Please! Help with my supercharged engine build.
 

Hi all,

So here’s the plan. I’m turning my 1983 3.0 into a supercharged 3.6.

My 83 is actually an 83 1/2. It’s got the updated case and hydraulic chain tensioners. So here’s my plan, any advice would be very appreciated.

I purchased a TPC supercharger with a water-to-air intercooler and I’m switching the engine to Coil on plug MoTec EFI. I found an adapter kit to fit the intake manifold to the heads.

I’m going to have the heads twin plugged and ported. Since I have the 83 1/2, I believe I have the 3.2 head from the 84 Carrera. What size should I have the heads ported out to? I’m going to be using dual racing valve springs with titanium retainers. I’m thinking of stainless steel valves. I’m planning on using ARP bolts for the case and heads.

The big changes I’m making in the engine are, I’m swapping the SC crank for a 74.5mm GT3 crank and I going to be using 100mm slip-fit cylinders and forged pistons. I’m upgrading the oil pump to a 930 or GT3. I have 964 camshafts but I’m open to suggestions. I want to change the car to drive by wire so any suggestions on throttle body size? I’m also using injector dynamics injectors any suggestions on injector size?

I would like to purchase the parts and then have the engine assembled. I would really appreciate any suggestions for my questions. Thank you in advance for any help with my project.

Chris

100mm slip fit cylinders pistons won’t fit your case spigots.

Couple of things I can think of. Even though yours is a late SC it still had CIS and small ports. They will need some port work for best power with forced induction.
While you can get slip fit 100mm cylinders from Mahle and LN you are probably better off to do the machine in cylinders and expand the spigot bore. The slip fit have a very thin wall and do not hold up well in boosted engines (they go out of round) the machine in gain this wall thickness back. If you want to do slip fit 98MM might be a better option.
The stroke on the GT3 crank is 76.4 (not 74.5). You will need custom rods, pistons or both to make all this work. You will also need custom pulleys on the front or have the front of the crank machined (it is longer). There is a lot of custom work needed to make all this work and you might benefit from working with one of the several engine builders on this forum.

john

You need someone that knows what they are doing design this engine for you.....

Regardless of who you get to help, YOU need to set YOUR budget and YOUR performance requirements.

Otherwise you will pay to build "someone else's" engine.

What's with the all caps crap?? Why do you state the obvious??

Who hires an engine designer to design someone else's engine? Do you hire a lawn maintenance person to maintain someone else's lawn?

My point is that someone that has no real idea how a series of complex parts fit together should get some help from someone that knows what they are doing so they don't make one or more mistakes and end up with an engine that can't possibly work. There are not a lot of people out there with supercharger experience on 911 air-cooled engines.

I would fully expect the OP to tell the designer what parts he already has and where he wants to go with the project. Part of that would be the total budget.

Neil has worked for Bernie Ecclestone and with Professor Gordon Murrary winning F1 championships is offering his advice for free on this forum only to be attacked by whom? The OP needs to understand his goals and budget. I will not dismiss Neil’s decades of motorsports experience because he chose all caps.

Neil is correct. Even the best engine builder can't build to the needs of the end user without a clue as to budget, performance goals and aesthetic requirements.
With early 911 project, aesthetics can be incredibly important.
Building a supercharged engine is primarily about building a stellar bottom end. Supercharges can create huge cylinder pressures that challenge connecting rod stability.
Stout bottom end, desired torque curve and desired displacement. There is no single formula so when Neil emphasizes "YOUR" what he's really saying is, build what fits YOUR needs not what random dude on the internet tells you what you need.

How does all this low end power and torque effect cylinder head temps? I would think this would be a concern as the volume of air moving is going to be less than ideal.

Thank you for those kind words.

It doesn't bother me what people say, what matters is when people say kind words in defense. So thank you again.

I am happy to offer an opinion and any advice. I was fortunate years ago to get help unconditionally, so its pay it forward time.

I receive many calls each week from owners and shops asking for my advice and opinions. Often, owners have had an engine built and want a second opinion of what they are doing or what they received.

Often, they were disappointed. The main reason I think, they never understood what they were having built. Education and transparency are so important.

Shops often ask me for a second opinion on what they are about to build. "We would like to offer something different" is the question often asked. Something different usually costs more, but it can be done within a average budget too.

I have seen in recent times the desire of many shops and owners to explore what is available now. All to often its never realized just what can be had.

There is a huge amount of technology that can be had now for these older engines. We have been lucky to stay pretty current with engine technology over the years. We see an opportunity to apply some of this tech to the older engines.

Its not for all as it does cost more. There are many shops that offer great work and great deals with these older engines. They stay in "their lane" do great work and great service. You just have to read some of their posts on here. It takes many.

The shame is, "some" here have a closed mind and think they have the best.

From my perspective they are no where close to the best and have cornered themselves from having the best by their posturing and bravado.

Thanks again to all that said those kind words. They are appreciated.

The challenge in making big horse power numbers in an air-cooled engine is head temp control. There is only so much air flow [heat transfer] you can accomplish through the cylinder and head fins. Oil cooling is paramount but still limited.
Fan speed optimization can increase air flow efficiency but without a horizontal fan, volume is limited as well.
Simply put, horse power and reliability need to find a balance. Compromise is a factor in every engine formula.

Who might "some" be? I am not an engine designer so it can't be me....are you talking about the guy that designs my engines...William Knight? Are you saying that William Knight does not know what he is doing and has "cornered" himself?

. Circling back to something the OP posted:
Newbie911 thought he might have Carrera heads....not likely if the engine still has CIS injection.
The 3.0 heads have a taller intake port flange.

Reclino
Back to your point about head temps. Porsche understood that cylinder head temps would be higher on boosted engines so they made all of the turbo heads using a special aluminum. The heads have casting marks RR350. This identifies the material as Rolls Royse aircraft quality alloy. Only turbo heads were make from this material. Using these RR350 might make sense given the desire to use a supercharger.
There are a few people making cylinder heads for air-cooled Porsche engines so a quick check on their materials might be advantageous. Budget once again is the question.
Here is one source you can try. https://www.xtremecylinderheads.com/

I am aware that the heads are RR350,. My question is and I have asked other times, when people select turbochargers or superchargers with much lower RPM boost onset, I don't think they consider the fact that there is much less cooling air available at these lower RPM,.and thus head temps may be much higher then in any factory configuration. Maybe I am not doing a good job of asking the questions, but I am doing my best to learn from the technical people on this forum.
David
Performance EngiNerding

I think I get your question now. If by they you mean the factory, they did consider fan speed with the turbo engines. They actually ran a larger crank pulleys and small fan pulleys to facilitate increased fan speeds at lower rpm. In fact the fan speed was increased to a point that at high rpm [5500+], the ducted fan became less efficient and the high speed fan tips created a harmonic that was louder as well.
The 2.0 race engines like the 906 ran small small diameter fans with large diameter pulleys and small crank pulleys because they expected the engines to function at high only.
The combination of fan pulleys and crank pulleys was danced around a lot up until Porsche introduced the two speed pulley system in the 964.

Reclino, I agree and you raise some important considerations about air cooling at lower RPM with high boost. There ain't enough.

We look at modern high-boost turbocharged and supercharged engines that produce 200HP Per liter and have no turbo lag wonder why we can't get some of that magic in our olde cars. Of course there are many reasons, but heat is the major one. Porsche limited HP on the air-cooled engines for that reason. Modern engines can get 200HP/liter because they are all liquid-cooled, and furthermore, those engines were designed from the start for boost, instead of having it added onto an existing NA architecture.

Newbie911: Therefore, I recommend not exceeding the figures for HP/liter that Porsche used in the 993 3.6 series turbos. That was 400HP (111 HP/liter), and I will also remind you that it used redesigned heads (with the different alloy Henry mentioned), including the ceramic exhaust port liners and a differently treated crank. In fact, I would stay well below those numbers because you're starting with a 3.2 engine case and heads, AND supercharging produces more boost (and heat) at low RPM than turbocharging. Another thing Porsche did to deal with that extra heat was use a larger oil and scavenge pump in the 930 turbo engines, which flowed more oil through the squirters and the heads and to add capacity for the turbo charger itself. You can look up the part numbers yourself, but IIRC, the squirters in the turbo engines may have been different too. You should follow Porsche's example and use turbo heads, crank, oil pump, and squirters, and open up the restriction in the oil tube in the cam housings a couple numbered drill sizes (and if after running, you still have plenty of oil pressure, you can open that up a little more).

Furthermore, if you stay below 400HP, I will argue that the heads don't need any significant work, because the boost more than takes care of intake flow. I recommend that you have the exhaust ports coated with TBC (thermal barrier coating ceramic) to reduce heat transfer thru the exhaust ports. It's not as good as the cast-in ceramic liners in the 3.6 engines, but it's better than nothing. Use the larger diameter exhaust headers to deal with the additional exhaust flow. Use a cam specifically designed for supercharging too.

When driving it, only plant your foot for short periods (say less than 10 seconds), and keep your RPMs up. That way, you'll give your engine a chance to shed that heat buildup. You may also be aware that on newer cars, Porsche allows the turbo boost to run higher for short periods (seconds), then pulls it back to prevent overheating. You will have to do that with the computer and algorithms between your ears.

Thank you everyone for the info. You've all helped more than you know.

After reading all of your posts and talking to a gentleman from Ed Pink racing engines and a very informative fellow from Patrick Motorsports I've decided to just get a 964 or 993 engine and have it rebuilt.

It seems like it will be easier and less expensive. The supercharger system was designed for these engines anyways. I won't need any machining. The heads should be OK, etc.

I really appreciate your time helping me realize what type of work would go into my Frankenstein engine build.

Once I get an engine, I'll re-post to find out what I can do to make the engine perform better for the supercharger.

Thanks again everyone.

Better decision to start with a 964 or 993, but the same warnings about heat management apply. Best of all would be to start with a 993 turbo engine.

I thought about a turbo engine but I'm just going to get billet heads and have the exhaust ports ceramic-coated. I'll be using the titanium heat shields, dual oil coolers, a transmission oil cooler. The intercooler is water to air. I was thinking about DLC the valve train parts. Maybe ceramic coating a few other parts to help with the heat.

Don't get billet heads....get Xtreme heads which are cast. They are the best!