m/t ecu in an a/t dsm?

[ChameleonLizard]

I was curious if I could put a manual transmission ecu in my automatic 91 gst. I already have the cams and injectors out of a 5-speed laying around. I was going to slap a 14b in as well to get away from my tiny 13b. But i was wondering if it would screw up my car getting the ecu from the 5-speed as well. Basically something that would answer my question is knowing whether or not the ecu and tcu work together.

 

[btrux06]

i think the only difference is the injectors so if you use the 450s and 14b turbo and cams and 5sp ecu it might work out, but not 1000p ercent sure, the tcu and ecu dont work together, so i think that will be ok, and next time dont post this thred 4 times, thats just not fair and cool, and against the rules of the forum not to mention

 

[ChameleonLizard]

Yeah, that wasn't done on purpose. Everytime I went to submit the thread it would come up with an error and I would hit back. The forth time it thanked me for posting. Then I checked the forum and lo and behold all the errorous submits were going through. It's beyond me but I do appoligize.

 

[kpt4321]

There are a couple differences between the A/T ECU and the M/T ECU. The two you have to worry about are the injector sizing difference, and the base fuel pressure difference. If you want the M/T ecu to run correctly, then you need 450's and the correct base fuel pressure (37 psi). Stock AT fuel pressure is 42 psi, I believe.

 

[btrux06]

the ecu does not control the base fuel pressure, do u see any wires coming out of the regulator. how ever yes the auto regualtor runs at 42 and mt runs at 37, so the ecu does run the 4 injectors differently causs it will assume that your base fp is at 37 with the mt ecu, so in return your car will run a little bit richer causs you will still have the higher 42 psi regualator on the rail, unless you swap that out also. which if u have access to that should work out

 

[TURFNNSURF]

I swapped out the AT ecu for a MT ecu when I did my head upgrade from TurboTrix. I also put in MT cams, 450cc injectors and a walbro 255 fuel pump. As far as the TCU goes everything works perfectly, because as stated before they work independently of eachother. The only upgrade I didn't do at the time was an AFPR to control the 255 pump. My fuel trims with the 255 pump were all maxed at 139.8% (lean condition) even though my stock fuel pressure regulator was being overrun.. Shouldn't I have been running RICH not LEAN with the extra fuel from the 255?? This I couldn't figure out?? Anyone got any answers for that one?? After finally installing an AFPR set at 40psi base fuel pressure my trims changed to L=139.8% M=118.3% H=121.3%.. To this day i'm still puzzled by those trims.. Finally after getting an SAFC II and adding 18% at idle and then +12% from 1600rpm to 7600rpm my fuel trims are almost dead on "Stoich" at L=102.3% M=98.4% H=98.4%

Sorry to babble on but if my experiences can help others and also get me some answers in the process then that is what this is all about...

 

[kpt4321]

That was probably due to a hacked MAF.

Obviously the ECU does not control the fuel pressure. The point was, the MT ECU is programmed for a fuel pressure of 37 psi base, and 450 cc/min injectors, while the AT ECU is programmed for 42 base fuel pressure and 390 cc/min injectors. If you do not make the appropriate fuel pressure changes, then the fuel delivery will not be correct.

 

[btrux06]

good said, and turf, its better to tune to knock and timing, o2s arent that accurate and fuel trims work off o2s so its not best to tune to fuel trims, a example is my cars 02s are way low at wot, .7s, and my fuel trims are at 139, but cars pulls perfect, little to no knock, timing increase into 22, 23 range at 19 psis, icant figure out whats with the low o2s but just a example to why u shouldnt worry about o2s as much as knock and timing.

 

[kpt4321]

Originally posted by btrux06
o2s arent that accurate and fuel trims work off o2s so its not best to tune to fuel trims

Can you please stop spreading misinformation?

O2 sensors are designed to work accurately ONLY around a 14.7:1 A/F ratio, and they are very accurate in this range. The fuel trims and O2 trim (short term fuel trim) are both very accurate representations of your A/F ratio in closed loop, which is at cruise and idle.

Fuel and O2 trims are the absolute BEST way to tune your lo throttle, low load settings on the SAFC, MAFT, VPC, whatever.

They are very accurate, you just can't refer to them at WOT because they are not taken into account there.

 

[luizdiefenbach]

That was probably due to a hacked MAF.

Obviously the ECU does not control the fuel pressure. The point was, the MT ECU is programmed for a fuel pressure of 37 psi base, and 450 cc/min injectors, while the AT ECU is programmed for 42 base fuel pressure and 390 cc/min injectors. If you do not make the appropriate fuel pressure changes, then the fuel delivery will not be correct.

I made some calculations and if you have an Auto 1G and install a Manual ECU, you can simply raise your base fuel pressure from 42psi to 49.26psi , and your 390cc/min injector (now at 49.26psi) willl flow exactly as the 450 at 37 base pressure.