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 Post subject: Short drives
PostPosted: Sat Jul 08, 2017 10:03 pm 
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Hey all, im abit unsure regarding the Short drives-Cold motor=Floods etc and how its not good for rx8s longevity..I drive about 4-8 kms each way for work..so my rx is a daily car.I always warm it up to at least the needle is moving or halfway then drive.Do i still need to rev the motor to 3.5 for a few seconds then turn it off? Or can i just switch it straight off? And when if ever do we need to idle it for abit before turning off? Eg:after a hard drive? I do what alot of ppl have said on here and rev it out to at least 7 thou rpm but not to the beeper yet.is this sufficient to blow the carbon out? Also what could make my motor drop revs to under 900 when i turn the ac on? Usually when ive turned off then on after its been warm its abit slower by about 2-3 cranks but fires right up,is this ok? Its getting a service on monday and matt13b gave me a contact for a guy to do a compression test for me so hopefully all will be looking good..any advice is much app


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 Post subject: Re: Short drives
PostPosted: Sun Jul 09, 2017 10:04 pm 
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Location: QLD
I don't drive mine daily.
But I do love inner suburbs. So sometimes my trips aren't ver long.

I think 4-8km is a decent drive.
The advice I was given was to to worry about letting it idle to warm up. The logic behind this is that cold engines wear quicker than warm engines, so you want to bring you engine up to operating temp as quick as possible. Do this by driving easily and keeping the revs below 3.5 until the the brine reaches operating temp. When it does reach a good temp, onto us driving keeping revs below 5k.. after a few more minutes you should then be able to redline it safely.

I never really do the rev up before shut down thing that people do here, not do I let it fool down before shutting off.. my logic is that the engine will cool down once turned off anyway, I don't see who's idling it for x time will help is cool down more efficiently or better. I feel like it's just a waste of fuel and time...
Also the logic behind the rev to 4K and turn off is to create inertia and spin excess substances in the combustion chamber out. I think that if you were at a decent operating temp when shutting doors an this shouldn't be a concern? (Hope others can chime in here)


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 Post subject: Re: Short drives
PostPosted: Sun Jul 09, 2017 10:43 pm 
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Location: Nth Sydney
I'd love to know of there is any relevance to the rev prior to shutdown in a modern car with an ecu??

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 Post subject: Re: Short drives
PostPosted: Mon Jul 10, 2017 2:00 am 
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+1 on Soldier's post.
I warm up to operating temp at idle before every drive, but I also agree that it's fine to warm it up by driving at low rpm on the road. However lets say you take a drive that is 2-3 minutes long, I would not drive while warming up as by the time you get to your destination you would have probably just reached operating temp.

The only time i see logic in revving up a little before shut down is if you have not reached operating temp to 'spin out' more of the rich air-fuel mixture to prevent the chance of it flooding. If the compression is good and ignition is healthy you will not have to worry about flooding I would say 99% of the time.

As for shut down procedure, I don't think its relevant for typical road use, or even a spirited drive. And its kind of unlikely you would go straight from high rpm driving to immediate shut off. I feel this is only a concern on the track.

As for rpms, the higher the better - with moderation of course.


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 Post subject: Re: Short drives
PostPosted: Mon Jul 10, 2017 1:13 pm 
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Thanks for replys..Ive had my rx a week now and its been fine.Was confused about the cold/hot procedures so i was doing abit of everything.:cool down,revs etc.On Saturday after my last drive i did the rev to 3k thing,engine was at operating temp but i only ever held it for 2/4 seconds..Then Sunday morning started her up and noticed smoke coming out of the exhaust.it did this for about 30 seconds then cleared.had me abit worried but then i saw a de-flood video on YouTube and they said its just excess fuel burning off.Ive since had a few more drives and it hasn't happened again.im wondering if its anything I should be concerned about?


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 Post subject: Re: Short drives
PostPosted: Mon Jul 10, 2017 5:34 pm 
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Aznsnoopy wrote:
Thanks for replys..Ive had my rx a week now and its been fine.Was confused about the cold/hot procedures so i was doing abit of everything.:cool down,revs etc.On Saturday after my last drive i did the rev to 3k thing,engine was at operating temp but i only ever held it for 2/4 seconds..Then Sunday morning started her up and noticed smoke coming out of the exhaust.it did this for about 30 seconds then cleared.had me abit worried but then i saw a de-flood video on YouTube and they said its just excess fuel burning off.Ive since had a few more drives and it hasn't happened again.im wondering if its anything I should be concerned about?


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And the car won't allow you to rev above about 4k rpm i believe and increases rev range up to full range as it warms up. Something like that anyway. I usually just start, wait for the noise where the revs drop down from the high starting idol. You can hear it obviously and then I drive using low revs until safely warm...... Then I cane it

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 Post subject: Re: Short drives
PostPosted: Sat Sep 16, 2017 9:33 pm 
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Location: Port Macquarie
I start similar to Matt13b, I wait until the exhaust fan stops, which is usually 35°C coolant temp. This is also the temp that the idle mixture leans out to around 14.4 AFR and the idle rpm settles down.


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 Post subject: Re: Short drives
PostPosted: Fri Sep 22, 2017 11:56 pm 
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The series 1 doesnt have a progressive rpm low temp limit like the S2, once coolant temp reaches (from memory) -10*C the ECU will let you go to 9000rpm.

I wouldnt let it idle all the way to operating temp, you will just foul your plugs over time. Let it sit for 30 seconds and then keep it below 4000rpm until 3 minutes after it reaches operating temp (the temp gauges isnt linear, it reaches centre position below operating temp - and stays there until well above). Then give it a good redline.

The real concern with repetative short drives isnt flooding, its that the oil doesnt reach operating temperature (oil temps usually lag behind coolant temps in warming up). When this happens the moisture and fuel wash that ends up in the oil on a cold start doesnt get a chance to evaporate off, abd eventually the oil turns to sludge and can destroy the motor. This happened to the previous owner of my car who drove 7km everday to work, thread below has some photos,

viewtopic.php?f=5&t=5389&start=45

In terms of reving before shutdown, if your ignition is healthy it wont make much difference, wont hurt anything either.

Hope that helps.


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