Shane

David congrates on the Stage III, you will reach 500 rwhp for sure. And you are doing it right by pulling your engine and getting it to run right first, and then adding your boost!!



I just got done spending about $8k on an $8k 86 auto making it boost ready... But when I start the tuning phase I won't have to fix a bunch of other crap to make the boost application work right and reliably.

JEC_31

Hi Christian,

FYI, there's been some odd emotional and legal troubles between the maker of the twin-turbo kit and Rennlist so we should NOT discuss that kit here. He posts on the Pelican forum.

The Murph kit posted above is readily available, popular with a very picky crowd, and boasts many positive apsects and very few (if any!) negatives. It's a bolt-on intercooled centrifugal supercharger kit.

Also, check 928gt.com as to the availability of their twin-screw supercharger kit.


Finally: I highly recommend the books "Maximum Boost" and "Supercharged!" by Corky Bell. More high-quality useable info there than on the entire internet.

- Josh

V2Rocket

i dunno, that pic looks like its got 8 velocity stacks...

hacker-pschorr

Or just send your car to Green Bay with a briefcase full of money..

Jim bailey - 928 International

This needs to be read again and carefully.
I just got done spending about $8k on an $8k 86 auto making it boost ready... But when I start the tuning phase I won't have to fix a bunch of other crap to make the boost application work right and reliably.[/QUOTE]

It may sound like a great idea that you can simply bolt on a kit and make big horsepower but the reality is many many cars have been neglected , abused and Mickey Moused by previous owners and "mechanics" over the course of tha last 15-20 Years something as simple as not changing coolant every two years on that low milage S-4 that sat in the garage for years "only drove it 2,000 miles in 6 years" can easily mean that the head gaskets are not going to hang in there much longer. The S-4 which J. Kuhn twin turboed was before he bought it serviced by Greg Brown it had as I recall over $10,000 dollars of repairs in the 12 months BEFORE John got it ! Shane in the quote above DOUBLED his investment in that 86 BEFORE the cost of the supercharger kit. My point is do not be surprised to spend 1/3 for the car 1/3 for the catch up repairs and 1/3 for the kit. Boost is seductive and more feels so good.....

PorKen

A rebuilt MAF, and new injectors are a must have.

Two point five (optional) get the most NA horsepower you can on the dyno. The peak will vary depending on the dyno type, but with DynoJet: S4 > 290, GT(86.5) > 310. Otherwise, boost may just be compensating for an underlying problem, like a poorly designed exhaust system, and you may max out prematurely.

Worse, some punk like me may make nearly the same power NA as the identical engine at low boost, and tell everyone about it.

69gaugeman

And God knows nobody wants that.... ever.....

RyanPerrella

Since you asked and you get a different opinion with everyone else i guess i will share mine now.

I was thinking of a twin screw kit 7-8 months ago but they havent been available for awhile but are apparently going to be ready for purchase with updates to as of yet unknown specs in the next month or two or possibly longer. I then was thinking about a centrifugal but i just dont like the look of the centrifugal no matter how many times hacker tries to tell me differently. Its not my ideal boost method, BUT IT IS THE ONLY KIT YOU CAN BUY AT THE MOMENT! And its got a huge following and i'm sure has all the bugs worked out which the current TT and Twin screw may encounter just simply because they are so relatively new.

I was also considering the mid mount Turbo from Mark Robinson here in Austin. But After seeing the TT setup I will go that route. But I will handle the intercooling and plumbing myself because i prefer air/water over air/air. And John is very smart in my opinion in offering the hotside parts which would include the manifolds, turbo's and downpipes. Its probably the mst expensive option, but the thing i love about a turbo is the ability to alter boost levels on the fly. I dont always need 550 RWHP! In all honestly i probably wouldnt use that much in most situations, i would dumb down the boost to 4psi in regular driving and get what, 400+ RWHP or there abouts on my GT. Then when i want more i can dial it up, maybe have 3-4 different levels and go from there. Thats something the SC cant give you. Also at these levels i would think 12psi from a turbo will probably give you another 40-50 HP then the equivelent on a SC just because the SC does draw some power, how much, well thats depends on what type. But for maximum power per psi of boost the turbo is more efficient.

This thread can go forever but since you asked, i offer my opinion and the way i am currently thinking of going.

Oh and as Jim B said, you can easily end up spending 25K on an 8K car. So you better love your 928! A 500RWHP 928 is a hard thing not to love if you ask me!

AO

Dave Roberts also has a kit. It's a Twin Screw Supercharger kit. You can see it by going to www.928gt.com or on my webpage (see link in signature). His stock kit is just below your target RWHP range, but I hope to show (this month) that it can achieve 500RWHP or close to it. This is the kit that's on my car.

Tim Murphy, as previously mentioned, also sells a kit that has proven to provide 540RWHP. You can find out more about his stuff at www.murf928.com.

Both of these vendors are proven reliable and dedicated to our cars. Both kits are about the same price.

There is a TT kit out there, but none have shipped and the vendor has been banned from Rennlist. Just do a search for "Twin Turbo" and I think you will find what you're looking for, but it's outrageously priced IMHO, and is not a true bolt-on kit requiring extensive body mods.

And just to echo what others have said, you really need to have a solid car. If you already have a car, plan on at least $2k on parts to refresh this, that, and the other.

All told, not including the car, it takes roughly $9k-$10k to get an 87-91 car up to the RWHP levels you're looking for. Factor in the car, and for $20k~$25k you can have a car that will beat 99.8% of the cars on the road in straight line performance and overall driveability.

Tony

Ok Opinions.
I very happy with the Twinscrew/Autorotor i have on my car. IMHO, Looks good and the power hits RIGHT NOW. Its as if your driving around with Big Block under the hood. Like all the systems it has its PROs and CONs but if you dare voice them on here your likely to get into a pissng contest between TS-CF-and Turbo...which has been beaten to no end on various threads (do a search for either setup).

Do what you feel you like and want.

You will be happy either way in the end.

Each passing month we learn a bit more about the capabilites of this engine under boost and the performace you can get into the car. I mean there are 18yr old PLUS cars on here, with over 100k miles on them that are putting out more Hp and TQ than a Carrera GT!

Gretch

Or send a half a briefcase full of money to the cheese heads, and do it yourself...........

I did, I was the first DIY, and my car is still kicking it HARD going on 4 years now. The Murph stuff is awesome, as are the cheese heads!

FlyingDog

His prototype has a 100% stock engine. The minor body mods are optional.

ChristianR

What 1/4 mile times does a 500hp 928 achieve, any one tracked there car?

Thanks

AO

Me too!

AO

Here you go! Lots to read!

https://rennlist.com/forums/showthre...81#post4109781