FI Insert & Retrofit

triplesn8s · 06-09-2005, 06:34 AM

Hey Folks!

I have been kicking around retrofitting a Megasquirt using the MFI manifolds from my 72T. In order to clear the manifold mount to the head I will likely have to machine some sort of injector sleeve. I was hoping to just buy a new steel sleeve insert for a late '73 with the newer fuel injection system.

Apparently these are not available separately of the head. Does anyone have one I can borrow/buy for the purpose of mocking up the retrofit and designing a sleeve?

Has anyone ever seen one out of the head? Are they the same OD & thread as the MFI injectors?

TIA,

Bill

kenikh · 06-09-2005, 07:41 AM

I've been thinking about the same thing for quite a while. My best guess is that it could be done if one were to machine some injector bungs like the ones Tony Bitz has on his CIS to EFI kit. Seems like it would not be that hard. The throttle response of having those individual TBs w/ EFI is enticing, isn't it?

You could then graft on a fuel rail and be off to the races with the MegaSquirt brain.

triplesn8s · 06-09-2005, 12:14 PM

You understand my motivation. Stock looks & 6 big beautiful butterflys giving RIGHT NOW throttle response. The problem is the fat-bodied electrically driven injectors will interfere with the mounting flange on the manifolds if I try to machine the injector bunghole into the heads. I need to sleeve them and back them up just a tad.

I was hoping to be able to dimension one of the stock head-mounted bungs from a '73.5. If I can find one...

914timo · 06-10-2005, 03:36 AM

This is what I have been thinking about. Spacer between throtle bodies and cylinder heads with welded bosses for injectors (not in the pic).

jpnovak · 06-10-2005, 05:44 AM

There is an easy way to do this though it is not cheap. YOu will have to find some injector blocks and install them under your throttle bodies. This will require installing new longer intake studs and also plugging your MFI injector ports with a suitable plug.

Search for 930 style injector blocks and you should find what you are looking for. I don't know if you will have clearance issues with the linkage and I assume you will have to extend the control rod from the tranny into the engine bay.

triplesn8s · 06-10-2005, 05:59 AM

Timo,

I like your idea. I could get away with much shorter spacers, say 3/4", and machine them for clearance. Being steel removing a little extra material for clearance shouldn't be a problem. What I am trying to avoid is cutting & weakening the magnesium manifold. I believe magnesium gets brittle.

Then again I could probably just do what you have on a shorter scale. Hmmm. Seems you have the better idea.

Did you buy those steel flanges somewhere or did you have to have them made up. I have a lathe so if I can buy the flanges making up the rest is a snap. Pierce Manifolds maybe?

Thank you!

kenikh · 06-10-2005, 09:55 AM

Looks like someone did this a few years ago, too:

3.0RS...spoke with andial

triplesn8s · 06-10-2005, 10:28 AM

Wish I could zoom that photo a bit. It looks like the may still be placing the injector in the head instead of the adapter.

kenikh · 06-10-2005, 10:29 AM

It looks like it is in the head to me, too.

triplesn8s · 06-10-2005, 10:34 AM

BTW Where do I find Tony Bitz & his bungs? Maybe he would separate them from the kit since I am doing something a little different.

Er.... I am not sure how that sounded...

kenikh · 06-10-2005, 10:37 AM

http://bitzracing.com/index.html

Are you perhaps thinking of cutting down some CIS runners and welding on a mounting flange for TBs?

triplesn8s · 06-10-2005, 10:51 AM

Ummm... Now I am! Do they stay vertical for enough height to make it work? Is the intake port for a CIS head round or does it have a 'cutout' for where the injector comes in?

kenikh · 06-10-2005, 11:07 AM

Almost. Since they are solid aluminum, you could cut the tops off, weld on the flange, then drill and ream the necks to be perfectly vertical. Voila. As far as the cutout goes, I am not sure, but I would assume so. I was going to buy a set recently but got beat to the punch. They went for $25(!) on the GruppeB site.

jpnovak · 06-10-2005, 01:04 PM

yes, the CIS system to make an injector block will work.

Tony's injector bungs will not fit into an MFI head. You would have to drill them larger to seat the o-ring for an EFI injector.

914timo · 06-12-2005, 11:04 PM

Quote:

Did you buy those steel flanges somewhere or did you have to have them made up.

No, my friend laser cut them for me.

Yes, those tubes are too long. It is only a mock-up in the pic.

Porschekid962 · Porschekid962's Garage

why not the jerry woods "madonna" setup? injectors go at the very top of the stacks in machined metal cups that look like the crazy madonna breastplate. sits inside the top of the air filter cover and voila. there is a pic of this in the bruce anderson book.

Tim Walsh · Tim Walsh's Garage

I wouldn't be comfortable running injectors above my throttle plates. The first itaration of the cold start injectors on the MFI cars had injectors in that location and were quite prone to fires. When the injectors are below the throttle plates then you just close the throttle and the fire dies.

tbitz · 01:00 PM

Bill,

I sell EFI injector bungs with Viton O-rings for the DIYer.

Just thinking out loud here, but what if you drilled oversize holes then mount EFI injectors on the EFI bungs, mounted into the fuel rail so all three are aligned, then stick the EFI bungs into the MFI manifolds and have someone tack them in place with a TIG. Remove the EFI injectors and then finish the welding.

You need to tack them in place with the fuel rails, and injectors because if the alignment is off you'll never get the three injectors to fit in the fuel rail afterwards.

If the spacing for the MFI injectors is 118mm, then you can use my fuel rails. The fuel rail mounting brackets probably wouldn't work, but it shouldn't be too hard to fabricate something.

Cheers,

NevenM · 08-03-2005, 02:00 PM

Hi

Is there any advantage in putting the EFI injector where the MFI one was (the MFI were timed to hit the valve before it opened) but a megasquirt is non sequential so it would build up a charge close to the valve.

Also with Timo's mock setup haven't you essentially got 'high butterfly' TB's, OK you'd have to fab or purchase some horns but you could run wild cams

Just thinking out loud

Neven

tbitz · 08-03-2005, 03:26 PM

I'm not no expert and have no real data comparing sequential injection to batch fired like MegaSquirt, but I say that at high power settings it probably makes no difference.

Here is why I say this. At high power setting the injectors are operating at high duty cycle, which basically means they are open for most of the duration of the engine cycle. If the intake cycle is about 25% of the engine cycle duration, and the injectors are open for something like 75% of the engine cycle, what difference does it make when they open? They will be open for longer than the intake cycle anyway.

I would say that sequential injection would only make a difference at low injector duty cycles (ie: idling).