To MFI or not to MFI

[Tyson Schmidt]

Originally posted by Henry Schmidt
[BRebuilt MFI 200 hp? $2500-$3000 tractor parts but so cool

Tractor parts!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!?????? ??????????????


I'll pretend I didn't read that.

[bumble]

Matt,

I haven't given this any thought yet - I wasn't really intending to deal with it until the new year.

The biggest problem with building a quick road engine is knowing just how far to go and thus how much to spend!

For an all out competition engine it's no problem - you just do and spend whatever it takes to get the strongest, quickest engine you can.

With a more or less standard road engine, there's not much to do other than put it together with good standard parts within spec.

I'm sure you know 2.7s have a number of issues that need to be addressed to get reliability once you extract good power. This costs $$$ to do. If it were me and the goal was a quick road car, I'd be tempted to find a good 3.2 Carrera engine and sell the 2.7. But that's me... If you abosultely MUST go the 2.7 route, email me or give me a call - gratuitous advice is never in short supply


My email is mark@penguinsystems.com.au

mob is 0410 559 395

[matty74]

I would'nt call the 917 a tractor, MFI kicks ass, I just can't afford it right now

[matty74]

You sound like my mates, get a 3.2 carrera, but I love the 2.7, I love MFI, and s cams. The early 70’s was a special time for Porsche, cause I was just a kid when this model came out and my mates mum had a new 911s in 74 and that's when I got the porsche bug at the age of 5.

Owning an early 70’s 2.7 is like living with a difficult woman, but she does it for you.

[Eagledriver]

Henry is refering to the origins of MFI. This system is based on the diesel systems found on tractor engines years ago. It's much more sophisticated due to having to keep the mixture right on a gas engine but it's based on early diesel systems and I believe originated in WWII on the ME109 fighter (not a deisel).

-Andy

PS. The other EFI systems (non-motec) weren't included in Henry's comparison because they won't produce the power that the options he listed will. You have to have the separate throttles and straight intakes that Carbs/MFI/Motec provide.

[matty74]

what the diff between these carbs in terms of cost and performance?

40ID3SC

and

40IDA

[degreeoff1]

Hey I know !!!

Just bought a set of IDS carbs....an extra fuel enrichment do hicki (venturi??) will enhance high RPM performance

Am I right teach???

LMAO 914-4 to 6 er

[304065]

No, the extra enrichment circuit does nothing for increased peformance, it's there for safety only. Once you are at the optimum fuel/air ratio at high rpm, more fuel doesn't help.

[Henry Schmidt]

It was designed to prevent detonation in high compression engines. It did not work!!!!!!

[degreeoff1]

is this to say that the set I just bought are not worth a damn over IDA's??

Shucks
Josh

Not to hijack the thread but I am a newbie to 911 ville

[Henry Schmidt]

No, they are worth a great deal to a concours gismo that cares more about how it looks than how it works.
The enrichment circuit can be sealed so the carbs will function properly.

[degreeoff1]

Will this be a detriment to performance or just gas economy?? These were just rebuilt to include shaft seals?

Thanks again
Josh

[matty74]

Can I take a 2.4 MFI system and bolt it on a 2.7 to replace the CIS?

If so what mods need to be done?

[356RS]

Yes....but you will or should replace:

Cams w/mfi drive gear, T, E, S or more
Pistons with 8.5comp or more
Heads must be mod. for mfi injectors

I know I forgot something...

Mark

[afterburn 549]

SDS can sell a whole sys for about 3 gs.....supposed to be ez to tune and very adaptable...(double plug, turbo or what ever)...no need for a lap top I am told, or many trips to the dyno....personally I would do a sys like that rather then carbs .Carbs were great in their day,that day is gone

[Wayne 962]

Originally posted by Henry Schmidt
How is an MFI more expensive? A'm I missing something? [/B]

I haven't really seen any rebuilt 2.7 MFI systems go for less than $5-6K lately...

-Wayne

[Henry Schmidt]

Wanye, it seems we're bumping heads again.

Although an 019 pump is hard to find and conversion pump works as good or better. (you can calibrate the conv. to specific needs while you're converting).
As for the whole system we (Supertec) have been known to sell custom built systems for under $3000.

That is about the same as PMOs and cheaper than most quality EFI systems that are capable of the same performance.

And what EFI system looks like this?

[mpdevelopment]

As for carbs being dead, ever hear a current Trans-Am motor run or see how much power an unrestrcted Nextel cup V8 makes? (850+ hp at over 9000rpm). A properly tuned carb setup can have better mixture atomization than most fuel injection systems. The carbs suffer at lower rpm due to the fact that the engine must draw the fuel from the carb. Above this critical point the carbs are quite good. The mfi system has a high pressure nozzle that chatters when metering fuel this atomizes the fuel better than any efi nozzle. Even with this Porsche in many of their racing engines placed the nozzles at almost the top of the intake stacks in order to help mix the fuel and air.

[Porschekid962]

All this back and forth and Henry teasing with those pictures oh god. Has ANYONE ever taken a motor, who cares about displacement but after run in swapped from carbs, to mfi and to efi to "see" some real HP difference on a dyno? I think there would be enough resources between all the ppl on this forum to where we could make this happen. Blueprint a 3.0 or something like that, use S cams, decent CR, single or twin plug, then to back to back tests swapping intake systems.

That I would like to see, until then we can all love what we love and for our own strange reasons.

Ryder

[Henry Schmidt]

As I see it, everyone has a favorite way of doing things. If you have a plan, research the options and choose that system that best fits your needs.

All the systems talked about here will work and will work well.
That said, all systems have limitations and compromises. Choose the one that compromises in places you least care about.
For instance if fuel mileage is important to you, CIS & EFI systems tend to offer better fuel mileage

Building these car/engines offers tremendous enjoyment and very hard to justify, so build what will make you smile.