Help me design a "grassroots" turbo conversion for my SC 3.0L

[SCWDP911]

Greetings to turbo land...

I usually do not post over here, so bear with me on this question if you think it is stupid. I have been looking around on the search a bit, but not found what I am looking for.

The question is this: what would be the ultimate low-buck turbo system for a late model SC 3.0L. Let's think grass-roots here. I have plenty of time to plan this out and gather parts, so scavenging for deals and bargains would be the "plan of the day". I just need to know what to scavenge for!

Keep in mind, I want something that helps my poor US 3.0L to be around 225hp or better (not sure what to expect really). Not looking for a twin-turbo monster. I want something reliable and easy to work on. It has to be something that would require the least amount of tuning as possible. It needs to be something that can be installed DIY.

So there it is. I hope you can help .

[WPOZZZ]

I would look at the 76-77 non-intercooled 3.0 turbo for inspiration.

[911st]

The easyest cheap way is to colect 930 take off parts from up grades and just bolt them up to your motor with a lower boost setting.

For the exhaust. The 930 J pipe bolts up to stock SC heat exchangers, to a wast gate, and to the turbo. You could use a stock take off 930 turbo at first thought a K27-7200 would start on boost earlier. A 930 muffler would bolt up to the turbo.

The only fabrication so far is going to be removing the rear tin and cutting around the turbo intake and discharge.

Often 930 owners upgrade to EFI and they sell off there stock intake manifold , fuel system, and intercooler on the cheap. It would be hard to beat this by trying to adapt your CIS system to be a turbo unless you are just a good fabricator and enjoy doing such.

Your ports are 34mm and the turbo's is 32mm so you could open up the turbo's manifold just a little or just bolt it up as is. You will probably need longer intake studs.

The only thing would would not try to copy is the turbo oiling system train. Check with Ben at M&K mufflers about a drain that plumbs into the bottom of your case.

You will probably need to upgrade your stock fuel pump to a high pressure 044 or just add a second 930 pump in line with your stock pump.

You have about 9.3/1 compression it looks like. You will want to keep your boost under 7.5 lbs or .5 bar max. You will need a different wastegate spring to do this.

As to the spark it would probably be easiest to look for a used MSD and boost retard unit as timing on boost will have to be retarded to make your motor safe.

Such a set up with your stock SC cam should make 260-300hp.

[SCWDP911]

Thanks. Brian (RarlyL8) was telling me a little about the possibility of converting my existing CIS to turbo ready.

I enjoy the fab part on some of this stuff, so it would be nice to understand what all is involved in that modification. Is there a good writeup already on here about what needs to be done?

If I went with a 930 CIS, is it a straight bolt-on swap, or is there a little more to it.

[911st]

Maybe a little more than that.

Don't for get the clutch.

Getting an early/euro fuel system (75-84) with no Lambda function might be easiest unless smog is an issue. Otherwise you will need to get and wire up the Lambda computer. Might just use the SC's.

Not sure how easy it would be to get a .5 bar boost spring. The 3.0 Turbos used a .6 bar but that would probably put you on the edge.

You may have to massage the tail pipe opening.

Also would want to get the tune right. Check the WUR function...

If you start from scratch, there is a lot of adapting of the fuel system that has to be figured out and finding a WUR to work with it might be a challenge, and the metering cone of the SC might not be a great fit.

Any time you have to buy something new to make the conversion the price will start to go up quickly.

At some point it is worth just selling the SC motor and buying a good used 930 motor. This also makes for better resale and a lot more HP potential.

[gsmith660]

Shane honestly there is no way to do this on the cheap. How many miles does your motor have on it? The 3.0 makes a good start to make a 3.2 short stroke with 8.5 to 1 CR and then I recommend the same route I did with the fuel and ignition the EFI and EDIS total cost was roughly 2000 maybe a little more but not much.

[copbait73]

Your compression is high at 9.3:1. A low boost set-up could be done like my 2.4L CIS. Do you have backdated exhaust or the standard heat exchangers?
73.5 911t cis turbo

[SCWDP911]

stock heat exchangers still

[copbait73]

Originally Posted by Shane Van Wey

stock heat exchangers still

These are best. Throw way the cat (or "testpipe") and fabricate from the forward multiple flange rearward to the factory turbo location. Or you could buy this factory pipe. Last one I saw was $150, eBay or Pelican, good shopping maybe half this price. The turbo flanges can be had for about $25.00 in mild steel.

I boosted a 9.3:1 3.0L to 5PSI with no issues. Calculations say 250HP but probably a bit less. Still very tractable with the base C.R. Don't try to bring the boost on early, not needed. Your 5 speed box will give you the gearing 930 guys wish for and the existing clutch will be Ok.

This scenario was just discussed at length. If you want serious power with some measure of reliability you will be duplicating the factory motor. At that stage you are money ahead to start with a used 930 motor.

[SCWDP911]

which scenario was just discussed? the mild one as I am looking at or the killer?

[copbait73]

Originally Posted by Shane Van Wey

which scenario was just discussed? the mild one as I am looking at or the killer?

This is the mild, homegrown, low boost turbo scenario. Roughly 250HP at 5 PSI boost. Your core problem is the fixed C.R. is too high.

[gsmith660]

Hey Shane I have a 930 intake and phenolic spacers that is in decent shape if you decide to go that route. As for the wastegate you are going to have to go the Tial route as the there is no .5 bar spring for the stock wastegate I have one and would have liked to use it but couldn't

[jwasbury]

FWIW, look for posts from Pat Keefe. I believe he has a turbo'ed SC track car. He's a pretty regular poster here on the turbo forum and seems to be a very competent DIYer.

BAE Rev 2.0 Install

[copbait73]

There is an existing turbo that is sized properly for your motor and it already has a wastegate, the mid 80s Buick Grand National Garrett T3. With some shopping you can find one for $100.00. Your mild boost lower HP application will not need the W/G flow of a typical 930 motor. 930 turbo and wastegate can cost $300 (very used) to $2500 (new, higher performance than you need).

You need to be cautious of turbocharger matches based soley on HP because most were for smaller displacement 4 cylinder motors. The compressors are low flowing and your high reving 3.0L will run off the map.

[sjf911]

Originally Posted by copbait73

......You need to be cautious of turbocharger matches based soley on HP because most were for smaller displacement 4 cylinder motors. The compressors are low flowing and your high reving 3.0L will run off the map.

This is why I ultimately went with a K27. You get reasonable compressor efficiency at low boost pressures preserving the appropriate air flow for our engine/horsepower goals.

[copbait73]

Originally Posted by sjf911

This is why I ultimately went with a K27. You get reasonable compressor efficiency at low boost pressures preserving the appropriate air flow for our engine/horsepower goals.

Using the K27 eliminates a lot of special fabrication but at a cost.
Your motor is very impressive in scope, certainly past what I would call a basic grassroots boosted project. Is there a reason why you stayed with the 9.3:1 C.R.?
I like the CAC and W/M injection. What is your water nozzle rating and max pump pressure? What boost level?

[sjf911]

Originally Posted by copbait73

Using the K27 eliminates a lot of special fabrication but at a cost.
Your motor is very impressive in scope, certainly past what I would call a basic grassroots boosted project. Is there a reason why you stayed with the 9.3:1 C.R.?
I like the CAC and W/M injection. What is your water nozzle rating and max pump pressure? What boost level?

I did my EFI conversion at the same time as a top end rebuild with only a vague notion of turbocharging the car at a later time. I actually went with 9.5:1 JE pistons with the 98mm cylinders but the actual compression is less with the twin plug machining and chamfering of the heads. I would love to drop compression further to up boost and corresponding horse power but the rest of the engine, transmission, and suspension are not up to the task, not to mention my marriage.
I am currently running 0.5 bar boost with an in cabin adjustable boost controller. I can't remember the exact water/methanol flow. I am using the Vari-Cool II system by Coolingmist with a single nozzle immediately after the intercooler.

[SCWDP911]

Originally Posted by copbait73

There is an existing turbo that is sized properly for your motor and it already has a wastegate, the mid 80s Buick Grand National Garrett T3. With some shopping you can find one for $100.00. Your mild boost lower HP application will not need the W/G flow of a typical 930 motor. 930 turbo and wastegate can cost $300 (very used) to $2500 (new, higher performance than you need).

You need to be cautious of turbocharger matches based soley on HP because most were for smaller displacement 4 cylinder motors. The compressors are low flowing and your high reving 3.0L will run off the map.

First, I appreciate everyone's comments and help. While I have owned a turbo car in the past, it was all factory and I just drove it! So I am on a big learning curve here. I understand some concepts of the turbocharging, but the devilish detail are where I am trying to pick up my knowledge.

That said, with the grand national turbo, will it work with the 930 J tube?

Also:
I found a guy selling a setup from a 76 930 (his uncle's car). He says his mechanic cheked it out and the turbo and WG are in proper workin order (though not sure how he knows for sure), but who knows. The heat exchanger and J tube look pretty rough in the pictures, but I can pick it up for $150. Not sure it is worth it though. I will post pics and see what you guys think. I know turbos are rebuildable (possibly) and I have access to pretty well equipped shop, so the question is, if I found one such as that, is it worth rebuilding money-wise, or are you going down the wrong path (keeping in mind trying to keep cost at minimum for this project). Is it something that can be done DIY with a decent shop, or are there too many special tools needed? Will pst pics in a few minutes. Snow day here today!

[911st]

Do you have good gas there? 93?

I would think one could buy a full 930 take off with stock turbo and intercooler for about $1000 if one waits and watches.

The stock turbo would come in a little later which is fine and the HP expected is right in its sweet spot. Yes a 7200 or GT would be a bit more efficient.

Could get a .6 bar spring from 3.0T. Many factory WG's boost a bit less than rated.


A .6 bar spring with stock 9.3 CR puts the effective CR at about 11.7. An 8/1 CR at .8 bar has an effective CR of about 11.18. A stock 964/993 is 11.3. Stock 7/1 CR with 1 bar is 11/1. And an 8/1 CR w 1 bar is about 12/1.

Could set the AFR in the high 10's at TQ peak. Lave the cam timing stock. Would be on the edge but if you have 93 gas and or not running on the track should be fun.

I would not do this without an intercooler, fat AFR on boost, and a solid timing strategy.

There are some cheap ways to lower your compression. You might put a 1mm spacer under the cylinders to drop CR to about 8.7. Could trade an early SC owner P&C's to get to 8.5/1. You could machine some of the dome off your pistons. You could have your rods shortened with the small end bushing done in off set.

As to HP, a stock 3.oT euro made about 260hp. With your bigger intake ports, compression, an intercooler, SC cams -- it should do better than this. Thus, still think something like 250-300chp is possible and with better throttle response.

Still need a clutch, a second fuel pump, and an oil cooler. Thus it is still not going to be cheap and watching for a used 3.3 is probably a reasonable alternative.

Just a thought.

However, a set of headers & carbs would be fun to!

The Spec 911 guys are getting up to 235hp with these on a mostly stock 3.0 motor on a well developed car.

Or, a nice SC should sell in the low teens. 930's can be had in the low twenty's...

[RarlyL8]

This is all you need on the exchanger side: