To MFI or not to MFI
 

I'm planning my rebuild of my 2.7 L CIS 74.

I'm not sure weather I should go for MFI or Webbers.

Why not go TBitz EFI? The MFI retrofit will cost you A LOT more money than carbs or EFI and the EFI can be bolted onto your existing CIS for the same price as a used set of carbs. Do a search; there's a lot of info out there.

will this give me the performance of webers, i'm going s cams and JE pistons

Frankly, it should be better, since it has a wideband O2 sensor which adjusts F/A ratio on the fly. Throttle response is supposely similar to MFI as well. I frankly dislike carbs, so take the biases for what they are. All of the cars I own with carbs are all in process of conversion to fuel injection.

..........The MFI retrofit will cost you A LOT more money than carbs or EFI and the EFI can be bolted onto your existing CIS for the same price as a used set of carbs.............

Old 2.7 40mm Webers 200 hp? $1200 to $2000 old school
New PMO 200 hp? $2600 to $3000 new version old school
Rebuilt MFI 200 hp? $2500-$3000 tractor parts but so cool
EFI? 200hp? Most cost $3500 + modern just like a Toyota

How is an MFI more expensive? A'm I missing something?

Henry,

Do you do gearboxes and engines for Aussies?

I have a 915 4 speed I want to update to a 5 speed I just want to exchange for rebuilt one but no one here really does this.

Not to mention what I want to do with the motor, I want an RS spec 2.7

Tony's kit that is specifically for converting CIS cars to EFI is MegaSquirt based and costs $1700, soup to nuts. Motec EFI, etc. are another ball of wax and MFI is actually cheaper there.

Do you do gearboxes and engines for Aussies?

I have a 915 4 speed I want to update to a 5 speed I just want to exchange for rebuilt one but no one here really does this.

Not to mention what I want to do with the motor, I want an RS spec 2.7

We send engines all around the world.

Early gear boxes are our specialty.

Instead of an RS spec engine I would recommend something with a little more pop. Perhaps a little more compression and a more modern cam from DR cams.
We do an intake port/manifold conversion that offers great flow and still delivers low end performance.

Email or call and I'll make something work for both of us.

Matt

I'm in Sydney and have a spare MFI setup I would consider selling if you decide to go with MFI.

I have a 2.7RS++ spec motor (MFI, 10.5:1 pistons, GE80 cams, twin plug etc) in my RS replica track/rally car and it is simply fantastic.

Also, performance 9 or perhaps one of the bigger porsche wreckers or parts places might do a gearbox exchange. However, i wouldn't expect much for your 4 speed.

Ryan,

I have spoken to Dave at P9, although they are great blokes I get my parts from them he can't help me with a rebuilt box.

who else is there?

BTW I'm interested in your MFI, what do you want for it?

Matt,

Re. MFI - I PM'd you a price.

Re. gearbox - maybe call exoticars at silverwater, swan in WA or aporschapart in VIC. there's also some guy in rural WA that advertises in unique cars who has engines and gearboxes.

Shared plenum and agressive cams like S cams don't work well together. The CIS setup has a shared plenum and even with EFI it will be hard to get it to run smooth.

Cheapest bang for the buck is still a used set of carbs in this scenerio but if you can swing it money wise the MFI requires less maintenance and performs better once it's set up right.

I love the novelty of MFI and it's relationship to Porsche in it's heyday when 917s were trouncing the competition. Those were the days....

On a stock 2.7 If I put on MFI what type of cam shafts can I use to gain performance with out having to change pistons?

Stock CIS pistons offer a number of challenges. Valve to piston clearance being the major on.

In the past we have placed valve pockets in CIS pistons and the results were acceptable. (be it lower compression and only done to accommodate a customers budget).
If your project is (as most projects are) governed by budget concerns, I would look to our host for some very reasonably priced JEs and build and engine that will run on CIS, MFI, carbs or EFI and add the new induction later.

What engine configuration will run with all these intakes?
I'm not sure, what is certain is that it will be a compromise, but what engine isn't?
The key will be the cams. I would ask our resident expert John Dougherty what he would use. http://forums.pelicanparts.com/drcamshafts.com
Perhaps a version of a S Cup cam?

By all means contact John. I wanted to install a different cam on my 3.0. I want to keep the stack pistons and run the webers and SSIs that are currently on the motor. He advised a special intake and exhaust grind with the correct lobe center to maximize my existing compression ratio and induction while maintaining clearance. He also helped it fit my budget by suggesting specs that could be reground, not welded. The cams are nearly ready to be sent off for grind work.

What great service! We are very fortunate to have these experts helping out us enthusiasts. Thanks John and Henry and everyone else that contributes.

I'll go with Henry's excellent advice and do the pistons first

Matt,

When do you plan on doing your conversion and what will you primarily use the car for?

Mark,

914/6 2.7

Early next year street use

Hmmm...

I run a set of JE 9.5:1 in my current engine. Finished in mid 2003, it's done four tarmac rallys and a couple of seasons of club sprints.

After Rally Tasmania in Feb I'll be building a new (smaller) engine and will probably sell most everything except the heads and ancilliarys of my current engine.

The timeframe may or may not suit. Just a thought.

Mark

I have sent you PM

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


I'll pretend I didn't read that.

:mad:

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

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

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.

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.

whats the Diff between weber 40IDs3 and 40IDA
 

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

40ID3SChttp://forums.pelicanparts.com/uploa...1132000095.jpg

and

40IDA
http://forums.pelicanparts.com/uploa...1132000155.jpg

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

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.

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

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

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.

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

Thanks again
Josh

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?

2.4 MFI on a 2.7 CIS
 

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

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

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

-Wayne

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?

http://forums.pelicanparts.com/uploads6/11132240758.jpg http://forums.pelicanparts.com/uploads6/21132240768.jpg http://forums.pelicanparts.com/uploa...1132240798.jpg

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.

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

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.