Just a quick update. MFI to EFI bungs are in and will be using the carbs will just be throttle bodies and port injection.

Have at those questionsClick to view attachment

You’re being a tease

What ECU?

Planning to run Alpha-N control (Throttle Position only)or are you using something like the stock air filter canister with a MAP sensor and Speed Density (SD) control? ECU maybe supports combo mode? I don’t see a TPS on that carb - does that mean you are using SD?

How easily will it be to tune?

Will the ECU support coil on plug or still running a distributor for spark? Can’t see the distributor in your photo - tricky!

What’s required for crank and cam sensing? Let’s see those sensor brackets!

Inquiring minds want to know Can’t wait to see this project progress and some documentation forging a path. I know EFI has been done before on the sixes but this one is sort of unique and something I may do with my 73.5’ 2.4L

Love the sleeper / clean look that carbs or PMO throttle bodies offer. I might want to try this with Zeniths.

Phil,

Gonna use mega squirt. I have base map’s already. I need to drill 6 fittings in the intakes for the map signal. Will not run TPS. This will be very close as far as principle as bittz racing setup except this system is more precise. It will only use map. The link I provided on the other thread is the system so am mirroring

http://forums.pelicanparts.com/porsche-911...14-mfi-efi.html

Will be watching closely. I'm still hoping to start my megasquirt project this winter but need to get a couple non-car things squared away first. I'll live vicarously through you project until then.

Why not use these?

Click to view attachment


https://store.jenvey.co.uk/heritage/heritag...ottle-body-42mm

They are a bolt on replacement for Weber IDA3C carbs. All of the EFI stuff is inside the throttle bodies.

Cool project...I was always wondering about EFI using MFI parts. Maybe I should chat with my MFI expert to see if he has any spares.

I am going the MFI components route -throttle bodies and mag stacks. In consultation with Jamie Novak and Pete Dawes and company. Motec 84, Denson coil on plug, TPS and other stuff TBD.

I'll post some pix as I get it further along.

Pretty cool - but come on $3800?

The thing I don’t get with the Jenvey’s Is where the injectors are spraying to? The angle of the injectors seems to be that they spray into a passage like a carb jet instead of directly into the air stream? Maybe I’m just not seeing it correctly but Google doesn’t seem to reveal details of their fuel flow path?

The potential to use a common set of carbs as throttle bodies and to repurpose the MFI / CIS ports on some of the early engines is what makes this proposal that Ben is showing unique vs a set of PMO ITB’s, Jenvey’s, or any number of other high(er) cost EFI solutions were you have to ditch the carbs and buy all new ITB’s

These are designed for a stealth EFI installation. They look like carbs, and unless you find the wires coming out the bottom, nobody would notice. For a factory six, this would be perfect. Hide a microsquirt ECU under the air cleaner, and nobody would notice the EFI.

The cost of EFI throttle bodies is what led me to making my own for the flat fan upgrade on my car.

Reusing MFI stacks is simple. Just fabricate a TPS mount to replace the switch at the crossbar, and make some MFI to EFI injector adapters.

I actually started on this for my old 2.4 motor. It's not hard to do. Use a 911 hall effect distributor and a toothed wheel behind the crank pulley, plus microsquirt.

Mainly cost and that I just redid a mechanical restoration on the carbs(performance oriented) and some day I may want to go back to them. I have a total of 1k into this setup.

You probably want to pull the venturis out of the carbs if you intend to use them as EFI throttle bodies. Less restriction.

Yes probably so.

Would love to see some datalogs when you get them. MAP only with ITBs on a 4 tends to be problematic, especially at lower RPM+higher throttle angle. Even with undersized ITBs you could wind up with only about 30% of the fuel map tunable. Interested to see if it works better on a 6.

Megasquirts hybrid alpha-N mode (uses speed density where you have vacuum and alpha-N where you don't) is amazing when setup properly. The trick is getting it setup properly.

Why not just keep the MFI?


I always thought it was genious.

I had a 2.4L MFI motor in my 914-6 conversion for a long tme.

The performance is great, and the sound is GLORIOUS!!!

But to live with MFI on a car you want to be a daily driver, not so good.

Typical morning startup from dead cold on a day below 40F.

Get the can of ether and spray it into the air cleaners on both sides.

Attempt to start the car. It sputters and dies.

Repeat.

Repeat.

Around the fourth time it will catch and run badly on 4 or so cylinders. So set the hand throttle to 1500 RPM to let it run for a while.

As it warms up, it will start firing on the rest of the cylinders. Ease the hand throttle down slowly as the RPM increases to keep it at 1500 RPM.

Once the engine is running smooth on all six and the oil temp starts to come off the peg, ease the hand throttle down until it idles at 950RPM.

Now you can back out of the garage and drive gently for a while until the rest of the chassis and drivetrain warm up.


Contrast that to EFI.

Get in car. Turn key. Car starts and idles on all six cylinders. Wait about 30 seconds and back out of the garage. Drive gently until the engine, transmission and chassis warms up.


To be completely transparent, I never connected the MFI cold start fuel enrichment system. They were nicknamed "the firestarter" for a reason. I have seen the stacks catch on fire because of a backfire on cold start. No Bueno.

Yea....considering it was developed so that the Messerschmidt could fly upside down and for 6 G turns....sounds like the prestart checklist and magneto start up.....


But when it runs right......sheeeez. What a sound and unmatched performance.

914 DD....naw... keep the MFI for the sound if only.

Cause I never had it to begin with.

I would like to see a complete list of parts needed.
Thanks, Matt

Ben put the engine together from scratch, using parts he obtained. The heads are mfi but he never had an mfi engine. MFI is really cool and has a strong Porsche history but it’s not for the faint hearted. Ben is in WI and puts his engine to bed over the winter. MFI is probably the worst sort of injection to let sit for months. I’m guessing one of the reasons he’s doing modern efi is so he can just jump in the car and go.

My mfi cars start much easier than is described above, but once i got my microsquirted car tuned and running well it is much easier on the fuel consumption and starts so nicely

Anyone priced a MFI rebuild?

I have a spreadsheet that I can share

Yes it’s silly expensive.


For everyone questioning why I am doing it this way.

Well I had great experience with a 3.2 ss turbo engine I built years ago that produced 400 whp and ran a rising rate fuel pressure regulator and mega squirt that was an adaption of Tony’s @ Bitz racing.com system though I used a 3.2 intake. I was impressed with that setup as it worked all the time with a simple turn of the key and ran perfectly in all weather.

That and I am trying to do this cost effective

Email sent to you

For you viewing pleasure Click to view attachment

According to my wife, boss, coworkers and kid, I'm kinda slow.

This is a FI system that look like carbs?

If true, kinda cool!

Yes sir

Ben. On your motor, what was covering/plugging the injector port prior to installing the injector adaptors??

Plugs that were a kit I remember be sold through automotion back in the day.

Vacuum fittings selected. I will have to drill and tap each manifold to get a good signal for the MAP sensor Click to view attachment

Here is what I did for vacuum fittings on the mag throttle bodies. The little brass tube at an angle on the far left throat next to the idle air bypass screw is the single stock vac port. I machined the middle and right throats for insertion of brass tubes and then used JB Weld to form a boss to seal them that mimics the stock boss.

I’ll run the six vac lines to an accumulator to smooth the vac signal. I hope to run a TPS driven alpha N and MAP signal to the Motec. Hoping to get throttle response as good or better than MFI.

Click to view attachment

You can see the injector ports on this engine I am using for mock up have been sealed with JB Weld or similar by the PO. I think the ports on my actual engine are sealed with the screw in plugs you mentioned.

That’s an idea for vacuum ports. Might look at that

I’m a bit confused.
Newbie to modifying a 6 here, but I have webers and will be doing some sort of fuel injection going forward due to car sitting for months in winter, not DD etc etc

So, mine is a 3.0 that I assume was using the old FI, but that is all gone.
Motor came with webers.

My question is, can I follow you, copy you, without modifying my heads in any way? I’m happy to get adapters for the injectors…but I’m concerned with head changes.

The 930 heads do not have an injector port like the earlier MFI "E" heads had. From what I have read there is no room on the later 930 heads to even machine a port to accept an injector.

The 930 used an injector block that bolts to the inlet port to house the injector. Those would work to hold an injector but at that point the carburetor throat spacing does not match the intake sport spacing.

Don't think that could be made to work with carbs.. Clewit makes EFI systems that use that injector block but then they use ITB' s or the stock CIS intake manifold with the correct spacing to match the inlet ports

What becomes of float bowls and other carb related items? Does everything other than the vac ports you’re putting in get plugged? Do the triple Webers have progression circuits?

Sorry you would need MFI heads to do this or some machine work

Just plugging the fuel inlets. I might remove the floats just so they don’t rattle.

Went a different route on vacuum tubes. Drill .100 hole and used 3/32 brass sleeved inside 1/8 brass and used loctite 638 cylindrical bonding and pushed them in the holes and for good measure so epoxy on the outside. Then connect the 1/8 vacuum tubing only to realize that I need to run individual lines to a manifold to ensure no reversion. I did also start on the injector harness as well. Click to view attachment

Equal length vacuum lines and manifold for a clean signal. Making headway Click to view attachment

You will need to check the map signal you get off of that block.

All ITB F.I. setups that I have played with required a TPS sensor as we had to run Alpha N below 12-1500 rpm as the map signal looks like an ignition signal at slow speeds.

This FI strategy is called blended alpha N/speed density.

More compression and big cam profiles made this MAP instability worse.

Most systems that I have worked on have 6 and 8 cylinders.

The more cylinders you have the smoother the MAP is at low speed.

You might be able to run an IAC valve (idle air control) off the block. I usually go with 3/16-1/4" vacuum lines from each runner to gain enough flow for computer controlled idle aspects.

Below the smooth signal threshold, the map sensor is not in use, but the IAC valve is, and above the threshold vise-versus.
I will commonly run the MAP off of one end of the block and the IAC off the other.

Another solution is to enclose both air filters in plenums and add MAF sensors in the entrance to the plenums, but you will significantly reduce the howl that we all love to hear from an ITB set up.


4 cylinder info next. I'm not researching 6 cylinder stuff yet.

I saw the Jenvey Heritage ITB for the 4 cylinders that hide the injectors and the TPS inside the unit. The injectors are firing into the intake just below the throttle blades at an angle. These are WAY cool but Jenvey themselves show compatibility with up to E20 which is a deal breaker for me. The little 350 cc injectors are too small IMO as well.

On PMBs website the normal Jenvey IDF (non-hidden injectors) are far more affordable.

https://pmbperformance.com/products/jenvey-...r-porsche-914-4

My big 4 cylinder with have those, 1050 cc injectors (Injector Dynamics), and run E85.

I'm betting the six-cylinder stuff is similar.

One final thought...

You could be Hybrid!

Turn the FI stuff off, pop the venturis and boosters back in, source the fuel off of the return line, and go old school in less than 10 minutes

Thanks for the input. I am following @jpnovak s blueprint on this. He has specific road map on this setup and he does these everyday with great success. I will for sure keep your thoughts in mind.

Do you need MFI heads for this to work?

Yes

Click to view attachment

Easy button,, PMO,
https://pmocarb.com/products.htm

Or Jenvey heritage. I just like to be different

I'm with you. Use what you have. Same principle.

EMPI bought the company but I don’t think they are currently available for sale.

Just saw That 2 days ago all links still worked , We have a Mfi 3.0 with the pmo Injector stacks , and they listed EFI injector style around 3k.. uses carb manifolds,
link for reference
https://www.racetep.com/manufacturer/carbs-...er/pmo-itb.html