Getting rid of ECUs

[opethmike]

With my current EFI setup, Megasquirt controls fuel and the idle air control valve.

As such, can I get rid of both the Lambda ECU without issue? I need to keep the idle ECU as that still controls my vacuum advance solenoid.

[DMCMW Dave]

The vacuum advance solenoid is only controlled by the idle microswitch. The ECU does not have to be there.

You can move the vacuum source for that to the ported vacuum that is used to open the evap can, then you could eliminate that solenoid. I don't really understand why they didn't do this in the first place. Possibly the ported Evap outlet came later and they didn't bother to engineer a change.

[opethmike]

You know, that's a really cool idea. I think I will do that. How about the lambda ECU? Any reason to keep that?

[David T]

If you are going the "whole nine yards" with the Mega-Squirt you don't even need the ignition ECU. In fact, the ultimate would be coil packs and you can do away with the distributor and the coil too. You can remove the ballast resistor, the bypass relay, most of the vacuum system for the control pressure regulator and vacuum advance. You would still need the RPM relay to run the fuel pump unless you run it directly off the M/S ECU. You would have to find a signal to run the Tach. Obviously you no longer need the Lambda ECU or the idle ECU and all of the associated wiring. You may still want the idle and WOT micros unless you use a TPS (Throttle Position Sensor). Probably would make sense to make a whole new wiring harness for the engine compartment.
David Teitelbaum

[opethmike]

Hey Dave!

I have only gone fuel control at this point. I wanted to do one thing at a time, so to speak. My fuel conversion is complete and running very well at this point.

My current goal is to clean up what I don't need in terms of ECUs and wiring.

So you and Dave S. have both confirmed that I can get rid of the lambda and idle ECUs. I will do so this weekend. That will tidy up the ECU compartment quite a bit, and help me locate the MS ECU a bit more nicely.

The idle and wot micros are long gone. I really want to get rid of the unnecessary wiring in the engine bay. It looks terrible with all of the no longer used K-Jet connectors lying around. Not to mention it would be a great time to relocate the big bundle of wires that go over the intake manifold.

-Mike


If you are going the "whole nine yards" with the Mega-Squirt you don't even need the ignition ECU. In fact, the ultimate would be coil packs and you can do away with the distributor and the coil too. You can remove the ballast resistor, the bypass relay, most of the vacuum system for the control pressure regulator and vacuum advance. You would still need the RPM relay to run the fuel pump unless you run it directly off the M/S ECU. You would have to find a signal to run the Tach. Obviously you no longer need the Lambda ECU or the idle ECU and all of the associated wiring. You may still want the idle and WOT micros unless you use a TPS (Throttle Position Sensor). Probably would make sense to make a whole new wiring harness for the engine compartment.
David Teitelbaum

[David T]

If you have an automatic you need to leave one of the WOT micros to preserve the "Kick-Down" function.
David Teitelbaum

[opethmike]

I have a manual. Like I said, the conversion is complete, and the car has been getting driven.

[Ron]

The vacuum advance solenoid is only controlled by the idle microswitch. The ECU does not have to be there.

You can move the vacuum source for that to the ported vacuum that is used to open the evap can, then you could eliminate that solenoid. I don't really understand why they didn't do this in the first place. Possibly the ported Evap outlet came later and they didn't bother to engineer a change.I'd guess that, during deceleration, the bypass valves open so there is still a drop in pressure before the throttle plates (up to the metering plate) and, all be it relatively small, they wanted no vacuum at all reaching the advance...?...easy enough to check...

[DMCMW Dave]

Yea - put a vacuum gauge on the port and see what it looks like when you slam the throttle shut. Then decide if it's a problem to hang vacuum advance. Might be an emissions issue but I can't believe it would impact driveability.

Question - Does anyone have megasquirt running odd-fire ignition? I've seen it ton eagle even-fire conversions.

[Delorean Industries]

Yea - put a vacuum gauge on the port and see what it looks like when you slam the throttle shut. Then decide if it's a problem to hang vacuum advance. Might be an emissions issue but I can't believe it would impact driveability.

Question - Does anyone have megasquirt running odd-fire ignition? I've seen it ton eagle even-fire conversions.


Yeah I run it on my personal car but not on customers using a MSD 6A 6246. It is now discontinued. I picked up a dozen on discount at summit when they were cleaning out inventory.

The megamanual wiring suggestions are not very well developed and it took a little guess work on bugs.

[opethmike]

Yea - put a vacuum gauge on the port and see what it looks like when you slam the throttle shut. Then decide if it's a problem to hang vacuum advance. Might be an emissions issue but I can't believe it would impact driveability.

Question - Does anyone have megasquirt running odd-fire ignition? I've seen it ton eagle even-fire conversions.

Owen Malbec (spittybug) has his running full ignition and fuel on his stock PRV.

[Ron]

Yea - put a vacuum gauge on the port and see what it looks like when you slam the throttle shut. Then decide if it's a problem to hang vacuum advance. Might be an emissions issue but I can't believe it would impact driveability.
I'll move the boost gauge over to that port and watch it as soon as I get a chance just for curiosity...
Emissions gets my vote too...hard to imagine it being driveability when you're coasting ;).

[Spittybug]

Question - Does anyone have megasquirt running odd-fire ignition? I've seen it ton eagle even-fire conversions.

It took a while because there was a bug in the MS code that needed hunting down, but both Daryl (Darcom) in San Antonio and I are running full fuel and spark control on our cars. Now, I still have a distributor to actually distribute the spark, but the timing is fully controlled by MS. The centrifugal advance is tacked in place and the vacuum advance disabled. Being oddfire, we can't go with a wasted spark setup. That means if I wish to totally eliminate the distributor and go with either coil packs or coils on plugs, then I have to install both crank and cam trigger wheels. The MS unit is capable of putting out 6 ignition signals if you simply add the driver circuits (not hard). The key though is for the software to interpret both where the cam is and where the crank is so that TDC of #1 can be found to initialize the timing. After that the internal code is the same as it is now; defined by the small angle, 90 degrees for our engines. I have a modern coil (Accel Flamethrower) so I totally ditched the ballast resistors and cleaned up my wiring on the firewall and in the entire engine bay.

[Bitsyncmaster]

What I have found playing with the ignition advance is, with the engine advanced and all warmed up, you will have a hard time getting RPMs below 1400. It all depends on where you have your curb idle set and other engine loads. That is the one nice thing of the idle switch which I removed on my car.

[Spittybug]

What I have found playing with the ignition advance is, with the engine advanced and all warmed up, you will have a hard time getting RPMs below 1400. It all depends on where you have your curb idle set and other engine loads. That is the one nice thing of the idle switch which I removed on my car.

Not sure I understand that comment Dave. Why the problem? At idle, the advance is purely the static advance of ~13 degrees unless you change that. The RPMs set by the amount of opening in your butterflies (because you said warmed up, idle air should be off) can be made to be at virtually any level from stall to thousands.

[Bitsyncmaster]

Not sure I understand that comment Dave. Why the problem? At idle, the advance is purely the static advance of ~13 degrees unless you change that. The RPMs set by the amount of opening in your butterflies (because you said warmed up, idle air should be off) can be made to be at virtually any level from stall to thousands.

That info was for considering using ported vacuum. I think DMC ended up using the solenoid because ported vacuum may provide advance just cracking the curb idle. Then you will have problems holding idle speed.

[David T]

Shouldn't be hard to set up odd-fire if you use a coil pack for each cylinder. You just fire the coil packs in the correct firing order. The M/S shouldn't care about odd-fire or even fire. For the full-up system you also should include a knock sensor, pre and post O2 sensors, and if the system can handle it, a rough road sensor like on the Lotus V-8. By not having to deal with the distributor you can adjust each cylinder individually for timing. With enough outputs you can also run the A/C and the auto tranny through the ECU. It can get very complicated quickly.
David Teitelbaum