So i replaced my knock sensor and my car does run better. Before the car wouldnt accelerate under boost. Now at tip in, it starts to pull then falls on its face. Does this sound like the trailing coils to you?

 

I would try to reset the ECU. Disconnect the battery etc. One must have had a reason for replacing the knock sensor code/?? so the ECU may be defaulting. If I engineered the system and had a skewed knock sensor I would sure want to limit the power by default until the problem was resolved.

 

I reset the ecu, but no difference...

 

the trailing plugs fire just as often as the leading coils but with less spark...holes in the housings are smaller

I don't think this is your problem
have you changed the plugs lately?

 

I also just changed the plugs tonight...

 

mods?

 

must be on stock ecu if the knock sensor was retarding timing

umm did you check all grounds and are the plug wires connected firmly to the coils and did they click onto the plugs? Also make sure the map sensor hose is attatched at both ends.

 

no, i am running the m2 stage 3 ecu....All plug wires are in place and grounds are secure...

 

maybe check your hoses.

 

What's your current boost pattern and at what boost & rpm does it fall on it's face?

 

We just put a Sears boost controller on it this weekend. So i can control it while troubleshooting. But without the controller its like 12-11-14or 15. Spike expected of course but not worried cuz i know i can fix that by using pellets or porting th WG. It probably falls off at like 4000rpms or so... Havent concentrated on that yet..

 

I once drove my car without power to the leading coils (long story), so it was running on the trailing coils only. It ran ok, but when I tried to accelerate, it stumbled and ran super rough.

Are you sure your plug wires are each hooked up to the proper coil?

Sonny

 

yeah, the pugs are all hooked up ok...

 

If you are spiking to 14-15, you may be hitting fuel cut on the M2 ECU.

 

fuel cut would only be under hard boosted conditions, right?

 

It does it even at easy tip in situations.

 

Not really. Fuel cut on the stock ECU's (or rechipped ones) is usually RPM, Boost Level, and time duration dependent. So, if you are at 4000 rpms at 15 PSI for more than 2 seconds then trigger fuel cut. I'm just making those number up as an example, but that's the general idea.

I have no idea what fuel cut would be on the M2 chips.

I would fix the spiking/creeping first, then see if the problem still exists.

 

BTW, here's what the values look like for the stock ECU:

http://www.scuderiaciriani.com/rx7/fuel_cut_info.html

I would imagine that the M2 ECU is higher, but not sure what the exact numbers would be. I don't think M2's are unlimited.

 

I have felt fuel cut in an FD before and its not at all like this...

 

Ok, what you need to do is record exactly at what RPM and Boost Level the car "falls on it's face".

 

if it is a gradual fall on its face...like it just doesnt pull and pull...then that is a symptom which i had running only leading plugs...the trailing not firing causes your motor to run rich plus just running leading causes a loss of about ten to fifteen percent hp (as my dyno sheets showed when we tested it).


so yes your symptoms could be part of the problem....can you test the spark? are you getting spark on the trailing?


J

 

That isn't quite true -- the leading coil and plugs (1 coil, 2 plugs that fire together) fire twice as often as either trailing coil+plug does in a "wasted spark" configuration.

L, T1
L, T2
L, T1
L, T2
...

-Max

 

Before I just had my motor built I didnt seem to have a problem running rich. But now I have eliminated the air pump, added a cosmo fuel pump, and I had the stock injectors flowed and matched, also now pairing up with a downpipe, and the m2 ecu. But i had the DP and ecu on the car prior to the death of the last motor...

 

You also might hook up a temporary fuel pressure gauge and see if your FPR is either failing or being overrun by the fuel pump.

 

does the throttle angle have any effect on the stumble? can you rev past the stumble in neutral ? the tps, secondaries, or the ignition. my guess in the dark is fuel