TurboTim

Jack,

Pull out your credit card! Typically a low boost forced induction system is good for 40-50% more power at the wheels.

Drew,

Yes we need a shark for prototyping and desiging the system. I would like to see a few more people commit to this sort of project though. Not financially but at least some sort of written statement gauranteeing the purchase of said system if we can deliver what we promise. We have already been through this sort of project with the supercharger systems we developed for the 944, 944S2 and 968 and we have yet to recoup our R&D costs on any of these vehicles, so I am a little skeptical about doing anything for discontinued Porsches these days.

As far as the system goes.........We can start with an adaptor flange that will allow a garret turbo with internal wastegate to be mounted onto the the 928 header. We can also build a custom stainless header with external Tial wastegate as an upgrade.From there the downpipes can be rerouted to the stock cats and exhaust. We can build a test pipe as an added option. The discharges of the turbos will be routed underneath the car with oval tubing (so it does not interfere with ground clearance) to the Spearco intercooler(which will be mounted in front of the radiator). Out of the intercooler will be tubing that runs to the throttlebody. The intakes of the turbos will also be run underneath the car and go up behind the radiator and to the airflow meter or mass-air sensor. We might actually scrap the airflow meter/mass-air sensor if we can get our piggy back MAP system to work which also allows us to dial in a very nice and safe fuel curve. This would make routing the intakes even easier. So essentially this is my plan that I had come up with a couple of years ago. Now it just needs to be executed if there are enough people interested:^)

Drewster67

I have a feeling not too many owners will want to commit to a "Unexecuted contigency Plan" -

I, however, am a risk taker. Who knows, when it's all said and done - You may have "Serious - Don't F**K with me Motor" that'll run a 11/12 second 1/4 mile.

I'll send you my contact information via PM.

TurboTim

John,

After all the things I have accomplished you are now doubting my abilities;^) You dont need watercooling for the turbos. Have you ever seen an oil-cooled bearing section for the garretts that contain no water passages? I can assure you that they do exist and I put one on a Skyline R33 GTR. So that problem is solved. You dont need external wastegates either as the internal wastegates discharges into the downpipes. But hey, I could route some external wastegates if there was a market for it. I can also build some custom headers if people wanted to pay for it. As far as the air sensors go.It is easy enough to use a MAP system which eliminates the air sensor altogether. If that is not feasible then it is easy enough to route the two intakes together so they use the existing mass-air sensor. Problems solved. I will agree with you about using an oil pump for the turbo drains but it can not be as complicated as the one we just installed on a turbcharged BMW M3. As far as fuel, timing, etc.......I dont think the compression on these 928s is anymore then the 11 to 1 compression of the 968 which was sucessfully supercharged by us. As long as the system is well though out and tuned, it can be powerful and reliable. Its that simple.

John Anderson

Tim,

I didn't bring you up in my post. I have worked on the 928, I was simply stating what I felt would be things that need to be addressed. I have never doubted your abilities, and I didn't say such a thing in my post. It was not directed at you.

I think that if you get a chance to work on the 928, you have a good shot at getting the job done.

Nothing pointed at you , I'm sorry you took it that way.

Take Care!

TurboTim

Hey buddy, I am sensitive:^)

Randy V

Wow, I didn't realize that I'm living in the 928 SC / Turbocharging mecca.

Between Huntley Racing, Speedforce Racing, and Anderson Motorworks, I should be able to visit them and see some real-world results!

Idiot Savant, please cease your foolishness here. I have sent you a PM that includes additional advice on why you should end this charade.

Steve Cattaneo

Tim, I have no doubt, you can build a tt 928. Please correct me if I am wrong. But is it harder to PROPERLY tune TT on a high compression engine (non turbo). The boost of a turbo is nonlinear, with the power band more toward top end. Turbo have a power lag, yes you can spool them up quicker but that will make a lot more boost .if true a turbo is not the best choice for a torque monster

My choice is a positive displacement screw SC. (lysholm) which has a flat torque curve from idle to WOT. A lysholm will compress air at idle. Yes it is more intrusive to the engine but the power and torque gains are greater then any system out there.

Good luck

TurboTim

[QUOTE]Originally posted by steve cattaneo:
[QB]Tim, I have no doubt, you can build a tt 928. Please correct me if I am wrong. But is it harder to PROPERLY tune TT on a high compression engine (non turbo).

Not neccessarily.We have been tuning some supercharger systems and have been running into problems of maxing out the mass-air sensors.When this happens your car will run lean and eventually detonate. Superchargers require horsepower to make them spin.Horsepower requires air. This means supercharger systems have to injest more air (which is still metered by the mass-air sensor) then a turbo chager system to make the same amount of power.

The boost of a turbo is nonlinear,

So is a roots blower;^)

with the power band more toward top end.

Your powerband depends on what size turbo you use.You can use a smaller turbo to spool up quicker which will give tremendous bottom-end torque with lack luster top-end. On the other side of this you can isntall a monster turbo which will have no bottom-end and insane power on the top-end. Again, it is all a matter of turbo sizing. Ideally you would want the best of both worlds.

Turbo have a power lag, yes you can spool them up quicker but that will make a lot more boost. if true a turbo is not the best choice for a torque monster .

You do not need more boost to spin a turbo up quicker.This has to do with turbo sizing. For example..... a smaller turbo will spool up quicker then a larger turbo even though they are both set at 10 psi. Take care.

John Anderson

Randy V,

You won't find any real world results on a twin/SC'd 928 at our shop. I'v had the inquiries, but after giving the owners a look at a "need to do list", we felt it best to pass. I would rather build an all motor, big bore, high compression engine. I've done the SC/Turbo thing, its fun, but there is something to be said about getting the power the minute you hit the mat, and driving it hard with a simple plan. I know you can make big power on the motor, hell, we have taken a 2.5 liter NA from a 84 944, bored, pistons,3.0 liter crank, cam, headers, some tuning, headwork etc etc...and it is putting 250hp to the wheels for this race season. No SC, no Turbo,stock intake manifold, again, started with an old 2.5 liter block. Its now a 3.1 liter, 14:1 compression race engine. And it has yet to be beat by a 944 turbo on the track :-)

It gets the crap kicked out of it and still keeps going :-)

Take Care!

Normy

Uhmm Tim...

Turbo boost [and as such, power...] depends more on cylinder pressure than simple rpm, as you have implied via the term "high end".

Lower RPM's with wide open throttle is a sure bet to make the turbine [and the compressor-] spool up.

The point, Tim, is that any turbo set up is bound to be TROUBLE with the capitals intended. Some of us on here don't mind that at all- I like working on my car too, but only on basic stuff. I'd still prefer to drive than turn a wrench!

A point of logic: A Roots blower is NOT a "top end" item- these are used on top fuel dragsters for a reason. These are true positive displacement superchargers, and their efficiency is not affected by RPM until extremes. As such, they have great low RPM performance. Vortech, Paxton, etc. blowers are centrifugal type, and they are indeed more efficient at moving air [they don't compress air...they move it, thus they are not true "positive displacement" blowers] at VERY HIGH SPEEDS.

Normy!
'85 S2 5 Speed

John Anderson

<img src="http://boards.rennlist.com/upload/DynoAnderson28ltr.jpg" alt=" - " />

I don't know about turbos being added for top end power. This is a chart of my own 951 after I built the 2.8 liter motor.

The power is definately in the middle of the usable rpm band. The torque was almost too much that low down, but I'm posting the graph to show that when a turbo is matched correctly to the engine, you can have huge power thats not in the red on the tach.

Take Care!

Steve Cattaneo

Tim,
Positive displacement compressors roots (lobe), lysholm (screw) have linear power curves. The roots (Lobe type) super chargers are old technology they pump air, lysholm compresses air at a rate of 2646lbs per hour. Thus producing a higher charge pressure than any other belt driving super charger out there, that is why all the big power players, automotive and marine use them. Roots SC max out at 14000 rpms, screw SC max at 20700rpms making a lot more power. <a href="http://www.kleemann.dk/compressor/index.htm" target="_blank">http://www.kleemann.dk/compressor/index.ht</a> <img src="http://www.kleemann.dk/compressor/index.htm" alt=" - " />

Click on G4 then on E55, 718lbs of torque

TurboTim

Normy,

I wasnt trying to imply that a turbo makes boost by rpm alone. I was trying to make a simple comparison that was easy to understand so I used the term top-end.

Steve,

Screw type blowers are very similiar to turbos. They make boost rather suddenly (which is usually accompanied by the torque peak) and maintain it into the high rpms (where peak power is usually made). They do not make boost gradually as rpms increase as in the case of the centrifugal blower. This was the point I was trying to make.

deltaP

Turbo Tim says: "We can turbocharge or supercharge any vehicle. Take care."

I've got an EV-1 that could use a little pep! Think you can give her a little boost?

Just playing with ya...

Back to this really cheezy Jackie Chan racing flick I'm watching. I like when they speed up the film by 50% so it looks like they're going fast.

GoRideSno

I think I am repeating myself here but this is a better thread for it.

I saw a GM engine at the auto show that had a turbo sitting on top in the middle of the V. With a redesigned intake I think there would be space for it on our cars.

The intake may be as simple as a 3" tube sitting on top of 4 runners going straight down to the ports. Use one of these for each side (Something similiar to a 944 intake) As Jim Bailey pointed out in another thread once you start forcing air rather than sucking it, things change. If anyone has the PET they should take a look at the older 911 turbo intake and see how very simple it is.

John Struthers,
Our path to 928 ownership was very similar. The '93 and up Supra TT is what got me interested in fast cars.
I searched for one only to find that even an abused 93 6spd with 100k miles will draw well in excess of $35000. Why is it that the Supra TT sells for usually twice as much if not more than a similar year 928 (except maybe GTS) when they have similar stock performance figures and similiar new sticker prices? I believe it is because they are easily and realitively in-expensively modified to make more power. This is what has made the Supra TT legendary. The NA Supras with 100 less HP than an S4 sell for about as much as an S4 if not more. This is due to rub off from the culture around the TT.
Not too long after all this SC and Turbo talk starts showing up a bit more in performance figures I believe there will be an increased interest in our cars and the values will rise. We have to make cheap power for the 928. As new cars get faster and ours don't, we will see more of them leaving the roads for the dismantlers.
Andy K