seven

Hi Guys,

I need to fit an autobox to a FC3S, but the original ECU has been long gone, is there any other way to fit the box without this ECU? It is currently running a manual box with a microtech ECU instead. Pls advise.


Thanks & Best Regards,
S.W

maxpesce

You can run w/o the Trans ECU, But in doing so you will only get the LEAST agressive of the 4 possible shift maps and the TQ Conv. lockup probably won't work (not sure if te FC TQc lockup is electronicaly controled like the fd's) - Find and apropriate ECU to control the trans & run it piggyback w/ the Microtech.

weaklink

Max, please elaborate on "least aggressive shift map" and also when I shift into S, or L from D, I get an engine braking effect. Isn't this torque lockup? I run a PFC with the trans ecu "stranded".

Project84

There is a automatic transmission computer on ebay right now. I think it was around $30 with no current bids on it. Don't know how much time was left on it.

Did all FCs with auto trannys come with a lockup torque converter or just the S5 models? I have an 86 GXL with auto tranny.

Thanks

weaklink, when you down shift, you get an engine breaking effect because the gear you are selecting is going faster than the engine is going. Think about going from 4th to 2nd in a stick shift car. What happens to the RPMs? They go way up near red line and since that gear is already maxed out in terms of speed, the engine will slow down. Its hard to explain, but it all has to do with gear ratios and speeds and stuff. Lockup as far as torque converters works like this. Torque converter is bolted to the flywheel. So the flywheel rotates the torque converter. Fluid in the torque converter starts moving, and the fluid flows through a turbine wheel. This causes the other half of the torque converter to move. This other half is attached to the tranny, and causes the tranny to move. This motion is less efficient then a clutch/flywheel assembly because the fluid in the torque converter never moves as fast as the flywheel. A clutch moves as fast as a flywheel. So, someone invented a lockup torque converter, which mechanically clutches the two halves of the torque converter together under certain conditions, which eliminates the loss of efficiency. Lost yet?

weaklink

no i get that. To verify lockup (during coasting) in the shop manual it refers to engine braking, not after a shift though, but definately should have engine braking when decelerating after 62 in 3rd with throttle opening less than 1/8, which I do. I see the different maps there too, but they look functionally the same except for slip lockup.

weaklink

ok I checked on the tranny $75-still a good deal, but the guy is in Hawaii. How much to ship that beast???

maxpesce

I was talking about running the Trans W/o The trans ECU at all, The only thing the main ECU controls re the Auto Trans is "Torque Reduction" during the (retards the spark) shifts and it tells the tECU when HOLD is engaged (why this is not directly a function of the tECU IDK ask a Mazda engineer). On an FD the Lock-Up function is both Mechanically & Electronically controlled and varies depending on if HOLD is engaged or not (w/ Hold on you get much more engine braking as theTQc stays locked up down to aprox 1500 rpm). I believe on the S5's the Lock-up is purely mechanical. I don't know what the FC shift maps look like but on the FD the Part Throttle upshifts occur @ MUCH higher RPM in S&L & in D the trans starts off in 2nd at anything less than 50% throttle also the stock eCPU will declutch the AC compressor on throttle tip in to improve throttle response. (Does this on the 5 speeds also) Also I miscounted the possible Shift/LockUp Maps maps as there are 1 each for D,S,L, another for each when the Trans Fluid & Water temps are low (Raises part throttle shifts & lowers Max rpm upshift to aprox 6k to limit trans oil press) and one each for D&S w/ Hold engaged (no "Map" per say w/ L-Hold as you only get 1st gear in that config No Shifting!)

weaklink

I misread the original intentions of the thread, sorry. For clarity's sake I researched this a bit further in my shop manual. Engine ECU sends Map Sensor input, slip lockup off signal, torque reduced signal, idle signal. Signal for the hold switch comes directly from the hold switch (pgs k38-39).

maxpesce

I missed that - so How come the Hold Function dosen't work w/ the PFC installed as a stand alone? hmmm

weaklink

my guess is that any time any tranny error codes are thrown the hold function is lost. hold light flashes then like a CEL.