To dump or not to dump?

[NEARING]

That is the question :zahn:

I haven't run the car with the dump open.

With Hooker exh I wonder if it would help or hurt?

Guess I'll see soon.

[Doober]

I dont see why it would really hurt, but it might not help too much either. Just get one of them electric cutouts and dump whenever you feel like it :elefant:

[JayC]

With the Hooker mufflers, your car will be faster with the dump

[mgmshar]

Depends on exactly how restrictive the Hooker system is...

When I had the stock exhaust on my car, opening the dump made a HUGE difference. I would pick-up about 3-4psi of boost with no other changes, just because the back-pressure after the turbo was so much lower with the dump open. Now that I have my ATR 2.5" exhaust, opening the dump makes very little difference.

Make back-to-back runs with and without the dump open. You'll get a good idea of how restrictive your exhaust system is. If the boost doesn't increase at all when you open the dump, your exhaust system flows very well.

:top:

[GrndNatnl]

Dont know how true that is. My exhaust system isnt all that great. Stock Y-pipe, unknown mufflers, cat replaced with testpipe with a dump. When I open it, I notice no visual increase of boost on the gauge. Dont feel any seat-of-the-pants power increase either, except that it spools a lot faster. (And sounds wicked!)

Also rattles loose any ear wax while cruising at 50 mph.

As I said though, I dont know because I havent track tested it to compare results. Kind of hard to do when its my daily transportation. Racing is out of the question.

[SYTECH]

On my 87 GN / TA49 / 009's / stock stall, I was running a consistent 12.2 to 12.4 in the 1/4 mile

I put on an electric cutout and swapped in a 3200 rpm stall convertor and 1st run out was an 11.86

Best 2 mods I feel that I did to my GN

Good Luck

Ray

[TType85]

I have a 3" THDP, Dump and Kenne Bell 2.5" Dual setup with dynomax turbo flow mufflers on my car. I picked up nearly 4# of boost uncaping it. Picked up 2mph in the 1/8.

[tim87tr]

With the Hooker mufflers, your car will be faster with the dump
I found this to be true for my mostly stock Turbo T. The car picked up 0.8 mph and .08 ET with no other changes besides opening the 3" dump on the downpipe. I have the Hooker exhaust with Aerochambers :albert:

[turbojimmy]

The dump sounds cool, but didn't do much for me. I have a THDP and 3" dual exhaust all the way back. Opening up the dump just made it louder. No more boost, didn't feel quicker (though never ran it open vs. closed).

I just like to instill the fear of God in my neighbors when I fire it up.

Jim

[TTA850]

I have a 3" TH downpipe with an ATR crossflow exhaust for TTA and have found that opening the dump made a difference,though I still like running quiet and surprising people :D

Through the exhaust I went 10.75@124.86mph with a 1.50 60ft

The next week I opened the dump and went 10.69@125.80 with a 1.47 60ft with the same boost(I have the innovative MSBC so I didnt see a boost increase)

So I picked up .06 ET and .94 MPH in similar conditions(it was about 10* warmer and about 10% more humidity the day I ran the dump open)

HTH,
Steve

[NEARING]

Guess I'll have to wait and see.

Guess the faster the car the more diff?

Thanks.

[JoeNational]

I have the THDP 3" DP and when i open it up i see a huge diff it feels like the car is about to pick those tires right off the ground, and the sound well cant be matched ppl lock and dont know what to think, but i also have the stock exahust so most of the time iam running the dump open around the streets, yet to take it to the track.

[jmidolo]

This is one of those "Get a dif reply from everyone" thread. Most people will experience some sort of gain by uncapping the exhaust. How much you will see is all dependant on the exhaust you're using. Running a dual ATR 3" system you're not going to see anything vs. running a dual hooker setup or a stock location Dynomax.

I'm betting you'll see something with them Aerochambers. I don't see much w/my 3" ATR Xflow system.

[Geoff87]

On my car it makes a difference, because I'm running an older, less free flowing exhaust.

On top of that, it just sounds too cool to not uncap at the track. :rock:

[sfiturbox2]

TE72 on the wifes car spools like a SOB and VERY loud "wistle" (like a semi)with electric dump open, the stocker set up on mine just makes the interior louder,not much difference using the butt dyno method.

[Buick GN Boosted]

http://www.buickgn.com/Exhaustcutout.mpg :top:

[WakkoSS]

Once I starting using the propain at 23psi, opening the dump did nothing for me except make a whole lotta noise.

[denn454]

i droped 3/10ths with thestock muffler, i wouldn't expect that kind of change with the better hooker mufflers but it still won't hurt any.

usually you hear a lot of people sayign not to dump the exhaust, thats a big thing with v8's, if you dump it you loose all your backpressure and loose power, the same is not true for us, don't get comfused. a turbo provides more than enough (much more) backpressure, i've heard of someone having just under 30# of back pressure in the cross over pipe, if thats not enough back pressure please tell me what is. anything you can do to free up the exhaust after the turbo will only help.

you can get a weld in dump pipe from summit for $35, thats what i just did. or just unbolt the cat or test pipe, hopefully you have a gutted cat, right before the exhaust flange, bole it back up offcenter (left and right of eachother) or if you have enough ground clearence the exhaust side hanging below the dp.

its well worth it, even though i don't care for the sound.

[Tom Shea]

The effect of running an open dump is going to be determined by the amount of backpressure in your cat back system. If yo have a very free flowing system, then less gain. If you don't know for sure, then i would suggest being careful about the boost level. If you can, turn it down at first. The back pressure can and does act like a boost limiter.

[turbot2112]

i ran my car with the dump closed and then with it open on the same night. car was 3 10ths slower with the dump open. :stupid: dont make sense to me.

[NEARING]

i ran my car with the dump closed and then with it open on the same night. car was 3 10ths slower with the dump open. :stupid: dont make sense to me.

Did the MPH drop also?

[Bruce Davis]

I have a THDP with his high flow cat. Will I gain anything by switching to a straight pipe? ( more flow ) Thanks guys. :happy:

[Tom Shea]

The cat back system backpressure I previously referred to would also apply to any turbo downstream backpressure. The reference to cat back was for the purpose of referring to the dump pipe which is usually located in the test pipe. There are other dumps such as a fenderwell, directly downstream from the turbo. For the purpose of this topic just use turbo downstream back pressure.

[Tom Shea]

Take a look at your Cat. Do you think it flows less freely than a straight pipe? If you try to lower the back pressure on your turbo downstream exhaust system, I advise to try to limit the boost level at first. You may be suprised by the increase.

[lazaris]

i ran my car with the dump closed and then with it open on the same night. car was 3 10ths slower with the dump open. :stupid: dont make sense to me.
If this was in fact the case then most likely you were too lean.

[Roger]

A Buick is supposed to be quiet & I'm still trying to learn the best system to make it quiet - ATR 2.5" Pit Bulls are way too loud.

Doober has the right idea & I already have my electric cutout installed.

[jmidolo]

My 3" ATR Xflow is not what I would call loud. It sounds and flows excellent. :rock:

[Chuck]

ATR headers, 4 bolt turbo, home made dual 2 3/4" exh, Ultraflow muffs, no cat. Made several dyno pulls and then repeated w/ dump open.... 3hp. :racer:

[Turbo Brian]

my exhaust is very free flowing with a mease dp, dump pipe, atr 2.5". while i didnt make back to back runs at the track, just street driving made no noticible difference. the only advantage i saw at the track was being able to hear my car running. with a helmet on and a loud car next to me, i cant hear my car running through the muffs. the dump comes in handy as i used to stall the car frequently after a burnout and not realize it cuz i couldnt hear anything :)

performance wise, it all depends on what you have after the dump.

[Ross]

I don't like running w/ the dump open. I think it sounds funky, and I it doesn't feel any faster to me. It actually feels like some torque is lost.

Ross

[GHawz13]

From what I heard when you open the dump you will lose some low end power but having less restriction you will gain top end. I am not totally sure about this , but I have heard this before.

[mike85gn]

I used to run without an exhaust system, after switching to a custom 2.5" stainless unit with some straight-thrus, I noticed no power loss and a whole lot less noise!

[tweaked]

If you are slowing down - Youy are too lean.

Fatten it up a little ... and FLY!!!

Have a nice day.

LC

[turbosnail]

I just posted a similar question, ATR2.5 SS duals, car feels quicker throughthe mufflers than through the exhaust cutout