1.3 - 1.5? Is this just a tune or do you have supporting mods or running race gas?

 

0.7 for stock k16 but it can have spikes 0.8-0.9 and 0.7 is normal for a stock k16 and not low.

 

What effect does altitude have on boost? I'm just under 5k feet.

 

Hi,You didnt say if you had K16s or K24s.....K24s go a little higher in boost

 

Hi,The higher the altitude the less atmosphere pressure to help in a sense as to act like a at higher boost helper,,in a small way,,which does have a slight effect know matter if our cars have sensors and controllers.....Plus the air gets thinner the higher the altitude which makes less efficiency/less power...You can relate this to us as far as hiking in the mountains as compared to walking on the salt flats,,,,Which place makes it easier for us to walk with out getting tired faster??....Hope this helped......

 

Hi,You are talking about non-stock turbos??..Also,I hope you have race fuel in there at 1.5 OR and another pump to feed your bigger injectors.....Just my opinion....

 

I think what he's saying is that while High altitude will reduce the efficiency of NA engines (due to lower atmospheric pressure), the effect is negligible with turbo cars. In fact, you MAY see a HIGHER boost reading to compensate for the reduced partial pressure of O2.

but the drop in engine output will be met by a commensurate increase in boost pressure.

 

For all intensive purposes, altitude will not have a noticeable effect on our cars as the altitude where our turbos will maintain max specified boost is much higher than 5000 feet (in aircraft terms this is called the turbos critical altitude and is the altitude there the wastegates are fully closed and the turbo can no longer maintain rated boost due to the air being too thin). The one thing that does happen with increasing altitude is also the fact that cooling is diminished due to the thinner air. With aircooled turbocharged aircraft piston engines you will often run into overheating issues at altitude due to the thin air even though the outside air temperature may be well below freezing. Once again, in our cars this is not much of a factor since we are liquid cooled but the thin air does have a diminished cooling effect on our intercoolers. Finally, higher altitude thinner air will offer reduced air resistance partially allowing an object, in this case our car, to travel faster. This effect is also relatively small.

 

I am also at a higher altitude. At higher altitude you will see the same boost levels but your turbos are working that much harder to get you there, as the air is thinner.

When your turbos are working harder than normal they can get outside of their efficiency range which means hotter IAT's (charge temp). However I wouldn't be worried about your stock turbos being outside of efficiency range at your altitude unless you have an aggressive tune.

 

Also at higher altitude, the effective fuel octane rating is higher.

 

for normally aspirated cars, not turbo......

 

Well I took it to Porsche and they checked my boost against what it should be for the chassis number and they said it is spot on. Any ideas? Here is a video of it boosting in action:

(Click the image below to see the video)

 

What does checking against the chassis number do? Even for a non-X50 car, the number seems low under nominal conditions.

 

Huh? whether it is turbo or not has nothing to do with it. This a characteristic of fuel at altitude only.

Edit - more a characteristic of combustion than the actual fuel. While I understand that a turbo at altitude is still compressing the air into the motor, the overall affect due to the pressure difference will still have the effect of a higher octane fuel.

 

No idea, I suppose that they meant they looked up the normal tolerances for my car and used the chassis number to find these.

The boost seems low? I thought if anything it would be high given most people say 0.6 or 0.7 and I am generally seeing 0.9 constant boost figure.