Advice on EFI injector to replace MFI
 

I am rebuilding/upgrading my 72 2.4L 911T to a 2.7L 9.3:1 with Mahle 90mm Nikasil cylinders and pistons and modified S dc40 camshafts from camgrinder. I am also removing the MFI unit and replacing it with EFI using the same heads. The plan is to use a Motec to control EFI and ignition. I need to purchase EFI injectors and machine the threaded injector holes in the head to fit (see picture).

Which EFI injectors should I use for this? The mechanical injectors (also in picture) seem to be significantly longer than electronic injectors that I am familiar with. I have heard there are a couple of choices for the EFI injectors. One choice being Bosch and the other being some Ford Mustang injectors that are affordable and work well in this application.

I also expect (but don’t know for sure) that the fuel pump feeding the MFI pump is not appropriate for use with the EFI. As such, I also need some suggestions on a good fuel pump for use with the EFI. Do any of you fellow pelicans have any experience on EFI injector choices and fuel pump choice that may be helpful for me?
http://forums.pelicanparts.com/uploa...1140369782.jpg

I don't think you'll want EFI injectors in the heads. Too HOT. I would look at something between the head and throttle body. Traditional EFI injectors are intended to be installed in the manifold and cooler the better.

Don't stop thinking, many have looked into this and some have accomplished it. Some have even installed them above the TB and in the air cleaner.

There are a ton of manufactors and Ford uses the Bosch style. You will need to decide between peak and hold (OEM Porsche low impedence) and the low impedence style like many domestic OEM (Ford) use.

I am under the impression that there is an injector that has successfully performed in this application (connected to the head below the throttle body). I could be mistaken as I have not actually witnessed such. Is the heat concern you expressed a melting or malfaction of the injector or a vapor lock issue?

MFI fuel pressure is 1 bar, relief valve opens at 2 bar. Most EFI run three or four times that, you will need a new pump.

Thanks John, that confirms it then, I need a new fuel pump. Got any suggestions?

Along with heat (no expert here, just have heard issues) there is an issue with spray in comparing high psi MFI and lower psi EFI. The droplet size and spray patterns are dissimilar. That is the idea behind Jerry Woods installing the injector up in the trumpet so that it would have better time for the fuel to mix. Obviously this is an art to some degree with trade offs. Direct injection seems to be the trend these days much like a diesel so trends are shifting.

I by no means am trying to state that it won't work. I guess I'm simply sharing my concerns as I've thought of this same conversion. Do some searches because his name excludes me right now, but someone on here has done a MFI to EFI conversion.

:)

I am planning a similar conversion.

I will watch this thread with great interest & contribute if I can.

Keep smiling, you own a Porsche.

Len

:)

You can buy a used set of CIS runners and throttle and make a custom intake manifold and fuel rails.

You can also add the CIS to EFI conversion blocks for 930's though the port size might be off outside of custom sizing.

It has been a couple of months and the longblock is finally together for me (my first). Here is a picture of the challenge. Now which EFI injector will work in those heads? The injector sure needs a long snout and possibly a high tolerance for heat. http://forums.pelicanparts.com/uploa...1146317234.jpg

:)

Still watching this thread & will contribute when I can.

I have some spacer blocks that were made up to accept Bosch EFI injectors with a fuel rail to hold them in place.

I will try to get some pics posted in a few days.

Cheers,

Len

It would be great to see those pictures Len. I am starting to look for new throttle bodies but such an option is proving to be expensive! At this moment I am hoping to find a TMW 3003 Throttle body.

OK, here are a couple of pictures of the progress so far.http://forums.pelicanparts.com/uploa...1148094396.jpg http://forums.pelicanparts.com/uploa...1148094538.jpg

subscribing

subscribed also. This is good stuff...

Anything furtrher on this? What injectors did you end up using

Don't have the numbers available on the injectors at the moment but these are the blue top injectors made for the Ford Mustang V8. From the research I have done these are used much in racing applications. All the internet sites list these as no longer available. The guy I bought the fuel rails from had a few new injectors on hand in the shop.

As far as other progress, the wiring harness is almost finished. this includes the sensors for throttle position indicator, barometric pressure sensor, air temperature, injector control and crank position. All this to connect to the Motec control unit.

Makin a little progress all the time.

Who did you get the rails from? And how did you address the length issue?

Good stuff. Keep at it.

What about the spray pattern of the injectors? I looked into a solution like this a while ago, and when I worked out how far back the injector nozzle would be it looked like the injector would spray a large amount onto the MFI-injector-hold-adapter-thingy. Perhaps not a huge deal but not ideal...

Injectors spray in a wide pattern. If you mount those injectors there I believe you will disrupt the pattern. The spray will hit the sides of the tapped hole and turn to dribble.

If you notice the MFI injector has a long snout that places the tip of the injector inside the port.

You should get some turbo blocks to mount the injectors and then notch the heads port like a CIS or MFI head.

Chuck, The rails appear to be homemade, see the pictures above, not sure about the length issue you question but assume you mean the length of the injector in the threaded port. This intake unit is from an engine that allegedly performed well (I have no real proof). We will see how well it works when I get it all going.

Mr Beau, I too am concerned with the "injector-hold-adapter-thingy".

Bobboloo, I too am concerned about the spray pattern and hitting the threads inside the bore. I'm not familiar with the CSI head you mentioned... nor do I know what a turbo block is... By notching the head are you suggesting to further inset the EFI injector deeper into the head? if so there is only a quarter inch or so that can be further recessed. What I have heard but not confirmed is these injectors have a more narrow pattern... just not sure it is narrow enough to avoid the current injector port threads.

Thanks for the interest guys.

I've attached a picture of a CIS head so you can see the notch for the injector. It's on the leftside in the picture.http://forums.pelicanparts.com/uploa...1151790733.jpg

I can't find a pic of a turbo block. They're not expensive. They mount between the intake runner and the head on a turbo motor. This would be between the throttle bodies and head on your motor. All the block does is hold the injector and isolate it from the heat of the head.

They come in 32mm I believe since that's the turbo port size but they should be easy to port.

This was my solution a while back; Turbo injector blocks. The injector blocks would have added 2 inches to the overall height.

http://forums.pelicanparts.com/uploa...1151800573.jpg
http://forums.pelicanparts.com/uploa...1151800621.jpg

I see that the blocks Will R. has raise the injector higher than the old stock Turbo CIS blocks. With his you don't need to notch the head.

Will, are those aftermarket?

The blocks are made for the Turbo EFI conversion. They replace the oem plastic blocks. These are made from aluminum and accept EFI injectors.

Sounds like there are a couple "turbo" block options out there. What are the sources?

I have a similar MFI -> EFI conversion in the works and will consider this option.

Hmmm, those blocks look like a good project for my CNC mill, of course I've been toying with the idea of just building ITB's but getting the throttle plates right is a lot of work. Where can I get one of those blocks to look at?

I think the Ford injectors have a 30 degree spray angle so there will be a lot of wall wetting with the original solution. When I was looking into this I had bought some motorcycle injectors that were small in diameter and seemed to have a more extended tip which could possibly work in the existing MFI injector holes. I then moved to Europe and wasn't able to continue with the project.

There's a picture in Bruce Anderson's book that shows EFI injectors placed at the top of the stacks. This isn't ideal from an emissions standpoint but is great for power (lots of evaporation and cooling going on).

Bump back to the top for an update?

I am a complete amateur in these matters, but with injectors that close aren't you almost going to have the same potential problems as you would with direct injection? Among other things, needing VERY high pressure injector rails, if modern diesel engines are any kind of example.

My understanding was that Direct in jection injected directly into the pressurized cylinder. It looks like these are injecting abobe the valve, so they won't see the elevated cyclinder pressures.

Anything new on this?

enrolling

Bump for an update?

Bobboloo... Thanks very much for the lesson on CIS heads
IRNWILL... Thanks for sharing the turbo blocks idea I will keep that concept in mind
Mr Beau... Thanks for the info on the ford injectors and sharing the info from Bruce Anderson's book

The fuel rails are now complete. Have added all the sensors for the Motec, air temp, engine temp, baro pres, throttle pos, O2 sensor (indy car version), wired them all and the injectors plus the MSD unit. Everything is ready to go and back in the car. Now need to program the Motec unit and fire her up.

She is looking good to me, here is a pic just before putting her in the car.http://forums.pelicanparts.com/uploa...1158893763.jpg

All right, keep us updated I have pieces all over just waiting to decide how to go forward with fuel injection on my engine, and this seems to be a nice combination of 'old' and new

Update: I'm back on the road again! Total time spent to remove, rebuild and reinstall the engine has been exactly a year. The EFI appears to be working fine however we are still tweaking the fuel maps in the motec unit. I am in the breakin period and anxiously awaiting a full dyno test and expert tuning in the near future. The engine feels very different from its original state 2.4T with MFI. Much more throaty sound and acceleration is also better but I am keeping it below 5K RPMs during breakin. Now I need to take some time to drive and evaluate things overall. Here is a picture of the car and the engine.

Whoops, here are the picshttp://forums.pelicanparts.com/uploa...1165462281.jpg http://forums.pelicanparts.com/uploa...1165462334.jpg

Looks good, but I think we jumped over a couple steps. Looks like you did not use injector blocks between tbodies and heads, and have installed EFI injectors into the original MFI holes.

Can you explain what you did (injectors used) and post some pics with closeups of the injector mounting.