It's as the title says...
I have a NA S4 that I just bought running/driving for a $1500 today & I have a n341 (J-Spec Turbo ECU)
I'd like to know if I turbo'd the car would it be plausible to use the ecu & it work...

I can't see why it wouldn't also that recommended 11-ish PSI max on OEM ECU does turbo size matter?
Also assume I'm on 550cc OEM T2 Injector to match the ECU.... Unless I can go bigger (I'm assuming not)????
Fuel pump is an Aero motive LP340

 

It would start and run but it probably wouldn't be safe.

The stock Turbo ECU is tuned around a lower compression ratio than the NA engine. It also has a very rudimentary knock sensor system, meanwhile the NA engine has neither the knock sensor nor a place to install it.

This means the ECU is A. Expecting to have a larger margin of error before detonation occurs (fatal to the engine) and B. Has no idea if detonation is occuring, or any ability to deal with it. The stock ECU is non-tunable and does not have any learning functions.

Larger injectors may help the issue but just swapping to larger injectors alone is a very crude solution as you'll still have no tuning ability. You also need a way to tune them to do this right.

Now if you add a piggyback solution like wideband and SAFC you might be able to get away with it, but then you still have no control over ignition timing. So then you really want an Rtek or something like an eManage (don't). Rteks are no longer produced, and people have had issues getting eManage to work reliably with our engines.

So then after that long slippery slope you end up at the best solution, which is a full standalone ECU. It isn't cheap, but it will be the best tool for the job and give you the most ability to do this safely.

I'm sure people have found creative ways to get away with less comprehensive engine control, but at this point parts for these engines are getting tough enough to find that it's hard to justify trying to save the $1000-1500 for an entry level standalone only to spend $1200-3000 on rebuild parts.

Just my $0.02 as someone who has been slowly accumulating the parts to do what you're trying to do.

Good luck, and no matter what you end up doing, remember to post a build thread

 

B341 is not a Japan-spec ECU, those are N318/N319. N341 is a European-spec S4T2 ECU. N323 is the Euro-spec S4NA ECU which has a distributor instead of the CAS.

 

Max boost on that ecu is really dictated by the boost pressure sensor. Stock boost pressure sensor will read up to 1 bar. You might be mentioning the 11 psi being the maximum boost rating of a stock turbo before it becomes inefficient.

You’ll need a wideband no matter what. For a budget, Safc will let you adjust fuel maps, I wired my load pickup into the boost pressure sensor.

I can’t comment on the timing while using that ecu since it’s for 8.5:1 instead of your 9:1, but it’s 2021 and I’d think water injection may be a solution.

 

9.4:1 for S4 NA. I'd forgotten about water injection, that might work for OP.

 

Thanks alot for all the information guys it's very much appreciated.. Not to mention you guys said alot of workarounds i'd thought of... I might end up buy a Elite 550 in the end as alot of other stuff isn't supported

 

Even if you made it work(which should be possible) it is a primative 8bit ECU, to run that ECU you would need accompanying MAP and VAF sensors as they are different than the N/A parts. If youre going to go turbo you would want a larger fuel pump to go with those injectors(and really a fuel pump rewire is a VERY good idea. When i first got my TurboII i picked up an RTek 2.0 as the car already had an exhaust on it, the rtek allowed me to get rid of the boost cut. I tossed in a pair of 885cc injectors and with no corrections having the full exhaust and intake it really ran just fine. The secondary injectors only come on in boost over 3700rpms. If youre N/A and thus almost 1 point higher compression having the extra fuel of something like 725cc secondaries arent going to hurt(and really i would suggest it).