hey fellas, just recently picked up a FD, the cat was removed but the stock pre-cat is still in place and there is an old mazda speed muffler on there, hate the sound of it because a part of the weld on it broke and it rattles sometimes. i was told to replace the pre-cat before the mid-pipe? my hks hi-power exhaust and downpipe is in the box still so i will have a full 3" exhaust. my question is will i run too lean to cause problems? will i be okay with this setup? car is mostly stock except for aftermarket air filters, exhaust, no cat. i do have a apexi afc neo too but i do plan on upgrading to a pfc fairly soon. there is also a walboro 255 lph pump installed, thanks!

 

from what I understand the pre-cat creates a lot of heat under the hood of our cars(destroys are engines harness since its right next to it) and most people get rid of that first but since you have full 3 inch you will probably see an increase in boost which is very bad especially with the stock ecu. I would leave it there until A: you get a cat/hi-flow cat or at least a power fc.

As far as I understand we have a 3 mod rule which depending on the mods will increase boost and the stock ecu I personally wouldnt feel safe past 10#'s.

*I'm a noob so do some more research lol.

 

If you port your wastegate you can run full exhaust with no problems on the stock ECU

 

I wouldn't go that far. Even with a ported waste gate, the stock actuator will have trouble keeping boost at stock levels with a full exhaust. You'd need an aftermarket boost controller with large enough actuators to handle the increased flow. I believe the old style Greddy Profec is the BC of choice for most.

To run high boost levels, you'll have to upgrade the injectors along with the ECU.

The Apexi AFC won't do crap for you on this car. Upgrade to a PFC as soon as you can, at which point you can run an open exhaust.

 

+1^ I have intake, full 3 inch exhaust with resonated midpipe, greddy smic, ported wastgates, streetport and pfc and am seeing boost creep hopefully it is because of I need a boost controller. I am seeing 1-2 psi boost creep btw.

 

Sorry, I meant to add that it is okay as long as it stays at 10 psi. Some get lucky, and some do not. With my mods, I am running a bit rich at 10 psi and WOT so I assume it would be safe (for my car) as long as boost levels did not exceed the stock amount.

Randy

 

wait hold on, i posted a thread about the mid pipe and everyone on there was telling me the i can blow my engine.....i have a power FC, greddy front mount with pipes, down pipe, exhaust, fuel pump, radiator pulleies ect ect..... so are you guys on here syaing that I CAN put a mid pipe on and be fine with my stock twins?

 

yeah you can add a mid pipe and be fine as long as you can control your boost which generally starts to spike when your exhaust has no restrictions.

 

Did you neglect to mention your mods in your thread? You can run a midpipe as long as you can a: control the boost, as FearNoPiston said, and b: you are tuned for the boost you're pushing. If you get a midpipe, you will need to get retuned on your PowerFC.

I'm currently running a large street ported engine, non-sequential twins, 3" downpipe, 3" resonated midpipe, 3.75" cat-back, 3" intakes, Greddy 2-row IC, 850cc primary injectors, 1580cc secondary injectors, dual Walbro 255lph pumps and a PowerFC to tie it all together.

 

Thanks guys, everything was really helpful. So from what I gathered from the info, I shouldn't install the HKS hi-power + downpipe UNTIL i get a pfc + boost controller? Otherwise I would be getting boost creeps? Will I be okay with the mid-pipe in there right now with a restricted exhaust?

 

yes you will most likely get boost creep if you put it on now and I wouldnt do many mods with the stock ecu. You could potentially get boost creep with a boost controller and a pfc porting your turbos wastegates can help. Basically the easiest way of doing this is put your down pipe on get a high flow cat and a pfc and you should be fine and shouldnt have to worry about boost creep.