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Motec would be my recommendation, but more important is to find a very good local tuner and see what they recommend. If they recommend a system that's not very good, they may not be as good you've heard
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Old 02-28-2007, 05:31 PM
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Bonjour!

Congrats on your turbo setup--very nice.

The variable vane turbo's are the coming thing---we've been using them in diesel truck engines for some years now. Flatter torque curve, improved fuel mileage, and yes, they do make more hp. Contrary to what others have said, diesels make a huge amount of exhaust heat. The more the better, just as long as you properly cool the intake charge.

As for the headers, the are many arguments for and against. You can jet-hot coat and thermal wrap your pipes to take advantage of the heat content that turbo'd engines live for. Removing the heat is a bad idea.

You might go to the 928 thread, and check out Herr-Kuhn's 32V and 16V (928) posts to see what turbo's and electronics he is using. He is still under development on the 32V setup, but is showing great promise. You might notice that his headers, although tubular, are very short and not equal length, I suspect more to space limitations than anything.

regards---rhjames



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Old 03-02-2007, 01:34 PM
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935turbo,
I applaud your audacity and courage in undertaking this project. I had no idea that projects of this scope were so politically incorrect in your country. Now, that's a pity.
I am curious on why you chose this engine configuration. It appears to be more of an aircooled 997 turbo engine than of a mock-up 935 engine. Like others that have posted on this board, I favor the 3.6l engine for your project. Keep the 3.3l in its current configuration and store it if the collector value of the car is of concern. Though you have already changed your brakes to 996 TT versions.
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Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 03-03-2007, 07:19 AM
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Salut et bienvenue!

You project looks exciting! I wish I could have that kind of engine in my car. Keep us posted.

I spent a year studying in Grenoble at Ecole Supierure de Commerce. I visited Paris many times. J'aime la France!
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Old 03-16-2007, 11:53 AM
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Thanks Jeffrey.....

And now...some news.....

I'll get the engine case machined probably next week.....extended diameter for 3.5 L Mahle cylinders.....inside reinforcments profiled......all gaskets "plans' machined to be perfectly surfaced.....I'll post pictures as soon I'll get it.....

and I'm still looking for the EFI right choice......

Serge
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Old 03-16-2007, 01:38 PM
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Hi all, I just stumbled on to this thread and see it has had no discussion in almost a year.
I can help define one aspect of the turbos in question. I can assure you these are Garrett VNT25s as used on the Chrysler 2.2 VNT gasoline engine. I worked the program. They are not diesel VNTS. I believe the vintage is 86-90. They are the FIRST automotive VNT turbos (predating Porsche's claim by roughly 20 years). Materials are good for 1835 degree F. I see the designer added a wastegate which is required as turbine flow will be beyond the vanes capacity.

Regarding what are obviously RSR style headers I like them. High performance engines, even turbos, should have equal length primary tubes. The length can be debated but one must "blue print" so to speak the entire system so each cylinder is operating to the same flow and pressure condition.

I witnessed an extreme application. I was on an Indy engine project testing unequal primary manifolds (turbo biased) vs. the standard tuned headers (engine system biased). At high boost and RRM the engine would misfire just as the engine builder (Ed Pink) said would happen. Tim Richmond qualified with tuned headers that year.

Last edited by copbait73; 03-01-2008 at 07:58 PM..
Old 03-01-2008, 07:02 PM
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Good news......thanks.....

the works on my original engine are stand by....still waiting to take the right decision for the EFI and designing (or finding...?) the right gaskets (head cylinders 3.5/962 heads, and base cylinders..)....the engine case has been machined and the heads gaskets surfaces to......





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http://www.club911.net/viewthread.php?tid=65004
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Old 03-02-2008, 02:18 AM
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Equal length headers will always make better power than a log style or other unequal length headers. The power curve will start wider and pull higher with a good EL header system. What he has is a good header design. If it is made of stainless (which I expect it is) it should retain heat fine.

Though the the turbos look a little small they will probably be fine. The biggest thing will be accurate control of the turbos, in order to get the best power curve. I am guessing they were controlled by MAP on the Dodge engines. The new Porsche turbos are controlled with a pulse width modulated controller on the turbo. So the control of the vanes is inherently more accurate and responsive than a vacuum based system. I am sure the MOTEC or Autronic systems can handle the electronic turbo controllers.

Good luck with your goals. Why not look into taking your car out of the country to have it tuned. Perhaps Germany or England. They may have better tuners for Porsche specific applications.
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Old 03-02-2008, 08:37 AM
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Quote:
Originally Posted by turboteener View Post
Though the the turbos look a little small they will probably be fine. The biggest thing will be accurate control of the turbos, in order to get the best power curve. I am guessing they were controlled by MAP on the Dodge engines. The new Porsche turbos are controlled with a pulse width modulated controller on the turbo. So the control of the vanes is inherently more accurate and responsive than a vacuum based system. I am sure the MOTEC or Autronic systems can handle the electronic turbo controllers.
Brett, your comments are right on. The GT25s will be pushed to their limit to handle 500WHP. The Chrysler 4 was probably good for 250HP uncorked with W/G added.
Old 03-02-2008, 08:58 AM
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What a dream project you are doing!!! Congratulations and good luck, now for my 2 cents worth... Wrapping the headers will do a tremendous amount to control the heat and help protect the surrounding items. I had to do this on a drag race car w/ a very long set of Hooker headers to keep from melting a fiberglass hood. The difference was amazing! Obviously on turbos is to get the heat to them, and any lost is a loss of H.P. You can obtain this product form www.summitracing.com and I know they ship overseas. I would even consider double wrapping them in your situation. The only thing not to do is ever try to pressure wash it, as it will blow apart. Good luck!!! Craig
Old 03-02-2008, 03:46 PM
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Be careful when wrapping headers it will kill them in a hurry. It does work but it will really raise the temp the metal sees. Plus there is a huge amount of moisture that gets trapped against the metal. I ran wrapped pipes on the 914 and they were in rough shape when I finally took the engine out.

I bet with those turbos though the off idle performance will punch your eyes through the back of your head. Can you say instant boost. It will choke off on the top though. I won't even entertain anything smaller than a GT28 on most street cars. Even small four cylinders. I am thinking about running two small T3s on my 2.4. Junkyard style. They are easy to find and should spool quickly. May even have to run something smaller like a couple of T25s.
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Old 03-02-2008, 04:30 PM
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Quote:
Originally Posted by turboteener View Post
Be careful when wrapping headers it will kill them in a hurry. It does work but it will really raise the temp the metal sees. Plus there is a huge amount of moisture that gets trapped against the metal. I ran wrapped pipes on the 914 and they were in rough shape when I finally took the engine out.

I bet with those turbos though the off idle performance will punch your eyes through the back of your head. Can you say instant boost.
I can get my hands on a pair of those GT25VNTs for my 3.6L but have the same concern regarding size. Still, that small compressor housing T25 can feed a lot more air than looks suggest and I'm sure they are no smaller than the K16s I'm setting up now. I'll get one and get reacquainted with the specs.
The vanes on the Chrysler/Dodge were ECU map set using vac however they can be controlled with pressure like a W/G. The canister is twin port allowing part throttle open vanes also. This is a big plus W/Gs dispensed with years ago. Don't know why.

Last edited by copbait73; 03-02-2008 at 07:43 PM..
Old 03-02-2008, 07:39 PM
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I wonder what the compressor map looks like? It would be interesting to see where it nose into surge. I have had my hands on a GT15 before. Was gonna use it on a FSAE engine. It was tiny.

Where those Garrett or Mitsubishsi turbos?
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Old 03-03-2008, 06:56 AM
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Originally Posted by turboteener View Post
I wonder what the compressor map looks like? It would be interesting to see where it nose into surge. I have had my hands on a GT15 before. Was gonna use it on a FSAE engine. It was tiny.

Where those Garrett or Mitsubishsi turbos?
I think I can locate a GT25 map. I know you have years of experience but 3.4L divided by two turbos is only 1.7L. As I recall we applied SINGLE GT25s to 3.2L motors however they were flow restricted and HP was no more than 250.

Did I give you that GT15 turbo?
Old 03-03-2008, 07:24 AM
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Here is the map for the Garrett GT25R:


I am looking for a map of that Chrysler VNT.

I would never consider a single GT25 for anything bigger than about 1.3 litres. What would possess anyone to try a single GT25 on 3.2 Six (Porsche?)? That turbo is tiny. I think a GT28 is a good turbo for a 1.6-1.8litre engine. Maybe a 2.0 if it has head flow like a VW four cylinder. I would be tempted to try two of them on a 3.5. Maybe a pair of GT2871s for good drivability, not ultimate top end power, but it would work great on a daily driver level.

I got the GT15 from Garrett. It may have been a GT12, it has been awhile since I looked at it.
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Old 03-03-2008, 06:28 PM
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Originally Posted by turboteener View Post
Here is the map for the Garrett GT25R:


I am looking for a map of that Chrysler VNT.

I would never consider a single GT25 for anything bigger than about 1.3 litres. What would possess anyone to try a single GT25 on 3.2 Six (Porsche?)? That turbo is tiny. I think a GT28 is a good turbo for a 1.6-1.8litre engine. Maybe a 2.0 if it has head flow like a VW four cylinder. I would be tempted to try two of them on a 3.5. Maybe a pair of GT2871s for good drivability, not ultimate top end power, but it would work great on a daily driver level.

I got the GT15 from Garrett. It may have been a GT12, it has been awhile since I looked at it.
No, no I didn't suggest a T25 SINGLE on a 3.2 Porsche. Second, this GT25 may not be the compressor on the T25VNT.
Finally, I said I recall T25 singles used on 3.2L DET cars with full restrictive CATs and low power settings. Mainly torquers meant for bottom end power ending around 4000RPM. I think they were GrandAms roughly 88-90 timeframe.
But, using this map, If you look at a Porsche 3.3L with twins you look at say, 3000 RPM, 20#/min at 2.0P.R.(1 bar) and 6000, 48#/min, 2.0P.R. Taking these flow readings at half you are centered on the map.
Actually the VNT can drive you right up the surge line. In this example it's at a full 1 bar at 3000RPM. Obviously this is a problem and the reason why most modern turbos use recirculating inlets and broad range impeller designs to improve the surge line so you can use your more desirable higher flowing turbos.

Last edited by copbait73; 03-03-2008 at 07:44 PM..
Old 03-03-2008, 07:32 PM
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Originally Posted by 935TURBO View Post
Thanks Jeffrey.....

And now...some news.....

I'll get the engine case machined probably next week.....extended diameter for 3.5 L Mahle cylinders.....inside reinforcments profiled......all gaskets "plans' machined to be perfectly surfaced.....I'll post pictures as soon I'll get it.....

and I'm still looking for the EFI right choice......

Serge

being that you are in France , go here www.dtafast.co.uk they have a French Distributor for their product as it is also used on FF3 cars etc and it would be a good choice for your EFI system.......

For turbos i would go with GT 28 as a min , 545-598 whp @ 1 bar is very much in reach with your setup , gt25's would be dead on the top and put too much heat in to your IC over 1 bar

Last edited by A.Wayne; 03-03-2008 at 07:43 PM..
Old 03-03-2008, 07:39 PM
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I would never consider a single GT25 for anything bigger than about 1.3 litres. What would possess anyone to try a single GT25 on 3.2 Six (Porsche?)? That turbo is tiny. I think a GT28 is a good turbo for a 1.6-1.8litre engine. Maybe a 2.0 if it has head flow like a VW four cylinder. I would be tempted to try two of them on a 3.5. Maybe a pair of GT2871s for good drivability, not ultimate top end power, but it would work great on a daily driver level.
3100 V6 of GM, which was reworked by MCLAREN. Check it out:http://www.golivewire.com/forums/peer-sptoat-support-a.html


Quote:
I got the GT15 from Garrett. It may have been a GT12, it has been awhile since I looked at it.
Did I send you that turbo? I sent numerous GT15s to FSAE teams.
Old 03-03-2008, 08:28 PM
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No, no I didn't suggest a T25 SINGLE on a 3.2 Porsche. Second, this GT25 may not be the compressor on the T25VNT.
Finally, I said I recall T25 singles used on 3.2L DET cars with full restrictive CATs and low power settings. Mainly torquers meant for bottom end power ending around 4000RPM. I think they were GrandAms roughly 88-90 timeframe.
But, using this map, If you look at a Porsche 3.3L with twins you look at say, 3000 RPM, 20#/min at 2.0P.R.(1 bar) and 6000, 48#/min, 2.0P.R. Taking these flow readings at half you are centered on the map.
Actually the VNT can drive you right up the surge line. In this example it's at a full 1 bar at 3000RPM. Obviously this is a problem and the reason why most modern turbos use recirculating inlets and broad range impeller designs to improve the surge line so you can use your more desirable higher flowing turbos.

Oh sorry I misunderstood your post. Yeah I could see GM doing something like that on their big sedans. I bet it did make good torque, but I am sure gas mileage suffered and the engines ran hot. The turbo would be way too restrictive for that size engine. I found some turbo Dodge websites that dissected the VNT. The compressor wheel is tiny. I am afraid it is not worth it. May be great for bottom end but will peter out up top. Don't need lots of bottom end on a 1900lb car.
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Old 03-03-2008, 08:51 PM
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