I was at an SAE meeting last night , and they had a Honda representative discussing their new hybrids. Among the many things he talked about was the reduction of frictional losses in the motor. One method they use is dimpling the skirts of the pistons for better oil retention which allows them to run a very low vicscocity oil ( 0w30 or something similar). The other major method was offsetting the head and cylinders from the crankshaft so that the rod and piston were perpendicular coming down on the power stroke which reduces side loads and frictional loss during the power stroke. I was talking with somebody after the meeting, and he mentioned that it was common in the racing world to use offset piston pins to the same effect. My questions are, have any of you used or seen either of these methods used? How affective is it? Is it something that could be applied to the Lt-1, Ls-1 etc. ?

Thanks!

Don

 

Off and on GM V8's have used offset piston pins (about 1/16) to minimize piston 'slap' (and perhaps friction reduction as a bonus). All thru the 60's at Pontiac at least. I believe Honda may be talking about more offset. Did they say how much? 5mm maybe?

Remember these (hybrid) guys are going for the last little bit. They've already reduced bearing size and probably ring width, piston skirt length, and maybe stroke, as well as keeping the rpm down. All of these things would help our SBC, as Winston Cup guys well know. Roller lifters and full roller rockers also help.

There's no free lunch: smaller bearings mean more loading and less crankshaft strength, so you make it up with stronger parts.
If you are building a restrictor plate Cup engine, and the amount of air which can get in to the engine is limited, every friction hp you can eliminate is one more at the flywheel. My guess is that Daytona/Talladega engines are at the minimum displacement limits, and at the maximum bore size to get the shortest stroke so there is less friction hp, or the same friction a few hundred rpm higher which gives more hp if the torque output is the same. Did anybody see any engine telmetry from DEI cars at Daytona? My guess is they turn a little tighter than some of the others.

Bottom line for LT1, LS1 SBC is you could spend a ton of money doing all these things and pick up maybe 10 hp at 6500. It's not cost-effective for street use, IMO.

It is a good topic Don2.

My $.02

 

The cheapest way to go about lessening frictional losses is to use a thin (1-1.2mm) ring-set and low tension oil ring. Then you need a vacuum pump to seal everything up. It is worth some power though as the many dyno tests I've seen would indicate.
Other than that, keep the oil temps up (use synth) ~220 deg..... the gains are small though.

-Mindgame

 

Would you run a crank driven or elcectric vac. pump for street use? I noticed Moroso had a new electric vacuum pump for SEMA.

 

The piston skirt dimpleing is interesting.

The oil control, can also be done with certain hone/etching in the cylinder bores. That along with coated piston skirts would help. The right hone would be good for street use but the coated skirts are not really cost effective on a street engine.

A friction reduction setup is basicly alot of things together. Small rings, small bearings, roller cam bearings, oil control, bore/stroke combo even the off set pin that you mentioned. It's a system, and as a group pays off but is never very cheap.

A electric driven vaccum pump is a good idea. How long is the service life on that? Hopefully close to the service life on a elec. H2O pump.

Bret

 

i've been thinking about a 'raised crank' type of scenario, and how that would affect the l/s of an engine...... i don't have any sort of modeling software, and my mechanical drawing skills are not nearly accurate enough to show who changes where with the what now, but it seems to me that raising/lowering the mains in relation to the cylinder would let you find a better compromise between piston side-loading/drawing force on intake port/rod bearing speed.

acourse, i'm just a dumb kid, so maybe i'm getting way ahead of myself..... this all assumes you have enough cam clearance to get the right amount of raise...... maybe the SStrokes and/or Mr. Horsepower have some details?

 

You can only use roller bearings like in acam on a place where you can slip the journal into them. On a take apart crank like in a motorcylce you can use roller bearings on the rod and main journals, you can't on a V8 crank because it would not be strong enough if you had to take it apart.

2 stroke motor cycle racing engines also need the roller bearing because it is difficult to oil a 2 stroke engine well, because you mainly oil it with the fuel. Roller Bearings solve that problem and they are not a ton better than a conventional bearing.

Tim S,

Hmmm, that's something we will have to think about. Esentially you are talking about changing the angle of the V in the block, which in F1 is tested alot on V10's. 72-110 deg ( I think Renault did the 110) engines rather than the tradtional 90deg on V8's. Obviously when you do that a custom crank is needed. The engine also needs to have the V angle divisible by 720 and work with the fireing order of the cylinders to balance it out. Hence a V8 is 180 or 90. A 110 deg V8 would poduce a horrible imbalance in the engine. The main reason they change the V angle is to get a lower center of gravity and a smaller engine package. Different V angles can also change alot of things with the intake manifold geometry and such.

Let me get back to you on this one. Chucks comments on this would be interesting.

Bret

 

ahhhh...... i get what you're saying. basically, you'd need a ~95* crank to put in the 90* block, so all you'd really get is a ~95* engine with cocked cylinder bores. right?

wait, no..... hang on...... still thinking.........

 

http://www.e31.net/engines_e.html

ok, found out why i'm wrong always nice to know there's a reason! SStrokerAce nailed it, custom crank. i just kept trying to figure out how to get 4 crank throws 95* apart...... DUH.

a change like that would need split crank pins, like a V6. it all makes sense to me now. so it comes down to paying $4,000 for a custom crankshaft.......

well, that's a good enough reason for me to forget about it, but i wonder if there would be any actual benefit?

 

actually, it's been said that NASCAR engines use roller cam bearings, but it's not that they're any more efficient. it's to reduce the amount of oil necessary in the engine.

 

If Moroso makes an electric that'd be the way to go. The crank driven ones do cost some power so that has to factor into the actual gains.
With the right ring setup, I'd go that way if getting every last bit of horsepower was the priority.

-Mindgame

 

Yep, roller bearings only need splash oiling to do their thing. Good for restricted oil flow.

-Mindgame

 

2-strokes don't have pressure oiling in the crankcase, so plain bearings (like in most 4-stroke car engines) won't work. Many/most 4-stroke "lawnmower" engines have plain bearings, or no real bearings on the rods; they just use the aluminum rod as a bearing. Lubrication is generally splash, with a dipper on the rod cap which churns up the oil from the sump. They use a ball bearings on the crank because they can fit over the ends of the crank. Again, usually no pressure oiling.

The plain bearings used in automobile engines have many advantages:

They offer very low friction for the loads they can support. Metal doesn't actually touch metal. There is a thin film (actually a wedge) of oil which supports the load and sorta spreads the load out over about half the bearing surface. The pressure in that wedge of oil can be very high. A roller or ball bearing has more point loading with rolling metal to metal contact.

Some very precise grinders use a similar type of plain bearing in the grinding wheel spindle because if offers a smoother running spindle. My guess is that the best, but maybe not newest, cam grinders have plain bearing spindles. The spindle ball bearings that run as smoothly as plain bearing spindles are very expensive, and often used in matched sets.

Obviously, the smaller diameter the plain bearing the slower the surface speed of the journal across the bearing, so less friction. The down side is that smaller bearings have less area to spread out the load, and the crank is less strong because there is less "overlap" between the main and rod journals.

No free lunches.

 

will a 160 stat effect oil temps-
just wondering if the cooler coolant will have any significant effects on oil temp/thickness

 

For the 2.2L Ecotech GM uses knife-edged crank counterweights and a powdercoated crank to reduce oil cling. The GM sales guy I talked to at SEMA in '01 also said that the knife-edged counterwights improve the crank's aerodynamics, although I'm not sure if I buy that as being a significant improvement.

I know they aren't really frictional losses. I'm just throwing my 2 cents in.

-Chris