jagged rpm graph

[isnms]

does anyone with any datalogging software experience this?
what could be the causes? noise, timing, detonation, slipping clutch,...

rpm is the blue line

 

[Supracentral]

In general when I've seen oscillation like that it's been due to a battle between the ECU wanting to advance timing and the triggering of the knock sensors telling it to retard timing.

It can be caused by one of the following:

1. Too lean of a mixture
2. Too hot of an air charge (insufficient intercooler)
3. Faulty knock sensor
4. Faulty knock sensor wiring
5. Cylinder hot spots (ie - damage to pistons, valves, plugs)
6. Too hot of a spark plug
7. Poor oil control internally causing detonation
8. Poor fuel quality
9. Damaged or worn CPS gear
10. Bad sparkplugs
11. Bad sparkplug wires
12. Weak or failing coil packs
13. Faulty ignition wiring
14. A few other reasons I can't remember right now..

That jagged line is the cars way of telling you to back off a litttle - you are pushing the ragged edge for one reason or another.

 

[isnms]

thanks for all that info, that's a lot to contemplate.

 

[tubbie]

It can be caused by one of the following:

1. Too lean of a mixture
2. Too hot of an air charge (insufficient intercooler)
3. Faulty knock sensor
4. Faulty knock sensor wiring
5. Cylinder hot spots (ie - damage to pistons, valves, plugs)
6. Too hot of a spark plug
7. Poor oil control internally causing detonation
8. Poor fuel quality
9. Damaged or worn CPS gear
10. Bad sparkplugs
11. Bad sparkplug wires
12. Weak or failing coil packs
13. Faulty ignition wiring
14. A few other reasons I can't remember right now..

.

That narrows it down... :rofl:

 

[siman]

/\ :rofl:

 

[Supracentral]

Hey, I know that's a long list and it's not even complete.

But when you've got a problem like this it's good to know where you stand. Develop a list and start eliminating possibilities.

Here's how I would work it out.

ALWAYS start from the cheapest/easiest solutions, work your way up. It's amazing how many times I've seen people spend virtual fortunes fixing a problem that was resolved with a $29 part.

With that said:

1. Poor fuel quality < - using good fuel? If so this is eliminated. Try some race gas - problem goes away? Almost 100% guarantee it's a knock issue.
2. Too lean of a mixture < - eliminate with a wideband test
3. Too hot of an air charge (insufficient intercooler/undersized turbo/overboosting turbo) <-which IC do you have? Good one? Which turbo? How much boost? we should easily be able to eliminate this too.
4. Too hot of a spark plug <- which plugs are you running - what gap? Should be able to eliminate this one quickly
5. Bad sparkplugs <- Cheap fix, unless they are new, replace them.
6. Bad sparkplug wires <- Cheap fix, unless they are new, replace them.
7. Faulty ignition wiring <- test, replace if necessary
8. Faulty knock sensor wiring <- test, replace if necessary
9. Faulty knock sensor <- test, replace if necessary
10. Weak or failing coil packs <- test, replace if necessary
11. Damaged or worn CPS gear < - inspect, repair/replace if needed
12. Poor oil control internally causing detonation <- save for last - potenially expensive fix
13. Cylinder hot spots (ie - damage to pistons, valves, plugs) <- save for last - expensive

We should be able to narrow this list down pretty quickly. Some simple tests (like a compression test/wideband test) can eliminate some of the items too.

 

[isnms]

some points answered:

1. Poor fuel quality < - using good fuel? If so this is eliminated. Try some race gas - problem goes away? Almost 100% guarantee it's a knock issue.
   
   come to think of it, for the past few months we've only been able to get 91octain around here. before that i was getting 93.​
2. Too lean of a mixture < - eliminate with a wideband test
   
   that's a snapshot of my wideband log. the green line is the a/f. the part where it dips down is around 12 then it goes down to about 11.2. i've just started tuning the s-afr but i don't think that's to lean.​
3. Too hot of an air charge (insufficient intercooler/undersized turbo/overboosting turbo) <-which IC do you have? Good one? Which turbo? How much boost? we should easily be able to eliminate this too.
   
   i have the cartech series 2 ic, 2.5"hard pipes, 50trim ct-26 and the evc4 @12psi​
4. Too hot of a spark plug <- which plugs are you running - what gap? Should be able to eliminate this one quickly
   
   ngk plugs BCPR6EIX iridium at .030"​
5. Bad sparkplugs <- Cheap fix, unless they are new, replace them.
   
   6mo old​
6. Bad sparkplug wires <- Cheap fix, unless they are new, replace them.
   
   ngk wires about 2 yrs old​
7. Faulty ignition wiring <- test, replace if necessary
8. Faulty knock sensor wiring <- test, replace if necessary
9. Faulty knock sensor <- test, replace if necessary
10. Weak or failing coil packs <- test, replace if necessary
11. Damaged or worn CPS gear < - inspect, repair/replace if needed
    
    
    ​
12. Poor oil control internally causing detonation <- save for last - potenially expensive fix
    
    engine has just been rebuilt and oil pressure is good. i may have to replace the hg again though. i'm getting air in the coolant system and that only startet when i up the boost to 12. compression test may need to be done here.​
13. Cylinder hot spots (ie - damage to pistons, valves, plugs) <- save for last - expensive
    
    engine just rebuilt​

guess that leaves me some things to test

thanks for the tips. any more ?

 

[hottscennessey]

my zeitronix logs get a little jagged near redline, but for the most part they're alright.. not quite as jagged as yours.

 

[TurboStreetCar]

thread revival, was this resolved? if it was what did u do. i just got my ZT2 kit and ive tried 2 diffrent sources for the rpm signal, ive tried the black wire from the ignitor thats suposed to be the tach signal. and ive tried the light green wire thats the IGT wire, both of with i haveto set my zt2 to 2 cylinder to get a correct rpm reading. but ill get spikes of like 7200rpm only under hard acceleration. could it be the signal wire im using? ill post a picture of it up later.

 

[mmarkk]

Zeitronix themself answers here: http://www.supraforums.com/forum/showthread.php?t=366502

 

[isnms]

You must use IGT or IGF for RPM signal. You must also set the software to 6 cylinder.
Check the Zeitronix ZT-2 Wideband wiring installation in my sig for wiring help.


about the jaggedness; Here is the link to his post: http://www.supraforums.com/forum/showthread.php?p=4291993#post4291993

and in case you don't have a sf account:

Zeitronix Zt-2 Wideband is equipped with a complex proprietary circuitry to condition the RPM signal. This is the only wideband on the market which is able to read RPM signal from multiple sources, the tach signal, the ignition coil or the ECU igniter drive without inductive clamps, RPM adapters, additional gizmos. Zeitronix Zt-2 Wideband adds a very small amount of averaging (filtering) of the RPM data to smooth out the RPM graph a little. The Zt-2 very high output sample rate contributes to the RPM signal variations you are seeing. Other units with only a handful of output samples per second are not going to show RPM variations per single crank revolution just a general trend. Wouldn't you rather see more data or less when tuning your expensive engine?
We may add some more averaging to make graphs very nice and smooth looking for MtFujiSupra, however most tuners are looking for a real data. We will consider user selectable averaging routine for a next software release.
As always, make sure your instrumentation is grounded to a clean ground point to gather the best data possible.

Tune safely!
Zeitronix Eng.

 

[TurboStreetCar]

i see thanks, but my problem is slightly diffrent then the ones mentioned but it was answered in someones post over on supraforums, my problem is i have spikes that go up to like maybe 72000 yes 72 thousand rpm, in one of the posts it said that noise would be a spike witch is what i have. they also said that a chassis bolt isnt a good enough ground for it and thats what im using so im gona change my ground and see how it goes. also i did a test today and i picked up 15 bucks of 100octane and it still does it so i kno its some sort of noise.


i have it hooked up to the light green wire from the ignitor (IGT) and i still have to have the cylinder selection set at 2 cylinder for it to read correctly.

Thanks for the replies.

 

[hottscennessey]

mine used to do that.. i dont know exactly what did it.. but it dropped me a BIG hint when my alternator went out.. i replaced it and problems went away.

just to clarify, mine were short spikes i could actually hear from my engine.. my A/fs and Vf's also responded to the spike. It was almost like a little "burp" that would randomly come and go.

 

[TurboStreetCar]

hmm, well mine i cant hear and nothing else shows a reflection of it. ill post up a log showing what ecactaly im talking about, id post it now but my laptop is in my car.