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Author Topic: Better when cool  (Read 1892 times)

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JasonH

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Better when cool
« on: 23 August 2006, 20:39:48 »
I've noticed that on cooler days my car runs smoother.

When the ambient air temperature is high the car definitely has a lumpier tickover and just doesn't rev as smoothly. It's not to do with engine temperature either because the effect is fairly immediate. Hot day, cold start = lumpy, then stays lumpy.

I'm thinking air intake temperature sensor and/or MAF.

No error codes and car otherwise fine.

Thoughts anyone. What about cleaning the sensors?
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Tezray

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Re: Better when cool
« Reply #1 on: 23 August 2006, 20:48:57 »
Are you sure it's not just to do with air humidity/density? Because these factors do have a definite impact on performance and unfortunately there's not a lot you can do about it....Is it really very noticeable? I notice it in mine, but i am very picky/sensitive to things like that lol
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JasonH

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Re: Better when cool
« Reply #2 on: 23 August 2006, 21:40:48 »
I'm really picky too! I suspect someone else wouldn't notice the difference - but I do!
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tunnie

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Re: Better when cool
« Reply #3 on: 23 August 2006, 22:16:13 »
my car runs much better on a cooler day, most cars do.
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Markjay

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Re: Better when cool
« Reply #4 on: 23 August 2006, 22:17:53 »
...what grade oil do you use? 10w40?

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JasonH

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Re: Better when cool
« Reply #5 on: 24 August 2006, 08:48:39 »
Vx 5W30 full synth, long life.

Oh no an oil thread....
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Marks DTM Calib

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Re: Better when cool
« Reply #6 on: 24 August 2006, 08:56:13 »
Well they are bound to run better on a cold day.

Have a read of the MAF sensor FAQ and consider that when its cold, the air mass is higher and hence you can get more air into the engine.
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mjl1644

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Re: Better when cool
« Reply #7 on: 24 August 2006, 13:37:51 »
...perhaps this is why they invented Intercoolers.... :-/

mike
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Markjay

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Re: Better when cool
« Reply #8 on: 24 August 2006, 14:05:54 »
I am a bit confused about the fact that the difference is when idling - I think the air volume should have more of an impact at high engine revs.

Going back to the oil issue... (I know, I know  ;D)


The 5W-30 is a new full-synth oil from Vx (replacing the older 5W-40), so I am assuming that you only recently started using it - can you tell if this rough idling on hot days issue was there from the start, or did it appear after you first changed the oil to 5w-30?



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JasonH

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Re: Better when cool
« Reply #9 on: 24 August 2006, 14:47:05 »
It was there with 5W40 too.

TBH it's not that bad, but it's noticeable.
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zoltron

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Re: Better when cool
« Reply #10 on: 24 August 2006, 22:33:43 »
I'm a complete fool when it comes to how engines work but as I always understood it the colder the air entering the engine the more it aids combustion, is this the basic principal of performance cars?
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