For flat sixes: Webers v MFI v EFI, Ecologically speaking… Options

[horizontally-opposed]

Currently have a 2.2E/S with Webers. It runs well and makes good power, having been tuned on the dyno and further dialed in since then, but I have discovered I'm just not a carburetor person. Fuel economy isn't good enough for the size of engine/car, and the emissions bother me—both in terms of the smells in my garage and while driving the car. And yes, we've been totally spoiled by low emissions cars.

What I'm curious about, for anyone who has lived with carbs and MFI: Is MFI noticeably cleaner and/or more efficient than carbs?

Or is EFI the way to go? I'm in no hurry on this, but curious for the experiences of others. Yes, Motronic, but I actually like the 2.2 engine.

Thanks! (IMG:style_emoticons/default/beerchug.gif)

[sixnotfour]

efi is the old school Boss..not so correct for the ecology..

call Clewett.. EFI


3.2

[mepstein]

A properly restored and tuned MFI setup will be close in cost to a running 3.2 engine. I don’t think it’s what you really want. A properly tuned modern day efi system would do it but again, by the time your done -$$$.

[worn]

Currently have a 2.2E/S with Webers. It runs well and makes good power, having been tuned on the dyno and further dialed in since then, but I have discovered I'm just not a carburetor person. Fuel economy isn't good enough for the size of engine/car, and the emissions bother me—both in terms of the smells in my garage and while driving the car. And yes, we've been totally spoiled by low emissions cars.

What I'm curious about, for anyone who has lived with carbs and MFI: Is MFI noticeably cleaner and/or more efficient than carbs?

Or is EFI the way to go? I'm in no hurry on this, but curious for the experiences of others. Yes, Motronic, but I actually like the 2.2 engine.

Thanks! (IMG:style_emoticons/default/beerchug.gif)

Cross country I got a little better than 25 mpg with the 3.2 and stock efi. Same as my big Ford Escape. One cause of the lower mileage is the increase in speed limit across the different states. At 85 mph you are way past the inflection of the drag curve. But crossing Nebraska, you feel silly not keeping up with the Jeeps.

[burton73]

I can tell you one thing, MFI on an E or S when tuned well will pull super strong in every gear. On my 73 S it ran great when the MFI was synced well but the tune would fall off in not that long and then it just pulled well but not as good as just right out of tune.

CIS ran well and kept its tune for a very long time. Always started right up and ran the same (good) all the time. Monotonic always ran good for me in my Carrera.

CIS and Monotonic always worked great.

I have PMOs in 46 for my 6 and we have to work out the tuning after we get the break in of the Engen. I think the PMO 46 where like $6,000. If you are not going to run your car all the time, carbs IMHO need to be run and not just sit for a very long time or you have to dich with them.

The thing is that the EFI when dialed in run all the time.

As far as the gas mileage it never meant anything to me.

Bob B

[colingreene]

EFI is the only way to go if you dont mind spending the money.

[raynekat]

MFI is good for power, but not fuel economy or low emissions. Modern EFI will mop up the floor with carbs and MFI when it comes to those 2 measures.

[morgan_harwell]

MFI will not get better MPG or Emissions than would Webbers, but
maybe slightly better throttle response, and maybe less fuel smell.

If your 2.2 was not already a MFI engine, the cost to convert to MFI would be mega $$$$ [ouch!]

[horizontally-opposed]

Appreciate the replies so far. Have driven MFI—I almost wish I hadn't!—but have not lived with it.

Agree that EFI mops then floor with MFI in most regards, with maybe the only exceptions being 1) fuel pressure > throttle response and 2) noise of that injection pump, particularly right behind my head. Probably the best-sounding Porsche street car I have driven this side of a CGT. Certainly one of them.

As to price: No six induction is cheap anymore. Not PMO, not MFI, and not EFI. But MFI is indeed nutty. Last I asked, it seemed like $12k~ to collect, restore, and install. And that was years ago. What's on there now is probably the cheapest option, which is old Webers—but even these aren't cheap anymore and I suppose they can be sold to offset some of the move to EFI. Already have Clewett's crankfire trigger with Electomotive "coil" setup, but the rest of his setup isn't going to come cheap. Do like that it looks like it would work under a factory airbox while looking like carbs. Hmm…

[Sway Bar]

Interesting...I think most of 6 drivers don't really worry about efficiency and emissions, especially on 30 plus year engines:)

A small displacement engine on carbs tuned properly can be quite fuel efficient and not smell of fuel/etc. of course never as close as EFI and you have to adapt your driving style.

MFI is kinda the precursor to fuel injection and very rudimentary. Great power band but you drive it almost on and off throttle. Due to fuel injectors at 220psi you get better atomoization and fuel burn for efficiency and of course smell over Carbs but still way short of EFI.

I've done Webers- Simple, quick technology, pain to initially tune and LOTS of compromises.

I've done many MFI- T/E/S, even a real 2.7RS, and my own built 3.0L. Complicated to understand at first and to tune properly. But man that throttle response and sound in addicting.

That being said, unless you have an affinity or like to play with these technologies EFI is the way to go for the best of both worlds. Check out X-Faktory (Al Kosmol on Pelican) he's created some really cool EFI independent throttle body kits for small displacement Porsche (2.0L and up). I haven't seen any with small displacement try this yet but lots are raving about EFI on their old motors.

For me, regardless of the induction, I'm as often as safely possible into 6K/rpm so emissions and efficiency are until the next fill up (IMG:style_emoticons/default/lol-2.gif)

Cheers,

Marlon

[SirAndy]

Cross country I got a little better than 25 mpg with the 3.2 and stock efi.

Same for my 3.6, i get 25mpg on my road trips. That's fully loaded with gear and two people in the cabin.
(IMG:style_emoticons/default/bye1.gif)

[roblav1]

My 2.2E targa MFI got 17 mpg highway back in 1982. Carb engines got about the same. No doubt MFI is cool, but crazy expensive.

[Charles Freeborn]

https://rasantproducts.com

[gereed75]

I have been collecting parts for a few years now to do an EFI system using MFI throttle bodies and the MFI injector ports in my 2.4 heads.

I have a set of MFI throttle bodies and stacks and they can be had for cheaper than most of the offerings on the market for ITB’s and you can bolt right up including linkages and retain the classic Porsche look and airbox/filter options.

From there I plan to use Rasant stuff. This has been done successfully by many. Al Kosmal has done it at least once, Jamie Novak several times and others over on Pelican. Jamie sells adapters to fit modern electric injectors in MFI injectors ports.

http://classicautowerks.com/mfi-injector-adapters

Overall cost should be around $6000.00. Selling Weber’s will recoup 1/2 of that.

Will be cool if I ever get around to actually finishing it instead of talking about it. Current carbs are tuned ok and Too many other projects.

[Chris914n6]

Cross country I got a little better than 25 mpg with the 3.2 and stock efi. Same as my big Ford Escape. One cause of the lower mileage is the increase in speed limit across the different states. At 85 mph you are way past the inflection of the drag curve. But crossing Nebraska, you feel silly not keeping up with the Jeeps.

My 914 with 97 Nissan 3.0L will do 29 mpg @ 90 mph between Reno & Vegas, stock ECU.

My Nissan 3.5L swap will get full aftermarket FI, MS3Pro EVO. Allows a few different tunes (street, track, highway). I can run a bit lean at 90 mph for mileage or a bit rich for cooling on the track. Also the software has 'autotune' to make initial setup & tuning easier.

You can use whatever intake hardware that fits, as the controls such as TPS MAF/MAP WBO2 TEMP INJECTORS all can be GM or Subaru or in my case stock Nissan.

I'll be all in for about $1500, which is likely cheaper than the dinosaur Porsche factory FI.

[stevesc_us]

Pete,

You’ve seen my car at the EASY get togethers and have probably heard me rave about how much I love my EFI conversion with PMO ITB’s and COP’S on my 3.2 conversion in my 73 long hood. Next time we meet up I will let you take it for drive to see what you think.

For me, in addition to the significant performance boost from the conversion, which I wasn’t expecting, the other main reason I did it was to give the engine bay that old school vibe since the PMO’s look just like carbs plus I love how uncluttered the engine looks. See for yourself.

[porschetub]

I have been collecting parts for a few years now to do an EFI system using MFI throttle bodies and the MFI injector ports in my 2.4 heads.

I have a set of MFI throttle bodies and stacks and they can be had for cheaper than most of the offerings on the market for ITB’s and you can bolt right up including linkages and retain the classic Porsche look and airbox/filter options.

From there I plan to use Rasant stuff. This has been done successfully by many. Al Kosmal has done it at least once, Jamie Novak several times and others over on Pelican. Jamie sells adapters to fit modern electric injectors in MFI injectors ports.

http://classicautowerks.com/mfi-injector-adapters

Overall cost should be around $6000.00. Selling Weber’s will recoup 1/2 of that.

Will be cool if I ever get around to actually finishing it instead of talking about it. Current carbs are tuned ok and Too many other projects.

What is your MPG with your 2.2? mine with good tune is really crap ?
Sorry no intent to hijack from the OP.
(IMG:style_emoticons/default/beer.gif) .

[horizontally-opposed]

My 2.2E targa MFI got 17 mpg highway back in 1982. Carb engines got about the same. No doubt MFI is cool, but crazy expensive.

Yep, I'm in the teens with carbs—and they're dialed in. Seems ridiculous for a car that weighs 2100~ pounds. While fuel economy is near the bottom of my list of "must haves" in my 914 (and thus I am not in any rush), K5 Blazer fuel efficiency sort of grates on me.

And here I thought I was making a funny about the mpg, but… https://ck5.com/forums/threads/good-fuel-ec...y-on-k5.144786/

Pete,

You’ve seen my car at the EASY get togethers and have probably heard me rave about how much I love my EFI conversion with PMO ITB’s and COP’S on my 3.2 conversion in my 73 long hood. Next time we meet up I will let you take it for drive to see what you think.

For me, in addition to the significant performance boost from the conversion, which I wasn’t expecting, the other main reason I did it was to give the engine bay that old school vibe since the PMO’s look just like carbs plus I love how uncluttered the engine looks. See for yourself.

Your 73 is gorgeous, Steve, and I'd love to take you up on that.

There are a lot of relatively new and interesting EFI options right now, from Clewett (already have their crankfire ignition trigger with Electromotive) to Rasant to several others. Some of the newer ITB hardware is really beautiful, too, but I have to say my leanings are toward the PMO hardware you have due to compatibility with the factory airbox and likelihood of long-term support. The promise of long-term support is where carbs, MFI, CIS, and Motronic shine bright—but only two of those were offered with a 2.2.

What is your MPG with your 2.2? mine with good tune is really crap ?
Sorry no intent to hijack from the OP.
(IMG:style_emoticons/default/beer.gif) .

No apology needed! This is very much the kind of discussion and data points I hoped for. (IMG:style_emoticons/default/beerchug.gif)

[gereed75]

My carbed 2.4 in S trim runs good, pulls smoothly from idle to 7000 rpm and drinks gas like crazy. Never really actually checked mpg but estimate low teens.

A throttle body is nothing more than that - a body that holds a throttle plate and facilitates linkage. The MFI ones provide an idle air adjustment circuit and I modded mine so that each has a vacuum port. Nothing more or less than what the PMO’s provide for more $. And you cant get more “compatible” or correct looking than using what the factory used for period fuel injection.

Steve, bad ass street sleeper hot rod BTW! Righteous

[roblav1]

A problem with carbs and MFI is that a lot of unatomized fuel ends up in the crankcase over the miles. 3000 mile oil changes become a requirement.
Also, the cheapest decent throttle bodies are motorcycle... 1999 to 2000 GSX-R 750 or 1000 depending on the size you want. Triumph ITBs require a manifold. I did this on a 3.2 back in 2012 with megasquirt (which I'll never use again).