sand_man

Okay experts, refer to my rebuild thread for more details, but I'm running Electromotive XDi twin plug with SC cams, k27-7200, B&B headers, IA fuel head, .80 BAR wastegate spring. What do you guys advise for the timing curve? Currently I have the dials on the ignition ECU set as follows:

10 degrees for initial dial
15 degrees for 3000 RPM dial
-3 degrees for 8000 RPM dial
RPM limit dial set to 6,500
I also have a MAP sensor. I'm still in the break-in period, so I'm not driving the car too hard.

Should this be advanced...left alone...retarded???

m42racer

It will be hard to tell the limit until you apply full boost WOT. I have been told many times to do the following. Take 1 or 2 degress off the setting you have now and see if the engine loses power. If it feels the same, adding more will make no difference.

Do you have a knock display? Get one from Performance Developments. They are really good and will tell you if its knocking. best to be sure.

D

Seems like a very conservative curve. With EFI I have mine set to 29degrees all the way to 7500, but pull back 15% timing (4.3 degrees) by the time it reaches .8 bar, above .8 I pull back 25% timing. At cruise RPM's with no boost it is set around 32degrees. Does the XDi allow you to pull back based on the MAP?

DonE

That seems extremely conservative. Remember, too little timing is bad too. You will add LOTS of heat. You need to go to a dyno that can put a load on the motor for correct adjustment - don't screw with this part.

To give you an idea, I have a copy of a good map from a 500 hp motor - initial is 11, 1800 rpm its at 35 degrees, peak torque its at 25 degrees and WOT/red line is 22.

PorschePhD

You don't want to retard too much. The goal should be to steady state it on a dyno. Add timing until the TQ stops coming up. When it levels off then drop back to the mark that the highest TQ was achieved. This is your safest and max power and TQ number. I would expect your car to see somewhere in the 18 degree range. Still, check it before going there. I like my initial a little higher on the CIS cars. That is just me though.

sand_man

Thanks guys! Keep in mind that with the numbers I posted, you need to add them...so I've got 10 degrees from 400 to 1,000 RPMs, then add another 15 degrees from 1,000 to 3,000 RPMs (so 25 degrees total), then retard 3 degrees (-3) from 3,000 to 8,000 RPMs. So between 3,000 and 8,000 RPMs I'm at about 23 degrees.

PorschePhD

Ok, I didn't realize you were not giving us the total advance. On a TP system you actually need less timing.

sand_man

Forgive me ignorance...what's TP? Throttle Position?

E-man930

twin plug

sand_man

Thanks! DOH! Okay, now that we're talking about total advance, I wonder if in my twin plug set up, there's too much timing? 25 to 23 degrees.

PorschePhD

There is only one way to find out. BUT as a point of reference my builds never run that much timing. Of course there may be some differences. I run a bump in CR which would also cause less timing.

DonE

Done right, setting the timing is akin to an art, and no two custom built cars are the same (sometimes, they are close)...

The only constant here is that you can not set your timing using someone else's timing table.

edpurplett

.. and to add fuel, pardon pun, to the issue... I was watching an initial tune on a Chevy LS-1 w/ an 8 lb supercharger kit added.... they showed 50.x additional HP with the last degree of advance.... from 460 to 510 RWHP from what I remember...(28 degrees total?) They didnt add another degree so we could compare.... I think they were so happy with what they got...

Not 100% relevent, but I jsut watched the show Sunday .. :-)

ed

Ed

edpurplett

FYI my advance..goes from about 20deg at 3k to 16 deg at 5k back up to 19 on top, at full load. It varies considerably according to load though. But don;t forget I have 8.9-1.... just to show annother rig....

DonE

I just came from 3 days of dyno tuning my motor on an engine dyno. My initial timing starts at 22, at 1800 its 34, 3500 (1 bar) its 28, at 6500 (1 bar) its 15. This was after we tried different numbers monitoring torque, EGT, AFR, knock and so on. This might be real different from other turbo's, but this is what the engine took.