Supercharger vs Turbocharger -- what would u do?

[stiddy]

Lag really isnt a big issue with these torquey 4.0L Inline 6's, I dont know why people are concerned about it to be honest.
Manual this Auto that. On these motors you can get away with any set up with any transmission. Especially if its a streeter which pretty much what this thread is about.
And as for the Twin Turbo set up, its alot of money for not much gain, if any.

[stiddy]

Bored and thought I'd add some extra info on superchargers. This is the path I want to take and have been spending alot of time researching Centrifugal superchargers.

Centrifugal superchargers aren't exactly new to the scene, they have been pumping out big numbers in Australia since the late 90's. They've been especially popular in the late model EFI cars, due to their ability to be fitted without disturbing the rest of the engine hardware, or poking stuff through the bonnet. No changers are necessary to the intake or exhaust manifolds unless you want to, and there is no messing about with the engine internals required - just bolt it on, a few tweaks to the ECU and its playtime.
Basically, they are like a mechanically driven turbocharger, but using a belt drive and an internal gearbox to get the impeller up to speed. As such, boost response is extremely predictable and is directly geared to engine revs.
But its NOT a linear relationship, if the supercharger makes 2.5psi at 2500rpm, its not going to make just 5psi at 5000rpm, they real figure would be 10psi or more. The higher you spin a Centrifugal blower, the more boost it makes, and so centrifugal superchargers are perfect for street cars.
Low boost at low rpm means that your less likely to turn the tyres, but theres plenty of power available up high when you put the boot in, and its easy to control. Obviously, you cant spin the blower too hard, because the bearings and impeller would fail.
Centrifugal blowers are also winners when it comes to adiabatic efficiency - that means they move air without adding too much heat. If you remember back to your high school days, you'll know that when you compress a gas, the temperature rises and that hot air isnt as dense as cool air, your car usually performs best in cool air. Any type of supercharging or turbocharging will heat the intake air - turbos run on exhaust gases, and Roots blowers use very tight tolerances, and are highly inefficient at moving air. Both act like heat sinks sitting in your engine bay. Sure, both make great power, but the average street engine runs on unleaded fuel, and you want to reduce the chances of detonation by limiting the intake temps.
Centrifugal blowers do this best..

[atec77]

Originally Posted by sly

Which blower are you running? Does it show a noticeable increase in torque at 2000rpm?

It's a centrifugal and it has boost from around 1500 rpm that has seat appeal if that helps , might be more in the set up but it shows about 2lb+ at 1200 rpm on the very suspect gauge .

[sly]

Nice summary Stiddy of what I've learned over the last 2 years. I've drifted the opposite way however. I have a Falcon for the lazy, long-stroke characteristics. If I wanted to spin an engine at high revs to make power I'd have a ricer. The issue for me is the overly-tall first 2 gears in the autobox. If I could buy an alternative gearset with 1st of about 3.00:1 and 2nd about 1.70:1 with 3rd and 4th unchanged, I'd have one. I reckon it'd be like an ar5ehole, everyone would have one!

What really opened my eyes was getting a 1.6 litre (base engine) auto Laser as a courtesy car while mine was being serviced, and finding the Laser much snappier to 60k's from a standing start than the Falc.

I could lower the final drive or fit a stally but I'm not too fussed on the compromises involved with either. I'd rather work with the engine's characteristics than against them, so I'm pretty much decided on going turbo. Speaking to a turbo & LPG guru with 20+ years experience today, he reckons intercooling isn't needed with 6psi and LPG & says he has customer cars running up to 15psi on LPG without intercooling. Seems a reasonable way to start (6 not 15!) and later add stronger internals, more boost and w2a intercooler plumbed through the LPG converter as an extra heat exchanger. Meanwhile, 6psi from under 2000rpm to redline sounds pretty appealing.

Just a little bit more research to do... when I start putting money into it I'll start a build thread.

[sly]

Originally Posted by atec77

It's a centrifugal and it has boost from around 1500 rpm that has seat appeal if that helps , might be more in the set up but it shows about 2lb+ at 1200 rpm on the very suspect gauge .

Which centrifugal unit though? Not the Gator???