Mike P

Title says it all really.

Car felt a bit slower to pick up than usual over the weekend. I'm driving a standard MY98 scoob.

Cracks along the lines of "no wonder it feels slow" can be submitted to the Muppet forum

chiark

Yes.

Hot air is less dense, carries less oxygen... Makes a shedload of difference to turbo charged cars

pthomlinson@hotmail.com

I'd heard that weather makes a big difference - and that about 1 deg C equals to about a 1 bhp drop, and that the drop can be as big as 40BHP overall - and the water spray on STI's etc is to try an counteract this.

It's probably a load of bollocks but it would be interesting to hear from someone with a waterspray who thinks it makes a difference.

john banks

I recorded up to a 5 degree temp drop on track with waterspray. Nice enough, bit like p*$$**g onto a bonfire though.

MorayMackenzie

I wouldn't recommend p***inc on a bonfire after drinking spirits.

johnfelstead

yep, loses a lot of power when its hot like right now. You lose power due to inlet temps being higher, leading to less dense air, this means the turbo cant compress the same quantity of air so you run lower boost and the charge temp of the air entering the intercooler skyrockets as the turbo works harder to try and produce that boost. You then get the added downside of high ambient air temp not removing as much temperature from the heated up charge air as the intercooler is less eficient, so your post intercooler charge temp is even higher, this means you have a less eficient combustion process and more likelyhood of det, so the ECU drops boost and timing yet again losing power, so its a tripple wammy on power loss with a turbo engine compared to a N/A engine.

i was 0.2 BAR down on sunday compared to a normal cool day due to the heat and thats with liberal use of the IC sprays.

pthomlinson@hotmail.com

a bit too technical for me john, but it makes sense in a star trek kind of way...

about the ecu dropping boost - will it re-adjust when the weather gets cooler?

*Sonic*

Thanks for that John

bring on the cold weather again LOL

How will the car be affected by having a Dawes on, as it is still set for 15-16 PSI, which according to my boost gauge it is still achieving, although I have been keeping off boost while it is so hot

I take it, it isnt a good idea running a Dawes in this weather, if the turbo is struggling to maintain boost

Ive lost my original pipes, so I cant remove the Dawes at the moment, but I should be getting some more from the dealers tomorrow

Steve

nom

I'm guessing that the ECU - as it doesn't look at the heat anyway (well, it doesn't on a pre-bug anyway, don't knw about afterwards ), so even without the Dawes it'll be trying to maintain what it usually does. As that boost is presumably lower than what the Dawes is aiming for, I suppose it's of less concern .
Isn't it easier to just mark where the Dawes is now & just twiddle the boost down a tad until it cools down a bit?

submannz

Best days for most performance is foggy days, air is dense and the moisture in the air also aids keeping combustion temperatures down.

Leslie

If you have a big enough turbo like the TD05, you should still be able to achieve normal boost within reason, unless you are using very high boost settings. However as explained the higher temperature will still mean less charge density for the same degree of pressurisation from the turbo. Less charge density means less airflow through the engine which of course means less poke. The water spray would help but I doubt it will fully compensate. It must be all to do with Charle's or Boyle's law, but I can can never remember which, or even both!

Les

[Edited by Leslie - 7/16/2003 2:25:04 PM]

Jza

On my boost gauge yesterday after work (indicated 33 deg C) i only got 1.1bar - normally 1.2 - 1.3peak on my PPP

So i reckon the answer must be yes!

*Sonic*

and ive just took my Dawes off, and im getting 9 PSI max instead of the normal 14.5

stevebt

iTrader: (8)

was really hot yesterday and mine went up to 1.25bar so if this hot weather stuff is true mine should be good for a bit more

BarkingMad

...We had a low of 2 degrees the other night and the car's been overboosting all over the place...

Spooks

Sorry to kinda hi-jack the thread a bit
Kinda curious as to what differances the guys with front mounts find with hot weather. I know there will be a drop off but, with the intercooler being more efficient , how much difference?
Also this I have always wondered about, do you still use water spray on front mounts?
Laters
Spooks

rapac

Running fmi and no matter what the weather, inlet temps would no rise more than 5 to 8 degrees above ambient.
Measured facts:
fmi,670X270X88mm,bar and plate(AVO origin).
Temps taken via incar digit display ( from Motec48pro) from inlet air sensor placed before throtle body.
Car moving, inlet max +3 above ambient.
On full boost(1.4 bar)starts with +8 and stabilized at +5
No water spray used.

Cheers

TonyBurns

iTrader: (3)

So.....
I know that you loose power in the warm weather, but i take it your egt's would be slightly higher in hotter temps due to less dense air etc? as the engine would be working harder?

Tony