Whether the compression needs to be dropped depends entirely on the boost curve. Detonation sensitivity is the highest at about max BMEP which is around 4000rpm.Turbo/linear SC have pretty constant boost through the rev range.
This limits the boost to what the motor will tolerate at 4000.
A centrifugal ,"square law " SC makes very little boost at low rpm,a little boost at mid rpm and BIG boost at high rpm.This makes this type of SC a good choice for high compression conversions.These things are basically a turbo compressor with a step up gearbox - Started by ZF many years ago.
Check out Rotrex,Vortech for examples of what can be done.
Obviously , I have NO commercial interest in either company.

Geoff

 

The comparisons that have been made between a SC car and 3LDZ K26 930's or K27-7006 '80 930 with stock plumbing are very inaccurate.. Why don't you compare a SC to a 993TT or like Anthony said a Hyflow 3.6.. It all personal opinion but make sure before you drop the cash 15-20K you ride in one of these modern converted cars..

My recomendation would be to buy a stock 993TT engine and drop it in your engine bay and sell your present NA engine to offset the cost. At a minimum, purchase a '91 and up 965 engine put headers on it and a modern design turbo.. Dollars for dollars there wouldn't be a supercharged car that could beat it..

I'm not bashing S/C cars I built a Knoxville 3.2 engine in the early '90's... Buy the time I was done with it and went through all the "teething problems" I wish that I just bolted in a 930 engine... Bolting on a SC is one thing, intercooling and programming the ECU is another..

 

Kevin,
I agree with most of what you say to a point! I was trying to highlight some of the misconceptions that pop up when people start to debate the turbo versus SC conversion route.Surely a decision is best made when all the facts are in place ?
I believe that you are a very highly regarded turbo builder (seen your posts on the 993TT forum) , so maybe you are a little biased ?
In a past life I did the ECU bit so I know what you mean!!
All the best

Geoff

 

I'll admit I am a little bias.. I do also have a 964 NA car sitting at home.. Many of us including myself started with VW, 914's 3.2's before getting into forced induction.. SC was always an option. My main point is, look at the $$$ spend, and look at the end result. Even though SC and turbocharging isn't apples to apples.. Before making the plunge, do your wallet a big favor and drive the cars back to back..

 

My thoughts exactly!

I know that there are people out there who would always want to start with a bone stock car over one that has been modified... But if you have a car that has been especially well cared for and has all the goodies... I'm sure someone would want that car knowing that they could potentially save thousands...

 

Marc,

I totally agree about enjoying the car for the "here and now". I always lived that way myself. Still do for the most part. However, after owning my last '79 SC for 19 years with modified aluminum turbo body, 3.2 L max moritz P/C, carrera crank pumping out 270 hp in a 2390 pound car, I finally one day decided to sell it. You would think I had the plague. Or the car did at least. This thing was such a Beauty and quite the beast. It was and still is one of the best NA 911 I have ever driven. Fast nimble and could out-handle most other cars I have driven and the list is long. The problem was finding someone to actually look at the car. I spent months trying to move it but everyone just stayed away because they were concerned because it was so heavily moded.

The "here and now" is great but one day the "here and now" moves on to 'bigger and better' and you can sit for months or years trying to sell it. I finally sold the car after a year of trying and I got $22,500 for a car that should have sold for $26,500. Funny thing, the first person to actually drive the car bought it. It just took a year to get someone to consider it.

So my comment has its point. One day when you want to sell any moded car and you need the extra $$ to buy the new toy you want you may see it differently.

 

Cobalt - don't disagree your point is valid.

I still would prefer to enjoy my car now and do to it what I'd like to enhance my enjoyment of it. I'll cross the bridge of selling it (modded or not) if and when that day comes. I have indoor parking for 8 cars so just plan to add to my collection.

Marc

ps. Like the new avatar!

 

Thanks on the Avatar. A fun day pushing the car to its limits.

Its not the parking but the Insurance here in Nj that does you in. 8 cars huh!! Boy you can get in a lot of trouble with all that space.

BTW the car looks great with the air duct/fogs.

 

Maybe before you guys go we can all go (the ones in the area) and try to get "hooked up." I've actually dealt and still go to TPC. TPC was were I had my first 911 worked on about 5 years ago. I'll still go there for the big stuff. As you know I've been posting for the DIY stuff so I can save some $$$. Anyways, have you been out to their shop? Nice guys.

 

Garret,
I put a 3.6 turbo motor, suspention, and brakes in a 964,
I installed some good mods which reduced lag and it has gobs of low end power compared to the modded 930 3.3 T . This car is fun . I did have to figure out some wiring but not that hard.
Elliot

 

OT
That's disgusting you lucky dog! What's on the "add-to" list?

c

 

Elliot nice job.

Did you add the rear trailing arms or use the stock arms with spacers? I am assuming you are talking about the headers exhaust changes etc to reduce lag. The 3.6 Turbo engine has considerably more low end power than the 3.3l's to begin with. I like the light weight wheels, looks nice.

I assume you got the engine form a wrecked 3.6T. I guess I need to add that to my list of wrecked 3.6T's that makes a total of 52 cars out of 409 that went to Porsche heaven.

 

To get back to the original question, i think the 965 turbo would be my decision. Surely it would make more sense financially. The other option i would take would be the Ruf RCT Evo (turbo) conversion to a narrow-body 964. When i win the lottery i plan to have both, and you're welcome to try them out when that day comes, if you havent made up your mind in the mean time!!

Here's an RCT EVO press release . . . .

From a rolling start in first gear, a boost spike breaks the tires loose at 3,000 rpm. Shift fast enough, and the tires continue repaving the tarmac throughout second gear. It’s not until third that the Dunlops can settle down and do their work.
The RCT is harder to launch, and it’s nearly a second behind the BTR to 60 mph, but it isn’t long before aerodynamics become a factor. By the quarter-mile, the RCT is at a higher velocity. After that, the needles climb so rapidly we began wondering if White had concealed a nitrous bottle somewhere. The RCT reaches 150 mph in 23.1 seconds, quicker than both theBTR and the factory 911 Turbo. Credit not only to the narrow rear fenders, but also the Ruf windshield A-pillar inserts the BTR didn’t have that reduce drag from the 911’s rain gutters. Top speed is an estimated 193 mph - 36 mph more than the stock RS America.
If speed is the devil, then this RCT proves the devil is in the details. For more details, call Ruf.
By Don Schroeder

heh heh i LOVE the sound of that car

 

I used the entire rear from the 3.6 turbo. because of the addtional stregnth the components have . The entire front end and steering rack is from the turbo but the body was not drilled for the extra width where the sub frame mounts since it was a 90 body, So I had to use spacers on the wfront wheels. Front controll arms have solid monoball bushings It has JIC magic coilovers w/10 &14kg program springs, and an agressive alighnment.
I do need to get a heavier front sway barfor front.
The entire Big red brakes were used. with PFC pads
The car was converted to a wide body and has SRD Seats, 5 pt harnesses and DAS Roll bar. It has a Andial boost gauge in the vent.
The engine has Ghl headers ,B&B muffler, K27 high flow,Tial wastegate,and E boost controller by Turbo smart. This car has wicked low end power and doesn't bled off boost like the stock set up did.It pulls smooth right to redline and doesn't fall off like the stock turbo.

This car is fun!

 

I am sure it is a blast.

I have about the same setup. Although I am using the B&B headers. I decided to keep it street legal and retained the cats deleted the muffler. I am loosing about 20 hp or so because of the cats but it isn't worth the fines. Although I think a 100 cell race cat may be next. Pressure is up to 1 bar at 3200 rpm with 80% torque and full torque not too far behind. I am running about 430Hp and my car drives very much like the ad for the Ruf. There is so much low end torque that it is hard not to spin the tires all the way to 3rd gear if you are crazy enough to push it that hard. The 3.6 has great low end torque and lots of it which is why I like it so much better than the 3.3l's

I don't understand your comment about bleeding off boost. i don't have a problem with that. Is this something you experienced with the 3.3's? Or are you talking about how the HF K27 blows strong all the way to redline vs the stock K27 which dies off at about 5k?