Will Cut Outs Improve my E.T?

Posted By: mrmopardan

Will Cut Outs Improve my E.T? - 05/18/11 01:56 PM

I make a occasional 1/4 Mi. pass down the track. I race with full 3 " TTI exhaust with their Dynomax mufflers. This exhaust seems to flow well but I'm wondering if there is even more performance to be had through exhaust modifications. would there be an improvement by adding "cut outs"? Anyone tried this and if so where is the ideal location to install and which brand. Thanks, Danny

Posted By: Mr.Yuck

Re: Will Cut Outs Improve my E.T? - 05/18/11 02:23 PM

un-capped seems to pick up 2-5 tenths depending on system. Since you have a decent 3" I'd guess you'd pick 2 or so. Enought to dip into the 11's I'd think. My old 67 coronet w/ a mild 440 and 2.5 system would drop 3.5 tenths w/ the exhaust open.
And before those guys who get on here and claim no difference.. I don't count a 3.5 with a race mufflers and no tail pipes as an exhaust system.

If you want to see how much, un-cap the headers and make a blast. That way you'll get an idea.

Posted By: DodgeCharger

Re: Will Cut Outs Improve my E.T? - 05/18/11 02:24 PM

I would doubt it would improve enough that you would notice it. I run a full 3 inch exhaust with magnaflows and if I drop the exhaust I don't really notice much improvement. maybe .05 at the most.

Posted By: MR_P_BODY

Re: Will Cut Outs Improve my E.T? - 05/18/11 02:34 PM

I am planning a cut out system for my Rampage BUT I
will have a header with about 16" long collector and
I will come off the side of the collector to run to
my exhaust, where most guys run straight off the back
of the collector... you would need to jet differently
without the exhaust... this is where guys dont see
any change due to not jetting for the change... I
plan on a split on the jetting... not perfect for
either set up, unless it will see alot more street
mileage, then I'll jet for the street and the exhaust

Posted By: slippery440

Re: Will Cut Outs Improve my E.T? - 05/18/11 02:38 PM

Same question almost a few days ago. Same answer. We found that if you drop the whole exhaust system off the car you will gain .1 to 1.5 in the 1/4. We guess some or most of that gain was for the lost of weight. You are just adding cut outs. Probly all your going to gain is to the noise pollution.

Is it worth the hassel? If you have a totally junk exhaust yes if not no.

Posted By: oldiron

Re: Will Cut Outs Improve my E.T? - 05/18/11 03:21 PM

66 belvedere, 431/tti 1 7/8, 3 in (with tailpipes), dynomax, 4sp, cutouts
saw no consistent measureable difference (best 11.07, consistent 11 2s to 3s. Would often run street stick class (closed) and quick stick (open) one after another. Liked the pipes open so I could hear engine revs on shifts (know if clutch slipped), plus I basically like the noise. If anything, slowed down slightly w/cutouts open, ran lean. If carb was jetted properly for open pipes probly would have picked up, but never tried cause I'm basically lazy.

Posted By: mrmopardan

Re: Will Cut Outs Improve my E.T? - 05/18/11 07:01 PM

As I continue to research this subject.. I also have the oval GTX exhaust tips too. Are they restrictive??

Posted By: dustergirl340

Re: Will Cut Outs Improve my E.T? - 05/18/11 07:23 PM

Quote:

this is where guys dont see
any change due to not jetting for the change...

amen to that! I've picked up 3-4 tenths with open exhaust AND jetting. I once forgot to re-jet when I uncapped and saw no gain, and ran very lean to boot.

Posted By: Moparnut426

Re: Will Cut Outs Improve my E.T? - 05/18/11 07:35 PM

I have seen guys switch to a more free flowing exhaust and have a slower E.T. and had it run leaner. So there is a lot to just dumping the pipes and goin racing.

Kasey

Posted By: ProSport

Re: Will Cut Outs Improve my E.T? - 05/18/11 09:01 PM

I ran an X-pipe on my old car with Magnaflows and turnouts in front of the rear tires, it was pretty quiet and ran 9.90 with or w/o the exhaust system.

Posted By: Jeff_383

Re: Will Cut Outs Improve my E.T? - 05/18/11 09:12 PM

68LAR went from a 11.60 to a 11.28 just with opening the exahust. No jetting change. He has a full 3" sysytem with dynomax ultraflows.

Posted By: Mr.Yuck

Re: Will Cut Outs Improve my E.T? - 05/18/11 09:24 PM

Quote:

68LAR went from a 11.60 to a 11.28 just with opening the exahust. No jetting change. He has a full 3" sysytem with dynomax ultraflows.

I think I was the winner of the "how much faster" contest on that one.

Posted By: Moparmal

Re: Will Cut Outs Improve my E.T? - 05/18/11 11:47 PM

Quote:

I would doubt it would improve enough that you would notice it. I run a full 3 inch exhaust with magnaflows and if I drop the exhaust I don't really notice much improvement. maybe .05 at the most.

Same deal - Magnaflows with twin 2.5" and X pipe.

I have electric cuot outs, I open them at the track and tune one stage richer and no difference.

If I don't tune one stage richer it leans and I go slower.

Thats the benefit of maganflows - they actually flow.

Posted By: Locomotion

Re: Will Cut Outs Improve my E.T? - 05/19/11 12:18 AM

A lot depends on how the carb is jetted. Typically, ideal jetting for a closed exhaust will be lean for an open exhaust. Of course, the more cubes and rpm's you have, will also be a factor, so the results depend on how efficient the exhaust is compared to the amounbt of air/fuel you're putting through it.

I've been running TTI step headers on my 360 for years and had the carb tuned for it as best as I could. A few years ago I installed a 3" x-pipe and Dynomax Ultra Flo mufflers (oval) ending at the rear end housing. After some carb tuning which I believe included dropping the jet sizes 1-2 numbers and getting the weight back to what it was (system was +60 lbs), the car was about .5-.10 faster than open headers! I can only assume that the x-pipe affected the jetting, overall helped my particular combination and that the mufflers were not a restriction.

Posted By: HYPER8oSoNic

Re: Will Cut Outs Improve my E.T? - 05/19/11 01:18 AM

Quote:

I am planning a cut out system for my Rampage BUT I
will have a header with about 16" long collector and
I will come off the side of the collector to run to
my exhaust, where most guys run straight off the back
of the collector... you would need to jet differently
without the exhaust... this is where guys dont see
any change due to not jetting for the change... I
plan on a split on the jetting... not perfect for
either set up, unless it will see alot more street
mileage, then I'll jet for the street and the exhaust

Posted By: BLONDE BARRACUDA

Re: Will Cut Outs Improve my E.T? - 05/19/11 02:32 AM

Posted By: DaveRS23

Re: Will Cut Outs Improve my E.T? - 05/19/11 02:39 AM

Quote:

un-capped seems to pick up 2-5 tenths depending on system. Since you have a decent 3" I'd guess you'd pick 2 or so. Enought to dip into the 11's I'd think. My old 67 coronet w/ a mild 440 and 2.5 system would drop 3.5 tenths w/ the exhaust open.
And before those guys who get on here and claim no difference.. I don't count a 3.5 with a race mufflers and no tail pipes as an exhaust system.

If you want to see how much, un-cap the headers and make a blast. That way you'll get an idea.

My car picks up about .2 with them open. And I agree that testing with the exhaust open at the track will tell you what you need to know.

Because there is a car show most weekends around here, I hit a couple a month. Which means the car sees more show time than track time. The cut-outs are more fun at car shows than they are at the track. I have cops come by and ask me to open them up and fire it up.

Cut-outs are just tons of fun on the street! The added performance at the track is gravy.

Posted By: StealthWedge67

Re: Will Cut Outs Improve my E.T? - 05/19/11 06:04 AM

When I bought my car it had a fairly new exhaust sytem with Flowmasters on it, but it was 2-1/4" pipe. So I added about 18" of 3" pipe off the headers (to get past the subframe) leading to a set of 3" cutouts, then it steps down to 18" of 2-1/2, and then down to the existing 2-1/4" setup. I see a solid .25 when open, but my system is relatively restrictive compared to a full 3" system.

To make it pay, you really need to rejet