3800 Exhaust question/theory
- Thread starter Fish
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Brian, You're thoughts are spot on but they are a small part of a big picture.
The comparison really isn't apples to apples since one of the cars is naturally aspirated and the other is supercharged. The supercharged car might have lower compression but is moving an exponentially larger amount of air than the naturally aspirated motor (remember all we're dealing with here are 500lb air pumps).
Headers aren't horrible for a GT in my opinion but unlike a GTP you can't drop a pulley size to get your low end torque back. You've effectively shifted your powerband up (less torque/ more hp) and though the car may dyno more horsepower it's anyone's guess as to whether it's faster in the 1/4 mile or not.
All things being equal (both motors naturally aspirated or both motors supercharged) this is the case but since one of the motors is supercharged the argument really isn't valid... Keep reading.
The comparison really isn't apples to apples since one of the cars is naturally aspirated and the other is supercharged. The supercharged car might have lower compression but is moving an exponentially larger amount of air than the naturally aspirated motor (remember all we're dealing with here are 500lb air pumps).
Headers aren't horrible for a GT in my opinion but unlike a GTP you can't drop a pulley size to get your low end torque back. You've effectively shifted your powerband up (less torque/ more hp) and though the car may dyno more horsepower it's anyone's guess as to whether it's faster in the 1/4 mile or not.
I see your point, but everyone wants to talk velocity. Velocity velocity velocity.
Yes, the blower is pushing more air into the motor, but the valve is only open for so long. The same ammount of time that the valve is open on a GT in fact.
Even if the L67 gets more air blown in, there is no blower inside the engine to push it back out. Since lower compression means a smaller bang, that would mean slower gas comming out. Which would mean there isnt AS much back pressure. In theory.
I understand what you are saying Mike. But I want others and yourself to accept the fact. And the info provied would be perfect to use. It just hit me as I was accelerating past a GTP on the highway and I chuckled.
Plus if a header for a na Civic makes a difference, Im damn sure headers for L36s would make alot more.
Yes, the blower is pushing more air into the motor, but the valve is only open for so long. The same ammount of time that the valve is open on a GT in fact.
Even if the L67 gets more air blown in, there is no blower inside the engine to push it back out. Since lower compression means a smaller bang, that would mean slower gas comming out. Which would mean there isnt AS much back pressure. In theory.
I understand what you are saying Mike. But I want others and yourself to accept the fact. And the info provied would be perfect to use. It just hit me as I was accelerating past a GTP on the highway and I chuckled.
Plus if a header for a na Civic makes a difference, Im damn sure headers for L36s would make alot more.
Again though, this is an innacurate assumption. If the blower is putting a larger volume of air inside of the cylinder the cylinder will move a larger volume of air out the exhaust valve when it opens. The supercharger can not put more air into the motor than it will move.
An incorrect theory...
What fact is that? I'm not against headers on a GT though I think the S&S's are the largest anyone should go on them.
What is boost stacking then??
Still a theory. I didnt say there wouldnt be any. But I find it silly when alot of old timers tell me that backpressure is bad, but L36s depend on it.
I never said you. Im talking the whole community. It is shoved down everyones throats that anything bigger than S&S headers are bad for GTs that it scares everyone away. Yet everyone that goes against what they are saying proves them wrong.
Anthony Arosemena on clubgp ran 14.6 with no cam or rockers with TOG headers and the following mods...
MSP CAI
Hypertech 180 Thermostat
Taylor Spiro Pro 8mm
NGK TR6
TOG Headers
RT Hi-Flow Cat
SLP Loud Mouth 2.5
GMPP 4" exhaust tips
ZZP HVTB Stage 1
ZZP Water & Alt Pulley's
ZZP Motor Mounts
GMPP Handling Upgrade Kit + Rear STB.
DHP PCM v1.0
Timberwarp on clubgp ran 14.2 with basically the same mods and a GT1 cam.
FWIW.
Im not doubting Mikes knowledge of engines. However I dont know how well he knows the L36. Ive slept, ate, breathed, lived the L36 for 3 years.
Just like I wouldnt question him about tore asses. That was/is his life for longer then Ive done the L36.
It's a limitation of flow. There will always be a flow ceiling. There is no such thing as boost stacking. Boost in itself is just a way of measuring restriction.
It all depends on where you want the power and each person has to find their happy little medium. With the naturally aspirated L36 reducing backpressure will lower the amount of available low end torque while raising the amount of high rpm horsepower.
Brian, the L36/ L67 motors are one of the most basic types of motors you can get sans a Flathead V8. How long you've been involved with the car should not matter. You don't learn engines by osmosis.
I never came onto this forum to have a genital swinging contest over who knows more about what. I never claimed to be the god of 3800s and I'm not sure why there is such a want to discredit me, especially under the guise of having a "discussion" which you knew I would respond to.I think you might be keen on picking up a couple of basic engine books Brian. They might make things a lot clearer and will certainly be more articulate than my ramblings.
I
imported_Ron Vogel
Guest
I don't want to get in the middle of this, but the L67 actually has higher compression.
???
Think of it like this, static and dynamic.
Static being the mechanical compression based on the piston dish, CC volume.
Dynamic being cam profile, ignition advance, boost, or vaccuum.
Even with the L36's higher static compression, N/A motors typically see 40% less cylinder fill that a boosted motor at 100KPA.
So you will see a total compression of (dynamic and static) on an N/A L36 reach 10-11:1, but even a mildly boosted L67 can reach in excess of 18:1!
Put that in your pipe and smoke it!
However, headers are good for all cars. N/A cars will be the first to feel the effects of proper (or improper) tube length and ID.
???
Think of it like this, static and dynamic.
Static being the mechanical compression based on the piston dish, CC volume.
Dynamic being cam profile, ignition advance, boost, or vaccuum.
Even with the L36's higher static compression, N/A motors typically see 40% less cylinder fill that a boosted motor at 100KPA.
So you will see a total compression of (dynamic and static) on an N/A L36 reach 10-11:1, but even a mildly boosted L67 can reach in excess of 18:1!
Put that in your pipe and smoke it!
However, headers are good for all cars. N/A cars will be the first to feel the effects of proper (or improper) tube length and ID.
I know they are a basic engine. You know they are a basic engine. Yet for some reason we dont exactly take our cars to the local speed shop to get work done or ask advice now do we??
I dont want to embarass you with a genital swinging contest. And I was contemplating on posting on cgp to get Zooomer and everyone else involved also. But I figured Id keep this on a lower level to see what other people though. I should have know basically it would be you, maybe RV, and a few others. This was never to discredit you. It was funny to see how you say one thing about compression and exhaust speeds, yet it doesnt seem to matter with headers. I hate the way everyone is towards things they dont understand.
You tell me to get a book because I ask a question about exhaust gasses. Rob Archer tells me to get a book cause I question him about shifting at 5700 RPMs with a cam.
You both also blow me off about an IL/IN race day. You guys in bed together or something??
Few questions/comments;
From my knowledge, headers give the exhaust gases an easier/more efficient way of leaving the engine which in turn equals hp. Weather it be on a N/A or supercharged.
Question on a comment made by Mike...you will lose low end torque when adding headers. If headers are put on a GTP will the low end torque loss be as great as it would be on a GT? I mean headers are gonna make the car faster either way correct?
Also, would I be looking at higher top end power over stock manifolds without dropping a pully. So basically would there be an improvement in trap speeds in the 1/4 mile....right?
Im only asking because Im planning on getting headers for my GTP in the near future. I dont want to have to drop a pully size if i dont have to because of the low end torque loss metioned earlier. I basically dont want the car to feel slower, I mean who does. So with that said and my current mods, and the addition of headers, I should be looking at an improvement in the 1/4 mile right?
Good topic BTW, very informative
From my knowledge, headers give the exhaust gases an easier/more efficient way of leaving the engine which in turn equals hp. Weather it be on a N/A or supercharged.
Question on a comment made by Mike...you will lose low end torque when adding headers. If headers are put on a GTP will the low end torque loss be as great as it would be on a GT? I mean headers are gonna make the car faster either way correct?
Also, would I be looking at higher top end power over stock manifolds without dropping a pully. So basically would there be an improvement in trap speeds in the 1/4 mile....right?
Im only asking because Im planning on getting headers for my GTP in the near future. I dont want to have to drop a pully size if i dont have to because of the low end torque loss metioned earlier. I basically dont want the car to feel slower, I mean who does. So with that said and my current mods, and the addition of headers, I should be looking at an improvement in the 1/4 mile right?
Good topic BTW, very informative
i think ron nailed it, idle and cruise gt's might benifit more(how much ill leave that for the pros to fiure out, but once any kind of boost is seen more flow is required from the added pressure, which is where the exhaust will see more pressure
and doesnt mike know a little about l36 motors....he did build a "turn key built up street /strip car" i think some knowledge would be needed for this, i doubt he glued it all together and hoped for the best
well thats where i stand on headers ...couldnt we argue this over a dyno sheet, and see where headers gain power over exh. manis
i think when it hits boost we will see the largest gain by them........?
and doesnt mike know a little about l36 motors....he did build a "turn key built up street /strip car" i think some knowledge would be needed for this, i doubt he glued it all together and hoped for the best
well thats where i stand on headers ...couldnt we argue this over a dyno sheet, and see where headers gain power over exh. manis
i think when it hits boost we will see the largest gain by them........?
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