cutout

**JattGunMan** · 04-18-2006, 07:51 PM

i had my cutout for a few weeks now and i decided to cap it today just for fun..and for some reason the car seems quicker with the cutout capped?y?
i have a 2001 ss basically stock

**redline** · 04-19-2006, 06:33 PM

because it has more backpressure

**chad2000ss** · 04-19-2006, 06:36 PM

what you are feeling is more low end torque, when it is open you gain more top end. in the long run , run it open you gain more over all.

**Mr. Luos** · 04-19-2006, 06:45 PM

Closed is better for everyday driving.

Open is best for dyno pulls and track time when you are really running the car in the upper RPM's.

**redline** · 04-19-2006, 07:31 PM

depends if you had it tuned yet, its not rare to see a loss in hp when running open headers without a proper tune.

**The Scientist** · 04-21-2006, 06:11 PM

All of the above is correct. Its that simple.

**mrr23** · 04-26-2006, 02:27 PM

it's not because of that mythilogical backpressure. it's due to low rpm exhaust velocity. what happened when you opened the cutout is it caused the exhaust to slow down in the lower rpms. basically idle to 3000 rpms. once above 3000 rpms, the exhaust can now better utilize the larger opening in the exhaust. i've been there and done the cutout thing.

Now here's results of my exhaust endeavors. This is with 200 n2o. the stock vs cutout was same day.

distance --- stock --- cutout --- cutout colder --- Bassani
60ft ------- 1.987 ---- 2.074 ------- 2.020 --------1.969
1/8 -------- 7.902 ---- 7.912 ------- 7.990 ------- 7.739
mph ------- 93.20 ---- 93.97 ------- 92.16 ------- 98.60
1/4 ------- 12.102 --- 12.080 ------ 12.191 ----- 11.814
mph ------ 117.12 --- 118.06 ------ 118.20 ------ 121.35

NA times

distance --- stock --- cutout --- cutout colder --- Bassani
60ft ------- 2.033 ---- 2.073 ------- 2.031-------- 2.044
330ft ------ 5.788 ---- 5.822 ------- 5.759 ------- 5.723
1/8 -------- 8.808 ---- 8.833 ------- 8.729 ------- 8.656
mph ------- 82.33 ---- 82.55 ------- 83.70 -------- 84.27
1000ft ---- 11.404 ---- blank ------ 11.278 ------- 11.196
1/4 ------- 13.606 --- 13.636 ----- 13.449 ------- 13.345
mph ------ 101.66 --- 101.58 ----- 104.05 ------- 105.15

yes, i gained 11/13 over stock exhaust vs open 3" cutout. again, that was after 3000 rpms. a dyno doesn't show you what happened under 3000 rpms because you start your dyno run around 3200 rpms.

cutout closed

cutout open