2.7 RS MFI on 3.0SC long block

[911st]

Wondering if a stock 2.7RS MFI injection could be tuned to 'work well' with stock SC long block. Meaning with stock but maybe re-timed cams & 1.5" primary tube race exhaust?



Thx

[HawgRyder]

The main problem would be the pistons and how the piston/cam combination reacted to the MFI.
The heads would need to be modified to accept the MFI injectors.
Compression numbers are different.
Timing would need to be addressed.
Seems like a lot considering you are only bumping 300cc.
Bob

[911st]

Thx

I believe the MFI pump output most closely matches the TQ curve. Thus a good fit should be where the TQ by rpm is most closely matched. If so the following TQ curves might give some clues to at least under WOT.

Idle is somewhat adjustable on MFI. As is moving gross delivery up or down by adjusting the MFI rack. Peak delivery can be moved up or down a bit by adjusting the pumps centrifugal weight springs.

The 3.0SC tq curve could probably be moved or improved some at higher rpm with a race exhaust and or playing with cam timing.

In all, over the rpm used at the track, it should work. The challenge being drivability in other areas I guess.


"The 3.0 and 3.2 were run on a dyno, the 3.0 is stock while the 3.2 has SSIs, special muffler, and other tuning like most F class race cars. Note the 3.0 is like a larger 2.7S engine. And it is interesting how the 2.7RS has similar low end torque to the 3.2, and a stronger top end. But the 3.2 kills the 2.7RS through the meat of the powerband."

I borrowed this from here: Analog Mike's 911 engine page

[Steve@Rennsport]

The REAL key is getting the MFI pump done right so it tracks from idle to redline at all throttle settings. Based on extensive dyno experience, many get this wrong and very few can do this well.

One cannot deviate far from factory camshafts unless you make a custom space cam for the pump and that's neither cheap nor easy to do.

[911st]

Thank you Steve. I fully agree.

Was kind of hoping you or someone might have tried this combo.

I once tried to mod my own space cam by marking the space cam with a felt tip to see where the stylus tracked and grinding on it for a 2.8 with improved S cams. Must have R&R's that pump 40 times. That is when I ended up having Gus build me an 2.7RS pump.

I believe they used this space cam & injection on the 74RS 3.0 w stock exhaust but that was with the S cams of course.

Kind of wonder if one could get reasonably close with the SC cams by trying to tune the motor around the MFI pump as much as possible by re-timing the cams and adding a race exhaust so it breaths something between an 2.7RS and 3.0RS. Then re adjust the pump weight springs to better match up the TQ peak point.

Probably just another one of my crazy ideas.

Good thoughts!