Input needed - Timing curve - Terminator X

[inZane240]

Hey Guys,

Not sure if this belongs here or in the SBM forum. Looking for a little input on my timing curve below. Car is running great, just looking for a little more input to see if I am on the right track.
Engine is a blueprint 408. Blueprint specified initial and max timing, but other than that I'm on my own. I didn't ask, but I would imagine they aren't going to fill me in on what their timing curve looks like on their provided distributor. Appreciate any advice/help.

The graph is vacuum vs RPM. not sure how to get better image quality...

 

[Mattax]

These end up in Electrical, as well is Small Block, Performance Issues and General Tech. Take your pick -any one of them is appropriate IMO.

Yep a little blurry but probably OK starting point.
I know we've had a couple discussion about MAP - RPM AFR tables FI LA engines. They may be worth looking at.

This one starts with a 408

figuring out advance timing

Hey guys. I am trying to learn how to tune my 408. 9.5 compression, 235/239 @050, 535/550 lift with a Holley Sniper feeding the fuel and controlling the timing. The engine was dynoed with a best of 12.8 a/f and 35 degrees of timing at wot. I am trying to learn more of how to fine tune the...

www.forabodiesonly.com

and another

Timing advance guru input needed

I'm running sequential EFI and spark on a 408ci w/ aluminum heads and approximately 9.5:1 compression. I can set the timing advance to anything I want at any RPM, and any load level. I know it would be best to tune on a dyno, but I don't have access to one at the moment. Below is my current...

www.forabodiesonly.com

This one is for a 360 Magnum but you can see what the factory was doing.

Need some help with my timing curve.

So after running an eBay Ready-to-Run Hei distributor for the past 5-6 years, I finally got around to putting a timing light on it and mapping out the advance curve. Come to find out, the curve was severely lacking! I ended up swapping out that distributor with a factory electronic distributor...

www.forabodiesonly.com

 

[inZane240]

Awesome, thank you!

 

[inZane240]

Uploaded a new pic. It looks a little better.

 

[rmchrgr]

Your MAP scaling does not look quite right. I like to use KPA. In KPA the values should be 100-105 at the top and like 10-20 on the bottom. 14.7 psi = 29.92 inHG =101.3 kpa.

Also, what kind of distributor is it? Do you have the ECU controlling timing? You're not going to be able to do much of anything if the timing is not being controlled by the Terminator.

Have you built a custom timing table before? The video below shows how. I'd create a new one from scratch and keep the current ignition config file in case you need to go back to it. Once you put the new file in then you're going to have to play with it and see what it wants.



I've used the image below as a place to start. In your table you have 33º at WOT which is OK but a little conservative. Your cruise timing looks a bit low too. The ECU will add timing for cruise without vacuum advance.

 

[inZane240]

I chose the option to convert from KPA to PSIG as I am a little more familiar with PSIG. 0=atmosphere. The table was built from scratch and started out very linear. Based on research on this forum, a little youtube university, and some datalogging it has evolved to what you see above, although I know there is a lot to be desired, especially in the "vacuum advance" area.

This thread really helped a lot:

figuring out advance timing

I am using the Hyperspark distributor so timing is fully controllable. I haven't figured out how terminator x controls the vacuum advance or if I need to build it in to the table.

For sure starting out conservative until I can get a decent map or a better r handle on w am doing. I don't want to make a fatal mistake.

 

[rmchrgr]

Well sounds like you're on the right track and the car is running OK so I wouldn't be too concerned with screwing things up. You can always go back to a known good tune if you find something isn't working.

The Hyperspark obviously does not have a provision for vacuum advance so you have to make adjustments to whatever cells you select in the table. I found the image I put up of how the table areas are delineated was really helpful for that, kind of took the guess work out of it.

Not a ton of EFI guys here so I'd consider joining the Holley forums and see if you can get a little more detailed help over there.

 

[inZane240]

@rmchrgr What would you recommend for a conservative total timing plus "vacuum advance"?

 

[rmchrgr]

@rmchrgr What would you recommend for a conservative total timing plus "vacuum advance"?

Not sure how rowdy your engine is but the table below was from the basically bone-stock 383 that was in my Sniper-equipped '68 Coronet. Initial was 20º, WOT was 34º and cruise was 44º. That engine had 10:1 compression ('68 factory flat top pistons), later 452 heads, factory 335hp hydraulic cam, headers and an Edelbrock Performer which is an aluminum copy of the stock intake. The 1968 factory dual point initial timing spec for a 383 4bbl was like 10º or so so I was literally at double that with no real downside. In general I'd say give it as much initial advance as it will tolerate without making it hard to start.

I arrived at the timing numbers by trial and error but I will say the increase was significant from the Wizard tune. To start, I put numbers I thought would be OK in the corners of the table, selected all the cells and smoothed the whole thing. I strated conservative like you but found that increasing the timing in all areas was generally a good thing and was especially true at lower RPMs where that car spent most of the time. Past a certain point it's diminishing returns though. Too much timing will usually make it run hotter so if you can't hear pinging pay attention to the temps.

In my limited experieince, WOT will generally be between 32º-36º but for a performance engine you'd probably want to see at least 34º. I know from dyno data my old 416" combo from my Duster liked 35º. That's a Ricky Racer engine with high-flowing heads and a big cam though so yours may not need that much. Just one of those things you'll have to mess with until you find the sweet spot. Log away and study the learn table to see what works.

Cruise timing can be almost 50 in some instances. I'd start at 42-44º. You can tune that in a live setting to see what happens. Thst would be similar to driving around with a vacuum gauge in the car. I'd also suggest watching the AFR table and see if it's hitting the targets with whatever timing you have it programmed at. I think my cruise AFR was like 14.8.

You're not that far off so just keep going. Hope that helps.