I'm think about getting a cutout done on my car and I'm wondering who else has done this and if so what kinda gains did you get out of it? A couple fourth gen friends of mine put there's right after the axle before the muffler...easy to get at and sounds good.

 

i put mine where my cat used to be and it netted me a solid 10hp on the dyno. i do have headers though.
Andrew

 

A buddy of mine got the one where you pull on the cable to open it, kind of like a trunk release. He ran a 13.23 with out it and when he opened it he ran a 13.16. Not too bad for a $50 piece.

Brian

 

I thought the biggest they made was 2.5 inches??? Is that true? Where can I get one that is 3 in??

 

I have a 3" cutout that I bought from Summit. It's the 3 wingnut type because I didn't want the cable version. I'll be testing it on the track a week from Friday if you want more numbers to compare to.

 

I do want numbers, but I also want to do this from the drivers seat. Any cable 3 in ones??

 

I did put forth a weak effort to find a cable-actuated 3" cutout, but the biggest I saw in Summit or Jegs was 2.5". I can only assume it's because most people put them before the cats, on the smaller pipes.

 

I'm just looking for the wing-nut setup. There's a local shop that will fab one up for dirt cheap. And yes Synapsis I would like to hear the results. If you remember, please send me a private message or email when you are able to test it out.

 

On my 85 TA I could take the gutted cat off easily because it is the bolt-on style. I gained a consistent, .2 in the quarter and 2 mph.

nick

 

Had it on my car when everything else was stock:

.15 quicker ETs and 1.2 - 1.5 mph gains consisently.

Now with the 383, same results.

Sparks a flyin'

 

Thanks guys, that's pretty consistent with an LS1 guy I was talking too. He gain 10HP to the rear wheels, about one tenth off his ET and ~1MPH.

 

Ok, I promised numbers... here they are:

SLP headers/catco cats, 3" catback:

<PRE>
Cutout
Closed Open

R/T .557 .614
60' 2.102 2.104
330 6.116 6.077
1/8 9.475 9.404
MPH 72.75 73.44
1000' 12.387 12.287
1/4 14.836 14.710
MPH 92.22 93.24

</PRE>

These runs are 15 minutes from each other. I was hoping the exhaust change as a whole would net me more power. But you can't sneeze at a solid tenth. How bout that consistent 60'? hehe

 

Synapsis, Where did you put the cut-out? I was actually surprised you would have that big of a gain from a cut-out when you already have a catback. Is your 3" exhaust mandrel bent with a free-flow muffler?

For those of you that wanna spend a lot of cash on a cut-out you can buy an electrical one from DMH Performance for around $180. It lets you adjust it from wide open to fully closed and anywhere in-between from the driver's seat.

 

Ive tested mine a few times...Now mind you this is on a BLOWN motor...But each time I opened the 3" cutout I gaine .2-.3 in the quarter mile....

Mine is where the CAT should be....What is surprising to me is that I have a fairly open setup without it...

Headman headders Into haedman y-pipe with 3" cutout into a test tube into a 3" flowmaster force II system... No AIR no CAT...But still a solid .2 to .3 difference..

Kenwood
-=ICON MOTORSPORTS=-
1987 GTA
Vortech Supercharged 355

 

Mine is after the cats, before the axle. I have SLP 1-3/4" headers, dual catco cats into Flowmaster Y with a Flowmaster mandrel bent 3" catback, single 3" inlet, dual 3" outlet 80-series muffler. I followed the 14.71 with a 14.74 and 14.75 later that night. The difference would probably be bigger if I didn't have cats.

 

I put mine before the rear axle and after my hi-flo cat. I noticed some better top end with it plus the just bad *** sound it makes Mine is three inches and I had the muffler shop make it and install it for $50. Uses 3 wing nuts to uncap (but when is it ever capped).