96 FD RX7 S7, Missfire on Accelleration Problem!!
 

Hi Guys,

I have a 96 Series 7 FD Type R, Just rebuilt the engine and have had stage2 ported, 2mm race seals & dowelled.
Still running standard ecu for now, series 8 Twin Turbos.
I have a problem where on rapid accelleration...at about the point where 2nd turbo has kicked in...my car will do a missfire, and it does it just about every time at the same point. It concerns me alot as i dont want a missfire to do any damage to engine...and almost feels like for a split second it starves of fuel or something.
It has been like that for as long as i can remember now, but shouldnt be doing that tho, and was probably the reason why the original engine decided to instintanously spit both rotor apex seals out the exhaust only a few months back! Anybody experienced anything like this? and know what the cause could be? Any idea's would be great. Cheers, Jeremy :)

What mods do you have and how much boost are you running?

It almost sounds like your boost is spiking and you are hitting fuel cut. Too much boost will definitely blow a motor quickly.

Thanks for the reply gracer7, well still has stock ecu it should still be at stock settings shouldnt it? forgot to mention i also have 3inch exhaust, no cat and trust down pipe and also no air pump. Doesnt really feel like any boost spike...but you might be right the fuel cut is probably coming into it.
I dont have any boost mods other than a sequencial blow of valve fitted to one of intake pipes.
Do you reckon i should fit a boost gauge first to see if anythings happening?

Cheers, Jeremy

The stock ECU cannot adapt to modifications to the car. If you take resistance out of the intake or exhaust the boost level will increase. With all of those exhaust mods it's probably a lot more boost than the original boost level.

Get a boost gauge and figure out how much boost is being produced, then if it's too high (often a spike in boost around 4500rpm) install a boost controller.

Thanks for your advice, my next plans where to run a stand alone computer to cope and be tuned to all the upgrades i have done...but since funds are limited at the moment...it might be a while away. The engine rebuilders said it was safe to run the mod'ed new engine on the factory ecu...but it seems maybe not! :( . I will fit a boost gauge and see if its spiking...and if needed fit a controller. What boost is safe to run on Factory set fuelling? And what boost are the twin turbos limited to? Cheers, Jeremy

The factory FUEL SYSTEM safely supports 10 PSI of boost. Any more and you will eventually detonate and blow the motor from running too lean.

If it will be a while, why not find a used stock cat or high flow cat so that you can safely control boost. A full open exhaust makes it almost impossible to control boost on the stock boost control system.

Check out the threads in the FAQ thread on boost spike and boost creep so you can learn more about it.

HKS Twinpower.
Barry

It sounds like your running open exhaust...If funds are of an issue to you just install the main cat and it should be good. Once your ready to get an ECU run your open exhaust again.


EDIT: Whoops gracer7-rx7 already said that.