Drewster67

Allright Ladies and Gentlemen - I think the conclusion I have come too is that - Superchargers are possible, but there is no real (in production and on the shelves) proven kit that is both affordable and reliable.

Please correct me if I am wrong - nicely!.

What about Twin Turbos?. If this system could be modified to any shark and be practical yet yield an ungodly amount of hp without major turbo, lag - would you be interested?.

I would like to hear both the negatives and positives and if you have any personal experiences with turbos, please add your two cents worth.

TIA and hope your having a great day!

George 911-V8

DREWSTER67: Now you talking that is the best power you can put on the car no doubt. The supercharger belt takes about 50hp away from the power just to turn the belt. On my NMRA Super Street Outlaw car my supercharger belt cost me 300 hp at the crank. Their is a company in texas that could make a complete turbo application headers and the fuel system. I tkink John Kuhn has a car that if he wanted to turn up the wick could pump out 600hp. I like the turbo no belt to slip, no power loss at the crank.

Curious George

Drewster67

I am in the process of soliciting information regarding a twin turbo application. Stay Tuned for the results. From what I gather so far - it is easier and economically more efficient to go with a twin turbo rather than a Supercharger.

BrianG

Turbo's obviously take advantage of the potentially lost kinetic energy from the exhaust system, but there HAS to be a cost involved with putting a plug in the way of the exhaust flow. I wonder if our engineer-type Rennlisters would care to comment on the comparative losses of S/C vs T/C huffing. The ONE definite advantage of S/C over T/C is that there will always be SOME turbo-lag. I guess that's an issue in a 1/4 mile duel, or the stoplight-to-stoplight thing, but that's hardly the realm of the 928 anyway. I doubt that turbo lag is an issue from 60 mph on up.

It seems that turbo installations are more complicated than S/C ones, and that they all seem to have intercooling. I wonder if these observations are base in reality or just speedy dreams........

My $0.02 worth........

T_MaX

With a car like the 928 (great low end TQ), turbo lag should be a non-issue if the turbo size and trim is properly selected. The correct type of wastegate and BOV will also play a big part in this as well.

Just remember turbo's don't like restriction at either side

Ken D

Since you'd be fabricating most of this anyway...wonder if you could do a two-stage twin turbo setup, with a smaller turbo used to build boost early, and a larger turbo for the "big finish." I believe the RX7 TT used a similar setup (IIRC).
My only experiences with turbos are two blown headgaskets, on stock turbo'd motors with no mods.

Jim Nowak

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva"> From what I gather so far - it is easier and economically more efficient to go with a twin turbo rather than a Supercharger.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">No waaaaaaaay! A supercharger system is much cheaper than a twin-turbo system and light years less complicated. A TT is great for the street and can be very reliable but cheap.....no way. I would love to have a TT 928 but the cost would be way too high and the average Joe couldn't do the install.

Twin-turbos are a good idea but very difficult with all the related parts and plumbing. Stick to supercharging. Why do you think most of the auto manufacturers are using superchargers to make their cars fast??? Cheap and reliable. Mercedes is producing cars with a reliable 500 hp out of 5.5L with a supercharger. On the flip side, the new V12 Mercedes engines have twin-turbos producing 500 hp from a 6.0L.

Supercharger:
bracket, plumbing, pulley, and supercharger

Twin-turbo:
exhaust system, exhaust/turbo manifold, blow-off valve, waste gate or 2, plumbing, large intercooler, oil cooling lines, water cooling lines(some use both water and oil lines), ETC,..........

Jack '84 928s

YOu have to have extra oil pumps on the car, I took mine to a shop to have an estimate for it done. The plumbing is a nightmare! Considering the turbos have to be underneath the engine and then you have route it to an intercooler than the intake. Ill stick with a supercharger. And if I was really going to do the turbos, I would put a LS1 in it with 1 T3/t4 turbo and some metal head gaskets to lower compressin. Ok now you can flame me for that comment. But there is just no space for turbos in the 928.

Drewster67

<a href="http://www.nsxprime.com/ubb/Forum1/HTML/002013.html" target="_blank">http://www.nsxprime.com/ubb/Forum1/HTML/002013.html</a>

This link is from another forum - General Information only, not specific too or related to 928's.

Again - what are your two cents worth.

TIA

srv

Drewster...

According to the owner of the Calloway twin-turbo 928, 'The Bastard', on this very subject he said that turbo charging a 928 is way too complicated as the plumbing is a nightmare since there is hardly any room. The guy should know as he has one of four made.

He also went on to say that a centrifugal supercharger would be the route he would go as among other things, it's a much more straight-forward installation and yield similar power gains.

Do a search and see for yourself as I do not have the link.

Drewster67

It seems to me that if can be done and has been done - what's the real issue besides working in a tight space?.

What I want to know is "How about the performance"

How does it compare to a SC 928?.
What driveline changes are needed to be made?
Can a stock 928 engine handle a bolt on TT?.
Does the FI Sys need modification?.

Same questions related to a SC installation?.

deltaP

drew,

you said:

"Superchargers are possible, but there is no real (in production and on the shelves) proven kit that is both affordable and reliable."

Yet you embark into the black hole of development on a system that is much less stable, much more costly, much more complex, and completely inexistant. Shortest distance between two points is a straight line. Next shortest distance is the shortest path, which is clearly supercharging.

Not trying to flame you. The rest of your questions are good for debate. There are some good answers already posted why supercharging is probably better route. Where does all the pluming go for the turbos? I know people have done it but it would be a tremendous effort.

PS. obviously Porsche likes turbocharging better.

Brent 89-GT

TT is WAY too complicated. Sure they can reliable, sure they can make the same power. Making the power is just a function of how much boost you cram in there. You alter this on a SC by pully changes or charger changes if it is extreme. On a turbo you need to size the turbos and limit boost with a wastegate.

Think about what a TT set-up requires. You will need to fabricate new exhaust manifolds. Then you need to run plumbing up from the turbos to the intake. In that intake stream you need to fit some type of wastegate to control boost. The wastegate needs some controls, like an electronic controller for instance.

Something else to consider is that superchargers provide linear boost and power curves. Turbos react differently. If the exhaust flow is there they make boost. IMO they are much more difficult to safely tune. Having blown two headgaskets on a 944 T, I speak from experience.

There is no way you could do a TT kit for even double what the SC kits go for. Unless they are meticulously tuned, they are tough on the engine.

Paul D

Or you could wait till someone wraps one of those Cayenne's around a tree and drop that twin turbo 4.5L right in! (yeah, right!)

Herr Schnell

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Jim Nowak:
Why do you think most of the auto manufacturers are using superchargers to make their cars fast??? Cheap and reliable. Mercedes is producing cars with a reliable 500 hp out of 5.5L with a supercharger. On the flip side, the new V12 Mercedes engines have twin-turbos producing 500 hp from a 6.0L.
[/QB]</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">I have a serious question (although it may be dumb). Is the choice dependent on engine size? I know the Subaru WRX and little SLK Mercedes use a turbocharger. I know the Cobra and the Mercedes you mention use a SC. The 911 has a TT version. And it seems like Corvette upgraders pick SCs. Does the engine size influence this choice? Or is there another reason the little cars I mentioned use a turbo instead of a SC?