Hey, I know that NO table that works well with your car will work perfect with mine, but I'm looking for some help with the timing table on my Iroc. Stock table is way too high as the car stumbles some, but it revs(in nuetral) much better with more timing). of course WOT needs low timing as it is a boosted car!

Its an aluminum headed SBC with 8.5/1 compression and a ysi supercharger. I am using MS II extra. Does anyone have a general timing table they have had luck with on their megasquirted boosted cars for me to start with?


Thanks

 

The timing of the stock table and the less than 100KPA table of a 2 or 3 BAR spark table will be very close to the same. You should be able to start with the stock spark table transferred to the MS spark map, then taper off timing above 100KPA as a base.

If there is a drastic difference check other things, like timing offsets, base timing, even where the dizzy is set for base timing.

Too much or too little fuel can also cause a stumble.

 

I recently had my old laptop crash and I was unable to get those files from it. That's why I need it

Do you have a way to get it?

 

Just borrow another laptop and reload what was in there, then we can look at it and go from there.
I just did a FAST XFI with 12psi of boost, it had about 23 at wot under boost, and 35 at 102kpa. Taper it from there. Timing can cause a stumble too. And make sure your timing is what the ECM thinks it is.

 

Thanks... I've double dchecked it to the balancer many times. Its right on! I will try and find a way to get the stock table and start backing it off. I will post up the table as soon as I get that done.


Thanks


ps, I'm looking at about 17 psi max.....

 

I'm using the Holley commander instead of Megasquirt, but I use a spreadsheet to make it easier to smooth the values. I have a similar setup, but turbocharged instead of the sc. Timing at idle is 30°, cruise is upper 40's to 50°, and since tpi's have peaky torques, I retard the timing a few more degrees and then add it back in the upper rpm's. You'll also notice that the timing ramps up very fast off idle which helps eliminate hesitation. Timing under boost is fairly conservative, but I'd rather be a little safe.

 

You have 50+ on decel, not crusing. I doubt you're crusing at 22in of vacuum, that's decel vacuum. And if you are I still think that's too much however you look at it. I hope you're not recommending he run that much as well.

And if your cal was right you probably wouldn't have to run that much timing to alleviate your "hesitation'. The reason you have the hesitation is because of improper transient fueling somewhere. The additional timing is just masking that. Your slow LC-1 is contributing to that as well. I've attached a lab test below showing just how slow and inaccurate the Innovate stuff really is.
And typically you need the most amount of spark wherever it makes peak torque, and that's always where you'll need the most fuel.

I was never impressed with the 950, because it fires all eight at once so you'll always have 2 cylinders that will run leaner and 2 cylinders that will run richer than the other four. Plus it's transient fueling tables are limited, your driving quality problems are a testimate to that.

Jmo.

 

Here is what I have so far. i simply took the "stock" table and took timing away ONLY under boosted conditions. Is that transition too rough?

 

Woah! If I'm reading that right, 100kpa should be wot no boost (0 vacuum or boost). There you should have about 34 then go down a degree or two in timing for every # or so of boost.
That layout seems like it wouldn't run too well.
Question, can you not scale your rpm ranges? I see it has large gaps in the horizontal scale, i.e. 3000 to 3500, then 3500 to 4000, then 4500 to 5700. Are the fueling scales laid out the same way?

Thanks.

 

Thanks for your help... I JUST noticed that. I will work them more tonight and scale them evenly...Besides it's a TPI car, I don't need 8000 on there. I think I've already scaled my fuel table. I will work on them both and post them up soon