Ok I have been reading for some time about lean spikes. And some thought process and questions out there; does this hurt my engine?
The answer is no it will not if its a spike.

So what is a spike?
A spike is nothing more than the air fuel going lean for a brief moment in time and then back down. Nothing more nothing less.

To be a spike it must return to norm very quickly. Will less than 1 second.

So what causes this to happen? With a wet nitrous system more times than not it has to do with 3 things. 1st fuel pressure drop in the stock fuel rail. Opening a fuel noid for a faction of a second you have no fuel pressure. Nitrous betting the fuel to the cylinder. ( tests have shown on a direct port with rails that does not happen). and 3rd, on direct port application, the maf sensor can actually see a stalled air problem at the engagement of your system, and the maf tells the computer to defuel.. Now this can happen on larger shots on nitrous.

So back to the spike. Some graph have been sent to me in an exploded format. Making this look like a large big **** problem. But any time you get one, click the graph over to time and see just how much time you are. Starting and finishing pionts I would say depends on the amount of nitrous. I would look at 13 - 13. Meaning the start point is 13-1 of your spike, and now back down to the other side of the spike at 13-1. This will be the largest amount of time. Again just a base to compare,
IF the nitrous leans outs and stays lean, get out of the pull and find out why... But that is not a spike. its a lean problem..

Just for discussion.

Ricky

 

I think it's great. It lets the motor know what it's in for.

I think an engine will survive going lean for up to 2 seconds provided the chamber and/or sparkplug is not already hot when the lean spike happens.

AFAIK the lean spikes happen just the same with MAF or SD, so I doubt the MAF is a factor at all. I've never worried about it myself (see above).

 

Ok, well what about heavily boosted applications (>8# seen at the time nitrous is added)???

I mean that is the situation I am faced with, thus the 'lean-spike' means a great increase in combustion cylinder temps that can cause detonation in the short term, which as we all knows means that once you detonate you need to reduce timing drastically over what would normally be allowable as well as a preferable increase of fuel to lower combustion temps... All a situation that is completely avoidable if you make sure the 'lean-spike' is either non-existent or minimal...

I am sure for some that spray off the line they won't run into this 'dangerous situation', but for me, I am bringing the nitrous on at 3000-4000rpm progressively, which means that I could see a lean condition all the way through 5000rpm when I am making over 10# of boost... In my situation a 'lean-spike' could mean the end of the motor if it goes badly enough...

That is why I like the safety features of the modern progressive controllers to 'see' such problems and deactivate teh system if it occurs, but in my case I am trying to engineer around it to make sure it does happen at all, or at the least have a plan to retard timing during activation ramp-up until I am certain that it is no longer lean before I bring full proper timing for power in... Which brings up a question:

In the Max2 setup there is a 'threshold' value for the timing retard features, I am assuming that the timing retard will not activate until that threshold is reached, but is that refering to the percentage of nitrous being introduced or the percetage of the 'window' in which the controller activates the nitrous? I assume it is the former, which means that if I set it for 10% for retard1 and 60% for retard2, then it would bring in retard1 at 10% of nitrous flow and retard2 at 60% of nitrous flow...

Now that being the case, is it possible to change the Max2 software to allow for a on/off threshold, in that I could activate say retard2 at 10% nitrous flow and deactivate it at 40% nitrous flow (for example)???

That would allow me to retard timing during this inital 'lean-out' and lessen the possibility of motor damage from a detonation event... I would have to imagine the power increase from the nitrous would more than compensate for any sort of power loss based upon pulling timing for safety's sake...

 

Is this a lean spike? lol.




Looks like I was alittle fat that day. That's back when I was playing with a single stage 200rwhp shot. Recovered pretty good for nothing but a Walbro pump. I have never been concerned with the lean spikes myself. If it was going to damage the motor I think it would have **** the bed along time ago. On a normal launch with the two stage 225 my lean spike is much smaller but it is a touch wider.

 

Can you get a lean spike from a dry shot?

 

yeppers thats a spike.
Thank you for the graph.
Ricky

 

If you've already built boost then your chambers are probably already starting to cook unless you're running a coolant, or pig rich like a lot of boosted guys do.

Keep in mind that you can also get a lean spike running NA as well.
It's normally harmless, unless as in the case above you're at boost and everything is hot.

 

Does anyone know how to transfer a lm1 (logworks) graph. I can't figure out how to get a pic off of it. I want to show a 4 shift lean spike that pegs 22 on each shift. also, have some spikes that look like like lean spikes but are in fact interference spikes (sutle differences).
Robert

 

You have an actual graph on your computer, or just a logged list that needs to be graphed? If your trying to post a graph just hit Ctrl Printscreen to put it on to your clipboard, then paste it into a photo program and crop it. That's the best way I came up with.

 

Yes, actual graph on comp. I try your method.
Robert

 

Is this a lean spike, or is it there too long to be a spike?

 

I prefer a time difference. In mph mode can look more drastic than it is.. But from what I see if you hit your nitrous at 66mph then you are lean at that point and went way way rich. Do you have this same graph in time mode.
Ricky

 

Nah, the retards at the dyno didn't even give it to me in rpm mode, somethin about the thing losing signal and it only showed up in mph, have no clue. But I lost 2nd gear in the trans on the dyno, so i'm scared to put it back on one (it was on this run, shook the tires and after that, 2nd gear was gone), so i'll be pickin up a wideband to put in the car soon.

 

http://www.fjoracing.com/products/WBAFR/
Go with the FJO widebands. For the money spent I think they are the best.

Ricky

 

How much is it and which one do you recommend, cuz they have a bunch of different one's?