omega0684
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| posted on 7/8/13 at 08:37 PM |
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Crank scrapers
Evening All,
I'd never heard of a crank scraper until this evening when I was reading through some posts on the turbo sport forums. What are people's
understanding around them? How do they benefit an engine? Is it worth fitting one? Would you see any minor power gains perhaps?
ATB
Alex
I love Pinto's, even if i did get mine from P&O!
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mark chandler
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| posted on 7/8/13 at 08:50 PM |
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The spinning crank attracts oil, not sure why as you would think it would be thrown off but it does and quite a bit.
So your engine is spinning extra weight, the crank scrapper is set very closely to the webs, it knocks off this additional unwanted oil allowing the
engine to spin more freely, so not any more BHP however less reciprocating weight.
If you make one then it must get within a mm or so of the webbing and be rigid, no good touching or you will get fillings, worth doing if you are very
competitive, for a track day toy not worth the effort.
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flak monkey
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| posted on 7/8/13 at 08:50 PM |
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Very minor gains, breaks the airflow around the crank and some of the losses from it sloshing oil everywhere. Talking fractions of a % though in
reality
I put one in in my SBC engine build
David
PS haven't you ditched that pinto yet and put a duratec in?  
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Smokey mow
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| posted on 7/8/13 at 09:29 PM |
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I run a crank scraper on my engine, a bit more detail about them and their benifits can be found here
http://www.crank-scrapers.com/What%20is%20a%20crank-scraper.html
Mine runs a close tollerance a required some bedding in of the teflon when new followed by an oil change.
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snapper
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| posted on 8/8/13 at 04:53 AM |
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Fitted one on a Pinto when rebuilding as it was cheap, easy to fit and will give a couple of bhp plus other benefits.
However as I run Cosworth rods with no oil spray holes ( you can notch the big end to throw oil up but I was not aware at the time) I had to fit a
Cosworth pick up and spray bar then modify an RS2000 sump which cost £100.
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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mcerd1
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| posted on 8/8/13 at 09:41 AM |
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got one for my pinto - might as well they don't cost much
quote:
Originally posted by snapper
However as I run Cosworth rods with no oil spray holes.....I had to fit a Cosworth pick up and spray bar....
ditto, only I couldn't find second hand ones at the time so I got a brand new pump and spray bar from cosworth (via graham goode) at ~£200 
the des hammill book gives guidance on drilling you own spray jets into the cossie rods - but me and the engine builder I use didn't fancy that
idea much ...
besides the cossie 2wd spray bar is better than drilling or notching the big ends anyway 
[Edited on 8/8/2013 by mcerd1]
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chillis
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| posted on 8/8/13 at 11:56 AM |
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Really depends how you intend to use the engine, unless your holding high revs for long periods, the only benefit it to improved fatigue life and a
small bhp gain under acceleration. If you hold high revs for lengthy periods then on a pinto ( most engines) its pretty much essential.
I fit them to all my engines together with a coarse mesh screen over the oil mass in the sump pan. The scraper keeps the oil off the rotating mass so
less energy is wasted during acceleration and the 'unbalanced' rotating mass is given an easier time.
2.1's suffer high blow-by causing oil to hang up in the heads which can lead to a shortage of oil so anything that gets oil returned to the sump
faster helps here as do extra external breather routes between the rocker cover and sump.
All these mods are relatively cheap and easy to do so its a low cost insurance to help look after your pinto, worthwhile give how much it costs to
build a decent 2.1 these days!
Never under estimate the ingenuity of an idiot!
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chillis
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| posted on 8/8/13 at 12:12 PM |
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quote:
Originally posted by mark chandler
The spinning crank attracts oil, not sure why as you would think it would be thrown off but it does and quite a bit.
So your engine is spinning extra weight, the crank scrapper is set very closely to the webs, it knocks off this additional unwanted oil allowing the
engine to spin more freely, so not any more BHP however less reciprocating weight.
If you make one then it must get within a mm or so of the webbing and be rigid, no good touching or you will get fillings, worth doing if you are very
competitive, for a track day toy not worth the effort.
The spinning crank doesn't attract oil, the oil is being pumped into it, this oil then flows out from the bearing sides. Viscous liquids will
always cling to a rotating assembly until the fluid mass and centrifugal forces throw it off. Unfortunately the glob of oil then splashes into the
mass of oil in the oil pan and can splash back up into the rotating mass!
Using a coarse mesh screen over the oil mass stops the 'splash' and the scraper keeps the oil mass on the rotating assembly to a minimum.
Under transient conditions it will show a little extra power as less is used to accelerate the rotating mass.
As said elsewhere these mods are cheap and easy to do so worth the effort IMHO.
Never under estimate the ingenuity of an idiot!
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