[428GTO70]

Not sure if this is the right section as I am running naturally aspirated but it is an EFI question.

I am getting ready to try and start up my new 458 build with a Holley HP efi system and a computer controlled HEI distributor. I was wondering if anyone here had some experience with this system or some advice for making a good street spark map? My combo details are in my signature. Any advice or info to get me started would be greatly appreciated!

Bob

[darbikrash]

I see that you have an Holley HP system? I would start with an exisiting spark map for an engine close to yours from the Holley database. I'm using the standard Holley calibration for the 496 Chevy rated at 650 hp. Now I don't have that displacement (or that HP) but it is a decent start.

You can find that base calibration under the Holley global folder, "Custom Calibrations" when you first login to the EFI programmer. You can save this as a new file name, and edit the values to reflect your actual displacement and engine parameters.

To get the best possible results, you might want to consider some dyno time setting up spark hook curves to establish MBT (mean best torque) as a function of engine timing.

Is it throttle body or port injection?

[TheSilverBuick]

^^^That guy actually uses the system so take his words over mine.

On my home project Megasquirted cars this is what I do:

Set cranking to something between 5* and 10*. I use 5*, cranks fast that way.

Set the whole table to something safe like 15*, it should run at 15* but add some if it stabilizes the idle. Let the engine warm up to operating temperature, work on the idle fuel so the AFR's are good then work the timing table. At idle just go up or down on the timing and see what it likes. You may need to adjust the AFR's a bit after a couple of degree's of timing changes.

Then I set the WOT and the bins right under the WOT values to a conservative number a bit less than what you expect it to like for max HP. Like 28* to 30*. It lessens the risk of damaging detonation, especially if your initial tune runs a little lean. A dyno or track time is the only real way to optimize where you want it (or maybe you already dyno'd it?).

Then fill in the rest. I usually set cruise timing to 38* and incrementally up it from there from driving it and seeing what it wants. Typically land between 45* and 50* total at low load cruising. I find as I add timing during cruising the AFR's get richer, so I lean it back out, then add more timing until it's too lean then I back off the timing a hair and add just a touch of fuel so it runs smooth at cruise.

[428GTO70]

Thanks to both of you, I will look into trying some of that. I started with one of the base cals but it starts at like 25 degrees and that seems a bit high to me. anyone else happen to have a good finished map I can start with? let me know

[krisr]

I hooked up my shifter to the ECU so I could switch spark maps to have 1 spark map for when i'm in gear and 1 for when i'm in Park/Neutral where I run 38° timing in gear at idle and 25° timing in park/neutral.

Below is how I set my 400 (in gear) but haven't optimise the 100kpa cells on the dyno yet so just took a stab at the curve and from the seat of the pants it goes quite well. The cells around 4000rpm/100kpa I found I would get slight pinging so pulled a couple of degrees there (i'm assuming i'm at peak cyl pressure as that's roughly where my VE table starts to taper down too) but ramped timing back in. If I cruise with timing more than 38 it starts to pop in the exhaust and you can hear a change in note where it sounds like it's skipping, the manifold vacuum decreased too. You can easily log a few parameters to work out your cruise timing after a few runs and interpolate most of the map, but the 90-100kpa cells you can only guess at without a dyno/ET's from a timeslip.

and all that jazz...

[428GTO70]

Thanks Krisr! That looks like it could be a good starting point for me, I really appreciate it!

[krisr]

Just use caution if you're going to replicate my map - maybe pull 5-8° from the entire map for safety and check your trigger angle to make sure your ECU is sync'd to your distributor so the timing on the balancer matches what you're commanding.

[428GTO70]

Originally Posted by krisr

Just use caution if you're going to replicate my map - maybe pull 5-8° from the entire map for safety and check your trigger angle to make sure your ECU is sync'd to your distributor so the timing on the balancer matches what you're commanding.

Yeah, ill be cautious. and yeah I still need to sync the distributor to the ecu. Thanks again. I actually need to address a leaking head gasket issue before I can try this but hopefully it will be soon.

[TheSilverBuick]

Yeah, always check the commanded timing with a timing light. Check at idle, around 2,000rpm and on upwards 4,000+ rpm. I usually set it for a fixed number like 25* across the board and you shouldn't see the timing waiver with the light as you rev the engine, at least not with a crank trigger. If it's a distributor trigger you want the timing to be on the money while the engine is accelerating, so calibrate to that.