Voodoo Theory

[Fenderaddict2]

Great posts. But now I'm worried about the longevity of my Roadrunner motor.

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[TearTheHorizon]

Great posts. But now I'm worried about the longevity of my Roadrunner motor.

Don't be. I've seen roadrunner coyotes past 300,000 miles. And I'm assuming that you won't put 250,000 miles at 3000rpm straight with nothing but basic maintenance in between. And thats after the 50,000 miles of hard abuse. ^.^

 

[Red]

Sorry about that -- unintended consequence.

I said that the the RR is a highly stressed engine -- but there's a difference between highly stressed and over stressed!

With common sense and proper maintenance, I wouldn't worry at all. If you're always running yours out to 7500, well, ... And let it warm up before any hard stuff!

TTH: Somebody's driven the h3ll out of their Boss to get to > 300k miles in three years or less.

 

[TearTheHorizon]

Wasn't a car engine. Dyno test engine. Hence the 50k of abuse and 250k of 3000 rpm straight.
I've seen and/or heard of most of Ford's recent 8 cyl motors (past decade or so) results on the durability dyno.

 

[Red]

Ah, dyno time. Can you elaborate on the abuse? I believe hot and cold temp tests are part of it. But how much time at max power and/or redline? Time at max torque? Acceleration rates? Anything you could relay would be very interesting (to me). And might allay fenderaddicts' worries. Thanks.

 

[TearTheHorizon]

You are correct, there is alot of heat cycling, alot of idle to redline bursts, and some (spurts of a few thousand miles) near redline. Most of it (250k) is spent at varying rpms that would be typical of daily driving and track driving. There's quite alot of time held between 1.5k-5k (daily) and 3-7k rpm (track). These dyno tests are to make sure your average joe (who isnt a pro racer and drives like he is in a fast and furious movie) won't end up being a warranty claim, and that your (literal) racer can have faith in his powerplant for years to come.

These coyote motors are very robust. The tolerance of the rotating assembly is incredible. It is a large part of this motors ability. (Reffering to space between moving parts)

I myself don't 'run the tests' persay so I don't know any of the program specifics.

 

[Dirk McGurck]

When they're running these engines, is there a load on the flywheel?

 

[TearTheHorizon]

When they're running these engines, is there a load on the flywheel?

Yes

 

[nametoshowothers]

When they're running these engines, is there a load on the flywheel?

By definition there is load - a dynometer measures engine output, therefore has to apply load to measure

 

[Dirk McGurck]

Okay. So the engine is 'driving' 3600-3900 lbs of 'car' for the 200,000 miles.

 

[TearTheHorizon]

Correct. True (as close as possible) simulations

 

[Dirk McGurck]

Correct. True (as close as possible) simulations

That's pretty cool. And those poor engines. They never get to be free.

 

[Red]

You are correct, there is alot of heat cycling, alot of idle to redline bursts, and some (spurts of a few thousand miles) near redline. Most of it (250k) is spent at varying rpms that would be typical of daily driving and track driving. There's quite alot of time held between 1.5k-5k (daily) and 3-7k rpm (track). These dyno tests are to make sure your average joe (who isnt a pro racer and drives like he is in a fast and furious movie) won't end up being a warranty claim, and that your (literal) racer can have faith in his powerplant for years to come.

These coyote motors are very robust. The tolerance of the rotating assembly is incredible. It is a large part of this motors ability. (Reffering to space between moving parts)

I myself don't 'run the tests' persay so I don't know any of the program specifics.

Thanks! Makes sense.

Do you know how many hours @ 3000 rpm equates to 250k miles? I'm wondering if it's around 2500 hours (i.e. 3000 rpm is roughly equal to 100 mph)? I also wonder how 'race-like' the first 50k miles are. As in accel rates from 4000 - 7500 rpm, duration @ 7500, and so on. Accelerating from one rpm to another creates additional stresses on the crank, rod, piston, pin, etc. The values I posted previously are all at a constant rpm (the redline value, specifically).

Also, to (hopefully) alleviate anyone's worries about longevity of their Coyote or RR engines: piston speed varies linearly w/ rpm, and peak accel varies with the square of rpm. For example, at 3000 rpm, the piston speed is 40% that at 7500 rpm (30/75 = 40%), but peak accel is only 16% that at 7500 rpm. So, you can see the stresses wanting to tear things apart, or grind things away, are far lower at more normal operating speeds.

Thanks again, TTH.

 

[TearTheHorizon]

Do you know how many hours @ 3000 rpm equates to 250k miles? I'm wondering if it's around 2500 hours (i.e. 3000 rpm is roughly equal to 100 mph)? I also wonder how 'race-like' the first 50k miles are. As in accel rates from 4000 - 7500 rpm, duration @ 7500, and so on. Accelerating from one rpm to another creates additional stresses on the crank, rod, piston, pin, etc. The values I posted previously are all at a constant rpm (the redline value, specifically).

I don't write the programs nor do I run these dyno's, so I'm sorry but thats about all I know :shrug:

I do know that the 300k miles are not 'true' miles.

If you held a boss 302 at 65 mph, in fifth gear (not sixth) you would spin just over 3000rpm. In sixth gear you are around 100 mph at 3000rpm. (3.73 gears, standard 27 inch tire)

In sixth gear, your driving over 100 days straight at 100 mph (3000rpm) to reach the simulated 250k of average use.
in fifth at 65 (3000rpm) your over 160 days.

These are engine dyno's, not chassis dynos, but that was information just for a comparison. There is no transmission persay, and no axle and tire size to truly calculate miles compared to its rear world application.

These dyno tests stop for basic maintenance (oil, plugs, etc) and that's it. But I can tell you the time for these tests is less than a tenth of the numbers above. These are simulated miles, alot of abuse is added to simulate longer periods of standard driving.

 

[Red]

Thanks. It would be very interesting to see one of these tests.

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