HEADER TECH AND MODIFICATIONS FOR STREET OR ALL OUT RACING!

AN INSIGHT INTO A HEADER TYPES AND WHAT THEY OFFER. OTHER ALTERNATIVES TO GET ADDITIONAL POWER TO MAKE YOUR STREET RIDE OR RACECAR BETTER!
COVER PICTURE IS OF AN ENGINE PRODUCING 2400 RWHP FROM 20 YEARS AGO.
I get numerous requests for technical advice and if interested, tex me @ 626 203 2712. Half hour to 1 hour+ rates are available. Most calls go over as posted and it is ok. US Pacific time zone.

[@rebekahfrench5747]

Always the small things that make the most noticeable results once they add up things go better.. Old school tech is never lost its just converted into todays high tech world.. 👍

[@daledavies2334]

A big advantage of the tri-y or 4-2-1 headers is the pair of cylinders that fire 90° apart have the exhaust split to prevent reversion into the first cylinder to fire's exhaust, by the high pressure pulse from the second cylinder. That high pressure, high temperature exhaust dilutes the cool fresh air in the first cylinder, which reduces volumetric efficiency and the density of the charge in the cylinder as it heats a bit. It also adds to the tendency to detonate in those two cylinders. With a cross plane crankshaft the tri-y header splits the exhaust pulses so they are 270° apart. By the time the now second cylinder dumps its exhaust down to the first Y, the high pressure can not turn and return into the first cylinder as the valve is closed. Mazda as part of their Shyactiv research found this on log manifolds. The second cylinder pushed hot exhaust back into the almost closed exhaust valve of the preceeding cylinder. This caused the fresh air/fuel charge to be about 60° warmer at BDC. At a point a couple of crankshaft degrees before ignition, the charge in the cylinder was 160° warmer. The length of 4 into 1 header primaries takes this out of the set of factors. Generally though 4 into 1 headers on a 4 cylinder engine will lose a couple of lbft at low to mid RPM but be much stronger at sustained RPMs above 7000. On a street oriented engine the RPM band favors the tri-y headers.

[@benalamedaracing2765]

Thanks Dale for a more thorough explanation and appreciate it much sir!

[@terrysibley9636]

That was like a physics class. Well done. My 311, and is coming together. Pistons came in at 0.010 out of the whole. Thanks been.

[@deanmoser5907]

Thought I had a good understanding of how headers worked but I've learnt stuff about try y headers that I had no idea about. Thanks again Ben.

[@benalamedaracing2765]

Thank you sir.

[@kevinclancy.]

soaking this all up, wow what a cool idea clocking the exhaust pulses to match turbo rotation, and also the pinholes to relight the exhaust to help the process, awesome!

[@benalamedaracing2765]

Thanks!

[@scottosborne8735]

The point of headers is to induce scavenging. Timing of the vacuum pulses is tuned by the size and length of the header primary tube. Complex flow dynamics in play. Strong knowledge allows for tuning of this dynamic to best fit the application. 4-2-1 collectors and an X-pipe allow for the performance most similar to 180 tuned headers. Cross-plane crankshaft engines are difficult to tune exhaust. Exhaust is one of the most effective methods to tune power.

[@benalamedaracing2765]

Interestingly many years ago we had a supercharge 347 and actually made more power with a shorty hedder than a complete long tube! I will try to do this video explaining what actually happened. It should be an eye opener because at that time years ago we were scratching our heads! lol

[@terrysanborn684]

Ben what about rapping the header

[@hoost3056]

​@benalamedaracing2765 doesn't surprise me, the supercharged engine is forcing the burned mixture out reducing or eliminating the need of tricks to manipulate the exhaust gases. Zoomies and uncollected exhausts are all the rage now on door cars running Prochargers and huge nitrous ( Roots and screw blower guys have been doing it forever )

[@matthewtucker2806]

Awesome lesson Ben. I learn so much from your videos. Keep em coming buddy. Great info and explanations.

[@benalamedaracing2765]

Thanks!

[@terrywillis5784]

I have seen alot of headers. This information puts it all together now why some race teams are spending lots more money on their headers. Super information. Thank you !!!

[@benalamedaracing2765]

Thank you!

[@ptwccrider]

Great content adding the drag strip in your videos!!!! And Ofcourse your excellent info. Thanks for sharing!!!

[@benalamedaracing2765]

Thanks and I feel it gives the impression I am not a keyboard racer! lol Appreciate your viewing sir.

[@e85lenkkari]

Thanks Ben! Great free information from you and you explain everything so well that everybody understands! 👏

[@benalamedaracing2765]

Thank you sir!

[@bulldogbradford8081]

Great video!!!!!

[@johnkufeldt3564]

Thanks again Ben, your experience is fantastic. Cheers from Canada.

[@benalamedaracing2765]

Thanks!

[@mikecondoluci53]

thank you ben for another great one

[@bobcuomo5122]

Another great video Mr Alameda....I learn somehting with every video !!!

[@benalamedaracing2765]

Thanks!

[@robertheymann5906]

Another fantastic video! Thank you sir

[@benalamedaracing2765]

Thanks again!

[@flyingdebree3094]

Awesome content I learned a lot from this

[@benalamedaracing2765]

Thanks!

[@patrickmarcello5103]

Ben those N/A small blocks revving in the beginning never ever get old for me! I had to rewind it a few times! Thanks for the great information mate

[@benalamedaracing2765]

Best to learn NA and what works and does not before we move on to another phase. It gives us a better outlook on engine dynamics. Thanks Patrick!

[@ptwccrider]

Hello , do you still port the upper 4.6 plenum. My brother and myself both have crow pics. A 2000 and a 2005. And would definitely like to purchase 2 of them. Ive been looking for the plenum elbow video to share with my brother . But man.. I cant find it again!! Thanks you!

[@jlbsmyth9494]

Excellent video I appreciate your honesty! Some people have another definition these days of honesty

[@benalamedaracing2765]

Thanks for your support of my channel and please share the videos!

[@rickyfulks889]

Smokey Yunick drilled the holes like that to read his air fuel visually

[@wayneireland4802]

Thanks for posting that mr alameda.makes sense especially turbo exhaust and putting in firing order thankyou.peace

[@benalamedaracing2765]

The ultimate goal is to prevent excessive turbulence that will make the turbo less efficient perhaps decreasing turbo response and making lag worse than it should be. Thanks as well Wayne!

[@Jvcomet]

Great info as always 👍thanks for sharing

[@benalamedaracing2765]

Thanks for supporting my channel!

[@autonomous_collective]

Very interesting tips.

[@benalamedaracing2765]

Thanks and many of my videos dealt with years of track testing and competition. Dyno testing exclusively and flow bench tests leaves a lot off the table, I try to highlight many of these things and very few actually seriously compete & race and there is the difference. Thanks again!

[@patrickwendling6759]

Thank you for your knowledge and video's USA 🇺🇸

[@benalamedaracing2765]

Thanks for watching Patrick!

[@zAvAvAz]

Thank you Ben.

[@benalamedaracing2765]

Thanks Dennis!

[@boduke2522]

your awwsome ben im first nation from bc canada iv owned muscle cars since i was 16 you have great tips and tricks thankyou

[@benalamedaracing2765]

Thanks as well Bo!

[@TerrelThomas]

Excellent content Ben, I installed a set of Doug's Tri-Y headers on my 67' coupe (438 CI windsor) they're 1 3/4" stepped to 2" and the thing makes a bunch of torque and revs right to 7000 RPM's. thanks for sharing the information

[@benalamedaracing2765]

I bet you got lots of mid range torque and power!

[@TerrelThomas]

@@benalamedaracing2765 The funny thing is, I almost sent them back to where I order them from because they weren't full length headers (I was told they would kill top end power) I'm glad I saw your "Header tech" video because even with full exhaust (tailpipes and all) the car revs just fine....Thanks again!!!

[@mikeg4163]

Very good…also pulls the rust out of the steel tubing/headers and runs that grit through the bore, rings and piston walls. Huge reason to run stainless headers

[@benalamedaracing2765]

You are correct!

[@renadocasimiro]

Wow..Ben..Good To See you Watching From The Philippines..

[@benalamedaracing2765]

Salamat Renado and thanks for your support of my channel.

[@renadocasimiro]

@@benalamedaracing2765 Ben Just Want To Ask ..Are You My Classmate On SRS... BENJIE ALAMEDA.. i Remember We Use To Read The Manual of F 86 Super Sabre.. well Migth be a diffrent Person..

[@benalamedaracing2765]

@@renadocasimiro, wow yes that is me! haha. Are you on facebook with the SRS group? I am there with my wife Carmen Tantoco.

[@stelios672]

ben you are greate thanks for the knowlegde

[@benalamedaracing2765]

Thank you and race safe!

[@jimkillen1065]

A long time ago the crayon deal was told to me by a fellow who ran a g gas car . Speaking of exhaust I think he ran some reversion plates on the heads to the headers . Or that's what I think he called them . Thanks for videos

[@benalamedaracing2765]

Reversion hedders are sometimes employed by using a cone exit and or an oversize hedder primary pipe within a smaller exhaust port both perfect for the purpose. Others also done is moving up the hedders above the exhaust port roof creating a dam or a mismatched doing the same thing. Everything to make a little bit more! lol

[@last302]

Great video and it was cool to see you talk about equal length headers. Whats your opinion on midlength headers. Midlengths are my only option with a 351w and a automatic AODE in a sn95. Besides shorties. Thanks!!

[@benalamedaracing2765]

Mid length is better than shorties and I would pick that over them if it is available and have clearance issues.

[@arthurking6549]

Goilet is the name of the spear Shorty headers with a long tuned collector work exceptionally well. Supersonic flow cannot occur in an enclosed pipe ( Darin Morgan).

[@benalamedaracing2765]

Thank you and it will help @ high engine speeds and it becomes a convenient ramp for reversion gases to travel back to the exhaust valve much easier at lower engine speeds. Now on supersonic flow? Mach 1 or supersonic occurs when an object (aircraft/rocket) is travelling faster than the noise it is making. It then impacts the atmosphere which is stationary and creates a "sonic boom". On our subject here, we have no object travelling @ 685-750 mph(depending on the altitude/temp)., but we have a movement of exhaust gases which I referred to as almost or near sonic. This gases are not impacting atmosphere anywhere within the pipe but outside only, by that time it is not at mach speed but much slower. Sorry for the long winded explanation. Lol. I am an Aerospace graduate this is why beside's racing, my Dad was a fighter pilot and airplanes are my first love not racing.

[@creekjonsun]

I wish you would do a video on 180 degree exhaust ( like on a Ford GT 40 ) and its drawbacks and benefits ,

[@benalamedaracing2765]

It is a plus from all aspects except fitment and will only work with some spring car chassis or Indy type racecars where you can wrap the hedders around and above!

[@daveb1870]

I keep tellin people wrap your headers in foundry ceramic if you can afford it where its good to 2500. Dissipated energy is a net loss in any circumstance. Helps on na cars with more consistency, but its even more significant in turbo applications. Keep that heat in boys. High temp molecular adhesion style coatings keep the heat off the piston as well as the surface area of the combustion chamber. Keep that heat from soaking and youll gain more.

[@benalamedaracing2765]

You are right on point with your comments! Thanks.

[@EricBatterson-lw7bb]

Bottom line.. the old guys/racers have paved the way for race, and street tech that just works. All the best tricks I've got have come from the old timmers.

[@benalamedaracing2765]

Agree Eric and please share my channel/videos! No replacement for experience.

[@cam3002]

Great information, thanks so much for sharing. Your analysis is supported by the book "Scientific design of exhaust and intake systems" by Smith and Morrison. Quick question on the burnt paint on the header trick, if the header has heat coating, does it still apply? Assuming that the heat coating will lower the tube temperatures enough to give a false reading.

[@benalamedaracing2765]

Thanks for tuning in. I feel the coating will throw off the actual area it starts to cool down showing the transition to the cooler location of the hedder pipe.

[@autonomous_collective]

4-2-1 always if motor is 8000 rpm and below. More torque confirmed by numerous Dyno tests. See David Vizard YT.

[@benalamedaracing2765]

Yes sir they are superior specially if we used the NASCAR style long tube 4-2-1. They not only produce just as much power as a conventional hedder but bump up the mid range much more than the traditional layout. In fact in 1990 I did this first time and I had too much mid range and many thought I was running a big block until they look and it was a short and smaller SBF.

[@TomKunnas]

Hello. First of all sorry my bad english...I am from Finland. I just remembering Vizard's 8000 rpm rule conserning of 4 cyl. inline engines which are evenfire. I think situation with oddfire V8 may differ...

[@jamesmedina2062]

@@TomKunnasHi what is the 8000 RPM rule?

[@user-id9ft8qv4x]

Thanks for knowledge! Can you talk about R/S and RPM?

[@benalamedaracing2765]

What is R/S?

[@user-id9ft8qv4x]

@@benalamedaracing2765 relationship between rod length and crank length

[@gabrieldimarco9646]

Catching up on some of your older videos Ben. I remember reading about the pinhole idea from Smokey Yunick years ago. I haven't put them in my headers as I'm running FI and thought that it would run rich since it is introducing oxygen into the system. Would I need to recalibrate the fuel curve to compensate or should I just leave it as is?

[@benalamedaracing2765]

It depends mostly on how sensitive your exhaust is to these small openings and I would suggest silicone them shut first (copper silicone) then note your readings and open it up and see where the difference shows and take note of it.

[@tinoracing7]

Anytime you funnel in Reverse Heat accelerates the speed that's why it was more responsive it really works real good but then you need a better location for your wastegate

[@benalamedaracing2765]

Yes and everytime you jam it like it is a on a merge collector the velocity speeds up and this is good for the turbo(s).

[@tinoracing7]

@@benalamedaracing2765 finally I get to conversate with somebody that knows what they are talking about

[@benalamedaracing2765]

@@tinoracing7 Thanks!

[@tinoracing7]

@@benalamedaracing2765 how you doing Ben I got a question I need some help I'll pay for your service I'm trying to put an LS together prototype that I came up with I converted LS to sing over a cam I need some guidance regarding the new timing on the timing belt

[@2fwelding842]

How long do you drive a street car to get header tube length, if you.drive too long will it keep creeping further? In school on dyno with tri y. Teacher said add 1.5 inch extension before 2-1. Gained 12hp. Tuned tri ys are nuts

[@utahcountypicazospage5412]

So a cam with no overlap with exhaust bias would be ok with the straight shorty but overlap would be better with long tube camshaft is the heart ?

[@benalamedaracing2765]

We need some decent amount of overlap and best to consult your cam grinder like Isky and others. They would probably shoot you in the right set up without much hassle.

[@bobcuomo5122]

1st

[@samuelsprague3361]

do you know if a fox body has a low pressure area anywhere under the car where ending the exhaust pipe might benefit power at speed.

[@benalamedaracing2765]

On the first gen. stangs the low pressure area is under the floor in front of the rear seat and slightly behind @ the opening of the floor! It may be the same with other cars.

[@richdouche8253]

Do you drill the small hole in Tri-Y headers too, or would that be counter productive to the desired reversion?

[@benalamedaracing2765]

Anything to raise the hedder pipe temperatures should be a benefit to keep it scavenging all the way down. Same thing with heat wraps or coatings does the same things...

[@evanarthur7535]

Do you smell any exhaust fumes when you drill the pinholes in the headers? Also, what are your thoughts on reversion dams/cones?

[@benalamedaracing2765]

If it is drilled in the proper location it should not leak exhaust gases and that is why it is important to locate the hole in a low pressure area.

[@quick-performance-services]

@@benalamedaracing2765 so the low pressure would be just after the bend of the primary tube after the header mounting flange in a downward angle ? And when you say pin hole ? what size hole do you recommend for a 2 inch primary tube ( long tube kook's header with 3 1/2 dump ) for a 1.60 exhaust valve with a rpm range of 2900 to 7200 SBF 414 cubic inch 12:1 comp. N/A motor. if you need more info i can contact you? thanks for your time.

[@jrsgarage3244]

Dominator car best, 2,200lbs Hemi Power 💪💥🚀

[@benalamedaracing2765]

Well that should run with heads like that!

[@frederickhairston3823]

Good day will the pin hole in header work well for weekend driver as well.

[@benalamedaracing2765]

If your exhaust system is loud enough you will probably not even notice it! Everything is different as far as combination of your engine but I have done this with my street car and I cannot even tell if it is there or not...

[@scotthultin7769]

Well I was told by a professional doesn't matter how long the tubes are on any set of headers there's probably no more than one two at the right length for any cylinder and sometimes none

[@benalamedaracing2765]

Well it does matter because if it is too long because, the reverse flow will really be bad! You want the slowing down of the gases to be precisely or close to it to get together on the collector at that juncture. Then at this point they can balance off each other and help them propel by the following gases to atmosphere/muffler. In fact on high rpm engines too long will cost power upstairs and too short will lower power downstairs or at low rpms. Got to strike a balance this is why I recommend the painting of the hedders or some use crayons to "precisely" point to you where it drastically slows down when it looses heat energy= flow!

[@joe-hp4nk]

If you double the diameter of the primary and use that for your collector, the area of the collector will be the same as four primaries. Therefore there should be no back up regardless of the length of the primaries.

[@benalamedaracing2765]

"Regardless" of the length of the primary pipe? Ok that is news to me because I have lost power with too long a primary pipe length. Gained torque no doubt but paid for it somewhere someplace... Could you explain that a little bit more because I am confused. Thanks!

[@joe-hp4nk]

@@benalamedaracing2765 If you take the diameter of your primary and double it and use that for your collector, the area of he collector is equal to the four primaries going into it. So there is no back pressure at the collector. So the primary length shouldn't matter. That's my thinking for what it's worth.

[@benalamedaracing2765]

@@joe-hp4nk Have you run this concept on a high horsepower engine if primary length is inconsequential to power production? This is news to me and thanks for your insight.

[@joe-hp4nk]

@@benalamedaracing2765 I'm just a back yard hotroder and it's only a hobby. No, I haven't tested it, so it's only a theory. Weather runner length makes a difference, I do not know. I don't have the means nor the capital to put it to the test. Wish you well.

[@benalamedaracing2765]

@@joe-hp4nk, thanks as well and I like to see what others think and it is always a learning process because we all do not know everything for sure.

[@michaelfackler9716]

I guess whomever came up with the concept of header collectors back in the day, didn't take into consideration that all cylinders dont fire at one time and collector didn't need to be that large

[@benalamedaracing2765]

You have that correct sir! The merge collector indeed helps keep the velocity going and here the scenario of one hedder pipe transitioning to the collector, see's a big area increase and the corresponding slowing down of the exhaust gases! I said the same thing of others trying so hard to port equalize flow @ the intake manifold, failing to consider the firing sequences robbing of other cylinders specially adjacent firing which makes it worse!

[@CLEEPER1]

So 2" primary into a 3" collector better than a 3.5" collector? 750hp to 800 hp ls7

[@donbrutcher4501]

On the engine dyno using an air flow meter above the carb, does the flow meter sense different volumes with the different header configurations?

[@benalamedaracing2765]

If you have a sizable and measurable increase in power then the intake must have been passing or ingesting more air. Therefore the flow meter should be able to see that.

[@donbrutcher4501]

@@benalamedaracing2765 Probably yes, maybe no. Could the power increase be attributed to increased combustion efficiency? Less negative work?

[@benalamedaracing2765]

@@donbrutcher4501 you are also correct and increased efficiency can mean many things like good exhausting thru improve hedders will scavenge most of the spent gases, therefore the next combustion event will definitely improve so will the power. I totally missed your point about hedder design difference. In short strong exhaust flow speeds will also have a reflection to the intake tract during overlap and that will increase the intake manifold signal thru the ports as well and the flowmeter will indeed see that.

[@warrenglover]

I have 1996 c 5 corvette stock exhaust manifold. For 5.3 ls . They say corvette manifold worth 50 hp . Sound better than header??

[@benalamedaracing2765]

I have to see both of them to evaluate hard to just think about it but 50+ more is pretty good from here!

[@ronaldrey8474]

Do equal length headers cause harmonic problems ? Wish people knew that rust in steel headers will travel up in intake & rings. Stainless is a must. Kaase showed experiment simulated with motor oil inside header and shows oil travel up through engine to bottom of carb. plate. Total Seal podcast just aired with Jon explaining how bad mild steel headers destroy your engine.

[@benalamedaracing2765]

Yes a rusted hedder will indeed cost power and your statements I agree with big time!

[@jamesmedina2062]

I don't think it's that simple. I need to watch Kaase more but I think he is great. There are chrome plated headers, ceramic coated headers, and many lengths and types of headers. My headers were coated and they have lots of carbon on the inside of them. I do definitely have a personal distaste for rusty mild steel pipes or headers. What about connections in a system? Do they matter? And what about other particles besides rust? There are off road vehicles operating in dusty environments. Does dirt travel up as well? When you look at my tailpipe I only see carbon and water and undoubtedly air pushes things outward usually.

[@ronaldrey8474]

@@jamesmedina2062 excellent response t.y. the video ref was with Total Seal Lake Speed Jr. and Kaase. Podcast I mentioned stainless (and was wrong) any coated headers on inside or chromed inside gives same protection (not only stainless). I'm just a parrot and not my experiment. But man it sunk in after learning. And oil filters only filter a percentage not all. So dirt etc.. yeah problems with rings. I didn't understand connections unless u mean connection of exhaustion with mild steel ??

[@jamesmedina2062]

@@ronaldrey8474 I ask a lot of question! It used to be my job!(providing technical support) I am not going to know that much about coatings as I only used one, Jet Hot, on some headers and only know what I saw and what they told me. I saw some odd little corrosion on them years later but while in use they looked great and kept things cooler. The X-Pipe on the system got very badly corroded while the headers looked great for many years. So now I am only asking myself if there is corrosion and how and where it is. They are warrantied and not just for a year so I plan to send them back for a redo.

[@ronaldrey8474]

@@jamesmedina2062 hello my friend... I'll tell you my head fell of my shoulders when checking under hood temps after jet coated headers on big block ! OMGosh !!! That Podcast with Kaase... Jon said straight up rev even a cold engine up to 4K rpm to remove rust inside pipes. He said a quick rev @starting will prevent getting sucked in through pipes. And a qwk rev. won't hurt a thing. Not a frozen engine ya know but on what they call a cold start engine hit with 4k rpm blows it out. And your ring seal won't be affected that way with mild steel pipes. But again this was Kaase doing test in controlled environment so I'm a believer. hehehe I think this might answer and allow some time before changing them pipes by blowing it out on cold start 👍

[@voxnova9471]

How do you find where to step your headers?

[@benalamedaracing2765]

Everyone has their own formula so it is best you talk to a hedder builder because he would have a lot of feedback!

[@officeassistant1292]

How small the hole sure be under the header?

[@benalamedaracing2765]

I feel a 3/16 hole will be the best compromise and do this on the inside bend of the primary pipes closest to the flange exit.

[@SuperTambo69]

how big do you drill that little hole?

[@benalamedaracing2765]

3/16 hole.

[@peterolson8350]

But the turbine is 90 degrees to how the exhaust gases hit the turbine wheel, so how does it matter how the pipes sit in the collector?

[@jakeeyeington92189]

It doesn't matter how it hits the turbo but the speed it hits the turbo does.

[@benalamedaracing2765]

Yes it is if you are running a single turbo! How about a twin turbo/side? Now you have direct flow to it or close to with minor bends if any with the pipe. Same thing can be said about a single dominator on a sheetmetal intake, which the corner end cylinders are not a straight but curve path! Twin dominators specially split types will position the venturi's all 8 of them on top or in front of all 8 intake ports, twin carbs like twin turbos. All collectors @ high speeds are subjected to pressures which is part of the flow condition because without it flow will rapidly slow down, it is important we contain and keep the heat going and with it the pressures creating downstream flow. Therefore, swirling or rotating the flow within the confines of the collector will be efficient at keeping the gases moving and expelled straight to the turbine housing regardless if it is curve, straight or with a slight angle. The object here is not to lose the heat content of the gases and the speed of the gases itself... Both gains are possible compared to just dumping the gases whichever way it comes in creating turbulence and flow separation because of said condition.

[@benalamedaracing2765]

@@jakeeyeington92189, absolutely but if the exhaust pulses are turbulent exiting the collectors, what do you think it would do to the turbo's efficiency? Here turbulence will slow the velocity of the exhaust gases. If there is anyway we can smooth this out the better!

[@peterolson8350]

@@benalamedaracing2765 The exhaust gases always enter radially (90 degrees) into the turbine wheel. Unless it is a turbo with an axial turbine, but they are hardly in any car.

[@benalamedaracing2765]

Peter, sorry for the confusion and I hesitated to bring up this subject because not that long ago I worked with a Mercedes Endurance team's efforts on their turbo's working with guess what? Axial type with an innovative impeller and housing design. Looks promising but there were issues with legality as far as the design which ended up in courts and I had to bow down exit stage left! Now on the piping collector it is also a delicate issue as far as the exit angles of the collector creating turbulence and inefficiencies specially as you pointed at the entrance angles of 90* (correctly stated) and how we tried speeding this area velocity's creating shock waves on the turbine's tips on the intake side! From interesting designs of exhaust sequencing and pipe wall's texture/discharge angles while "dumping raw fuel" on the exhaust sides and lighting it up, creating exhaust pulses to decrease any perceivable turbo lag is quiet interesting but mostly on the close lips research.