Will this hurt my car?

gardner44 · Post by **gardner44** » Thu May 26, 2005 3:33 am

i use my 90 legacy for racing it is a N\A, FWD. i cut off the exhaust and all i have now is about one foot of pipe left on each side of the exhaust manifolds. i unpluged the o2 sensor, took it off and i was just wondering if that will make any difference or not in performance and if i need any back pressure for the motor or not?
P.S it sure is nice and loud now hahahah
thanks for your help...

Subaru_Nation555 · Post by **Subaru_Nation555** » Thu May 26, 2005 3:37 am

I was always under the impressions that N/A cars need at least some backpressure.

gardner44 · Post by **gardner44** » Thu May 26, 2005 4:11 am

i kept everything else just in case i have to weld it back together if i have to i guess i can just clean out the cat and put the sensor back in.. anyone else know? thanks

91White-T · Post by **91White-T** » Thu May 26, 2005 5:14 am

What kind of racing? Street?

gardner44 · Post by **gardner44** » Thu May 26, 2005 1:57 pm

Oval Racing. need some more power...

91White-T · Post by **91White-T** » Thu May 26, 2005 5:24 pm

Leave the sensor in, the ecu will be lookin for it.

BAC5.2 · Post by **BAC5.2** » Thu May 26, 2005 7:33 pm

91White-T wrote:Leave the sensor in, the ecu will be lookin for it.

Only in closed loop.

The ECU sees the O2 sensor signal in open loop, but doesn't do anything with it. It doesn't respond quickly enough, and the ECU says 'fuck it' and just starts throwing fuel from a base map.

gardner44 · Post by **gardner44** » Thu May 26, 2005 7:43 pm

so take the sensor out of the cat, plug it in and just tie it up somewhere??

BAC5.2 · Post by **BAC5.2** » Thu May 26, 2005 11:12 pm

NO! Do NOT plug it in if it's not in the exhaust stream.

Just leave it unplugged, or have a bung welded to the pipe and have it there.

It's either in the exhaust stream, or not at all.

Do you have each side freely dumping into the atmosphere? Like, not after they join, but right off of the head, they just dump a few inches away? I want a sound clip of that!

gardner44 · Post by **gardner44** » Fri May 27, 2005 4:19 am

ya its very loud i will see how loud it is tomorrow at the races when i get to rev it up

ok so i'll leave it unpluged. and yes each side is individual and has about one foot of pipe facing the rear.

I'm going to bring ear plugs just in case its too loud inside when i'm driving it

i can get a pick or sound clip of it if any one wants to see it, just let me know
thanks guys for the help
Adam

greg donovan · Post by **greg donovan** » Fri May 27, 2005 6:54 am

i really want to see/hear this thing.

my car had better top end w/ 2.25 and a one cat w/a resonator/glasspack on my 90 FWD that we rallycross.

but i need more midrange/bottom so i added a second resonator at the end.

plus it was way too loud to drive around town w/the kids. w/ two resonators it was just right.

good luck!

gardner44 · Post by **gardner44** » Fri May 27, 2005 1:19 pm

i will post a pic tomorrow. so will i lose some midrange power by having the exhaust cut off so short? and by having no back pressure is ok for the engine?
thanks guys. Racing tonight Can't wait

better not rain

mikec · Post by **mikec** » Fri May 27, 2005 1:29 pm

There's nothing in the rules about having the exhaust exit behind the driver?

I'd be worried about carbon monoxide when I was waiting to get on the track.

But yeah, I want to hear it too!

free5ty1e · Post by **free5ty1e** » Fri May 27, 2005 1:48 pm

Exhaust backpressure is necessary to some extent for optimum power on NA vehicles... IIRC, has to do with keeping the exhaust gas veloticy up.

With a turbo, the less backpressure you've got the better. An engine with air forced into it will create plenty of its own exhaust velocity

On another note, however, I'm sure that open-header boxer engine sounds nice

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Will this hurt my car?

Will this hurt my car?