3.1 CIS to efi Turbo

mikedsilva · 01-14-2022, 03:00 AM

I'm no stranger to building a n/a motor, but have never dealt with turbos, nor put my own efi together.

The car I have acquired is a 79SC but has been 'Ruf'd' and it would be great if it went as well as it looks.
The motor was previously rebuilt in 1992 using 97mm turbo cylinders and mahle pistons. I'm not 100% sure of the spec yet, but was told 9.5:1. It runs great. Bone dry, the CIS was rebuild and it performs faultlessly.

I feel the time is right to try a turbo conversion but am really not 100% sure which way to go. Goal is a car with great torque and hopefully more performance than could be got from a n/a setup. Is 300wheel hp realistic? From reading here, a low boost (0.5 bar) setup would be a good way to go. Which would allow me to leave the motor mostly stock, but I am not afraid to rebuild it. Probably should have new head studs as I'm certain it's still running the originals!

I've found a 3.2 intake manifold, throttle body, injectors, rails etc..
For the exhaust, I was contemplating using a set of 3.2 stock heat exchangers that I have, coupled with a J-pipe.
As for the turbo, it was suggested to me to look for a Garrett 3071 with 0.63 a/r for fast spool and drivability. Whilst I have not found one of those 2nd hand, there is a Garrett 3076 not far from me for not too terrible money... could that be suitable?

Do I need to run an intercooler for a low boost setup? Could I start off without one?

For efi I am trying to decide betwen Ecumaster Classic, or Haltech Elite 750 (should this be suitable?). I've not done my own wiring before but I see Haltech offer the 750 as a premium kit with an unterminated harness that is fully labelled..https://www.golebysparts.com.au/collections/ecus-wiring-harnesses/products/haltech-ht-150604-elite-750
I have spent a bit of time on my previous car with Aem Infinity and VE tuning, so I have a little understanding there.

I'm open to suggestions for turbo, ecu, general setup, parts for sale, etc. I'm not sure if 930 J pipe use a T3 or T4 flange yet, but I guess if it's non matching a shop can rectify that fairly quickly for me.

thanks for reading?

Steve G · 01-14-2022, 07:35 AM

Have you checked to see if this is an original 3.1 from the factory?
I have one and they're super rare.
If it has 97mm barrels and Mahle high compression pistons then you might be in for a surprise. These pistons are unobtainable as they were only ever supplied to Porsche and never available on the market, if they were fitted in '92 then i've no idea where they came from. Mahle never supplied them to the public. Believe me i've tried to find some!!!
If it is a genuine conversion you will find a stamp on the block near the engine number *3.1* and there are various other subtle differences.... different CIS...oil cooler etc etc

mikedsilva · 01-14-2022, 11:07 AM

Quote:

Originally Posted by Steve G

Have you checked to see if this is an original 3.1 from the factory?
I have one and they're super rare.
If it has 97mm barrels and Mahle high compression pistons then you might be in for a surprise. These pistons are unobtainable as they were only ever supplied to Porsche and never available on the market, if they were fitted in '92 then i've no idea where they came from. Mahle never supplied them to the public. Believe me i've tried to find some!!!
If it is a genuine conversion you will find a stamp on the block near the engine number *3.1* and there are various other subtle differences.... different CIS...oil cooler etc etc

Hi Steve, being in Australia, I don't think we received the option. Also, the case doesn't have the *3.1* stamped either... I feel ok with modding it. However, all original components will be stored safely.

quattrorunner · quattrorunner's Garage

I actually think the 3076 would be better anyway. I used one for a turbo 3.0 with 6.5/1 comp (stock turbo internals) and it was lively with sc cams. Plus you really don't want too much torque down low with a 915 gearbox. .5bar would be fine, and a blast in that setting all things staying same. A blast indeed.

mikedsilva · 01-24-2022, 10:38 AM

Quote:

Originally Posted by quattrorunner

I actually think the 3076 would be better anyway. I used one for a turbo 3.0 with 6.5/1 comp (stock turbo internals) and it was lively with sc cams. Plus you really don't want too much torque down low with a 915 gearbox. .5bar would be fine, and a blast in that setting all things staying same. A blast indeed.

You might be right, but I missed out on a 2nd hand Garrett... trying to do things on a budget and sensibly (ie not buying a $150 turbo).
Considering a Pulsar Turbo...

https://www.ebay.com.au/itm/184671364647

For intake, I have found a 3.2 plenum and throttle body.. and am considering an Ecumaster Classic for the ecu.

mikedsilva · 01-24-2022, 10:40 AM

Quote:

Originally Posted by mikedsilva

You might be right, but I missed out on a 2nd hand Garrett... trying to do things on a budget and sensibly (ie not buying a $150 turbo).
Considering a Pulsar Turbo...

https://www.ebay.com.au/itm/184671364647

For intake, I have found a 3.2 plenum and throttle body.. and am considering an Ecumaster Classic for the ecu.

Am probably going to order a set of the OBX headers too.

konrad911 · konrad911's Garage

Quote:

Originally Posted by mikedsilva

Am probably going to order a set of the OBX headers too.

Mike the OBX seems to be 1.5" in diameter for primaries. This seems too low for a turbocharged 3.1 IMHO. I'm sure more experienced turbo-guys can chime in, but for a turbo you want almost as much on the exhaust as possible.

quattrorunner · quattrorunner's Garage

My first turbo headers were obx and they worked well for 3.0turbo. Also used them for the 3.3 until I wanted for heat so I swapped them out. But they made good power.

JakobM · 02-07-2022, 02:38 AM

Quote:

Originally Posted by Steve G

Have you checked to see if this is an original 3.1 from the factory?
I have one and they're super rare.
If it has 97mm barrels and Mahle high compression pistons then you might be in for a surprise. These pistons are unobtainable as they were only ever supplied to Porsche and never available on the market, if they were fitted in '92 then i've no idea where they came from. Mahle never supplied them to the public. Believe me i've tried to find some!!!
If it is a genuine conversion you will find a stamp on the block near the engine number *3.1* and there are various other subtle differences.... different CIS...oil cooler etc etc

Wuav, that it interesting. Did not know a 3.1 was made original from the factory. That would need to be in the 1975-77 years I assume.
What is the story behind these rare builds from the factory?
Racing I assume....
Tell us more :-)

scottrx7tt · 02:33 PM

I converted a 3.1 engine to turbo using a carrera intake 9.5:1 compression, a 930 Jpipe Microsquirt ECU, K27-7200. Mine did have carrera heads though. I ran 10 lbs boost and it made 402HP. It was impressive! I definitely recommend a 930 transmission as my original stock transmission spit 2nd gear out in no time. I went in and fixed it, and put another 20k on it with no problems. I sold that car almost 2 years ago. Im sure you can search my username for several threads that i started or commented in that will give you a plethora of information about doing a turbo conversion on the 3.1. As far as i know, my car was 1 of 1 as far as factory 3.1 engines converted to turbo.

scottrx7tt · 02-14-2022, 02:25 PM

JakobM · 02-14-2022, 05:02 PM

Great build and result! thanks for posting - About the case - did porsche make a 3.1 NA case originally?
If so, which NA 911 models had this case?
I have never heard of any 3.1 stamped case from factory
Thanks
Jakob

mikedsilva · 02-14-2022, 07:59 PM

Quote:

Originally Posted by scottrx7tt

I converted a 3.1 engine to turbo using a carrera intake 9.5:1 compression, a 930 Jpipe Microsquirt ECU, K27-7200. Mine did have carrera heads though. I ran 10 lbs boost and it made 402HP. It was impressive! I definitely recommend a 930 transmission as my original stock transmission spit 2nd gear out in no time. I went in and fixed it, and put another 20k on it with no problems. I sold that car almost 2 years ago. Im sure you can search my username for several threads that i started or commented in that will give you a plethora of information about doing a turbo conversion on the 3.1. As far as i know, my car was 1 of 1 as far as factory 3.1 engines converted to turbo.

Hi Scott
do you remember which injectors you ended up using?