Variable Electronic Exhaust Bypass / Cut out?

[bkw]

One of my friends has an STi and had just installed the qtec exhaust bypass on his car and I was pondering doing the same for my speed3 but perhaps a little differently.

In the STi under 'power' mode he'll keep the valve closed in 1st and 2nd gear, and half way through 3rd to keep the low end torque. He'll then switch the valve to the open position in his upper gears to add a bit more power up top. We dyno'd his pre-tuned car last thursday and we noticed some noticeable gains with the valve open and more power in the upper range where the motor would fall off when stock.

Thinking that I (or someone) can rig up a similar device but automated by tapping into the speed sensor out triggering an on/off toggle. So lets say when the system is 'armed', it'll open the valve at ~50mph.

-or-

Do it manually like my friend. It's really not that hard - he's got his switch mounted behind his steering wheel so that all he needs to do is push a button to engage.

Just thinking out loud here guys.. what do you think?

 

[Focused]

I've had the cutout idea in mind since day 1, but I'm still waiting on it simply because I don't have a tuning device for the car yet, and I'm not ready to jump into any of the devices that are already out (waiting on PnP).

IMO the proper way to run an open DP is with the right tune (can't just slap it on and call it a day...the ecu needs to be tuned for it)....and besides, with the excessive smoking issues people are having with their TBEs right now, I'm in no rush to do my downpipe. I'd like to wait alittle bit more and see if there's any new news regarding what the exact problem is.

BTW, where in NY are you?

 

[jeffmsp]

there is no reason to have it closed in 1 and 2, the less backpressure, the less turbo lag, the more low end grunt u get, he has it backwards as many do when they mod a turbo car. no backpressure is best at all rpms with a turbo. consult any intelligent book on turbo performance and they will all agree. Just keep it open when racing, closed when cruising.

 

[bkw]

Westchester County - moved up here after 9/11

As for awaiting a proper tuning and ecu manipulation device, I've thought of that as well especially after seeing the gains on my friends STi with a little bit of programming and the bypass.

But, our speed3's run so damn rich it's silly and those who've installed an MBC have shown that the turbo can handle at least 18psi - what I'd imagine would be what our cars would boost spike at with the bypass installed.

Speaking of MBC and FCD's, I've just placed an order for these two as well. Once installed I'll do some dyno runs to see where my af is. If she still runs a bit rich I'll seriously consider picking up the qtec electronic bypass. Theyre quite cheap - but I imagine the install costs would be more than the device itself. Gotta find someone who can cut up my SS turboxs rp w/o bending me over.

 

[bkw]

So was thinking a bit more on this subject. I've got the race pipe but it's made out of SS which is a bit hard to cut and re-weld properly.

So.. what about keeping my stock exhaust and just cutting out the first resonator and installing the bypass where the resonator once resided?

Here's a picture to give you an idea of what I mean. The first resonator behind the second cat would be replaced.

edit - looks like the powers that be are afraid of users linking to outside sites.. Anyways, you can find this pic by going to s t reet un it<dot> com/photos/MS3Exhaust_Small.jpg

 

[Focused]

True, with the BCD you'll probably be able to run the cutout without issue, but it's not solely the a/f I'm concerned about, but also overboosting. Timing is another issue altogether, but I haven't seen much data to make me too worried about that yet...

The car's gonna gain a few more psi with the less restrictive exhaust, so I'd probably want to play around with the MBC to a point where everything's within reasonable limits.

BTW, where abouts in Westchester? Yonkers, here! There's at least 5 MS3's in the area now. Think it's time for an MS3/MS6 g2g.

 

[Focused]

Hmmm...if it were me, I'd want the cut out as close to the turbo as possible...looks like the first resonator's kinda far and IMHO just not worth the trouble. If I'm going to do a cutout, I'd go to Meineke [with my racepipe installed] and tell them I want another pipe done with the cutout installed.

A few months ago, I went to Meineke to see if they could make me a race pipe but the guy wouldn't do it because the cat was there, and he's known for doing custom exhausts for locals. However, if I have the racepipe there, he'd probably be more open to doing a replacement pipe for that, since he technically didn't take off the cat himself.

If they give me problems, I know of an exhaust shop in Queens that does decent exhaust work [at least they did a couple of years back].

 

[rodney]

if you run a cut out be carefull because i did that and it shot flames out some times and eventually blew a hole threw the heat shield and it got hot enough to melt the BOdy control harness mounted right to the floor under the carpet right under the shifter, and i had to buy a new harness and it ain't cheap just a little heads up

 

[dkswim]

ive been whanting to do this i was contemplating putting an aditional pape at the end of it with a tip pointing down.

 

[knowledge007]

I've had the cutout idea in mind since day 1, but I'm still waiting on it simply because I don't have a tuning device for the car yet, and I'm not ready to jump into any of the devices that are already out (waiting on PnP).

IMO the proper way to run an open DP is with the right tune (can't just slap it on and call it a day...the ecu needs to be tuned for it)....and besides, with the excessive smoking issues people are having with their TBEs right now, I'm in no rush to do my downpipe. I'd like to wait alittle bit more and see if there's any new news regarding what the exact problem is.

BTW, where in NY are you?

LIke to clarify that the smoking has nothing to do with the any TBE...

 

[Focused]

True, I'm aware of that, though I could see how my wording might misinform people...

Thing is, from what I've read, having a TBE on seems to accelerate the process of the seals going, as there are quite a few more ppl with TBEs smoking than stock exhaust MS3s smoking.

That's all I was trying to get at.

 

[laloosh]

I have been wondering about this as well. I am most likly going to CPE my car out and place the cut out on the bottom half of the downpipe. Run it only on the track or when im running someh1 else. YOu dont really need to tune for this in my opnion. As for gains....eh im keeping the stock catback most likly so im sure they will be there, with a bigger aftermarket one, who knows.

 

[laloosh]

True, I'm aware of that, though I could see how my wording might misinform people...

Thing is, from what I've read, having a TBE on seems to accelerate the process of the seals going, as there are quite a few more ppl with TBEs smoking than stock exhaust MS3s smoking.

That's all I was trying to get at.

it has nothing to do with TBE though, its the fact that your stock exhaust system creates enough back pressure while the cats eliminate the smoke. Just because you dont see doesnt mean your seals arnt blown already. Its a pos design and im sure every single ms3/6 will smoke eventually.

 

[northmiler89]

..im just waiting for the PnP