Jump to content
SAU Community

Can Overfueling Cause Detonation?

Abo Bob

By Abo Bob,
in Engines & Forced Induction

 Share

Recommended Posts

Abo Bob Grand Master

Abo Bob

Posted
Posted

Just trying to confirm something.

I got my car tuned with a z32 AFM that up until that day had been sitting in my garage for about 18 months and I've just found out had been unused but presumed to work for quite some time before then.

Anyway, the tune was good, it ran well but over a few days it seemed to deteriorate and I put it on a dyno where the air/fuel ratios went under 10 and it pinged.

I have since been steadily dropping the boost to now 7psi to stop it pinging.

The z32 AFM I believe maxes out at 4.5 volts.

I have seen it at 4.4 volts at 5000rpm with as little 10psi so it has been suggested that the AFM is dying or at least has something wrong with it.

My question is:

If we are right about the AFM showing far too much voltage for the actual air flow, it makes sense that it would be overfueling but can overfueling cause it to ping? Or is something else up?

Link to comment
https://www.sau.com.au/forums/topic/133359-can-overfueling-cause-detonation/
Share on other sites
Cubes Grand Master

Cubes

Posted
Posted

Mine was running in to the 9's (flat lines at 10 on the dyno as thats as low as the wideband reads) and there were no signs of detonation.

Sounds strange.

I gather you are running new fuel? Its quite possible the old stuff went off as it is 18months old. :O

Z32 at 4.5v. What sort of power are/were you making?

Mine hits 4.3v on the standard turbo running 10-11psi.

T04GTR Grand Master

T04GTR

Posted
Posted

well. it must of been making some power to reach the limit of the z32 afm.

to much fuel can cause pinging. not directly, but by carbon buildup in the cylinders. this glows and causes pinging. not detonation.

this is a pretty obviouse question but there isnt any air leaks is there?

also worth checking is the timing. if the cas hasnt been done up tightly it can move and the timing can change.

T04GTR Grand Master

T04GTR

Posted
Posted

in throey. if its dirty it will take more voltave to keep the element hot. given the same volume of air.

coz the dirt will be insulating the film.

give it a clean(if its dirty) this will restore it to the factory parameters. if that makes any sense.

also oiled type air flow meters are no good for longevity on any hotwire or thick film afm (z32) it oils up the element and the dust sticks to it.

Adriano Grand Master

Adriano

Posted
Posted

Wouldn't that mean less voltage?

If you had an air leak in the intercooler piping, or a venting bov opening, the afm voltage will go high, as will turbo speed.

in throey. if its dirty it will take more voltave to keep the element hot. given the same volume of air.

coz the dirt will be insulating the film.

Abo Bob Grand Master

Abo Bob

Posted
  • Author
Posted

Well with the old ECU, auto and stock AFM I was making around 255rwkw.

Then I did a manual conversion and put a pfc and Z32 AFM in. Tuned on a dyno that seems quite happy it made 300rwkw. This was at 11.8 A/F ratios I'm told.

Tried to run it on a dyno I knew and it ran 225rwkw, pinging and rich as feck. Didn't get too close to redline cos of the pinging.

Cubes - is that standard turbo but RB30?

Fuel is new and fine. 3 types tried.

I don't think there are any air leaks but I will check tonight.

The pinging doesn't seem to happen with heavy boost low to mid rpm, more like any boost high rpm, like over 5000.

My theory at this stage is, AFM tells PFC there is much more air than there really is, PFC puts lots of timing and lots of fuel in.

The only other thing I can think of is that the lambda sensor used to tune it was out and something is wrong with the tune although that wouldn't account for the pinging since it wasn't pinging at all when it was being tuned and on my test drive (and I gave it a good quality test drive).

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      Yup. You can get creative and make a sort of "bracket" with cable ties. Put 2 around the sender with a third passing underneath them strapped down against the sender. Then that third one is able to be passed through some hole at right angles to the orientation of the sender. Or some variation on the theme. Yes.... ummm, with caveats? I mean, the sender is BSP and you would likely have AN stuff on the hose, so yes, there would be the adapter you mention. But the block end will either be 1/8 NPT if that thread is still OK in there, or you can drill and tap it out to 1/4 BSP or NPT and use appropriate adapter there. As it stands, your mention of 1/8 BSPT male seems... wrong for the 1/8 NPT female it has to go into. The hose will be better, because even with the bush, the mass of the sender will be "hanging" off a hard threaded connection and will add some stress/strain to that. It might fail in the future. The hose eliminates almost all such risk - but adds in several more threaded connections to leak from! It really should be tapered, but it looks very long in that photo with no taper visible. If you have it in hand you should be able to see if it tapered or not. There technically is no possibility of a mechanical seal with a parallel male in a parallel female, so it is hard to believe that it is parallel male, but weirder things have happened. Maybe it's meant to seat on some surface when screwed in on the original installation? Anyway, at that thread size, parallel in parallel, with tape and goop, will seal just fine.
    • Kinkstaah
      Mistakes were made, my R34 Story

      By Kinkstaah · Posted

      How do you propose I cable tie this: To something securely? Is it really just a case of finding a couple of holes and ziptying it there so it never goes flying or starts dangling around, more or less? Then run a 1/8 BSP Female to [hose adapter of choice?/AN?] and then the opposing fitting at the bush-into-oil-block end? being the hose-into-realistically likely a 1/8 BSPT male) Is this going to provide any real benefit over using a stainless/steel 1/4 to 1/8 BSPT reducing bush? I am making the assumption the OEM sender is BSPT not BSPP/BSP
    • funkymonkey
      Jacks that fit under GTR lips that can reach the subframe?

      By funkymonkey · Posted

      I fashioned a ramp out of a couple of pieces of 140x35 lumber, to get the bumper up slightly, and then one of these is what I use
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      I wouldn't worry about dissimilar metal corrosion, should you just buy/make a steel replacement. There will be thread tape and sealant compound between the metals. The few little spots where they touch each other will be deep inside the joint, unable to get wet. And the alloy block is much much larger than a small steel fitting, so there is plenty of "sacrificial" capacity there. Any bush you put in there will be dissimilar anyway. Either steel or brass. Maybe stainless. All of them are different to the other parts in the chain. But what I said above still applies.
    • Duncan
      Mistakes were made, my R34 Story

      By Duncan · Posted

      You are all good then, I didn't realise the port was in a part you can (have!) remove. Just pull the broken part out, clean it and the threads should be fine. Yes, the whole point about remote mounting is it takes almost all of the vibration out via the flexible hose. You just need a convenient chassis point and a cable tie or 3.
×
×
  • Create New...