Plenum injection Ka-boom!!

[T4 Primera]

For those of you considering a NO2 system or turbocharging with additional fuel injection in the plenum, I just thought I'd relate something I saw the other day.

My brake man was given (as in for free) an old Celica by a customer to play with. It was MPI at the ports with dry intake runners. So they fitted a turbo off a Subaru to it and some extra injectors to the plenum.

After fooling around in it a bit (he didn't want to until he got it properly sorted - but was nagged into it) the engine blew. Removing the head showed 3 out of 4 pistons with broken top ring lands.

Now there was plenty of fuel getting supplied as shown by the puddles in the plenum but the cleanliness of the piston tops and combustion chambers suggested it was definitely not burning rich. Also, the one piston that was undamaged was a little 'darker' with residual deposits than the others. Possibly, poor fuel distribution caused leanout in the other 3 cylinders.

Just thought I'd share this to illustrate what may happen when fuel is injected into parts of the intake system that are designed to run dry. Every manifold I've seen designed for handling a fuel/air mixture has also included water jacket heating to avoid this 'puddling.

[nis.k.a.]

The whole idea of injecting fuel into my airstream makes me nervous. This just adds to it. Poor Celica....OH WELL.