Hey guys...

Through a twist of fate, I may have found a cool way to get a handle on the BOOST CREEP we all face with out s4's and to a lesser extent S5's...

Because I'm a cheap Bastard... I swapped the Racing Beat catback from my 89 N/A to my 88 TII before I sold the N/A... the guys at racing beat said that the only difference between the two is that the N/A Catback uses smaller diameter piping inside the muffler cans, but it uses the same Y pipe. So I figured, what the hell, why dump another 570 bucks on a cat-back for a little bit more flow...

It should also be noted that my wastegate is still stock

I then added a Racing Beat Downpipe and Presilencer to the TII, and one of the FCD's I make...

Guess What...

As expected, My boost regularly goes over 8 Lbs and without the FCD, I hit fuel cut at the track on every pass.... However... with the FCD on.... my boost hits between 9 and 9&1/2lbs and I've never seen it go any higher....., even on long pulls in 4th gear uphill on the highway (yeah I know, thats WAY past the speed limit here in PA!!!!), it stays just above 9 LBS.

The Exhaust tone when you're in town is suprisiningly quiet, the cops don't bother me, however, when you mash the pedal, she roars pretty good and lets whoever's beside (and fading to the rear) know whats up!!!


I'd be interested hearing if anybody has tried this before, and if you think its a good idea, of if you think I'm full of sh*&t!!!

 

Hey dude... congrats on finding a way to "battle it", but you're killing performance by using smaller diameter piping. With a dual system, it tends to matter very little because there are two outlets as opposed to one. And its better to have resistance at the end of the exhaust than at the downpipe... Well... its even better to have no resistance at all lol

Anyways, stick a downpipe/presilencer on and see how that goes.

Good luck
-Ross

 

All you're doing is restricting the exhaust so the stock wastegate is once again able to handle the flow. Nothing new here, as that's exactly what the stock system does.

 

Actually I think its well done...You have done a good job with "your setup"...
When I do my mods, I do a custom exhaust and go with a 2.5" DP & exhaust to keep a handle on boost...9-10 PSI is fine for me...The lightened 87-88 T2's can fly pretty well p ushing that kinda boost! Its a good way for people to go who haven't upgraded the fuel mods...Stay safe, don't run lean...

 

9lbs with a 2.5" exhuast is nothing special...

I was only getting 10 with my fulll 3"

 

if it's less than one bar, it doesn't matter to me

porting the wastegate is easy, though.

 

damn s5 turbo. I have my s4 wastegate ported and backcut with a full 3'' exhuast/intake and my boost looks like this:

1st - 7 pounds
2nd - 10 pounds
3rd - 11
4th - creeps to nearly 13
5th - 12

this is with maybe 70 degree temps around midnight. I can't imagine what winter will bring. I might do the exhuast valve swap for the stock flap, but I think I might as well try to snag a s5.

 

Well, since i originally posted this,,, i've done some more testing, added a walbro and re-set my safc... I'm now Stable at 11 psi and 11.9 on the lambda under boost up till about 6.5K..

One guy talked about restricting with the N/A exhaust.. lemme tell ya, I've had the R/B downpipe and presilencer on the whole time.. so just for ***** and grins I put the TII R/B catback on... instead of the N/A, the only difference I saw was that the TII catback took away a bit off the low end, and creeped a bit more.. i didn't notice any power difference, it was just harder to tune...

If you've done a turbo ugrade, I guess you might see a difference in the two, but for the stock turbos.. I'll stick with the N/A catback until I do a complete teardown, port job, rebuild., turbo upgrade and haltech addition over the winter.. Its just less squirrelly!!!

I thought about porting the stock wastegate and then said the hell with it... If I'm going to rip her apart this winter anyway.. I'm just gonna ditch the stock turbo system all together!