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

[Solone]

The BOSS 335 guys on the Ford Forums whinge about their cars being heatsoaked. They are also factory engineered setups!!

Really boils down to what you want from your car. Each setup has their pro and cons.

[IJ.]

The BOSS 335 guys on the Ford Forums whinge about their cars being heatsoaked. They are also factory engineered setups!!

Really boils down to what you want from your car. Each setup has their pro and cons.

Non Intercooled....

What I "want" and have from a Blower is instant boost, 1600rpm it's making usable boost, don't know about you but my cars are drivers and it's nice having the response "right now" when I want it, if you were building aq 1/4 mile car or even a Circuit car that you can keep in it's powerband fine but a road car the PD wins hands down.

[XUV]

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.
.

we use to do that with NA big blocks , Have the WB's bonnet sitting up an inch near the windscreen .

[Jag530G]

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

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)

I think what is happening to IJ's Supra was the issue of pressure difference between under the bonnet and at the base of the windscreen, at low speeds the air pressure in the engine bay was greater than at the base of the windscreen, hence raising the rear edge of the bonnet worked at low speeds. But as the speed got much higher the pressure difference went the other way, the base of the windscreen was higher pressure than the engine bay, hence air wasn't sucked out of the engine bay and there wasn't any cooling benefit.

Cheers, Matthew

[IJ.]

I think what made it worse at high speed Matt was the High pressure at the base of the screen would impede the incoming air through the radiator, those cars were marginal for cooling at the best of times due to the tiny frontal area, if you left the undertray off you saw a 5c rise as the air took a shortcut under the radiator as the path of least resistance.

[Evman]

The BOSS 335 guys on the Ford Forums whinge about their cars being heatsoaked. They are also factory engineered setups!!

Really boils down to what you want from your car. Each setup has their pro and cons.

Factory engineered without any intercooling.

Heat is an issue in PD blowers. The intercoolers are often so small it's very difficult to get a large amount of heat out of the air. The main advantage that centri blowers have is they can run an air-air intercooler which is much more efficient. On a hot day with city driving my IAT will hover around 60degC (I have an M1900). My car is predominantly a daily driver. That means I'm not driving around the streets at 5000rpm and 9-10psi ready to go. I don't drive my car below 1500rpm, but in normal circumstances it wont see 3000rpm either. That's quite a short band to drive a car in, but when you're making a solid 6.5-7psi at 2500rpm you don't really need to go beyond 3000rpm because you're already making plenty of power (roughly 200rwhp at 2500rpm in my case). The other thing that needs pointing out is that the lower the rpm, the lower the effect of hot air. My mechanic gave me a dyno graph showing a cool power run vs a hot power run. Cool it made 513rwhp at peak, hot it made 490. At 3000rpm though the difference was 10rwhp (250 hot vs 260 cool). I'd never be able to pick 10hp.

[Jag530G]

I think what made it worse at high speed Matt was the High pressure at the base of the screen would impede the incoming air through the radiator, those cars were marginal for cooling at the best of times due to the tiny frontal area, if you left the undertray off you saw a 5c rise as the air took a shortcut under the radiator as the path of least resistance.

And the extra air going underneath would have caused more front end lift, so an undertray/splitter would serve two benefits, less front end lift and better cooling. Feistl's previous post he mentions he uses a V8 supercar front, so that should serve as a splitter. I'd say with Feistl's race-car, the air going in the front is all fine, it is getting it out that could be an issue and the VZ Monaro bonnet or raising the rear edge won't really help.....

Cheers, Matthew

[Jag530G]

This all reminds me of when Jaguar bought out the XKR supercharged V8 coupe. COmpared with the nn-supercharged XK8, the XKR had two rear facing louvre bonnet vents in the front corners of the bonnet to help with cooling. They had the added effect of reducing lift at the front so Jaguar had to fit a rear lip spoiler to balance out the lift over the front and rear of the car.

Goes to show that cooling and aerodynamics of a car really do go hand in hand and luckily tend to be mutually beneficial. If you get the airflow through the engine bay right it tends to reduce lift at the same time as cooling the car properly.

Cheers, Matthew

[IJ.]

Ideal situation would be a pair of large vents in the rear corners of the engine bay exiting out through louvres in the guards....

Not sure how practical this would be though.

[Jag530G]

Ideal situation would be a pair of large vents in the rear corners of the engine bay exiting out through louvres in the guards....

Not sure how practical this would be though.

Yes, could also pump the front guards out so that there is a nice gap between the rear edge of the guard and the front edge of the door and have the engine bay airflow vent out through this gap. Would look a bit like the Dodge Viper. IIRC there was a heavily modified V2/VZ Monaro in Street Machine which had the front guards were pumped out (had the bonus of fiting wider rubber).

Something else I remember is the Monaro 427, it had two vent holes in the bonnet in the front corners and a small splitter on an otherwise standard looking V2 Monaro front bar (not the HSV bar). The Monaro that was given to Peter Hanenburger on his retirement had the 427 splitter so he could hoon down the autobahns back home.

Cheers, Matthew

[Solone]

Watch This... in particular Look at the effect of heatsoak..

http://www.youtube.com/watch?v=qowkRc6qcZ8

[Solone]

Factory engineered without any intercooling.

Heat is an issue in PD blowers. The intercoolers are often so small it's very difficult to get a large amount of heat out of the air. The main advantage that centri blowers have is they can run an air-air intercooler which is much more efficient. On a hot day with city driving my IAT will hover around 60degC (I have an M1900). My car is predominantly a daily driver. That means I'm not driving around the streets at 5000rpm and 9-10psi ready to go. I don't drive my car below 1500rpm, but in normal circumstances it wont see 3000rpm either. That's quite a short band to drive a car in, but when you're making a solid 6.5-7psi at 2500rpm you don't really need to go beyond 3000rpm because you're already making plenty of power (roughly 200rwhp at 2500rpm in my case). The other thing that needs pointing out is that the lower the rpm, the lower the effect of hot air. My mechanic gave me a dyno graph showing a cool power run vs a hot power run. Cool it made 513rwhp at peak, hot it made 490. At 3000rpm though the difference was 10rwhp (250 hot vs 260 cool). I'd never be able to pick 10hp.

But what about if the Supercharger didnt generate this heat to start with? Your comparing hot air against hotter air. At same boost a centri with its cooler intake temps may have made 550rwhp.

[Evman]

Something else I remember is the Monaro 427, it had two vent holes in the bonnet in the front corners

They were intakes for the engine if memory serves me correctly

[Tre-Cool]

years ago, we dynoed my then vortech blown 5.7 vy ute. just running the belt on the blower cost over 40rwhp on a dyno run.

i.e ran the car with no boost without blower belt on and then with.

if the belt is still spinning the ****ing pulley it's taking power.

[steve_t]

years ago, we dynoed my then vortech blown 5.7 vy ute. just running the belt on the blower cost over 40rwhp on a dyno run.

i.e ran the car with no boost without blower belt on and then with.

if the belt is still spinning the ****ing pulley it's taking power.

40rwhp to run the belt?!!