IcemanG17

My new racer has a bit of a hybrid 928 16V motor......its a M28-15 engine or a 9.0CR 4.5L L Jet motor.....the cams are Euro S (not sure which ones) its have a valve job, ported heads and port matched intake + headers......it also has a full Euro LH intake with MAF (even though it doesn't use one, it runs MAP sensor)

The fuel is controlled by a SDS EM3-E that also controls timing via a Crane system used in oval racers.... so its totally programmable far beyond the stock system of turning the distributor....

I looked at the stock 1980 L jet ignition advance curves...it looks like 10' is the base timing at idle & its advance curves are about 16' at 1000rpm and rise to about 23' at 3000.....max is quoted at 28-34' at 6000rpm.....

Right now I am running a bunch more timing than this down low.....peaking at 32' at 3000rpm and holding that all the way to redline.....

I attached my current dyno chart......AFR's look good and torque is STRONG down low, especially for a 4.5L.....Peak torque is 4250rpm and peak HP is 5640rpm.....it makes me think that the valves probably are stock USA size....since true euro's make peak power higher...

My plan is to try making adjustments.......do a baseline run at the current 32' timing....try 2' increments from there....34'-36'-38 until it stops making more power or we hear knocks on the dyno.....

Right now I can either loose 176lbs or gain 20hp and still make the race class I am shooting for....

Other ideas?

anonymousagain

Brian, no hands on to contribute, but if it runs well and you like how the powerband delivers, it seems the weight savings is the bigger benefit. 20hp isn't much for the limited benefit, but 176lbs less benefits you around the entire track.

Until the power gain is significant, Lighten Up!

123quattro

You don't need to hold static timing from 3000 up. You really would want to start adding timing back in once you get past the torque peak. I add a couple degree every thousand rpm. Combustion takes a certain amount of time. As the engine spins faster you have less time to get the combustion in. So, you need to start it sooner to get the pressure to wind up in the same place during the expansion stroke.

That said, l agree that dropping the weight would probably be more beneficial to lap times.

Lizard928

I would be watching the oil ejection too.
10 linear to 32 at 3K is a good old school setting that is pretty safe yet makes for good power.

I doubt you will pick up much if any power above that but I could be wrong.

IcemanG17

The SDS system allows timing adjustments every 250 rpm.....same for fuel.....

I also watch oil ejection closely...since I don't go past 6k, it burns very little....about .5 qt in 2.25 hours on track last weekend...it is a stock setup....I plan on changing that so it can't inject oil vapor into the intake....

I'd like to optimize the engine, then back off a bit for safety...... We shall see how it responds....probably near the end of this month.....

toofast928

+1 on the oil consumption. Its the first sign that the cylinder is beginning to detonate. The timing on my 5.0L Hybrid with 9:1 was 27 degree -WOT.

IcemanG17

I did some research.....I found Scott's 5.0L euro build up....here is his dyno chart at 5.0L....his power and torque peaks are nearly identical to mine, just higher.....when you consider I have only 4.5L of displacement......its not too bad.....only 32' max timing.....I think his peaks at nearly 36' since his base timing is 12'