Mileage VS Performance
 

I have a 2.4 E cam 9.5 cr engine with carbs and 2.7 heads. I'm looking to greatly increase gas mileage without a big drop in performance.

I remember when I dual plugged my BMW R100RS the gas mileage went up substantially with a modest gain in performance. Is this also true on a Porsche engine?

I have a complete CIS fuel injection unit taken off a 1976 2.7S. Will this work well on the 2.4E? Will I lose a lot of performance VS the gas mileage gain?

I have another P car that has a 2.7RS spec engine for go. I would like to build a strong, good gas mileage engine for touring.

What do you think is the way to go to increase fuel mileage with this engine?

Thanks!

911T cams and EFI.

You could use your CIS intake on your 2.4 and use a bitzracing EFI conversion, this would however require some port work as the port sizes wouldnt match intake-head. The better option would be to find a CIS intake from a 73 1/2 2.4 this would fit straight up and would be perfect for an EFI conversion. EFI will easily out perform any early induction system in terms of gas milage if you have the will/ability to get the tuning spot on.

http://www.bitzracing.com/

Steve

I’ll contribute to the effort.

I agree with John; 911T cams, EFI, leave the CR at 9.5:1, twin plug (integrated with the EFI), use the ’73.5 CIS intake for the EFI, 911SC iron clutch and heavy flywheel, turn the engine slowly, turn the fan fast to keep engine cool (a front cooler would be good), etc.

The EFI will let you use mixture and knock-sensing feedback to eek out the last bit of efficiency and/or performance (you do have to go up hills and safely merge into freeway traffic) without damaging the machinery.

The ’73.5 CIS engine produces 75 hp at 3000 rpm. This engine would have more radical cams (non-CIS 911T), higher CR, twin plug and better fuel/spark management. I would expect over 100 hp at 3000 rpm, more than sufficient for an early 911.

I have a ’73.5 CIS intake system I’ll donate.

It might be useful to figure a way to introduce more ‘swirl’ in the intake runner/port. It might turn out that the ’74 911 ‘normal’ CIS cams would be best.

Best,
Grady

I'm a bit confused, why do I need the 73.5 (2.4) CIS intake when I already have 2.7 heads on this engine.

The Bitz racing EFI conversion sounds very interesting, and is cheap enouph.

If the dual plugging makes as big a difference as it did on my BMW bike, that will also be in the mix.

Man, I would hate to give up those E cams.

Thanks,
Ken

Didnt see you had 2.7 heads in that case your 2.7 intake would fit right up to these, you may lose some bottom end though with the 2.7 heads as the 2.7 ports area bit large for the 2.4 this may have a negative impact on gas milage.

Steve