JDL Header & Exhaust System Development

[nelsmar]

Baseline was TRD intake, FA20 street tune.

The only changes were JDL overpipe, front pipe, UEL headers. The tune was revised on the dyno. We also did some blended high octane fuel as well (we had too much fuel in the car for a pure 100 octane test).

Thanks to Joe @GoodSpeedracing for lending us the dyno and Toni @FA20Club.com for helpin us with the tuning.

After this I may need to bum one of these headers to see what it does on my vortech kit =x I am extremely impressed!

[nelsmar]

Crud i was really tired and plotted the dyno backwards. Ill re-plot it on Saturday when I head back tot he shop... the info at the bottom was for the baseline.

The actual numbers (light line):
Corrected WHP: 183.3
WTQ: 138.5

This was on 91 octane Arizona/California fuel. On 96 octane blended we were seeing low 190's WHP.

edit: I updated my previous post with an overlayed dyno. The final numbers were just barely higher (listed above in this post). This should suffice.

[tennisfreak]

EDIT:

So you picked up 34 additional HP with the headers, front and over pipe?

Damn

[Freeman]

Sound clip please sir/miss!

sent from my locker... help!

[nelsmar]

Originally Posted by tennisfreak

EDIT:

So you picked up 34 additional HP with the headers, front and over pipe?

Damn

Just woke up... sick as hell. I now realize that i didn't plot the highest HP baseline. He made a few HP more than that. It was the same curve just a few HP more. The difference we saw was only 28WHP (sae). Sorry if i ruined everyones hopes and dreams... we ONLY made 28WHP... lol

Originally Posted by Freeman

Sound clip please sir/miss!

sent from my locker... help!

I'll work one out once i dont feel like death!

[industrial]

Originally Posted by Sellout

Scavenging is ALWAYS helpful. Under boost or not.

That said, if you remove backpressure with any supercharger, you lose boost, generally. Gotta remember that boost is simply a function of restriction (backpressure). Less backpressure results in less boost, but likely the same power, which then goes up if you bring the boost back up (duh)

I think you're confused. The engine which is connected to the ground provides the load (what you are calling backpressure). The backpressure I'm talking about is between the tailpipe and engine exhaust port. With a positive displacement supercharger...you are always in boost or positive pressure... Why do you need to pull air into the combustion chamber through scavenging when you have pressurized air constantly being crammed in there?

[Sellout]

Originally Posted by industrial

I think you're confused. The engine which is connected to the ground provides the load (what you are calling backpressure). The backpressure I'm talking about is between the tailpipe and engine exhaust port. With a positive displacement supercharger...you are always in boost or positive pressure... Why do you need to pull air into the combustion chamber through scavenging when you have pressurized air constantly being crammed in there?

For the same reason that a proper header will absolutely always result in more horsepower on the top end than a log manifold in a turbo application.

Both are pressurized, air will flow through both. One flows easier, using less engine horsepower for pumping, allowing more of the horsepower to make it to the ground.

That and I've actually seen it time and time again on vehicles with PD superchargers. Owner adds headers, boost goes down.

[industrial]

Originally Posted by Sellout

For the same reason that a proper header will absolutely always result in more horsepower on the top end than a log manifold in a turbo application.

Both are pressurized, air will flow through both. One flows easier, using less engine horsepower for pumping, allowing more of the horsepower to make it to the ground.

That and I've actually seen it time and time again on vehicles with PD superchargers. Owner adds headers, boost goes down.

Do the cars lose power when headers are added to a PD setup or does boost just go down (i.e. everything working better)? If you add a smaller pulley to a supercharger to get the boost to the same level it was with an exhaust restriction (backpressure), do you gain power? There is no need for backpressure for scavenging reasons on a PD system. You really can't convince me otherwise.

Headers make a MASSIVE difference on turbos. duh... Not talking about turbos here my friend, just PD superchargers.

[Sellout]

Originally Posted by industrial

Do the cars lose power when headers are added to a PD setup or does boost just go down (i.e. everything working better)? If you add a smaller pulley to a supercharger to get the boost to the same level it was with an exhaust restriction (backpressure), do you gain power? There is no need for backpressure for scavenging reasons on a PD system. You really can't convince me otherwise.

Headers make a MASSIVE difference on turbos. duh... Not talking about turbos here my friend, just PD superchargers.

Now you're taking us in two different directions. I never implied that backpressure was necessary. I said that removal of backpressure will reduce boost with a supercharger. You really don't have to look too hard to find evidence of this. I can't believe we're even still talking about it.

I said scavenging works, even under pressure. Headers working massively well with turbos is evidence of this. Pressure over atmospheric does not negate manifold tuning, whether it's an intake manifold or an exhaust manifold. The same principles apply, whether we're talking about turbos, PD superchargers, centrifugals, or naturally aspirated motors.

[JETRED]

First drive after install - K&N drop in filter, Raceseng Revo S2 Pulley kit, JDL UEL header with stock OP, MP and exhaust. Enjoy.
[ame]http://youtu.be/JdvvflP4dFU[/ame]

[industrial]

Originally Posted by Sellout

Now you're taking us in two different directions. I never implied that backpressure was necessary. I said that removal of backpressure will reduce boost with a supercharger. You really don't have to look too hard to find evidence of this. I can't believe we're even still talking about it.

I said scavenging works, even under pressure. Headers working massively well with turbos is evidence of this. Pressure over atmospheric does not negate manifold tuning, whether it's an intake manifold or an exhaust manifold. The same principles apply, whether we're talking about turbos, PD superchargers, centrifugals, or naturally aspirated motors.

I agree that removal of backpressure will reduce boost with a supercharger...and it will still be making more power and doing so with a happier motor. The way you say it sounds like you're saying the car will make less power and it's misleading.

Unless you can prove to me that scavenging works with a positive displacement supercharger (drawing exhaust gases from the combustion chamber...when you have a constant positive pressure on the intake side...), you aren't going to convince me that the backpressure you induce on a system to create a scavenging effect will be beneficial to this type of system.

Turbos and superchargers are very different when it comes to exhaust designs. I can't believe you are comparing the two. Are you completely missing the fact that turbos are driven by the exhaust where as supercharger aren't? You need to think about exhaust pulses and velocity on the hot side of the turbo which complicates the system. Think about the exhaust side of the turbo, what do you want there? The least restrictive system possible. It's no different with a supercharger except you want the least restrictive system possible from the exhaust ports on.

Might just have to agree to disagree since none of these things are easily proven. Except that gases do not expand when cooled, they cool when they expand. There is a difference buddy, that much is just basic chemistry.

[Freeman]

Originally Posted by JETRED

First drive after install - K&N drop in filter, Raceseng Revo S2 Pulley kit, JDL UEL header with stock OP, MP and exhaust. Enjoy.

Thank you! Sounds great!

sent from my locker... help!

[Sellout]

Originally Posted by industrial

I agree that removal of backpressure will reduce boost with a supercharger...and it will still be making more power and doing so with a happier motor. The way you say it sounds like you're saying the car will make less power and it's misleading.

Only if you take what I said at more than face value.

Unless you can prove to me that scavenging works with a positive displacement supercharger (drawing exhaust gases from the combustion chamber...when you have a constant positive pressure on the intake side...), you aren't going to convince me that the backpressure you induce on a system to create a scavenging effect will be beneficial to this type of system.

What does introducing backpressure have to do with scavenging? Scavenging is all about tuning the headers. The inside of your headers will always be under some positive pressure relative to atmospheric if the engine is running. You want that positive pressure to be as low as possible but there will always be some, even if it's only a few mm/hg. You tune the length of your header primaries such that the exhaust valves open while there is a low pressure zone right behind them and voila. Scavenging. The engine does not need to waste power pumping the exhaust gases out, and the power at the wheels goes up.

Turbos and superchargers are very different when it comes to exhaust designs. I can't believe you are comparing the two. Are you completely missing the fact that turbos are driven by the exhaust where as supercharger aren't?

Wow. Seriously?

You need to think about exhaust pulses and velocity on the hot side of the turbo which complicates the system.

You need to think about this stuff with ANY internal combustion engine if you're trying to make power. This is very basic engine tuning stuff here, and it works on all internal combustion engines.

Think about the exhaust side of the turbo, what do you want there? The least restrictive system possible. It's no different with a supercharger except you want the least restrictive system possible from the exhaust ports on.

You need to do some reading. Or build some cars. Or something. There is a whole lot more to exhaust system design in supercharger applications than "give me the least restriction I can get". Just like you can lose power in an NA application that way, you can lose power that way with a supercharger. This is easily proven, and has been. All you have to do is spend some time reading instead of arguing a point that you apparently don't understand. There is a LOT if information on exhaust system design out there if you do some simple searching.

There are two reasons that you want the widest, shortest pipe you can fit with a turbo setup:

-After the turbine wheel, there is no possibility of tuning exhaust pulses. The pulse waves are basically destroyed by the turbine wheel. All you want is to get the gases out of the way.

-You improve the efficiency of the turbine wheel with as little backpressure as possible.

Neither of those points apply with a supercharger, and there are no other reasons why you would want absolutely zero thought about pulse tuning.

Think about this: Why do top fuel dragsters have header pipes? Why aren't those header pipes wider? Shorter? They use positive displacement superchargers...

Except that gases do not expand when cooled, they cool when they expand. There is a difference buddy, that much is just basic chemistry.

Where did I say gases expand when cooled?

[industrial]

Originally Posted by Sellout

Only if you take what I said at more than face value.



What does introducing backpressure have to do with scavenging? Scavenging is all about tuning the headers. The inside of your headers will always be under some positive pressure relative to atmospheric if the engine is running. You want that positive pressure to be as low as possible but there will always be some, even if it's only a few mm/hg. You tune the length of your header primaries such that the exhaust valves open while there is a low pressure zone right behind them and voila. Scavenging. The engine does not need to waste power pumping the exhaust gases out, and the power at the wheels goes up.



Wow. Seriously?



You need to think about this stuff with ANY internal combustion engine if you're trying to make power. This is very basic engine tuning stuff here, and it works on all internal combustion engines.



You need to do some reading. Or build some cars. Or something. There is a whole lot more to exhaust system design in supercharger applications than "give me the least restriction I can get". Just like you can lose power in an NA application that way, you can lose power that way with a supercharger. This is easily proven, and has been. All you have to do is spend some time reading instead of arguing a point that you apparently don't understand. There is a LOT if information on exhaust system design out there if you do some simple searching.

There are two reasons that you want the widest, shortest pipe you can fit with a turbo setup:

-After the turbine wheel, there is no possibility of tuning exhaust pulses. The pulse waves are basically destroyed by the turbine wheel. All you want is to get the gases out of the way.

-You improve the efficiency of the turbine wheel with as little backpressure as possible.

Neither of those points apply with a supercharger, and there are no other reasons why you would want absolutely zero thought about pulse tuning.

Think about this: Why do top fuel dragsters have header pipes? Why aren't those header pipes wider? Shorter? They use positive displacement superchargers...



Where did I say gases expand when cooled?

I'm having a similar conversation in two threads. Getting some of what's said confused.

Top fuel dragsters have exhaust pipes because it would be counter-productive on many levels to have the exhaust evacuate into the engine bay. I seriously doubt it has to do with scavenging. It's as short and as wide as necessary.

Scavenging is important on a NA car for low end torque. It's a compromise because any backpressure is detrimental to the top end. It's all a compromise because anytime you design an exhaust for proper scavenging effects, you induce backpressure.

I'm done debating this with you. Taking this topic too far off topic and nobody is going to be convinced regardless of the science.