2.7 w full 3.2 Motronic conversion, can it be done?

[RetroSC]

I know, I know... why would you do this? I'm just brainstorming during quarantine, and after looking at my current 2.7CIS that needs sorting, maybe just ditch it. I also prefer how a 2.7 rev's over the larger motors and don't want to do a motor swap, sooo..

Could you in theory adapt a full 3.2 system, i.e, manifold, sensors, motronic brain ect, to a 2.7? I know the ports are a little smaller, so an adapter may be needed. I assume it would need a custom chip, maybe Steve Wong could whip something up?

I've read some EFI conversion threads, and it's a lot of reading. Don't really want to become an EFI tuner, so thought maybe doing the Motronic would be easier since it's all Porsche?

[MIAdragon]

I’m considering going to an ITB setup so will be pulling my complete 3.2 EFI setup.

[targa72e]

My first cis replacement 20+ years ago used the 3.2 manifolds and the electronics off a 280Z. Tuned the mixture by messing with flapper box spring. Worked pretty well. Eventually went with programable ecu (still 18+ years ago). Sold that system to a friend who ran it on his 2.7 engine with E-Cams RS pistons. He made some spacers to go from 3.2 manifold to 2.7 ports. That engine dynoed just over 200hp at the wheels. He spun a bearing on the 2.7 and replaced it with a 3.0L. That engine with 3.2 manifold and programable injection is still on the car today. So 3.2 manifold with programable ECU pretty easy. To use all factory stuff you would You would need a custom flywheel to fit the 2.7 but with 3.2 outer pulse ring. Fab a mount for the engine speed sensors. Probably would need to have custom chip made as well that was tuned on dyno. Might need to swap out to 3.2 dist (or mod the 2.7). so possible but maybe more work than worth.

john

[spuggy]

Originally Posted by RetroSC

Could you in theory adapt a full 3.2 system, i.e, manifold, sensors, motronic brain ect, to a 2.7? I know the ports are a little smaller

Billet adapter blocks for EFI 930 conversions; stock 3.3 930 intake ports are way smaller, machine out to match. Guys have also done this retaining the CIS manifold and adding fuel rails and an FPR.

A crankfire trigger wheel bolts on and is way easier than splitting the engine/trans, fitting a late flywheel, milling out the transmission window/bodging up the sensor mounts.

Originally Posted by RetroSC

I've read some EFI conversion threads, and it's a lot of reading. Don't really want to become an EFI tuner

This is the only unrealistic part. Either someone's going to have to do it for you, or you'll have to do it yourself.

How did you see that working out?

Originally Posted by RetroSC

, so thought maybe doing the Motronic would be easier since it's all Porsche?

Gosh no. Use all the sensors by all means - but ditch the Motronic.

a) it can't be readily tuned without specialist knowledge/hardware/software
b) factory 3.2 maps won't be right for the 2.7 so someone will have to tune to suit
c) it's 40 YO tech and your toaster has more CPU power.

Just about any ECU made in the last 20 years will offer a user interface, real-time sensor readings, interactive programming, logging etc. etc.

There are ways to do this with Motronic - but why try so hard to cling to obsolete tech you can't tune yourself?

Either just pick any ECU and DIY, or ask the folks you'll be paying to get it running for you what they would prefer.

[darrin]

the other issue with a 3.2 Motronic system is that the chip is optimized for the specific characteristics of the 3.2 engine it was built to support (i.e. different chips for us vs euro versions to address different compression ratio and emissions requirements of euro vs us engines) -- SO, even if you did mate a complete 3.2 motronic system to your 2.7, you'd still need to work with a chip tuner to program the motronic system to address/resolve the particularities of your 2.7

[Peter M]

RetroSC,
You will be amazed at how revvy a 3.2 becomes once you dump the Motronic and the AFM and go modern EFI, even without the expense of ITB's

[RetroSC]

Ok, so no Motronic, got it!

I'm fairly handy, done two engine rebuilds on these, but reading EFI tuning and I sort of zone out.. Sounds like that's the way to go though.

Nothing but time on my hands, maybe I'll look into some of the ITB threads.

[Peter M]

Not ITB's and not 3.2's but I think a nice introduction to efi'ing an early 911 that you may find useful.

https://rasantproducts.com/content/Manuals/Rasant_Products_Engine_Management_Installation(ITB ).pdf

[Arne2]

If your 2.7 is essentially stock, you may find the base 2.7 map that comes with the Bitz EFI kit to be close enough, although fine tuning it would make it better, I'm sure.

From the FAQ page at Bitz Racing:

The kit was originally built around a 1978 3.0SC engine, however the kit fits all the 2.7L and 3.0L engines and comes with a base map for both the 2.7L and 3.0L.

[mysocal911]

Originally Posted by Peter M

RetroSC,
You will be amazed at how revvy a 3.2 becomes once you dump the Motronic and the AFM and go modern EFI, even without the expense of ITB's

Please explain in detail what the negatives of the Bosch Motronic system are.

[RetroSC]

This seems like maybe the easiest way to EFI, and the more I read the less daunting it sounds. I could even run RS pistons and more cam down the road..

Originally Posted by Arne2

If your 2.7 is essentially stock, you may find the base 2.7 map that comes with the Bitz EFI kit to be close enough, although fine tuning it would make it better, I'm sure.

From the FAQ page at Bitz Racing:

[chrismorse]

IMHO, one of the reasons that the 2.7 is so “revvy”, or as I like to call it, “Happy”, is the stock flywheels weigh something like 11-12 pounds and the clutches 15 or 16 pounds.
I am going to shave about 10 pounds off that total and add EFI to a fresh 2.7, (dad built it stock). This will be my first venture into EFI, but I’m hopefull that a little help from the X Factory and a day on the dyno ;-)...........
Good luck

[Coastr]

Originally Posted by mysocal911

Please explain in detail what the negatives of the Bosch Motronic system are.

Great for its day, outdated now. Uses a spring paddle airflow meter, controls only the fuel and not ignition, parts like injectors are expensive and not as good as newer tech. The ecu is only programmable by someone who really knows what they are doing, to rather than by your dyno tuner with a laptop.

You can use the manifold and maybe throttle body but the AFM should be something else, also best to plan for full sequential and COP for better power, drive ability and economy.

The simplest thing is the bitz kit that converts the CIS manifold to EFI. It’s not a particularly advanced Efi solution but it is cheap and simple, and keeps the stock look if you like.

[Peter M]

Originally Posted by mysocal911

Please explain in detail what the negatives of the Bosch Motronic system are.

Oh Dave, you probably know more about Motronic than anyone else on this forum!

The proof of the puddling is in the tasting and suggest you take a properly tuned "modernised" 3.2 for a run. I'm sure you won't miss the Motronic, I haven't.