Pre 89 ECU rev limiter A/T vs M/T

[Devin LeBlanc]

My car is automatic so currently I am using the 7MGT A/T ECU.. I am wondering if the rev limiter is higher on the manual ECU.. I have used the manual ecu with the automatic wiring harness before and it worked flawless so please don't say they are not interchangeable. However when I was using it I was not able to test the limiter on it I was working on a lean problem so just swapped out ECU's to make sure mine wasn't bad.. Anyways, hopefully someone can answer my question!

Thanks

 

[3p141592654]

Rev limit is set by the engine, not the tranny so they are both the same. If you want to increase it, you need to find one from a car with the 6M crank, unless that's what you already have!

 

[Devin LeBlanc]

I have a 6M crank so my rev limit is already higher correct?

Thanks

 

[Moy]

3P, I think he's talking about if there is a difference between A/T and M/T ECU's and their respective RPM limiters

 

[Devin LeBlanc]

Correct, Just wondering if the limiters are the same RPM weather its a auto ecu or manual Ecu..

 

[3p141592654]

I guess I wasn't clear, but I think he got it anyway. There is no difference in rev limit between A/T and M/T ECUs. After all, the tranny has nothing to do with the max safe engine speed.

The only rev limit difference between ECUs is for the 6M vs 7M crank. He has the 6M ECU, so he already has the highest rev limit (6800 rpm is where the ECU cuts the fuel with 6M crank).

 

[Devin LeBlanc]

lol, my tach must be off by about 400 then.. Unless the ECU Im running is out of a car with a 7M crank.. I bounce off rev limiter at like 6400.. My car is originally NA.. I am NA-T setup but got the wiring harness and ECU out of another car.. Still pre 89 however with yellow plugs.. I have a Manual ECU out of a car that I know had a original 6M crank motor in it.. Maybe ill try that one and see what my limiter is

 

[3p141592654]

All the yellow plug ECUs I've looked at have been 6800rpm.

 

[Devin LeBlanc]

I just did a bunch of reading, and it seems that the rev limiter for 6M is 6500 and the limiter for the 7M crank is 6200

 

[3p141592654]

No, that is the redline on the tach. The actual rpm limit in the ECU is 6800 for the 6M crank.

 

[Devin LeBlanc]

hmm, Well I start bouncing and banging off the rev limiter at 6400 RPM.. I will however do a log on the SAFC to see the actual high rpm

 

[3p141592654]

Be careful your SAFC sample rate does not influence your result.