im not sure where to start with this. but after i did the controversial mods on my inlet system and port work, the car seems to now have a sort of surging or jerk right around 7500rpm. it wont do it in 1st gear, but maybe its cuz it blows thru 1st so quick. its noticable in 2nd gear. it would probably do it in 3rd gear too, but i dont want to do 80mph on a surface street.

has anyone else experienced this before on their car?

its almost like the car is running out of fuel up top. but i dont think thats possible w/ the little mods that ive done. even with a stock pump and injectors, i cant see that the motor is needing that much fuel, even for Old components.

what do you guys think?

 

It's probably ignition break up.

I had this problem before, installed a Crane Hi-6 and it was gone.
Check it out.

 

hmm, id have to check into that. i did just change the plugs too.

i didnt think that the rotaries needed ignition upgrades untill much later down the upgrade path. dave from FC3S.org did a writeup on installing the HKS twin-power ignition. he didnt see any real gains from it aside from easier starting and crisper throttle response.

ive never really heard of ignition breakup or spark blow out on an NA motor... only forced induction. kind of odd... ive always been under the impression that rotary coils were pretty potent as well.

is ignition about the only thing it could be, or is there anything else i should troubleshoot before throwing an ignition on it?

thanks
chris

 

How about the rev limiter???


-Ted

 

no.

it redlines at 8000rpm and ive hit the rev limit at ~9000rpm before. so i dont think its hitting rev limit at only 7500

 

My car does that too, I'd be very glad to know why. It's probably because it runs so pig rich. I spit flames evey time I shift at full throttle above 7000RPM's. I've got a MSD 6A, new plugs and relatively new wires, so it's probably not ignition breakup. I suspect the excess fuel in the combustion chamber is just not wanting to burn very quickly, giving the surging power. It'll be a long time before I can afford any sort of fuel controller, besides, suspension mods are higher on my list of priorities. If anyone has a bright idea, please let us know.

 

The redline can sometimes be extremely inconsistent.
I've heard of FC turbo hitting redline at 6,500RPM in the higher gears.

Why don't you pull your plugs and find out?


-Ted

 

I replaced my plugs before I installed the MSD and they looked fine, they probably didn't need replacing anyways, but they'd been there for a few years and many thousand kilometers, so I changed them anyways. The surging power isn't violent or even that pronounced, it's gentle and smooth, but it's easily detectable and you can feel the loss of power, that's what leads me to beleive it's associated with my ridiculously rich high RPM mix (I've been told that the flames are up to about 4-5 feet in lenght out of each pipe).

 

yeah... well when i changed my plugs the other day, the old ones had a decent burn on them. some carbon buildup, but not too severe. it definitly didnt show any white specs or wasnt realy even a nice golden brown like i typically see on turbo piston engines w/ a good burn.

after the intake work i did on the car, it smells leaner than before. it doesnt burn my eyes or my nose anymore. it used to be sickeningly rich, but now its way more tolerable. i think the intake work may have leaned out the AFR's somehow.

i do have an SAFC that i could tune it with if i need to. somehow, i dont think im reaching the fueling limits of my stock fuel system... but i suppose anything is possible, with 153k on the clock and counting.