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I gotta take a MegaSquirt.

1206 Views 4 Replies 4 Participants Last post by  82MKIILtype
Just curious if anyone was currently using a MEgaSquirt..and if they are, what tuning issues they have had with it... also.. how did you handle timing?
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Funny, I just tried to revieve an old thread in the engine section on this vary topic. I got nuffin. Maybe old threads are ignored or nobody actually had any new info to add. I dunno...

Anyway, what are you planning to use the MegaSquirt for? Personally I am thinking about using it to fuel a 5M turbo 82 and possibly an 84 dirt tracker. I think tunning the cold start enrichment will be a total pain in the A$$ 'cause it has to be started at cold soak conditions. It will take a full winter of screwing around to get it set properly. I don't think that the rest of the tuning would be that big of a deal as long as I get a wide band O2 sensor in the original setup and use the data logger.

Ignition on the 84??? I got no clue. I wanted the same info. I know that the same people who did the MegaSquirt are working on a MegaSpark but I think it's still a ways off. There must be a way to keep the Toyota ecu reading engine sensors like just putting resistors equivilent to injector resistance and grounding them all. Maybe by altering the coolant sensor you could force the ecu into open loop operation and ignore all the sensors? (might hurt performance?) I'm looking into this hard core but might not get around to actually doing it untill spring. I would love to get some input on this from others... but I'll figure it out on my own if I have to. It will just take a bit longer.
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My 82 race car has been modded by its original builder in ~1994 and by the last owner in the last few years. I'm still trying to figure out all the little mods they did.

Anyway, one thing they did was to wire in a potentiometer (0-2000 ohm variable resistor) in line with the coolant temp sensor circuit. Adding resistance makes the ECU think the motor is cold so it adds more fuel.

The car will not start when cold (say less than 50 deg F outside, engine cold) unless that pot is turned up to about 1000 ohms resistance to richen up the mixture. Once engine is warm, it will start with 0 resistance added. In the summer with temps above 75 deg F, it started ok with 0 resistance added. I need to check and see if the cold start injector is working properly.

Keep me informed of what you find out.
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Just curious if anyone was currently using a MEgaSquirt..and if they are, what tuning issues they have had with it... also.. how did you handle timing?
i'm kind of curently using it, still havent gotten the car to start though (but i finally know what's wrong, i can't wait to get back home to it).

mike l. (if he uses these boards) will have to tell you more about tuning issues. it ought to be just like tuning any other standalone, but probably a bit simpler. it's a very very bare bones, simple system. from stories heard on the mailing list, it doesn't take long for most people to get their car tuned pretty well, but i'm sure we dont hear about tweaks people make for a while after installing one.

as far as timing goes, i had a weird problem and don't know the cuase of it yet. i installed the MS, and had a CEL. i wired a pot to the AFM and clt temp sensor. the CEL went away when i turned the resistance up on the AFM pot, which is sensible. in any case, the toyota ecu wouldn't spark without my turning the pot down to when i did get CEL. i'm thinking now that the CEL came on when the resistance was actually too low. anyone know how CELs are tripped in our cars?

i'm pretty sure the toyota ecu indexes timing with load. i think the effect of having an hooked AFM will be pretty bad since the 'load' calculation it must do will come from an air flow reading. i *think* mike l. was having trouble with this; he was getting poor mileage and he was beginning to suspect overly retarded timing. one possibility might just to hook up a dizzy from an '82, but, then again, that might not be ideal for a turbo car. i think if i had to use the stock ecu for timing, i'd leave the afm in there, and maybe use the map sensor that the MS uses to trigger a switch for the check connector to hold timing at 10deg under high boost.

other possibilities which would involve more work would be MegaSquirtnSpark or MegaSquirtnEDIS. you get a lot of bang for you rbuck with either of these... i think megasquirtnspark needs a standard trigger (like, 3 per rev, at x degrees before TDC), and will have one ign. output for a distributor. i havent realyl looked into it yet, but a locked up '82 dizzy and some signal conditioning might be all you need for megasquirtnspark.

megasquirtnEDIS is probably the better way to go-- it uses the ford EDIS system for ignition. for this, you need the EDIS crank wheel from a '91-'97ish ford 6 cyl motor that had EDIS, and the EDIS module. but this way, you get rid of the distributor. both of these units have limited testing; they are side projects that were developed by other parties. however, they are simple enough and the limited testing has all seen great results. the megasquirtnspark yahoo group would probably be a good place to get more info.

another possibility will be to wait for ultramegasquirt. it will have a better tested distributor/EDIS set up, and there's a good chance that if you are ok with using a dsitributor, the pickup from an '82 dizzy will be all you need for a crank trigger-- the board's supposed to have a built-in variable reluctance signal conditioner. it'll also have a wideband controller, with considerable effort being expended to get a reliable way to hold any AFR of your choosing under cruise and WOT as i understand it. it'll also have more i/os, and use a processor for which there is a good C code cross compiler. unfortunately, there's really no telling when UMS will come out. i believe the main focus right now is the wideband control/feedback.

for timing, i myself picked up a haltech ig5 off ebay a while ago. it cost be $200, so i've ended up spending about $400 for two separate units to control fuel and timing. bah. the ig5 seems to be compatible with our position signals after some conditioning. my plan is to use this for a while, in the meantime tracking down EDIS equipment and finding ways to mount the wheel and pickup, then trying megasquirtnEDIS, and then finally getting UMS when it gets here. i really cant wait 'till it does come out. it wont be any more expensive and everything'll be in one unit.

sorry i couldn't be of more help. if all goes well, after thanksgiving i can report back with more info on tuning.

megasquirt's a lot of fun.

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sorry i couldn't be of more help.
This is the most information anyone has had. :greatpos:

I Think I will definatly go ahead with the MegaSquirt on the 82 and just use the OEM distributor ect. I figure any off boost performance loss will be quickly fogoten when the turbo spools...

For the 84 Ummmmm I might try to find an 82 distributor assembly for the short term (it will switch right into the the same hole in the head right???) but with the increased compression I think ultamately a turbo might not agree with it. It's not a daily driver so I can take the time to play with it. :wink:

Time to start ordering a MegaSquirt! I'll try to keep you guys informed but my contract ends on th 28th so I might be relocating for a while and internet may be touch and go. (This just means I need to order the MegaSquirt before the 28th!)

Let the fun begin :dancin:
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