XF EFI Crossflow Advance Curve

[SteveHobart 57]

Hey All

 

I am looking for some help. I have a XF Crossflow EFI which I have built with:

Crow 14771 Cam

Zero Decked head- 10:1 compression

Lightened flywheel

 

And a few other small mechanical mods. It’s all run with a MS3X ECU.

 

Whilst I can get the fuel table pretty close, I am struggling a little with the advance curve on the dizzy. I have confirmed 8 degrees base advance via a timing light with the Spout disconnected.

 

Does anyone have, at least a stock advance curve that I can input into the ECU as a start. I have it booked in for a Dyno tune on the 1st of July (earliest booking) but really want to give it a crack before then!

 

Thanks in advance

 

 

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[Mixalis 266]

Hey Steve,

 

Just confirming you do in fact have one of the TFI/EST Hall effect distributors without any mechanical/vac advance systems built in?

 

Regarding the timing curve, I set up a 'curve' (with some advice from @gerg) quite a few years back on my crossflow using a 6al2. It has been quite a while and I never touched it since, but it was effectively linear'ish' between by timing at idle and max timing at WOT RPM (my combo has higher compression, i believe i kept the ceiling somewhere around ~26ish degrees, been a very long time). I spent more time hooking up a 1 BAR MAP sensor to dial in advance at different loads as well which helped with economy. It works fine but hasn't been on a dyno so theres room to improve

 

I then road tuned a 4.0 sohc turbo that I fabricated and wired (Stinger ECU) with a similar curve (at atmospheric) and then dialled the timing back under different boost pressures. When I started tuning the fueling, i had the timing at a static value the entire curve - it drove around absolutely fine. Left the timing till last - took an educated punt based off other people combinations. It works fine, hasn't been on a dyno so definitely has room to improve.

 

Moral of the whole story above - if you're going to a dyno, I honestly wouldn't worry too much about the timing side of it - even a single value across the whole curve will work fine. If you don't have access to a dyno and a knock sensor, you really are just guessing. Even if you rock up to the dyno with a flat timing curve, as long as the dyno operator has a knock sensor (and of course a dyno), then you can hopefully rest assured they will do a good job after you drop the car off. 

 

But you've done a great job to sort out the fuelling side from before and also confirm that the ECU knows the position of the engine (timing at ECU is what you see on balancer) - that will surely save you some dyno time money. Really keen to see how you go!

[gerg 10,871]

Yeah all good points Michael, generally the more cam you have, the flatter the ignition curve will be. 8 degrees sounds very conservative given that you've got a bit of a cam happening. I would start at 15 , ramp up to 25 at 3000 then 30 at 5000 and see where that gets you.

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[Outback Jack 6,352]

I agree with Gerg with above info.

For a crossy, 10 degrees at 0-500rpm means an idle at 12 degrees.

Then try a curve with more points, I think from memory a rough guide is 2 degrees for every 500rpm.

 

So at 0-500rpm 10degrees

500-1000rpm 12 degrees

1000-1500rpm 14 degrees

1500-2000rpm 16 degrees

2000-2500rpm 18 degrees

2500-3000rpm 20 degrees

3000-3500rpm 22 degrees

3500-4000rpm 24 degrees

4000-4500rpm 26 degrees

4500-5000rpm 28 degrees

5000-5500rpm 30 degrees

5500-6000rpm 32 degrees.

 

This will give you a great base curve to tune from. The MSD 6AL series like to have multiple reference points.

That timing will be pretty good, I set up a crossy with 600 holley and that curve.

It's a good starting point for all timing set ups.

Just add in an extra 2 degrees per 500rpm to whole table if you want to peak at 34degrees @ 5500-6000rpm.

That would mean you have a 0-500 of 12 degrees. Around 14 degrees at idle.

 

You can thank@ando76 for that, he's the one that gave me the info on how to set up a good base curve.