Help with 911SC turbo design

[sigchuck]

Hi guys, I first want to thank everyone for documenting some extraordinary builds over the years. The information has been invaluable. I’ve read countless threads, the old BAE turbo manual, and Maximum Boost by Bell.

I have a stock (recently rebuilt to factory specs/9.3 CR) 1983 911SC. The horsepower bug is strong, and I’m considering adding a turbocharger, likely based in whole or large part on the BAE kit (thank you to Chappy for sending me a manual several months ago).

I would like to run without an intercooler/methanol injection, as I like the tail-less lid that I currently have. I know this will seriously limit the boost I can run, and I think makes it even more important to address timing and fuel enrichment issues that were not addressed all that well by BAE.

I would really appreciate any help with the following, very general questions that will hopefully help me decide whether it's feasible for me:

1. Will an adjustable (Lesak) or factory 930 WUR solve the enrichment under boost problem with the factory 911SC CIS?

2. Will fabspeed or rarlyl8 headers bolt up to my 911SC heads? Based off several threads, it appears the exhaust port sizes are the same on 78+ 930s and 911SCs, but a call to Fabspeed’s “tech” line indicated they won’t work. I use quotes around tech as they didn’t seem to know a lot outside of what the website told them.

3. Will engine longevity/reliability be seriously affected running .5 bar of boost without an intercooler? I love driving the car and it’s generally my daily if the weather is nice (targa top makes for a wet commute in the rain).

4. Does the MSD boost controller require manual input (i.e., knob turning) throughout the drive, or is it a “set it once and forget it” type device? If the former, is there a better way to permanently address ignition retard under boost?

5. Any thoughts as to turbo brand/specs for a low boost application like this?

Thanks so much for your help with this guys! A turbo is definitely an exciting prospect!

[Jeff NJ]

I have a 930, and have not turbo'd a non-turbo car, but I can answer a few things here:

1. A 930 WUR made adjustable by Leask will allow you to set the enrichment threshold and the boost enrichment pressure. Neither can be done with an SC WUR since there is no boost and they only enrich on the absence of vacuum. I doubt a factory 930 WUR would be set at the right specs for a turbo SC, so an adjustable one would be my choice.

2. I would call Brian at rarlyl8 directly and discuss.

3. Detonation is what kills these motors prematurely, so it is all about avoiding that. As long as you do, I don't see why your motor life would be shortened. An IC helps, but there are myriad ways to address that, including knock sensors, timing maps, higher octane, proper AFR, etc.

4. I have an MBC and its sole purpose is to limit the max boost. It is not something you touch while driving and it has nothing to do with any levels of boost throughout the rev range other than max boost. You would set it at 0.5 bar and forget it. The "dial of death" that you have heard about simply adjusts the max boost to increase max HP at WOT. Not a good idea for a street car or nearly any car that doesn't have a lot of work done and other safeguards to help avoid blowing the motor.

[EPorsche]

Subscribed

[RarlyL8]

Sounds like you've schooled yourself on turbo kits and how things work! The same systems and approach when transplanting a 930 engine into a 911 will apply for turbocharging your 3.0L SC engine. You've got to deal with oil to the turbo, extra fueling and systems affected by increased horsepower.
1. Yes an adjustable 930 WUR is helpful to dial in the fuel curve and for enrichment on boost. However, you will run out of fuel using the OEM SC fuel distributor and pump if adding any appreciable horsepower. We can modify the fuel distributor for more flow. The OEM pump should be changed to a -044 unit if you plan to keep just one pump.
2. Yes our headers will bolt right on to SC heads. Depending on what oil lines you have they may need to be changed. The headers will add a bunch of power and add torque to work with your SC cams allowing you to use lower boost to achieve the same results. If on a budget you can use your OEM exchangers and add a 930 J-pipe.
3. Longevity is only affected if detonation becomes a problem. Your driving style will have a lot of influence on this as well. Street cars typically aren't on boost very often or for very long periods. I do know folks (you know who you are, ha!) who drive the stew out of their turbos which would cause high intake temperatures without an intercooler, which leads to detonation.
4. MSD has a version that retards on boost. Nice option or you can just set your OEM SC distributor to 29° @ 4000rpm which should be conservative enough for 0.5bar boost at 9.3 C/R. You'll need to adjust the timing once you get some feedback driving the car.
5. I'd use a small turbo like a GT30 or similar. You'll need something that operates well at low boost levels.
Don't forget the turbo oiling, scavenging and a sport clutch.

[spuggy]

Originally Posted by sigchuck

considering adding a turbocharger, likely based in whole or large part on the BAE kit (thank you to Chappy for sending me a manual several months ago).

You might be interested in the tailless/non-intercooled kit in the classifieds here - guy took it off his 2.7.

No affiliation, just looked like a great starting point with all new(ish) parts that seems to fit your application almost to a 'T'..

Originally Posted by sigchuck

is there a better way to permanently address ignition retard under boost?

I vote the J & S Safeguard; only retards ignition if you need to (because actual detonation).

[flightlead404]

Originally Posted by sigchuck

Hi guys, I first want to thank everyone for documenting some extraordinary builds over the years. The information has been invaluable. I’ve read countless threads, the old BAE turbo manual, and Maximum Boost by Bell.

I have a stock (recently rebuilt to factory specs/9.3 CR) 1983 911SC. The horsepower bug is strong, and I’m considering adding a turbocharger, likely based in whole or large part on the BAE kit (thank you to Chappy for sending me a manual several months ago).

I would like to run without an intercooler/methanol injection, as I like the tail-less lid that I currently have. I know this will seriously limit the boost I can run, and I think makes it even more important to address timing and fuel enrichment issues that were not addressed all that well by BAE.

I would really appreciate any help with the following, very general questions that will hopefully help me decide whether it's feasible for me:

1. Will an adjustable (Lesak) or factory 930 WUR solve the enrichment under boost problem with the factory 911SC CIS?

2. Will fabspeed or rarlyl8 headers bolt up to my 911SC heads? Based off several threads, it appears the exhaust port sizes are the same on 78+ 930s and 911SCs, but a call to Fabspeed’s “tech” line indicated they won’t work. I use quotes around tech as they didn’t seem to know a lot outside of what the website told them.

3. Will engine longevity/reliability be seriously affected running .5 bar of boost without an intercooler? I love driving the car and it’s generally my daily if the weather is nice (targa top makes for a wet commute in the rain).

4. Does the MSD boost controller require manual input (i.e., knob turning) throughout the drive, or is it a “set it once and forget it” type device? If the former, is there a better way to permanently address ignition retard under boost?

5. Any thoughts as to turbo brand/specs for a low boost application like this?

Thanks so much for your help with this guys! A turbo is definitely an exciting prospect!

I had a similar set of considerations with my modified 930. Since I have CIS with lambda I elected to go with a FrankenCIS implementation, replaced the WUR with an eWUR, and running ignition and electronic boost control all from the MS. I'm not on the road yet but have good confidence it will work.

afaiak the leask style adjustable wur, coupled with rpm or vaccum based pierburg switches for mixture adjustment is an old rube goldberg setup that is unnecessary and suboptimal given the technology available today.

[lite75]

I vote the J & S Safeguard; only retards ignition if you need to (because actual detonation).

The J&S Intercepter can be programmed to pull timing under boost as well as using the knock sensor. Good option for the ignition side of your project.

[gavinc69]

I found the biggest problem was fuel supply.
The Bosch CIS fuel head could just not supply enough fuel. I even tried the Dkubus digital WUR setup and I still could not flow enough fuel.
I ended up going EFI, that works.

If I had to do it again I would just go straight to EFI.

Check out my thread :

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/711757-turbo-conversion-3-0-sc-winter-project.html

[flightlead404]

Originally Posted by lite75

The J&S Intercepter can be programmed to pull timing under boost as well as using the knock sensor. Good option for the ignition side of your project.

If you go the frankencis route you can use the much cheaper, although less feature rich, knocksense ms. Engine knock detection and indication for all vehicles

The MS will do all the timing adjustments and so forth for you.

[sigchuck]

Thank you all for the great information.

With respect to fuel delivery, I actually have my tank out right now for repairs and was going to go ahead and replace the fuel pump. Is it okay to go to an -044 pump now with stock, NA CIS, or would this cause potential over-pressure issues?

I also do a fair amount of highway driving, and even in 5th, I find myself between 3500 and 4000 RPMs. Depending on turbo, would this have the potential to put me on boost for an extended period?

Lastly, would a K27-7200 be a good potential candidate for a low-boost 3.0 like this? I may have the opportunity to pick up a good used unit from a 964 for a reasonable price, and would like to know that it will have some value to someone if I choose to not pursue this project.

Thanks again guys!

['76 911S 3.0]

Originally Posted by sigchuck

Thank you all for the great information.

With respect to fuel delivery, I actually have my tank out right now for repairs and was going to go ahead and replace the fuel pump. Is it okay to go to an -044 pump now with stock, NA CIS, or would this cause potential over-pressure issues?

I also do a fair amount of highway driving, and even in 5th, I find myself between 3500 and 4000 RPMs. Depending on turbo, would this have the potential to put me on boost for an extended period?

Lastly, would a K27-7200 be a good potential candidate for a low-boost 3.0 like this? I may have the opportunity to pick up a good used unit from a 964 for a reasonable price, and would like to know that it will have some value to someone if I choose to not pursue this project.

Thanks again guys!

I ran an -044 with factory CIS without issues.

[spuggy]

Originally Posted by sigchuck

Is it okay to go to an -044 pump now with stock, NA CIS, or would this cause potential over-pressure issues?

Pump doesn't determine pressure, the regulator does. From Bosch Motorsport:

Modern electric fuel pumps are “Positive Displacement” type pumps, this means that the pump cannot produce pressure unless it is acting upon a restriction. The only restriction in the system should be the fuel pressure regulator. The regulator controls the system pressure; the pressure ability or flow volume capacity of the fuel pump will not alter the system pressure.

Originally Posted by sigchuck

I also do a fair amount of highway driving, and even in 5th, I find myself between 3500 and 4000 RPMs. Depending on turbo, would this have the potential to put me on boost for an extended period?

You'd like a taller 5th a lot better, I'm sure.

It won't make boost unless there's load; doesn't make boost purely because the RPMs are up there.

Which is why, when you're cruising at a constant speed/throttle opening on the highway and you start to climb a hill, the car will speed up - because it started to make boost due to the extra load. Kind of odd the first time it happens...

Originally Posted by sigchuck

Lastly, would a K27-7200 be a good potential candidate for a low-boost 3.0 like this? I may have the opportunity to pick up a good used unit from a 964 for a reasonable price, and would like to know that it will have some value to someone if I choose to not pursue this project.

The K27-7200 would be an upgrade for a 930 with the original 3DLZ. For your purposes, think you would get the best results from a turbo selected to suit the application; e.g. small/fast-spooling, doesn't need to flow massive amounts of air.

The only upside of the 7200 would be that you could sell it to someone who hadn't figured out that there were much better K27s 20 years ago...

[clutch-monkey]

Originally Posted by sigchuck

I would like to run without an intercooler/methanol injection, as I like the tail-less lid that I currently have. I know this will seriously limit the boost I can run, and I think makes it even more important to address timing and fuel enrichment issues that were not addressed all that well by BAE.

you can still run an intercooler, maybe a small one with water/methanol injection as well, to give you a buffer?
or something like this.

[flat6pilot]

I used a small intercooler on mine, but not really sure how effective it is. I can read intake temps thru my Megasquirt system but I don't know what is good and what is HOT.

Here's a parts list:
Another 911sc Turbo Conversion

And another link with some pics showing the intercooler tucked under the lid:
Another 911sc Turbo Conversion

Also, you had a question about the MSD retard box on your 1st post: Yes, it's set it and forget it.

[gavinc69]

I had the FrankenCIS and maxed out the fuel MAP (255 per cell) but the Bosch fuel distributor could not flow enough fuel.

Yes the K27-7200 is fine. I started woth a 3LDZ and then put a K27-7200 on.

I really would recommend going EFI first, get that running well and then add a turbo.

I gradually upgraded and modified my setup to over come problems that I kept finding and limitations of factory parts on the car. I learnt alot but my advice having done it myself would be take the easy route, EFI then turbo.

Even if you go for the Blitz racing kit its a good start https://www.bitzracing.com/ and will get you up and running.

[iamchappy]

When I ran a turbo in my 79 sc 3.0 cis engine with stock wur, I kept It pretty simple It worked very well at 9lbs of boost no intercooler. I added a 7th injector that was plumbed in just before the throttle body, I used an sc cold start injector for this with a hobs style pressure switch set at 5lbs. My afrs were plenty rich on boost. Not the perfect setup for fine tuners but it worked well and ran safely. The slippery slope finnally caught up with me and ended up building my current engine with 930 cis Ruf intake and fuel head. I kept the 7th injector but it only fires when on boost over 6,000 rpms.

[sigchuck]

Guys, thanks for all the replies and especially to those that have helped via email. In considering this project, I’m now leaning towards using more factory 930 components.

I was thinking of the following

- 78/79 factory 930 intake/fuel management system (sans rear pump in lieu of -044 pump up front);
- Injector blocks ported slightly to match my small port SC heads (34mm intake port on heads vs 32mm port on 930 intake, I think);
- Tial 46mm WG with .5 bar spring;
- Elimination of factory intercooler with routing of turbo discharge pipe directly to TB;
- Gravity drain on 3dlz turbo

Assuming there are no glaring problems, can you let me know where you think you might see issues? I would like to continue to drive the car fairly regularly, so anything related to cold start valve, TTS, etc.?

Could I eliminate the factory bypass duct in favor of an aftermarket BOV/bypass back to the turbo intake pipe? I have a very limited understanding of the factory bypass system, but it looks like there are a couple hoses and vacuum pods present. Are those solely related to the bypass system, or would I affect other parts of the CIS?

As always, thanks for your help and the wealth of knowledge.

[iamchappy]

These are the left over parts I used with the bae kit, I had a tial bov mount welded to a SS elbow that replaced the original bae one. I may run across some more pieces stashed where I've not looked. One of the elbows has been cut down and may not work for you. You might be better off getting new aluminum piping and fabricating your own, plus it's lighter.

[sigchuck]

Originally Posted by sigchuck

Guys, thanks for all the replies and especially to those that have helped via email. In considering this project, I’m now leaning towards using more factory 930 components.

I was thinking of the following

- 78/79 factory 930 intake/fuel management system (sans rear pump in lieu of -044 pump up front);
- Injector blocks ported slightly to match my small port SC heads (34mm intake port on heads vs 32mm port on 930 intake, I think);
- Tial 46mm WG with .5 bar spring;
- Elimination of factory intercooler with routing of turbo discharge pipe directly to TB;
- Gravity drain on 3dlz turbo

Assuming there are no glaring problems, can you let me know where you think you might see issues? I would like to continue to drive the car fairly regularly, so anything related to cold start valve, TTS, etc.?

Could I eliminate the factory bypass duct in favor of an aftermarket BOV/bypass back to the turbo intake pipe? I have a very limited understanding of the factory bypass system, but it looks like there are a couple hoses and vacuum pods present. Are those solely related to the bypass system, or would I affect other parts of the CIS?

As always, thanks for your help and the wealth of knowledge.

And an additional follow-up question - Assuming the 930 intake/fuel system will work on the SC, will it noticeably (negatively) affect off-boost performance?

Thanks!

[jpnovak]

Honestly, I would not even bother with CIS for this application. Just go EFI and move on. Will be a much more simple install. IF you want the 930 CIS pancake manifold then buy TurboKraft injector blocks.

I see a frustrating road ahead if you try to mix and match various systems without a complete understanding of how they all interact.