MFI or carbs? Options

[bossboy302]

Sorry for re-asking this, but as I begin fiddling with mechanical and electrical components for my project 6 conversion, I am still pondering this decision.

The car, when finished, will be shipped to Europe where my wife and I can use it when we're there, and do some rallies, trips and such. There will likely be (months-long) periods of no use.

Have most of the necessary stuff for the build, (included with the '71E motor-entire MFI, fuel filter/console, complete electrical board, fuel pump, etc) all from 'donor' car...

But I'm beginning to sense that the complexity of MFI (transducers, fuel system, micro-switches, etc.) could prove challenging. A good set of PMO's on the other hand: basic fuel pump and regulator, MSD 6AL, and a spray can of ether may be better suited, again given the intended use.

So, I welcome thoughts and opinions-thanks

[Superhawk996]

MFI is amazing tech for that era. However, hard to fix by the side of the road or in some little European town out of the way.

I’d opt for carbs.

[Long_ago]

Agreed.
I went with new webers on my 6. For the simplicity.
Old carbs, no thanks. Tough to get everything happy and reliable.

[Cairo94507]

I 100% agree; you can always swap out to MFI when you get the car back home. (IMG:style_emoticons/default/beerchug.gif)

[r_towle]

Add in a fuel shutoff (look at the 356) so when you park it, turn off the fuel and let the car run till it dies.
This empties the carbs of fuel and gives you a better chance to keep the carbs clean in between each use.

I’m in 100% agreement on carbs .
You can fix them, and get parts, pretty much everywhere.
MFI will get you a lot of puzzled looks.

I’m thinking a lot like you, and building something similar to send abroad…..

Rich

[ClayPerrine]

You should consider an aftermarket EFI setup.


Modern, reliable easy to start, better gas mileage...


Jenvy makes Throttle bodies with all the EFI parts built in. Just add the ECU.

[NARP74]

I am guessing the newer EFI systems will cost $5k for all the parts needed. The price should come down in a while, or go up. Who knows these days.

You can use fogging oil in the carbs for better storage. Fuel shut off is a good idea too. I use that on my lawn mower and works well.

[mlindner]

bossboy302. Living in Wisconsin, time on the road is less than six months and then a big nap each year. I love the PMO's, installed a inline fuse for the fuel shut off and MSD. Nice simple setup that I understand. Best, Mark

[targa72e]

Mfi once set up requires very little attention. If you are building a factory engine spec that used MFI then all the standard settings apply. If you deviate from factory specs with different cams, compression port sizes etc then there is a fair amount of custom tuning required whether you are using MFI or carbs.
On of the other issues with MFI is that 914 has no provision for hot air to the MFI thermostat from hear exchagers. On a 911 there is a hose off the heat exchanger to the thermostat housing on the MFI. With out this provision the car will not run right when warm, if permanently set at hot position the car will not start when cold. There are mechanical cable aftermarket systems to operate the cold start enrichment as a option. So many things to consider (carbs are a pain to tune correctly for many different reasons) on induction system.

john

[ClayPerrine]

On of the other issues with MFI is that 914 has no provision for hot air to the MFI thermostat from hear exchagers. On a 911 there is a hose off the heat exchanger to the thermostat housing on the MFI. With out this provision the car will not run right when warm, if permanently set at hot position the car will not start when cold. There are mechanical cable aftermarket systems to operate the cold start enrichment as a option. So many things to consider (carbs are a pain to tune correctly for many different reasons) on induction system.

Not 100% true. The majority of 914-6 heat exchangers don't have a provision for the MFI heater, However, there were heat exchangers that Porsche had built for the 916 program with the MFI heater connection. Those got put into the spare parts channel when the 916 program was cancelled. I know this is a fact. I have a set of them I used on my 2.4L 911S MFI motor.

[vitamin914]

On my carbed '74 914-4 I have a switch to the electric fuel pump. I just shut off the fuel pump and let the fuel bowls go down before turning off the engine. The Webers have a tendency to boil over if shut down after a good run on a hot day. If well hidden, the fuel pump switch also could help if someone tries to steal the car (with carbs) - it will start go a bit and then die leaving them stuck and perplexed. Not an anti-theft guarantee but everything helps.

Fuel injection can be very reliable. I love getting into my 73 turning the key and having it fire up right away. Less cranking before starting compared to the carbs. The thought of fixing the FI scares me if it ever fails.

IF there is ever a problem it will be more difficult to fix FI stuck in the middle of nowhere. Carbs are simple mechanical, FI uses electrons and it is hard to see what the electrons are doing at the side of the road after lifting the hood.

A lot of young mechanics don't know what to do if they can't find an OBD II port to see which part needs to be replaced.

[Eric_Shea]

Modern EFI that looks like carbs. (IMG:style_emoticons/default/wink.gif)

https://pmbperformance.com/products/jenvey-...058a5&_ss=r

We didn't forget about the -4 guys:

https://pmbperformance.com/products/jenvey-...058a5&_ss=r

[Superhawk996]

EFI is nice and all but that wasn’t what OP asked about. Then there is that little issue of Tuning EFI.

I have yet to see any “auto tune” actually do what it implies. Awaiting the day. It’s getting closer but not there yet.

Still won’t have OBD with aftermarket EFI. You could actually end up in a worse situation traveling in Europe without a laptop should something go wrong. So average repair shop will be of zero help without the laptop to connect to EFI.

Let’s just say for a moment that the MS or whatever ECU takes a (IMG:style_emoticons/default/stromberg.gif) . What them? Try to import one to Europe overnight? I suppose someone in Europe may have them? You see where this is going? Open to be corrected - just thinking out loud.

[Eric_Shea]

OK, OK... Carbs to the OP?

ECU is Holley. Holley is "Self Learning" which is why we're moving all of our builds to those. In stock. Takes a crap about as often as a Motronic unit from a 3.2 Carrera or a 3.6?? (IMG:style_emoticons/default/biggrin.gif)

If we all thought out loud like that we'd be whipping horses still. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/wub.gif)

[ClayPerrine]

OK, OK... Carbs to the OP?

ECU is Holley. Holley is "Self Learning" which is why we're moving all of our builds to those. In stock. Takes a crap about as often as a Motronic unit from a 3.2 Carrera or a 3.6?? (IMG:style_emoticons/default/biggrin.gif)

If we all thought out loud like that we'd be whipping horses still. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/wub.gif)

(IMG:style_emoticons/default/agree.gif)

Modern EFI is a quantum jump forward from carbs. I understand keeping it original. But carbs were only available on a Euro 1.8L, and MFI, other than a select few prototypes, was not available on a 914 at all. And there are less people out there these days that know MFI. There are lots of people who know programmable EFI. And with a laptop and an internet connection, the builder can troubleshoot it from anywhere in the world.

EFI is the future, at least for as long as we have internal combustion engines. I could hang a pair of PMO carbs on my 4.0L engine, but it won't make as much horsepower, and it definitely won't run as well as the Motronic I have, much less the MS3Pro I am going to use.

Why do you think the OEM builders don't use carbs anymore? Because they are as outdated as buggy whips.

[Superhawk996]

OK, OK... Carbs to the OP?

ECU is Holley. Holley is "Self Learning" which is why we're moving all of our builds to those. In stock. Takes a crap about as often as a Motronic unit from a 3.2 Carrera or a 3.6?? (IMG:style_emoticons/default/biggrin.gif)

If we all thought out loud like that we'd be whipping horses still. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/wub.gif)

I get it - I like EFI too but come on - Holly availability in Europe ? (IMG:style_emoticons/default/laugh.gif)

You guys are missing the point of OPs question - not meant to rehash the carb vs EFI debate.

[r_towle]

Honestly, it does bring up an interesting reality.
First, I would rule out MFI due to lack of skilled people fixing it abroad.

Carbs or EFI….seems like a toss up that might depend upon the region.
Seems to be a lot less skills with carbs now, and us old farts have to keep helping newbies.

I’m planning to build and ship a car also and I’m going to use EFI, once I have done plenty of research. I will also carry spares.

[930cabman]

My vote goes to Webers.

[r_towle]

My vote goes to Webers.

I’m in the same camp today,,, until I learn more.
At the end of the day, what can realistically go wrong with carbs?
Not much.

I’m still focused on his use case.
Going abroad for a year, hoping shit does not break.

[JmuRiz]

I’m lucky enough to have EFI, MFI and carb expert friends near me. I have carbs but am on the fence on EFI entry cost. I should have pulled the trigger 7 years ago when prices were lower.

OP: I’m sure I can ask my MFI guru who you can talk with in NorCal if you need an MFI tech.

Having a fuel pump cutoff is a great idea. I have a petcock on my 356 but often forget to run them dry and kick myself as I have to ungunk the jets and bowls (IMG:style_emoticons/default/headbang.gif)

I’ll be in touch Eric (IMG:style_emoticons/default/wink.gif)