I believe I am getting some level of detonation and would like to know if my ECU has been retarding my timming a bit. I don't think it is a bad knock sensor. For one I have no code. Two, when I run a race gas/pump gas combination that gives me a 96 or 97 octane level my timming seems to be normal and I make the power I should make. This tells me that I must be expierencing knock on normal 93 octane pump gas and my kncok sensor is doing it's job by retarding my timming.

It's not that my JWT ECU needs the race gas, it should be just fine on 91+ octane. So there is some reason my car is retarding the timming. How can I find out what is going on. Would an OBD scanner tell me this? Could I have a problem with getting feul to my cylinder and that causing me to run lean? And wouldn't running lean cause my knock sensor to retard my timming?

Any thoughts on my problem are apprectiated.


Mike

 

An OBD scanner will show what the timing advance the ecu is running. Outside of Consult that is probably the only way to see actual timing advance.

 

Yup an OBD-II scanner would probably be the best choice. Not that expensive from what I read and works on a PDA

 

That is what I thought, but will the readings show if the knock sensor is retarding my timing? Sorry I have no expierence with scanners. Also, do the 95 production maxima and I30 use OBD-I

 

I have read that JWT programs ECUs for turbo'd Z32s strictly according to air flow and engine load, and knock sensor input is ignored. I read it on the internet, so it must be true. Just kidding, but the source is knowledgeable and pretty reliable. What they do for NA ECUs I do not know.

 

got a laptop? http://www.obd-2.com/ that is what u need. it is some cool stuff man

 

Ok, I got a acess to a scanner. It's kind of a universal cheap one, but I don't know anything about them. I can't read my knock sensor but I can read the spark advance. That should be able to tell me the advance in timing correct? But what I need to know is how much it should advance underload. The read out gives 0 at idle and will change under load, but I don't know what the correct change should be. I hope I am making my self clear....

 

I have a Techtom MDM-100. The timing is constantly changing so its almost useless unless you can graph it someway. At idle, mine runs 11-15. Cruising, it goes as high as 45. Can't remember what full throttle is, but I think it jumps around quite a bit at full throttle. It's hard to see at any given point if your running the correct timing or if it's being pulled back.

 

so my spark advance won't be a way to tell me if my timing is being pulled back. Do some OBD scanners show kock sensor readings?

 

The auterra dyno scan that I have doesn't show the KS input. However I know that autotap has this feature, but I don't know if its available for nissan/infiniti's though. However I'm sure you could datalog with any scanner and then compare the timing advance curves vs TPS vs MAF vs RPM to get a baseline.

 

But if I don't know what the correct advance should be then it does me no good.

What about the hp curve on a dyno graph? Would the curve get real erractic if my timing was being pulled back?

 

That is a good question I've done pulls with my ranger and my dad's 5.0 explorer. Now for some reason his explorer pings on 87 and rarley on 89. During one of the dyno pulls I did I hear some detonation so I let off. The curve had a big dip in power around the same place where the knock occured. However I datalogged a WOT from 10-90mph and I couldn't see evidence of knocking but I heard it. His engine doesn't have a KS however so the timing advance curves were pretty much the same in each gear. My advice would be to log timing advance vs TPS vs RPM, after a while you'll get a feel for how much timing the engine is running per rpm at a certain throttle %.

 

After thinking about this I don't think it makes a difference if I do all of this because I can't do anything about it.

This is what I was thinking. I am running a JWT ECU and have found that I run better 1/4 times with race gas, not just a little but somwhere around .2. That made me think that on pump 93 octane I must be gettin some knock which causes my knock sensor to tell my ECU to retatrd the timming. So on 96 or 97 octane I don't get knock and I am able to run at full available timing, thus faster times.

So even if I find out that my knock sensor is retarding my timming on 93 octane there is nothing I can do about it. I can't run race gas all the time. This all assuming that my knock sensor is in good condition, which I have no reason to believe it isn't.

I considerd for just doing the resistor mod and removing my knock sensor all togther, but if on 93 octane my ECU is having to retard my timing because of knock then with out a knock sensor i will get knock

I just want to be able to run as fast on the street as I do at the track.