2056 Timing, Looking for Analysis Of New Timing Values Options

[Mblizzard]

I have converted my 2.0 to a 2056 and added Micro Squirt fuel injection.

Ever since I did the 2056 conversion I have seen higher than norm cylinder head temperatures. In fact I cracked a set of heads from getting them too hot.

I played around with the timing with in the suggested 2.0 limits of around 27 degrees. but was really never able to influence the CHTs that much with changes in the timing. Adding more fuel at the right times with the Micro Squirt certainly allowed me to control the CHT much better but I always felt it was still getting too high.

Then I ran across this.



This is certainly a lot more advance than I ever added to the engine. So based on that I revised my timing table to:



Just love how easy it is to make changes with Micro Squirt.

So I am looking to see what the thoughts are on 35 degrees of advance and what impacts it may have on CHT. I am going to load this and test tomorrow.

[Mark Henry]

I got to admit looking at those tables is so confusing, the main reason I've never embraced MS or other data overload systems.
It's a fricken timing curve, not rocket science!

My SDS has one value per 250 rpm, that's it. Same could be said about a mechanical dizzy, sure springs but it's a simple curve.

I agree with Jake and Mark, idle too low I run 10* and 30*+ is too much advance on a T4, I run 28*. If anything I'd consider retarding the timing a bit as I approached 6000 rpm.

One of my tricks when tuning is I have a highway close by that has a long (10km) steady uphill grade and it's divided by a concrete barrier. When in the passing lane you are about 24" from the barrier and the sound bounces so you can really hear the engine mechanicly. I've tested 1.8, 2.0, 2056, 2270, and my 2600 T4's any time I push it to 30* I can hear the ping. I can also see head temps going up.
Ping is about the equivalent of hitting your piston top with a ball-peen hammer. Sooner or later it will kill your engine.

The chart above "Ideal 2056 Adavance Curve" that might work on a WC engine but I'd never consider it on an aircooled T4.

[JamesM]

I got to admit looking at those tables is so confusing, the main reason I've never embraced MS or other data overload systems.
It's a fricken timing curve, not rocket science!

Watching a three dimensional system operate in real time helps a lot in understanding how it works and in reality it is not much more than a simple timing curve once you know how to read the table. Its really just 10 simple timing curves stacked on top of each other.

Take a single horizontal line of the table and that is basically what you have with SDS, a timing setting where the only variable is RPM ( X RPM = Z degrees advance) Like a distributor that only has centrifugal advance. Setting all the horizontal lines up the same produces a table that works exactly like SDS works.

The Y axis of the table represents engine load. Depending on how you have the system configured this is usually determined from manifold vacuum but could also be throttle position.
So basically every horizontal line is its own independent timing curve and which one is in use at any given time depends on how much load the engine is currently under (or at what position the throttle is). So the top line is basically the ignition curve that is used at wide open throttle, and the bottom line is the timing curve used when the engine is closed throttle under deceleration and everything in between is everything in between, timing curve for 60% throttle, 70% throttle etc. Its sort of like adding vacuum advance and retard cans to a distributor, but magic ones that are able to defy the laws of physics that apply to a vacuum canister in order to provide exactly what you want at all time.

Obviously having load dependent timing curves is not necessary for an engine but it does allow you to optimize for all running conditions and do some cool stuff, tricks that you couldn't otherwise do. It can be used to improve drive ability, gas mileage, emissions etc without impacting your WOT power. Fully optimizing a tune to this extent though would require tools not readily available to a home mechanic which is why i question a lot of peoples tables that look like they have been.

The table I posted is pretty simple as it is basically the same curve across all loads, the only change i made from there was to not have the timing advance as quickly in the low load/idle area of the map in order to help stabilize the idle but still immediately ramp up the advance as soon as you get on the gas.