Is low specific output the secret of engine life?

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Originally Posted By: OVERKILL
I don't believe that to be the case. The piston/rings/walls only have a certain number (an insanely high number but still) of strokes in them. The rate of wear directly correlates with RPM; an engine spinning 9,000RPM is wearing the cylinders faster than one spinning 2,000RPM. Certainly tweaking technology and choice of materials plays a role here but ultimately high cylinder pressure (high load) and high rate of scrub at that high load will wear the bores faster than that same load but at a far lower rate. The bearing area, assuming always hydrodynamic and ignoring fatigue are not affected by this but anything that is boundary will have wear that follows frequency.

I posted second UOA with PP 10W30 for S2000 yesterday.

High RPM did shear the oil quickly, virgin PP 10W30 has 10.3 cSt at 100C after 4500 miles it sheared down to 9.24 cSt. But somehow wear metals are fairly low at no more than 1 PPM.

Previous oil was a mix of Castrol 0W40 and 0W20. It sheared to 9.76 in 4k miles and wear metals were low too.

The car had many WOT to 8k RPM each drive, and it spun more than 4-4.5k RPM on highway speed of 80-85 MPH.

The 2 UOA's showed that high RPM didn't increase the wear rate in the S2000. But I will change the ratio of the mix for the next oil change, increase xW40 to 2/3 so that after 4-5k miles it will be no lower than 30 weight.

OT: MPG increases substantial from 85 MPH to 75 MPH, almost 10%.
 
But UOA's don't show wear, they may show you excessive wear if some component decides to go sideways but they do not tell you the rate at which the bores and other components are wearing.

Also, are you sure your oil sheared or was it fuel dilution? A 10w-30 should have very little VII in it and is possible to be formulated without any VII's at all with a quality base oil.

Doug's OTR trucks had UOA condemnation limits of ~100ppm for Fe, yet a 1.2 million Km tear-down showed no discernible wear in the bores and all components were fit for continued use. He has stated many times that UOA's are not to be used as many here attempt to use them and you appear to have fallen into that trap because it supports your notion that the engine in your car, despite being high strung and with high power density should be long lived and low wearing because it is a Honda product.

High performance engines are designed for high performance, not long life. There is a relationship between those two things that cannot be designed around. When you are singing at 9K and making 120HP/L you are compromising longevity for that level of performance. It doesn't mean it is going to fail early, but it does mean you aren't going to get 700,000+ miles out of it like you can with a much lower power density and much slower spinning Ford Modular for example that will spend its life loafing along at under 2K for the most part.
 
Originally Posted By: HTSS_TR

I posted second UOA with PP 10W30 for S2000 yesterday.

High RPM did shear the oil quickly, virgin PP 10W30 has 10.3 cSt at 100C after 4500 miles it sheared down to 9.24 cSt. But somehow wear metals are fairly low at no more than 1 PPM.

Previous oil was a mix of Castrol 0W40 and 0W20. It sheared to 9.76 in 4k miles and wear metals were low too.

The car had many WOT to 8k RPM each drive, and it spun more than 4-4.5k RPM on highway speed of 80-85 MPH.

The 2 UOA's showed that high RPM didn't increase the wear rate in the S2000. But I will change the ratio of the mix for the next oil change, increase xW40 to 2/3 so that after 4-5k miles it will be no lower than 30 weight.

OT: MPG increases substantial from 85 MPH to 75 MPH, almost 10%.


Even if you had a hole in the block, a $20 UOA would not show it. Probably would've been the best looking UOA you've ever done
lol.gif
 
Originally Posted By: OVERKILL


I don't believe that to be the case. The piston/rings/walls only have a certain number (an insanely high number but still) of strokes in them. The rate of wear directly correlates with RPM; an engine spinning 9,000RPM is wearing the cylinders faster than one spinning 2,000RPM. Certainly tweaking technology and choice of materials plays a role here but ultimately high cylinder pressure (high load) and high rate of scrub at that high load will wear the bores faster than that same load but at a far lower rate. The bearing area, assuming always hydrodynamic and ignoring fatigue are not affected by this but anything that is boundary will have wear that follows frequency.

If you designed a gas engine just to run at 6-9k rpm, you could get away with very low tension rings and low compression and cylinder pressures to make its power though. Honda used a longer stroke to aid in low end torque to make it streetable, but if they were just going for hp in the 6-9k range, they probably would've shortened the stroke I'd think.
I think many of the midsize diesels in construction equipment kind of operate in this area, they spin easy at relatively high rpms to make their hp, as they don't actually need any low end torque in normal use, just a bit of torque rise down from their operating rpm to keep from bogging out when asked for a bit more than max power.
My little 2L NA tractor runs this way with its HST, you just set it between 2000-2400 rpm and do your work. Below 1600 or so it starts to sound like its working hard and puffing some black smoke like an old tractor but its far better to let it rev.
 
You could get away with low compression but then it would make less power, which sort of defeats the purpose. Yes, Honda used a longer stroke, to bring the power band down (and bump up displacement) with the engine change between the two generations but they both still rev to the moon compared to your typical gasser.

If you are dealing with a displacement limit, then chasing higher RPM power becomes a necessity. Or if you are just going for the engineering challenge which appeared to be Honda's reasoning. You can only wring so much power out of a given level of displacement. Forced induction and/or RPM become factors in how much air do you want to pump; how much juice you want to make.

Driveability then also becomes an issue as wilder camshaft profiles lead to rough idles, poor low speed operation and fuel economy loss. It's an incredible balancing act and there are various compromises taking place to hit a target that does what needs to be done well, done well.

2-3K is not really high RPM for a diesel compared to what a comparable gasser runs or even some more consumer-oriented diesels. Look at what a TDI spins to or some of the later PSD Ford's and you are doubling that (the 6.0L PSD had a 4,200RPM fuel cut-off).

Also, low tension rings bring with them the issue of oil consumption (just ask BMW) which is fine for a track car or race-oriented engine where you are trying to extract the last ounce of power out of a given package but isn't a great choice when longevity is a concern because of all the contamination that gets by the rings and into the lube as well.

Extended high RPM operation brings with it a suite of challenges that affect partial or overall engine life due to component durability issues that are simply a part of that mode of operation. Valve spring fatigue, rod stress, fastener stress, rotating assembly control (crankshaft deflection) are all a reality here and that's why Honda and other OEM's shoot for as light as possible components in many of these areas in order to minimize the effects of the stresses created in that operating environment, but they cannot eliminate them.

In comparison, a low speed engine can have weaker springs with much longer lives, heavier rods, heavier crankshaft....etc. This is why displacement is usually what is chased when long life is a requirement and why engines doing constant duty are relatively low power density and operate with a low RPM ceiling. Your own example of marine engines earlier is a great point, as the stock 302 in the Mustang had a rev limit of 6,250RPM, but you'd never see close to that out of its marine counterpart because of durability issues at that speed with sustained operation. Valvetrain control in a pushrod engine at high RPM requires more spring pressure, which means shorter spring life.
 
There are a few ways to get a long lived engine.

1. Low stressing it, which is what the OP is talking about.

AND/OR

2. Using HIGH quality components and exacting assembly standards
 
Originally Posted By: OVERKILL
But UOA's don't show wear, they may show you excessive wear if some component decides to go sideways but they do not tell you the rate at which the bores and other components are wearing.

Also, are you sure your oil sheared or was it fuel dilution? A 10w-30 should have very little VII in it and is possible to be formulated without any VII's at all with a quality base oil.

Doug's OTR trucks had UOA condemnation limits of ~100ppm for Fe, yet a 1.2 million Km tear-down showed no discernible wear in the bores and all components were fit for continued use. He has stated many times that UOA's are not to be used as many here attempt to use them and you appear to have fallen into that trap because it supports your notion that the engine in your car, despite being high strung and with high power density should be long lived and low wearing because it is a Honda product.

High performance engines are designed for high performance, not long life. There is a relationship between those two things that cannot be designed around. When you are singing at 9K and making 120HP/L you are compromising longevity for that level of performance. It doesn't mean it is going to fail early, but it does mean you aren't going to get 700,000+ miles out of it like you can with a much lower power density and much slower spinning Ford Modular for example that will spend its life loafing along at under 2K for the most part.

Blackstone comments "The viscosity is a little thin for 10W30, but no fuel turned up that may caused that"

Same for previous oil of 50-50 Castrol Edge 0W40 and 0W20, that mix should have 10.75 cSt. After 4k miles the cSt was down to 9.76 with no trace of fuel.

I am a little uncomfortable with shearing of 2 UOA's, I will increase xW40 to 2/3 and reduce xW20 to 1/3 for next oil change.

I think S2000 is hard on oil, it needs thicker than 10W30. The other car, the E430, is easy on oil so I changed to xW20 instead of M1 0W40.

Note: All previous oil changes were 4500-5000 miles in 1 year without oil lost, never top off.
 
Last edited:
Originally Posted By: HTSS_TR

Blackstone comments "The viscosity is a little thin for 10W30, but no fuel turned up that may caused that"

Same for previous oil of 50-50 Castrol Edge 0W40 and 0W20, that mix should have 10.75 cSt. After 4k miles the cSt was down to 9.76 with no trace of fuel.

I am a little uncomfortable with shearing of 2 UOA's, I will increase xW40 to 2/3 and reduce xW20 to 1/3 for next oil change.

I think S2000 is hard on oil, it needs thicker than 10W30. The other car, the E430, is easy on oil so I changed to xW20 instead of M1 0W40.

Note: All previous oil changes were 4500-5000 miles in 1 year without oil lost, never top off.



Blackstone's method for determining fuel dilution isn't great. An easy way to determine whether there has been dilution or not is to look at the flashpoint relative to virgin. Fuel reduces the flash point. your previous UOA had even higher fuel in it based on the flash being in the mid 300's.
 
SInce you have so many variables you need to eliminate them to determine the answer to this question. The question is, does specific output affect engine life? The only way to know would be to take two of the exact same engine and run one full out and one at half throttle. It's pretty obvious which engine would outlast the other. Now the question is, which engine performs more work before it's death? This would be evaluating hp per cubic inches. Another would be to evaluate hp per lb of weight.
 
Originally Posted By: KrisZ
Here are some interesting numbers.

The average 18 wheeler engine size is about 15L. Their maximum gross weight is 80,000lbs.
Even taking a conservative 50,000lbs loads, it puts 3300lbs per 1L of engine displacement. Maximum 80,000lbs puts that number at 5300lbs per 1L of engine displacement!
Now imagine a 1L engine pulling a 3000lbs to 5000lbs vehicle that would rev as any normal gasser would. It would not last too long in that kind of usage.


Means nothing....if it takes a minute to get from 1-60 it just means the engine was not pulling near what a passenger car does doing 0-60 in 16 seconds.
 
It seems to all be a compromise. Take speed limits.. If we really were safer at low speed, cars would be banned and we would all be walking.IMO


It is about usage. Like mpg,,sure it is burning less fuel at 30mph than at 60mph, but probably not half as much......so 60mph is more efficient. Now, I domt know if the engine would last twice as long at a constant 30mph than at a 60mph...I dont think you can tell.



OVERKILL, I question your assumptions of high speed engine longevity. Sure maybe holding the pedal to the medal all day will result in problems. But take a good engine and set the cruiseon 60mph......come back the next day and set it on 90mph.....observe.....I would guess it would burn alot more oil at nnety, but NASCAR can run 500 miles all day t 8000 rpm in a OHV V8. I do wonder about how much oil they use in races......


Anyway, the only real problem I see with prolonged high speed operation is dispelling the heat. Maybe no car is really meant to ride top speed all day other than a NASCAR....no not road racing they brake for the turns, street cars seem built to do 80mph at ease all day long and there probably arent too many people in many areas with the proper equipment that can sustain high speed. Traffic conditions, blind curves and hills, rough pavement, etc.
 
All else being equal, a longer piston stroke will wear the cylinder liner slower because there's more surface area to wear out versus a shorter stroke.

Higher piston speed increases heat from friction which increases wear.

Million-mile diesel engines have a very long stroke (for more torque). The moving parts are heavy for durability, but that higher weight necessitates lower recriprocating speeds. All these are favorable to longevity.
 
That's going to come down to rod ratio as well.

Long stroke and poor rod ratio is a bad thing.

The increase in piston speed is a factor as well. Long stroke and rpms don't always agree.
 
The BMW Airhead motorcycle engine is low stressed, and for a motorcycle engine low reving and has a low output. In the owners manual you get a whole pile of specs - power and torque charts, the rpm at max hp, maximum engine speed...and maximum continuous engine speed...which is 50 rpm higher than max hp speed. This engine is designed to run at the redline all day, everyday....and it will.

The old aircooled VW Beetle was also designed to run flatout all day, it's maximum speed was also it's cruising speed. It's engine life is no secret, they wore out the same as any engine of the time. The Germans tend to set up their vehicles for high speed use.
 
Originally Posted By: akela
I think the right criterion is

vehicle_weight / engine_displacement

The less the better (from the engine life viewpoint).


I do not thing it is so simple. When I was working at a Ford dealership we say an old F250 that was used on the Rodeo circuit towing horse trailers for a rider. He had over 700k on the original V10 engine. Big engine, big truck, and pulling a moderate amount of weight.

I have also seen a metric ton of old 4.6 lincoln town cars with TONS of miles on those heavy boats. Sadly they are usually dragging their hind end from the rear air suspension going out.
 
Many Volvo bricks had turbocharged gasoline engines, yet they lasted for ages. Many Volvos that weren't bricks still had excellent engine life even with turbos.

I'm fairly certain that the right design and build quality is what separates a long life engine from a short life engine.
 
Originally Posted By: crazyoildude
What 4.6 has 275 HP?

96+ Mustang Cobra (4.6 4V)
05-09 Mustang
06-10 Explorer
09-10 F-series
All 4v's
 
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