How important is equal length??
How important is equal length?? In the process of building a turbo kit for my 240. There is not room for it to be mounted in the center so I'm planning on mounting it on one side or the other. How important is it that my runners from each side are equal length? The simplest route would make one side about 12" off the manifold on one side and bringing the other side all the way across to the turbo. I do think it may be possible to add length to the turbo side by routing it down then back up to the collector? Looking for real experience or proven knowledge. In my mind it probably won't matter but I want it to be the best possible.
My set up is a 4.8l 9.1:1 cr, stock 243s, 04z06 cam, pt76gts.
Thanks in advance
My set up is a 4.8l 9.1:1 cr, stock 243s, 04z06 cam, pt76gts.
Thanks in advance
care to comment on spoolup differences as well as power band differences. I would assume equal length would spool slightly slower and reach a lower peak number sooner where an equal length setup might spool slightly slower but give more power in the high rpms and hold it longer.
Hard to find anyone using a 4.8l, i have kinda been looking at what the cobra guys are doing.
Hard to find anyone using a 4.8l, i have kinda been looking at what the cobra guys are doing.
try to run factory cast exh manifolds flipped forward. If the 3 bolt collector flange interferes with something cut it off and weld on a Vband. Plenty of cars on here are running 8's with some form of factory manifold. No need to fabricate ones unless you have to.
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keep the crossover short as possible and with a 4.8.....2 inch crossover would be best to help with velocity. Im building a e46 bmw with a 370 and im using a 2 1/4 crossover. here is some great info on yb....and Phil is the man when it comes to this kinda **** heres the link http://www.yellowbullet.com/forum/sh...d.php?t=308464
Definately looking into a smaller crossover pipe. This won't be the only motor this turbo kit will be on but I doubt I'll ever go bigger than a 347ci. Probably try the 4.8 and if I like it alot do a set of custom rods and the 3.780 wisecos and be done. If I don't like it I'll probably go to a forged iron 347. I might Do 2.5" and a conical reducer closer to the turbo down to a 2". Then it would be easy to change later.On page 10 of that thread btw.
Equal length headers are considered more important on smaller engines. Like a 4 cylinder or smaller 6 cylinder. These engines need more help spooling turbos.
Your exhaust leaves the head in pulses. If you have equal length headers/manifolds, then each exhaust pulse out of each runner will hit the turbine wheel on its own, instead of being crammed together with another pulse.
While it may sound like cramming exhaust pulses together is a good thing, like it would make one bigger pulse... Yes it will make a bigger pulse, but you just added turbulence into the mix as well. The two smaller pulses would have more total energy than the one bigger pulse. Keeping all your pulses in line aids in spool and flow, thus an increase in power as well. This is why smaller engines can benefit more using equal length. An 8 cylinder engine has 8 pulses heading toward that turbo. It doesn't need a whole lot of help with equal pulsing. However, having equal length most certainly can still benefit a V8.
A well designed equal length header/manifold setup should perform better in all areas over a regular manifold
Your exhaust leaves the head in pulses. If you have equal length headers/manifolds, then each exhaust pulse out of each runner will hit the turbine wheel on its own, instead of being crammed together with another pulse.
While it may sound like cramming exhaust pulses together is a good thing, like it would make one bigger pulse... Yes it will make a bigger pulse, but you just added turbulence into the mix as well. The two smaller pulses would have more total energy than the one bigger pulse. Keeping all your pulses in line aids in spool and flow, thus an increase in power as well. This is why smaller engines can benefit more using equal length. An 8 cylinder engine has 8 pulses heading toward that turbo. It doesn't need a whole lot of help with equal pulsing. However, having equal length most certainly can still benefit a V8.
A well designed equal length header/manifold setup should perform better in all areas over a regular manifold
Staging Lane
Joined: Jul 2006
Posts: 53
Likes: 0
From: F22 Secret Lair (aka) The "Austin Millbarge"
Having an obstruction, in this case a turbo, negates the benefits of running equal length headers. At this point you're dealing with thermodynamics as opposed to exhaust tuning for scavenging, torque, etc.
So ideally, you want high exhaust gas pressure with little heat transfer through the headers/crossover pipes, and little to no obstructions after the turbo to maintain low pressure (high pressure always seeks low pressure). This why HP increases on turbo cars are so great when getting rid of cats and installing larger downpipes and exhaust tubing.
A better alternative to figuring out equal lengths is to group exhaust pulses by running 4-2 headers into a divided turbine housing.
So ideally, you want high exhaust gas pressure with little heat transfer through the headers/crossover pipes, and little to no obstructions after the turbo to maintain low pressure (high pressure always seeks low pressure). This why HP increases on turbo cars are so great when getting rid of cats and installing larger downpipes and exhaust tubing.
A better alternative to figuring out equal lengths is to group exhaust pulses by running 4-2 headers into a divided turbine housing.
So ideally, you want high exhaust gas pressure with little heat transfer through the headers/crossover pipes, and little to no obstructions after the turbo to maintain low pressure (high pressure always seeks low pressure). This why HP increases on turbo cars are so great when getting rid of cats and installing larger downpipes and exhaust tubing.
Again, all of the info I have given is from an engineer in this field who knows quite well what he is doing. Corky Bell, Maximum Boost. Read it, learn it, then give out your information.
Corky Bell is god. Maximum Boost is the bible, and anything else is wrong. /Sarcasm.
Good read, lots of great information. But thats one of the great things about this sport....there is more than one way to skin a cat.
Good read, lots of great information. But thats one of the great things about this sport....there is more than one way to skin a cat.
If more people read Maximum boost, then less people would be on here handing out their incorrect opinions coupled with their zero experience.
The great thing about big *** turbo charged V8's, is that it is easy to make big power and run fast times, which makes lots of people LOOK like they know what they are talking about. When in fact, just like any internet car forum... very few really know what they are talking about.
JAX04,
The twin scroll would benefit the most on an equal length manifold setup, with one bank running into one scroll, and the other bank running into the other scroll.
Second place would be non equal length, but still keeping both banks separate all the way to the turbine wheel.
Third place is simply to merge everything together before it reaches the twin scroll housing. At this point, it makes zero difference if you are running twin scroll or an open housing. Actually that is wrong... In this case, an open scroll would be better, because you are not running exhaust flow right into that divided section of the turbine housing causing exhaust gas reversion.
Staging Lane
Joined: Jul 2006
Posts: 53
Likes: 0
From: F22 Secret Lair (aka) The "Austin Millbarge"
As far as Maximum Boost, yes great book. Unfortunately wasn't around when I first started playing with boost. Hell, neither were car forums, or google, or yahoo. Tribal knowledge..
So with all do respect to the OP and his question about the importance of equal length headers in a turbo application, my opinion; sure in a perfect world under perfect conditions and tons of space to play with, go for it. The time and money spent to design a set of these headers, that would actually perform well, would far outweigh their practicality unless the OP has a sponsor, or maybe even a cool "sugah mama". Especially, with all the technology built into turbochargers these days, who really cares whether your headers are equal length or not.
Again, you're playing with theory here and not providing any clear direction. To simply tell someone to haphazardly split the banks up, would leave someone pretty frustrated if they were looking for any measurable gain in spool up. It's not just about splitting banks, it's about dividing and grouping exhaust pulses that would otherwise interfere with one another in a completely merged collector.
First of all sir, you have no clue as to what my experience is. So for this arguments sake let's just say I have a very strong, and knowledgeable, background in thermodynamic power and propulsion. So if you really wanna kick around theories in gas flow & thermo-mechanical energy, pulses or what ever, I'd be more than obliged in another more appropriate thread.
As far as Maximum Boost, yes great book. Unfortunately wasn't around when I first started playing with boost. Hell, neither were car forums, or google, or yahoo. Tribal knowledge..
So with all do respect to the OP and his question about the importance of equal length headers in a turbo application, my opinion; sure in a perfect world under perfect conditions and tons of space to play with, go for it. The time and money spent to design a set of these headers, that would actually perform well, would far outweigh their practicality unless the OP has a sponsor, or maybe even a cool "sugah mama". Especially, with all the technology built into turbochargers these days, who really cares whether your headers are equal length or not.
Again, you're playing with theory here and not providing any clear direction. To simply tell someone to haphazardly split the banks up, would leave someone pretty frustrated if they were looking for any measurable gain in spool up. It's not just about splitting banks, it's about dividing and grouping exhaust pulses that would otherwise interfere with one another in a completely merged collector.
As far as Maximum Boost, yes great book. Unfortunately wasn't around when I first started playing with boost. Hell, neither were car forums, or google, or yahoo. Tribal knowledge..
So with all do respect to the OP and his question about the importance of equal length headers in a turbo application, my opinion; sure in a perfect world under perfect conditions and tons of space to play with, go for it. The time and money spent to design a set of these headers, that would actually perform well, would far outweigh their practicality unless the OP has a sponsor, or maybe even a cool "sugah mama". Especially, with all the technology built into turbochargers these days, who really cares whether your headers are equal length or not.
Again, you're playing with theory here and not providing any clear direction. To simply tell someone to haphazardly split the banks up, would leave someone pretty frustrated if they were looking for any measurable gain in spool up. It's not just about splitting banks, it's about dividing and grouping exhaust pulses that would otherwise interfere with one another in a completely merged collector.
Ok, so you have now 100% disagreed with your original post. That works for me too I guess? Whatever...
