4-2-1 headers for turbo.
4-2-1 headers for turbo. Ok, I have no idea where to put this thread, mods please move to FI if appropriate.
Just came across a decent lump sum of money and decided its time to turbo the GTO. Can't say I'm entirely happy with anyting currently on the market in the way of kits for the car so I want to build my own headers and stuff.
So, on to the point. I've been pondering on the firing order of an LS1 with header design in mind. I'm going to be using "twin scroll" split inlet turbine housings, why not use 4-2 headers to take advantage of splitting the exhaust pulses on each bank and have the final 2-1 merge the turbo itself. From my experiance the secondary lengths are much more important on 4-2-1 headers than the primarys are, how would a turbo effect this? Could I just measure down the centerline of the turbine housing until it meets the wheel and add that to the secondary length?
Have found with past experiance in turboed imports that this can make a 3-400 rpm difference in spool time without having as high of a pressure ratio on the turbine. Would pair cyls 1/5, 3/7, 2/4, 6/8 if anyone was interested.
Just came across a decent lump sum of money and decided its time to turbo the GTO. Can't say I'm entirely happy with anyting currently on the market in the way of kits for the car so I want to build my own headers and stuff.
So, on to the point. I've been pondering on the firing order of an LS1 with header design in mind. I'm going to be using "twin scroll" split inlet turbine housings, why not use 4-2 headers to take advantage of splitting the exhaust pulses on each bank and have the final 2-1 merge the turbo itself. From my experiance the secondary lengths are much more important on 4-2-1 headers than the primarys are, how would a turbo effect this? Could I just measure down the centerline of the turbine housing until it meets the wheel and add that to the secondary length?
Have found with past experiance in turboed imports that this can make a 3-400 rpm difference in spool time without having as high of a pressure ratio on the turbine. Would pair cyls 1/5, 3/7, 2/4, 6/8 if anyone was interested.
Drew,
This is probably the most appropriate forum for this topic and the way you've structured you post is proper for this forum. Actually, I've seen very little discussion of the relative advantages of tri-y (aka 4-2-1) headers here in the years that I've been active on the forum and this is a good time for that discussion. I run them myself because I'm more interested in broad-band torque rather than peak HP (or torque for that matter).
Steve
This is probably the most appropriate forum for this topic and the way you've structured you post is proper for this forum. Actually, I've seen very little discussion of the relative advantages of tri-y (aka 4-2-1) headers here in the years that I've been active on the forum and this is a good time for that discussion. I run them myself because I'm more interested in broad-band torque rather than peak HP (or torque for that matter).
Steve
I searched for a few hours and couldn't find any discussion on tri-y's with turbo setups. I'm not really looking for ultimate power. 650 on 93 octane with no meth and I would ****. I would like it to drive pretty close to stock, don't mind if I loose 30-40 ft/lbs in the bottom end, my previous cars were gutless (out of boost) turbo nissans. Would like to make decent power and have great driveability. Don't care if it makes a bazillion hp, biggest tire I can fit without tubbing is a 275. Like I stated earlier, I've seen properly divided manifolds make more of a difference in spool time than going from the largest to smallest a/r will, with much better flow.
On The Tree
Joined: Mar 2006
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From: N.C.
Rusted40,
Your link makes mention of a four into two into a turbo, but it doesn't quantify anything. Maybe I'm missing something. I'd like to see some test data and some theory for both normally aspirated and forced induction engines.
Steve
Your link makes mention of a four into two into a turbo, but it doesn't quantify anything. Maybe I'm missing something. I'd like to see some test data and some theory for both normally aspirated and forced induction engines.
Steve
I know there is a program called Pipemax that you can download for some $ that is rather impressive. I've only seen some screen shots and what it can do, but it looks really cool. It goes into detail on a lot of things you are talking about.
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TECH Addict
Joined: Aug 2004
Posts: 2,866
Likes: 4
twin scroll turbo are starting to become popular in the Evo comunities. they do work better than traditional housings as they make better use of the pluses in the exhaust gasses.
are you thinking of a single or twin turbo setup?? i know a guy on the corrvettforum.com (BTF) did a single on his C4 that had a crossover style exhaust like the ford GT guys used to run. think it worked well for him.
thanks
Chris.
are you thinking of a single or twin turbo setup?? i know a guy on the corrvettforum.com (BTF) did a single on his C4 that had a crossover style exhaust like the ford GT guys used to run. think it worked well for him.
thanks
Chris.
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Verdad Gallardo I've heard of pipemax before, I really need to quit being lazy and just paypal Larry for it. Would like to go twin turbo, packaging seems better than a single on GTO's. Crossover headers + twin turbos would be bad *** but I don't really need another 20 some odd feet of tubing under the hood as space is already at a premium. I already know how well some of the twin scroll turbos have proven themselves in the import world, just though it was odd that no one was using them on LS1's to split up the two exhaust pulses per bank in succession. I think I should just buy all the crap and see how it works, if it turns out awful then I'm only out a few $$$ in materials for headers, everything else I could reuse.
TECH Addict
Joined: Aug 2004
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I've heard of pipemax before, I really need to quit being lazy and just paypal Larry for it. Would like to go twin turbo, packaging seems better than a single on GTO's. Crossover headers + twin turbos would be bad *** but I don't really need another 20 some odd feet of tubing under the hood as space is already at a premium. I already know how well some of the twin scroll turbos have proven themselves in the import world, just though it was odd that no one was using them on LS1's to split up the two exhaust pulses per bank in succession. I think I should just buy all the crap and see how it works, if it turns out awful then I'm only out a few $$$ in materials for headers, everything else I could reuse.
Chris.
I searched for a few hours and couldn't find any discussion on tri-y's with turbo setups. I'm not really looking for ultimate power. 650 on 93 octane with no meth and I would ****. I would like it to drive pretty close to stock, don't mind if I loose 30-40 ft/lbs in the bottom end, my previous cars were gutless (out of boost) turbo nissans. Would like to make decent power and have great driveability. Don't care if it makes a bazillion hp, biggest tire I can fit without tubbing is a 275. Like I stated earlier, I've seen properly divided manifolds make more of a difference in spool time than going from the largest to smallest a/r will, with much better flow.
On The Tree
Joined: Feb 2005
Posts: 178
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From: Odessa, TX
From a n/a stand point if you need more low end torque without high end loss than the tri-y is the way to go. On a 316 ci motor we saw an increase of 25 hp and 15 ft lbs at 8000 rpm and no loss at 10000. So in my opinion if it worked on that motor I would try it on a turbo motor.
From a n/a stand point if you need more low end torque without high end loss than the tri-y is the way to go. On a 316 ci motor we saw an increase of 25 hp and 15 ft lbs at 8000 rpm and no loss at 10000. So in my opinion if it worked on that motor I would try it on a turbo motor.
Steve, any chance of getting you to measure your header primary and secondary diameters and lengths?
Last edited by Drew04GTO; Jan 28, 2008 at 02:45 AM.
Drew,
I will be glad to measure, however I will be out of town for the next week. I'll keep following this thread. Perhaps someone else could do the measuring. Also, call Randy at Thorley and ask him if he has the dimensions on their 310Y headers. Also, take a look at some of my pictures here http://rides.webshots.com/photo/1106...48361291DWkvUo.
Steve
I will be glad to measure, however I will be out of town for the next week. I'll keep following this thread. Perhaps someone else could do the measuring. Also, call Randy at Thorley and ask him if he has the dimensions on their 310Y headers. Also, take a look at some of my pictures here http://rides.webshots.com/photo/1106...48361291DWkvUo.
Steve
Teching In
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In my honest opinion, it is not worth it on 8 cylinders...the pulses are already "tight"...it will be especially difficult for it to go thru the turbine the way it should be...smooth and sequenced.
It works perfectly well for a 4 cyl and even 6. I am currently using this setup for my 3800series3.
It works perfectly well for a 4 cyl and even 6. I am currently using this setup for my 3800series3.
nocutt please explain. I would actually think the firing order of all twin plane v8's SUCKS. Really with there was a readily available single plane v8 that didn't come from Italy. But the way it sits right now there's one event on each bank where 2 cylinders fire right after each other "loading up" the collector with both pulses. If I can pair the header tubes I can have each one of those pulses do something to the turbine wheel instead of it just being one big lump of a pulse. And that's still happening at 25hz or something around 3000 rpm anyways, pretty common event in the exhaust, might as well take advantage of it. I'm really trying to treat this motor as a pair of 4 cyls, probably not the best of ideas but space concerns have me wanting to go twin turbo instead of single.
Teching In
Joined: Feb 2005
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If it is something you want to try for your own edification; then I will say carry on 
...but for the sole purpose of reducing lag or boost threshold is not worth the headache. At least in my opinion...Yes you are right, on the ls1 I believe two cylinders do overlap, but to harness the grouping like you have proposed to arrange them would seem you still loose the even firing the turbine 'needs'. Other than taking the pulse from one bank across to the other I don't see a cost effective way to space the events in sequence. The pulses MUST reach the turbine wheel EVENLY, so the theory is the cylinders should fire from bank to bank...this is optimal. The 4 cyl can get away with it because they are spaced 'more loosely', plus the cylinders that overlap can be paired more conveniently. (it would seem less complicated with four pulses). On a six cylinder, the cylinders are paired in 3's + the fact that each bank fires 240 degrees apart, neither 'too tight nor too loose' (the pulses).
...but for the sole purpose of reducing lag or boost threshold is not worth the headache. At least in my opinion...Yes you are right, on the ls1 I believe two cylinders do overlap, but to harness the grouping like you have proposed to arrange them would seem you still loose the even firing the turbine 'needs'. Other than taking the pulse from one bank across to the other I don't see a cost effective way to space the events in sequence. The pulses MUST reach the turbine wheel EVENLY, so the theory is the cylinders should fire from bank to bank...this is optimal. The 4 cyl can get away with it because they are spaced 'more loosely', plus the cylinders that overlap can be paired more conveniently. (it would seem less complicated with four pulses). On a six cylinder, the cylinders are paired in 3's + the fact that each bank fires 240 degrees apart, neither 'too tight nor too loose' (the pulses). Awsome, this is the exact info I was looking for. So really the only way this would work correctly would be to have crossover/180degree headers also. I'm actually really not horribly concerned with boost threshold, atleast not as much as many of the people I've seen on here, it just turns out that the turbos I want only come in twin scroll and I thought I might as well take advantage of it. I will probably do it anyways for ***** and giggles since total header cost (both sides, including flanges) is in the neighborhood of $500.
Last edited by Drew04GTO; Jan 30, 2008 at 12:50 AM.
Teching In
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I think the fact that lag is reduced when employing pulse turbocharging has more to do with backpressure and possibility of reversion been reduced; to also add, turbine efficiency is potentially increased...reduced lag seems to just be a by-product. Notwithstanding it will be a nice experiment, hopefully you choose a more suiting turbine wheel and housing 
