ROSS

I was driving my STI to the car wash today (oops! am I a bad person! call me what you like and I know its a matter of choice but I love to drive my car but polishing it all the time errr ! no thanks...ZZZZ) today gave it a bit of welly and well very little happened no savage acceleration just a flat spot over the entire rev range switched the air con off and a slight improvement is my car duff ? or does this hot spell really sap such a huge chunk of the performance. Anyone else out there had a similar experience

Ron H

Mine was running like a dog yesterday as it happens.
At about three when it was really warm it felt like a normally aspirated engine.
This morning its back to its old tricks and its hopping along nicely

R

The Zohan

I had a similar thing happen to me recently, I went to ovetake a car, put my foot on the loud pedal, hit 3000RPM and no boost to speak of, i managed to creep past the car i was overtaking. I travelled the remaining mile or two home and had a look under the bonnet to see if everything was ok (or there even!). All looked fine. I went out a little while later and the car was fine - power in the right places and so on. I have not been able to replicate the problem since.
Strange.
I have a MY99 UK car

[This message has been edited by Paul Habgood (edited 19-06-2000).]

stray15

Thats what happens when you don't buy the Porsche. No, just kidding, does it make a different sound like a struggling sound in the engine?

DavidRB

Now you know why they're popular with IT types. If something goes wrong with the engine, the first test is "switch it off & switch it on again, see if it cures the problem!"

Sith

Hey don't diss IT staff, I work in IT 'Tis true though - first thing any Helpdesk says, and it drives me up the wall.

Stangely mine wasn't suffering as much as I expected, just not quite as savege in 1st and 2nd as I'm use too. But not slow by any means. Except for 4th (mutter grumble).

P

davidw

I've got a Nissan 200SX and notice a similar effect when driving in hot weather.

Being non techincal I could be talking complete garbage but I've always understood that a Turbo responds better when the weather is colder because cold air is being forced into the turbo gives greater power. (Is this what the intercooler does?)

The air con also use up some of the power but not sure if this has a noticable effect on performance.

I always seem to have much more power when it's icy although RWD, ice and more power is not a good combination.

Steve Perriam

u mean we dont all work in IT ?

i thought this was 'own a scoob and work in IT only BBS'

well at least if switching it off dont work we can always blame Bill

happy switching !!

DavidRB

Right, this is how I understand it, errors & ommissions excepted!

As with most things in engineering, more heat is a bad thing. Cold gases are more dense than hot ones, so an engine cylinder full of cold fuel-air mix has more molecules than a hot one. The more fuel in the cylinder, the bigger the bang & the greater the torque output.

Turbo chargers work by compressing the air before it enters the engine, thus increasing its density:



The side-effect of the compression is that the temperature of the air goes up (Boyle's Law, used to great effect in all refrigerators). This increase in temperature works against the compression, reducing the air's density. Thus, turbocharged engines have to cool the compressed air between the compressor & the engine. This is achieved using the Intercooler, which in simple terms is just a radiator that gets rid of the excess heat before the air finally enters the engine.

*Deep Breath* So, the hotter it gets, the worse things get for a turbo charged engine.

This is why we had a long thread on

Rum*

Yikes ....Dave....now thats what I call to the point....nice little diagram.....just wish I understood it tho?!!!

DavidRB

It makes more sense when you don't miss out a double-quote the first time around!

DavidRB

Rum*, what bit doesn't make sense?

GranTurismo

Hmmm,

Does this indicate a weekness in the scooby ECU?

Air temp affects density, hence Oxygen for combustion, this will limit power and decreace compression/boost and stuff. Most ECU will retard the spark (retune the engine)to get the best compression autmatically, however these posts indicate that the scooby cant cope on a hot day and the fact that you "need" to do the fabeled ECU reset if you move to unleaded indicates an average reading over time rather than an "instant" re-tune.

Thefore if it suddenly gets hot like this weekend then you car will run poorly for a while untill the ECU adapts to the climate??????

KevinW

ROSS,

Perhaps the lack of polish on your car caused massive drag, or maybe it just didn't fancy going through the car wash with all other ordinarymobiles

Kev

Formula1

I guess I will have a go at this!

Turbo- compresses air to a predetermines pressure before it is forced into the combustion chamber.

Basic rule- The more air = more burned fuel at one time = more power.

What part of the air is used to burn the fuel- oxygen. When the air is cooler there are more oxygen molecules per volumetric area- therefore more power is made.

intercooler- after the air is compressed it is super heated therefore there is less oxygen in this compressed form than there should be- inttercooler cools it down , so in essence compressing it more!

Nevertheless- The problem that has occured is not the cooling problem- it wouldn't be that drastic because if the turbo is functioning properly, you should still have the same volume of air forced into the engine each time!-

My theories- 1. Turbo is malfunctioning
2. Air fuel mixture was wrong therefore since it was hot outside- could have gone a lean-run- timing was retarded to keep from knocking
3. wastegate or bov malfunctioned by releasing all the compressed air!

I hope this made sense and it helped you out!

John

ROSS

Thank you everyone for your help. At the moment I must say I like KevinW's reply the best ,knowing little of the strange workings of the ECU although suspecting from what I have followed here that its only purpose is to destroy the cars performance and blow the engine up in various ways I will now adopt a far more logical approach perhaps others should try this as well to get a statistically objective set of repeatable findings. I propose to poke a fishing rod out of the passengers window so the tip protrudes at least a meter beyond the bonnet and dangle a tin of Carnauba Wax in front of the car. This is clearly the road ahead for performance enthusiasts and I am expecting to see at least 3 seconds off the 1/4 mile
What do you think Low 10's probable...LOL

ROSS

Thank you everyone for your help. At the moment I must say I like KevinW's reply the best ,knowing little of the strange workings of the ECU although suspecting from what I have followed here that its only purpose is to destroy the cars performance and blow the engine up in various ways I will now adopt a far more logical approach perhaps others should try this as well to get a statistically objective set of repeatable findings. I propose to poke a fishing rod out of the passengers window so the tip protrudes at least a meter beyond the bonnet and dangle a tin of Carnauba Wax in front of the car. This is clearly the road ahead for performance enthusiasts and I am expecting to see at least 3 seconds off the 1/4 mile
What do you think Low 10's probable...LOL