Stress on engine during autocross.

Discussion of anything that doesn't fall into the Solo II and RallyX Categories

Is the stress on a stock engine during autox any different than what could occur on the street?

Yes.
11
34%
No.
21
66%
 
Total votes: 32

thrdeye
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Stress on engine during autocross.

Post by thrdeye »

Poll inspired by dumb thread on NASIOC. Guys car blew up (stock STi) because the 08's had a tuning problem, causing them to run lean sometimes. Subaru rebuilt engine under warranty, idiots on NASIOC are blaming autocross.

Do you think that autocross is any harder on a stock engine than what could conceivably occur on the street?

I say no for a variety of reasons.
Chris Harp
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Scuffcakes
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Post by Scuffcakes »

Nope. There's a red line on the tach for a reason. That's with a margin of safety so they don't end up with tons of warranty claims. Everything you do to the engine autocrossing is well within the designed tolerance.
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Budman
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Post by Budman »

I think yes, but only due to the engine rpms being higher than normal and for longer periods time. Higher rpms puts more stress on moving parts and also could cause decreased lubrication.
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01badz28
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Post by 01badz28 »

Autocross isn't rough on engines at all!!!

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

Even after my blow up, I'll have to vote no. I think drag racing is a lot tougher on the driveline / engine.

My problem was probably a random part failure or the product of a warranty rebuild as well.
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Post by backpacker6 »

That's ridiculous. If anything I would say an engine that is autocrossed is better taken care of (frequent fluid changes, etc.) It sure is hard on tires though. :lol:
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Post by backpacker6 »

Budman wrote:I think yes, but only due to the engine rpms being higher than normal and for longer periods time. Higher rpms puts more stress on moving parts and also could cause decreased lubrication.
Yeah but it's only for a total of about 6-8 minutes per month. :lol:
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EliseAutoXr
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Post by EliseAutoXr »

I voted no... I beat on my car all the time, the short 40sec runs might even be a break for it, hehe.
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thrdeye
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Post by thrdeye »

Budman wrote:I think yes, but only due to the engine rpms being higher than normal and for longer periods time. Higher rpms puts more stress on moving parts and also could cause decreased lubrication.
But during an average autocross run of ~45 seconds, how long are you going to be at or near redline?

I would venture to say that taking a car to redline in gears 1-3 while getting on the freeway would net you an average higher maintained RMP than your average autocross run.

eidt: and of course the service guy would say yes *WARRANTY DENIED* :lol:
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Post by scottgib »

I voted yes for the following reasons:

a) I assume you mean over period of time although short instead of instantanious. There would be no difference if instantanious.

b) Just to keep up my contrarian role

Seriously, there is probably a little more time at max rpm under load in autoX, but it is a small amount and driver controlled. This is probably more true of us that run lower torque, high rpm cars such as Miata's, Mini's, S2000's, etc. that use 1st gear more than say a WRX. Rarely on the street will I go from full load at max rpm to no throttle without depressing the clutch to change grears. This is common in autocross.

If one were to short shift staying away from max rpm, and drive very smoothly, the extra stress would be negible IMHO.
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Post by Wheelman_13 »

I wonder what effect heat cycling and short on-off cycles might have. Turn the car on, let it warm up to op-temp, flog car for 35-60s, idle car for a minute, turn off for 5-10 minutes, then repeat 3-7 times.

That said, I voted no, because I'm sure stop & go city driving and traffic idling is probably still worse.

Roadracing would be a different story obviously.
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Post by steverife »

I would tend to say yes.

I bought an eBay knockoff Mugen chip for the CRX and it didn't have a rev limiter.

"Everyone is going to third and I'm not even hitting the limiter. WTF?"
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Post by thrdeye »

steverife wrote:I would tend to say yes.

I bought an eBay knockoff Mugen chip for the CRX and it didn't have a rev limiter.

"Everyone is going to third and I'm not even hitting the limiter. WTF?"
I said stock engine. Read noob.
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steverife
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Post by steverife »

thrdeye wrote:
steverife wrote:I would tend to say yes.

I bought an eBay knockoff Mugen chip for the CRX and it didn't have a rev limiter.

"Everyone is going to third and I'm not even hitting the limiter. WTF?"
I said stock engine. Read noob.
engine != ecu

...but seriously, I'd say yes. How much harder? Eh, who knows?
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thrdeye
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Post by thrdeye »

steverife wrote:
engine != ecu

...but seriously, I'd say yes. How much harder? Eh, who knows?
ecu = raised rev limit = engine revving higher than stock = does not qualify for poll question
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01badz28
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Post by 01badz28 »

My Gtech recorded all my runs the day I blew my car up, I never even got into the rev limiter.

And before you all point out my motor wasn't stock:

1) The cam had a GM part number. :lol:

2) You could get an engine from GM in that specification.

3) It was running a rich tune. (Verfied by my dyno pull with wideband the week before).

4) The engines bottom end was untouched, as were the heads, and it was running stock compression.
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