Mega Jolt Light Junior thread for a /6, Because folks have asked Options

[smdubovsky]

Good Dr,
The advance data for the SC I gave you was for the DISTRIBUTOR shaft. Needs to be multiplied 2x for advance at the crank (the bulb should turn on in your head now;) The SC goes from somewhere around 0-5deg BTDC (5deg ATDC if you leave the hoses connected) to around 38deg BTDC at 6000rpm (w/ no hoses). You're not going anywhere w/ 12-18 deg total advance at the crank;) It would feel like a 1.7L four...

When you multiply by 2, they look much closer to the 2.4-2.7 data.

You should set the max vacuum up for near perfect vacuum (0 psi). In overrun (max rpm, going down hill in gear, and taking foot off throttle) I could easily generate 28+"inHg in my old Jeep 4-banger.

SMD

[Dr Evil]

Ah, the degrees need to be multiplied as well. Nice.


I just spent $20 on a vacuum gauge to get the MAP. I wish I didnt have to, but I need the data points.

Thanks!

P.S. I am gonna fix it in my previous post for posterity

[Dr Evil]

Well that was a waste of $20 I didnt have (IMG:style_emoticons/default/dry.gif)

So I start the car and attempt to take readings, no joy. The gauge barely registers anything (as in it stays with in the 0 zone).

You may be wondering if I got a gauge that was of the wrong range. Well, ya considering I have no idea what range I am looking to play in. I wonder if the hose is plugged or otherwise blocked. I get light vacuum.

With out the vacuum data points I can not build a chart and I can not see how to progress.

Any ideas?

[lapuwali]

You can start with just the centrifugal curve. At worst, what will happen if the vacuum programming does nothing, is that you'll get poor cruise gas mileage and more emissions. This isn't going to be a "blow the engine up" kind of scenario.

As for what MAP you're likely to see, most engines with single throttle/plenum intakes and street cams generate fairly similar values. Typical MAP values will be 20-30kPa on the overrun (lowest value), up to 95-99kPa at WOT (highest value). Cruise is likely to be 45-60kPa. I'd start by adding in a bit of timing around that range, in the same RPM ranges you normally cruise (3000-4000rpm, most likely). Taper it off so that by 80-ish kPa you're back to the centrifugal curve.

Keep an ear out for pinging, and reduce timing in that range if you hear any. Having some real-time display of MAP while you drive would obviously be very helpful. Very easy with Megasquirt, but I have no idea if the MJLJ software displays anything.

[Dr Evil]

I have read and rearead the post on the MSEFI forum about genreating a start curve. They recommend that idle advance be limited, and that for every 1kpa of pressure drop .3 degree of advance be added. I augmented the latter buy limiting advance to 36 degrees due to the warnings that I have seen about going more thatn 38 on any of the /6 engines mentioned.

I will see if I can generate a table based upon what you have said as well, but tell me what you think about the one I made using the 77 S curve.

[Dr Evil]

Hey Dave,
Didnt you mention that I need to consider that the advance is added to the wheels offset or something like that. I know for the /6 the offest of the missing tooth is 60 degrees. Am I supposed to subtract/add to this figure?

Also, I notice in your chart maxes out at odd places. According to what I have been reading, and from what I understand from James, I need to return to mechanical advance after about 80Kpa. Thus, I should be maxed out with advance at highest RPM and lowest kPa, right? I am switching my above table a little bit to remove the 0kPa rating. Instead it will be max low at 20kPa.

As soon as I find some clarity on these questions I will program the unit and give it a go (IMG:style_emoticons/default/biggrin.gif) I started making my wires up today, the shielded cable is on the way, and I am fabricating the coil mounting bracket. Kind of exciting!

[DNHunt]

It's not the sixty derees I was referring to. If the sensor is 59 or 62 or any mounting beside 60 degrees you have to account for the difference. MS has aspot were that fudge factor can be added. When you get it started you need to put a timing light on it to find out if the measured timing is the same as the value reported in the software. If not you need to apply that fudge factor or manually reposition the sensor otherwise you timing will be off for the entire cure. Just think calibration.

The retard in the higher RPMs is to accout for higher piston speed as Jake explained it to me.

Dave

[Dr Evil]

O, I C.

Thanks man, that is a lot more clear. Luckily the toothed gear has adjustability.

[lapuwali]

The highest rpm/lowest kPa thing will require some fudging. The only time you're going to hit 20kPa or lower at all is when you lift off the throttle. The higher the revs when you lift, the lower the MAP value will be. You'll basically want to set the timing to some value that prevents backfiring, but that's about it. Other areas are basically never going to be reached. 20kPa at 900rpm, for example, will never be seen.

Basic ignition curve theory:

You see the advance rise as revs rise for a fairly obvious reason: the fuel takes X time to burn, but the time it takes the piston to move from, say 25dBTDC to 20dATDC gets shorter as the revs rise, so you have to move the ignition point earlier and earlier to account for this. At some point, OEM ignition curves go "flat". The reasoning here is that at some point as the revs rise, air velocity through the port is high enough that the turbulence caused by the incoming charge does a better and better job of mixing the charge, so X actually gets shorter, so more advance isn't required.

However, a flat curve is much easier to acheive than a complex curve with a mechanical distributor, so the flat plateau is something of a compromise. Some have found that rising steeply at low revs, then slowing the rise past that point, is actually more effective. Only experimentation will tell you what works with that engine. I'd say that rising a bit more steeply to your max advance by 3500 rpm will be more in keeping with traditional curves. Later, when you have more confidence with the system, you'll want to raise the lower MAP advance to well beyond 36 degrees. At lower MAP, there's little load on the engine, so it's virtually detonation proof. More advance here MAY improve economy, and can slightly assist response, and does reduce emissions. At 40-60kPa, you'll be cruising with very little throttle, regardless of RPM.

I would also rework your curve a bit at the top end. Drop the 5500 and 6000 bins, as, the curve can basically be the same as 4500, and make a 6500 bin and a 7000 bin, and retard the ignition at higher MAP by 15 degrees at 6500 and 25 degrees at 7000. This gives you a no-cost rev limiter. If you try to accelerate past 6500 rpm, the car will feel like it's falling on its face, and you'll back off and curse yourself for not paying attention to the tach.

[Dr Evil]

Dude, you are like an encyclopedia. Thanks a bunch. The rev limiter idea is brilliant! I'll get working on it as soon as I get back.

Also, I am gonna be posting a "how to" on making your own spark plug wires. I learned a few things that will save much time and money.

I had to order 25' of the shielded wire for the PIP, SAW, and VR. Do you need any for your conversion?

Stay tuned!

[wilchek]

Sounds like you are making some good headway. Keep us posted. Glad to see the computer worked for you.

[DNHunt]

Remember that you don't have to cover every MAP/RPM situation. Beyond the bondaries of the table the values stay constant so, you may not need to provide a value for 7000 rpms or 102 kPa or 20kPa. If they are the same drop them and use the bins where changes are happening the fastest.

Dave

[Dr Evil]

Thanks again, guys. Especially you James. Your write up was very well put and taught me things I did not yet know so I am very greatful.

Based on what you put in your post I augmented my chart:
-full advance by 3500
-add 6500 and 7000
-Subtract 15 from 6500 and 25 from 7000
- (later to come) more advance at lower MAP

Please keep the suggestions coming. Below is the newest curve, what do ya'll think?

[Dr Evil]

And the latest.....

I have everything wired up, installed and looking mighty fine (pics later). I adjsuted the timing wheel so that the spartk for #1 happens at -5ATDC as verified by timing light. And it will not run right (IMG:style_emoticons/default/dry.gif)

I need to verify I that I am doing the right thing regarding the coil wires. Here is what I got:

Firing order 1-6-2-4-3-5 (right?)

So the wires should be paired as 1-4, 6-3, 2-5 (right?)

At least I know that #1 is correct

[lapuwali]

Why do you have the advance so retarded for starting? I'd try TDC, or even 5BTDC.

What's "not running right"? If it's way too retarded, it tends to "kick" when you try to start it.

I'm trying to puzzle out the plug order problem. This is something I can do in my head on a 4, but I've never tried doing it on a 6.

[fiid]

Hey,

Your wiring looks right....

The crank does a full rotation every 3 firings on a 6, so 1-6-2 and 4-3-5 are exactly the same as read from the crankshaft or piston positions, so the pairings should be 1-4, 6-3 and 2-5 - just like you said.

[fiid]

As for the map - I don't think you'd ever need to be firing after top dead center... you probably wouldn't need to go past -10 or so (That's limp home mode for the EDIS), unless you are doing retard for rev limiting.

Other than that it looks basically right though... Have you thought about getting a knock sensor?

[Dr Evil]

Sorry, I guess I should elaborate. I was in a hurry to get out the door to pick up the little lady.

I did get the kick back, so I adjsuted some things and the best i can do now is a nice loud BOOM on at least one of the cylinders up throught the air box. I put it starting at -5 because that is what the manual said it should be at for idle. I can change this to 0 if necessary, but when it was origianly at 0 it was acting pretty much the same. I need to verify that I have coil 1, 2, and 3 wires going to the right wires on the coil pack.

[Dr Evil]

Also, my fuel air mixture is probably still off (IMG:style_emoticons/default/dry.gif)

[lapuwali]

I've seen no engines that start well with ATDC timing. 5-10BTDC is typical. The smallest I've seen for idle timing was 3BTDC on a 912, but the engine actually started better at 10BTDC. Which manual are you referring to that said to use ATDC timing?