Turbo Elevation Question

[ippielb]

Posted this on snowest but i thought i might have better luck here with all the folks in alberta traveling from home to the mountains with their turbo's.


So, i have a question about elevation when running a turbo.

Ambient pressure at 7,000 feet is 78kpa(11.34psi)
Ambient Pressure at 1,500 feet is 96kpa(13.91psi)

Turbo's pressure the cylinders with compressed air, so mine pressures to 7psi, does this add on top of the ambient pressure? So at 7k feet it would be 18psi, and at 1.5k feet it would be 20psi? Or does the turbo compress to a set pressure regardless of ambient pressure? I am confusing myself with this and would like someone to help me with understanding this.

I'm wondering what fuel i have to run in comparison between the two. I have my heads machined to run AV gas at 7,000 feet at 7psi. If i come down to 1,500 feet, what fuel will i need to run at home to get it on the dyno? I want to bring out my Land & Sea Dyno for the first time and put my sled on the dyno to break it in, and to give it a tune.

 

[DaltonW]

i am not sure about the ambient pressure question. As far as your fueling, If your on the dyno, better safe then sorry, get some c111 or c116. JMO.
If your planning on tuning this sled in, from the info I have gotten from boondockers on my kit is, tune at elevation you normally ride with the fuel you normally run. Don't tune your sled in at 1500' on race gas, then take it to the mountains at 7000' with av gas and expect it to run the same.

 

[ippielb]

That's what i was hoping is that i could tune it at home here and have it good in the mountains, but i see that was foolish. I guess now i want to get it tuned in a bit back here at home on the dyno in a controlled area, so i have a base tune ready for the mountains. How do people dyno tune turbo'd sleds to get them dialed in?

I have a bucket of 110 here, do you think i need more octane then hat?

 

[DaltonW]

I don't think your going to be way out on your tune if you do it at home, I just mean dont spend days tuning at 1500 and go to 7000 and change a bunch of variables and expect it to be spot on. I would tune it in and then you would have less to to at elevation. give your turbo kit guys a call and they should straighten ya right up.

 

[orange stealth]

Tune it to high elevation and then dump some race gas in it for at home. Mine is bang on no tuning needed

 

[ippielb]

I don't think your going to be way out on your tune if you do it at home, I just mean dont spend days tuning at 1500 and go to 7000 and change a bunch of variables and expect it to be spot on. I would tune it in and then you would have less to to at elevation. give your turbo kit guys a call and they should straighten ya right up.

Okay, that's a bit comforting. I have never used my dyno before, and it will be new to me, as are turbos. It will be a learning experience. I wish i had someone to call for my turbo kit, but my sled is an odd ball. It is a 700cc with a D&D BB800, and i made myself a turbo kit using an aerocharger 53 turbo. So there's really no one to call who's done this before.

Tune it to high elevation and then dump some race gas in it for at home. Mine is bang on no tuning needed

One problem is i live 9 hours away from the mountains, so tuning at the higher elevations, i better hope the sled doesn't have any hiccups as it's never been run with the new motor i built, with the lightened crank, RKtek head, and the blow off valve.

 

[DaltonW]

What controller you running. Arctic Edge has been helpful for me. they know there sh*t in there and should be able to help you out if your really lost.

 

[ippielb]

I have an attitude fuel box. I will look up them tomorrow and try and give a call. I will also try an give rktek a call since they machined the head domes for me.

 

[DaltonW]

due to the fact its a custom kit, I dont know how much help there gonna be. My suggestion would be to get REALLY familiar with your fuel controller and just dial it in yourself. probably gonna be slow process. I don't know much about the altitude box's. Hopfully there not to bad to work with. EGT and Air fuel guages will help you as well.

 

[CamoKVF700]

I can't remember the formula I was given but I have a turbo quad which I get 24 lbs of boost out of at sea level and 18 lbs at 5000 feet in the dunes. All I do is jet it differently for 5000 feet. (It's carbed) So If you're EFI, it'll compensate for altitude. You won't need to change your fuel for altitude as it will build less boost up there. A turbo is a compressor and will only multiply boost by the quality of air it is given.

Sent from my SGH-I337M using Tapatalk

 

[ippielb]

due to the fact its a custom kit, I dont know how much help there gonna be. My suggestion would be to get REALLY familiar with your fuel controller and just dial it in yourself. probably gonna be slow process. I don't know much about the altitude box's. Hopfully there not to bad to work with. EGT and Air fuel guages will help you as well.

It's worth a try i guess, i have the manual for my attitude fuel controller, i have went through it and plugged it in to play around with it. I do have EGT gauge and an AFR

I can't remember the formula I was given but I have a turbo quad which I get 24 lbs of boost out of at sea level and 18 lbs at 5000 feet in the dunes. All I do is jet it differently for 5000 feet. (It's carbed) So If you're EFI, it'll compensate for altitude. You won't need to change your fuel for altitude as it will build less boost up there. A turbo is a compressor and will only multiply boost by the quality of air it is given.

Yes, the sled is EFI, that sounds promising. Guess the only way to find out is by giving it a go. I did get a PM from Aerocharger Jerry recommending me not to use my turbo on my sled anymore as it's too small. So i'm kind of in a pickle.

 

[CamoKVF700]

It's only too small if you're not getting the boost you want. Too big and it'll give you boost but not the responsiveness you might want.

I have a GT25 on an 800cc and is fine when moving. Out of the hole I use nitrous to light it up. Lol

Sent from my SGH-I337M using Tapatalk

 

[oly]

Do your self a favor and get a boost it box or boondocker box! I have played the areocharger game with those dobak boxes! And alot of helicopter rides out of the alpine I would definitely give Brent a call at arctic edge motor sports or even Dean at Mad motor sports a call on this. What ever it takes for wiring especially on your situation I would try and get a boondocker then you can play with every lil detail with tuning.

 

[ippielb]

I had a boondocker box but a non turbo model, i liked how it was set up. The tuning was fast and easy, very easy to understand, i also liked how you can plug a 9v battery in to change settings. I have never seen a boost it box. Anything that works on the earlier m8's will work on my sled. Only that that would need to be changed is the pins for the injectors if anything.

Only wiring that i may need is how to rig up a reliable 12v DC system, i bought a battery but it adds a lot of weight, and i dont have electric start so no point in having it right?

 

[samsquatch47]

Posted this on snowest but i thought i might have better luck here with all the folks in alberta traveling from home to the mountains with their turbo's.


So, i have a question about elevation when running a turbo.

Ambient pressure at 7,000 feet is 78kpa(11.34psi)
Ambient Pressure at 1,500 feet is 96kpa(13.91psi)

Turbo's pressure the cylinders with compressed air, so mine pressures to 7psi, does this add on top of the ambient pressure? So at 7k feet it would be 18psi, and at 1.5k feet it would be 20psi? Or does the turbo compress to a set pressure regardless of ambient pressure? I am confusing myself with this and would like someone to help me with understanding this.

I'm wondering what fuel i have to run in comparison between the two. I have my heads machined to run AV gas at 7,000 feet at 7psi. If i come down to 1,500 feet, what fuel will i need to run at home to get it on the dyno? I want to bring out my Land & Sea Dyno for the first time and put my sled on the dyno to break it in, and to give it a tune.

You are correct on the ambient pressure, except that temp also affects the pressure reading as well as what type weather system (high pressure, low pressure) is passing through the area at that given time. Anyway our boost gauge we use on our sleds and tire gauges we use to measure tire pressure read "0" at rest when at fact they should read 10 or 12 or whatever the ambient pressure is at that place at that time. But this would over complicate simple tasks like checking tire pressure, because then we would have to always subtract the ambient pressure to find out how much air in our tire. All of our gauges (except aviation manifold pressure gauges and altimeters) read zero when not under pressure or vacuum. So that 7psi your seeing on your boost gauge means your turbo is pressuring up the engine to 7psi over the ambient pressure. Unless you have an electronic boost controller you will have to turn up the boost controller to make the same hp at 7000ft as your sled did at sea level or 1800 feet or whatever you are at home where it was set. A manual boost controller is just that "manual". It won't compensate for hp loss due to altitude. It will just make the waste gate dump exhaust after the set pressure is reached. I don't know the exact math but if you were set up let's say for 200hp at sea level and then went to 10,000 feet with a manual boost controller you would have to adjust the boost controller to let's say 10 to make up for the loss of air density at the higher altitude. MCX turbo kits have a fancy electronic boost controller and altitude compensater that will automatically adjust boost to give a desired HP no matter what altitude or outside air density. My friends 270hp MCX Nytro would run at 10-13psi here at home at 1800 feet and we've seen up to 18psi at altitude in McBride. Unless your heads are really high compression you should be able to run more then 7psi at 7000ft with straight av gas. I run 10-12 at 6-9000 ft around vale and McBride on straight av and that's with a bikeman head and I don't have the low compression turbo domes. No signs of detonation on my 12 TSS M8 at all.
Just to be safe also run av on your dyno at home. Detonation is the number one killer of turbo sleds so it's really not worth the couple extra dollars to do a dyno pull. It will make sure you will be safe even if your boost controller messes up or the waste gate sticks and can't dump fast enough if you load it too hard on a dyno pull.
Was just bored reading old posts, hope this helps clear things up.

 

[samsquatch47]

Oh one more thing... The attitude box does not compensate for altitude. You most likely might have do some tuning on the hill. Whatever "tune" you make will only run that good at that altitude and temp that you made it at. Turbo sleds aren't as finicky as carbed sleds to altitude change, but expect to tune regularly to get peak performance at various riding areas and altitudes. This is why lots of guys run the Boost-it fuel systems that have baro sensors to adjust the fueling. It just adjusts the set point at which the injectors add fuel, when your engine just starts to build boost. Thats where you'll get a gurgle or bog on a system that can't adjust itself. Usually your wide open settings stay the same, it's all about getting the idle-mid range running crisp. That's what's hard to do on a 2strk turbo.

 

[ippielb]

You are correct on the ambient pressure, except that temp also affects the pressure reading as well as what type weather system (high pressure, low pressure) is passing through the area at that given time. Anyway our boost gauge we use on our sleds and tire gauges we use to measure tire pressure read "0" at rest when at fact they should read 10 or 12 or whatever the ambient pressure is at that place at that time. But this would over complicate simple tasks like checking tire pressure, because then we would have to always subtract the ambient pressure to find out how much air in our tire. All of our gauges (except aviation manifold pressure gauges and altimeters) read zero when not under pressure or vacuum. So that 7psi your seeing on your boost gauge means your turbo is pressuring up the engine to 7psi over the ambient pressure. Unless you have an electronic boost controller you will have to turn up the boost controller to make the same hp at 7000ft as your sled did at sea level or 1800 feet or whatever you are at home where it was set. A manual boost controller is just that "manual". It won't compensate for hp loss due to altitude. It will just make the waste gate dump exhaust after the set pressure is reached. I don't know the exact math but if you were set up let's say for 200hp at sea level and then went to 10,000 feet with a manual boost controller you would have to adjust the boost controller to let's say 10 to make up for the loss of air density at the higher altitude. MCX turbo kits have a fancy electronic boost controller and altitude compensater that will automatically adjust boost to give a desired HP no matter what altitude or outside air density. My friends 270hp MCX Nytro would run at 10-13psi here at home at 1800 feet and we've seen up to 18psi at altitude in McBride. Unless your heads are really high compression you should be able to run more then 7psi at 7000ft with straight av gas. I run 10-12 at 6-9000 ft around vale and McBride on straight av and that's with a bikeman head and I don't have the low compression turbo domes. No signs of detonation on my 12 TSS M8 at all.
Just to be safe also run av on your dyno at home. Detonation is the number one killer of turbo sleds so it's really not worth the couple extra dollars to do a dyno pull. It will make sure you will be safe even if your boost controller messes up or the waste gate sticks and can't dump fast enough if you load it too hard on a dyno pull.
Was just bored reading old posts, hope this helps clear things up.

That answered exactly what i was after. It compresses 7psi over ambient pressure. I'm looking to have the sled set up for constant air pressure, non adjustable. I want to play as little with the fuel as possible and as much in the snow as i can. No worries on reviving an old thread, i'm sure anyone who has the same question will google it and it will bring them here. I have a thing of 110 that im going to run through the sled to put it on the dyno, tune it a little rich and then switch to av gas, better safe then sorry.

Oh one more thing... The attitude box does not compensate for altitude. You most likely might have do some tuning on the hill. Whatever "tune" you make will only run that good at that altitude and temp that you made it at. Turbo sleds aren't as finicky as carbed sleds to altitude change, but expect to tune regularly to get peak performance at various riding areas and altitudes. This is why lots of guys run the Boost-it fuel systems that have baro sensors to adjust the fueling. It just adjusts the set point at which the injectors add fuel, when your engine just starts to build boost. Thats where you'll get a gurgle or bog on a system that can't adjust itself. Usually your wide open settings stay the same, it's all about getting the idle-mid range running crisp. That's what's hard to do on a 2strk turbo.

Okay, thats good information i did not know that one. I will give it a base tune here back home and when i get to the mountains i will bring the fuel down a tad, get it set up at elevation and then not ride it back home, wont be able to use the power here, my 440 gets me where i want to go easily. I was looking at the boost it controllers but they no longer sell them for the arctic cats which is disappointing, i haven't been able to find a used unit either.

 

[samsquatch47]

That answered exactly what i was after. It compresses 7psi over ambient pressure. I'm looking to have the sled set up for constant air pressure, non adjustable. I want to play as little with the fuel as possible and as much in the snow as i can. No worries on reviving an old thread, i'm sure anyone who has the same question will google it and it will bring them here. I have a thing of 110 that im going to run through the sled to put it on the dyno, tune it a little rich and then switch to av gas, better safe then sorry.



Okay, thats good information i did not know that one. I will give it a base tune here back home and when i get to the mountains i will bring the fuel down a tad, get it set up at elevation and then not ride it back home, wont be able to use the power here, my 440 gets me where i want to go easily. I was looking at the boost it controllers but they no longer sell them for the arctic cats which is disappointing, i haven't been able to find a used unit either.

Call TSS (top secret shop) they build turbo kits for M8's using Neil's Boost-it system.
I'm sure they wouldn't have a problem selling you a boost-it system. Brandon Miku is the Arctic Cat contact at TSS. They could give you baseline settings in the box then you just have to tune it once the snow flys. Once tuned you'll have years of enjoyment.

 

[ippielb]

Any idea on how much one would cost? Even if they have a used one i'd take that not like a used unit wears out.