TIMEBANDIT

Hey guys after reading the whole Bore verses stroke thread I realized that at higher rpms a huge amount of hp is lost due to friction. I was wondering what are the methods for the reduction of friction in an internal combustion engine and how much HP/tq could you gain with each modification and lets think out of the box. Using a standard 400 chevy small block. Keep in mind we would like to keep the motor semi reliable.

To my recollection here are a few.

1. Roller bearings
2. low tension rings
3. dry sump oiling system
5. teflon coated piston skirts

can anyone add to this and maybe someone could come up with some percentages of savings from each
Thanks

OldSStroker

The quick and dirty answer is smaller main and rod bearings. There was some discussion on roller bearings; they aren't that much different in friction from plain bearings as we use now. Smaller bearings usually mean you need stronger parts, so either reliability or cost suffers.

Roller lifters and full roller rockers are worth a few %, but additional potential power output is more useful and cost effective reason to use them.

Oil control is important, sure, but dry sump isn't the only way.
Synthetic oil of lowest usable viscosity also helps a bit, and is relatively cheap.

Coatings on everything might be a few %, with nearly as much coming from oil shedding as reducing rubbing friction.

Of course, big bore, short stroke is the way to low friction for a given displacement and hp level. Combined with other things, you might be up over 10% in a good example. If you are not rules limited, it's probably easier/cheaper to get that (maybe) 10% hp with better airflow rather than a redesign and bespoke parts just to reduce bearing sizes, IMO.

Additional thoughts to increase flywheel (brake) hp:

efficient accessory drives, like multirib belts, or directly driven pumps.

no mechanical drive distributor

electric water pumps, especially for drag cars.

possible belt drive for cam vs. chain. (maybe/maybe not)

My $.02

TreySpeed

Believe it or not-
brakes rubbing against the rotor can cause some serious performance issues. Ask anyone with a new Lincoln LS how they like their rear brakes.

Maybe get some used pads or something
I don’t have much experience with drum brakes, but I think you can adjust them so that your pedal feel sucks and they aren't rubbing at all.

DarthIROC

Floating pins free up a little power

TIMEBANDIT

OldSStroker say we confine this to best-case scenario, which would be a big bore short stroke motor.

Items that can be used without major modifications and are commonly used today

1. Low tension rings
2. Teflon coated piston skirts
3. Roller lifters
4. Roller Rockers
5. Floating wrist pins
6. Lighter Viscosity oil
7. Oil Scraper
8. Windage tray
9. Better accessory Drives
10. Electric Water Pump
11. Remove the distributor drive

If we look at all of the above incorporated into a v8 engine maybe a small block 400. What would be the percent reduction in friction and the additional hp gain assuming you have a 400 hp motor at 6000 rpms prior to the modifications.

Items needing major modifications

1. Dry sump oiling system
2. Smaller Bearing surfaces Which requires smaller lighter stronger parts which is how nascar does it
3. Roller bearings

Are you sure about the roller bearings???? I believe you stated that roller bearings provided little if any reduction in friction. I have a 300hp Mercury Promax 2 stroke Outboard and from time to time we do some machine work on these 6 cylinder 3 liter blocks. As a result of this I have had to speak to Mercury Performance out of Florida from time to time. An Engineer there told me that because of the environmental laws they have been working on some 4-stroke versions of this motor. They took the opportunity to build 8 test blocks 4 with all roller bearings assemblies and 4 with standard automotive bearings. He stated it took an average of 51ft/lbs to turn the standard bearing assemblies over and 28ft/lbs to turn the roller bearing assemblies over. He also stated that with the same cam, heads, intake, and fuel system the standard bearing motors made an average of 277 hp at 6200 rpm. And the roller bearing motors made an average of 301hp at 6200 rpm. Basically 24 more horsepower and he said the motors revved and responded to acceleration cues much quicker. He also stated that there was probably only about 200 dollars difference in cost to build the engines. This suggests to me at that there can be a fairly large gain from an all roller bearings engine.
Also why is it that a lot of the more exotic race cars use roller bearing engines if this provides no added benefit.

dano73327

The smaller main and rod journals deffinitely contribute to friction reduction. I dont know how exactly you would convert a 400 chevy to a full roller bearing setup. Its funny that you mention that because we just had a discussion about that at school today.
I would imagine though that the cost of such a project would be prohibitive. I also think that the added weight of caged needle bearing assemblies would overshadow the friction reduction.

Roller rockers and lifters both reduce friction slightly and reduce the oil temperature somewhat. Floating pins can reduce the amount of pin rotation in the piston bore by allowing it to rotate freely through the rod and piston assembly.

Control of windage with tighter bearing clearances, and better parts can help.
Windage trays, screens, and crank scrapers can make a difference on some engines. That just requires testing to see if a difference was made.

Lighter viscosity synthetic oil can deffinitely make a difference.

Any time you can lower parasitic losses from accessory drives you can free up some power.

As far as coatings go we dont really concern ourselves with coating the parts. If we have some extra time or if a customer wants it done we will coat some of the parts. We have had some bearings coated mainly to take up some clearance if we thought bearing clearance was excessive.

The biggest gain from friction seems to come from the ring package. The rings contribute to upwards of 60% of the friction in the engine. And of that 60% the oil scrapers and expander make up 75%. We have seen pretty large gains from using thinner, low tension ring packages and using a specific surface finish in the bores. With one of our circle track engines I was able to turn the engine over with one hand gripping the pulley bolts near the center of the balancer. This was with all the pistons and rings installed. That amount of friction reduction could be worth as much as 20hp, maybe more on some combinations compared to standard tension rings.

Of course, big bore, short stroke is the way to low friction for a given displacement and hp level. Combined with other things, you might be up over 10% in a good example. If you are not rules limited, it's probably easier/cheaper to get that (maybe) 10% hp with better airflow rather than a redesign and bespoke parts just to reduce bearing sizes, IMO.

Big bore and short stroke is the way to low friction for a given displacement and RPM. The problem is that as stroke is reduced the rpm necessary to reach your power goals goes higher and higher. Though since hp is airflow limited, for a given head on a given bore the longer the stroke the lower the rpm where you reach the limiting piston speed of the head. In this way the longer stroke combined with that particular bore/head combo has the potential to make just as much power if not more with less friction and inertial loads along with increased durability.

OldSStroker

Dan,

I agree mostly about ring friction. Bore roundness and the correct surface finish, the % plateau, etc. primarily enhance sealing, and not friction, IMO. Thin, low tension rings contribute to lowering friction. I haven't heard much about 75% of the ring drag coming from the oil scrapers and expander. Please tell more bout that.

Is it really hp that is limited by airflow or torque? If you can produce the same amount of torque, based on airflow, at a higher rpm, by definition of hp, you get more. True, you have more friction losses at the higher rpm, but if the torque & hp gain exceed the additional friction losses, keep going until they don't. Diminishing returns applies again.

I too like big displacement street engines to achieve torque/power/cost goals. But, when winning a race is critical, and rules limit displacement, but not cost, I don't see the lower rpm/longer stroke engines winning. I believe I understand your point, but I don't see the state-of-the-art racing classes doing this. Just the opposite. Why is that, do you think?

What I do see is rpm at the highest point that the limiting port velocity will support (with durabilty factored in, of course), with big bore/short stroke configurations. Even in restricted Cup engines, I don't believe the bore/stroke change much (from unrestricted), but the rpm drops maybe 1500+ due to airflow limits. I notice, via TV telemetry, that Cup "plate" engine speeds seem to rise a tad each season.

IMO, Cup and F1 engines have seen most of their recent hp gains come from producing approximately the same indicated torque, but at fractionally higher rpm. Both of those series seem to have solved the valvetrain problems for 9000+ and 18000++ rpms respectively. As far as Pro Stock, I believe they may have valvetrain (springs?) limiting their max rpm, not airflow. A couple of years ago, a well-know PS engine builder discussed that in an engine conference. Valve lifts near/over 1 inch were mentioned, with rpm near/over 10K. Spring life was discussed in seconds, not minutes or hours. I suspect they still are similarly limited.

Keep up the good posts.

My highly-opinionated $.02.

OldSStroker

I really don't have the last word on all roller bearing 4-stroke engines, because I've only been involved with old 2-strokes. A few thoughts, however:

1. Plain bearings don't involve metal-to-metal contact when the engine is running. There is a wedge of oil supporting the bearing journal and keeping it away from the race. If this oil film breaks down, the engine goes toes up.

2. When static, the plain bearing engine does have metal-to-metal contact (hopefully with some assembly lube or oil on the bearings). Yes, it can take quite a bit of torque to turn over the engine. I would suggest that 51 lb-ft might be a lot for a 3L 6-cyl engine.

3. Ask the engineer about friction hp they measured by motoring the plain and roller bearing engines after the rings seated, assuming all else was equal in the engine.

4. Because of the way they work, plain bearings don't require the journals to be hardened. Roller bearing rollers, as well as inner and outer races are generally hardened to Rc 60 +/- a couple of points, because in roller (or ball) bearings, there is metal-to-metal contact between the races and the rollers. This is approximately line contact, and causes very high unit stress, and requires good lubrication. If you hardened the crank journals to Rc 60 for at least .050 depth required to keep the case from cracking, I don't think the crank would have the kind of fatigue life it now has. Surface hardening or nitriding crank journals is a very shallow case, a few .001s at most, and wouldn't support rollers.

5. True you might be able to fit hardened races into blocks and rods, but geting a continuous race on a crank journal with a crank that doesn't come apart escapes me. That leads to running the rollers on the journal. In the 2-cycle engines I am familiar with (low hp/cube, BTW), the rollers run on the crank pin and the rod bore. They regularly wear, and need to be reconditioned. The crank is polished or ground, and the rod honed, and oversize rollers are installed to take up the extra clearance.

6. Roller cam bearings, roller lifters and roller rocker arms all run on hardened surfaces. Even flat lifters and non-roller rockers use hard surfaces because of the metal-to-metal contact. Lubricating oil yes, but no oil wedge llike the main and rod bearings.

7. FWIW, $200 is a huge increase in cost to build any OEM producton engine. 10% of that might be considered doable. I seriously doubt that a manufacturer could pass $200 more cost on the the customer and be competitive with the other OEMs.

8. 24 hp just due to bearings sounds way out of line to me on a 3L engine at 6200.

9. Which of the more exotic race cars use roller bearing engines?

TIMEBANDIT

THANKS GUYS

I have a degree in Electrical Engineering and I am about a year away from my mechanical engineering degree and I have learned more about an internal combustion engine, its stresses, friction, and performance in reading here the last 2 weeks than I have in the last year of school or all my work on our marine performance engines. The reason I asked about a total roller bearing engine is the info that was provided by Mercury performance and an engine we studied in school which was a 12 cylinder double over head cam engine and even the cam had roller bearings we were asked to compute the losses due to friction in this engine. I tried to find out who built it but all we were given was stroke, bore, number of cylinders, and a 3d cutaway of the engine.

So my next question since basically we are limited by the valve train and springs why dont we eliminate them. There are a number of solutions available at this time.

1. Soleniod operated valves although there are still some friction issues that are associated with these but less than a regular valve train. But the ability to map timing of the valves and greater valve lifts would over shadow these small friction issues. Like the man says go to the point of diminishing returns. But you still have valve placement issues. I understand some of the exotics already use this technology and it is being used on some diesel engines currently too.

2. Coates valve system has virtually no friction and no valves so air flow is not obstructed. I saw one of these engines running at a marine performance show about a year ago. The guy was trying to sell Fountian Boats on the new valve train he even offered to build a couple of BBC engines for Fountian to test with, don't know if it ever happened though. It was amazing. You dont realize how much noise from an engine comes from the valve train until you hear one without one.

3. What is the life expectancy of a set of rings that are small and low tension will they survive for maybe 50K mile?????? It is amazing that you could turn one over by hand. I tried some of our BBC's and even the ones we build for racing and had loose tolerances took about 45ft/lbs to turn over. But larger bore equals more friction.

TIMEBANDIT

Oldsstroker I spoke with the engineer at Mercury this morn and he said that you are right about the hardening of the crank journals. Rockwell 60-64 minimum. He also stated after a 20 hr break-in the standard bearing engine produced and average of 294 hp at 6200 rpms and 315hp at 7,000 rpms and the roller bearing engines produced an average of 317 hp at 6200 and 341 hp at 7,000 rpms which still suggests both motors gained 20 hp after break-in. And by moving to 7000 rpm the standard bearing motor gained 21 hp and the roller bearing motor gained 24 hp. This suggestes the roller bearing engine still has less friction.

He also stated that the roller bearing engines accelerate much faster. I wanted to get to the bottom of why did they give so much more horsepower and along with him came to the conclusion that the oil was the difference. The oil used in the standard bearing motor was a 5w-30 synthetic which their engineers felt was needed for the engine to last for 3000 hrs. The roller bearing motor got 0w-20 synthetic. I asked him if he would be willing to run another test with the 0w-20 in the standard bearing motor and tell me what the results are he said ok and will let me know tomorrow.

Also I asked about the durability of the motors and stated that you are right about changing the bearings every so often, although he stated that the quality of the bearings made now as opposed to just 10 years ago is significant. Assemblies 10 years ago were due for change at 900 to 1200 hrs now there good for around 3000hr if good synthetic lubs are used. He told me to put this in perspective, if you take an auto and run it at 60 mph for 3,000 hr thats 180,000 miles.

OldSStroker

Thanks for the good info Bandit. Good call on running the 0W-20 oil test.

Marine engines have a much harder life than auto engines. They run near their power peaks continously, while auto engines only do that during hard acceleration. A typical GM marine engine dyno durability test is 55 minutes at hp peak and WOT, then 5 minutes at idle. Repeat 300 times minimum, sometimes lots more. That would be like running around Daytona WOT @170mph for over 19000 laps, with a 5 minute stop every 155 miles!

As far as bearing quality, I don't think much has changed in high-end roller quality in the last decade other than maybe using ceramic *****/rollers. Coatings maybe, but if you need ceramic or hard coatings on a roller, you are on the edge of the operating envelope, or you have serious size constraints, and not much $ constraints. Not where I'd design a long-durability engine! I'm guessing they are still using 52100 BQ steel rollers with -120F cryo treating between the two temper cycles. This is standard practice for the rollers we produce.

IMO, it's the oil that has improved durability the most.

3 hp change due to friction from 62-7000 is less than one % brake power improvement. I still wonder where the extra 20 hp is coming from in plain vs. roller engine.

As for faster acceleration, maybe the engines have different rotating inertia. If the roller bearings have to fit in the same block space, the crank has to have smaller journals, so maybe less inertia. Are they running step dyno tests, or accelerating tests? I'd guess step tests for marine.

Keep asking your source questions. Maybe he/she will send you some dyno output data. I'd be interested.

TIMEBANDIT

Ok guys
My guy from Mercury called and stated by going to the 0w-20 oil the standard bearing motor gained 7 hp at 6200 rpms and 8 hp at 7000 rpms. But the data suggests that it will not survive the 3,000 hr durability requirement. He also stated that if roller bearings are designed into the block its not much more expensive. And it would be even less on a production line. As a matter of fact he said the cost to cast the 4 aluminum blocks for each motor was identical it was the cost of the special deminsion bearings that caused it to be more expensive.

Still It shows that the roller bearing set up is worth about 13 hp at 6200 and 16 hp at 7000. He said he didn't mind it was a test the some of the other engineers there had suggested anyway.

I asked him about the crankshaft weights its a wash all cranks for both type engines are 2.000 on the mains and 1.650 on the rods. All motors have the same weight rotating assembly.

He stated that the bearings used are kryo treated between tempering processes and the quality of bearings along with the quality control period is just much better than it was 10 years ago. He said this process is used for all their bearings now and 10 years ago it was only used on their race engines.

He wouldn't release dyno sheet because they are still in development and he probably shouldn't have told me what he has already.

OldSStroker

Thanks again for the info.

We have been making speciality bearing rollers for over 25 years, and have had that kind of processing and QC for most of that time. Not everyone does that, I guess. Our customers with 1930's vintage 30 hp racing outboards get the same quality rollers. Probably overkill for them.

How about asking him where the $200 cost comes in on a production engine. It still seems like a lot!

SStrokerAce

Dan,

I'm still trying to figure out why you say this. A shorter stroke with the same components does not need more and more RPM to reach the same power goals on the same displacement as a long stroke motor. In fact it will do it at about the same RPM.

The limiting piston speed of the head doesn't have to be reached to achive max power. If you were below the limiting piston speed at power peak it would make more power, since it would not be running into extremely high port velocities where the port is limited and airflow is limited.

If we were upping the displacement then yes we could reach the HP goal at a lower RPM with the same parts, but the friction of a longer stroke is higher than that of a larger bore, just due to the higher piston speeds. That and we already proved that the inerital loads are higher in a long stroke engine.

One more thing, on the coated bearing surfaces. A thickness of more than about .0003 on the bearings is way more than you need.

Here is a good quote about that

"One of the most important features of DFL-1 is it's ability to maintain it's full lubrication characteristics even in extremely thin films. DFL-1 typically will be applied in a film thickness of from .0003" to .001". Obviously this would affect clearances when the film approaches .001". After checking the thickness, burnish with "Scotchbright" or similar material until the film thickness is no more than .0003". During running, the coating will burnish to a near "0" dimension. This characteristic allows the bearing to be run with it's normal installed clearance. Coatings that form a "harder" film will also reduce friction and provide a protective layer to the bearing, however, as these coatings begin to wear , clearances will open up. DFL-1 does not have this problem."


Bret

TIMEBANDIT

The engineer stated that the total cost difference bewteen the 2 types of developmental engines is about 200 dollars. This was the difference in the cost of the bearings since both engine types required all the bearings and their dimensions be special order. And by the way the cost of one of these R&D engines is around 40 grand so 200 bucks isn't a big deal.


Special order
4 main bearings
6 rod to main bearings
8 cam bearings 4 for each head

6 rod to wrist pin bearings were standard production type used in their 2 stroke motors already.


He felt like the difference in cost between the 2 types of engines at a mass producion facility would be about a 70 to 80 dollars. And most of that would be the cost difference in the bearings and cages compared to the regular automotive bearings.

And its funny how things are done in R&D

They were told build an engine to the following specs
300 hp at 6000 rpms
Vertical engine
4 stroke
Direct fuel injected
2 or 4 valves per cylinder they ended up with 4
max displacement 3.0 liters
Max weight finished 275lbs (which means aluminum block and heads)
Max assembly line cost 10,000 including the lower unit which costs about 4,000 leaving 6,000 for the engine.

He said that they have managed everything but the weight and cost issues they are coming in consistantly at around 295lbs with a predicted cost of about 6200 dollars.