What could cause this? My EVT750+ is running better now that it is 98-102 degrees. It is super hot and humid so this does not make any sense. The car would normally have quite a bit of lag, especially when switching gears...all that lag seems to be gone now. It runs smoother, pulls stronger and the lag is pretty much non-existent. After owning several modified turbo cars, I have never encountered this. Any ideas? Too much timing? Fuel? Temp sensor? I will datalog soon but would like to get ideas of what to look at/for. Thanks!

 

well, my evt 775 is running kind of sluggish in this hot/humid temps.... it boosted way harder in the winter. says my BUTT-dyno.

 

Two questions:
1- Are you running mafless?
2- If so, was the car initially tuned during summer in similar weather?

 

I think my dyno is the same brand as yours and I agree. Colder temps equal less lag and quicker power delivery. Must be a NY thing?

 

Turbo cars loooooove cool temps - that's for sure. That is why I am absolutely puzzled by the behavior of mine...

 

The MAF is still in place.

EVT simply sent the tuning - the car was not dynotuned.

 

I would say it must be better fuel. Hard to explain otherwise?

 

yeah, makes no sense. took mine out last week for a good long drive and it was about 103F. car definitely felt sluggish compared to normal.

 

Theoretically what's happening is impossible. The reason cars produce more power in colder weather is because colder air is more dense, and contains more oxygen. Dense air, more oxygen, better combustion, more power.

Sounds like you might have gotten a good batch of gas, or your mind is playing tricks on you.

 

I know it does not make any sense, in theory. The car has been sitting for a couple of weeks (been out of town)...same gas it has had (93 oct) for a while.

If the ECM was pulling timing from the car, say to prevent detonation...now that the air is less dense, thus less oxygen, could it be that the computer is thinking that it is ok to add timing...hence the car running better? Similar to when the car does not reach optimum temperatures...how the ECM holds things back a bit...?

I am thinking out loud. Nothing out of this makes sense.

I am trying to think if my recirculating valves were not fully operational while it is cold...and somehow now, that it is extremely hot...somehow, they are...? This is bugging me...

 

Maybe it has something to do with the summer blend. My understanding is that gas sold during the summer has to have a lower vapor pressure (for smog purposes) and that changes how the fuel is produced and is why it historically costs more for the summer blend over the winter blend. But, I have no idea if that change actually affects the energy content of the gas.

A quick google search turned this up:

http://www.examiner.com/global-warmi...e-of-the-blend

 

Another thought is that when it is hotter, your car will run richer.. Hot air is less dense than cold air, therefore there is less oxygen in hot air.. if the tune/fuel system does not make the appropriate adjustments, then your car may be getting a richer AF mixture.

I had the exact same issues on my 500+ HP 944 Turbo.. In really cold weather, I could actually hear the car detonating because it ended up running too lean. In the summer time on hotter days, I could see black smoke from my tailpipe as the Car ran too rich.

Just a thought...

 

I don't think you're going crazy. I've encountered the same experience on the odd day during the summer months. For some unbeknown reason the car feels like its lighting fast....so electric, and in uncanny heat only to find the following day its a completely different story....so its not fuel. It's weird. It must have something to do with barometric pressure....thats all i can put it down to. Then equally i've had the odd day when its sub 10C and the car feels unresponsive for no apparent reason at all when it should be smokin fast ballistic. Weird.

 

I would bet on fuel quality. I have run my tuned TT at the track a few times where the car felt a bit sluggish or would hesitate slightly. Dropping in a couple gallons of 104 wiped that sluggishness away immediately. The ECU's on these cars are very sensitive to fuel quality in that a tuned turbo is running much closer to the limit as far as timing/boost/EGT than a stock turbo. The ECU will quickly pull timing and boost to keep the car safe. You can quickly resolve all that by adding some race fuel. Our cars are fuel snobs!

 

I hear ya totally with the fuel but the strange thing ive found is that on the days it happens out of nowhere i'm running on the same tank of gas.. It really gets mewondering what what on earth causes it..its so strange. Then the next day, same gas, its nowhere near as electric. I usually look at the weather details such as pressure, humidity temps etc to try and get a handle on it. Im sure its not mood related.