MAP Timing with Speedtigger :p
 

Today I went out for a ride and really focused on my MSD 6010 MAP settings.
My goals were to make sure they came in at the right time to achieve a consistent idle, high efficiency cruise and assure all the MAP timing comes out by WOT. Here is a graph:

http://px6.streetfire.net/0002/67/06/2137660.jpg

BASE TIMING
My base timing is typically 27 degrees. I chose this base timing based on the 1/4 mile track testing.

I should probably also share that a base timing of 27 degrees in the idle RPM range would not be a good idea for an automatic car with a stock or low stall torque converter. It will also likely cause a stick shift car to rattle (pre-ignition) at low rpm loads. However, my experience says that initial timings of 18-30 degrees can work great for quick throttle response and fast revving in a larger camshaft, high stall automatic equipped car. In fact, most racers with an automatic would probably tell you that they have their timing locked at their ideal total timing figure.

MSD's MAP TIMING GRAPH
Before I start, I have to say that the MSD's map graph is not expressed in the typical inches of vacuum. Not only that, to make it even less intuitive, the lower the number the higher the vacuum, the higher the number the lower the vacuum. So, if the way that I express more or less, higher or lower, etc is confusing, send your complaints to MSD. :D

IDLE TIMING
To get started, I wanted to see what the car liked for idle timing. Over the years playing with this, I found some characteristics that set the parameters for consideration. I found out a long time ago that most cars will keep idling faster and faster with more and more timing right up to the point where it starts to misfire. One might conclude that this is where the idle is most efficient. However, I find there is one particular draw back to these very high idle timings. This is that there becomes a huge disparity between the in gear idle speed and the in neutral idle speed. So, to get a reasonable in gear idle speed like 700-800 for an average street strip camshaft, the in neutral idle speed race up to well over 1000 - 1200 RPM. With less timing, the disparity between idle and in gear RPM lessens.

The downside of too little timing is lazy throttle response and slow revving off idle. So, I tried to run as much timing as I could and still have a stable consistent idle in gear and in Neutral. For my application this was about 36 degrees total timing. Since I have my base timing at 27 degrees, I had to get 9 degrees from the map. Stick shift cars and cars with stock stall converters will want to use less base timing and more MAP timing.

So, my MAP for idle is set to 9 degrees timing between 6.0 and 9.0. 6.0 was chosen as the top(higher vacuum) number because the idle vacuum did not rise above that number in neutral. The 9.0 lower limit(lower vacuum) was chosen because the idle did not fall below that number in gear. This is important because if the timing starts decreasing as the RPM drops, the car could fall into a stall spiral. If the timing starts increasing while the car is in neutral, the idle will tend to race when in neutral causing an annoying high idle when in neutral or park.

CRUISE TIMING
Above 6.0(at higher vacuum levels) the MAP timing ramps up to 19 degrees bringing the total timing to as high as 46 degrees. These higher cruise timings were very typical on many cars I have worked on over the years. This works for low load cruising because the volumetric efficiency is so low(meaning there is very little cylinder filling at low load cruising). All of this is dependent on vehicle weight, gearing etc.

Why 46 degrees? I don't have a scientific answer. I went driving around testing. I had the total timing as high at 58 degrees at light cruise. It just sounded and felt best just below 50 degrees maximum. So 46 is where I landed. From memory of evaluation other cars factory calibration over the years, that was pretty typical. I also attempted to ask some of the tuners in the tuner section of this site what they observed for cruise timing, but got no answer. I am not worried about these higher levels of timing because as more throttle is applied the vacuum reduces and the MAP starts pulling timing, so the engine does not experience too much timing under higher loads.

WOT TIMING
Below 9.0 (at lower vacuum levels) I ramp it down to 0 degrees MAP timing at 11.0. I chose 11.0 because 13.0 was as low as my MAP sensor would display at WOT. So, I wanted to make sure there was absolutely no chance I would be adding any MAP timing at WOT. This is especially important in high compression and vehicles with Nitrous like mine.

Well, that is how I came to my current MAP settings. Combined with the extensive tuning I have done to my Holley 950 HP, the car drives pretty damn good.

I thought some more about simplifying my timing strategy and I decided to try this:

http://px6.streetfire.net/0002/67/16/2137661.jpg

This strategy would allow more timing at a cruise while still limiting total idle timing. It employs a single step up in base timing at 1100 RPM (about 100 RPM above my in-neutral idle speed) that allows for a simpler single step in the MAP taming just below idle vacuum levels. My only concern is slower revving and slightly reduced throttle response when stabbing it from an idle. And perhaps slower response when flashing the converter at the drag strip. My setup works best if I load the converter to about 1400 RPM and then stab it from there. I will test it tonight and see how it drives.

Nice write up! I keep putting off making the FAQ/all you need to know about carbed LS sticky but this will be in it!

Thanx Zone. Hopefully others will come in and share their insight and experiences.

One thing that I was uncertain of is how the Idle Timing Control option feature works. So I called MSD and here is how they describe it:
This feature tries to help maintain a consistent idle RPM by varying timing. So if the RPMs drop, it increases the idle timing, the if RPMs rise, it reduces the idle timing.

This feature only has two settings. On or Off. LOL So, you cannot tell it what idle RPM you are trying to achieve. The tech said it samples your current RPM and tries to keep it stable. It re-samples at intervals, but he did not know the intervals or how much it was capable of varying the timing.

He knew how it functioned but did not know the intricate programming details. So, I guess I will just try it tonight and see how it goes. However, my cars idle is very stable, so I don't know that I have anything to "control".

I've toyed with it some but it wasn't very friendly with my cam. It wanted to jump around alot and it Didnt sound good to me. I'd worry a little if you drag your idle down when you put it in gear from a neutral idle and it cranks the timing to keep it up and either starts you driving or speeds you up. I don't think it would make much difference unless you weren't expecting it lol. I idle in neutral at like 850 and like 650/700 in gear so for it to pick up 150-200 rpm that's the difference in me moving slowly or not slowly lol

I always made the assumption that the idle feature was for those using the 6010/12 on a engine that had injection.

I only have 1 spare MAP so I will still have to wait till I can try the setup on the stang or TA.

Thank you for all the info and putting in the time.

Great work....:cheers:

Well, I tried the Idle Timing Control feature tonight. No good for me. The idle started hunting and surging badly. So, disabled it will stay on my car. Anyone else have experience with this feature?

What's happening on the dashboard when it's hunting? Is the timing moving around? I never tried it as I, too, was under the impression it was only for injected stuff...

Nice work Speedtigger, just to throw a monkey wrench at the topic what do you think of this lol :

http://i971.photobucket.com/albums/a...ps28832848.jpg

Timing would vary wildly from the teens to forties.

Looks like turbo stuff. 3 bar map?

What is with the little dip between 700 and 900?

The only thing I would wonder looking at your graph is does it ever stall on you? The reason I ask is you timing starts to drop at 700 RPM. This could encourage a stall spiral if the idle drops below 700.

Yes, 3 bar map for my turbo setup.
The small timing dip at 900rpm works fairly well to stabilize my idle, but I'm not sure it's worth using up precious dots . I might try having timing higher than necessary below idle rpm. I am constantly messing with the timing curves to try get best driveability

Do you have the Idle Timing Control feature enabled?

Also, you might try running less idle timing. It can slow throttle response, but it can also stabilize the idle a bit. What is your idle AFR?

No, like yourself I always believed it to be for EFI apps. I have tried less idle timing, but I seem to have best results with it fairly high. My biggest issue is having the engine stall upon quick close of the throttle, like getting out of it as you come up on a yellow light . Richer idle a/f's, and the higher idle timing seem to have the best results for that problem.
My car likes 13.2-13.5 ish idle O2 readings.

I have seen that before. What size is your IFR and LSAB?

Also, you may want to set your first timing curve point to be at 300 RPM and not 700 RPM. That way if your engine were to happen to dip below 700 RPM, the drop in timing won't encourage a stall spiral.

What is your idle RPM?

My idle speed is 900. It it the red highlighted dot on my rpm graph, you can see that I programmed 900 rpm to be at a dip in timing - trying to stabilize it.
Edit: I see what you mean with the first dot at 300rpm, I'll try it.
I don't know what the idle restrictors or low speed bleeds are, I had the carb custom built by Kevin at CSU, and I have not altered it except for jets and shooters, it is really good. The stall upon rapid decel has happened to me on other carbs as well, not just this one.

I know what you mean 3Peds...I had it happen a number of times on the old 406ci SBC and this LS a few times.
The 406 was locked out timing and no vac. adv. hooked up...this LS is fairly stable in the timing dept. also...now anyway.
I always contributed it to some fuel slosh from the vent ?