i was just at the yard the other day and got a couple ecus and a dash clock.

one ecu i got was a pm9. it came out of a hatch with vinyl seats. no option for cargo cover in back. i'm guessing its the std? anyways, from what i could find, thats what the pm9 is for. I couldn't find anywhere online that there are any differences between a pm9 and a pm5 other than one is 5 sp and the other is 4 sp. I have a stock 89 dx hatch(pretty much stock, it's got a d15b7 in it with all the b2 external stuff), so I decided to plug it in and see if it made a difference. I cannot seem to detect any changes in the way the thing drives.

Do you guys think it is ok to keep the pm9 in the car? Will it save some gas? will it hurt anything?

 

Why would you change out ecu's if your car is stock? Leave your stock one in there, it's obviously made for it.

 

A little something called curiosity, that's why.

So I've put 50 miles on it, I don't feel too much of a difference .
Does anyone know what the differences are between the pm9 and 5?

 

the pm9 is from the std, it has a less aggressive map than a pm5. pm5 is better. + the pm9 is for a 4 speed :/

 

I put a pm5 on my standard and I ran better. Not more power but it idles a whole lot better. Just smoother.

 

yes, i knew it was for an std 4sp, but it seems to run fine...

Maybe it's psychological, but it did feel marginally more sluggishlike and a tiny bit more rougher... maybe because it's using less gas?? I dunno... anyways, it at least works. I'm changing it back now.