boost creep
 

Hi All,
I'm currently having the following mods installed on my 93 FD, and I understand I may need to worry about boost creep.
1. GReddy FMIC
2. GReddy Dual Air Intake
3. DP
4. Midpipe
5. Tanabe Super Medallion Hyper Spec Cat-Back
6. AEM EMS
7. Profec B Spec II
With these mods, I hear creep will be an issue. The car will be a daily driver, mainly highways. I want to try to avoid porting/upgrading the wastegate, because it sounds like a pain. Should I put the stock cat back on? Or should I get a high flow cat? I was looking at the N-Tech high flow cat, which says it has 96% of the flow of an open pipe. I don't see how this can reduce creep if it flows almost like a midpipe.
Thanks,
Tony

Why you say porting a WS sounds like a pain?
I think its necessary to port the WS when you get a MP. High flow cat is not cheap and its power cannot compare to the MP.

Below is something from Rob Robinette's site


Mid-pipe - Replaces the stock main catalytic converter with a three inch pipe. The car will be very loud with a down-pipe, mid-pipe and cat-back. If you don't have one yet you'll definitely need a fuel computer. A mid-pipe is normally an off road (race) only modification, your car will not pass an emission sniff test or visual inspection. If you add a mid-pipe you would normally want to remove the air pump too. With an open intake and complete exhaust on a well running car, boost creep will occur. Boost creep happens when the stock wastegate is overwhelmed and can't dump enough exhaust to keep the boost level from creeping too high. I had to replace my mid-pipe with a high-flow catalytic converter so I could control my boost. Others have had their waste gate enlarged but this requires removal of the turbos and exhaust manifold (very serious work). I only recommend this mod for those serious racers that want the extra power and are willing to modify their wastegate to handle the extra exhaust flow. If you try to run an open intake and exhaust without an upgraded wastegate you're asking for over-boost and engine damage.

Sorry dude, if you want to modify, that requires you to put some work into it.

No free lunch. Pull the turbos, modify the wastegate.

Try making a stainless steel restrictor plate to replace a gasket either before or after the midpipe. Start off with a 2 1/4" hole and go smaller if your boost is still elevated or creeping. An easier alternative to pulling the turbos to port the wastegate and will flow better than a cat.

antcee,

Some cars run into boost creep, some don't. If you want to keep the midpipe, porting the wastegate is the best option. While it might be a pain, it can save your engine.

As far as hi-flo cats, they typically have enough restriction to keep boost creep from happening. However, as mentioned, they are not cheap.

Thanks Mahjik,
The N-Tech high-flow is $340 which i'm okay with. It may also give me less of an issue when I have to have it smogged. How much was the one you have? Would you recommend I get that one instead?
Tony

I haven't done any testing of hi-flo cats myself, but another member posted some info a while back:

I haven't heard of any problems with the N-Tech Hi-Flo cat. Also, Gotham Racing is offering a hi-flo that a few members have purchased recently. However, they are a little too new to have any good/bad results yet.

Here is the link to the Bonez Hi-Flo:

http://www.rx7.com/cgi-local/3catalog.cgi?cat=4&part=2

It is probably the most expensive of the bunch....

Thanks again,
I just ordered the Bonez Hi-flo.
Tony