High Boost Superchargers? 12+

[bigmansm]

Why are there no High boost supercharged cars? Is it because no one uses low compression internals with a supercharged car. Is it because no one wants to replace there basic vortech unit to a biggier unit? Is it the availability to pullies, because custom pullies can be made fairly cheaply.

I ask because I'd love to see one. I bumped the boost on My 1994 Mustang and I am get 3 psi at 3k rpm, an it feels great, i think 15psi total, I need to double check. Horsepower is at 650 engine.

Todd

P.S. Marco where you at?

[CarlsbadCroak]

It's a pretty safe assumption that many people who went with a centrifugal supercharger did it partly because they didn't want to get into the hassle of lowering compression or diddling with internals. I know it was a factor in my decision to install a SC on my car (though the biggest for me is that I LIKE how a centri supercharger delivers power, and I'm not a torque addict)

There's also the nasty side effect of how the car drives off boost with low compression. You have to deal with it on a turbo car as well, but proper turbo sizing can get the boost coming pretty early. With a centri though, lower compression can really make it bad in the lower RPM's because you've lowered the unboosted power of the motor and still have the parasitic losses to run the blower, making it a double whammy at lower RPM.

Then you have to run considerably more boost up top to make up for that lowered compression to see any usable gains in that part of the RPM range. Doing that takes you out of the relatively compact V1-V2 max impeller speed and into the larger trim units, which means new brackets and intakes and discharge setups (which you have to fab yourself because nobody is making them), and even more parasitic losses to spin the larger units, further hurting bottom end response.

Long story short, it's a lot of money, time and hassle for limited return.

[DakarDave]

Originally Posted by bigmansm

Why are there no High boost supercharged cars? Is it because no one uses low compression internals with a supercharged car. Is it because no one wants to replace there basic vortech unit to a biggier unit? Is it the availability to pullies, because custom pullies can be made fairly cheaply.

I ask because I'd love to see one. I bumped the boost on My 1994 Mustang and I am get 3 psi at 3k rpm, an it feels great, i think 15psi total, I need to double check. Horsepower is at 650 engine.

Todd

P.S. Marco where you at?

There have been a couple of high boost/low compression supercharged cars.. JCarp had a RMS Stage III kit that ran 14psi @ ~9.0:1 compression.. It put down near 400rwhp and 320ish torque if I remember correctly..

[Jimmyz2]

DAve,what boost were you running when you had Osh tune your car before you went the turbo route?

[DakarDave]

Originally Posted by Jimmyz2

DAve,what boost were you running when you had Osh tune your car before you went the turbo route?

According to the ZT-2 gauge I was running 10.5-11lb of boost.

I had a custom bulldogge pulley 3.05" sc pulley and the RMS 6" crank... with a redline of 6500RPM.. (we were going to raise it but osh suggested against it)

According to the vortech site.. my max impeller speed was:

46032.79 RPM @ 6500 RPM

Just as a comparison.. I believe Marco had a 3.18" bulldoge crank pulley and a 7000RPM redline (or was it 7100RPM) and he's making about 11psi... BUT he has a V1...

He's spinning his impeller @

45566.04 @ 7000RPM
or
46216.98 @ 71000RPM

pretty close...

-Dave

[DakarDave]

also.. the 2.8 had slightly lower static compression.. 10.2:1

-Dave

[bigmansm]

Ah, that makes sense now, Because on the Mustang lower the compression yielding a loss in horsepower and especially torque is not too noticeable because of its highier horsepower output and definately its highier torque output.

[CarlsbadCroak]

I don't know about the base horsepower difference, the 94 Mustang GT 5.0 put out what, 215 with a 5.5 to 6k redline? The M3 puts out 240 at 6.4k stock. More torque on the V8, with a lower torque peak RPM, but not a ton more torque.

But yeah, you had a lower compression engine (8.5, 9.0 at most) to start with, so you can run more boost safely, but to offset the 25hp advantage the M3 motors have, you'd need to run about 2 PSI more than a boosted M3 to make that up.

You can see where it's a balancing act.

[paul e]

Wouldnt part of the issue be related to the impellor speed we develop on the Vortech V1 and V2 units? I forget the peak, but its somewhere around 50k rpms.. Most of us making 11 psi are spinning up pretty close to that. So, for all intents and purposes, we are pretty maxed out.. To get more boost, wed need to lower compression, and wed need to source a new blower. And then, theres the matter of software, etc. With SCs being considered the lower cost option to Turbos, most folks wanting to get into that kind of money have gone turbo in the first place.. At least, thats my take on the main reasons.

[Jimmyz2]

Originally Posted by paul e

Wouldnt part of the issue be related to the impellor speed we develop on the Vortech V1 and V2 units? I forget the peak, but its somewhere around 50k rpms.. Most of us making 11 psi are spinning up pretty close to that. So, for all intents and purposes, we are pretty maxed out.. To get more boost, wed need to lower compression, and wed need to source a new blower. And then, theres the matter of software, etc. With SCs being considered the lower cost option to Turbos, most folks wanting to get into that kind of money have gone turbo in the first place.. At least, thats my take on the main reasons.

My take on on the main reasons are most people who apt for S/C do so because they want to go the S/C route.I have seen dyno graphs of some 'new' turbo kits and quite frankly they do not look that more impressive than 'old school' S/C kits.You want to move the torque curve around alittle?Fine.i have a sneeky feeling 'turbo' is the flavor of the month.

[CarlsbadCroak]

I think it's a mixed bag. Some folks (like myself) really really really like the way a centrifugal car drives, hard as that may be to swallow when you talk to the turbo guys.

For instance, had the AA turbo kit been the same price as the Dinan kit and CARB certified as well, I still would have went for the Dinan kit. I just plain don't like the way a single turbocharged car drives, no matter how well sorted out the kit is. The only way I'd consider a turbo is if it were in a good AWD platform, since AWD negates most of my issues with a turbo.

If I just wanted a RWD drag strip and dyno queen, and lived my life stoplight run to freeway run, the turbo might have been more my thing, because it rules in that environment. But I like to know that I can nail the throttle at the apex and have no surprises, I like to nail the throttle from a roll and not have traction events, I like to park the car and not worry about cooking bearings, and so on.

My goal for my car was to build something that can keep up with some other cars in my company parking lot, from a roll, on the track, and through the canyons, and build it for a whole lot less money. Those other cars include a 360 CS, a 996 Turbo, and a Viper GTS, and my little E36 hangs with all of them, without being a monster to drive, and I drive it every single day.

That's not to say I don't appreciate the technology and benefits of turbocharging over centrifugal supercharging. One suits how I like to drive and my modding goals, the other doesn't, to each his own.

I don't think turbo is the flavor of the month for BMW modders either, it's here to stay. The simple fact is, there are more turbo products on the market, from turbo manifolds to turbines to impellers to IC cores etc. And more ultimate horsepower to be had. You won't see a SC'd E36 in the 600 RWHP lists, ever. There's also more people with experience building turbos for other cars, I won't even get into the whole JDM tuner thing and what impact it has had making turbos more popular and the technology cheaper and well understood.

I just wish the turbo guys would stop bagging on us centri SC guys, it's not a religion, and we're not "stupid" for going the centri route.

[Jimmyz2]

If you don't think turbo is flavor of the month wait till the twinsrew hits the E36 market.OT- Mario Andretti blasted me around Infineon Raceway yesterday in a Audi S4 and that was quite an experience.Now I am definitely taking the ESPN Russell Racing 3 day course.

[mpowered325i]

Saturn ion redline boost 14 or 15 right from the factory, the reason its not done aftermarket so much is all of the extra drag/stress it causes on the crankshaft

[CarlsbadCroak]

Originally Posted by Jimmyz2

If you don't think turbo is flavor of the month wait till the twinsrew hits the E36 market.OT- Mario Andretti blasted me around Infineon Raceway yesterday in a Audi S4 and that was quite an experience.Now I am definitely taking the ESPN Russell Racing 3 day course.

Heh. Almost two years ago, when I decided to go FI, the TS was in the works. Glad I didn't wait, the TS is more like Fantasy of the Month so far.

And like you mentioned about turbos above, if you look at the Eurosport TS dyno charts on Dan's car, and compare them to mine or Paul's, you'll see that there's no big advantage.

RPM by RPM comparison of my dyno charts and Dan's car (in the parts of the power band that matter for performance driving) make me feel all warm and fuzzy. I make more HP, and similar levels of torque everywhere past 4k or so than the prototype TS. Below 4k, the TS is stronger torque-wise, but frankly, the only time I'm below 4k when driving the car hard is in 1st gear pulling out of the paddock or off the start line, and that's only for about 1 second.

Street driving in traffic or on the freeway I'm often below that, but the car is still plenty quick, and I didn't drop thousands into FI just to be able to pass better without a downshift or tow a boat uphill with ease.

The TS is nice, and the PD cars that I've driven feel good and the power is predictible and steady, but it's a lot of work and a packaging nightmare in the E36 engine bay, and a lot of money for no clear superiority over a charged cooled centri on the track. The biggest claim to fame the TS has is low RPM torque that stays flat throughout thanks to a flat boost curve. That's great for a tow vehicle, but it limits the amount of boost you can safely run on stock internals to right around 8psi.

A centrifugal SC's "peaky" power output that is often criticised is also a blessing. It allows you to run higher boost at high RPM where cyl pressure isn't as high (and where you'll be at on the track anyway), while maintaining safer amounts of boost at lower RPM and peak cyl pressure. And once again, in performance driving, you're not seeing low RPM once the car is rolling, some Auto-X courses being the exception.

So yeah, I take exception to the statement that's parroted a lot about a centrifugal supercharger having no business in an automotive application.

[DakarDave]

The whole idea behind forced induction is compressing air and forcing it into the engine's air intake. If I'm paying money for this, then I would like a technology that will allow me to force as much air as possible throughout as much of the RPM range as possible.

What technologies are available (not for just for bmws.. but in general)

1) PD Superchargers
2) CF Superchargers
3) Turbos

PD superchargers have the benefit of allowing you to build boost from idle (in theory) to redline. You'll have peak boost very early on.. and should be able to hold peak boost til redline

CF superchargers builds boost in exponential fashion. This means your peak boost is not made until redline. And at 1/2 redline you'll make the square root of your max boost. (i.e. if you make 8psi @ 6500.. you're boosting 2.8psi at 3250RPM).

All superchargers are belt driven.. and your boost is determined by pulleys. That is if you want to increase boost.. you need to manually swap pulleys.

Turbos on the other hand.. develop boost via exhaust gasses that have been expelled by the engine and are travelling through the exhaust manifold. There are no belts or pulleys or things like slipping belts.

Turbos also allow you to make full boost very early in the RPM range. Depending on turbo sizing for your application.. you can decide how you wish to develop boost and how early it comes on.

Also with the wastegate and electronic boost controllers (esp. closed loop boost controllers) you can control max boost at the touch of a button. With the right boost controller.. you can also control max boost for each gear... and in theory you could control boost as a function of RPM...

Lag and heat are the only real enemies of a turbo setup... You can minimize lag via smart turbo selection... and you can minimize heat via exhaust wraps and thermal insulation techniques.

I don't know about you.. but I think its clear that CF superchargers are the weakest form of Forced Induction.. because:

1) It isn't the most efficent (turbos are)
2) It doesn't offer the max boost potential (turbos do)
3) It can't develop full boost across a wide RPM band (PD superchargers win here)

That not saying that a CF supercharged car can't be FAST.. I had a CF supercharger kit and I loved it. With it my car was FAST and it drove well when the tuning was good.

I just think turbos or PD superchargers (I've driven some nice AMGs with PD superchargers) are superior. I now have a turbo and it feels nice.. I make full boost by 3500-4000RPM and it holds that boost to redline....

I can see someone wanting a PD supercharger over a turbo. And I can see why people would want a turbo over a PD supercharger.. But I can't see how, cost issues aside, would choose a CF supercharger over a PD or a turbo.

And this is coming from a former CF supercharger owner...

-Dave