9 replies to this topic

[Andy500]

Hi Chaps.

My engine is currently being rebuilt using the MED 18cc FIS forged pistons, im having the crank hardened and the head reworked in order to get the compression down without running the decompression plate again. The guys at morspeed do the different size pulleys and Simon reckons that my engine should hapily take 18psi of boost which can be achieved by running the smaller pulley.
Has anyone else ever gone down this route and used the smaller pulleys and are there any other considerations i need to make?

[smith1380gt]

From what I've been told by Stuart Guerr at VMAX, anything over about 10 psi in a suck through configuration just generates extra heat, and no more power. At a certain point, the inefficiency of the supercharger gets in the way of making more power.

If it was set up as a blow thru with an intercooler, it could be done, but I'm not sure anyone has figured out how to fit it all under a roundnose bonnet.

[Turbo Phil]

Unfortunatley anything over about 10psi on the M45 is a waste of time, as already said, all you'll be doing is generating a lot of heat & no extra power gain.

[Andy500]

ok right then cheers for the info guys. Howcome the extra boost is just wasted? What happens to all that energy and how come it just gets converted to heat.
Cheers for the help guys.
Andy

[mini93]

when you compress air its heats up...which is why and how diesel engines work

with hot air it doesnt release as bigger bang when a spark is induced and combustion takes place

[Wil_h]

As said when you compress air it heats up (think of how a foot pump warms up as you pump). The efficiency rating (map) of the compressor tells you how much heat it generates dependent on flow and psi. This is where centrifugal turbo compressors score over Eaton-type SCs. An Eaton 45 is say 60% efficient compared to modern turbos that are nearly 80% efficient. This means you can run higher boost on a turbo.

[mini13]

adding to what Wil has said,

turbo's have an efficiancy "map" when they are operated on the correct size engine at the correct pressure they are efficient, but if you mismatch a turbo to an engine or run them at a boost pressure they are not eficient at they will heat up the air a lot!

the same applys with superchargers, but where as you can find turbos that will be efficient enough at 18psi superchargers (eaton ones anyway) just arn't efficient at this pressure.

[Andy500]

ah right that makes perfect sense now, cheers guys will ring morspeed then tomorrow.
Cheers
Andy

[Andy500]

ah right that makes perfect sense now, cheers guys will ring morspeed then tomorrow.
Cheers
Andy

I take it that some of this problem can be overcome with the use of an intercooler? I have no way of putting this sort of charge cooling device on mine but i could knock together a casing cooler for the charger, similar to the one that vmax do would this help at all or is high boost and an eaton m45 just goin to cause me trouble with high temps etc. Also what would be the optimal boost for an m45 in a suck hrough orientation.
Cheers
Andy

[fastcarl]

if you were to use a small shot of nitrous on this setup you really will see a big jump in power, its intercooling effect is excellent.


carl