Programmable Timing - the 3D approach

[kmart356]

The quest for improved timing for the Spyder engine led me to have a custom distributor built for me by Ken Hand. That worked well with a Dale A/R until I started pushing for higher boost levels. Once the Mikuni HSR45 was installed and tuned, the boost performance just kept getting better and better and then programmable timing became part of the mix.

There are a few timing boxes that allow for very flexible timing control but the one I have focused on is the CB Performance Black Box. CCF topic for background can be found here: Turbo Ignition Timing – Optimizing Performance with 3D Timing

Having recently completed an engine rebuild, the timing needs to be revised to take advantage of the Mikuni flowing through 140heads. This is the first revision that will be used for initial break-in and testing. The "idealized" 140PG timing is shown on the left with the Black Box Turbo Timing on the right. Turbo graph shown for boost up to 9.4psi (for clarity) but the timing table used to generate graph extends out to 20psi. Water-Methanol is used to keep things cool
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[toms73novass]

Kewl stuff.

[chris]

That is cool Ken, thanks for sharing!

[kmart356]

After reading a couple of threads on timing and "target AFRs" there was a suggestion that with programmable timing you could make the vacuum advance have different ramp rate. The objective is to provide more vacuum advance during idle - low rpm range and to provide less advance in the higher RPM range. This is what that looks like. Vacuum advance does not need to be linear either! This is for my turbo engine.
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Nearest (lower) line on graph. Base timing is 18* with 10* advance @ -13inHg. Idle vacuum is just at -16inHg at 1000rpm.
Farthest (upper) line on graph. High end timing is 31* @ 4000rpm and up. Vacuum advance is 5* in that region.
This approach prevents those dreaded "rattles" during acceleration from cruise to WOT for the most part.

[Nashfan]

Have you considered the suggestion of adjusting the vacuum advance ramp rate with programmable timing to provide more vacuum advance during idle and low RPM, and less advance in the higher RPM range for your turbo engine?

Thats what Ken did! it works very well. I do a version of this on mine and its amazing how snappy it is compared to the stock turbo timing!

[manvair]

Don't be fooled- that post was written by a bot so that they could insert a link into the signature line.

[azdave]

Don't be fooled- that post was written by a bot so that they could insert a link into the signature line.

FYI...manvair is talking about the new member "Barefiece" and I just deleted their signature that contained a commercial link. There is a slim chance it is a legit Corvair person but they'll get once more chance to contribute before account deletion.

[kmart356]

Thanks for the cleanup @azdave!

After some additional consideration, I decided to use a more conservative timing scheme until the fresh build has a few more miles on it.

This one is patterned after the custom distributor with vacuum advance + Safeguard for boost retard function. That dizzy+Safeguard combo worked pretty well so this timing map should be a good start until i have confirmed the jetting on the Mikuni as well as water-methanol injection performance.
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[Nashfan]

Just for "kicks and grins", maybe you could post the timing curve on my engine, AKA wildchild?
If you still have it. I dont.

[kmart356]

Just for "kicks and grins"...

... a thing of beauty to behold!!!