how much boost on 93 octane? W/O any injection

[TT69CAMARO]

I have a general question for everyone. There is no right answer, I'm just gathering information. I would like to know how much boost you run on 93 octane? what your static compression ratio is, what your cubic inches are, intercooled or non intercooled, carb or fuel injection, and timing at that boost level? I'm looking for this info before water injection so I have a starting point. It would be especially nice for those to share their misfortunes by pushing the envelope too far so the rest of us wont follow in their footsteps.

For example, here's mine:
15 psi boost
8.00:1
374 ci.
intercooled
fuel injected
26 degrees timing

If we get enough info it might help all of us in the long run!

I have been invited to Hot Rod's pump gas drags in 5 weeks. I just got my car finished towards the end of last year. I havent had much time to tune it, so I'm looking for a starting point. Thanks in advance, Chris

[hotrod]

The stock Subaru WRX is a 2 liter (122 CID), four valve head, overhead cam engine, flat top piston, aluminum head. Compression ratio 8.0:1, It has a top mounted air to air intercooler, and runs about 14 psi max boost, on a recommended fuel of 91(minimum) octane. The engine runs likes more octane and runs better (and the ECU gives better igition timing on 93+ octane). This mostly effects the most knock prone rpms near torque peak. Due to the output characteristics of the turbocharger it peaks boost near 5000 rpm then tapers a couple psi towards 7200 rpm red line.

The guys making big power (and tunable ecu solutions) run around 24 -26 deg ignition advance, but the stock ECU has been know to dial in a lot of ignition advance at high rpm ( up to 30 degrees or so). It gets away with this due to the stock boost taper, but aftermarket turbos that hold boost to red line will detonate at 14 psi at these ignition advances.

This engine has a very over square bore stroke ratio (92mm x 75mm --- 3.62 inches x 2.95 inches)

Larry

[TT69CAMARO]

Thanks Hotrod, That was very informative! It must be hard to tune WRX's with everything always fluctuating?

[hotrod]

Thats true. The new highly adaptive ECU's can end up fighting the tuner if he doesn't understand how the ECU code makes decisions.

There is something to be said for the good old fashioned distributor ignitions. Set the base timing. set the rpm you have full advance and maybe retard a couple degrees in the traps. What is really interesting is a well tuned distributor ignition give up very little power to a modern EFI system at WOT.



Larry

[Roger G.]

1993' Mitsubishi 3000GT TwinTurbo

1.0 bar boost
8.00:1
2997 ccm
twin intercooled
fuel injected
timing not known for sure

1.14 bar with WIS and same amount of knock

The problem on the V6 is knock. Some engines don't knock at all others start at 0.85 bars. We haven't really found out what the differences are. Fact is that at 1 bar the IDC is 100% due to the overrich mixture the engine needs. Leaning it out results in knock. Here in Switzerland we have 95 and 98 ROZ octane gas. This is somewhat similar to 91 and 93 or so octane. Not sure about this.

My car is equipped with a MAF replacement where the restrictive Mitsu MAS is removed. A fuel controller tweakes the airflow signal for the 720cc injectors (360cc is stock). Therefore the timing is probably too much advanced under full load causing the unwanted knocking.

WIS helped to lower down the high inbtake temperatures but I haven't been successful yet in knock control. In some other threads I will report my progress to this goal. Interestingly I saw huge knock on the AWD dyno but almost noe on the roads when testing. This tells me that the IC were not able to work properly on the poorly air cooled dyno.

Today the car has two 20g sized turbos and heavily ported (I call them overported) heads installed. Discharge temperature is lower due to the higher efficiency islands the compressor works on. With this I see beter intake temperatures and can concentrate WIS for knock control.