Boost myth that drives me crazy!

[CO 2.0]

While you all make good points I need to throw in my $.02. Your turbo has to work exponentially harder (faster rpms) at 10000ft to make the same psi levels as you would at sea level. The barometric pressure, air density, etc is lower at elevation so HP will go down regardless if your NA or turbo. Turbo's DO lose less power than NA's at elevation. I know this because of the many NA and turbo'd cars I've personally dyno'd at sea level and 6000ft on the same dyno in the same temps. Not to mention how many times I've raced big HP V8 NA cars up here and smoke them with my 2871R 2.0T Audi where if I were at sea level it would be a much closer race. At 6000ft where I dyno I have been seeing that Turbo's lose ~19-22% depending on ambient conditions. NA's lose ~22-25% depending on ambient conditions. This is what my dyno research has shown on the matter compared to dyno's I've personally done at sea level on the same setup, same temps, same dyno, etc). Overlaying graphs and power curves. Ambient conditions play a big role in what you lose. My car makes 30hp more in 40deg than in 100deg just because of how dense the air is. Intercoolers need to be that much bigger up at elevation too since the thin air being compressed by the turbo is creating the air to be much hotter (also spinning the turbo harder) than it would at sea level in the same temps. Pressure at sea level is +/- 14.7psi (29.92 hg). Pressure at 10000ft is ~ 20.6 HG. Pressure decreases exponentially 0-5Kft, 5K-10K ft, 10K-15K ft and so on. Turbo's will work harder at elevation to make up for the loss in atmospheric pressure but their net loss is a tad less than NA. It's not the 3% FI vs 6% NA losses per every 1000ft gain in elevation like everyone has always said, especially since that scale is exponential.....but if I were to put it into those terms to 10K ft at most I'd say my research has shown more like 3-4% FI vs 5% NA. It's pretty close. Regardless forced inducted engines are the way to go at higher elevations. Be thankful you run those FI sleds in 30deg especially if you don't run a intercooler (which is the wrong thing to do). I'd hate to see what those egt's and iat's would be on a 100deg day lol... Also a good thing to do is check engine compression at sea level vs 5K ft. You will not be happy regardless of being NA or FI. I only bring all this stuff up because I have PERSONALLY gone out of my way to do extensive research on FI vs NA cars at sea level vs elevation. Not something I googled like a lot of people do on forums.

 

[Mountaintech]

A normally aspirated sled will lose about 3% per 1000'. If you are riding a turbocharged sled that is set for 10lbs. of boost at 1000' ,that boost pressure will decrease as you go up in elevation. Ask me how I know. A mechanical wastegate on its own cannot compensate for thinning air. I would start riding at 1000' and have about 13lbs. of boost, about 10 lbs. at 4500', and 7 lbs at 8000'. Now add a boost controller! As long as you can adjust your boost level you will not see HP loss at elevation.

10 lbs @ sea level= 10 lbs @ 10,000 ft.

 

[ReTodd]

The argument that a turbo'd sled doesn't lose power because of elevation compared to SC'd or stock sleds stems from the fact that even though you are losing power, your effective compression is lowered and you can therefore compensate by turning up the boost without detonating a piston.

As an example, if you normally get 240hp @ 10lbs at 4,000 feet and go to Wyoming and ride at 10,000 feet, you can turn your boost up to 12lbs and still get roughly the same hp to the track.

Rt

 

[Spur]

If your going to ride with the group I ride with you have to have a boosted sled. Some of the guys in the group don't really ride well enough to need a boosted sled but if they don't have one they can't get where were going. Some of the places we go to get off the beaten path do not require a lot of skill, they just required a lot of HP.

 

[0007]

K...........So

What yer sayin is
Turbo's make your air thicker?

CO 2.0, that was a good post

 

[A CAT]

Now back to the original question he had about 20% o2 at altitude is all wrong, yes the ratio will be close to the same but that has nothing to do with density, say you have a box of air at sea level, say you have 20 pices of o2 and 80 pices of nitrogen, that same box at 10,000 ft. will only have lets say... 15 pices of o2 and 65 pices of nitrogen,(the atoms are spred further apart from each other at altitude), so now throw in you're air fuel ratio of 12 or 14.7 to 1 and you are burning less fuel because of less o2, less fuel, less heat, less combustion expansion force=less HP

 

[happylilcuss]

I was not tryin to get anything started either. like I said was just venting a little. Obviously I am way off base so I will take a big ol bite off the humble pie!! Ride safe guys and girls!! Stay safe!

Again I wasnt trying to get anything started.. I admitted to being off base.. I took the bite of humble pie!!
However I am not wrong about there being less air at altitude. There is always 19-20% of O2.. You are right that it is the density of that air that makes a difference. That was the whole point I was trying to make.

I am really sorry if I offended anyone. It wasnt the intent. I was just venting and spoke improperly. Again I am sorry for upsetting everyone!!

Also I ride a turbo and am in no way trying to say that turbos do not lose hp. Of course they do. Only the turbo compresses or boosts the availble air making the engine feel like it is at a lower altitude. Thus causing it to lose hp at less of a rate than a na sled.
Again I am sorry for upsetting anyone!!

 

[snowblind]

way more that one in 50000 die on everest.

actually the everest facts websites says
"1993, 129 summitted and eight died (a ratio of 16:1); in 1996, 98 summitted and 15 died (a ratio of 6½:1)"

 

[skibreeze]

way more that one in 50000 die on everest.

actually the everest facts websites says
"1993, 129 summitted and eight died (a ratio of 16:1); in 1996, 98 summitted and 15 died (a ratio of 6½:1)"

I think that the point he was trying to make is that the 1/50000 ratio was strictly the bodies reaction to the reduced air pressure. Not dying from exposure/falling/avys/etc.

 

[AKtoad]

If you know why Joe Kittenger broke the sound barrier without an air craft and was able to accel. just under 900 mph then you will be able to understand why your sled loses HP boosted or not.

Just trying to stir the pot

 

[Rprecision]

I think things drifted away from the point made by happy in the first place.

Of course a turbo increases horse power and torque of any engine, and at any altitude. That increase will be the same roughly caompared to sea level vs. whatever altitude.

Happy's point, as I understand it is the "need" vs. "want" of a turbo to make up for poor abilities. Which if measured is probably true to a degree.

The one thing I wish was discussed here was reliabillity and longevity of a turbo sled. We have seen the fourstroke crowd (Not one of them) do some amazing things with both. When looking at a true backcountry sled, one has to consider these very carefully as it can be a long walk home!

 

[Mountaintech]

The one thing I wish was discussed here was reliabillity and longevity of a turbo sled. We have seen the fourstroke crowd (Not one of them) do some amazing things with both. When looking at a true backcountry sled, one has to consider these very carefully as it can be a long walk home![/QUOTE]

The 4 stroke turbos have been very reliable. I rode one for 5 seasons and it never let me down. The key to success is a well designed system and running the proper fuel and not overboosting. I logged 9000kms and sold it in great shape to someone who is equally happy with it.

 

[Adrenaline Revolution]

When I clicked on this thread I thought it was going to be about boost at idle.



Just stirring!