Losing performace in the hot weather?

[20Vcqdriver]

Know it is normal to loose a bit of performance in this hot weather but how much is normal.
40-60 in 3rd has now dropped from 2.4sec on a cool evening a few weeks ago to 2.7 today. And in 4th 50-70 was 3 sec now 3.5secs. Seems a lot but as this is the first hot weather spell I have driven in with this engine I am not sure what to expect?! Certainly very noticable though.

[s2driveruk]

totally correct, hot temps equal some drop in performance. best performance will be on cool misty mornings i bet you Having said that if the chargecooler is doing its thang then in theory it should be able to overcome much of the increased intake temps as in effect the turbo is compressing (i.e. further warming up) the already hot air on intake.

[philKS2]

Wowwahhh...!! hang on 20vcgdriver !!!

Who is driving around measuring thir 40-60 speeds that accurately anyway??

[EspenW]

Yep, hot intake temps will have a massive effect. This is why open cone filters end up costing serious power on most setups.

On a crisp, 3C, overcast fall day, with 50% humidity, the dyno correction factor is 104.1, so a 300hp car will produce 312hp

On a 30deg ambient day like today, where temps in the sun easily can top 50C, the dyno correction factor is 88.5, so our 300hp engine only produces 265hp (in the sun)
In other words, it pulls almost 20% harder on the overcast 3C day than on the sunny 30C day.

Temperature sensitive ignition timing or a car that is right on the border of knock will produce even larger variances.

Summer temps really suck when it comes to engine performance. I prefer cool fall or spring evenings when the roads are dry. Winter temps produce more power, but the car starts going sideways and stuff when the asphalt gets too cold:mischeif:

[BrianSmith_S2]

For some strange reason i was shocked to see 21 psi on my gauge last night on a warm evening 5th/6th gear run up the A3.

For over a year now 18 psi has been the limit

So guessing the heat has sealed a small boost leak or has got to the ecu

Brian

[Rusty]

No Brian, that's the ABY temperature compensation working... It robs you of 3PSI in the winter and gives it back in the summer

[Fat Audi 80]

I have no idea what mine is boosting to, but it was STILL bloody fast when I went out on Tuesday night and not much kept up with me bar a brand new Porsche Turbo! (And he didn't get away too much either. )

[driftin jo]

The standard set up is designed to give the same power whatever the temp so that's why you get less boost in the cold and more in the hot weather.
There is however a bit of a problem with a chipped car,as you are now running the turbo close to what it can do the efficiency is down and the air temps are up so as the ecu tries to compensate for increased temp to make the same power by increasing the boost and it all goes wrong, the the output temp is too much for the intercooler to cope with and the ecu has to retard the ignition to prevent knock, this then costs you a lot of power.
There is plenty of overhead in the k24 on a standard car that has not been chipped so this is not a problem.
If your car has not been chipped you should no see much performance loss in the heat.
In Thierry the standard set up should be able to make full power at 45 deg , and it does not get that hot in the UK , I know in the real world there will always be a little less power on a hot day but a standard car should no suffer much .
I never lost any power, well not that was noticeable, in the summer before my s2 was chipped.

[20Vcqdriver]

Wowwahhh...!! hang on 20vcgdriver !!!

Who is driving around measuring thir 40-60 speeds that accurately anyway??

Took an accurate set of readings for the Audi Driver mag over several days several weeks ago. Driving in this heat over the last 2 days in particular I felt a noticable drop in performance so took some 'new' times today in 27-28 degree heat.

[max_s2]

Btw, does anybody know how VEMS can be configured to know when to retard ignition on each +10deg temp?

[20Vcqdriver]

For some strange reason i was shocked to see 21 psi on my gauge last night on a warm evening 5th/6th gear run up the A3.

For over a year now 18 psi has been the limit

So guessing the heat has sealed a small boost leak or has got to the ecu

Brian

Mine still pushes out 1.25bar, same as always on Pauls homefry (should be 1.4 but think present exhaust stopping it going higher, to be sorted in 10 days time:mischeif

[EspenW]

One thing that I forgot to mention is that on a turbo car, hot weather makes more of an impact than on a NA engine, since the lower exhaust volume produced in hot weather makes the turbo spool later. This means less torque and lower G's pulled. Thus, in a turbo car, heat affects torque even more than it affects hp.

[T2Andy]

Thats just how my car feels at the moment

[S2central.net]

For some strange reason i was shocked to see 21 psi on my gauge last night on a warm evening 5th/6th gear run up the A3.

For over a year now 18 psi has been the limit

So guessing the heat has sealed a small boost leak or has got to the ecu

Brian

Brian - you need a V-stream to counteract the bonkers behaviour of the ABY... Then you'll see 21psi in the winter as well

[S2central.net]

Hot air also affects the amount of ignition advance that can be dialled in... essentially the timing has to be retarded in hotter air so as to avoid knock - that is most certainly being felt in the butt dyno of the 3B - this is where really good intercoolers pay for themselves - or water injection systems... to keep temps down.