View Full Version : Crank scraper cons?
cherrybombcivic
07-12-2004, 03:20 PM
http://www.crank-scrapers.com/products/honda.html
While looking at the link posted above, it seems like a no-brainer. However, if they were so efficient at freeing up horsepower, why didnt high performance vehicles(think k20a - b18c) come with these from the factory? Can anyone forsee any problems caused by using these/had actual experience using them? Thanks in advance.
The link doesn't work, you're not talking about knife edging your crank are you?
doctorstupid
07-12-2004, 03:38 PM
crank scrapers are awesome little contraptions. though to be fair, i would say that most of the power gains are exaggerated to sell them. in reality, the biggest gain to be had is keeping more oil in the sump. there are some power gains, however, that would depend on your engine size/speed/etc.
they're cheap, and can be installed in an afternoon. they've been around for decades, and in my book are worth it :)
edit: absolutely no cons that i am aware of, other than the work that goes into installing them, of course :)
doctorstupid
07-12-2004, 03:40 PM
stu-
a scraper is a plate that usually bolts into the main bolts, and is designed to stop the crank from slinging oil everywhere and creating extra resistance for itself in the crankcase.
Extra resistence? Does that matter to a crank style like Hondas, where it doesn't dip into the oil?
ryanman
07-12-2004, 03:52 PM
I use em in all my small block chevy's, never had a problem with them and they seem to work great.
doctorstupid
07-12-2004, 03:56 PM
well, no cranks are meant to dip in the oil. but oil comes from above as well as it drips out of the bearings. engines with oil squirters (DSM, VR-4, and many factory turbocharged cars) have a lot of oil in the air at any given moment. also when you turn/accelerate/stop quickly the oil moves around in the sump and the crank can catch it and sling it around. granted, oil pans are designed with baffles o prevent this, but most OEM oil pans are incapable of completely preventing it.
some big blocks (specifically 502) are known to create a vortex in the crankcase at high RPMs and actually pull oil out of the sump. as i understand it, it's just because of the massive size of the bottom end.
like i said before, the actual benefits and gains will vary depending on the engine size and speed. i doubt a small honda engine would have as much of an issue with it as a 502.
What kind of gains would one see with something like this though? Something like a CAI? I assume this is something like getting your crankshaft knife edged, something you do as a last effort to gain a extra horsepower?
doctorstupid
07-12-2004, 04:05 PM
it's similar to knofe-edging, but there are several major differences.
knife-edging not only reduces resistance on the crank, it also lightens the reciprocating assembly.
scrapers are designed to keep oil in the sump, and it just so happens that means less resistance on the crank.
Weston-work
07-12-2004, 04:18 PM
My main issue with them is: how do the piston rings get oil then? I don't know if oil squirters are really efficient at lubricating the rings, and many engines (ie mine) don't even have them.
chrisbarnett01
07-12-2004, 04:41 PM
Get a windage tray instead.
The reason many engines do not have these from the factory, is simple. Cost vs benefit.
1/2 hp for a stock engine is meaningless, especially when production engines vary as much as 10 hp easily.
No point in spending a large amount of money on research, tooling, materials, and labor, not to mention the additions to the assembly line. That's at least one extra assembly employee, a few in design, etc. Not worth the $$ for maybe 1 horsepower.
A windage tray is usually better in most situation. Slightly different function, but it works better to keep oil in the pan. Not as well as baffles though.
Aren't baffles just sections that are inside the pan to hold the oil, but don't interfere with the oil pick-up? Couldn't you weld some in yourself for next to nothing?
cherrybombcivic
07-12-2004, 05:04 PM
sorry i screwed up on the link. heres a working one..
http://www.crank-scrapers.com/ebay%20ads/honda.html
Weston-work
07-12-2004, 05:15 PM
sorry i screwed up on the link. heres a working one..
http://www.crank-scrapers.com/ebay%20ads/honda.html
Those pictures show exactly what I'm worried about... the piston rings don't get oil! I'll stick to the stock windage tray.
Bedlam
07-12-2004, 05:41 PM
sorry i screwed up on the link. heres a working one..
http://www.crank-scrapers.com/ebay%20ads/honda.html
I fixed it for you.. :p
-Bedlam
So how much are these? And Chris, you've got a PM.
cherrybombcivic
07-12-2004, 06:01 PM
Their $49 for the "buy it now" price.
Kevin Johnson
07-13-2004, 08:06 PM
My main issue with them is: how do the piston rings get oil then? I don't know if oil squirters are really efficient at lubricating the rings, and many engines (ie mine) don't even have them.
Hi,
I am the person who makes the scrapers. The cylinder walls still receive more than enough oil to lubricate the rings. It only takes a very small amount of oil to lubricate the cylinder walls and more than that is detrimental to performance in various ways -- this is one reason why most piston ring packages include an oil scraper ring. Most oil squirters are present to help cool the piston (oil serves multiple functions in an engine). It is important to return that heated oil to the sump as quickly as possible (hopefully an oil cooler is then present).
It is also important to remember that the spinning bottom end is a very complex shape and that only the borders of this shape pass by the "scraper" (it does not actually touch the crank but that is the name that people have been using for decades).
Kind regards,
Kevin Johnson
Kevin Johnson
07-13-2004, 08:22 PM
Get a windage tray instead.
The reason many engines do not have these from the factory, is simple. Cost vs benefit.
1/2 hp for a stock engine is meaningless, especially when production engines vary as much as 10 hp easily.
No point in spending a large amount of money on research, tooling, materials, and labor, not to mention the additions to the assembly line. That's at least one extra assembly employee, a few in design, etc. Not worth the $$ for maybe 1 horsepower.
A windage tray is usually better in most situation. Slightly different function, but it works better to keep oil in the pan. Not as well as baffles though.
Many, many stock engines do have them so many companies do feel they are worth the cost. Today we looked at the Ford 4.6 that a local shop was building up. The stock engine had at least three different crank scraper devices. Only one of these was located in the the stock windage tray (most windage trays do not have scraper devices built in -- the Honda engines that I have seen do not). The Nissan VG30 engine in the 300Zx has at least seven different crank scraper devices in its pan in addition to a windage tray, kick-out sump and separate baffling for the oil pump pickup. The SRT-4 from DaimlerChrysler comes stock with a crank scraper. BMW, DaimlerChrysler, Mazda, Ford and Nissan (among others) all have modern engines that use crank scraper technology.
I spoke with a retired engineer from Chrysler that worked on the 2.2 Shelby Charger engines in the mid 1980s. Chrysler and Mobil Oil did joint research on the windage losses in this engine. They found that with a crank scraper type windage tray they could recover 7hp at 6000 rpm and 9hp when using Mobil-1. These are fairly typical windage losses I am told. This sort of info is circulated within the car companies but rarely appears in published research available to the general public.
Kind regards,
Kevin Johnson
Kevin Johnson
09-13-2004, 01:45 AM
We just did roller-dyno work on the 993cc three-cylinder SOHC Metro engine.
This tiny engine already had a *full windage tray* and still picked up 3% hp (data ranged from 2.5% to 3.5% over four pulls). Power increased from roughly 2750rpm to 5300rpm.
Kind regards,
Kevin Johnson
Kevin Johnson
09-14-2004, 11:31 AM
I just heard back from a Honda race team that received some scrapers for testing about 7 months ago. The D16 scraper picked up from 1.5% to 3% hp depending on rpm. This is about the same result as the Metro scraper (the D16 has a girdle structure but hp still improved with the scraper).
Kind regards,
Kevin Johnson
Get a windage tray instead.
The reason many engines do not have these from the factory, is simple. Cost vs benefit.
1/2 hp for a stock engine is meaningless, especially when production engines vary as much as 10 hp easily.
No point in spending a large amount of money on research, tooling, materials, and labor, not to mention the additions to the assembly line. That's at least one extra assembly employee, a few in design, etc. Not worth the $$ for maybe 1 horsepower.
A windage tray is usually better in most situation. Slightly different function, but it works better to keep oil in the pan. Not as well as baffles though.
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