Turbocharging a type 4 Options

[stownsen914]

I have heard the conventional wisdom that "you can't turbocharge a type 4 successfully." Is it just difficult, or can it really not be done well? I'm tossing around the crazy idea of turbo'ing a type 4 for PCA club racing, to put in the chassis in my avatar. My 6 in its current configuration is not competitive, so I can put a bunch of money in that, or do something different. I like a challenge, so why wouldn't the following work?

- 1.8 or 2.0 type 4 as a base. I would keep displacement stock or close to it.
- EFI for induction
- Properly sized intercooler and huge oil cooler
- A good aftermarket cooling fan
- Would be dry sumped
- I would work with a knowledgeable builder or shop to build the engine. I am not so familiar with type 4 race modifications, but presumably this would include reinforcing the bottom end, using Carrillo, Pauter, etc. rods
- Obviously the heads would need to be reworked for flow and possibly reliability

If I do the above, could a type 4 be built to withstand 15 psi of boost and make 350 hp reliably?

Scott

[snakemain]

Here's the thread from when this topic came up a couple weeks ago.

http://www.914world.com/bbs2/index.php?sho...20&hl=turbo

It can be done (turbo a type4, not 350 reliable hp...if you want those numbers go Suby or small block)

[Jetsetsurfshop]

I like that you posted this here. Should be some more constructive answers then in the Garage.
It seems that if you built the bottom end and valve train to handle the power it would work. I think I remember reading from a credible post that the heads were the problem. I swear i've seen that someone adds head studs. I don't know if that would help or not? I want to build one too. (IMG:style_emoticons/default/beerchug.gif)

[HAM Inc]

It can be done, but the heads are indeed the weak point, specifically, the combustion chambers in the areas positioned directly above the exhaust ports.

Take a look at the way the port cuts directly beneath a significant area of the chamber. That area is very thin. When exposed to high pressure and high heat it droops into the hollow space that forms the port, anywhere from a few thousanths to half a milimeter in extreme cases. It only takes a few thousanths to blow the jug seal.

This droop is a problem on N.A. engines of modest CR's when temps get high enough in the presense of steady high revs at full throttle. The aluminum is pretty soft at the egt's that peak power demand -1225-1250.

Turbo's like high egt's, and they generate a good deal more cylinder pressure than NA engines.

My suggestion for making it work is to keep the bore as small as possible, the stroke as long as possible and the revs as low as possible. Think really low speed torque.

If I were building a turbo T4 I'd look for a pristine pair of 1.7 Q heads and follow the above blueprint, with a max bore of 91mm.

A fellow on here did a pretty good job with his turbo T4 engine. He followed that blueprint. He didn't cook the heads, but he did hurt it with a mechanical overrev.

[Mueller]

Would the heads benefit from ceramic coatings in this application to help protect the potential soft spot?

[HAM Inc]

Coatings in chambers and ports definitely help. But they're a band-aid.

[Andyrew]

I dont see you making 350hp in a type 4 for any less than a 3.6L conversion. And thats pretty close to that...


I would 100% just run a 3.6 instead.

[HAM Inc]

When the chamber droops it takes the exhaust seat with it. None of our heads have ever suffered a seat failure as a result, but it does lose the valve seal.

You really get a good look at the impact of the droop when you flycut the head and cut the valve seat. This post on our FB site is an excellent example of a head that suffered this issue.

These were new LE200's that were installed on a track car engine and saw very elevated egt's for long, full throttle runs. It developed high leak down around the valves, indicating it lost the valve job. Fortunately the owner stopped running before he blew the head-jug seal, which would have done major damage.

In the pics we're cutting the ex seats. The layout die shows the low side. This one got hot enough to move the intake seats, too. That's some serious warpage!

https://www.facebook.com/HoffmanAutomotiveM...e=3&theater

These were new heads, but only God can make a cylinder head that heat won't hurt!

[stownsen914]

Thanks for the thoughts, guys. I'm giving this some thought because I like a challenge and wondering if it's possible if done correctly. Definitely not looking to do a 3.6 conversion, or a Chevy or Suby conversion. I have a 2.7L 911 race motor in the car now that needs a rebuild, and I'm toying with the idea of a turbo 4 instead of putting the $$$ to make a 911 engine competitive in PCA club racing.

I do understand that a type 4 turbo will not be a cheap venture. I am wondering whether it can be done, if done right.

It sounds like the heads are a limitation. I've heard that there are some fresh castings being done these days. Are those heads designed to address the limitation that HAM mentions above?

[Andyrew]

What are your limitations for your class in PCA racing?

[stownsen914]

Looks like I was writing while HAM was posting. I guess the LE200 heads are the ones I asked about.

[stownsen914]

What are your limitations for your class in PCA racing?

My car currently runs in the PCA Club Racing GT4 class (and where I'd like to stay), which is for highly modified cars using a Porsche tub as a base and a Porsche engine and transmission. The engine case needs to be a Porsche (or in this case VW) part. Pretty much every other part of the engine can be from any manufacturer. The GT classes use a sliding scale for displacement to weight, and different Porsche engines have different hp indexes. The aircooled 911 engine has a 110 hp/L index, 911 turbocharged is 210, type 4 is 90, and type 4 turbo is 150. Currently I run a 2.7L 911 motor in GT4. To remain in this class, I can have a turbo type 4 in the 1.8-2.0L range to run at the car's current weight of about 2100 lbs with me in the car. The type 4 has what may be a favorable index, if I can get 150-200 hp per liter, hence my inquiry.

[Jetsetsurfshop]

Does more boost mean more heat?
Can you run two smaller turbos with less boost?
I don't know much about turbo. Throwing darts here.

I like that Len knows the problem for the turbo idea. How can we solve it?
The ceramic coating idea sounds good to me. What if you took a proactive approach and serviced the heads once a season? Race cars require this kind of service all the time. It's not like your trying to make a daily driver here. But then again, WOT does take its toll.

[HAM Inc]

All engines that see sustained full throttle (max cylinder pressure) are vulnerable to heat related issues from a poor state of tune.

Aircooled engines are by nature more unforgiving to tuning issues than H2O engines since they have a less effective means of dealing with heat.

Among air cooled heads that I've worked with the T4 has the weakest ex port area as it relates to the chamber.

The twin turbo idea is interesting, but turbo's like heat, so the practical impact on the heads will be the same.

The bottom line is that careful temp monitoring is a must. The track LE200's in my FB post were new and had one weekend on them, which IIRC was 6 sessions. Temps were not monitored.

Nickies and coatings will go a long way to managing heat. Limit the revs and run a small bore.

IMO a 4 banger pushing 175hp/liter will be a tedious beast that will steal the fun from your time at the track, and in the shop. You will likely go through a difficult learning curve that will cause you to pull off track early many times to protect the investment from climbing temps, and then thrash on the piping hot beast back in the paddock to try and make the next session. Not a ticket to an enjoyable track outing, unless you like that sort of thing.

When a state of tune issue arises on a long straightaway at full throttle on a NA engine, I know from experience that things go pear shaped very fast. Throw a turbo on there and that will increase exponentially.

For someone with deep pockets, plenty of patience and very accomplished engine tuning skills it could be made to work, just like any other turbo engine.

The T4 wants the same things any high output engine does, ie perfect spark and perfect fuel mixture, and adequate cooling. The biggest challenge with the T4 is that it is an unforgiving platform when it doesn't get all of those things, in concert with each other.

[stownsen914]

Thank you for sharing your thoughts. I guess this must be Len?

The turbo formula is a better known quantity with 911 engines since it's been done so many times for so long. I would think many of the challenges would be the same, and big oil cooler, big intercooler, and sufficient fuel seem to be high on the list (and if you are the Porsche factory, a huge flat cooling fan too). Even without the flat fan, if you get the other stuff right, 250 hp/L is possible. I wonder if some of those who turbo'd type 4 motors didn't take all those steps?

[stownsen914]

Does more boost mean more heat?
Can you run two smaller turbos with less boost?
I don't know much about turbo. Throwing darts here.

I like that Len knows the problem for the turbo idea. How can we solve it?
The ceramic coating idea sounds good to me. What if you took a proactive approach and serviced the heads once a season? Race cars require this kind of service all the time. It's not like your trying to make a daily driver here. But then again, WOT does take its toll.

More boost is definitely more heat and stress on the engine. I understand that the advantage of smaller turbos is faster spool-up when you step on it. I think usually for a smaller motor, like 2.0L, most just use a single turbo.

Maintenance would definitely be frequent on a turbo type 4!

[Cracker]

This may not be popular, and I do not mean to be a "Debbie downer" but I think it is a disaster waiting to happen. Even under the best scenario (as is modern components and technology) turbo motors on the track are very expensive, tougher to drive, plagued with heat issues, and its tough to achieve reliably. The subies blow like its the fourth of July (on the track) - I've seen it "live" many a time. I'd never run one in anger (and they are light years ahead of a T4)! If you move forward, make sure you do so with the expectation that it will be "long road to hoe" (and expensive). Good luck in whatever you choose.

Tony

[HAM Inc]

Thank you for sharing your thoughts. I guess this must be Len?

The turbo formula is a better known quantity with 911 engines since it's been done so many times for so long. I would think many of the challenges would be the same, and big oil cooler, big intercooler, and sufficient fuel seem to be high on the list (and if you are the Porsche factory, a huge flat cooling fan too). Even without the flat fan, if you get the other stuff right, 250 hp/L is possible. I wonder if some of those who turbo'd type 4 motors didn't take all those steps?

Yes, 250hp/L is definitely possible. Like I always say: "Where there's a wallet, there's a way." And: "If you want to push the envelope, better stuff it with cash."

Road racing is hard on engines, and a very unforgiving environment to tuning mistakes. Don't make any tuning mistakes along the way and you'll be doing better than most. They happen. A 10/10th's turbo T4 will not tolerate them well. A N.A. engine can consume itself in less than a lap around Road Atlanta. Ask me how I know.

Like I said before, all engines want the same things for optimum performance and reliability, 911, 914 or 917, etc.

A massive oil cooler will help with heat soak, but do nothing to combat damage from EGT spikes and detonation.

Keep in mind that on a T4 you're funneling that power through a crank with half the main bearing support/cylinder as a 911. The case and crank will have to have a good bit of attention to handle this. I'm not sure (meaning I don't know one way or the other) if the currently available T4 main bearings are up to this.

Also keep in mind when comparing the 911 to the T4 that the 911 heads are much stronger than the T4 with much better cooling characteristics.

IMO the issues that make the T4 not so great a platform for turbo's are pretty well baked into the design. I think that for a short burst AX car the turbo has some serious potential. For a road race car... I see a lot of $$/hp to make it work.

Len Hoffman

[stownsen914]

Thank you again Len and others for sharing your thoughts. A few questions from reviewing other threads and other sources as well:
- I've seen references to a dual-plug option for T4's. I was under the impression that this mod is more for hemispherical combustion chambers. I am curious to know how it helps for a T4.
- What modifications are done to the bottom end of a T4 to make it stronger? Shuffle-pinning is commonly done on 911 motors. Is this done for T4's? Other mods?
- Does anyone do 911-style piston squirters in T4's?
- What options are out there for providing air cooling? I see the RAT sells the DTM setup, and I've seen 911 fan based setups. What works, and what doesn't?
- For 911 turbos, sometimes "Niresist" or interlocking fire rings are used to seal the heads to the cylinders which are considered much more effective than head gaskets. Would this be feasible and desirable for a T4?

Scott

[Mueller]

Seems like there is potentially a small market for some redesigned coast or billet T4 heads.


Key word...small, which is why I guess nobody has taken on such a venture.