Guest 928tt

Get a twin turbo set up.

bcdavis

Dude, it *IS* a twin turbo setup...

Guest 928tt

Yes i know it is it is mine .

toofast928

Yea, My hats off to you, routing the piping to and from the front grill area. Looks clean.
I'm in the process of installing a air to water intercooler.

Tony

Airflite40

Maybe you will notice it when you put the hood back on

Okay. I'm next in line for Herr-Kuhn's Turbo-my-ride!

tommytomaso

i see the piping looks nice and tight....but if the next sneaky curb takes out the nice ''s'' spoiler will it also take out some piping?

ceedee

why do you thing this car goes to publix for the weekend shopping?

Kevin Michael

John, is the air to air ic effective for this set-up and why do the sc guys go air to water? Is the air to air only affective for the turbos?

zoltan944

since your SC is linear boost, meaning as your rpm climbs you reach maximum boost. Routing ALL that piping for an air to air is a little too much pressure drop and makes it look REALLY busy. With a turbo, your piping has to come up from the header/exhasut anyway, so you run it throught an AtoA then to the intake. Also, with the way boost comes on and the easier controllability of the turbo its a good match up

G Man

Hey John, That is impressive. Is this something that will be available in kit form in the future. If not perhaps a detailed writeup with photos and part numbers. I love turbos!

Charlie944

John, are you aware of the maker or brand of the Callaway OE wastegates? Or was it all strictly in house? I have had mine apart for a rebuild in did not see any part numbers or markings indentifing it. I wish the 928 manifolds were the same as mine...I would not mind having a spare or two. Does the turbo hang off the bottom of your manifolds like this?:

SwayBar

Properly implemented, both do their jobs well, with pros and cons for each.

For a street car, the air/water is more than sufficient and easier to mount.

For a race-car, less is always more, so I would go air/air as there are less 'moving parts' to fail, and generally, there is more room to mount one.

Herr-Kuhn

There two main reasons for the air to air over the air to water:

Efficiency...sized properly, about +10-15% over a closed loop air to water system
Reliability...no pump or liquid to move about.

You have to remember, your goal is to drive heat back out to atmospheric air. With the air to air you have the folloing steps:

Charge air heats IC core
IC core exchanges heat to atmosphere

With closed loop air to liquid you have the following steps:

Charge air heats IC core
IC core exchanges heat to water
Water exchanges heat to front IC heat exahnager core
Front IC heat exchanger then dumps heat to ambient.

You can't say that the heat transfer from metal to water is greater, therefore the air to liquid will outperform the air to air...at that point you have only done 1/2 the job...you now have to pump the water somewhere to dump that heat to atmo. yes, I know you can use the AC core...but to me that is silly and complex. K.I.S.S.

ntot=n1*n2...if both heat exchangers on the air to water are 80% efficient and the air to air is 80% efficient...the air to air will have a sufficient advantage. You would be around 65% with the closed loop air to liquid setup and 80% with the air to air.

Now, if you are talking a drag race car or a race boat, then the air to liquid will clearly outperform the air to air. In the drag race situation you can super chill (ice) the water after each run. With the offshore boat you basically have an infinite supply of cold water....this is the path to big cooling effect. Neither of these constitute a closed loop system. Last I checked the 928 is not a drag race car or a boat...thus the reason for my selection.

The twin turbo S4 is getting two massive air to air units up front. I could also easily fit a very unique twin inlet air to water design (believe me it would be easy and I almost did it)...I'll see where costs play out on the system with air to air before looking to the air to liquid. I wanted a maximum effort, reliable and simple system. For me that means air to air.

On the Callaway manifolds...actually the 944 manifolds are a better design than the ones he did for the 928...they are very different. My turbo 928 manifold system is slightly better than Callaway's...but they are not easy to make. I have two of the old Callaway wastegates...and there are no markings as indicated above. I can tell you that the wastegates on my 81 were much nicer than those on the 84...we used the 81 setup. The 84 wastegates have a very small opening. Neither is a very good design by today's standards, because the diaphram to valve ratio is way off. But nonetheless they work well and fit in tight spaces. If you can fit it, a Tial 38mm would be perfect for the 944...probably can be done with ease. My manifolds use the Tial 38mm gates.

Ironically, I am using internal wastegates on the twin turbo S4...mainly to keep costs reasonable, but it also allows me to mount each blower at the rear of the bank...not in the middle like the other systems I have done...this allows for slightly better (and more cost effective) manifold design which should free up a few more horses. You can say it should not cost much to make a mifold of the design pictured above, but when you add it all up they are costly to make. The ideal manifold for these setups would be cast iron. If I can swing it and there is enough demand, the production S4 system will be cast iron...problem is the patterns are very expensive...but once you have them the manifolds are inexpensive to make. This would drive system costs down substantially.

I recently reviewed some literature on a TT GTO...on just 6 psig that car sliced out 530 RWHP...it is a 400 HP NA engine and the system is VERY similar to what I am building...right down to the turbos by the look of it. I'm hoping to make 500 RWHP on less than 10 psig on the S4 engine and I think it can be done.

I tend to think that those who rip the chin spoiler off a 16V 928 simply don't pay attention. But to answer your question....the plumbing there is rubber, not steel so it can take quite a bit of abuse. The rubber hoses are dirt cheap compared to the chin spoiler. At least an order of magnitude less.

Koenig928

Very nice, John!

That's alot of work to correct what other careless P.O.s have screwed up. Beautiful job.

(I too have my own laundry list of gripes I discovered with the Koenig rebuild..)

Charlie944

I would love to stick a Tial 38mm in there or similar from Turbonetics but the bolt patterns are not the same. Winter project I reckon. Thanks for the info John! I really like your IC setup with the vertical rows versus horizontal rows. More efficient yet! What brand cores are they?