Defined Autoworks Header Install!

j9fd3s · 06-26-2011, 12:31 PM

i haven't checked backpressure on the P port yet, but it is on the agenda shortly. i did check it on my stock FC though, and it made tuning so simple its funny, i don't know why we don't use it more.

Libor · 06-26-2011, 12:49 PM

Quote:

Originally Posted by j9fd3s

i haven't checked backpressure on the P port yet, but it is on the agenda shortly. i did check it on my stock FC though, and it made tuning so simple its funny, i don't know why we don't use it more.

Could you contribute more? This is something very interesting, unfortunately not much examined on public rotary forums

j9fd3s · 06-27-2011, 11:49 AM

sure, um the gsl-se and the 86-88 NA cars make doing this very easy, so its a good place to start. my car happens to be 100% stock, mileage is 76K now, 74k at the time.

so the 6 port cars use exhaust backpressure to move the 5th and 6th ports, so all i did was tee a boost gauge in the 6 port hose, and then go for a drive.

the results were interesting, the gauge and the butt dyno agreed 100%, or more accurately the boost gauge and the tq curve agreed.

the stock exhaust did ok, up to about 4500, then backpresssure starts to climb. so its under 1psi, until 4500 then it comes up pretty quick and peaked around 4.5psi.

i pulled the cats off, and behold the center cat was all melty, so i hollowed it out, and was rewarded with 3.5psi of backpressure. seat of the pants improvement was bigger than the SAFC.

the next step would be to put the gauge actually in the exhaust manifold, i'm not sure but i suspect i'm measuring the rear half of the exhaust. as the pickup is in the main cat.

the concept works though, and its easy to do. higher exhaust pressure = lower power.

06-26-2011, 12:31 PM	#1
j9fd3s Rotary Fanatic Join Date: Mar 2008 Posts: 123 Rep Power: 18	i haven't checked backpressure on the P port yet, but it is on the agenda shortly. i did check it on my stock FC though, and it made tuning so simple its funny, i don't know why we don't use it more.

06-27-2011, 11:49 AM	#3
j9fd3s Rotary Fanatic Join Date: Mar 2008 Posts: 123 Rep Power: 18	sure, um the gsl-se and the 86-88 NA cars make doing this very easy, so its a good place to start. my car happens to be 100% stock, mileage is 76K now, 74k at the time. so the 6 port cars use exhaust backpressure to move the 5th and 6th ports, so all i did was tee a boost gauge in the 6 port hose, and then go for a drive. the results were interesting, the gauge and the butt dyno agreed 100%, or more accurately the boost gauge and the tq curve agreed. the stock exhaust did ok, up to about 4500, then backpresssure starts to climb. so its under 1psi, until 4500 then it comes up pretty quick and peaked around 4.5psi. i pulled the cats off, and behold the center cat was all melty, so i hollowed it out, and was rewarded with 3.5psi of backpressure. seat of the pants improvement was bigger than the SAFC. the next step would be to put the gauge actually in the exhaust manifold, i'm not sure but i suspect i'm measuring the rear half of the exhaust. as the pickup is in the main cat. the concept works though, and its easy to do. higher exhaust pressure = lower power.