[Jas0n]

Hi guys I'm wondering if anyone else out there has experienced this:

I'm driving an '07 Sti.

My current setup is a catted Cobb downpipe hooked to a SPT catback. Before the SPT, the COBB DP was hooked to the stock exhaust. This hookup was flawless as it fit perfectly with no leaks.

Now with this SPT I find the fitment poor. The Doughnut gasket on the Cobb exhaust appears to be too deap to mate properly with the SPT. (maybe the mouth of the SPT is too small?)

When I did manage to get the two alligned (using the stock spring bolts as the ones that came with the SPT exhaust are worse), I tightened the S*$% out of it but there is still a noticable leak. I could even see condesation dripping the from join. There also seems to be a noticable (but not loud) noise coming from the leak which worries me.

My questions are:
1. Will this hurt my car?
2. What can i do to seal this exhaust better? Maybe try a different doughnut gasket? regular gasket? I'm seriously concidering welding the two together at this point!

Thanks.

[IGoFast1589]

I don't see how the SPT hardware could be any worse than the stock spring bolts because those things are completely terrible...

[Jas0n]

Originally Posted by IGoFast1589

I don't see how the SPT hardware could be any worse than the stock spring bolts because those things are completely terrible...

they were worse in the fact that they could not tighten the dp and catback anywhere near as close as they should have been to make a seal. The leak would have been ridiculous!

I too am very suprised too to see the stock bolts did a much better job.

[Oi_Oi_M8]

I've been running the Cobb catted downpipe with SPT Catback setup for 2 yrs and haven't had a problem with it at all. Replaced all the exhaust gaskets a few months ago (just cause I'm anal like that), but again had no problem with fitting.

Is it too late to send it back?

[mond12345]

Try a new donut gasket?

When did you get the COBB DP if you don't mind me asking?

[kpnorton]

similar problem, but certainly not the same.

I am using a Titek DP with a full 3" flat flange connection and mating it to an Apexi GT Spec cat back that necks down and is designed to be used with the donut gasket.

I developed a leak where the somewhat poorly fitting gasket that was sold with the downpipe blew out.

I ordered a Remflex gasket which was recommended to be good at this connection point, though I have read mixed reviews of their other products.

If you can go to a "flat flange" gasket, this might be an option. Check back with me in a week or so if you want to hear the results of the install.

[Jas0n]

Originally Posted by Oi_Oi_M8

I've been running the Cobb catted downpipe with SPT Catback setup for 2 yrs and haven't had a problem with it at all. Replaced all the exhaust gaskets a few months ago (just cause I'm anal like that), but again had no problem with fitting.

Is it too late to send it back?

yeah i've had it on the car for about 2 months now.. way too late to send it back at this point...

I'm going to remove the donut gasket and maybe try a flat one of some sort.

Thanks everyone fore the input!

on a different note, according to my AP i'm only hitting a max boost of 16.4 psi... this is in a 4th gear pull.. now i'm really starting to get worried

[AP1toGDRev.G]

Mine leaked at first (stock CBE) but I tightened the crap out of it and after a few heat cycles it sealed.

[kpnorton]

Originally Posted by Jas0n

on a different note, according to my AP i'm only hitting a max boost of 16.4 psi... this is in a 4th gear pull.. now i'm really starting to get worried

what map are you using? Cobb stg2 "off the shelf"?
what did you used to max at?
what are you holding at 6500-7000?
your sig says Toronto which is 254 ft above sea level. Is this where you are driving?
can you log MAF (mass air flow) with the Cobb AP?

[Jas0n]

Originally Posted by kpnorton

what map are you using? Cobb stg2 "off the shelf"?
what did you used to max at?
what are you holding at 6500-7000?
your sig says Toronto which is 254 ft above sea level. Is this where you are driving?
can you log MAF (mass air flow) with the Cobb AP?

yes toronto - cobb stage 2 1.04 Off the shelf map... 16.4 seems low as it should be around 18 to 19 i believe for a Stage 2 car. To be honest i've never used to AP to monitor boost until now.. although I do have the stock boost guage which i could have sworn would show shomewhere around 0.125 mPA, (18 psi) maybe about a month ago... I do hear a whistle noise when letting off the gas while boosting, is this normal or indication of a leak?

i've been reading around the forum though and it looks like an exhaust leak after the turbo shouldn't affect boost. so additionally I'm going to try pulling the intercooler and reinstalling it to make sure everything is tight... nothing else has been touched.


unfortunately the AP doesnt log MAF. I'm still new to a lot of this though. What numbers should I be looking for with MAF?

Thanks!

[kpnorton]

Originally Posted by Jas0n

cobb stage 2 1.04 Off the shelf map... 16.4 seems low as it should be around 18 to 19 i believe for a Stage 2 car. To be honest i've never used to AP to monitor boost until now.. although I do have the stock boost guage which i could have sworn would show shomewhere around 0.125 mPA, (18 psi) maybe about a month ago... I do hear a whistle noise when letting off the gas while boosting, is this normal or indication of a leak?

i've been reading around the forum though and it looks like an exhaust leak after the turbo shouldn't affect boost. so additionally I'm going to try pulling the intercooler and reinstalling it to make sure everything is tight... nothing else has been touched.


unfortunately the AP doesnt log MAF. I'm still new to a lot of this though. What numbers should I be looking for with MAF?

Thanks!

the exhaust leak at the DP-cat-back connection shouldn't affect peak boost, though the disturbace in airflow might make a little extra backpressure. probably negligable though.

not sure about a whistle noise, but a "wooshing" sound is normal when letting off the throttle after being in boost (ex: shifting at 6000 prm off of WOT). this is the bypass valve, and it is especially audible if you have an aftermarket intake or the GP Moto Silencer Delete Elbow.

just a guess, and this is again not based on personal experience with Cobb maps....if you recently reset the ECU or reflashed a map, the ECU may require a few cycles to learn WGDC (wastegate duty cycle) in order to narrow in on target boost.

you might also check the vacuum lines going into the turbo wastegate actuator and boost control solenoid.

peak MAF on a Cobb stg 2 should be ~245-265 g/s depending on the weather, exact mods, etc... I have not run the Cobb map, so this estimate is not based on personal experience. MAF is sort of a measure of the engine's overall health, although it will fluctuate some based on weather, fuel, etc...

[Jas0n]

guys suppose i were to by a flat gasket and try it on my setup, anyone know what size i should go with?

[Jas0n]

just an update:

We jacked the car up and removed the catback. It turns out the SPT catback was not lining up with the COBB downpipe properly, leaving a very small gap at the top (producing a leak). We cut the flange at the top of the pipe and knocked it back a quarter of an inch with a hammer, then rewelded it. The pipe then fit perfectly with the donut on the downpipe... all is well, no more leak!

As for my boost issues I said the hell with it and got the car protuned (thanks to Paul and Andy at Neetronics). It's now maxing at about 19.5 psi and WOW what a difference over the Cobb 1.04 OTS maps. I don't know why I didn't do this sooner, it's a whole new beast.

The only thing that worries me is i can still hear a distinct whistle noise in addition to the normal WOOSSHH from the turbo. I have no idea what's making that noise, and it only appears while under boost. All pipes and hoses appear good and tight and I'm also holding boost just fine. The tuners didnt mention anything about it when i picked up the car so I'm assuming its not a big deal... could it just a be a noisy turbo? any ideas?