3.2L Carrera - PMO Carbs with Bosch Motronic or MSD?

[polizei]

Guys,

I'm in the process of converting my 3.2L Carrera into a twin-plugged 3.4L with higher compression. My goal is to build a performance street car that is very reliable day-to-day and fun to drive at the occasional DE. I'm interested in replacing the stock induction system with one that allows the engine to breath better and be more responsive.

My budget does not allow me to go with a fully programmable ECU and ITBs, so I'm considering PMO Carbs. Does anyone have real world experience in moving from Motronic to PMO Carbs w/ MSD for ignition? Or how about PMO Carbs and maintain Motronic for ignition? How much of a compromise is this in terms of reliability over Motronic? Does anyone know if Steve Wong will program chips for this?

I couldn't find much information on running PMO Carbs with Bosch Motronic. Interesting article here: Investigating conversion 911 Motronic with Carbs. « The Porsche Independent Repair. Here's a thread in which a few Pelicans refer to the possibility of PMO Carbs with Bosch Motronic, but no documented install is mentioned: 3.2L conversion to PMO Carbs - Ignition Options

How much time and cost is involved with installing/tuning PMO Carbs?

Thanks Guys

[larrym]

carbs will require different cams as well - you can't just bolt 'em on & expect it to run strong

.

[polizei]

Originally Posted by larrym

carbs will require different cams as well - you can't just bolt 'em on & expect it to run strong

I'm planning to change cams as a part of the build. Thanks.

Bump.

[Tippy]

Lets see here:

1. MegaSquirt II ver 3.57 = $272 IIRC in kit form (assemble yourself)
2. Crank trigger pulley, Ford EDIS-6 ignition system, VR sensor/bracket, wires, etc = $400
3. Various sensors = a little >$100
4. MS main harness = $70
5. Clewitt TPS = $140

Total = a little >$1000

Used, cheap Triumph motorcyle TB's and injector blocks = $??

Isn't PMO's like $3500?

Wouldn't it be cheaper to do the fully programmable EFI with TB's? I might be missing something.

[polizei]

Originally Posted by Tippy

Lets see here:

1. MegaSquirt II ver 3.57 = $272 IIRC in kit form (assemble yourself)
2. Crank trigger pulley, Ford EDIS-6 ignition system, VR sensor/bracket, wires, etc = $400
3. Various sensors = a little >$100
4. MS main harness = $70
5. Clewitt TPS = $140

Total = a little >$1000

Used, cheap Triumph motorcyle TB's and injector blocks = $??

Isn't PMO's like $3500?

Wouldn't it be cheaper to do the fully programmable EFI with TB's? I might be missing something.

Tippy - My guess is that the cost of parts for carbs versus ITBs with programmable EFI is about the same. Installing and tuning carbs is cheaper/faster.

I'm curious to hear anyone's real-world input in converting from Motronic to Carbs.

[RWebb]

you mean converting from Motronic to Carbs while retaining the computer?

or just in general? if the latter, there are numerous threads

I would (did) twin-plug it also.

[polizei]

Originally Posted by RWebb

you mean converting from Motronic to Carbs while retaining the computer?

or just in general? if the latter, there are numerous threads

I would (did) twin-plug it also.

Hi there - I'm interested in both, but more so in Carbs with Motronic for ignition. I'd like to understand the pros/cons of keeping Motronic.

[polizei]

Bump.

[RWebb]

read Steve Wiener's web site - rennspeed?

[rusnak]

Jeez, the L-Jetronic already gets you there with reliability, and 1.0 lambda fuel mixture. Why screw It up with carbs, unless you are talking about massively changing engine parameters and hence actually NEED carbs? What is the point of this build?

[polizei]

Originally Posted by rusnak

Jeez, the L-Jetronic already gets you there with reliability, and 1.0 lambda fuel mixture. Why screw It up with carbs, unless you are talking about massively changing engine parameters and hence actually NEED carbs? What is the point of this build?

I've got Motronic - not L-Jetronic. Putting aside whether carbs are right or wrong, I'd like to understand the pros/cons of using Montronic for ignition versus MSD.

[Flat Six]

Originally Posted by polizei

I've got Motronic - not L-Jetronic. Putting aside whether carbs are right or wrong, I'd like to understand the pros/cons of using Montronic for ignition versus MSD.

Don't want to speak for rusnak, but Motronic is an evolution of L-Jet and lots of guys treat them as mostly interchangeable terms since they're so similiar. In many cases (e.g., AFM, ICV) the discussions are identical and the Motronic/L-Jet distinction is irrelevant.

Essentially Motronic digitally integrates igntion and FI; in L-Jet systems they're -- well, not independent of each other -- but maybe best described as separate but coordinated.

[stownsen914]

I didn't see if mentioned here, but some years back there was a mass flow meter mod that could be done to the 3.2 engine, that with a Motronic/DME chip and a free flowing exhaust (e.g. headers), that you could get 250 hp or more from an otherwise stock 3.2 motor. It might have been made/sold by either Welt

I also recall from Bruce Anderson (maybe his 911 book) that he mentioned that bolting 46 mm Webers, headers, and megaphones on an otherwise stock 3.2 Carrera motor made like 260 hp at 7000 RPM. I remember being impressed with that. This was back when Webers were still in production and relatively cheap, while was very expensive, of course.

Edit - FYI, just noticed a thread over in the Engine Rebuilding forum mentioning the mass air flow mod.

Scott

[Flat Six]

Originally Posted by RWebb

read Steve Wiener's web site - rennspeed?

Rennsport Systems (Rennsport Systems | Porsche Performance Systems and Support)

[JeremyD]

My single plug 3.4l - motronic pulled 287hp and maintained diveability - what about smog in PA? Big cam won't pass smog - so what would be the point?

Oh Dyno we will go...

my 3.4, in blue, compared to Ralph's 3.5, in red, compared to a bone stock 88 3.2 with a euro premuffler and stock chip, in green.

[lindy 911]

"motronic pulled 287hp and maintained diveability"

Graph shows 244hp; not 287hp

[JeremyD]

244 at the wheels

244 at 15% diveline loss - 244/.85 = 287

[lindy 911]

My bad; I always thought we looked at RW numbers...

[polizei]

Originally Posted by JeremyD

244 at the wheels

244 at 15% diveline loss - 244/.85 = 287

Jeremy - I'm curious to hear more about your build. What displacement, compression, cams and induction are u running?

[polizei]

Originally Posted by JeremyD

244 at the wheels

244 at 15% diveline loss - 244/.85 = 287

Jeremy - I'm curious to hear more about your build. What displacement, compression, cams and induction are u running?