Twin turbo vs Supercharging LS motors? What's the vibe nowadays?

[Evman]

SVE have this style which should work perfectly to draw extra air out

[feistl]

The other "mod" i had done was to raise the rear of the bonnet slightly by putting a couple of washers between the bonnet and hinge mounts, coupled with removing the rubber strip means there is a reasonably large gap where air can be vented. I tried to do some measurements but there was far too many variables. I can say though that the windscreen was always warm to the touch after driving at lowish speeds (So i assume hot air was escaping out and going over the window.

Again i wish i could test this thoroughly but its hard to get a controlled environment.

EDIT - I also run the VX Supercar front bumper when on the track, so it has a pretty good air dam effect and does get a lot more air through the radiators compared to the standard front bar. (Although it looks pretty tacky it one of the few times a "body kit" has been fitted for performance reasons alone).

[Jag530G]

SVE have this style which should work perfectly to draw extra air out

Yep, that looks perfect. @Feistl, you might want to look at a Monaro bonnet style version of the SVE style, I think you'll find the VZ Monaro bonnet to be a complete waste of time. I know people like the look of the VZ Monaro scoops. Holden developed them for the Pontiac GTO purely for styling reasons to tie in with the old GTO. In terms of engineering purpose the Monaro scoops are a complete wank really.

Cheers, Matthew

[IJ.]

The other "mod" i had done was to raise the rear of the bonnet slightly by putting a couple of washers between the bonnet and hinge mounts, coupled with removing the rubber strip means there is a reasonably large gap where air can be vented. I tried to do some measurements but there was far too many variables. I can say though that the windscreen was always warm to the touch after driving at lowish speeds (So i assume hot air was escaping out and going over the window.

Again i wish i could test this thoroughly but its hard to get a controlled environment.

Tried this on the Supra, it helped at low speeds but hurt at high speeds.

[Jag530G]

The other "mod" i had done was to raise the rear of the bonnet slightly by putting a couple of washers between the bonnet and hinge mounts, coupled with removing the rubber strip means there is a reasonably large gap where air can be vented. I tried to do some measurements but there was far too many variables. I can say though that the windscreen was always warm to the touch after driving at lowish speeds (So i assume hot air was escaping out and going over the window.

Again i wish i could test this thoroughly but its hard to get a controlled environment.

EDIT - I also run the VX Supercar front bumper when on the track, so it has a pretty good air dam effect and does get a lot more air through the radiators compared to the standard front bar. (Although it looks pretty tacky it one of the few times a "body kit" has been fitted for performance reasons alone).

The problem with raising the rear edge of the bonnet is that is in a high pressure area, it will actually draw air into the engine bay and stop air getting out. (thats why old Torana SLRs and VH Group 3s had rear facing scoop, it was the air intake for the engine, not as a means to exhaust hot air from the engine bay).

[Evman]

Can be seen here. The base of the windscreen gets as much pressure as the front of the car. I have no idea what speed this test was done at but I assume 60km/h or so. Also, I have no idea what pressure the areas are. Even the "high pressure" areas could be relatively low for all I know (but I'd assume not, especially at speed)

[Solone]

I disagree with a few on that list... what's your source or is it just your way of thinking?

As said a few times in this thread, the newer PD blowers will bypass at low throttle, Magnuson were claiming 1/3 of a hp loss when it's doing this at 60MPH. You'd be hard pressed to notice anything better than that from the "seat of the pants" dyno.

Low throttle (off boost), I didn't notice any change in fuel economy before and after fitting my blower. On boost fuel efficiency will depend entirely on the tune and how much boost is going in. If you're putting more air in, you generally need more fuel. You can't say a PD blower is less efficient just because its making more boost... it's also making more torque/power in that case!

Just because there is a valve dont mean the blower isnt making heat and costing power. The engine is still driving the blower at full tilt but the benfits are being blown out the back door. So the PD blower with a valve will have a heavy cost of power but not making any power. Also its just recirculating engine heat if not on boost. If its a top mount blower it has to be heatsoaked as the heat from the engine rises straight into it. If its a twin screw blower then its always generating heat whether its valve is open or not as its internally compressing air. The eaton type by design generates so much heat when its on boost and when not on boost it recirculating engine heat.

The centifugal by design isnt costing much power as its not spinning hard down low and it free spins. Doesnt exchange heat with the motor, only up in rpm is it costing power to make power. The PD system is heavily taxing the motor of power but for most of the driving its being vented out the back door?

[IJ.]

Just because there is a valve dont mean the blower isnt making heat and costing power. The engine is still driving the blower at full tilt but the benfits are being blown out the back door. So the PD blower with a valve will have a heavy cost of power but not making any power. Also its just recirculating engine heat if not on boost. If its a top mount blower it has to be heatsoaked as the heat from the engine rises straight into it. If its a twin screw blower then its always generating heat whether its valve is open or not as its internally compressing air. The eaton type by design generates so much heat when its on boost and when not on boost it recirculating engine heat.

The centifugal by design isnt costing much power as its not spinning hard down low and it free spins. Doesnt exchange heat with the motor, only up in rpm is it costing power to make power. The PD system is heavily taxing the motor of power but for most of the driving its being vented out the back door?

Are you trying to tell us with the gear ratio needed to spin up a Centri that at low engine speeds there's no load/parasitic drag?

I don't know how accurate the Magnusson claim is but 1/3 of a HP at 100 Kmh is nothing.

[Solone]

Are you trying to tell us with the gear ratio needed to spin up a Centri that at low engine speeds there's no load/parasitic drag?

I don't know how accurate the Magnusson claim is but 1/3 of a HP at 100 Kmh is nothing.

Of course there is still some loss but Id argue much less than a PD blower. Not only less Parasitic loss but much lower IATs as well.

There was a test done between a roots type supercharger (TVS is a roots type) and Centrifugal....

http://www.lextreme.com/icvsnic.htm

[white lie]

I don't really see what the big issue is with 'costing power' if you're just cruising down the highway... It may effect the fuel efficiency but power wise, it shouldn't be an issue as you're not using much.

Yes, it will generate heat but this doesn't necessarily effect the intake temps when the car is moving. If its a dyno queen, then you may have a valid case but there are still ways around that.

[IJ.]

At 100 kmh/ roughly 2000rpm in most cars your Centri is spinning at 14800 Rpm, can't see the load would be so much lower than a PD in bypass...

By all means buy one and let us know how it works for you, keep in mind there's a LOT of sales hype attached to these things.

[Solone]

At 100 kmh/ roughly 2000rpm in most cars your Centri is spinning at 14800 Rpm, can't see the load would be so much lower than a PD in bypass...

By all means buy one and let us know how it works for you, keep in mind there's a LOT of sales hype attached to these things.

The centris shortcoming is its lack of boost down low but its offset by the less "cost of power" of running it down low as well. Its just a fact that Centris dont cost as much power as PD units. Thats one of the reasons why per pound of boost they are superior. (and the less heat)

[Solone]

read this!!

http://www.lextreme.com/icvsnic.htm

[white lie]

Of course there is still some loss but Id argue much less than a PD blower. Not only less Parasitic loss but much lower IATs as well.

There was a test done between a roots type supercharger (TVS is a roots type) and Centrifugal....

http://www.lextreme.com/icvsnic.htm

I don't quite see how this link is valid to your argument.
It's essentially comparing a non intercooled, thermally inefficient Roots blower to an intercooled centrifugal.
Firstly, the TVS are 76% thermally efficient, which is leaps and bounds ahead of what they're using in this test. And secondly, they are of course intercooled.

[IJ.]

read this!!

http://www.lextreme.com/icvsnic.htm

All from the Corky Bell book that's 20 years out of date.....