Gregsgto2,
why are you posting a ebay listing for some pontiac heads
in this topic?
Quote:
"This centrifugal compressor topic has me curious. If you have a minute or three I was wondering if you could elucidate myself on some of the engineering trad-offs.
As I understand it the amount of air it supplies is a function of many variables such as blade pitch, RPM, inlet and outlet diameters, pressure differential, air density, differential temperature, parasitic power and so on. Given that are there tables or plots that show airflow as a function of the variables I mentioned?"
Specification guide is shown here:
http://www.vortechsuperchargers.com/...ation%20Guides
Compressor maps are shown here:
http://www.vortechsuperchargers.com/...pressor%20Maps
Quote:
"I had read somewhere that centrifical compressors don't do much until you are in the upper ranges of RPM. Is this true? Or is it linear with RPM?"
Not linear. If you had 16 psi of boost pressure on your pontiac at 6000 rpm you will have 1/4 the boost or 4 psi at 3000 rpm. 4 psi at 3000 rpm is a lot more power vs a NA engine at the same rpm where an engine might have 75% volumetric efficiency.
Quote:
"Is it possible to provide so much boost that the mixture ignites from compression regardless of the presents of spark?"
If you had an engine with a lot of boost 30 psi, high compression, and low octane fuel you would suffer from very high cylinder pressures and hurt the engine parts. With a compression ratio in the 8.0 to 9.0 range and 12 to
15 psi of boost you will have plenty of power and should be able to run on good fuel without issues if you have the right camshaft event timing.
Quote:
"Is the one you are talking about a "blow through" type?"
Yes.
"If so how do you keep the air pressure from pushing gas back out of the carb jets? How do you maintain carb calibration?"
The fuel bowl is vented to the airhorn, same as the carb venturi. Pressures are balanced under boost same as a na carb. Pressure in the bowl is higher with boost therefore you need to have a fuel pressure regulator that has a boost reference line to raise the fuel pressure to the carb under boost. Stock engine you have say 6 psi in the line to the bowl. With 5 psi of boost the bowl will still see 6 psi after the needle and seat you now the boost fuel pressure regulator will raise the fuel line pressure to 11 psi. The fuel pump must be a high quality fuel pump designed for boost. For 6-8 psi boost a boost referenced mechanical fuel pump MIGHT work but much better to use a good electrical fuel pump.
Hey, I'm just a curious guy. Thanks for a great topic!
No problem.
Tom V.