JD Shredds

Agreed with everything you said, but especially this bit.

rocco16

That would be difficult to say, since you don't know what RWHP and RWTQ the car produced when new. That's the whole point most of us are saying, I think.

You are probably basing your conception on the commonly held belief that the difference between crank hp and rear wheel hp is from between fifteen and twenty percent. That would make your claim an estimate, since the 15/20% is an estimate.
Based on what I have experienced on a chassis dyno, I'd put the losses of that method at about 10%....and I've always used that formula. Using this number instead of the much more generous (and ego-massaging) 15-20%, your 300hp LT has lost about 10hp, or about 3%....which is right in line with my earlier WAG.

I have no doubt that a well-broken-in engine can produce more power than it did when it was new, but to expect a complex mechanical device to be even more efficient after tens of thousands of hours of use than it was when new is unrealistic.
Them's my opinions, nothing more.

vader86

I dynoed my 86 not long after I bought it, it put down the right RWHP and TQ for a 86 L98 given the driveline losses in an Automatic. It had about 118K on it at the time.

But theres no guarantee you will get the same results. I knew the car was driven daily but taken care of before I bought it. Eventually there will always be more HP losses due to gradual wear in the cylinders and compression, lazy valves, weak lifters, or whatever. Exactly when that happens is too variable to pin a number on.

Tom400CFI

But we do know. Car was rated at 300 CHP and 330 Ctq. Using 10%, which is what *I* used for sticks, that would be about 270 RWHP and 297 RWtq. But my car did better than than by ~10hp and 15 tq....certainly, not losing power there. Agreed?



Negative. See above. I don't agree with the 15-20% at all, and I don't agree with this figure based on my experience chassis dynoing stick shift cars where we know the chp rating.


Negative. I typo'ed my RWHP yesterday. It did 280, not 260, so it "gained 10 hp". More likely, it had that, and never lost it.


Hours? Or miles? I though we were talking about 100,000 miles in this thread. Anyway, you just admitted that an engine can become well broken in and produce more power...then in the same paragraph, said it can't be more efficient. Which is it?? A more well broken in engine, IS going to be more efficient, due to potentially better sealing and less friction.

jakenks

What you are asking is not readily quantifiable without making some broad assumptions based on actual initial HP & torque ratings. Then, the amout of variables over time regarding use, maintenance and condition would make it very difficult to develop any sort of reasonable algorythm to determine your question.

mike100

I saw that episode...I think it was a wild azz guess. They never had data or never eluded to what those cars would put out on a chassis dyno when new, but were comparing crank hp to wheel hp. It didn't make sense...

Maybe they were using a 15% correction, but they never went into the details. Most cars will be within 10hp of original until the compression starts dropping off or the exhaust system becomes plugged and the engine carboned up on the intakes.

bb62

One thing not discussed in this thread was the propensity for the German manufacturers to overrate their engine power. This was a fairly common practice until about 10 years ago when the Ford Cobra was tested by an outside group that determined the stock HP was not at the advertized level. Ford (and the other manufacturers) changed their processes to make sure the two now match.

86C4Z51

I used to overhaul engines for a living. Those with owners who changed the oil religiously had cranks and bearings that went back in standard (unless sized prior to their ownership etc). Cams showed little wear but I pretty much replaced them regardless.

Those who changed their oil by replacing that which leaked out, and once in a while changing the filter, well those engines required a lot more care and concern internally than the other group. They certainly weren't making power like the cared-for engines.

I never measured a group of engines etc, never did a scientific evaluation of them all. This was in the 80s, but engines are engines. Internal wear characteristics of engines with different designs, along with a wide variance in maintenance practices and environment will cause different strokes for different folks. There's no one measurement I'd believe in unless someone started from new with a control group etc to make a measurable, valid, repeatable conclusion.

That said, cylinders will seal better on an engine with miles on it. Use of synthetic oils may yield better results with one engine than regular oil on that engine operated by someone else. Carbon will build up, which may help seal some things, clog other things. Overheating can prematurely wear parts. Once the tolerance gets out of range, failure is more likely, and power loss will happen. How much? See above paragraph.

As for German engines, Japanese engines, American engines -- these are not apple-to-apple comparisons. You'd need L98 to L98, LT4 to LT4, etc, in the same, or very similar car, driven similarly. And you couldn't have one in Michigan and the other in Florida.

Not worth the money to do such a study. Who cares that much? All I know is when I mash that right-hand pedal, I get pushed back in the seat and go like hell. That's enough for me.

dbgoodwin

I just want to know what c6 z06 made it to 180k miles without blowing up?

2HIP4U

Not enough that I can't terrorize anyone in the right chair.

rocco16

Hours.
An engine, like any other complex mechanical device, does not know how many miles it has traveled...if it has traveled any miles. It only knows how many hours it has run and the conditions under which it has run. It takes time for a car to go 100K miles, does it not?

There is a reason engines like those on riding lawn mowers, over-the-road trucks, boats, big generators, commercial water pumps, etc. have hour-meters on them....not just because they don't have odometers.

You don't seem to differentiate between "well-broken-in" and worn out, tom; they are not the same.

86C4Z51

Airplane engines are maintained by hours (turbines count cycles as well) for the same reason, rocco. Who knows how many miles they go in an hour, regardless of airspeed vs ground speed? Time spent running is the primary measure.

THE 383 admiral

Brand new Engines Or complete rebuilds do not produce maximum HP
until broken in. I firmly believe you should never command power 0 - 1500 miles or so along with 3-4 oil changes, Easy launch gradual speeds.
I also believe with proper maintenance 100k should produce the same HP level.

86C4Z51

There are different schools of thought on that. I've broken in engines using full power. Not race power, like all day long.... but you can baby a new engine too much and never get the rings to seal properly. On the other hand, you can pound the rings hard with a fresh cylinder and generate too much heat.

Glazing, the enemy of all reciprocating engines, can occur in both situations.

I recommend driving it "normally." Don't try to run a rally race, and don't Grandma it around town for 1500 miles, either. Vary the pressure in the cylinders, and don't worry about WFOing it once in a while (but NOT on the first engine start after overhaul!). Don't lug it around in high gears at low speeds (hi manifold pressure) for the first several operating hours. Higher RPMs in lower gears would be better than doing that.

The main reason for breaking in an engine is to get a good ring-to-cylinder seal. The rest of the engine, not as important as far as break in is concerned. To get that seal, you need to operate the engine as it's intended to operate.

The other best thing you can do in that time period is to use proper break-in oil (mfg recommendation) and then change the oil more often than normal.

Tom400CFI

I completely agree that broken in and worn out are not the same. Where did I state otherwise?? Not in this thread. This thread is about "horsepower lost at 100,000 miles". Even a semi maintained engine will go right on by 100,000 miles and still not be worn out, so there is no point to talking about "worn out" in this thead...other than if you're losing power at 100k, you're doing it wrong.

And as a fleet maint manager for ~20 year...trust me, I know what the hour meter is for. Thread is about a specific, 100,000k miles though. You stated a vague (and perplexing) term of "tens of thousands of hours of use". How many "10's"?? We don't know. Thread is about 100k miles, which should convert to ABOUT 2500 - 3000 hours. Not sure where you're getting your "tens of thousands of hours" in a thread talking about 100k miles.

No normally driven Corvette motor should be losing power in 100k miles...excuse me, 2500-3000 hours.


.

86C4Z51

Just for grins, most recip aircraft engines have a scheduled overhaul anywhere from 1500 hours to 2200 hours (depending on application and HP, whether they're geared or not etc). That doesn't mean they aren't running well; it's a safety thing.

However, these are mostly air-cooled engines. Water-cooled engines run closer tolerances, have more carefully regulated temps, etc. Aircraft engines run a lot like stationary powerplants, spending hours at nearly the same rpm during cruise.