Durability Targets

[rengine]

Apologize if the question is too vague.

A few Q's

How do you define " durabiity targets " for an engine.
hours, Milage other or a combination??

What would " Durability targets " look like ( ballpark) for

A. Toyota Camry
B. Porche Cayman
C. A Bugatti Veyron or Enzo.

Thanks in advance

 

[GregLocock]

Any engine destined for production I have ever worked on has had to run for 100 hours at full power. Until it does that you don't bother working on anything else.

Any engine sold in California has to stay within emissions limits for 100000 miles of actual driving with no replacement parts.






Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[BrianPetersen]

I think California is 120,000 miles emission durability now, at least for certain engine types. That milestone is going to govern everything else, because the engine won't pass its emission targets if the piston rings are worn and causing the engine to pump out blue smoke.

The big question is 120,000 miles of "what" sort of driving; that number is the mandatory length of the warranty on the emission control system.

Engine manufacturers have all sorts of test cycles that they use. Have you checked SAE standards?

Regarding sports cars versus family haulers; sports cars often have engines that are relatively oversized considering the daily-driver mission that most sports cars end up seeing in real life, and family haulers can end up towing caravans/trailers that put lots of load on the engine for extended periods, so on that grounds I don't think it warrants any difference. A 50cc engine in a scooter or moped is probably going to live its entire life at either idle or full load.

 

[WGJ]

Greg - did you miss a zero off?

When I was running durab on 6 litre DI diesels, the base durability test was 55 min at full rated speed and load and then 5 min at idle. There was a 1500 hour test as well.

"Customer correlation" is the buzz phrase.
Know your customer, know how they treat their vehicles, know what they expect for their money.


Bill

 

[rengine]

Appreciate the responses.

I have been tasked with coming up with "durability targets" for an engine we have commisioned.

The engine is destined for a road going sports car and expect similar duty as a GT3 RS.

 

[WGJ]

I did some work to assist a certain UK manufacturer of well-known expensive sports cars a while ago.

I worked on the fuel system.

Our normal fuel pump target durability for a mass production saloon was 8000 hours of steady state running at system pressure.

To get the performance that this manufacturer wanted, we could only offer 5000 hours max - they were happy as they reckoned that their typical customer only did about 5000 mile/year, tops.

Bill

 

[rengine]

thanks.

Greg, can you confirm that 100 hour figure?

WSJ, can you please elborate on the 1500 hour test.

Saw a piece on TV a while back on Harley Davidson VRod development. they used a test simulating a Autoban trip for 500 hours ( forget the name )

Our engineers want to hold 25 Hours at 10% over redline before moving onto an 500 hour test.


again thanks for the responses.

 

[Pud]

25 Years ago we used to run a 400 hour endurance test on small petrol engines 2 litres approx - it comprised 80 x 5 hour cycles, each cycle consisting of (e.g - cannot remember precise details) 1 hour full load full throttle, X hr at max torque, Y time at 1/2 throttle 1/2 load, Z time at tick over, etc. This interspersed with recommended oil changes, valve clearance checks etc.. As Greg suggested, 500 hrs. full load.

Iirc, this equated to 100,000 miles very hard driving (salesman type)

As an aside, the company were not renowned for quality and are no longer in business!

H

 

[WGJ]

The 1500 hour test was the same 55/5 cycle as the 1000 hr test.
These were 6 litre diesels - 55 mins at full load, rated speed (once you got to the rated/governed speed that was it - no 110%), followed by 5 min at idle.

I'll ask about the current state of gasoline durab cycle but can't give you an answer until next Mon/Tue as I'm on a course offsite at the moment.


Bill

 

[GregLocock]

100 hours WOT is what you do at the start of an engine program, just to prove you have a design that really will hold together. I decided against looking up the production durability test.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[romke]

i would say about 300000 km for passenger cars and 1500000 km for trucks under favourable running conditions - that is about the design standard in Europe nowadays.

running the engine at full load for a given amount of time is only part of the picture. in some applications engines are put up with stop and go use and that places a completely load on the various components.

most standard tests for luboil development for truck diesel engines last for 400 to 500 hrs, the idea is to get information that would be comparable to what the engine would experience in actual service over 1500000 km. to a certain extend it is possible to get the necessary info in this type of "fast motion" tests, but most manufacturers have additional field tests in actual vehicles on the road where engines are disassembled at the end of the test for inspection of various parts.

 

[dgallup]

When I worked in the heavy duty (class 8) truck industry over 25 years ago we routinely did 2000 hour oil consumption tests. The engines ran full throttle at peak torque, peak power and some speed in between. We had a number of aggravated durability tests too that went by such colorful names as "Super Rock Crusher". These would be over fueled, over speed with advanced injection timing compared to rated speed & power for up to 1000 hours. They would be set to aggravated peak cylinder pressure, pre-turbine temperature, injection line pressure goals. The idea was to catch any design weakness with a relatively short test. We also had high mileage customers who got free prototype engines in exchange for meticulous record keeping and access to their trucks. We would tear down their engines at 250,000 & 500,000 miles for inspection & measurement.

 

[xlch58]

Greg's numbers look in line with what I have read elsewhere.

I have the GM Automotive Test Code for 1967. It specifies a two hundred hour durability test. The GM test code requires the engine to complete a 200 hour test schedule "without major failure". The engine is cycled between peak torque rpm and peak hp rpm +200 rpm (max rpm not to exceed 4600)on five minute intervals. Every five and a half cycles, speed to be reduced to idle from max test speed by closing throttle for two minutes, after which engine speed is brought up to maximum upshift speed within 10 seconds ± 5 seconds, the speed is then reduced again to the peak torque rpm and the normal cycle is continued again. The engine is inspected every twenty five hours for cranking compression, blowby, belt tension and ignition timing.

I have heard that GM's test in the 90s was updated. This is excerpted from an article by a former GM employee, Max Freeman. It was written for Contact Magazine, which is devoted to the conversion and operation of automotive and non traditional powerplants for aircraft:

"As a routine part of an engine development program we tested the engine at full power, maximum RPM. We ran it at 6000 RPM, pulling 215 HP at wide open throttle, for 265 hours. That's a continuous 265 hours of wide open throttle, far worse than autobahn driving, because even on the German Autobahn, you wouldn't be at 6000 RPM. That is a standard durability test. We run many engines through this test as a matter of course.

Specific development focus is on the crank, pistons, rods, block structure, timing drive wear; we get a lot of full load cycles in a hurry. It isn't necessarily designed to replicate customer driving but to get development answers. Wear and fatigue are accelerated. The test is particularly applicable in proving out dampers and their effectiveness. If the damper is not properly tuned to the engine the crankshaft will inevitably break in that time period.

A number of other engine tests are utilized. We use a variety of specific tests to accelerate engine wear and to look at fatigue failures. The cyclic endurance test is now called PTED (power train endurance). It closely approximates cyclic durability. The engine is cycled from its torque peak to its horsepower peak, at wide open throttle, then down to idle, then accelerates up to shift points, then back down to the torque peak and then horsepower peak. This test is run for 400 hours. Once again, it's a wide open throttle test for 400 hours. The RPM for this engine, ranged between 4400 and 6000 RPM, back and forth in about a 5 minute cycle. The dyno computer will occasionally bring the engine down to idle, up to 6500 RPM shift points, and then back to the 4400 - 6000 RPM 5 minute cycle.

Thermal cycle tests are run to define engine capability under cold weather condition. We run the engine at full throttle at 4000 RPM, bring it down to idle, stop it, switch the coolant valves to drain the hot coolant, pump the chilled coolant from the chiller until the metal temperature stabilizes at 0 degrees F. Frost forms on the outside of the block, as the cold coolant rushes into the engine. When it stabilizes at 0 F, we motor the engine, start it, come to full throttle at 4400 RPM, the valves switch and the coolant temperature starts to climb. It climbs back up to 260 degrees F. It takes 10 -11 minutes to complete one cycle. The engine must pass 600 cycles without any sign of failure. We typically run 1200 cycles and a probe test will run 1600 cycles. That's a (sic) excellent gasket killer test. Head gaskets are the first to fail because of the rapid expansion and contraction.

A powertrain endurance test simulates in-vehicle operation. The Ypsilanti plant uses it for testing transmission. We, of course, use it to look at engine performance. The equipment consists of an engine/transmission combination, which sits on a dyno with large steel inertia wheels. The inertia wheels are being driven by the transmission output shaft, just like in a car. They cycle is brutal; the engine is at idle in gear. The engine accelerates wide open to 6200 RPM, upshift occurs, 6200 RPM is reached, upshift occurs to 3rd, 6200 RPM is reached, upshift occurs to 4th, the wheels turn up to 135 MPH depending on the application. The second half of the cycle calls for a closed throttle down to 70 MPH, then wide open throttle with a downshift to 2nd, the engine goes back up to top speed, coasts down so that the transmission selects down to a lower range. The engine is in an overrun condition all the way down to idle; i.e., the engine is being used for braking. That's one cycle. One transmission life cycle is typically 12K - 13K cycles of the above test. We will run an engine through 4 or 5 transmissions. This is a very harsh schedule for the engine, particularly because of the overrun braking.
Cylinders and rings suffer the most on this test.

We run some idle tests to verify low speed operation. The engine is run at idle for about 2000 hours to make sure of adequate oil flow at idle.

We use all those engine tests in addition to fleet tests and extensive vehicle road testing. The customer can be assured that the PV6 engine is a thoroughly tested advanced design that matches or exceeds competing offerings."

 

[GregLocock]

That's a great starting point. The old engine lab wisdom was that high speed no load was the best way to break engines, we didn't do much overrun/motored durability that I remember.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.