93rx74lyfe

iTrader: (1)

Hello all, I'm tearing my hair out with boost problems but here's a little back story.

Like many with a intake/full exhaust I was experiencing some over boosting. To fix this I bought Jyros exhaust restrictor plates and installed the smallest plate(2.25in) between the mid pipe and catback. Now my turbos are completely controled by my AEM truboost ebc and everything for the most part was 10ish pounds. Now that i added a pfs smic boost is uncontrolable, and im neering 90 percent duty cycles and that has me very uncomfortable.

At first I thought the hoses to my boost controller were getting old so I replaced all of them with brand new silicone lines and the aem boost solenoid is barely two weeks old so im pretty sure I can rule that out. Just for kicks I ran the car with the boost controller off and was surprised to see I could spike to over 12 lbs on just the stock waste gate spring! So my only conclusion was maybe my exhaust plate had enlarged over the years....nope, in good shape and still 2.25 inches in diameter.

So if im thinking correctly, do I need an even smaller plate like 2in? Has anyone ever run something so small? Im sure porting the waste gates would help but that's just not an option right now. Im sorry for being so long winded but im sure you'd agree, its much easier to figure stuff out with a bunch of info. Well if any of you guys have any advice I'd really appreciate it.

-Justin

tt7hvn

iTrader: (5)

instead of going smaller, you could install another plate between the DP and MP. That would be my suggestion.

However, there is still an underlying issue that is causing your boost creep. I'm assuming your still running the stock twins. If that's the case then that's you're issue.

Also, you didn't mention what ECU you're running. I hope with a full exhaust your running something other than OEM. Otherwise, you're looking for a world of boom.

If you still have the stock side feed injectors, running those at 90% duty cycle isn't a bad thing. Some would argue it is, but I know of many that have run the stock injectors to 100%, on multiple occasions, more than once with no issue. They are a good design and are actually designed to run that way.

What size are your injectors?

What boost are you trying to maintain?

93rx74lyfe

iTrader: (1)

Yes Im still on the stock twins, also using a base map pfc, and stock inject/pump. I do have one more plate that is 2.5in that i thought about throwing in as well but I wasnt sure how that would effect things with the plates being different diameteres.

tt7hvn

iTrader: (5)

it shouldn't be an issue running different diameter plates. Although, I would be the larger plate farther upsteam; closer to the turbos.

silverTRD

iTrader: (37)

Your car is simply flowing too much air imo once you installed the ic. I'm assuming you're on a pfc with the base map for the twins, which isn't a bad map really. I ran this for a while, I even did the exhaust restricter. I was running a profec b and it was controlling boost fine, id's were fine, afrs we're fine until one day it was cool out and I detonated. I was lucky and didn't blow the motor but the cat went back in that night until I ported my waste gate which is the solution to your problem. It sounds like you know this, just get a cat, or go back to stock ic or something if you don't have the time to pull your turbos. It's not worth it man. My .02

tt7hvn

iTrader: (5)

^I should've just come to that conclusion; as it would be the easiest for him.

I need to brush up on my stock rx7 knowledge, lol

93rx74lyfe

iTrader: (1)

I know it sounds crazy but I waited over a year to get this I intercooler and would weep having to look at the crummy stock one in its place. I have considered a high flow cat but I cant lie, a straight through pipe is pretty awesome. I wonder if a slightly smaller plate might help, I just feel like going down to 2in would be a crazy squeeze.

silverTRD

iTrader: (37)

I have my old 2.25" restricter for sale for cheap if you want but to be honest its not the way to do it. Its a bandaid and to be honest its probably hurting you more than helping you power wise. I'll tell you my experience and let you be the judge...

I was running the mid pipe with restrictor on the pfc with base map and it was cool because it thru flames and all but it was actually slower overall compared to my high flow cat. I raced a buddy with an R1 one night with the mid pipe and I beat him but not by much. He had a fresh reman with a dp and that's it. I probably beat him by a car length from a dig to an eighth mile wish. I was curious so I swapped in the high flow cat the next day, raced him again that night, very similar weather and we did the same race and to my surprise I beat hime by 3 cars. Food for thought?

Its my opinion that a mid pipe is not as beneficial on a FD unless the car is tuned for it. I suppose its like anything on this car...

93rx74lyfe

iTrader: (1)

Thats crazy, im glad the hiflow worked out well for you. I have a strange story myself, i know a few local guys with all the bolt ons, tuned to 12psi, better rubber, diffs the works and my fd beats them all by a good half car with less mods. Ive driven a bunch of fds and ive honestly never seen a tt 7 pull as good as this one. The hiflow sounds likea good idea but im just worried that it might not fully solve the problem and of corse the power loss.

Prôdigy2nd

iTrader: (3)

as silvertrd stated, you need to port the Waastegate to cope with the exhuast flow, yes the Intercooler might be nice and you've waited a while, but having a running engine is much better with a stock IC then a blown engine and a nice fancy IC...

porting the wastegate is the only real solution to your issue, anything else is a band aid. I wouldnt want to blow an engine because of me not listening to people who have warned me about could happen.

J.

93rx74lyfe

iTrader: (1)

I comple agree, porting the wastegates is the proper way to do things, I just do not have that option. The restrictor plates have been proven to work on my previous setup and with many others from looking at past threads on these. I understand that on a few peoples setups even a 2.25in plate wasn't enough so they went smaller, Im just looking to see what their experiences were with going into a not so charted territory.

tt7hvn

iTrader: (5)

why is porting the wastegates not an option for you?

Since it would solve all your problems, it honestly seems like the ONLY option.

TomU

iTrader: (11)

curious, how does porting the wastegate keep boost in check?

tt7hvn

iTrader: (5)

with a full exhaust, the stock wastegates are too small to bypass enough exhaust to maintain 10psi. If you port them out, making them larger, they can then handle the amount of exhaust flow that a full exhaust provides and bypass enough exhaust to maintain 10psi.

That's why one of the suggestions was putting the stock main cat back on; to create a more restrictive exhaust. That's why he's also been using restrictor plates, to simulate the backpressure of the stock main cat.

Troclo

Well the waste gates only function is to keep the boost in check, when you install a larger IC or/and a PFC more air is pushed through the engine resulting in more exhaust gas. As the stock waste gate is pretty small it is soon unable to dump exhaust fast enough to keep the turbos from over boosting. By porting the waste gate its ability to dump exhaust gas increases thus slowing the turbos down. Putting a flange with a 50 mm hole in between the down pipe and mid pipe usually keeps boost below 0.9 bar/13 psi by creating a backpresure choking the turbos. As others state above this is not the right solution but it will work without hurting the engine or the turbos if you haunt got time to port the waste gate.

93rx74lyfe

iTrader: (1)

Yes, porting is the "right" option, but it has been documented to sometimes have other issues associated with it besides the much higher cost and actually taking the turbo off. This engine is nearing 100k so im sure ill be seeing it out of the car by winter, at which it would it would make more sence to do the poting. Im just looking for a safe fix for the time being weather that be a hiflow or a brtter plate configuration.

So what your saying is you have experience with using a smaller diameter plate (50mms)? Do you have any input on how this may effect spool characteristics or sizes that are more 10psi friendly?

93rx74lyfe

iTrader: (1)

Hey guys I have an idea, the plan is to order this 2in plate ( 2-Bolt Stainless Steel Exhaust Flanges - Vibrant Performance ). I would also pick up the right gaskets as well. My question to you guys is how would you go about this, order one 2in plate to put between the mid pipe and exhaust or 2 plates so I can sandwich the mid pipe with one after the down pipe and another before the cat back?

IRPerformance

iTrader: (41)

Port the wastegate. Everything else is a bandaid. Its really not that much work.

93rx74lyfe

iTrader: (1)

Sure, how much and whats your turn around time? You can pm me if thats better.

TomU

iTrader: (11)

I'm interested as well. I read the Rotary Resurection write up and would prefer paying somone that's done it before. The learning curve is a bitch

BLUE TII

iTrader: (9)

When I had IC, downpipe, resonated midpipe and catback (stock intake!) and MBC on WG and prespool I had to go down to a 2" reducer to stop boost creep.

I switched to an SMB "highflow" cat and no longer needed a reducer. Much less stink and noise too.

If you have your stock cat still I am sure putting 3" inlet/outlet pipes on it from a cheap ebay non-resonated midpipe will get you flowing better than the "highflow" cats on the market and stock is a metal cat- its quite durable.

Fritz Flynn

iTrader: (263)

If you must have the volume I'd go with 2.5 plate after the DP and 2.25 after the mp

Best option for a street car IMO is a stock cat with airpump. Not too loud, perfect boost and no gas smell.

Troclo

I drove my car 3000 miles with the 2inch flange between the down pipe and mid pipe. It worked just fine, spools up just the same but is restricted by the flange to creep/overboost as the flange creates back pressure preventing the turbos from over boosting. I guess you could go even smaller but why?
0.9 bar is great fun if you are not leaning out. Yes its a bandaid but if you are in a hurry its a quick fix.
Porting the waste gate is pretty easy too though, you just spray paint the flap when its closed so you can see the edge when its open, grind away but leave a few mm's for the flap to seal. Happy rotaring to all!

Fritz Flynn

iTrader: (263)

I like the flange idea

silverTRD

iTrader: (37)

Funny thing is, I'm willing to bet your car will definitely be slower if you go down to a 2" restrictor instead of a high flow cat or even a stock cat. Your top end will definitely fall off compared to your other options.

However if you are planning to pull the motor shortly, go ahead and go with the smaller restrictor temporarily.