RX7 - Random Loss of Boost, Fuel, Spark

Hi All,

Was doing some dragy gps testing and randomly i had a power cut, looking at the logs fuel, boost, spark all cut at 6597rpm. TP still at 100% until 6700 rpm. I've gone over the logs and cant see any gp rpm limit, map limit, rpm limit get activated. Anyone able to offer insight into why this happened?

Sounded like something popped off....but checked all boost lines, turbo, engine etc...and all looks fine. Drove car home and again all in fine. Random G4+ ecu glitch?? which maybe activated a gp rpm limit but didnt log the activation?

I'm not a pro in data analysis (yet!) but I'm trying to develop those skills. So I'll give it a go!

I went over your log but I couldn't find anything out of the ordinary. Your MAP dropped almost all the way to barometric pressure and the ECU reacted by pulling fuel and timing, but it's hard to see if it's because it missed first or MAP went down and then you had a loss of power. Did you feel a missfire or a stumble of the engine or it just stopped accelerating?

The fact your lambda didn't go lean (let's say it would be a false reading from the MAP) shows that there was actually less air coming in your engine. So your boost leak could have been a good guest.

Im not a pro either and also learning everyday. I found it very strange that none of the limits of safety systems got activated. I could hear the loud sound of pressure being released....poooff...like hitting a wall. I obviously shit myself and thought I blew up my engine or turbo but everything was responding as normal. Off Boost the drive was the same etc....but the turbo spooling sounds were reduced / diminished.

I checked everything in the engine and nothing seems to have come loose or gone wrong. Still got the same oil/coolant levels as before. I'll have to put the car on a ramp and see if any wg lines have popped off.

When you said all is fine when you drove the car home, did you try to build boost? I assumed that everything was working as it should.

Try to get a smoke test of your intake piping to check if you have leak. Maybe check if you have a stuck open wastegate. Would be obvious if you have an external one with a dump tube but sometimes if it's an internal gate it's something you could have overlook.

My eyesight isn't what it was, but...

I agree with Frank - looking at the lambda you can rule out an ignition or fuelling problem - if either was cut it would show as a lean condition caused by the excess oxygen in the exhaust gases. You can rule out any ignition or fuel cut for the same reason and as it did continue to accelerate further up the rpm range

It looks like you were doing a pull in a low-ish gear without a problem, changed gear, continued with the pull before it suddenly lost boost pressure? I don't see it being due to a boost cut, either, because it was holding fine for a while.

Most likely reason is you blew off a hose somewhere, split a hose - this may be difficult to spot as it may close up when off boost, split the charge cooler, seized the turbo', etc.

Perfect thank you both. That is very helpful. I agree with the points raised and will look over the boost lines asap.