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

[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?

[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