Dyno Results at Altitude
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Dyno Results at Altitude

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    Default Dyno Results at Altitude

    I just got the results back for my Gale Banks TT BBC from the dyno shop in Greeley Colorado. Actually, he left a message yesterday explaining that it didn't produce the 700 to 750 horspower I was excepting. That's because it made 853 HP at 5500 on pump gas! Naturally, I was stoked! After calling all my buddies with this wonderfull news, I headed down to pick it up. After a some chatting on a few issues, he handed me two dyno sheets. The first being the the one that was corrected to sea level showing the marvelous 853, and the second, at 4500 feet, showing a very dismal 667. WTF!! I couldn't believe the difference! He told me you lose around 25 percent at this elevation. I thought being force induction, that would take care of some of that difference. Any thoughts????????? Guess I'll just buy an impeller for the realistic horsepower and if anybody asks, I'll tell them "853 HORSEPOWER". LOL!

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    sounds like bs... the calculator for a N/A motor says loss is 120 hp at 4500ft..your turbo should lose less since you can safely runs a little more boost to compensate for the altitude.... I can tell you this...our turbo motors (not in a boat) have a limit of 14.5 at sea level, set by the ecu..when I go to 5000 ft I can get 18lbs before the ecu cuts spark...and it feels like we have more power at 5k than at sea level..

    maybe he was adding in some temprature diffs as well..
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    Well at the top, he has the Standard Corrected Data for 29.92 inches Hg, 60 F dry air. These guys are good and he told me that just the way it is. Hell, I'm going to lose more with another 700 feet in Wyoming when I take it home! Don't make sense to me either but???

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    I rule of thumb for aircraft

    You loose 3 percent power N/A per thousand ft of alt

    You also have to figure density altitude into equation

    I don't know how you set up your turbo boost

    But I would think a good set up could produce much more then you have

    And hold that output as you go up in elevation
    If you ain't the lead dog the view is always the same !

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    Well, I bought this turnkey engine out of Havasu. I believe it's the old Stage 3 Gale Banks system that should put out 850 horsepower. It's the 454 kit with draw thru 750 Holley carbs into the Raajay twin turbos with the intercooler mounted on the intake carb flange. 7.9 to 1 compression with solid flat tappet camshaft designed for this system. With no wastegates, it has the orfice holes drilled into the exhaust side of the turbos. They are and were currently open, 3/8 tapped. Dyno guy says its boosting 12 pounds. It seems to me that it's right on the money if you use the sea level numbers. I just ca't imagine loosing that much for elevation?

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    Remember, your boost pressure is the differential of manifold pressure VS atmospheric. 12lbs up there is not the same ABSOLUTE pressure as sea level. Its 12 lbs higher than the surrounding atmospheric. So aside from the lack of oxygen, in the air, your actually dealing with less actual true pressure in the manifold at 12lbs there, than 12lbs at Long Beach on a killer 60 degree winter morning. If the atmospheric there is around 26.92, then your running 3 lbs less ABSOLUTE manifold pressure than the same reading at Long Beach on a bitchin day.
    Thats why BigMike58 says he can turn the boost up to 18 psi at altitude. Because the actual ABSOLUTE pressure is closser to his sea level boost.

    You may be able to plug the hole in the turbo to get a little more safely at altitude, but I would check with somebody that is familiar with thise turbos. Drop a PM to Hass828. He has messed with thise turbos some and seems to know them pretty well. It is a limited setup, and there may be a limit to how fast you can spin the things.
    The fact that it is a 850 HP setup, and it made 850 corrected tells you quite abit. But the correction is not that far out. We had a huge discussion about that on the site about a year ago as to whether some shops at altitude were fudging numbers. I don;t think thats the case here. Your losing a shit load at that altitude.

    You could get it all back, but you'll need turbos up to the task if you can't spin those faster.



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    Last edited by gn7; 07-14-2011 at 10:22 PM.

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    I see what you are saying. Most guys put pipe reducers in to 1/4 inch or even 1/8 inch to bump up the boost. But hell, I just picked it up from the dyno and don't want to send her back down there already. The dyno guy has her dialed in correctly now. He actually didn't have to do too much. Rejetted the carbs to 80 & 88 and bumped up the timing to 35 locked in. Oh, and put the correct sparkplugs in! He told she flat out comes alive at 3500 RPM and set my rev limiter to 5800. Will probably just buy the impeller for the true horsepower and run it. It's not like I have a race boat or anything.

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    Look at it this way jonnwald. Making an actual observed 667 HP at that altitude with a N/A would be a serious bitch, uphill all the way and cost some pretty serious coin. So you have a pretty decent package there. 667HP is nothing to sneeze at. And where your running it, it will be a serious piece.



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    This is very true. Thanks for cheering me up. Probably won't even get her installed this season as time is running out and super tied up at work. The thru transom exhaust is going to take some time to fab and need to go thru the pump and install some upgrades.

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    Quote Originally Posted by gn7 View Post
    Remember, your boost pressure is the differential of manifold pressure VS atmospheric. 12lbs up there is not the same ABSOLUTE pressure as sea level. Its 12 lbs higher than the surrounding atmospheric. So aside from the lack of oxygen, in the air, your actually dealing with less actual true pressure in the manifold at 12lbs there, than 12lbs at Long Beach on a killer 60 degree winter morning. If the atmospheric there is around 26.92, then your running 3 lbs less ABSOLUTE manifold pressure than the same reading at Long Beach on a bitchin day.
    Thats why BigMike58 says he can turn the boost up to 18 psi at altitude. Because the actual ABSOLUTE pressure is closser to his sea level boost.

    You may be able to plug the hole in the turbo to get a little more safely at altitude, but I would check with somebody that is familiar with thise turbos. Drop a PM to Hass828. He has messed with thise turbos some and seems to know them pretty well. It is a limited setup, and there may be a limit to how fast you can spin the things.
    The fact that it is a 850 HP setup, and it made 850 corrected tells you quite abit. But the correction is not that far out. We had a huge discussion about that on the site about a year ago as to whether some shops at altitude were fudging numbers. I don;t think thats the case here. Your losing a shit load at that altitude.

    You could get it all back, but you'll need turbos up to the task if you can't spin those faster.
    He can turn those turbos up to about 15-17psi depending on a few other variables , then he's out of turbo. But that should regain his lost hp. He will be at the limits of pump gas at 15psi though.
    I turned mine up to 25 psi a few times and tore up the turbos every time I did it. Actually had a turbo explode and an exhaust turbin exit the tail pipe. Knocked a hole in the pipe on its way out . Glad it didnt hit anyone as it left. Bad deal. 15-17psi max with those turbs.
    Last edited by Hass828; 07-15-2011 at 05:14 AM.
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    Quote Originally Posted by BigSteve View Post
    I rule of thumb for aircraft

    You loose 3 percent power N/A per thousand ft of alt
    that could be, but i don't believe it, especially when well over 500". i know what my engine turns at 500', what it turns at 5000', and what the hp curve looks like from the dyno, and what the hp drop shows on sleepers graphs. and i know the "numbers" would be different, but the "actual performance" would indicate the hp loss is nowhere near this number in my deal. BUT... i was told several years ago, by a pretty smart guy, that "bigger inch" engines do not seem to fall off anywhere near as much as smaller engines. at the time, he'd been running a 572 for a couple years, in d/a from 200' to 5500, and just didn't see nearly as much of an rpm loss compared to the old 468.
    are the applicable aircraft engines large or small?
    i do know that i've seen ob guys that could run under the number in kentucky/alabama, go to a race in marble falls where the air's a bit different and fall flat on their azzes, with no hope of getting remotely close to a number.


    Quote Originally Posted by Hass828 View Post
    He can turn those turbos up to about 15-17psi depending on a few other variables , then he's out of turbo. But that should regain his lost hp. He will be at the limits of pump gas at 15psi though.
    this is confusing - regain what lost hp??? if he could run it at 15, why not run it at 15 all the time??? kind of sounds like it's a lake boat and the engine is set up to live at 12. running it at 15 may not be the best thing for the engine? no one's really gonna know what's inside the thing until he breaks it. i say, just put a good pump behind it, and just go have fun with it.

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    Quote Originally Posted by bp298 View Post
    this is confusing - regain what lost hp??? if he could run it at 15, why not run it at 15 all the time??? kind of sounds like it's a lake boat and the engine is set up to live at 12. running it at 15 may not be the best thing for the engine? no one's really gonna know what's inside the thing until he breaks it. i say, just put a good pump behind it, and just go have fun with it.
    The hp loss that he started this whole thread about.

    Quote Originally Posted by jonnwald View Post
    I just got the results back for my Gale Banks TT BBC from the dyno shop in Greeley Colorado. Actually, he left a message yesterday explaining that it didn't produce the 700 to 750 horspower I was excepting. That's because it made 853 HP at 5500 on pump gas! Naturally, I was stoked! After calling all my buddies with this wonderfull news, I headed down to pick it up. After a some chatting on a few issues, he handed me two dyno sheets. The first being the the one that was corrected to sea level showing the marvelous 853, and the second, at 4500 feet, showing a very dismal 667. WTF!! I couldn't believe the difference! He told me you lose around 25 percent at this elevation. I thought being force induction, that would take care of some of that difference. Any thoughts????????? Guess I'll just buy an impeller for the realistic horsepower and if anybody asks, I'll tell them "853 HORSEPOWER". LOL!

    He's complaining about the loss from 853 at sealevel to 667 at 4500ft. All I was saying is that he could possibly regain the loss with a couple more pounds of boost when he goes up in elevation.
    Honestly sounds to me like the dyno operator has a happy correction fact to get the 853.
    Last edited by Hass828; 07-15-2011 at 10:40 AM.
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    Quote Originally Posted by bp298 View Post
    that could be, but i don't believe it, especially when well over 500". i know what my engine turns at 500', what it turns at 5000', and what the hp curve looks like from the dyno, and what the hp drop shows on sleepers graphs. and i know the "numbers" would be different, but the "actual performance" would indicate the hp loss is nowhere near this number in my deal. BUT... i was told several years ago, by a pretty smart guy, that "bigger inch" engines do not seem to fall off anywhere near as much as smaller engines. at the time, he'd been running a 572 for a couple years, in d/a from 200' to 5500, and just didn't see nearly as much of an rpm loss compared to the old 468.
    are the applicable aircraft engines large or small?
    i do know that i've seen ob guys that could run under the number in kentucky/alabama, go to a race in marble falls where the air's a bit different and fall flat on their azzes, with no hope of getting remotely close to a number.




    this is confusing - regain what lost hp??? if he could run it at 15, why not run it at 15 all the time??? kind of sounds like it's a lake boat and the engine is set up to live at 12. running it at 15 may not be the best thing for the engine? no one's really gonna know what's inside the thing until he breaks it. i say, just put a good pump behind it, and just go have fun with it.
    A large majority of na piston aircraft are in the ~540ci range. Even the smaller 4 cyl are ~360ci. Also remember that most piston aircraft engines operate at well under 3000rpm, ~3000 usually being max and are very low compression, max being about 8.7:1 for say, the Lycomong IO540 that makes 300hp @ 2700rpm.
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    I'm really having a hard time understanding why your dyno guy would have made such a crazy statement about a "potential" 25% loss in power.

    I pulled this from the BorgWarner site on turbo efficeincy/ loss of power at altitude..
    The high-altitude performance of a turbocharged engine is significantly better. Because of the lower air pressure at high altitudes, the power loss of a naturally aspirated engine is considerable. In contrast, the performance of the turbine improves at altitude as a result of the greater pressure difference between the virtually constant pressure upstream of the turbine and the lower ambient pressure at outlet. The lower air density at the compressor inlet is largely equalized. Hence, the engine has barely any power loss.

    I think the issue "from what I've read about your system" is the lack of having a closed loop system with that engine package. You should be able to run at 12psi at sea level and then manualy turn up the boost to 15psi at 5000' and see no loss in power.

    Why can't you run a manual boost knob on this system? like this? ( be forewarned--boost is addicting!! and it's real easy to reach down and twist the knob..I do it all the time!!)


    I also have a question about the lack of BOV or wastegate...What is used in this system to protect the turbo from compressor surge?


    Congrats on the 650+hp...wish I had that much!!!
    Quote Originally Posted by gn7 View Post
    zombie you are seriously one screwed up dude. Good thing you decided to be on welfare for a living. Because you are way to stupid to have made it in the real world. GN7-

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