What to do, keep Cis or go with Pmo’s

[OSC911]

Originally Posted by Showdown

This is one of those arguments that I just don't understand: with EFI you have comprehensive engine control so you can set whatever tune you want. You can even have different tunes for different situations: one for modest and fuel efficient driving to the track and one for the track that chugs gas. That flexibility just isn't available with CIS (Unless your Ian and have a trick on-the-fly adjustable WUR) or carbs and for that reason, objectively, they are inferior systems.

I'm not crapping on CIS or carbs but there's just no way to have the level of control available with EFI.

I just fitted a Motec, PMO ITB kit to my 3.0 litre. It had a base tune that assisted in getting it running but was pretty poor. Backfiring through the throttle bodies, barely idling etc. I had it tuned yesterday by a well regarded local tuner who hasn’t had any experience with air cooled cars, let alone Porsches. He usually tunes big horsepower 2JZ Toyotas and Jap engines.

He was happy for me to hang around and assist with the usual checks which was great. Two hours later, he was done. Perfect tune at all RPM stages. Super smooth idle and making power right through to 6100 RPM. Falls away badly after that as it has CIS cams and pistons but still made 207HP at the wheels on a rolling dyno - he didn’t have the correct adapters for the 911 wheel PCD to use the hub dyno.
EFI is just so adaptable, with the right guy/tuner it can be just as smooth as CIS and produce way more power. My advice is go with EFI and find a good tuner that knows his stuff. There are plenty around, if they can tune a 2JZ with 1100 reliable HP they can tune an air cooled Porsche.

[mikedsilva]

Originally Posted by OSC911

I just fitted a Motec, PMO ITB kit to my 3.0 litre. It had a base tune that assisted in getting it running but was pretty poor. Backfiring through the throttle bodies, barely idling etc. I had it tuned yesterday by a well regarded local tuner who hasn’t had any experience with air cooled cars, let alone Porsches. He usually tunes big horsepower 2JZ Toyotas and Jap engines.

He was happy for me to hang around and assist with the usual checks which was great. Two hours later, he was done. Perfect tune at all RPM stages. Super smooth idle and making power right through to 6100 RPM. Falls away badly after that as it has CIS cams and pistons but still made 207HP at the wheels on a rolling dyno - he didn’t have the correct adapters for the 911 wheel PCD to use the hub dyno.
EFI is just so adaptable, with the right guy/tuner it can be just as smooth as CIS and produce way more power. My advice is go with EFI and find a good tuner that knows his stuff. There are plenty around, if they can tune a 2JZ with 1100 reliable HP they can tune an air cooled Porsche.

Sounds like a fun motor.
Do you recall what AFR or Lambda he was targeting when doing your full throttle runs?

[juanbenae]

removed CIS from 2 3.oL motors i built. had 46mm pmo's on the red, 78SC spec911 car with euro compression pistons and a recurved dizzy with SSI's I cut the heater boxes off of...

the white one was a hotrod 75 I built much like the race motor but with a very nice set of 40mm webers.







i liked carbs on my flat six.... you gotta dick with them from time to time with today's pump gas offerings with all the additives, but if you are committed to learning them it's pretty rewarding.

or do an EFI set up that must be thousands now days. I do jeeps now.

[juanbenae]

oh ya, if you are gunna do it have somebody in the know recurve the dizzy or it won't run right through all the ranges.

[OSC911]

Originally Posted by mikedsilva

Sounds like a fun motor.
Do you recall what AFR or Lambda he was targeting when doing your full throttle runs?

Hi Mike
I let him do his thing in the car but I was watching the monitor and the remote AFR gauge and from memory it seemed to be between 13.0 to 13.9. When it cam back after each run it dropped to 11.0 for a minute for some reason and then stabilised to around 14 or so. We couldn’t really work out why though.
It pulls super hard with great low end torque but runs out of steam pretty early.
Now I’m keen for pistons and cams but that’s a way off.

[Gordo2]

I'm the dude reading your original post, skipping past pages of replies that were incredibly insightful and relevant - to add my thoughts, as a guy who went to carbs and did it because I needed to.

CIS is hard to beat - my OEM system went 190k miles, with a distributor rebuild being the only needed fix for fuel / ignition related repair. Don't give another thought without realist thinking of what a replacement / alternative offers...

Love my PMO's, but went in with the commitment to embrace and re-kindle the old school tech. I've bridged old & new on my journey, and determined that - its hard to fail with advice of this Pelican community's guidance & input.

Take it all in and do what appeals to you - you have a huge Pelican community itching to help.

-- Gordo

[OSC911]

My recent EFI install

Old school look with some modern tech.

[Undecided]

I have a new set of PMO 40s on my '77 2.7L. Can someone explain the hand brake throttle knob? What is needed? How is it installed? Pics?

What are some good resources to learn how to adjust/care for PMOs?

Thanks!

[pmax]

Originally Posted by OSC911

My recent EFI install

Old school look with some modern tech.

That's perfection.

The benefits of modern engine management without all the drawbacks of open loop engine killing caveman carbs.

[MST0118]

If you’re not concerned about gas mileage or having stock look, I would go for PMO (assuming you’re not interested in fuel injection). Much better throttle response and sound. If I were doing it, I would get custom CPs with good valve clearance and go for a cam with more duration like GE40 or even GE60 depending on what you want to do. For that cam I like the 46s.

I’d keep the CIS if you ever want to bring back to stock.