I took my car to the track today,
13.11 @ 101 with a 1.75 60 foot.
shooting for 12's but ran out of juice.

Anyways, I shot nitrous straight off the line in one run I got 98 knock counts!!!
The wideband was pegged out on the rich side (9.94).
Would these most likely be false counts or can an extremely rich mixture cause the sensor to go off?
Do I need to lower my timing?
The Nitrous Master mind is tasking about 4-6 deg. out when spraying as well.

 

U need to find out exactly what was going on when the knook occured?

Was it immediately off the line, or once the nitrous was engaged.(from the post looks like u hit it when it went green)

That much knock, your getting it from whatever you did(provided u have little or next to none when not spraying)

I would heartily suggest backing down to a known good tune NA only and then working on the nitrous end of things. Start out with a 50 shot and work your way up progressively.

9.94 to 1 is too rich on best power for anything running on pump gasoline. This could very well be whats causing your knock if its happening at the big end of track.

I would more than likely work out a full throttle prom for the nitrous rather than try and rely on timing being pulled by other means or run a bin switcher and swap bins when u spray.

later
Jeremy

 

The knock counts go up contiunously down the entire length of the track. I had one after the burnout, off the line with nitrous they just shot up. It only did it with the n2o flowing. The NA tune is pretty good but kinda rich in PE, as far as the timing goes all the tables and such are left stock, that is why I am confused.

 

How much timing did the ECU pull out from knock? 150 shot on a 230 hp engine is quite a lot, but it's not my engine. Basically, you're filling mostly with N2O and the jetted fuel at that point - the engine doesn't increase (much) the amount of stuff it takes in, just gets more stuff that makes more power. I'd bet on a MAF car (which I can see that you're not) the MAF g/s would go down quite drastically at low RPMs - actually driving down LV8 and giving more timing.

I've never heard of excessively rich causing knock. I'd also think it would be quite hard to knock in such a rich condition - that is if it really is that rich, or whether the N2O can't fully burn in the time allowed, and fudging with the sensor. But, I'd put my money on the N2O kit manufacturers just playing it safe, and "mak'in it really fat, and tell'm to pull some timing."

My suggestion would be to try 4-6 degrees less timing and see if it goes faster down the track. If not, fuggetaboutit.

 

The ecm was taking out timing anywhere 11.4-2.5, varying the entire run.

 

What did the plugs show about the situation?.
EGTs?.

Something might be drastically wrong, and I'd suggest just short passes until you get things handled. Once you start hitting the K/S you ought to lift, IMO.

 

I can.
There are several things that can happen when running really rich. One, is masking the acoustic signal so that the K/S completely misses hearing any knock. Adding so much fuel that the CR is effected, and that'll help form detonation. Those are a few reasons why I yammer all the time about running the least amount of timing consistant with best performance, since that'll help keep folks out of the too rich with too much timing scenarios.

 

Yeah, I guess if it goes in the cylinder as liquid fuel... But that's approaching hyrdolock, hehe (not really). Does vaporized fuel count in the whole "actual" compression ratio (I'm not sure, I'm asking on this one - and if so, how much)?

Maybe the fuel isn't distributing evenly enough for the N2O, and one or two cylinders is taking a beating. Definitely pull plugs. But, at such a large shot, you're probably going to be building another engine soon anyway...

 

To be honest I didn't look at the knock counts until I got home. I recorded every run so I could review them.
I know BIG mistake.
I was more concerned with the AFR. When I saw it was sooo rich and the fact that I was running stock timing tables and the NMM taking timing out, I just didn't think it would of been an issue.
I will go pull a plug or two and see what they look like, I know it is probably too late.

Thanks for your opinions guys I appreciate the input.

 

well here are the pics of the two front drivers side plugs
(easiest to get at) These are one step colder R44TS and are gapped @ .030 thes only have a few hundred miles on them.

 

#2

 

These just have a slight tan mark. I don't see anything that would signal 100 knocks in 13 sec.

 

The combustion process starts when the intake valve closes, and the spark only cascades an event already in progess. The fuel starts entering the combustion chamber, by being dribbled/ sprayed an intake valve that's already at 600dF or so. So there's very little droplet sized that makes it past the intake valve. We're not talking about much of a change of CR, but with it changing the dynamics of the process, it does matter. ie look at how one cures detonation, you generally have to take timing out a lil before the detonation point, or start adding fuel, ahead of time.

IMO, the fueling answer for running NOS is using Propane. That has the same **response** since it's also a gas.

BTW, if you look at some single plane carb manifolds you can see how fuel forms paths across the bottom of the plenum floor.

 

Grumpy,
whatcha think of the plugs?
Is pointless at this point?

 

After reviewing the bin I was running I found that I was mistaken. I actually had timing added in the spark tables. I would bet farm that this is the origin of my knock.

 

Just to ease your mind about excessive rich raising the compression ratio by much, let me put out a number --> 0.1 grams of fuel per intake stroke would make an extremely rich mixture. That's about 0.14cc. That's about 0.02 CR change. That's assuming liquid state - not sure if vaporized fuel makes as much difference.

 

It is an intresting idea, but I don't see that causing the knock I am experiencing.
Maybe if I was running on the ragged edge, but not likely here.
I think it is caused from my timing.