, could be part of the issue, ie it will just take longer to build boost

[@mlturboguy]

I don't work with V8 turbo applications, I am in the 4 cylinder (2.5 Liter) Porsche turbo car market, road racing applications. The turbo shop told you what is wrong, he nailed it. The hot housing is too large for this application. The old style Garrett T4 turbo's I work with on occasion have a .50A/R, .68A/R, .86A/R, they have a 9 something and one even over 1.0A/R. I only used the T4 housing design when we are building a 3.0L to 3.3L 4 cyl. Even the smallest .50A/R is too large for a 2.5L engine. The smaller the A/R ratio, the quicker it will make boost. The exhaust velocity is lost inside the larger size turbine housing, changing feed pipe size won't be enough. We tried one of the larger AR housings on a 2.5L build early on and we saw the same thing you are experiencing here, it wouldn't make boost until the RPM got way up there, totally impractical for road racing applications. Just install the tighter hot housings the turbo shop recommended on the existing turbo's reconfigure the exhaust flanges and its done. The system will work, just not with those huge A/R housings.

[@chevy502dk]

Nice video as always i Got a g-body 540 with hairdryers in the back 76 precisions not much lack so it’s wired you have the boost issue, I did once have a issue with missing boost turn out to be a boost leak with a inlet pipe since they are in the back you have more piping 🤠

[@Hjfvvdst]

That's a big money change and huge amount of rework and work.

[@kennethhecht3354]

Put the turbos up high and to the back of the motor on the firewall and hinge the hood forward.let the turbos stick out the sides of the hood.

[@danielbargas3377]

For turbo cars exhaust back pressure gauges are a must

[@jamielombardo5292]

My idea is start using a smaller turbo and see if you get better results. A lot of energy is lost in the distance from cylinder head.

[@timothymilam732]

But if pipe size is not correct on either end of this issue, and the static loss through all the components including bends and right angle turns intercooler restrictions all combined then your just throwing parts at it without the data to determine if that is the answer or not. Sorry but that's the science end of this apparent air flow problem. Something on the exhaust side of the issue too, plus is it wrapped to contain the heat energy needed as well. Plus if he's using even air to air cooling for intake air the heat gain at that distance is another factor in the overall performance of the engine equation.

[@rickwallace6270]

Smaller won’t get the power they are after. And if they could achieve the power goal with smaller turbos there is no future proofing it for higher horsepower.

[@bigdog2024]

the input side housing of the turbo is too big, to fix it the exhaust would need more volume and with enough pressure to spin the turbo to 20+ lbs boost and that’s not possible. A smaller exhaust to get the higher pressure is more back pressure on the motor meaning less HP. But pressure alone won’t fix it. Higher RPM would increase exhaust output but to get that volume is probably above the RPMs the engine is built to take and even if you get there you cannot add more. It’s all gotta work as a system. Turbo isn’t easy and bigger is harder. Steve figured all this in his head in about a millisecond and said, it’s just not going to work.

[@KD0LRG]

This is the ultimate of you have to have the money and time to be able to play at this level. This build is so cool, hate that it doesn't work with the turbos in the back. I know he wants mid 2000 hp but could you change the housing and just give it a spray for that extra 400 to 600 hp's. But at the end if the day it isn't mine and i respect whatever the owner wants to do. 🍺

[@whyamihereg]

It all works itself out. Awesome Truck Keith, worth the wait for sure!!

[@iansprojects3081]

It makes me sad I loved the way the turbos in the back looked

[@MattyEngland]

Sunday treat 👍Cheers Steve

[@timothythompson3029]

Probably the volume of the pipes. The turbos have to fill that volume up first before it can build boost. Try smaller pipes first.

[@scotthatch4548]

I do not know the specifics of the engine but one option would be to open the exhaust valve sooner to drive up exhaust pressure

[@Hydrazine1000]

What Clay Millican once explained while he was dropping by at PFI speed was that venting out the hood can seriously mess up the aerodynamics of a car. Venting out the side is a much better option in terms of how effective any rear spoilers are. Then again, this type of vintage truck body shape scoffs at modern aerodynamics anyway, so the point might be moot...

[@jamesbeard3983]

The energy that the turbos use to generate boost is mostly in the high temperature of the exhaust. Check out the Ideal Gas Law, the full form of Boyle's Law (same thing, PV=NRT, or pressure times volume equals a constant times temperature in Kelvin or Rankine -- degrees from absolute zero). By putting the turbos in the back, you allow the exhaust to cool and expand before the turbos get it.

[@db7069]

This!

[@bigmuz_pilot]

How long does the exhaust have to cool down? 1/10 of a second at 6k rpm? It barely cools, I think you're wrong. A mate has a boot mounted turbo on a 2jz and it works fine, takes a small amount longer to build initial boost as it has to compress all the exhaust gas in the long pipe but once it makes boost it is identical to a front mount.

[@jamesbeard3983]

@@bigmuz_pilot Check the temperature of the turbo exhaust inlet.

[@stevenkirk2563]

My twin turbo ls1 rear mount 68 mm turbos spools nicely.

[@bcbloc02]

I would just put two to .80ar housings on those turbos and try that first. I bet it would turn them fine then. Don’t think the small housings will choke the power because they are not having to handle near as much exhaust energy as they would if they were close.

[@johndcramblit3045]

I remember watching FANTOM WORKS on the Motor Trend channel & in 1 episode they installed the lt4 that had just come out in a 70 chevelle. It was supposed to be making 650hp but after installing it & driving it the engine wouldn't even spin the tires. They messed with it a lot & couldn't figure out why it was missing a few hundred hp? Then they called GM & found out that their air intake was too small & was choking off the motor. They installed a bigger cold air intake & all of a sudden that motor had all 650hp! Maybe you should try a larger tube size on the air intake or change the diameter of tubes feeding the turbos?

[@kcav5374]

Steve, I wish I'd have known you years ago when I first started machining blocks for high performance and racing. But now I'm 69, retired and just plain OLD! 🙂

[@tabbott429]

Seems like a lot of waste and inefficiency putting turbos so far back. This explains a lot about the velocity of air needed at a given distance. Thanks for sharing.

[@chriss8206]

Steve I have a question regarding exhaust .I was watching something about the NHRA and the amount of Down force that the exhaust pipes exert on the car .and I was wondering why dont people run their exhaust pointing straight back to get essentially a little extra boost for a few thousands of Second faster.

[@parsonsenergy]

Lol you hit the nail on the head. I’m a jet/reaction engine advocate. What you posted is pure Newtonian!! At some point I’m building my own reaction engine with no moving parts which I intend to mount in the bed of my Camino… I’m hoping to develop around 1200 pounds of boost which would be an impressive kick in the ass.. Good observation.. a secondary consideration for directing the exhaust perpendicular to the line of vehicle movement is that the vehicle is self tracking keeping it on the track..

[@parsonsenergy]

I meant thrust not boost.. tanks

[@timothymilam732]

I've often wondered that exact thing, because the top fuel folks aimed the exhaust backwards sometime back. As you mentioned they picked up several thousands in time due to this simple change. Where as they originally were using the exhaust for down pressure, they found the increase in speed was a larger gain than the minor difference in downforce. I believe the problem they're having here is the collectors are too large, and in the loss if heat energy due to the probably not insulated with heat wrap. Not knowing everything they have in place it's hard to be precise about whatever else there maybe happening or not happening. Then there's all the bends and turns made in the piping, and those greatly effect the velocity that the exhaust has by the time it travels that distance, and the same is true about the charge leaving the compressor housings after going back through the intercoolers to the throttle body could be significant among of restrictions all combined together to restrict the performance that much if all the different pieces are checked with a manometer at each individual fitting or component to verify exactly how much static pressure loss total which will inturn give you your cfm back to throttle body for the combustion to fed the turbos to begin with. Dam that's a long way around, but that's about only way I know how to say everything involved to determine the answer to the problem.

[@stevemorrisracing]

Yes you can But down force is needed too

[@Sharkey_t]

a number of years back nhra did a couple races of dragster vs funny car. a few of the funny car guys started screwing with the angles of the headers to point them right at the cockpit of the dragsters at the starting line. while it did throw off the dragster drivers the cars were loose on the top end. this started teams experimenting with header tube angle, to the point teams had a trailer full of headers and were using them to tune for track conditions. nhra eventually came up with a mandated header angle putting a stop to this.

[@kwaka140]

Smaller housings is a bandaid. The pipes from engine to turbos need to be really well insulated to retain heat and therefore gas volume. Even small temp changes make a huge difference. Check with a friendly engineer to confirm the science. To confirm heat loss you only need an EGT at the engine and another at the turbo inlet

[@tauraspasmonnom8325]

I'm curious. How much heat does the exhaust gas lose on the way from the engine to the turbos ? With that much flow an pressure is it still able to be laminar ?

[@ckane510]

Interesting as I've seen a number of builds on trucks where the turbo's are in the back.

[@3400Modified]

Looks like you got a new social media guy! So far it looks like he's a good addition to your team. :)

[@cjespers]

Thanks for the video, just needs a little Dewey. Re-engineering? I think we have all been there, lol.

[@chrispalfreyman8434]

What size is the tubing to the turbos? We’ve done a number of rear mount setups without spool issues, one of which being a 102mm GTX55, 1.50 A/R and 460ci, turbo mounted in the back of a ute and makes 10-15lb within 3-4 seconds on the brake. We did play with pre turbo exhaust tubing size and found smaller is better, aka twin 3” for big ci.

[@tchiwam]

Check pressure and temp(EGT) near the block then pressure temperature near the Turbos (T5) , if the pipes cool down the exhaust too much, you loose the main power source of a turbo.

[@williamdundon9770]

How about due to some compact mounting, was there some clamps missing on the exhaust piping?

[@jessemorrow3512]

Could the not spooling be from the volume exceeds the speed, with a 6 inch pipe, could you create a increase in speed by reducing the exhaust before the turbo (similar to Venturi effect)?

[@timothyschardt6672]

Could you spool it with like nitrous or CO2 directly onto the impeller blades?

[@ssnerd583]

I have used nitrous to spool a big turbo on a small motor.....you squeeze until about 7-8psi and then its all good but that is going into the MOTOR.....its kinda hard to tune, but....can be done....but you cant spray directly on the impeller like that as far as I know.....

[@alanphillips4431]

What about mounting them transversely up closer to the firewall then you can add naca ducts on each side of the hood to feed them. There’s enough sidewall on that hood to make it work without ruining the hoods lines.

[@scottsinfl]

Yea I was wondering about if I put a bigger intercooler in the back of my beast 42 chevy truck with the cummins if it would cause a boost loss from all the volume in the pipes to the rear. I figured it would have some lag time but wonder if I would drop in boost. Still if I could get egt's down I could stay in it longer and the lag wouldnt matter as much. When I hit 20 lb's the egt climbs fast and I cant stay in it to long maybe 10 sec. but at 28-30 I hit 1300F in about 5 sec so Ive got to add another cooler somewhere.

[@tomstrum6259]

Maybe super Insulate the Headers to Turbo with Smaller ID tubing to Keep Velocity up ??

[@michaelkennedy2528]

Hot side gasket on the turbo flange missing allow them to leak right at the turbo?

[@stevemuller82muller65]

Great work fellas 😁 can't wait to see this truck after you fellas get it sorted out 😎🤙🇺🇲

[@stevemorrisracing]

Keith too!

[@samuie2]

What about using an exaust bypass valve to block one turbo and force all exaust to a singel turbo to start spooling. Once it starts to build it should produce enough exaust to spool both and you can open the valve to the second turbo. Kind of like the sequential turbo setups of 90s supra and subaru.

[@joetate8563]

I have dealt with this exact issue many many times in the diesel world. Everyone thinks bigger is more power, but the turbine housing will dictate drive pressure. Sometimes, when someone couldn't wait for the correct size housing, we could play with the timing map, and retard the timing a bunch on the bottom to build some heat and get the turbine moving then rpm would take over on the top. Seen this too many times to count. Especially with sled pullers.

[@BrothersBuilds]

Love this channel! Thanks for cranking out content (no pun intended)!

[@donbrutcher4501]

Strange as it may seem, most of the exhaust energy driving the turbos is temperature drop arcross the turbine, rather exhaust pressure. Have you tried insulating the exhaust system from the engine to the turbos to reduce heat loss?

[@hghhvcggvcf9500]

How much is it to do with turbo system air volume? Feels like we're asking a lot more from the turbos after making more air volume to pressurize.

[@NorthernHDrider]

Be able to strap on smaller turbos & step up to the 80mm turbos?

[@merylpelosi8485]

Did you recalibrate the Spavine bearings in the Turbo-Encabulator? Maybe the Tremmie pipes have become disconnected from the Sprague uncoupler again. Make sure someone didn't leave a rag stuffed in the turbine inlet(s).

[@mattmanyam]

Possible dingle-arm pronation?

[@longroth4882]

Always questioned whether the rear mounts were worth it. That's a lot of pipe to drive a turbo, and get the boost back to the engine efficiently. Always figured it would be a slow build of boost, like waiting for an air compressor tank to fill to get the volume needed... 🤔

[@rodneyhillhouse7956]

Wouldn't a restrictor scoop into the up-pipe force the flow and still open up enough on the big end to still have adequate overall flow?

[@parsonsenergy]

I’ve been recommending augmented approach to eliminate trying to spool up before launch.. The idea needs someone like you and your shop to work out the nuances. I’d like to come visit you this summer before I croak..lol

[@HERETIC529]

I’d be curious if you could do a pressure test on the tubes to the back to make sure there isn’t a leak you didn’t know about

[@someyoungguy6990]

Smoke test will show all sins.

[@tthatcher854]

Just A thought if you get the turbos too far away. They are dependent on heat also air compresses and maybe the efficiencies just Won't be efficient! Would be cool to experiment on the Engine dino. To putting turbos farther away and see what happens!!!

[@Oliver-rb1tf]

I agree to all statements to put those "small" turbos as closely to the engine as possible. But how about to use only one turbo in the lower RPMs. Spool this one to get much more air into the system and when the first turbo is on his best efficiency, get the second one to assist him to reach maximum power.

[@jgregorykline3457]

Would smaller diameter exhaust tubes from front to the back turbos help? Cool truck no matter what route you take!

[@glenbrannon7224]

I'm thinking the exhaust side of the turbo is to big, not letting them spool up.

[@jeffreylong1841]

I concur.. Need smaller turbine housings..

[@mbliss01]

I would bet that fixes the boost under launch conditions, but limits the top end horsepower potential. There may be a middle compromise that works. But it might take a few experiments. And still be a compromise.

[@peterfusco2596]

What is spinning the turbos being they are away from the motor?

[@BopthoR]

Hey Steve may sound weird what if you run 2 smaller turbos up stream to create a jet effect?

[@ssnerd583]

sequential turbos....been done many times before

[@RUFFLEDPAPA]

all the elbows and bends in piping from front to back then return create all kinds of friction loss.not enough velocity to maintain flow?

[@chayzlett1988]

Would choking the exhaust up to the turbos help?

[@dannybrown5680]

Looks like lots of elbows in the run to the turbos. That causes pressure drop as well. He will need something else to move the air. You could try smaller exhaust diameter to increase speed but that will obviously choke the system at higher rpm’s

[@MrAPCProductions]

Wait, am I understanding this correctly that a 632 doesn't start spooling the turbos until 7k? and they are only 76 or 80s? Holdeners big bang motors are 76s, so a 4.8 hits full boost by 5k with a set of twin 76s. How is it possible that a 632 wont spool? Something else, intake, intercooler, couplings? something has to be leaking.