Been doing some reading and it seems to be that the best way to work out point of Maximum Best Torque (MBT) is with a Dyno. Obviously having the flame front hit the piston at 15* ATDC will mean you'll need to adjust the timing for piston speed (revs).
Is there any way to get to MBT just by doing WOT logs without a dyno? Can you rely on KR detection as an indicator of being close to or having passed MBT?
On normal pump gas you will get knock before you reach MBT on our cars. The only time you need to worry about reaching MBT is if you use E85, methanol injection or any type of octane booster. If you are using 98 octane you can just tune until you get consistent knock in multiple logs, then remove .5-1* of timing in that rev range. So I would say it's not safe to tune for MBT without a dyno as every log you do on the street will be different and you need consistency to see when you stop making MOAR POWA
Last edited by ledfootrob; 04-05-2013 at 08:06 PM.
Thanks @ledfootrob, that approach makes sense.
I am running Cobb Stage 1 - 98. How many more degrees in the mid range and upper ranges is there to be gained from the Stage 1 OTS map on 98 octane? Wondering how much fat there is to trim (or are they fairly agressive as they are).
Also, does anyone know if running more timing puts additional pressure on the stock HPFP? My guess is no, but wanted to be sure. Certainly don't want to venture too far until i do get upgraded HPFP internals
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Tuning until you get a little knock on pump gas is the best way to maximize timing on the street. However if you have access to higher octane fuels that allow you to run past mbt before seeing KR, you will need to dyno tune to ensure you do not go past MBT. Going past MBT can actually be worse for the car than getting KR, because cylinder pressures drastically increase in a negative way once you have gone past MBT. Also, for street tuning, and if you have the octane to get there, I wouldn't go past 18* of spark advance this seems to be pretty close to where most cars MBT is. Another thing to take note of is that every car will be different. On the MPS motor, the crank position sensor has a tolerance of +/- 3* so no car will have exactly the same MBT.
I think you need to drop 1st right down to 35-40% to get traction and 2nd to about 60% but it will most probably be different for you than what I tried due to tires etc. I got it setup well traction wise but it made my car feel slow and no where near as fun to take off. You could also play around will load limiting. You have me interested in trying it myself now