2.4L Mounting CIS intake for EFI Conversion

tbitz · 01-17-2019, 12:34 PM

Hi Folks,

I've been asked a few times if it's possible to install CIS intake on an earlier non-CIS engine for EFI conversion. One fellow did convert his 2.4L to EFI using CIS intake with some adaptor plates. Some details here:
https://www.bitzracing.com/gallery/James_72_911T_2_4/

And so, I'm looking to fabricate such adaptors to mount CIS intake runners on the earlier non CIS engines for possible EFI conversion.

The details of the problem with mounting the CIS intake runners directly to the heads, is the injector spray would be obstructed by the head. On CIS heads, there is a cutout for the injector in the port, where non-CIS would just have a circular port. So an adaptor plate needs to be created to raise the CIS runner so the spray directs the fuel into the head opening, and not hit the head.

Here is an image from a Google for a 2.7L CIS head showing the cutout for the injector:

I have a CIS runner from a 2.7L so I can measure and model that side, what I need is the port diameters for earlier non-CIS heads (2.0L, 2.2L, 2.4L). Also looking for any reason why this is a bad idea, other than converting a 2.4L to EFI is a sacrilege and will be punished by the Porsche gods

tbitz · 01-17-2019, 12:36 PM

Picture of CIS head didn't come through...try again:

tbitz · 01-17-2019, 01:31 PM

Below is a pic of the 2.7L CIS runner with the cutout for the injector. This has a 34mm opening.

I measure the stud spacing at 66mm centre to centre. Does anyone know if Porsche kept this stud spacing on all early 911 engines?

Trackrash · Trackrash's Garage

The 2 - 2,4L Ts and Es had 32mm intake ports. The S had 36mm ports.

This sounds like an interesting project. I would wonder if the longer runners would benefit the mid-range torque.

mb911 · mb911's Garage

The nice thing is allot of 2.4's have MFI ports and one could easily tap into those and then use carbs or even the mfi tbs for air intake.. Thinking about doing this with mine with your setup Tony.

tbitz · 01-17-2019, 06:52 PM

ok thanks. So 34mm from the CIS runner side, tapering down to 32mm on the head.

I've seen pictures of the heads with the ports for the MFI injectors right in the head. Probably need to fabricate a bung to fit the EFI injector in there. For now, I'm gonna focus on using a CIS intake, as that fits with the other parts of the EFI kit.

I got the CIS side of the adaptor plate modelled.

Printed it on paper and looks like a good fit.

tbitz · 01-18-2019, 05:35 PM

Here is a 3D model I have for the spacer so far.

Also created a model of the CIS intake runner with an injector and a fuel spray. A 10degree spray pattern clears the spacer walls and goes directly into the 32mm intake port.

Trackrash · Trackrash's Garage

Quote:

Originally Posted by tbitz

Below is a pic of the 2.7L CIS runner with the cutout for the injector. This has a 34mm opening.

I measure the stud spacing at 66mm centre to centre. Does anyone know if Porsche kept this stud spacing on all early 911 engines?

I'm using the same Weber manifolds that I used on my '71 now on my '78 SC motor.

tbitz · 01-19-2019, 01:40 PM

Thanks Gordon, so looks like one size will fit all.

I also ran some cross sections to see spray pattern.

targa44 · 01-19-2019, 09:47 PM

Tony,

Your modeling makes me think of the Accel injectors you recommend (or used to). Have you tried using any of the EV6 type injectors?

tbitz · 01-20-2019, 05:19 AM

No, I haven't tried the EV6 style injector.

The CIS to EFI bung was designed for an EV1 style injector. The wide part of the injector seats on the top on the bung preventing it from going down any further. I haven't tried the EV6 injector, but I suspect the narrow EV6 injector would most likely go deeper into the bung with the o-ring potentially popping out the bottom.

Can see what I mean in the photos here of the EV1 injector:
https://www.bitzracing.com/products/injector_bungs/

tbitz · 01-20-2019, 11:47 AM

I printed a prototype for fit. Looks to be a perfect match. I'll open up the top and bottom diameter by 0.5mm incase there is a mis-alignment during installation of the intake to head.

Schmitt RS · 02-06-2020, 06:34 AM

Man Tony this just what I am looking for! Great work so far. Can't wait to see how it turns out.

tbitz · 02-06-2020, 07:46 AM

Thanks!

Below is a top view of another prototype showing inside as it transitions from the CIS runner to the head.

I saw your email on the Bitzracing.com web site. I'll send you a reply from there.

Tony