Full exhaust with Pettit ECU
 

question , if it posible to run full exhaust with this Pettit Racing ECU ? JDM downpipe, mid pipe and PFS cat back in a stock FD (37k miles) or do i need the stock cat to control boost creep .Im pretty sure I do need the stock cat.

The pettit ecu should allow you to run 12-13 psi safely. If your boost goes higher, then you will need something to control it.

keep the stock cat, it'll keep the engine together

I am running this setup, boost is steady at 12psi .....
Stock airbox with bottom cut out.

No problems ... shoot flames.

thanks for the replies, i installed the stock cat . I bought a SMIC looks like the ARC one . So i installed the SMIC , Efini Y pipe , PFS cat back and JDM downpipe with pettit ECU . Car is hitting fuel cut at 14.5 Boost. So i don't know if I should install the Stock intercooler back. Right now it has stock intake and stock cat and car has 37k miles. https://cimg1.ibsrv.net/gimg/www.rx7...86842acbfe.jpg
https://cimg2.ibsrv.net/gimg/www.rx7...79a20ae03a.jpg

That IC doesn't look to be a huge upgrade size-wise. Surprised you're seeing so much boost with the stock main cat in place, actually. If anything removing the Efini Y-pipe should help lower boost, that's been proven to add a solid pound or so of boost with no other changes made.

Consider moving to an Apex'i Power FC. Great proven ecu and along with a boost controller there's no reason you can't limit your boost a bit, and/or get the car tuned so you can safely run 1 bar boost. Many other benefits like the ability to monitor boost, water temp, battery voltage, fuel injector duty. Makes things like adjusting your TPS a breeze, just to name a few.

Of course, the twins won't last forever at that level. Then there's the consideration of water injection to keep things mega-safe. It never ends :rofl:

there's always the old "Drill out the restricter pills" method if you don't want to go down the Power FC rabbit hole. The other thing to consider is going with a Racing Beat catback exhaust, as it will be more restrictive.

On my '95 I have JDM downpipe, stock cat, RB catback, drop in filter, stock intercooler. Boost is about 11psi (was similar with stock catback and just drop in filter only) and tapers down to 8 at redline.

Remember, the pressure ratio across the turbo compressor side is compressor inlet pressure (measured after the restriction of the airbox) compared to the compressor outlet pressure, not the manifold pressure.

https://www.rx7club.com/attachment.p...1&d=1504447562

High intake restriction pushes the turbo harder. It increases the pressure ratio.
More boost pushes the turbo harder. It increases the pressure ratio.
All that moves you up along the Y axis of your compressor map

Carrying that boost at higher rpm increases the mass flow, moving you to the right on the compressor map. Therefore:

the higher boost you run at redline or right before the secondary turbo comes online, the harder you are pushing the turbos because the compressor speed is highest there. So if you are a 12psi at redline, with the stock airbox making it suck air through a straw... that's pushing the turbos. The SMIC and Y pipe is probably offsetting that a little bit, but still, you are reducing the life of the turbos and probably running them near the choke line.

So, how high do you want the boost to be? And do you want to go down the road of boost tuning, engine tuning, etc, or do you want to keep the drop in nature of a stock or chipped ECU?

car looks good btw

thanks for help brother , I don't really want to mess with the apex or any aftermarket ECU yet , I'm heading to Germany next year for my last duty station (will retired from the Army year 2021) and i'm planning on taking the car to Germany once I get back to the states hopefully FL, I probably do more to it . But i'm really happy the way is running now stock. I'm going to removed Y Pipe. With the stock ECU car was running 12 PSI (with same mods except IC) so i'm hoping if i removed Y pipe and put the stock ECU to be in the 11 PSI.

Thanks for the info . I would like to keep like yours 11 PSI and 8 PSI at the red line. I'm not looking into going aftermarket ECU yet.

Easier, simpler, and better to get a boost controller.

yeah i'm looking into that , today i put back the stock ECU and Cat back ( car is way to quiet )so the only aftermarket part is the SMIC , i should not see anything higher than 11 PSI just with the JDM downpipe , Efini Y Pipe and IC , Tomorrow i'm going to test it in the highway .

Stock catback is quiet compared to aftermarket, but compared to other cars' stock exhausts it's not that quiet. My FD with stock exhaust was louder than my stock Ecoboost Mustang. Get on the highway in 5th gear with Windows up, blower speed at medium or less, and the audio at lower volume and you will hear it drone a bit as you accelerate. Go WOT with the windows open and you will hear it. It's not an S class Mercedes.

The biggest problem with the stock catback though is that it rusts.

Keep in mind that any aftermarket boost controller you get will vary with the weather, and needs to be tuned in consideration of the turbo transition.

i installed the stock catback and ECU car is quiet , haven't test drive it yet (too many coronas) tomorrow i will drive it in the highway . But i will be looking into the RB catback .Im in WA state right now is hot but it will start getting a little bit cold soon.

update, car has jdm downpipe, efini y pipe and the SMIC , with stock cat back stock ecu . Surprisingly i guess the SMIC makes the turbo sounds better cause it sounds good. In the highway 3rd gear pull boost went to 11 PSI and back down 8 PSI. 2nd gear pull went to 12 PSI.

sounds about right. I'd call that safe.

As I pointed out in another thread, https://www.rx7club.com/3rd-generati...n-myth-934461/


Mazda's own technical information shows boost rising as high as 12psi and tapering down to 7-8 on a stock car.

Easiest thing to do is install a 2.5" restrictor plate between the downpipe and midpipe. Without it most likely you will have trouble controlling boost. 12-13 lbs is about the safe limit of the stock fuel system. Yes some have run more, but it leaves no safety margin. That being said, there is little benefit removing the cat at your power level.

good info thanks

so i should be able to put the cat back again it should not change that much but if it does then i know I will need the RB one

The RB is going to be quieter and more restrictive. The actual difference in boost between all 3 catbacks in question is something you will have to test for yourself.

I just went thru testing this 2 weeks ago.
Pettit ECU, cut intake box, hks dp, SuperU SMIC, bonez mp, RB catback and two 2.5 inch gaskets between mp/RB catback and the joint RB pipe and muffler.

Got 10-13-12-10 boost pattern. However, because the turbulence in the exhaust flow, spool up was bad, lots of popping and I didn't like how the engine would hang revs.

Took the 2.5 inch gaskets out and replaced with 3inch, everything was smoothed out.

Decel was good.
Boost pattern is now 10-13-12.

I think this is the sweet spot.

My SuperU is probably helping me control boost. Your ARC is very free flowing in comparison.

I decided to leave mine stock for now, is starting to get kind of cold in WA , I don't want to risk it blowing my engine . I be shipping the car to Germany around april.