924 Garage " ... the best handling Porsche in stock form.", Jim Pasha, Excellence
Project Ewing

Up Ewing's 931 Frank's Carrera Convertible 924 LJ's 931

David Ewing is moving along on major improvements to his 80 931 (93A0152285). He shares with us the design process and rational used as the pieces come together. David is a member of the Central PA Region and is located in Hatfield, PA.

Goodbye cold start injector, fuel pressure regulator and auxiliary air valve. No longer will I be plagued with well intentioned CIS remedies dreamt up in Weisbauden. The engine should produce 250 h.p. I also will upgrade the oil cooler using one from an early Mazda RX7, these are very nice. 

Ewingheadmod1.TIF (116750 bytes) I ported the head and intake manifold, acquired a Weber big throat throttle body, will install Raceware studs, GTR head gasket and gapless Perfect Circle moly ring set, using 7.5:1 stock pistons and bottom end. The final step is to install an Electromotive TEC2, DIS system with high flow Bosch EFI injectors. The cylinder head is being adapted for these injectors.

Fuel Injection
Original CIS designEwingheadmod2.TIF (48343 bytes) The injector is rated at 38 lbs/hr, Bosch P/N 0280450024.

1. The injector body is only 0.002" larger in diameter than the existing
injector port.

Djettronicsketch.jpg (66122 bytes) 2. If one were to resize the injector body the tip of the nozzle would not quite protrude into the intake port. I was informed that is perfectly acceptable since the pressure differential created by the intake stroke pulls the spray where it needs to go. Machining the pocket ever so slightly will drop the injector further into the pocket and the injector tip will then extend into the port proper.

3. Factoid - MSD sells injector port cutters designed for the Bosch style body. The cutters cost $200.00 and there is a 6 week lead time.

4. The injectors will seal with an "O" ring at the tip. I am attaching two crude documents I have scanned which give some indication of what I am referring to. There is no problem with connector clearance. 


The SDS system requires removing the crank pulley/damper assembly and precisely drilling and mounting two magnets 180 degrees apart. the Electromotive crank trigger uses a disk (variable reluctance?) with evenly spaced cutouts around the circumference. One of the cutouts is larger than the rest, this is used as the timing reference. The disk will be mounted either in front of, or behind the crank pulley assy. The pulley is a job to remove. The disk is mounted such that the disk passes in close proximity to the sensor which in turn generates the pulse.

T Electromotive TECII is around $1,300 without the software. Maybe two people can share the software and split the cost. That would be a plus. The uP might be configured to read the serial number of the software, in which case you would not be able to share.

I sincerely believe spending even $500.00 more today will pay long term benefits in reliability and care free driving. Also, if things really were out of control I could drive to Virginia and get personal assistance. I suspect setting up the timing retard for 1 bar boost condition and fuel enrichment for start take a level of sophistication a home brew system might not capture. Although, I have been wrong in the past.

A hybrid turbo is being built at Majestic Turbo (based on a Garrett T3). I will install a 951 intercooler with 2.5" aluminum plumbing and 1 bar wastegate spring. The turbo arrived and it is trick. It uses a Turbonetics T3/T4 compressor section and the KKK26 turbine. This should be an easy modification. The Turbonetics does not possess the bypass valve and will require the addition of a blow-off valve to the intercooler intake plumbing. I was told HKS has a new model, racing blow-off valve which is also touted as the piece to use. Majestic Turbo in Florida was able to use part of the shell from the KKK26 and install parts form a Garrett T-3.  The exhaust flange will mate as well as the oil line since these remain unchanged.  The compressor housing is different and I will need to revise the output plumbing.  All the turbocharger vendors were reluctant to do anything with the KKK26 because there is very little demand and the turbo itself is very small, there simply is not enough room to machine the housing to swap in different turbine assemblies.  The final cost is $800.00, that is at least $400.00 less than the Auto Atlanta upgrade and I would be willing to bet a much better turbocharger.

Integral cams is finishing the cam based on flow data measurements from my cylinder head and intake manifold.  . (Steve Gruenwald at Integral previously worked at Elgin.) thanks for a great suggestion. This company also started at square one with the 924 because there is so little demand.