Mark,


Can you explain the theoretical benefits of this hybrid set up a bit more? I'd like to better understand what you are trying to accomplish with it.

Very good question Brooke, hope I can give you a good answer.
First of all the hybrid pump in the picture is not finished yet so I have no flow tests to provide. I hope to have this done by May in-between all my other work.

My theory and challenge is to have an RSR style pump using the early Mercedes regulator as most of the RSR pumps used, mated to the later (2.4) pump section with the improved plunger design and enlarged internal fuel head flows and be able to have a pump with RSR style and performance. Some of the benefits from the Mercedes regulator are:

1. Being able to use the early dual solenoid enrichment linkage inside the regulator for a manual cold start device/lever coming off the left side like the RSR’s have.
2. The baro cell on top is located on the right side and provides far better clearance for air filters like the K&N’s.
3. Also the baro cells plunger is seated directly on the balance beam lever with the Mercedes regulator instead of going through a pivot cam and 30mm long rod to get on the balance beam. If not using the baro cell and instead using this for mixture adjustments provides a better contact and control.
4. Ability to use the narrow space cams from Porsche and some of the Mercedes space cams as well. (that’s another story)
5. The Mercedes regulator is aluminum and will not have the magnesium corrosion factor, and when mated to a Porsche aluminum pump section looks great.

Much of these are minor benefits to some and an awful amount of time and labor to get it right. But I’m building a short stroke 3.1 MFI engine, 66 x 100 with a target 8500 rpm, and this pump I’m working on will be tested on this engine. There will be a lot of modifications made to this pump including flyweights, plunger springs, governor springs and space cam.

I will start a thread on the engine soon with another on the pump.

Thanks for the explanation. It sounds like a very cool project. I'm very interested to read about your 3.1 short stroke when you start documenting that. I have a 2.8SS in my 911 and LOVE it. I like the idea of taking a 3.6 and destroking it. Is that what you are doing? If so, are you using one of Henry's cranks or making your own?

The 3.1 I'm building starts with an early 3.0 Turbo case and the early CW 2.0 66 mm stroke crank. Case spigots are inlarged to 105 mm so the 100 mm bore cylinders will fit. The crank has been sent out for oiling mods, knife edge CW's and 2" rod journals with special rods that will use the 2" Clevite NASCAR bearings.

Not to forget the fire danger of carburetors.
Also no fuel smell out of the engine compartment.
I love MFI and can tune them in the car.

Harold