Engine Dyno 328ti

[andy]

Hi Guys,

Here is the first dyno from my new engine before and after tuning. You can see that the red line (before tuning) was very lean and preventing the engine from making a lot of power below 4000rpm. The top end of the power now shows as running pretty rich, and with less fuel or more air into the engine we'd get another 5-7hp on the top end.

Engine is an OBD1 2.8 with M3 cams, all stock internals... about the limit of what I can do for US Touring cars and remain legal. And it should last a nice long time, and even pass smog.

[cali-ti]

what all did you do during the tuning stage?

[andy]

We tried several off the shelf GIAC chips, keeping the equipment on the car pretty consistant. I think this one was designed for a 3.2l m3 engine in an OBD1 car. Next step will be to try to adjust or air to see what gains we can make, but I'm checking with the rules guys to see if going to a larger HFM is legal. If not, I can probably go to smaller injectors and get more power as well.

[jcarp]

Andy, I'm not sure I'd consider that running rich in race trim. You may want to use EGT's as a guide not just AFR's. That 5-7 hp could cost you in engine longevity.

[andy]

HAha - yes, I do really want to keep it safe, this puppy needs to last a while or my next track day will be in a 212K+ mile miata. :) Project this week is installing new springs (have to keep up with the motor now) and I sorely need a gauge package. I hadn't thought about checking EGT's though - not a bad idea. I also plan to religiously go through the oil analysis process and to see what's going on inside as well.

[jcarp]

What spring rates/suspension did you decide on?

[andy]

I have 550 and 650 springs on my workbench, all 2.5x6" so I can try either in front. I left the old springs on for Thunderhill since it looked like there was a good chance we'd be running in the rain. They didn't work badly, although I do show a mildly alarming amount of travel sometimes. :)

http://gotbluemilk.com/web060424/38/imagepages/image9.html

In fact the rear was more planted than I'd imagined it would be and I picked up a few seconds toward the end of the race turning in earlier and getting on sooner than I thought it would handle. It could be my old 'ti diff wasn't in as good condition as the 88 325 diff I'm using now, or that the Z3 M fins on the back were keeping things in working order better than before.

I've got Buttonwillow in 2 weeks to test the springs; it's a great course for that, good mix of fast and slow (understeer punishing) sweepers and a very nice high-grip long sweeper.

[HuGo]

if i read correctly, ur car has 196hp?

[cali-ti]

the 88 325 diff will have a larger fluid capacity too (besides the m-coupe diff cover) ... all helps to keep it cooler. was the ti diff a LSD?

[andy]

if i read correctly, ur car has 196hp?

Right, to the wheels. Figure about 230 at the crank, give or take. My M42 dynoed a little over a year ago at 125 to the wheels. Nice upgrade. :)

[andy]

the 88 325 diff will have a larger fluid capacity too (besides the m-coupe diff cover) ... all helps to keep it cooler. was the ti diff a LSD?

I have run both the stock 3.45 LSD that came on the car when it was new, and a 4.44 LSD that was very difficult to find. The new one really sticks in spite of the new power. I'll have some work to do to use the car to its fullest pontential .