Bugeye EFI progress

[Glen_B]

Its been a long two weeks as I burned out the first wide-band O2 sensor, redid all the firewall-to-bonnet wiring harness to incorporate the new wires and look neat. Last night I got the first engine start with the ignition activated. Now the Megasquirt is in control of the fuel AND the spark. Its back to the books tonight as I study up on designing a "perfect" timing table for a turbocharger engine. I can set in timing values for RPM from 500 to 7000, and for manifold pressure from 10Kpa to 170Kpa (idle to 10lbs boost).

So far, I plan on about 9deg. around idle, about 32deg pushing hard, dropping to 22deg at high boost and RPM. Suggestions from anyone with experience in timing curves on the A-series would be greatly appreciated.

On a separate front, my wife just bought my Christmas gift(which I can't play with yet!!! but she'll never know I snuck into her closet and played with it while she was out of the house this weekend). Its a direct tie-in to Lake of the Ozarks. A nice big-screen GPS that will navigate me along the secondary routes and point out exciting Points-of-interest along the way. Wouldn't want to miss "another roadside attraction", like the world's largest ball of string or the museum of crochet while rushing off to Spridgetland. And I can enter waypoints for every spridget I see rotting in backyards and driveways as I cross the US next spring, shopping for the next checkbook hemorrage.

Glen Byrns

 

[aeronca65t]

Many of us here are interested in your success with the Megasquirt system.

You are blazing a new trail with this stuff and I know many of us are interested (me, for sure!)

The high RPM timing retard to 22 degrees sounds good (because I think it is similar to other turbo engines). For safety's sake, run that thing somewhat rich at first (or you may hole a piston).

I guess part of the issue is figuring where the "threshhold" to start that retard....maybe 5500 RPM? 6500? It's hard to know.

Hope you have good luck working out a "map" of the mixture/timing!

 

[Morris]

Again... way to go Glen!

Did you burn out your wide band sensor by forgetting to plug it in before starting the engine... 'cause I wouldn't know anything about that /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

Ps. I am on number 3.

 

[racingenglishcars]

When I was at the university we used a Mini 1275 with the ÅKM head as a test engine. The boss wrote up a theoretical advance diagram, though only up to 1 bar. I can try to dig it up.

 

[racingenglishcars]

Here it is.
n is the engine speed in 1000s rpm.
x-axis is manifold pressure in bar.

 

[Glen_B]

Thanks Donn,

The graph concerns me a bit. I could extend the curves to get guesses at boosted values, but the non-boosted values in the table don't look reasonable. The advance values look higher than suggested values from Vizard's book. 50deg. at 4000RPM and .4atm? That seems like a lot of advance. Was this curve generated for an A-series engine?

Glen Byrns

 

[racingenglishcars]

It was generated by the engine control group at DTU from data obtained on a 1275 7-port mini engine and using theoretical engine characteristics as explained in the engine control courses.
https://www.oersted.dtu.dk/English/research/au/ecg.aspx
https://www.iau.dtu.dk/engine.html
https://www.iau.dtu.dk/~eh/ecg.html
https://www.iau.dtu.dk/~eh/ecg_proj.html
The curve is included on one of their test engines. (The other is a diesel)
~ test engine ~ ~ console ~

That set of curves shows 50 deg at <u>5000</u> rpm at 0.4 bar. This is absolute pressure, therefore partially to nearly closed throttle. One could consider this part to be deceleration, where a standard distributor would be using the vacuum advance most. (partially open throttle so the advance supply hose is exposed to manifold pressure, and high engine speed for both centrifugal and vacuum advance, and high vacuum - low manifold pressure)
I didn't make the curve, Elbert Hendricks did, and he knows very well about Vizards book.

You could call him (He's an American and been in Denmark since around 1968) Control systems on Spark Ignition engines are his speciality and he's very good at it. (He also likes working with the Mini engine)
Their Mean Value Engine Model is a core technology in the Delphi fuel injection system as used on Opel cars since around 1990. (like my wife drives) (the timing expression is in Matlab Simulink 5.1 model form "MDTTiming.mdl" in the MVEM available on Elberts home site https://www.iau.dtu.dk/~eh/ )

 

[Morris]

Glen,

You may want to check this out:

https://home.comcast.net/~whaussmann/wmgb/wmgbframeset.htm

If you download his table, you will see that he is advancing spark 47° at high rev low map.

I used a similar excel spreadsheet to create my map, and it had me advancing 55° at high rev low map. I chickened out and retarded that number a bit. I still have a little work to do on my spark map, but other projects *sigh* keep me away from the fun stuff.

When I get to work, I will see if I can dig up the Excel spreadsheet I used and send it to you. As I recall, it can generate maps for turbo'ed cars as well.

Morris

 

[Glen_B]

Thanks guys,
I guess I'm just surprised at how much advance an engine would like to have that it is usually denied due to the limits of the centrifugal advance system on the conventional engine. Fear of consequences of the "maximum" advance force you to use too little advance at most throttle settings. With the Megasquirt you can actually consider using the best advance for each situation.
For my turbo application, I've always limited my dizzy advance to ~28deg. to prevent ping at high throttle/load. Obviously that also meant that where 50deg might be best, 28deg was the best I could hope for. Now that the world's my oyster, I'm trying to figure out how best to enjoy it.
I found and used Werner's website quite a bit to set up the Crane trigger but had missed the timing spreadsheet. Thanks!!

Glen Byrns

 

[Morris]

I found a better spreadsheet than Werner's and posted it on my website for ya'. You can download it here:

https://www.electrongun.org/hotrod/Ignition.xls

This one is set up for calculating boost retard, too. It used to be readily available on the MS forums, but it disappeared for some reason.

For those of you viewing this who are not Glen or Donn, Lemme just say that switching to computer controlled ignition has increased the overall performance of my car better than all other mods combined. As Glen says, it allows you to set your ignition advance to the best possible number for the specific driving situation, rather than just what will keep your car from blowing apart at WOT. I highly recommend it.

 

[Glen_B]

One look at the table tells you why a computer controlled engine will get better mileage, lower emissions and better power. Most every dizzy will go from 5-10deg BTDT to 28-38deg BTDC all in by about 3.5K. NOT what the engine really wants under so many conditions. This entire process has been a tremendous education.

Thanks a million guys, I'll be entering one of these maps for this weekends trials.

Glen Byrns