Like the title says I need some advice. I am new, and have searched, and gotten a lot of good advice. Now I know this question, or a variation of this question has been asked, but after reading through it, I didn't get a full, and accurate answer, thus the reason I am posting now. Again, I am new, so I am hoping I dont get flamed...Thanks in advanced. Here we go;

I have a stock 94 FD. I just purchased a PFC, DP, MP, and HSK cat back. My question is, do I put the mid pipe on? (yes I bought it, but got it as a package with the DP). People have said no, some have said yes...I just dont know.

I want to run stock boost levels, or slightly higher (11-12psi?) What advice do you have if any...

Thanks!

 

your stock midpipe(cat) helps control boost levels. If you replace it with a straight pipe, I suggest porting your wastegate and getting a boost controller. These 2 mods will help to control boost after removing the stock midpipe

 

No. A mid-pipe often causes boost CREEP. Creep happens when too much exhaust overwhelms the wastegate. That happens when you have too little back-pressure...ala mid-pipe w/a DP and aftermarket cat-back. No cat will also make your eyes water and smell up the neighborhood.

And don't get Boost CREEP confused with Boost SPIKE. SPIKE is from too much intake flow and is typically dealt with by a boost controller. CREEP can NOT be controlled with a boost controller...only from porting the wastegate. Wastegates on the stock twins are internal and not easily accessed for porting, so IMO it's not worth it. Especially since your trying to stay at stock or near stock levels.

 

Also, just for future reference......adding searchable terms to your thread title (like "Midpipe" or "Mid-pipe") might help the next guy searching for answers to the same question.

 

I run the stock twins with a midpipe, a ported WG and a profec controller. I have zero creep issues but granted each application is different.

I think it is completely worth it, or you could just go with a high flow cat and get the best of both worlds

 

as surfmon said get a boost controller so you can set your boost, and control spikes. Make sure you port the wastegate so you don't get creep from your MP.

You need to get that PFC tuned before you WOT BTW. While you are at it get an IC so you can do everything at once. and not have to worry about retuning nor anything.

 

And you shouldn't....you ported the wastegate. And as I said, a BC is for spike. Does nothing for creep caused by a midpipe.

You and Montego are bringing up BCs, ICs and tuning when he's asking about whether or not he should install a midpipe. He's new. Why confuse the issue?

 

He is new but not an idiot. Im sure he can figure it out. as with this new info he will go back and research a little more and make his own decisions.

A BC is necessary given that he has a DP and CB. So it needs to be brought up. And at some point he will want an IC. So why pay for a retune? Do it once do it right and enjoy.

 

I like that one...lol. Thanks for the advice so far guys. All the advice is helping so far...Now I dont want to sound like one of those people who say the want the "cheap" way, but I am on a budget...I just bought all of this stuff, and have to buy some gauges (boost, egt, water temp wb afr)...so I dont really want to do anything else this year...however this is my first FD, and you all have been doing this a lot longer, so any advice is truly helpful.

And newbie question...what difference will I get with a hi-flow cat vs. a mid pipe vs. stock cat?

 

noticeable difference in power between the stock cat and either a MP or Highflow cat

Its much louder without a cat though and depending on your tolerance, it can get annoying loud.

Lots of people run a resonated MP which gives you the flow of a midpipe, but has a built in resonator to tone it down. I run one and the sound is phenomenal.

t

 

but an aggressively ported WG does, and that is the main issue that needs addressing.....which is why i recommend porting the hell out of your WG

 

I'm with Sgtblue on this. Don't install the mid pipe. Keep your cat.

Running w/o the cat leads to problems with boost control. Especially up there in Canada where the air is cooler. Plus running w/o a cat smells terribly and is LOUD. You will make a little more power but you now risk blowing the motor if your boost creeps - which it will in colder weather. "Porting the wastegate" requires that the turbos be removed so its not like its an easy thing to do.

I think the stock fuel system is sufficient for 11-12 PSI of boost.


Installation Note - It sounds like you ordered an ebay downpipe - midpipe combo. The bolt holes at the flange where the DP meets the cat are often smaller than the studs on the stock cat so you might need to enlarge them. Best to enlarge those holes while the downpipe is off the car.

 

I actually bought the DP and MP and PFC from someone here on the forum...it was just a good deal, so I couldn't pass it up, even if I am not putting the MP on anytime soon.

 

Install the midpipe, remove the boost restrictor pills and the car will be safer and just as fast if not faster on 8lbs than it would be on 10lbs with the stock cat installed and the car running on the edge of safey. What do I know, I have only owned about 50 fds with the exact setup you were describing expect most were on the stock ecu and no the PFC.

 

boosh

 

Sounds like you're looking for a simple solution in controlling your boost? Installing the DP and MP will diffinately increase the boost beyond the 10 psi limit on a stock twins!

The most simple and cheapest solution is to add restrictor plates between the DP and MP until it gets within the level you want. Then, in the future, when things become more apparent, you can opt for the other modifications.

 

Agreed...I think. That's why I mentioned it when I posted virtually at the same time as you. But what exactly is "an agressively ported" wastegate? I mean, why would someone go to all the trouble but only port it say...half-way? Really, either you port it or don't.
A BC comes in when he adds an intake, efini 'Y', or IC, but not exhaust mods. Nothing to do with whether or not to add a midpipe. A BC can deal with Spike from the intake side, not Creep from the exhaust side. So why is a BC necessary for a DP and CB? The ONLY reason I brought up a BC was to draw attention to the differences. Never insinuated that he was an idiot. Hopefully he knows that and does figure it out. Those DP and MP "package deals" have probably made alot of money for rebuilders over the years.

 

I experienced boost spikes when I added my DP/MP with a stock INTAKE and STOCK IC. I am not alone in this. Does not seem out of this world since turbos spin off the exhaust. Yes I added a midpipe on a stock ECU and ran for years without a worry so yes he can add a MP he just needs to be able to control his boost and make sure that PFC is tuned. But whatever what do I know I only owned this car for 11 years.

 

10 psi is not the limit on the stock twins. But it is the limit on a stock ECU.

 

You have to consider your location though. You are in San Diego where it 50 degrees F in winter is considered cold. He is on Toronto, Canada where the air is a lot cooler.

Controlling boost in thin, cool air of Canada where ambient temps vary by a large range throughout the year is a lot different than controlling boost in San Diego. When I lived in the NorthEast, my car would creep and spike a lot more in the winter when I had a mid pipe and a boost controller and a well tuned PFC. Adding a cat made boost control a reality.

 

I run boost levels from 11-12 with the stock cat. My car was tuned for 294 rwhp with the mods below. I did not need the extra power or noise of a midpipe.
No aftermarket boost controller or driving hard on cold nights.

 

True I've never been in the teens so maybe thats the key... From my stand point I never had any issues, winters here can and have gotten in 30's. Nevermind our locals mountains where they get into the 20's. In those situations all I ever did was was dial down the boost and enjoyed the cold intake temps.

 

An alternate way of making a safety net against boost creep is through the PFC, by pulling ignition to zero at - say - 13 psi or any other boost limit you feel comfortable with, depending on your fuel system. This is what I do because porting the wastegate is not allowed in my SCCA class.

- Sandro

 

Just for my knowledge. Even assuming that you cap the bleeding line from the wastegate actuator, if you stay at full throttle long enough, couldn't an open exhaust eventually overcome a stock non-ported wastegate?

- Sandro