Some of you may know that I've been having mystery knocks now and then. Here is a graph of a good ping i just had today.



All the stats on the left are durring the ping. Could this be simply an octane problem? Or could it be that my leading plug didnt fire at that point and the trailing did?

 

Am I reading you log correctly?
(1) rpm = 4943
(2) boost = .88, is that psi or .88 X 14.5 = 12.76 psi???????
(3) IGL = 8
(4) AFR = 10.771

 

.88 bar yes you are correct on being just under 13psi

 

That rich at that boost and only 8 IGL, I doubt it is the 91 octane fuel, unless you got some super large intake ports.


I am at 12 IGL and 11.5AFR at that boost with my GT35R stock intake and mild exhaust port on 92 octane. I run 11.2AFR at 15psi boost.

Either bad gas or something else.

 

unless i keep getting bad gas all over my city, i doubt thats the problem. Stock port, stock turbos. This knock was really hard hitting too, gave a nice hesitation. Would a trailing plug firing alone cause such a problem?

 

Mis-connected igntion wires or too much carbon in the engine might cause it.

I always noticed that knock levels are always a little higher on the first boost run than later. If those AFRs are your norm, most likely you have carbon builup from running too damm rich!


Have you ecer noticed how better the car runs after a long trip? It burns off the carbon built up from slow driving.

 

the engine only has about 5k miles on it. I'll run some Seafoam through her and also I need to get a seperate A/F gague because I'm relying on my datalogot software for my lc1, i need to make sure my a/f is accurate.

 

i called up a former rotary engine builder that also did tuning. His engines were used for sandrails, he seems to think that i might have a partially fouled plug, I'm going to replace them as soon as my engine cools down and hopefully i will have some results tonight.

 

I changed my plugs and turned my water injection back on. Everything was fine for a few pulls then I decided to do a long 3rd gear pull and *PING,* right before 5k or so, not sure I wasn't logging at the time.

I'm going to put my head through a wall.

 

Double check you coil connectors by connector color (White #1 T front coil; Black #1&2 L middle coil; Blue #2 T back coil) and spark plug wires from coil to plug.
Leading plugs are the bottom position, while trailing plugs are the top position.


Log it again and attach the complete log for the event. Use both basic and advance logging.

 

yeah we went over the coil situation a while back when i was having this problem a while ago. everything is hooked up ok. I just got done ordering the innovate a/f gauge so I can check it against my logging.

 

ok... ive been thinking (uh-oh) im going to disable the trailing spark and see what happens.

 

W00T! OK I'm getting somewhere. I disabled my trailing plugs and *BAM* ignition breakup city above 6k rpms @ WOT and NO detination (so far) Now all I've got to do is wait for my a/f display in the mail to check it against what my computer reads.
I kinda thought my power ocilated a bit up high. I would hate to know how often the trailings were picking up the slack.

If that checks ok then I'm guessing either my stock style spark plugs aren't good for anything over 10psi (could someone verify). If that isnt the problem maybe i need an ign amp?

 

for those that care, i put in some of those ngk race moped plugs. I forgot what the number was. I used a 9 heat range. With my trailings still disabled these plugs seem to have almost clared up all of my missfires. I'm waiting for a twin power to come in the mail, once that comes in I can start tuning again.

 

ive got my twinpower in. I still have my trailing plugs disabled. I've got no detonation, power is beyond belif now, even with a fairly conservative timing map. I'll finish my tuning this weekend and enable the trailing plugs and start adjusting the split.