Gernby

I'm not very knowledgeable about FI, but isn't the roots style SC the solution for getting boost across the entire RPM range?

wicky

My research seems to indicate that the f20c spins a little too fast for a roots-type.... I could be wrong tho, I'm no expert.

Gernby

Doesn't Jackson Racing have a roots type for the H22? Doesn't the H22 have an 8K redline?

wicky

yeah, I've run into conflicting opinions about the roots type. It's been awhile since I looked into a roots solution, but I've ran into several references talking about that range being right about where it gets too fast for the roots. Again I'm no expert....... just regurgitating what I've read (actual info from eaton and whipple, not forum rumors ) If I come across this stuff I'll post it to share. I would think it would be just a matter of matching the pulleys so the max rpm of the SC (usually around 12k~14k for eaton) matches the 9k max of the f20.....

Greg888

the revs arent a problem on roots type blowers (the type-r will easily rev to 9k as well), powerband is. bell's book, supercharged, gives the formulas for boost with roots and centrifugal type superchargers. the roots type produces more boost than a centrifugal until about 4000 rpm. that's all well and good for low revving domestics, but an s2000 should only be concerned with its upper range power. the centrifugal takes over about 4k rpm, and more importantly has vastly superior adiabatic efficiency. even with an aftercooler, the roots is useless above 12psi. since the roots wont produce much power at 8k+, its uses are very limited for the s2000. it might make the car more driveable on the streets, but the added risk of detonation isnt worth it.

Jenner

"The roots type supercharger is known for its ability to produce large amounts of boost while spinning at very low speeds. On an automotive application, a roots type supercharger can often make it's full (peak) boost by 2000 engine rpm. This characteristic has contributed to its success and popularity on the top fuel racing circuit and has made it ideal for use on smaller 4 and 6 cylinder engines that traditionally struggle in the lower half of the rpm range (and is why Jackson Racing uses a roots type Eaton compressor). Another advantageous characteristic of the roots type supercharger is its simplicity of design. The roots type supercharger has very few moving parts and spins at low rpms, making it one of the more reliable and durable aupercharger designs.

The big disadvantage to the roots type supercharger is its thermal inefficiency - or its nature to produce high discharge temperatures - which robs power from the engine. With a roots type supercharger, an intercooler is almost always a necessity to bring the air charge temperatures down to an acceptable level. This poor thermal efficiency can be attributed to the fact that it has no internal compression (compression is done after the air leaves the discharge port). Additional heat is created by compressed (hot) air that leaks backwards past the rotors and heats up the temperature of the inlet charge.

Conclusion

The roots type supercharger is the oldest type of supercharger and still has its place in the automotive world on dragsters, smaller engines, and trucks - all of which are need power in the bottom half of the rpm range. Most major manufacturers have steered away from roots type superchargers likely because they create so much heat, even at low levels of boost. Like the screw-type supercharger, it is also difficult to create very high levels of boost with a roots type supercharger."

From:
http://www.superchargersonline.com/content.asp?ID=22

wicky

Thanks Jenner. I believe that's one of the documents I have printed out at home...... thermal inefficiancy.....d'oh!

Gernby

Thanks for clearing that up! Sorry for hijacking the thread.

itsallforyou

Jenner, sounds like you've got the "boost bug". I hope everything turns out OK.

What's your timeframe for building the internals???

Maca

Hi Jenner
I am also looking to alter timing on the Vortech box and have downloaded standard settings. I was surprised that it only pulled 3 degrees at top end as supplied. Can you let me know the final settings or pm me so I could get the file to look at for my set-up. I have similar set-up to you but am running 450 injectors - I also like the sound!!
MACA