My brother and I have been working on his 94 Si hatch for a while now and just recently got the LS swap all done and running... Well this week the car began running pretty rough and there was no CEL to tell us what was wrong. We had to fix over 5 CEL's when the engine was first swapped because of so many broken sensors etc. so we know they are all working fine now. So I figured we should try swapping in his old ecu (the p28) to see how it would run. Well the car seemed to run much better. The idle is much better and it SEEMS to be running great with the p28.
So I guess I've got two questions. Is the pr4 ecu possibly fried?
and will it be ok to run a virgin p28 on his engine?
Thanks

 

the p28 will run it ok until WOT.

 

Would it run lean at wot?

How bad is that for the engine...

 

well im just concerned with the ignition and fuel maps at WOT. i know they are different from b series and d series. plus the p28 is for vtec.

If you run lean then you can detonate.
when you are running lean your motor gets hotter. and the stock pistons can expand a little bit under the heat load and can scar the cylinder walls.

 

Ok thanks, I'll definately take that into consideration... My main concern was if the fuel maps were different enough to do harm to the engine. (seems like it can)
The CEL came on instantly (code 21, since vtec doesnt exist)... Do you think I should find another ECU or find someone to maybe remove vtec and change the p28 maps? (I'm new to this ecu stuff) Thanks for the help

 

id go prowling around for a LS ECU. infact i might still have mine laying around here somewhere.

 

That would be really cool man.
Anyone else have experience with this?

 

the only prob you would have is the vtec. check eng. light going on. but other then that, that ****'s the same way, I ran p28 on my hb all day long, (2 years) and still running strong.

 

i ran a virgin p28 on my gsr swap for awhile, when i finally got uberdata tuned in it the difference was quite significant. Im not sure if it's going to hurt ur motor, but it does have a powerloss with the less aggressive fuel map.

 

Thanks for the comments, I appreciate it.
It seems to be running fine (its my brothers car so I dont drive it as much as him of course) I am selling the ecu to someone and using the funds to get the proper ecu.

Someone has an ecu locally (p06 I believe) and he said its been programmed to a gsr fuel map... He actually let my brother plug it up to his car and drive around to see how it felt and he said it ran really good (with no CEL). So would this ecu be better than that p28?

 

if it were programmed with a gsr map it should have thrown a cel for vtec

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jarvis199 &raquo;</TD></TR><TR><TD CLASS="quote">if it were programmed with a gsr map it should have thrown a cel for vtec </TD></TR></TABLE>

Exactly. Unless the ECU was chipped to remove vtec, it should've thrown a code. The only advantage I can see from running a gsr prog is a higher redline, but that isn't doing you too much of any kind of good with your LS. Find a virgin p75 and chip away.

 

I dont know much about this stuff so I didnt think the fuel curve would affect vtec... There was no rev limiter on it either.
Guess I'll look for a p75.
thanks guys.

 

Btw, if you're planning on chipping, think of it as your last mod, or one of your last mods, because you'll be wasting your time if you just chip for ***** and giggles. The chips are much more effective with an engine that has a considerable amount of work done to it. Uberdata w00t!

 

I think I'm just going to buy another pr4 ecu, the car has light modifications so a chipped ecu probably wouldn't help much (if I'm wrong, correct me)... The other one we were using was for an automatic and threw the egr code and makes the car run like crap, so I guess its just F'ed up.

Thanks for the advice.