930 heads on a turbo'd SC?

[Lukesportsman]

Would you or could you use 930 heads on an SC for a turbo application? How would it effect the compression ratio, squish area and air flow? Is the alloy improvement worth any hassle in this installation or is there any hp improvements to be expected? Would you JE pistons be able to make an appropriate piston dome design if used with an EFI conversion. CIS design factors are not a factor in this concept. TIA....because I'm looking at some heads currently.

By the way, Wayne, just received your book and I'm very impressed.

Luke

[beepbeep]

Hmm...i'm not teriblly sure but i believe that 930 heads are same as SC ones except that intake ports are smaller.

With other words, it's P&C's that determine compression ratio and fitting 930 heads to your SC engine will affect it's preformance negativly. Porsche decreased intake ports in attempt to boost air velocity and thus torque at lower revs which was problematic in early 930 models due to low C/R and big turbo.

I suggest you to try to keep SC heads. One of first things you do when tuning 930 past turbocharger uppgrades is hotter cams and better flowing heads.

Now let see what experts have to say.

[Lukesportsman]

Goran,

Thanks for the info. The E bay heads weren't very expensive so I thought it was better to ask now than to wish I had in the future. Your one of the guys that I was hoping to answer this question....since obviously you're just a few steps (light years) ahead of me on this. I'll take this info as an answer to pass on the heads.

I couldn't find a great answer amongst my books and I appreciate the knowledgeable on this board always helping us newbies.

Luke

[A Quiet Boom]

Originally posted by beepbeep
Hmm...i'm not teriblly sure but i believe that 930 heads are same as SC ones except that intake ports are smaller.

With other words, it's P&C's that determine compression ratio and fitting 930 heads to your SC engine will affect it's preformance negativly.

P&C's don't entirely control compression ratio, the volume of the heads combustion chamber also plays a role. It's hard to explain without drawing a picture but suffice it to say that if a cyl. head has a smaller cumbustion chamber the compression will go up and the reverse is true as well.

As to the question about JE, when I spoke with them they said they could make just about any compression I wanted.

I agree with beepbeep on keeping the SC heads since it makes no sense to run smaller runners IMO.

[Lukesportsman]

The combustion shape and size was what I was concerned with along with flow. I wasn't sure of differences in swirl or squish areas and didn't want to screw things up rather than improve. CC of the combustion area obviously does effect compression, but I think he was saying that in this instance P did it with the pistons rather than the head/combustion chamber. Much the same combustion size is of differing importance dependent on the size and stroke of an engine.

It sounds that the restriction in flow that Porsche felt necessary to make it more "streetable" in the 930 heads is reason enough with todays turbos to avoid this "upgrade/change" to a NA engine.

[rick conrath]

Dont forget heat. The 930 heads are made of a different alloy to better handle the heat of the Turbo. They are different on several fronts.
Rick
'78 930

[A Quiet Boom]

Originally posted by rick conrath
Dont forget heat. The 930 heads are made of a different alloy to better handle the heat of the Turbo. They are different on several fronts.
Rick
'78 930

I'm aware of that but there are a few things to consider. First there are several turboed SC's on this board that I'm aware of and they don't seem to have heat issues. Second aftermarket oil coolers are better and more reliable than years past. Third todays oil, from what I've read, has better cooling capability than ever before. Fourth there are options like using a 3.6 fan setup to help cool the engine better. And lastly, the factory raced the 930 based engines at much higher HP numbers than stock and they were able to keep heat under control. With all that 's available today I have to believe that a mildly boosted SC shouldn't be much of a problem.

I agree that a 930 engine is probably the best place to start since it was already setup for turbo use but in the case of guys looking for a little more power the costs are too great IMO. Plus todays turbos are much more efficient that the early turbos thus inducing less heat into the intake and less restriction and heat in the exhaust.

I'd love some criticism here since a turboed SC with EFI is in my future plans. It seems to me that with my fabrication skills I can set up a twin turbo system with EFI for just a little more that selling my SC motor and replacing it with a 3.0 turbo (there seems to be a $3000 difference between the two)

[rick conrath]

Whether or not the other SC 's on this board have issues with heat or not remains to be seen. I would call Ollies and some of the other specialty turbo shops, and ask them what problems they have seen in this application.

I am putting together a twin turbo 3.4 right now. The real cost in the motor is not the core, it's in the turbos, intercooler, EFI, exhaust,pistons,cylinders,rods and machine work. Fabrication skills aside, don't discount the earlier engineering skills of the Porsche engineers as demonstrated by the 930.

I think you are underestimating the costs of converting an SC motor to turbo. Your better value lies in taking a 3.3 and spending a little money to make it fly. I know, I sold my SC two years ago for this very reason. The dollar/ hp ratio made little sense. You would be better off starting with a 3.2 as a second option..even though the head issue still remains.

What configuration are you thinking of for your SC...930,935, or 993TT?

Rick
'78 930

[A Quiet Boom]

Originally posted by rick conrath

What configuration are you thinking of for your SC...930,935, or 993TT?

Rick
'78 930

I'm starting from scratch, just about everything will be hand built. I'm looking at T3/T4 hybrid turbos on custom headers into a custom intercooler/intake with megasquirt EFI to start. MSD will be the ignition system incorporating their boost retard controller, 6al box, crank trigger, and programmable timing computer. As for cost, yes I guess I did "underestimate" in the previous post, I didn't include the fact that I already have most of the ignition components as well quite a few of the EFI components. I also have several intercooler core from which I'll build the intake/intercooler setup. Basically I need to build the megasqurt EFI controller, buy the turbos and fabricate the exhaust, crank trigger and intake.

The only thing really holding me up is I had originally planned to use custom low-comp pistons until I found out my SC motor had Alusil cylinders. This is why I might go to the turbo longblock if I can find a good one. Also these are all future plans and are subject to change as I have a dilema What would you do? that needs resolved first. This will give me plenty of time to sort out my engine plan.

[rick conrath]

These projects often take on a life of their own. If you enjoy the journey as much as the destination, then you will have loads of fun. I have changed direction several times through my project, and still have some unknowns( as well as extra parts). One of the hardest tasks is selecting the right exhaust setup. I originally started out with a 935 style twin turbo exhaust that was to exit out the back. After speaking with a number of people, I bit the bullet and went for the 993TT setup since the runner length is so short. There seems to be this weird inverse relationship between the length of the exhaust and the cost.

Don't get me started on EFI systems. A group of us spent six months researching every possible combination with pricing. In the end some of us went to DTA, and some of us went to Motec (myself included). Dont scrimp here...it's the heart of the beast.

As far as your Alusils...check with EBS. They may be able to recoat them with Nikasil. Some people swear by the coated Alusil as a better solution than the Mahle Nikasil.

In the end, I think you will be surprised at the value of the turbo engines. Much of their value lies in durability and ultimate horsepower potential. If it hasn't happened yet...you will be bitten by the HP bug.
Rick
'78 930

[A Quiet Boom]

Thanks Rick,

I was bitten by the HP bug a long time ago. I used to drag race a 600HP small block Ford, then I bought my first 911 and really enjoyed the cornering and stopping power it had but I still missed the awesome acceleration of the old drag car. That lead to a carbed 3.0 replacing the 2.0 the car came with and all that's leading towards the new car and a turbo engine. I know I'll never match the raw acceleration of a dedicated drag car in a street going vehicle but I'd like to at least come close and given the fact that the 911 is so much lighter than my old race car I think I can reach that goal eventually.

You're right the journey is as fun as the destination and there is no better joy than driving something you've put so much effort into. I'll check with EBS about the cylinders since I still think I need to drop down to about 7.5-8.0:1 compression to run the kind of boost I'm thinking about safely.

[beepbeep]

I don't think there is some big issue about 930 heads being made in better material than SC ones.

Actually, I'm quite sure they will work as good if not better than 930 heads. 930 engine is good fundament to start with but you should remember it's unnecessary archaic setup nowadays.

It has strangled intake ports, C/R that is unnecessary low, piss-poor flowing intake, mild cams (due to CIS) and bad turbo.

Best engine to begin with would be Carrera 3.2 engine. it has already turbo crank, good case, free-flowing heads,good plenum with fuel rails etc.

I would stear clear from hybrid T3/T4 turbos. It will be way too big for your 3.0L engine. See earlier thread on 911 tech forum and Natchamps problems with K26 hybrids. It's quasi-typical for TT installations to chose too big turbos...temember, you'll have two of them!

Frankly, i dislike "customized" hybrid designs to begin with. Problem is that turbo shops would like to sell their expensive "customized" stuff to punters but many times thet actually don't know what they are doing. Remember that when there are no leaks all air that goes trough compressor will alsogo trough turbine latar on. If size relation between turbine and compressor size is altered too much, you will get "capped" range on the turbo where it cannot boost more than certain value, it just blows hot air.

I suggest looking for a pair of K16's. Also,
8:1 C/R would boost your off-boost low range torque too.

[rick conrath]

The factory didn't make the heads of a 930 with different material for grins. You don't believe me, ask the experts. This isn't my opinion...it's fact.
Rick
'78 930

[ChrisBennet]

Originally posted by A Quiet Boom
Fourth there are options like using a 3.6 fan setup to help cool the engine better.

The stock 3.6 fan flows less air I believe. It is quieter though.
-Chris

[A Quiet Boom]

Originally posted by ChrisBennet
The stock 3.6 fan flows less air I believe. It is quieter though.
-Chris

I made that statement on an assumption that the factory changed the fan design to help cool the higher output 3.6. I don't know if it flows more or less, it was just an idea.

[A Quiet Boom]

Originally posted by beepbeep
I don't think there is some big issue about 930 heads being made in better material than SC ones.

Actually, I'm quite sure they will work as good if not better than 930 heads. 930 engine is good fundament to start with but you should remember it's unnecessary archaic setup nowadays.

It has strangled intake ports, C/R that is unnecessary low, piss-poor flowing intake, mild cams (due to CIS) and bad turbo.

Best engine to begin with would be Carrera 3.2 engine. it has already turbo crank, good case, free-flowing heads,good plenum with fuel rails etc.

I would stear clear from hybrid T3/T4 turbos. It will be way too big for your 3.0L engine. See earlier thread on 911 tech forum and Natchamps problems with K26 hybrids. It's quasi-typical for TT installations to chose too big turbos...temember, you'll have two of them!

Frankly, i dislike "customized" hybrid designs to begin with. Problem is that turbo shops would like to sell their expensive "customized" stuff to punters but many times thet actually don't know what they are doing. Remember that when there are no leaks all air that goes trough compressor will alsogo trough turbine latar on. If size relation between turbine and compressor size is altered too much, you will get "capped" range on the turbo where it cannot boost more than certain value, it just blows hot air.

I suggest looking for a pair of K16's. Also,
8:1 C/R would boost your off-boost low range torque too.

Ok, I already have a 3.0 so that's why I'm planning on it as a starting point. Also I haven't really researched the turbos yet so the T3/T4 was just a consideration, of course I'll size the turbos for the desired output and rpm range. As for the intake setup of the 3.2, it's irrelevant in my plan. Basically I want to fabricated an aftercooler type setup from two intercooler cores with an intake plenum in the middle for the throttle and end tank plenums to feet the runners to the cylinders. I can machine and weld all this myself, I just need to figure out the thermal expansion issue.

I admit I have a lot of bugs to work out of the plan but like I stated earlier I have plenty of time to get there since I haven't even started on the chassis yet.

[rick conrath]

I would buy a 3.2 intake from e-bay and use that as a starting point, rather than trying to fabricate something. You will have to open up your heads to match the ports...but that's a much smaller deal than the fabrication involved in making the intercoolers and associated piping. The 3.2 manifold is a tested design. Try some hybrid K-16's ...or better yet, try them as is. If you are not happy, then have them worked over with bigger wheels, etc.
Again I re-iterate. Don't spend any money on your heads until you really understand where you are headed. You can take a set of turbo heads and make them flow...you can't take a set of 3.0 or 3.2's and change the thermal properties of their metal. Check with Imagine auto, Ollies, ...etc. to confirm what I am saying here. You can go with the 3.2 heads...but I wouldn't take the chance, especially since it's not really going to be any cheaper going that route.

Rick
'78 930

[A Quiet Boom]

I think the logical first set is to get the system running at low boost say 6-8 psi on the current longblock and then make decisions about heads and compression. If it turns out I need both it only makes sense to get a turbo long block and do a little work to it, like porting the heads and maybe bumping the compression a point to 8.0:1 then maybe cams. The idea at first is to get a running engine without modifying the long block so that I could sell it if need be. I'm not concerned with fabrication, that's the fun part for me, I love designing, machining and welding.

[rick conrath]

I understand. I tig welder is now on my wish list.
Rick
'78 930

[A Quiet Boom]

Originally posted by rick conrath
I understand. I tig welder is now on my wish list.
Rick
'78 930

Yup! one of the best toys to have. Fortunately for me I get to use the tools and shop at work on the weekends and evening for my car projects. I recently fabricated an intake plenum for my brother-in-law's car, he owns the business. We're in the process of putting a Ford 2.3L turbo from a Thunderbird into his '73 TVR 2500M. He's running a T3/T4 which is were I got the idea for the turbos but I realize they would be too big. I'm also fabricating his intercooler from a core he purchased, it will be totally custom for this car. The interooler/intake for my car will look something like this (excuse the poor graphics skills) The gray areas are the intercooler cores, the end tanks will feed the runners and the center plenum will hve the TB connected to it.