Deeps

First of all, apologies if the answers to my questions are out there already (I've had a good search around and I can see that they have been asked, but I'm not sure that they have yet been answered in any detail). I ask out of interest and because I suspect that there are quite a few SC'd 996s out there now (whether by TPC, Evo or by anyone else ...).

Anyway, here goes:

(1) Has anyone tried their SC'd 996 (3.4 or 3.6) out against a stock TT driven by a similarly skilled driver? What happened? I've seen mention that the SC'd car can take the TT up to about 100mph, but after that, it's the TT. Is that people's experience?

(2) Has anyone had the pleasure of driving both a SC'd 996 (3.4 or 3.6) and a stock TT? How did the cars compare? I've heard (and would expect that) the SC'd car's acceleration is more linear, but is there anything more to tell in terms of overall acceleration, performance. etc?

(3) Does anyone have dynos for both a SC'd 996 (3.4 or 3.6) and a stock TT, for comparison purposes? I haven't seen any out there ...

(4) How does the noise level of the SC work out in practice? Are they a lot noisier than stock 996s, or indeed stock turbos?

It would be great to get some answers, if anyone out there has the time/inclination/experience.

Thanks in advance for your time

Deeps

wwest

Superchargers are typically designed to bring on the extra manifold pressure at a lower RPM than turboes can provide. The short-coming of the SC is that once the engine reaches a higher, mid-point, RPM the SC would overboost it without serious pressure by-passing, blow-off. Obviously the shortcoming of the turbo is a lot of exhaust flow must exist before it can be spun up to speed.

I'm really surprised that no one has designed a variable speed hydraulically*** driven SC such that it can develop lots of boost at a very low engine speed but have the speed/boost moderated as the engine RPM climbs.

Remember that for an SC to work at these lower RPMs a fixed ratio belt drive must give it more air movement capacity than the engine at any given engine RPM. If the air movement capacity of the SC is say, 5%, over the engive at 1500RPM then that 5% becomes way too much boost fairly quickly as the engine RPM climbs.

Studebaker did that back in the fifties but using a variable ratio V-belt drive.

***larger, or varible capacity power steering pump...??

I would go with the SC as the winner since the engine HP comes on earlier in the RPM cycle.

The Turbo is predominant in the marketplace only becuase of it's lower overall expense and simplicty.

Scott_in_Houston

Keep in mind that a TT is a totally different engine and block than the regular NA 996 (non GT-3).
The TT is over engineered and is capable of taking much more boost than stock while not harming the engine or engine life.

As for the 996 and super charging. (Disclaimer: personal opinion coming) The 996 M96 engine is probably near it's full potential as is. I would be worried about super charging this engine and severely shortening the life of the engine or worse, causing it to grenade.
In general, a super charger may be a better solution, but I would definitely buy a 996 TT before I ever considered spending the money to SC a NA 996. The risk is not worth the potential disaster. Also, I don't think the SC'd 996's will compete with the TT anyway.

RoverRon

i guess you guys are saying that Honda makes a better engine than Porsche because they super charge their N/A engines all the time.

mlambert890

I think in terms of numbers the SC cars compare pretty favorably to the TT from 0-100. Of course the TT has lots of other upgrades that would also have to be added to a base 911 to get the total package (suspension, brakes, etc.) Hard to say if the SC 911 would still be cheaper than the TT if you went the whole distance.

In terms of how hard the SC is pushing the engine, only long term data once these SCs have been on the market for a long while will really answer the question.

Deeps

Thanks for the replies so far. We're still searching for that elusive owner (or even owners ...?) who can tell us about their experiences in direct comparison to the TT. Come on guys, don't be shy ...

mlambert890 - I agree - I have a C4S but there is still quite a bit I would like to add in alongside the SC option if that was the route I ever chose.

scott - I completely respect that opinion. Only time will tell, I guess. The thing for me is that my black/black C4S is the perfect 911 for me, in terms of styling. I actually had the option of buying a TT (and the funds to do so), but the side vents just don't do it for me at all (I'm sure plenty would disagree). For me, TT-like performance in a car with the looks of the C4s would be automotive perfection.

wwest

Personally If I wanted to add an SC I would start with a TT engine and scrap the turboes. I have often thought of experimenting with a hydraulically driven variable speed but starting with a turbo 944 as a test mule. The 944 engine would already be detuned, compression lowered.

Itzkirb

I just installed the SC and would like to reply, but want to get more fatcs. Most of the cars I'm around are far from stock so it is difficult to compare. I have yet to Dyno it as Akkurat is still making some final tweaks to the car.

I have a track event this sunday, so maybe I can gather some data there with Stock Turbos.

As for the noise...I like it! I thought PSE sounded good before, but now it's even better!

Deeps

Itzkirb,
Thanks for the reply - I was hoping that your name would pop up (having followed the details of your install with great interest). It would be really great if you could keep this thread in mind as and when you have any concrete info ...
Regards
Deeps

1999Porsche911

If you drive alot on the open road averaging over 100 mph, then the turbo is the way to go. If you want quickness and power up to 120, then supercharge is more fun and instant. My 3.4 regularly wins me a beer from 2 TT owners around here. Haven't taken them on past 120 mph (not many roads allow that), but i am able to watch them in my rear view mirror up to that speed.

wwest: You said - "Superchargers are typically designed to bring on the extra manifold pressure at a lower RPM than turboes can provide. The short-coming of the SC is that once the engine reaches a higher, mid-point, RPM the SC would overboost it without serious pressure by-passing, blow-off."

There is no chance of overboost with a fixed superchager installed. Maximum boost is established mechanically by the ratio of pullys at maximum RPM. Boost is based on engine speed and not the speed ofthe car. Aftercooler maintains intake air at 20 degrees above abient temp. Exhaust is much cooler than the turbos.

Sound is not any louder than stock except for a slight turbine sound from the supercharger. A pretty cool sound I might add. Much like a jet engine moving around the runway.

Key to success is the abilty of the chip programer to balance the stock emmision sensors and fuel controls to properly accomidate the increased boost.

wwest

Assume WOT on the engine at 1500 RPM, in order to provide any boost pressure at all the air movement capacity of the SC MUST be greater than the engine at 1500 RPM. You can do that with SC volume or SC speed or both. Most systems choose speed, running a low volume/capacity SC at a speed high enough above the engine RPM to always have more air movement capacity than the engine can handle. As the engine RPM climbs toward its "native" (without SC) peak HP if you don't reduce the SC output you will blow the engine.

1999Porsche911

I have no idea what you just said wwest????

Webtool

WWest:
On the subject of variable speed driven superchargers, I would offer the opinion that a hydraulic system would be inefficient compared with a split pulley type variator. Mechanical variators are too heavy and complex. I wonder at the possiblities of an electric drive system with AC inverter control receiving input from the engine management system?

wwest

I agree, a variable frequency AC supply of some significant higher voltage would be perfect. The interesting thing is that the engineer I discussed this with said the the higher the SC drive motor speed is the smaller the motor itself can be.

Hmmmm....

A highly efficient but small and light motor squirrel cage blower SC design.

1999Porsche911

A highly efficient but small and light motor squirrel cage blower SC design


You would be driving around with a mortor shell in your car! The current SC's run so hot now at 70,000 cuz they are so effieciant. I couldn't imagine a blower needing to turn 150,000 200,000 RPM just to get the same amount of air you get from curent systems. If a bearing went...it would be probably take out the back end of your car. In addition....to get as much air from a smaller blower, the air would have to be compressed even more and that would further raise the temperature of the air. An intercooler will only cool the air so much I guess you could carry an ice chest in your back seat and run you're plumbing through that.