just got a ls1
07-26-2009, 03:50 PM
#41
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i agree with the last 2 guys, headers should be among the first few mods to get, 20whp for sure in most cases, plus you will never get the full benifit of your other mods without the headers,...talk ls6 intake....a car bone stock puts one on, and a car with headers puts one on....the one with headers is going to get a bigger gain, same with a cam, same with heads, TB, MAF, catback da da da....sure it may not be a huge gain off the bat, but get your car up to 400whp, and take off your headers for manifolds and i bet you lose close to 40whp....20 off the bat, not a lot, but it will turn into a lot more with the more mods you get, plus sound is wayyyy better
07-27-2009, 08:25 PM
#42
TECH Senior Member
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Headers are used so at higher rpms and in race engines due to the fact that under full load the intake will be at atompospheric pressure and the scavenge affect from the headers will cause a vacuum on the exhaust side allowing for even better gas exchange through the cylinder because of the greater delta p due to the header vaccuum created. Now how this really affects a stock car that doesn't spin to high and doesn't have a large overlap you tell me because I would really like to know.
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Headers are used so at higher rpms and in race engines due to the fact that under full load the intake will be at atompospheric pressure and the scavenge affect from the headers will cause a vacuum on the exhaust side allowing for even better gas exchange through the cylinder because of the greater delta p due to the header vaccuum created. Now how this really affects a stock car that doesn't spin to high and doesn't have a large overlap you tell me because I would really like to know.
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the "vacuum" pulse travels back up the primary tube, past the open exhaust valve, and into the combustion chamber; then the exhaust valve closes trapping the "vacuum" pulse in the combustion chamber; then the intake valve opens (we said no overlap), and the "vacuum" in the chamber "pulls" the air/fuel charge into the chamber...
at lower rpm there is more time for the "vacuum" pulse to "leak" out via the rings... but since the pressure differential due to the vacuum pulse can be around 8 times bigger than the pressure differential due to the intake valve opening alone (refer to David Vizard's exhaust experiments), there will still be sufficient pressure differential remaining to easily pull in the air/fuel charge (it will still be several times greater than the differential due to the intake valve opening)...
for long tube headers, the amplitude/intensity each "vacuum" pulse is pretty much the same regardless of rpm... long tube headers do scavenge effectively even at lower rpm.
Long tube headers are probably the best bang/buck mod... may be more than 20HP (more like 30 and then some).
Last edited by joecar; 07-28-2009 at 10:34 AM. Reason: clarification
07-31-2009, 08:34 AM
#43
Even if the cam has no overlap (or even if it has negative overlap), headers still pull the air/fuel change in thru the intake port (and also even at lower rpm)...
the "vacuum" pulse travels back up the primary tube, past the open exhaust valve, and into the combustion chamber; then the exhaust valve closes trapping the "vacuum" pulse in the combustion chamber; then the intake valve opens (we said no overlap), and the "vacuum" in the chamber "pulls" the air/fuel charge into the chamber...
at lower rpm there is more time for the "vacuum" pulse to "leak" out via the rings... but since the pressure differential due to the vacuum pulse can be around 8 times bigger than the pressure differential due to the intake valve opening alone (refer to David Vizard's exhaust experiments), there will still be sufficient pressure differential remaining to easily pull in the air/fuel charge (it will still be several times greater than the differential due to the intake valve opening)...
for long tube headers, the amplitude/intensity each "vacuum" pulse is pretty much the same regardless of rpm... long tube headers do scavenge effectively even at lower rpm.
Long tube headers are probably the best bang/buck mod... may be more than 20HP (more like 30 and then some).
the "vacuum" pulse travels back up the primary tube, past the open exhaust valve, and into the combustion chamber; then the exhaust valve closes trapping the "vacuum" pulse in the combustion chamber; then the intake valve opens (we said no overlap), and the "vacuum" in the chamber "pulls" the air/fuel charge into the chamber...
at lower rpm there is more time for the "vacuum" pulse to "leak" out via the rings... but since the pressure differential due to the vacuum pulse can be around 8 times bigger than the pressure differential due to the intake valve opening alone (refer to David Vizard's exhaust experiments), there will still be sufficient pressure differential remaining to easily pull in the air/fuel charge (it will still be several times greater than the differential due to the intake valve opening)...
for long tube headers, the amplitude/intensity each "vacuum" pulse is pretty much the same regardless of rpm... long tube headers do scavenge effectively even at lower rpm.
Long tube headers are probably the best bang/buck mod... may be more than 20HP (more like 30 and then some).
