Opinions on exhaust for the drags

[vyls1wa]

I'm looking at running a muffled exhaust straight out the headers, no cats and jumped at the diff, just for the track only, now I've shopped around a bit and have had different advice inregards to what size I should have.
Basically between a 2.5 or 3 inch twin.

Cars got 227/231 cam, 3600 stall, 3.9s with 1 5/8 pacies.

[lwboosted]

Is it just for noise? Or performance? I don't think u will gain anything if not go backwards....

[vyls1wa]

Bita both, less restrictive mufflers and no cats, I would think the right size pipe should give some improvement. I want it for other reason, but want it built with track in mind

[lwboosted]

If u already have a decent system I would be leaving it and spending the money elsewhere, but each to their own...

[tomholzy]

it will most likely give you more noise but sacrifice power/torque

[boggers007]

Cats are a big restriction so i would have thought taking them out and going with either a 2.5 or a 3 would net some gains over the same system with cats.

[vyls1wa]

i should add, a tune will be done to suit the setup for the track

[whitels1ss]

Decent cats don't cause huge restriction on a n/a car.
I reckon if you have the car tuned with a decent exhaust it would make it go backwards or might need a retune taking the exhaust apart.
I would go the 2 1/2" system if you wanted performance.
Or the 3'' system if you were just a deep loud sound. :)

Edit... you beat me to it with your last post about a tune being done for the other track system.

[whitels1ss]

Is the car to be driven on the street?
Reason I ask is are you going to have 2 tunes?
One for the street with cats and exhaust,
and another for the track without cats and exhaust?
As I said before, I don't reckon you would pick up much with no cats over a set of aftermarket free flowing cats and 2 tunes would be a PITA. :)

[Soopy]

Is the car to be driven on the street?
Reason I ask is are you going to have 2 tunes?
One for the street with cats and exhaust,
and another for the track without cats and exhaust?
As I said before, I don't reckon you would pick up much with no cats over a set of aftermarket free flowing cats and 2 tunes would be a PITA. :)

I reckon the energy needed to swap it all would be a waste.

[vyls1wa]

yeah, got an autocal for the tunes to swap. swapping over an exhaust is bugger all IMO.
money wise doesnt bother me, neither does the time to do set it up. got time on my week off.

Just thinking out loud, i dont know, which is why im askin.

[whitels1ss]

yeah, got an autocal for the tunes to swap. swapping over an exhaust is bugger all IMO.
money wise doesnt bother me, neither does the time to do set it up. got time on my week off.

Just thinking out loud, i dont know, which is why im askin.

Cool, hey if you got both tunes checked on a dyno I would be interested to

see the results as I doubt there would be any advantage or gains. :)

[vyls1wa]

hell, id do back to back at the track.

But in saying that, i want a exhaust dumped at the diff for abit of fun, but at the same time have it suited for use at the track, not entirely just for the track

[Soopy]

There might be a tiny difference in top.end power but i doubt it woukd justify the time and energy.

[whitels1ss]

hell, id do back to back at the track.

But in saying that, i want a exhaust dumped at the diff for abit of fun, but at the same time have it suited for use at the track, not entirely just for the track
It will be interesting to see the results then. :)

[dyno junkie]

Cars got 227/231 cam, 3600 stall, 3.9s with 1 5/8 pacies.

This combination should already be very deep into the low 12's.

If 12.9 is really your current time with this set up, someting is very wrong!

[vyls1wa]

12.9 , that before the new box, stall and cam

[255-LS1]

those small primary headers might be holding it back a tad

[JezzaB]

Why not just bolt on 2 little dumpers straight to the extractors? Alot cheaper and easier.

[poolkeeper]

Have you thought about electronic exhaust cutouts? saves bolting unbolting bolting the exhaust lol ...

[OMR346]

I agree about the small headers holding it back.

I have a similar set up. 231/239 cam, 3500rpm Dominator, built A4, 3.73:1 diff (currently in pieces lol), 1 5/8" Pacies, 100cpi cats, twin 2.5" Burkley system.

It is quiet on the street, and wheni go to the track, i drop the rear muffler and add some dump pipes to the flanhe to dump at the diff. It makes it a lot louder and gets rid of that restriction. In saying that though, i am yet to back to back test the 2 systems.

I ran 12.09 @ 111mph on Saturday night at Willowbank.

[vyls1wa]

yeah, headers are on the list to be replaced, that was the obvious bit.

and Jezza, my understanding is that it needs to have mufflers at the track

[dogsballs]

i'd just run a 1 7/8 headers, 100 cpi cats, twin 3". no restriction, no fuss at track, no need to change tune.

but as previously said, only 12.9, i'd be focusing on it getting down the track before farting around with changing exhaust etc.

my old thing with 225rwkw, no cam, just 4500 convertor, 4.11's, big exhaust, ran 11.95 @112mph, 1.60 60ft.

[ova400]

the biggest benefit of what you want with the shorter exhaust will be the weight, which if you intend chasing every tenth will be worth it, but otherwise it shouldn't cost much $400-500 so you could sell your current exhaust and be better off.

[RIDE:42]

I have 2.5 from turbo`s to the diff then 3 out the back bit loud in car parks but you get that .

[dyno junkie]

12.9 , that before the new box, stall and cam

Ok that makes more sense then.
Have you run it down the track yet with the new combo?

A lot of us have got into the 11's with 1 5/8" tri y headers.

[VYSHSV8]

Ok that makes more sense then.
Have you run it down the track yet with the new combo?

A lot of us have got into the 11's with 1 5/8" tri y headers.


Nah he hasn't yet Lyle the cam goes in soon at the end of this month :)

[QldKev]

Have you thought about electronic exhaust cutouts? saves bolting unbolting bolting the exhaust lol ...


That's what I was thinking.

Electric exhaust cutout and an autocal, 30 secs from street to strip.

QldKev

[silvervyss]

This might help

http://www.dmhperformance.com/ecutout.htm

[stompa]

you could get some sections made up with flanges to replace your cats then your not having to replace your whole sytem then if you want it dumped at the diff do the same again get some dump tips made with flanges and get a flange section put in before your diff

[Soopy]

That's what I was thinking.

Electric exhaust cutout and an autocal, 30 secs from street to strip.

QldKev

I hear they tend to leak a little when closed.

[Roonstain]

Some might - others don't - mostly down to the quality of the install IMHO

[Soopy]

Some might - others don't - mostly down to the quality of the install IMHO

I was under the impression allot leak around the butterfly. Also how does having an intersection in the pipe effect flow?

[Roonstain]

I know those that I have seen and used that they are fine

The cutout design and position will determine flow

If using a low profile design, this position may be a good idea for flow:
http://www.google.com.au/imgres?q=low+profile+exhaust+cutouts&um=1&hl=en&safe=off&sa=N&biw=1280&bih=622&tbm=isch&tbnid=_awvoa3mm-zlBM:&imgrefurl=http://www.camaro5.com/forums/showthread.php%3Ft%3D38210&docid=REHrrEfzLtHHzM&w=800&h=500&ei=I4RxTuCeG8OziQezvoyhBg&zoom=1


A Y-piece design is probably a little harder, but you could go for a "diverter" setup instead of a cutout - for example:
4FHdbgvNNWo

[Soopy]

That second one looks stupid imo. When its closed you essentially have a tenis ball in your exhaust.

[Roonstain]

Nah mate, don't think you can see it properly - essentially makes no difference to flow or anything when on the stock system side
Then when the button is pressed, a valve closes the stock side completely and lets all the air out of the diverted section

[Soopy]

Highly probable that i cant see it. It looked as if the normal exhaust was an after thought. But the way you explain it makes sense.

[Lincoln87]

just diff dump your current system???


and pretty sure most tracks have DB limits on certain days/nights.

i know WSID has one (not too sure if they enforce it tho)