Question about elevation

[theinsider]

So last week we borrowed a friend's 2014 GTI SE and brought it up to Lake Tahoe. For those who don't know, the elevation in Tahoe is nearly 7,000 feet. Long story short, the performance was awful... about as bad as anything I've ever ridden. It only had about 65 hours on it and our friend swears he just had it tuned up before we borrowed it.

While we were up there, someone overheard us talking about it and mentioned that it might be the elevation that's affecting the performance. Is this possible and to what extent? If that's the issue, can anything be done to compensate for it?

 

[jammin777]

where i ride near home is 2200 ft and where i camp is 5000 ft in elevation and there is a huge difference so i could only imagine 7000 ft would make it feel like a barge. i lose about 3 to 4 mph between the two elevations and takes a longer to get there.

 

[Coastiejoe]

Vehicles have had this issue for years. In the late 70's Ford came out with a Barometric sensor that would correct things based on atmospheric pressure. The funny part with that was, it only took a reading when you started the vehicle. So if you started it and then drove for 1000 miles, it would never take a reading again. You have to stop, turn it off, turn it on and it would read the pressure...

That said, I have no clue how Seadoo corrects this. But I will do some digging as I am curious...

Here is the Ford switch

 

[Coastiejoe]

It does have one,,,

MAPS, (Manifold Air Pressure Sensor). Also referred to as, APS (Air Pressure Sensor) or (Atmospheric Pressure Sensor).

If they are out of range, they can/will throw a code and normally will not operate as designed. They WILL use a generic default average when they are bad.

However,,,, to be out of range (defective) is pretty unusual as the normal range covers several thousand feet. So,,, it can be bad and NOT really be bad...

Make sense?

 

[Coastiejoe]

Here is the Seadoo version.

Sent from my iPhone using Tapatalk

 

[theinsider]

where i ride near home is 2200 ft and where i camp is 5000 ft in elevation and there is a huge difference so i could only imagine 7000 ft would make it feel like a barge. i lose about 3 to 4 mph between the two elevations and takes a longer to get there.

Yeah it never would go past 35 MPH and took a good 8-10 seconds to hit that. It was also louder than any jet ski I ever heard- we could hear it from over 200 yards away. Normally I would just assume it was a poorly maintained PWC but it has less than 100 hours on it and our friend just had it serviced.

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Interesting thoughts Joe. I'm really interested in figuring this out because we would like to borrow it from him again to avoid renting but the ride was so poor that it was like a moped vs. a motorcycle.

I forgot to mention that we rented a 2015 GTI (about 35 hours on it) from one of the marina's to have two jet skis out there and the difference in performance was night and day. There's obviously some kind of adjustment that people up there with jet skis and boats make but I have no idea what it is. The rental people weren't really sure either as they have all the work done by a mechanic but said it could have something to do with the carburetor.

 

[Coastiejoe]

I would ride the ski you borrowed in the "normal" area that the ski is kept. If it rides great, then I would change the sensor. My best guess is, it is not out of range but not accurate to the higher elevation.

 

[pvamax]

You lose ~3% of your hp per every 1000ft elevation gain. So a 155 ski is down about 33hp at 7000ft vs sea level. Not sure where you are used to riding but thats a big drop if you come from the coast.

Might be a bad plug if its running like garbage compared to the other gti though. Simple fix and despite it's recent tune up, plugs can foul early in their life on occasion.

 

[theinsider]

You lose ~3% of your hp per every 1000ft elevation gain. So a 155 ski is down about 33hp at 7000ft vs sea level. Not sure where you are used to riding but thats a big drop if you come from the coast.

Might be a bad plug if its running like garbage compared to the other gti though. Simple fix and despite it's recent tune up, plugs can foul early in their life on occasion.

Yeah like I said I rode a GTI that was essentially the same and it ran great. I've been riding up in Tahoe for several years and never had any issues with rentals. This was the first ski I rode that we brought up there

 

[Mike99]

Does your friend's ski have fresh gas? It's too new to have carbs, right?

Mike

 

[ski-d00]

Something was wrong with it. It should run fine in all elevations. Were you using the green key?

 

[theinsider]

Something was wrong with it. It should run fine in all elevations. Were you using the green key?

Nah we were definitely using the right key. Something was wrong with it for sure but it's just odd because as I said, it was serviced before we borrowed it and it's not that old.

 

[AircraftDoc]

Unless it supercharged, YES it will affect it.
I fly at 12,500 and I set the mixture. Even though I lean out the engine and have electronic advanced spark, I loose lots of power. Even more so on when the temp is higher than normal. This is called density altitude. Even though everything is tuned, no turbo = no power.

 

[jammin777]

as in the elevations mentioned above, i loose 4 mph top speed at 2200 to 5000 ft asl. and takes a little longer to get there but its is not drastic. in your case it almost sounds as if the learners key is being used as it tops out at 35 mph and takes a longer time getting there. in most cases if a ski or boat lives in the higher altitudes all the time then they are usually re-propped to gain some of what is lost.

 

[ski-d00]

It sounds like you were running on 2 cylinders like a plug wasn't firing which is common on the 4tecs. Even new plugs can be faulty right out of the box. Did you ever get short bursts of what felt like full power? This is a symptom of a plug going out.

The 4tecs are pretty smart motors that sense and adjust for atmospheric changes so it should never run poorly like you describe. You will lose some speed and acceleration at higher altitudes due to the thinner air but it still should run fine. These aren't the motors of old with carbs that had to be re-jet for every altitude change.