going no cat
 

Ive got a 1994 FD

Koyo N Flo:blush:
65 degree C Thermostat:blush:
185 degree F Fan Switch:blush:
Defi Boost Guage
Efini Y-Pipe
SS Resonated MId pipe
HKS carbon TI exhuast
and ss Down Pipe
also am going to add two manual boost controllers.

NOW ON TO THE QEUSTION...

Can i lets say install this exhuast system which is 3" all the way through with the stock ecu? also do i need to put an o2 sensor in the DP or WideBand? And if i go WideBand does this mean i need a Standalone???:scratch:

*The short answer is no.
*The longer answer is that the stock turbos have a relatively small wastegate. Opening up the exhaust and leaving too little back pressure can cause that wastegate to be overwhelmed. That will cause boost CREEP, which can cause a lean condition which can cost you an engine. Know that your boost controllers will only control boost SPIKE, which isn't the same thing. They do nothing for CREEP.
*RE: the lower temp thermostat, I'm personally not a fan. The stock OEM t-stat is fine for a street car. Running that low of a t-stat on cool days could actually make the engine run too cool, reducing efficiency. Run as much distilled water to coolant as you can get away with in MI and change it at least every two years.
*Not sure about what fan switch you're referring too. Many of us do replace the stock fan thermoswitch with a S5 FC thermoswitch. That lowers the threshold temperature to turn the fans on from 105 C. (220 F.) to 95 C. (203 F.) and adds some safety margin.
*Yes, you need to replace the O2 sensor into the downpipe. You don't need a wideband but do need the O2 sensor on the stock ECU. I recommend a new OEM downpipe gasket. They're kind a pricey, but you don't want to do the job twice because of a leak.

There are some catbacks that are restrictive enough to prevent creep (RB), the HKS is not one of them. The wastegate will need to be ported.

When eliminating the cat, you are also going to disable the smog pump since the split air pipe will have nothing to dump into. This gets into an area where the stock ecu thinks the car is running too rich, since it is not seeing the air from the pump.

The PFC will control boost, no need for twin boost controller valves. It can also control the fan temps. A wideband is a requirement if you are doing your own tuning. The water temp correction factors can be tuned if the car is running too cold. Nothing can be done on the stock ECU.

If you want to keep the stock ecu for some reason, just leave the main cat on the car. There is also the option of a high flow cat.

Good point on the hi-flow cat. But if you do get one, stay with a track record of dealing with the higher exhaust heat of the rotary. I like BONEZ.

Another point is that for a street car, going with no cat with that exhaust will make the car stupid loud and it will stink like road kill marinated in rotten eggs.

Thanks for all your guys' help. If i get a hi flow cat can i keep the ecu and should i still port my wastegate and delete the air pump thankyou in advanced🙏👍👍👍

The air pump goes to the cat. If you delete the cat, you delete the air pump. There is a group of local guys here in Detroit. Michigan Rotary Club - Index

Registered thanks for the info. And the recomendation Show off

You can keep the stock ECU and boost creep will not be an issue with a hi-flow cat. So porting the waste-gate is NOT necessary. I drove my car for years in that configuration.

Im glad to hear im keeping my stock ecu i dont have 700+$$ to fork over for a decent standalone. And for your earlier post blue my car is strictly a summer car i dont drive in cold weather this is why i have the tstat and fan switch from pettit (185)....

are you having issues with boost creep?

I just got a pfc i hope it solve issues related to boost im also in the middle of porting my wastegate to 1.24"

94 FD + 3"DP,MP+HKS Ti + EF Y + 185F FANSWTCH + 65C T STAT + KOYO + 18X9.5f/10.5r +30/+22 +2 BOOSTCONTROLER +BMPSTR + Ynk COILOVR + SOON PFC IMA ROTARD!!!

For creep the porting will help. PFC will not.