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

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)

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.

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.

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

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

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.

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!

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?

What are your limitations for your class in PCA racing?

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

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.

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.

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.

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?

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!

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

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

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

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.

Scott, what limits do you have on engine controls? I'm just wondering if you could extend engine life with some fancier fuel/timing/boost control strategies based on EGTs, knock, etc.

I imagine you have to decide if you heart is into the project or the driving.

How about water mist cooling like some if the 911 guys have done?

I think is called Coleman water cooling or something like that. Good for 10 to 15 minutes?

No limits, at least not in the rulebook I don't have a bottomless wallet, but I would plan to use a quality engine management system if I do this project.




I thought of this too. I believe it has been called the Rubbermaid solution for the brand name of the container you put the water in . Popularized by a 914 guy, no less - Grady Clay, RIP. He used it on 911 motors at the track, and I assume on his 914/6 racecar.




Yes, you've got me on that one. If I didn't like a challenge, I would not still be racing the 914. I'd have bought a spec Boxster!

Burning alcohol would keep head temps down. Add power too. Is it legal?

I've wanted to do this for a while on my 911 motor, and would make sense to me for a T4 turbo as well. Unfortunately, not legal at the moment for PCA Club Racing. I looked just yesterday to make this suggestion again, but it seems the period for submitting suggestions for 2017 rules closed in August. I would suggest E85 actually, which gives a more visible flame than straight alky when on fire. I understand that the invisibility of alcohol fires is why some has reservations about its use. Maybe next year ...

These days, anyone racing a turbo pretty much has moved to E85. Makes a ton of sense to me.

FAT Performance does install 911 oil piston squirters in Type 4 cases, check with them.
I read somewhere that when using twin-plug ignition, there are more gains in power for smaller bores than with larger bores. It might have been written in the B Anderson 911 Handbook, or maybe in Up-Fixin...going by memory on this...
I bought ARP thru bolts and ARP head studs. Jake recommends the head bolt torque be 24lbs, no mention of the case thru bolts. Gene Berg raised the case torque on Type 1s by spot-facing all the bolt holes and using thicker, hardened washers. An old article about engine builder John Zeitler increased thru bolt torque to 40lbs, perimeters 35lbs.

https://www.youtube.com/watch?v=6r1Unv9L39k


There was more detail about this on Jake's Forum. I think the owner said he was getting approx. 300 hp. Sounds sweet.

You're right about B. Anderson and the twin plug, but I think that was for 911 engines. The dual plugs make a lot of sense on the 911 due to the hemispherical combustion chamber shape, and even more so on high compression 911 motors, since high-domed pistons make the situation even worse.

I thought that dual plug didn't have the same advantages for type 4's since they have flatter combustion chambers and pistons (and like many other engine types that also don't get much benefit from dual plugs). But maybe I'm wrong on that?

Twin spark for:

1. High compression
2. Big bore

As for the twin plugs it's the other way around; the extra plug benefits larger bores more than smaller bores.

On 911's the second plug is advantageous because the piston dome interferes with the flame front. Putting a second plug on the opposite side of the chamber cuts down on detonation. This is a typical issue with true hemi chambers.

A second plug on a T4 is a royal PITA to deal with. Gets pretty crowded and hot on the bottom of the engine. The plug wires routing is a challenge.

All of those challenges can be (and have been) overcome, but with a small bore (90-91mm) wedge chamber using a flat top or even dished piston, the second plug will not be needed.

My suggestion for minimizing heat gain from the turbo is to run a larger turbo and run low boost.

I have a pretty big turbo in my audi 1.8L engine and on 10psi it will make about 275hp on good fuel and lots of timing. I run an air to water intercooler and its a pretty solid setup.

You can easily adjust your power level for the track your on by adjusting the boost. My setup is a bit extreme and its a newer motor so its always going to have more potential, but on race gas and high boost (30ish) it'll make over 500hp very easily...

You can also program in an overboost function that will increase your boost for a couple seconds. Many electronic boost controllers have this option. Great little secret weapon for a track car.

I would think forcing more into the cylinders via a turbo would be increasing the cylinder pressure just like increasing the compression.

Yup. I was just correcting his post (Len did a better job).


I'm missing the correlation between big turbo and low boost? I get low boost, but you presented it as if those two work in tandem. My first two thoughts on turbo size relate to 1. what rpm the turbo kicks in and 2. what rpm the turbo starts impeding exhaust flow. But I agree with all your benefits of running low boost.

Most new production cars with turbos are running higher compression, small turbos and lower boost. Giving good off-boost performance and a nice little kick when the turbo spools.

I'm thinking I'd need to run at least 15 psi for the hp I'd be looking to make (at least 350). At that boost, heat from the turbo is certainly something I'd have to deal with. I would run a large intercooler, and hang it in clean air to cool it. My 914 has very wide bodywork, so I would be able to fit it on the fender well area in front of the rear tire (even extending forward to the door if needed, which also sits much wider on my car) with a large NACA duct or similar feeding incoming air.

I read his comment to mean that a smaller turbo, when pushed hard, tends to generate more heat than a larger turbo. I would be building this for track use only, so the logic makes sense to me.

PSI is relative to turbo size and plumbing. A small turbo running 15psi on a 2L engine would make say 175hp, medium say 250-275, and a large say 350-375 simply as examples... But the tradeoff there is WHERE they make the power. the 175HP engine might make say 200lbs of torque from 1.5k-5k rpms making it a fantastic responding engine. The 250-275 turbo might make power from 3-6k making it a great street/track engine using all of a typical rev range. the 350-375 turbo might make power from 4.5-7.5k meaning it would need an engine built to rev higher, and would have a very noticeable boost lag.

Its all relative in that remark. Also certain turbo's make much more power when you get above a certain PSI range. For example my big turbo is just starting to wake up around 25psi and is comfortable up to about 35psi. Whereas a stock style turbo wont make much more than 20psi and will fall on its face as the RPM's increase.

There is a LOT of turbo tech out there. Heat and detonation will be your enemy. Adjustable timing, a properly sized turbo, race gas and methanol injection will be your hero's. Your going to need a tuner that REALLY knows their stuff.

http://shoptalkforums.com/viewtopic.php?f=3&t=131253

An interesting build thread, a couple different versions and tests done

I would think you'd be shooting for the most efficient spot on the turbine and compressor maps to keep heat generation down and pressure drop across the turbine relatively low. This likely equates to a larger turbo than would generally be selected since low rev drive-ability isn't really a concern for a track car.

Good results from a GT3076. Seems to me those are wheel numbers, which again is pretty impressive for a T4! You could find similar numbers for the Audi 1.8T guys.

Whats equally impressive is the torque curve. There is no boost spike, its straight linear. I cant tell from that first dyno sheet where the turbo makes max spool but Im going to guess its around 4k

Just for reference the GT3076 is about the same size turbo as whats on my Audi 1.8T for those following my setup, and those are numbers I was expecting to hit myself on a much more advanced motor.

Correct

Been following this thread intently and want to get back to the heads.
Why do companies like Scat and Pauter have there own performance castings for type 1 and not for us? Isn't there enough of us interested to get some of that love our way?
I dont know this, but does the bug and bus crew like using our engines to make more power? It just seams to me that we have enough customers to make some performance castings, right?

If I was building a turbo setup for a track car I would do it like this.
Which tracks am I driving and whats the lowest revs I will use on track with the current gear /tire ratios. Lowest RPM will determine usable turbo sizes depending on how much you value boost out of those lowest speed corners.

Take this data to the person thats going to tune the car and get their view on turbo size etc. Critical to use someone with ALOT of experience of different setups. A turbo doesnt care if its boosting an aircooled engine or a watercooled engine.

I for one would choose a broad rpm range with boost over peak hp.
An easy to drive car will yield the most consistant laptimes and let you focus on driving.

Not sure it helps any but hopefully you've thought of this already.

What about using a supercharger for the forced induction, vice turbos? From reading thru this thread, it seems that you would have the resources to make an SC engine work just as well as a turbo one? I don't know a whole lot about either method of forced induction, but I would think you wouldn't have as much of a heat issue with an SC as you would with a turbo, and the plumbing wouldn't be anywhere near as complicated?

I'm talking about the accessory-belt driven style SC units like those from Paxton or Magnuson, not the Roots-style ones. As long as there's a belt on the car, like for the alternator, one should be able to fab up a belt-drive system to power an SC.

Just thought I'd chime in with another option...

Superchargers simply can not make the power of a turbo. However there are many people that are using superchargers to spool the turbo similar to how in the old days people would use nitrous to spool the superchargers.

What some have found is that the supercharger becomes a parasite at higher RPM's to the turbo and they put a flapper that dumps the supercharger pressure once the turbo is outboosting the supercharger. Thats just one way of doing it.


Another is twin charging which is simply running both in the same intake track, which I think is the most commonly found method. If sized correctly it can be very potent. I have been considering it for my setup but I simply dont think I can use the power that that setup will make on my engine... I think I prefer to rev my engine out vs the instant torque. We'll see.

Another common method is multiple turbo's. The theory is that its better for spool, and gives you a similar top end as a medium size turbo with two small turbos. But in practice you will find that most high end tuners go to a single turbo application as its far more simple and has just as much if not more power across the board. I believe its so common among manufacturers today because it is more compact than a large turbo.

Finally there is compound turbos. Not something I would recommend in a racing application but BOY is there some power potential there. Unlike twin turbo's compound turbos have a small turbo that feeds directly into a large turbo, essentially spooling it quickly. The issue with a compound turbo is that you overspool the small turbo. This is very similar in practice to the twin charging setup as you have something that gives power down low as well as spooling an incredibly large turbo.



If hes only looking to make 350hp from a turbo 2.0L that wont be that difficult. As shown by Mike a nicely built T4 can easily do it on pump gas within a safe boost range. Decrease the turbo size a little bit, run race gas and lots of timing and you have a very nice setup for the track. For a track car it'll provide plenty of power in the lower register of his gear infact he might find that the torque it produces is going to be problematic for his transmission..

O.P., can you convert to a T1 engine for your class?

If so find an aluminum Auto Linea case and build from that. There are plenty of new T1 head options out there that are stronger than T4 heads.

That's a nice build thread from the shoptalk forum. I haven't finished reading it yet, but definitely will.

As for what I can do for my build, I don't want to limit myself to 350 hp if more is reasonably available . For trans, I'd switch to a 915 and use custom gearing to get the RPM range where I want.

^ditto... even MOFOCO has brand new cast in the USA heads starting in the $300 each range. ( doing some reading I guess they had some iffy quality issues years ago but current heads supposed to be decent for street motors, not designed for race car applications as is)

I think the solution is water cooled heads like the 934(935?) race cars.

So your basically looking at about 15-20k engine+trans. Right?





I dont think he can run a T1 at PCA events. It needs to be a "Porsche" motor and trans.