Truck manifolds? Really?
08-01-2012, 07:05 PM
#1
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Truck manifolds? Really? I read on one of these threads that some guy said use truck exhaust manifolds on a remote/rear mount turbo upgrade. Is this for heat retention alone? On the basis, a better flowing engine makes more power on the same amount of boost than a stock engine, what is the benefit? Could ceramic coating and header wrap not provide the same efficiency? Please explain this to me.
08-01-2012, 07:11 PM
#2
I was under the impression they were used due to availability and power capabilities. People still make massive power with stock manifolds that often come with junkyard motors. Had nothing to do with heat retention, more to do with reducing cost/fabbing
08-01-2012, 07:28 PM
#3
most use truck manifolds on a front mount turbo. rear mount turbos would use the stock f-body manifolds.
Yes you want the engine to flow better, but not at the cost of exhaust velocity. Velocity is the speed of the air. The more speed the better your turbo will spool.
you wouldnt want long tube headers for a turbo system beacuse while they do flow a lot of air, you lose that very important velocity. Also, the cast iron retains a lot of the heat. Hot air has more volume, more volume = more air to spin the turbo. (which is the reason front mount turbos are better, closer to the manifold for more heat.)
The factory manifolds still flow well, are very strong, hold heat, and are very cheap. You could go to a custom fabricated tubular turbo manifold, and yes it would make a little more power, but it would be astronomically more expensive compared to a $40 set of truck manifolds.
Im pushing 1020rwhp on 17psi through truck manifolds, and there are a lot of people with a lot more HP.
hopefuly that makes sense. That was as simplified as i could figure out how to explain it
Yes you want the engine to flow better, but not at the cost of exhaust velocity. Velocity is the speed of the air. The more speed the better your turbo will spool.
you wouldnt want long tube headers for a turbo system beacuse while they do flow a lot of air, you lose that very important velocity. Also, the cast iron retains a lot of the heat. Hot air has more volume, more volume = more air to spin the turbo. (which is the reason front mount turbos are better, closer to the manifold for more heat.)
The factory manifolds still flow well, are very strong, hold heat, and are very cheap. You could go to a custom fabricated tubular turbo manifold, and yes it would make a little more power, but it would be astronomically more expensive compared to a $40 set of truck manifolds.
Im pushing 1020rwhp on 17psi through truck manifolds, and there are a lot of people with a lot more HP.
hopefuly that makes sense. That was as simplified as i could figure out how to explain it
08-01-2012, 07:30 PM
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Truck manifolds are more for front mount guys. Rear mounts usually use whatever the stock manifolds on the car are. It has EVERYTHING to do with heat retention. Surface area on your exhaust from motor to turbo is the enemy. Heat helps turbos spool. Long tubes are the worst thing you can do for a rear mount. To quote Zombie:
Chapter 3... Use the Force!
Eventually end users started to listen to the cries of partially correct dissenters who claimed a turbo runs off of heat (they run off of heat and pressure). They started to insulate their exhaust piping and swap headers for stock manifolds, anything to keep the heat in the exhaust stream. Surface area is the enemy. The more surface area on your exhaust system, the faster it gets rid of the heat. Headers are the worst mod on a rear mounted turbo setup. They have a very large surface area compared with exhaust manifolds. That large surface area is also at the point where the exhaust is it's hottest, the point where you want to keep the most heat possible.
Exhaust heat causes the volume of the gas to be larger. That larger volume of gas in a confined area equals more pressure. More pressure equals faster spool. Pressure is both friend and foe though. As much as pressure can help you, it can hurt you. Too much pressure and things start to choke up.
Hot exhaust gas has much more energy and pressure than cool exhaust gas. Without a waste gate before the turbo to bleed off some of this exhaust, the turbo would spool to its maximum. The waste gate lets us regulate how much of the exhaust is actually making it to the turbo and regulate the amount of boost produced by the compressor side. The goal is to supply the turbo with just enough exhaust energy to spool up as quickly as possible to the set boost level and then bypass the rest of the exhaust gas. The best way to bypass extra exhaust gas is a larger exhaust housing or a larger exhaust wheel or both. The hotter your exhaust gas the less of it you need to spin the turbine wheel of the turbo. This means the hotter exhaust gas is more efficient at doing the work. Since you don't need all of it to do the work, you can bypass the extra. Bypassing this extra gas causes the backpressure to drop which allows the cylinders to fill easier. If you don't bypass this extra exhaust gas your engine tends to choke at higher boost levels and RPMs due to excessive exhaust back pressure. It becomes more difficult for the engine to ingest more air when it can't get all of the spent exhaust out of the combustion chamber because it's fighting the exhaust back pressure. Controlling this backpressure and maintaining decent spool can become a delicate balancing act. Bypass too much and your setup spools slow and might not be able to make as much boost as you desire. Bypass too little and you run into excessive back pressure and possibly over running the flow of you waste gate causing you boost creep, poor power and increases your chance of detonating.
Eventually end users started to listen to the cries of partially correct dissenters who claimed a turbo runs off of heat (they run off of heat and pressure). They started to insulate their exhaust piping and swap headers for stock manifolds, anything to keep the heat in the exhaust stream. Surface area is the enemy. The more surface area on your exhaust system, the faster it gets rid of the heat. Headers are the worst mod on a rear mounted turbo setup. They have a very large surface area compared with exhaust manifolds. That large surface area is also at the point where the exhaust is it's hottest, the point where you want to keep the most heat possible.
Exhaust heat causes the volume of the gas to be larger. That larger volume of gas in a confined area equals more pressure. More pressure equals faster spool. Pressure is both friend and foe though. As much as pressure can help you, it can hurt you. Too much pressure and things start to choke up.
Hot exhaust gas has much more energy and pressure than cool exhaust gas. Without a waste gate before the turbo to bleed off some of this exhaust, the turbo would spool to its maximum. The waste gate lets us regulate how much of the exhaust is actually making it to the turbo and regulate the amount of boost produced by the compressor side. The goal is to supply the turbo with just enough exhaust energy to spool up as quickly as possible to the set boost level and then bypass the rest of the exhaust gas. The best way to bypass extra exhaust gas is a larger exhaust housing or a larger exhaust wheel or both. The hotter your exhaust gas the less of it you need to spin the turbine wheel of the turbo. This means the hotter exhaust gas is more efficient at doing the work. Since you don't need all of it to do the work, you can bypass the extra. Bypassing this extra gas causes the backpressure to drop which allows the cylinders to fill easier. If you don't bypass this extra exhaust gas your engine tends to choke at higher boost levels and RPMs due to excessive exhaust back pressure. It becomes more difficult for the engine to ingest more air when it can't get all of the spent exhaust out of the combustion chamber because it's fighting the exhaust back pressure. Controlling this backpressure and maintaining decent spool can become a delicate balancing act. Bypass too much and your setup spools slow and might not be able to make as much boost as you desire. Bypass too little and you run into excessive back pressure and possibly over running the flow of you waste gate causing you boost creep, poor power and increases your chance of detonating.
Last edited by Adam86; 08-01-2012 at 09:51 PM.
08-01-2012, 09:38 PM
#7
the flange points straight down on those... i would assume it would interfere with the motor mounts, but have never tried it.
do a search on here, there are a few different options (5th gen camaro, c6, etc) if you want to keep A/C.
If youre looking for the additional flow from the LS7, you dont really need it.
do a search on here, there are a few different options (5th gen camaro, c6, etc) if you want to keep A/C.
If youre looking for the additional flow from the LS7, you dont really need it.
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08-02-2012, 12:18 PM
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08-02-2012, 12:48 PM
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Are we still talking about a rear mount or are you considering a front mount now?
08-02-2012, 01:30 PM
#18
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To put it simply
Heat:
The thin gauge steel used on longtube headers loses a ton of heat. Even when you wrap them they are still going to lose more heat than a set of cast iron manifolds
Exhaust velocity/flow:
The larger primarys of headers may flow more air but they kill the exhaust velocity. The more velocity you have the harder its going to hit the wheel. Its the same concept that guys use in the arguments about 2.25 vs 2.50 inch crossover pipes. The smaller pipes make just as much power and spool faster.
If you want to try and reinvent the wheel go right ahead. Its already been done before. People use manifolds because they are cheap as dirt and work. They've been 7's in the 1320.
08-03-2012, 12:21 AM
#19
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I'm saying if I wanna spend the little extra on Cast iron aftermarket manifolds that prob flow better I will, but if actual "headers" are gonna hurt the whole setup then i will stay away from them.
08-03-2012, 12:27 AM
#20
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And I'm planning the build for a '91 Camaro hardtop 5-speed car. It has plenty of room for HUGE intercooler up front, but I want to keep the A/C and not have to cut the fender apron to run the turbo piping like ive seen some people do. Plus I'm putting a 14-point cage in the car so under good clearance is valuable. Yes it will prob have some issues with keeping the A/C but I will cross that bridge when I come to it.