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Re: RX075's s3 AUS spec Tuff street car build.
Posted: Fri Dec 02, 2016 4:31 pm
by spirit r
great pictures!
Do you use a Main Drive Pulley designed for high performance/RPM street and moderate racing use, slowing the water pump and alternator 13-15 %, thereby reducing cavitation?
Btw i like your process very impressive!
Thomas
Re: RX075's s3 AUS spec Tuff street car build.
Posted: Fri Dec 02, 2016 8:04 pm
by codge
spirit r wrote:
Do you use a Main Drive Pulley designed for high performance/RPM street and moderate racing use, slowing the water pump and alternator 13-15 %, thereby reducing cavitation?
Thomas
Wow Thomas.....that's pretty good science.
Re: RX075's s3 AUS spec Tuff street car build.
Posted: Fri Dec 02, 2016 9:47 pm
by kenwhiteside
I thought the reason for a smaller pulley was to reduce the power required to drive the ancillaries. If running at high rpm there is no need for the same drive ratio to keep things running on at low speed. If there is cavitation at high pump speed this is a different issue.
Re: RX075's s3 AUS spec Tuff street car build.
Posted: Fri Dec 02, 2016 11:58 pm
by KiwiDave
Yes, that's my understanding as well. Reducing the ancillary power drain was the main aim although cavitation reduction is a secondary benefit. I'm not sure how much of an issue cavitation is for race engines as things like water pumps would be changed out on a regular basis. Cavitation gets all complicated after a while with water temp vs pressure vs impeller speed and angle blah. blah, blah. Really interesting if you wanna get into it.
Re: RX075's s3 AUS spec Tuff street car build.
Posted: Sat Dec 03, 2016 5:50 am
by RX075
I will just see how she runs and go from there, if I have any issues it can always be changed at a later date. I just want to see it done and christmas will slow me down again.
Re: RX075's s3 AUS spec Tuff street car build.
Posted: Sat Dec 03, 2016 7:05 am
by spirit r
RX075 wrote:I will just see how she runs and go from there, if I have any issues it can always be changed at a later date. I just want to see it done and christmas will slow me down again.
The use of the underdrive pulley depends how to increase the engine's RPM range substantially. Test the engine RPM range first is a good reason.
Re: RX075's s3 AUS spec Tuff street car build.
Posted: Sat Dec 03, 2016 10:21 pm
by kenwhiteside
The bigger problem with cavitation is not the damage done to the water pump impeller by the implosion of bubbles but more the collapse of the bulk flow itself that can lead to overheating. As spiritR suggests if you are increasing the engine speed significantly you are operating the pump outside its design range, perhaps into cavitation, so the underdrive pulley is probably a required addition.