compression on the #4 is 10% less than the rest, the rest test good at 180psi

and im not new to this stuff either

 

sorry, just saw this. it sounds like there are about 5 marbles bouncing around in the intake right after the tb. so it comes from right behind the dash. when we were logging with the utec, at one point it recorded 4 knocks at one rpm.

with the added spacer and meth injection, i saw a huge jump in air fuel ratios

 

cylinders are ok, so we can move past that area then. that's good news

hmm....4 knocks wouldn't sound as bad as you describe it. I'm not sure how it displays the knock it logs. If that's 4 knocks PER rpm then i guess that would make good sense.

bad news is if you were detonating before and that's what caused the spark plug failure and he kept doing it then it probably damaged that rod bearing due to the excessive cylinder pressures. Now that knock you are hearing isn't the knock from detonation anymore, it's knock from the rod bearing.

After doing all that work i don't know why you are so resistant to detonation theory. I'm nto getting defensive, it's not my car so it really doesn't effect me but i layed out a very strong foundation of facts and what those facts could mean. They all lay back to possibly a fuel problem which would cause detonation which would destroy a spark plug.

The spark plug monster eating them theory doesn't apply here. I listed what causes spark plugs to be destroyed like that and told you what things could be tested but you want some other magic problem.

I think the other magic problem now is a rod knocking due to excessive damage. That's probably why it's happening even without nitrous now.

 

i already thought of everything you mentioned, but maybe ill have the injector flow tested anyway. i can almost guarantee its not an injector though. it only does it on spray, like has been stated a couple times already in this thread

 

Yeah, it is only like that when he sprays nitrous. Without motor, everything sounds perfectly normal. There is a ticking sound from the engine bay, but its the same ticking sound I've heard in multiple vq35de engines. Nothing crazy.


Although, my friend did use seafoam 8-9 months ago. He thought something had happened at that time. Since then he'd spray plenty of times with no knock issue besides the melting plug issue.


I agree with you that pre-det and detonation both cause excess heat which can melt/destroy the plugs. That said, I don't see how there would be an issue with the injector given the fact that it only happens when he sprays.

If the rod bearing was bad or going bad wouldnt that cause noticeable knock under all conditions and not just nitrous?

 

well, it does'nt really mean there is an injector that's bad but a lack of fuel possibly. By having the injectors tested you are just ruling out one more thing. Then if they are normal and you still think fuel issue (which is what i'm still thinking) then the wiring harness or ecu could be an issue. I've had wires back out of my injector clips and cause misfires WITH NO CODES. I know there are misfires by the way the engine was running so when i pulled hte plugs i had a bone white plug which meant it was lean. Checked the wires and found the issue. It was only misfiring under wot and again, with no codes....blew my mind. Took me 3 weeks to find that junk.

other things, i mis understood. I thought when you were saying now it knocks when he gives it gas i thought you mean normal non-nitrous driving. If it's only at nitrous i still wouldn't rule out rod knock but it's less likely.

I've had engines (granted these are race bikes but same concept) that idle normal with no noise then when i put a load on the engine it will start to knock. Reason behind this is the increased combustion chamber pressures with higher rpm and load. If the rod bearing is just starting to get sloppy it will present like this, then shortly after it'll start knocking all the time, then when your racer never tells you about it the rod decides to fly through the bottom of the block.

So now that i know it's not "knock" on normal driving giving it gas i would say that you are correct in it probably not being rod knock but that doenst mean it's not starting to go out so i would just pay close attention to it and see if it progresses. catch it early if it starts progressing to save the block.


oh, the question about being lean and only melting plugs on nitrous is because at normal driving you don't have an accelerant like nitrous that increases combustion pressures like crazy. That's like how you can drive with 42 degrees timing while in vaccuum but if you're on nitrous or boost you have to retard that timing because the combustion pressures would be way too high at that timing.

More nitrous=requires more fuel (not undermining your intelligence, just going through the facts). Therefore if for some reason that 1 injector doesn't increase it's fuel like all the others then that cylinder would run really lean.

 

Ya, its just a crazy situation is all. Melting plugs with no knock. Now not melting plugs, but getting crazy knock.

I haven't ruled out a rod tweak/rod bearing issue but it should be present in all motor driving when WOT as well.

Injector is a possibility, but why would it not be doing that at WOT all the time, not just with nitrous?

 

well, the onset of a bad rod bearing could be intermittant knock only with load on the engine or high rpm. It's a tricky beast.


umm, then you think injector don't think just injector being bad, also think it could be a wiring connection causing the issue. Mine was a loose connector that make good connection until high rpm when it would break up. I assume it was due to the amp draw through that connection.

Yours might not be caused by that. Yours could be the injector isn't supplying enough fuel when in nitrous. Maybe the injector is maxing out before it supplies enough fuel for the nitrous but it supplies enough for WOT without the nitrous. The reason for it only at certain cylinders is due to a bad injector or a clogged injector.

not to undermine your intelligence but i like to put numbers on things to make them make sense.

say fuel requirements WOT: 10gph
fuel requirements wot nitrous: 15gph

now pretend that 5 cylinders flow 15gph but 1 of them only flows 14gph due to a clog or something. So now it gives plenty of fuel for WOT, but when you need that extra 5gph for the nitrous that 1 injector falls short therefore it would be lean. *numbers are arbitrary

 

I guess thats possible. It just seems unlikely that it would be such a small blockage so that its fine under all motor but nitrous is starving.

Possible that the "lean" condition is causing the extra strain and the rod bearing is going too, i suppose. Tough to say at this point.

 

ya, very tough to say but if you aren't running a separate fuel filter you can easily get something clogged in an injector. They have very smal holes therefore all it takes is a very small particle. The stock screen on the fuel basket is crappy and only a "screen" not a true "filter".

So it's plausable that something is stuck in just 1 or maybe 2 injectors. Usually if you are getting crud in your injectors is starts with one and as it builds up it will start getting stuck in more. having them bench tested eliminates that variable.

Then i would check wiring connections. Mine would only cut out at high rpm under load. loose wire at the connect was all i had go wrong. easy fix.

 

I highly doubt its a wiring issue. That would be more erratic and happen with all motor in addition to nitrous.

Injector is a more plausible cause i think. However, the cylinder that has been having the problems is now a lower compression than the other 5 cylinders. I wonder if there has been some damaged cause to the rod/bearing

 

the car just hates nitrous, thats all it is

 

You'd be surprised about wiring issues. It's hard to tell until you have the injectors checked. Once you do that you will find out if you need to replace injectors or dig deeper.

If the cylinder has slightly lower compression it could be due to the piston rings. Extreme heat and detonation will wear out rings fast.

 

update,

the marble sound disappeared, two things changed, out of meth/water mix and hfc were installed. still on a rich 65 shot. getting meth/water mix to add that factor back in to see if the sound comes back to determine which one was the cause.

 

it was the cats for anyone interested

 

so the stock cats had failed?

that's a bummer but also great because it was an easy fix. i guess that backpressure was causing the lean condition that was eating spark plugs?

 

yea, they were backing up the system enough to cause heat buildup therefore causing preignition. fixed now though. except the hfc are very raspy

 

hmm, could be a combo of that and your exhaust. I have headers, tp, and borla and i haven't ever had rasp even though everyone says TP will always be raspy.

 

yea, idk, there doesnt seem to be a method to the madness when it comes to rasp cause ive talked to others with a similar setup to mine and they dont have rasp, but i def do, o well