bi22le
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| posted on 23/5/16 at 09:23 AM |
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Change all your oils, it will make your car go quicker!!
I am off this week revising for a big engineering exam I have next week.
I was working through a test paper about 40 mins ago and it had simulated figures for a "high performance engine". They looked round about
right.
Plugging through the numbers it turns out that the bearings on your crank spinning at just under 7000rpm take about 30bhp to overcome.
I dont know if that is new oil or old, I dont have enough familiarity with the numbers to know but, surly new oil can shave a bit of that off.
Transferring the saving straight to your tyres! (assuming no additional loss further down the chain)
Consider wheel bearings, diff and all other oliy bits. A good strip down and grease up could gain some healthy speed.
I often felt my car had more zip to it after an oil change, no I now know it was not a placebo effect.
If anyone is interested why dirty oil is bad, although the viscosity is often reduced in old oil( making it in theory easier for the engine) , its due
to its containments. The little bits of carbon and particles (that make it turn colour) add a wider range of particle sizes. Although viscosity of the
liquid is less, the dynamic viscosity increases, the oil and particles rub and flow over each other causing heat and friction. Plug this into
Petrov's equation and torque required to overcome the bearing increases.
Reading about oil types and SAE numbers was also interesting, but quite confusing.
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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Bluemoon
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| posted on 23/5/16 at 09:40 AM |
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But by how much 10% increase in friction would equate to 3hp... Not so bad, some real numbers needed for old oil..
Dan
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britishtrident
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| posted on 23/5/16 at 10:25 AM |
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The vast majority tne friction losses in an engine come from windage, pumping air and ring friction.
You can noticably power losses by running the crankcase at sub-atmospheric pressure a Formula Ford racer in the USA exploited a grey are in the regs
by fitting a venturi in the exhaust only to have it specifically banned PDQ.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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onenastyviper
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| posted on 23/5/16 at 11:15 AM |
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quote:
Originally posted by britishtrident
The vast majority tne friction losses in an engine come from windage, pumping air and ring friction.
You can noticably power losses by running the crankcase at sub-atmospheric pressure a Formula Ford racer in the USA exploited a grey are in the regs
by fitting a venturi in the exhaust only to have it specifically banned PDQ.
I like this - instead of turbo-charging, he had "suction-charging". Scrutineers must have wondered what's was up with the funny
crank case ventilation pipework going into the exhaust 
Perhaps an obvious question but doesn't the dry-sump system perform some/all of this functionality by maintaining a depression in the crankcase?
"If I knew what I was doing then it wouldn't be called research would it?...duh!"
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coyoteboy
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| posted on 23/5/16 at 12:00 PM |
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Crankcase vacuum systems have been around for donkeys years in competition across the world?
http://www.dragstuff.com/techarticles/vacuum-pumps.html
As for new oil vs old oil - if you stick to the maintenance regimes I suspect there's sweet chuff all difference in friction losses, in fact I
know for a fact that my old car oil is notably less viscous - not sure if that translates to oil friction loss directly though.
[Edited on 23/5/16 by coyoteboy]
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SJ
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| posted on 23/5/16 at 02:35 PM |
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When I was a kid my mate had a Suzuki A100, which went really well until he realised he had been running it with virtually no oil. Once topped up full
it was miles slower!
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Irony
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| posted on 23/5/16 at 09:39 PM |
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Ideally the Rover V8s crank case is run at negative pressure. This is not performance related through. It helps stop all the oil falling out.
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coyoteboy
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| posted on 23/5/16 at 09:46 PM |
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LOL
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mark chandler
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| posted on 23/5/16 at 10:21 PM |
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Have a read of performance tuning of 4 stroke engines by A Bell, he fits scrapers within a few thou of the crank webs which pull off the oil to
increase BHP at the crank, even without a dry sump you can make significant savings with care.
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Nickp
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| posted on 24/5/16 at 05:36 AM |
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It's easy to become too anal when it comes to lube
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