Turbo: Headers vs Log
11-21-2006, 04:13 PM
#1
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Turbo: Headers vs Log Is there a performace advantage when using headers, comparied to a "log" type design, in a turbo set up? The way I want to set up my system has very limited space. Im going to try to build headers, but if I cant fit them, would it hurt to build a "log" style header? I see truck madifolds support up to 1000hp (1 5/8 into 2 1/2) My motor will be around 900 @ the crank. Headers would be 1 3/4 into 3. Any thoughts?? 
11-21-2006, 09:53 PM
#3
A properly designed log can make close to or same amount of power as tubular's. I have 3" log in my LT1 combo and built a similar tubular setup last year. From the best I can tell, they are making the same amount of power, or my log setup is slightly ahead. You do the math:
My car:
388 LTx
LT4 intake
AFR210's 2.08/1.60
224/236 cam
T-76GTS turbo
water/air intercooler
3" log header downpipe, full exhaust
146 mph in the quarter at full weight and 16 psi - depending on which formula you use, that equates to 910 - 1060 fwhp.
Other combo I built:
377 SBC
Victor Jr. intake
Ported GMPP Fastburns 2.02/1.625
230/230 cam
T-76GTS turbo
air/air intercooler
stepped tubular headers with merge collectors, 2.5" y-pipe, 3.5" downpipe, no exhaust
930 fwhp at 18 psi
Even though the other combo had various advantages (less cid to match T76 better, better intake manifold, better exhaust ports, better "turbo cam", supposedly better headers, better downpipe, no exhaust, and 2 more psi boost), it didn't make significantly different power numbers from the engine in my car.
Mike
My car:
388 LTx
LT4 intake
AFR210's 2.08/1.60
224/236 cam
T-76GTS turbo
water/air intercooler
3" log header downpipe, full exhaust
146 mph in the quarter at full weight and 16 psi - depending on which formula you use, that equates to 910 - 1060 fwhp.
Other combo I built:
377 SBC
Victor Jr. intake
Ported GMPP Fastburns 2.02/1.625
230/230 cam
T-76GTS turbo
air/air intercooler
stepped tubular headers with merge collectors, 2.5" y-pipe, 3.5" downpipe, no exhaust
930 fwhp at 18 psi
Even though the other combo had various advantages (less cid to match T76 better, better intake manifold, better exhaust ports, better "turbo cam", supposedly better headers, better downpipe, no exhaust, and 2 more psi boost), it didn't make significantly different power numbers from the engine in my car.
Mike
11-22-2006, 07:23 AM
#4
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Originally Posted by nitrorocket
Log 
Why do you have limited space?? Build the passenger side first, it will make you feel better.
Why do you have limited space?? Build the passenger side first, it will make you feel better.
Im going to try to build the tubular headers first. But was wondering if I couldnt fit them, If I could go with a Log, and not effect the power or performance of the engine
Last edited by TT402LS1; 11-22-2006 at 07:29 AM.
11-22-2006, 11:31 AM
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im no exspert by any means, i just started researching for my turbo project. so take this with a grain of salt...
but from what i've gathered is the turbo create a crap load of back pressure in the exhaust manfold something like twice as much as the amount of boost its generating. so to an exstent having a really good flowing header/manfold doesnt help much. its going to have the back pressure anyway.
but from what i've gathered is the turbo create a crap load of back pressure in the exhaust manfold something like twice as much as the amount of boost its generating. so to an exstent having a really good flowing header/manfold doesnt help much. its going to have the back pressure anyway.
11-22-2006, 03:54 PM
#7
Originally Posted by blkchevyz
im no exspert by any means, i just started researching for my turbo project. so take this with a grain of salt...
but from what i've gathered is the turbo create a crap load of back pressure in the exhaust manfold something like twice as much as the amount of boost its generating. so to an exstent having a really good flowing header/manfold doesnt help much. its going to have the back pressure anyway.
but from what i've gathered is the turbo create a crap load of back pressure in the exhaust manfold something like twice as much as the amount of boost its generating. so to an exstent having a really good flowing header/manfold doesnt help much. its going to have the back pressure anyway.
Thats what i was going to say. Having tubular headers that are all free flowing and then have it all neck down to get through the small hole in the turbo is restrictive...theoretically, if your thinking it flows like an N/A engine. Actually the larger volume of exhaust/header you have the longer spool up time will be.
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11-22-2006, 04:47 PM
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The main fault on the log headers is they are much more prone to cracking. They will and can make insane power, pretty colse to a tubular header. A 6.0 manifold is not prone to the cracking problems that a fabbed log header is. If you made them from 1/8" tube you would probably be o.k..
11-22-2006, 05:19 PM
#11
Originally Posted by nitrorocket
The main fault on the log headers is they are much more prone to cracking.
a) can be accomplished by adding bellows expansion joints inbetween cylinders like the stock turbo GN header:
http://www.gnttype.org/techarea/pict...stockhdrs.html
b) can be accomplished by keeping each cylinder's flange separate. Use a solid copper gasket and the log can grow axially, slide the flange across the gasket, and never crack. This is how mine is and it actually works quite well.
Mike
Last edited by engineermike; 11-23-2006 at 12:12 AM.
11-22-2006, 11:03 PM
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That would work, however, This car has plenty of room to build a true header and in that case will be easier then making an effective log. If he had no other option, I would say go for it, but he's got the room. Here are some pics of the header he needs.
11-23-2006, 05:30 PM
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This is how my turbos are gonna be mounted..
The turbos are flush with the front of the motor. Its a little tighter than how you have yours set up.
The turbos are flush with the front of the motor. Its a little tighter than how you have yours set up.
11-24-2006, 09:40 AM
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Originally Posted by engineermike
Also consider that, since the exhaust will be at 30 - 50 psi, then it is 2 - 3 times more dense than normal, meaning you need 1/2 to 1/3 the flow capability for any given hp level.
11-24-2006, 12:50 PM
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I was just curious but doesn't turbine wheel trim, like clipped or not, and the a/r of the housing, on center or tangential, frame size , all of these have an affect to the flow. Just curious as to at what point you would need a tubular header? i have tubular headers on both mustangs. But was just curious as to at what point a tubular header would pull ahead? Thanks
11-24-2006, 03:28 PM
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I would think a tubular header would have an advantage when not in boost. They should make good power similar to a regualar header. I would also think they would make more power again at the real high boost range due to the increased efficiency the headers have because of continous smooth bends and merge.
The only way to ever know is to see a back to back dyno with nothing else changed. I think there was one done on a honda a while back that might support this theory.
The only way to ever know is to see a back to back dyno with nothing else changed. I think there was one done on a honda a while back that might support this theory.
11-25-2006, 11:39 AM
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Well... my tubing hasnt came yet from FI, so I guess I dont know which one Im building for sure.I have to fly back to Orlando tomarrow, so it will have to wait till X-mas.
Im going to try to build the full lenght headers first. (this is the way Id like to go) I think there is just enough room for them, but it will be very tight. Because I am coming up into the turbos from the bottom, the headers have to fit between the streeing shaft and engine block. I will also need very tight 180* bends. Whats the tightest bend you can buy?
Thanks - Ron
Im going to try to build the full lenght headers first. (this is the way Id like to go) I think there is just enough room for them, but it will be very tight. Because I am coming up into the turbos from the bottom, the headers have to fit between the streeing shaft and engine block. I will also need very tight 180* bends. Whats the tightest bend you can buy?
Thanks - Ron
11-25-2006, 06:31 PM
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With the rear tube, just use a 6" radius bend and you should be o.k. That is what I used and it cleared. You can see in the pics how I made it clear the steering shaft.
