What AFRs for turbo'd NA?
 

I am currently finishing up my turbo'd na project and will begin tuning it via SAFC neo, and i'm wondering what AFRs to tune to (the neo will be wired to take a MAP signal instead of TPS).

From what I've read in other threads (for T2's)

light throttle ~14 - ~ 15

medium throttle ~13

High throttle/high boost (8-10psi) ~12 - ~13

Since this car will be high compression (with no timing control until I get a standalone) I'm thinking the "high throttle" might need to be closer to 12. If anyone has some datalogs of AFRs that they could post just so I can get an I dea of what to look for that would be awesome.

List of important mods...

550cc (pri and sec)
t2 I/C front mounted
t2 turbo
2.5" DP

Any input/constructive criticism is appreciated

Thanks

EDIT: I know some guys have done this on stock timing but would it be a good idea to rotate the CAS back a bit (if so how much?) just as a safety measure? I know I would loose a little low end, but rather that tan blow the motor.

You need to address the timing control issues as this is very important with hi compression turbos. It's not just about A/R ratio that you need to be worrying about.

I'm not talking about turbo A/R (Area/Radius), i mean wideband AFR (Air Fuel Ratio).

I know the stock timing is not ideal (or even recommended) but it can work, and like I said I can rotate the CAS back a bit to retard the timing (I need to know how much though...). Others have succesfully used stock timing on a turbo'd na (aaron cake).

From what I've read on these forums, stock timing isn't really an issue until about 8psi and up, that's when it gets dangerous. My plan was to make sure there was plenty of fuel at that point and if it was a serious issue, rotate the CAS back a bit (or just limit boost to 8 psi for now).

But my original question still remains what AFRs should I be looking for accross the RPM range?

Honestly i would tune them around 11.5 or less on WOT, especially with high compression. I would also retard the timing some. What are you using for fuel control? Your best investment would be a standalone for sure. My car ran 10x better with just the base map than with my safc. Also im not for sure but didnt aaron cake have a standalone in his????

get the car on a steady state capable dyno and watch what the car likes best! the high compression is more going to reduce how much boost you can run on pump gas... not what afr's it wants.

Until I get a standalone I'm not boosting past 10lbs

I believe he ran an SAFC with his "phase 1" and then a mircrotech? with the big turbo phase 2.

How much should I rotate the CAS back?

There is no set amount to retard the timing depends on the engine and your setup. I wouldn't be pushing 10 psi on NA rotors though, maybe 5-6 at most with stock ecu. I think your asking for it without a standalone no matter what others have gotten away with. One bad tank and you could be rebuilding.

Stock injectors? Stock ECU? On a high compression turbo car? Come on man. Why are you wasting your time with such a risky setup? Get 720 secondarys (stock injectors is just asking for it). Sell the AFC Neo, it's no different from an SAFC1 except a few visual gimmicks and a little higher resolution. Then use that to get an Rtek 2.1 , which lets you edit your stock fuel maps and datalog engine sensors, as well as control timing. People have made well over 300 to the wheels on the Rtek, and it is a good compromise between the SAFC and the time and expense of a standalone.

I actually have an s4 NA Rtek 2.0 but I was told it won't work for turbocharging because it uses a MAP vs RPM graph and the stock na MAP sensor only goes from -14.7 to 0psi which would give no control of fuel maps in boost...so I bought the SAFC.

I was going to sell the Rtek, but maybe it's worth keeping just for the ability to control the timing maps (and a few other nice features)?

um yeah thats kinda what its for... the safc doesnt control fuel maps in boost either.

have you read the instructions for the rtek?

Umm sure it does, especially since i'd wire the TPS signal to a 2 BAR MAP sensor, therfore giving me a RPM vs MAP (MAP that goes to 15psi and not 0)graph to map the fuel.

I have gone over them once, yes, but since you mentioned it i read over them again. I found out the the timing table is an RPM vs LOAD or BOOST (i guess i can select which one somewhere). This got me thinking...if i set the retard for the ignition @ 0psi for the value I would like at 10psi, as soon as the car entered boost the ignition would retard as though it was at 10 psi.

Maybe not the best for performance but would definately be safe, no?