Dmitri 1580rwhp Uncorrected...

JQmile said:
I think he went 158.XX, I was just rounding up...I also think the truck has to weigh 6000lb for Super Street right? I know what you mean about backing up crazy dyno figures with track times, but as it's been proven time and time again, there's a lot more than just horsepower that actually gets you down the dragstrip. Even if the number on the II drag truck was corrected by 20% (which is entirely possible), that's still stupid power.
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Yea, 158MPH is no joke! It legally has to be 5940lbs for SS. But for some reason they only weigh the trucks if a record is broken and backed up. I know what mine weighs, I know what Daniels weighs, what Robs weighs(they are all legal)and a few others, and I just don't understand understand how that thing can be that heavy. Just bed sides, no tail lights or anything. It's not really a big deal though. If they say its 6k I believe them it just looks really light.
 
If my turbo was in I would have been at that even such a bummer.
so I hope the dyno isn't an "easy" one because that's the one I'll be using hahahah
 
For the record, unless a dynos altitude correction factor is calculated specifically for turbocharged engines, then its got to be inaccurate.

I thought it was fairly well known, but turbo engines have minimal power loss at altitude once the turbo is spooled up.

The idea is, that a turbine/compressor will continue to spin however fast it needs to until it has the air pressure "load" it was designed for. And as long as manifold pressure is the same then an engine should make the same power.

Boost takes a big drop in supercharged engines at altitude. I've heard multiple times that turbocharged cars in nhra classes are almost as fast as the nitro cars when their both at altitude.
 
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ChargedTTQ said:
For the record, unless a dynos altitude correction factor is calculated specifically for turbocharged engines, then its got to be inaccurate.

I thought it was fairly well known, but turbo engines have minimal power loss at altitude once the turbo is spooled up.

The idea is, that a turbine/compressor will continue to spin however fast it needs to until it has the air pressure "load" it was designed for. And as long as manifold pressure is the same then an engine should make the same power.

Boost takes a big drop in supercharged engines at altitude. I've heard multiple times that turbocharged cars in nhra classes are almost as fast as the nitro cars when their both at altitude.
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This has always made me wonder as well. The turbocharger was heavily researched for aviation uses to maintain power. In fact the main reason turbochargers were researched so heavily over superchargers is the fact they could be used in aviation more effectively since they react to atmospheric changes and prevent detonation in a gasoline engine when a plane drops from 30k feet down to sea level where manifold pressure would change drastically with a static load from a supercharger.


"Due to the fact that turbine speed is largely determined by the pressure differential between turbine inlet and exhaust, as atmospheric pressure declines at higher altitude, the increasing pressure differential between the exhaustt manifold and atmospheric pressure at the turbine discharge tends to automatically compensate for reduced compressor efficiency with increased turbine speed, which, in turn, automatically increases engine boost pressure in the intake manifold to maintain power."


-turbocharging performance handbook by Jeff Hartman


Direct quote from a book that is coveted on this site. I purchased it because several members on here referred this book as a great turbocharging learning tool. Now is this false information or is there more to the story that we do not see?
 
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Altitude does make a difference in a max effort no boost limitation situation. Turbos that are boost limited via a waste gate will show little to no power loss as the turbo just works harder to maintain the same manifold pressure. Until the point it can't work hard enough.

The dyno correction math was based on NA and not turbocharged engines however, its way to favorable to a turbocharged engine for the altitude difference.

Now correcting while spraying nitrous.....*bdh*
 
Joesixpack said:
Altitude does make a difference in a max effort no boost limitation situation. Turbos that are boost limited via a waste gate will show little to no power loss as the turbo just works harder to maintain the same manifold pressure. Until the point it can't work hard enough.

The dyno correction math was based on NA and not turbocharged engines however, its way to favorable to a turbocharged engine for the altitude difference.

Now correcting while spraying nitrous.....*bdh*
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So in most cases using a correction factor is garbage. It depends too heavily on the scenario at hand. The only time it would come into play is on a complete max effort scenario where the turbochargers are overspeeding and unable to maintain boost with a surplus of fuel and no nitrous is used, correct? Of course this would assume the setup has proven itself at sea level and already has a set of so called "max effort" parameters it maintains at sea level but cannot maintain at heavy elevation. Otherwise the new setup on a dyno at elevation has no way of telling what boost it should see while at sea level.
 
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The only time I use a CF is if I am comparing dyno pulls on the same dyno but done on different days. To take elemental factors out of the comparison.

And yes using a CF while using a turbo isn't ideal, using a CF while using a turbo AND artificial air from a bottle is just, HUH???
 
Even using the same truck on the same dyno on different days makes you wonder why a cf is used. Any setup at any elevation is going to dyno different on 3 consecutive pulls. Using it to make the numbers look the same makes you wonder why they even dyno the truck? All they're doing is fudging the numbers to make them appear the same. Then that correction actor is really only good for that exact truck given different setups react to elevation differently.
 
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JQmile said:
I think he went 158.XX, I was just rounding up...I also think the truck has to weigh 6000lb for Super Street right? I know what you mean about backing up crazy dyno figures with track times, but as it's been proven time and time again, there's a lot more than just horsepower that actually gets you down the dragstrip. Even if the number on the II drag truck was corrected by 20% (which is entirely possible), that's still stupid power.
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The NHRDA race director told me after the event that pass wasn't accurate. He said nothing added up and the mph light hung after the ford passed the traps first. Just what I was told.
 
You know something is up when king of dyno BS is crying foul.

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Nothing like picking up 700hp between dynos....LOL
 
Joesixpack said:
Altitude does make a difference in a max effort no boost limitation situation. Turbos that are boost limited via a waste gate will show little to no power loss as the turbo just works harder to maintain the same manifold pressure. Until the point it can't work hard enough.

The dyno correction math was based on NA and not turbocharged engines however, its way to favorable to a turbocharged engine for the altitude difference.

Now correcting while spraying nitrous.....*bdh*
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Bingo! Not sure why most folks don't get this..
 
IdahoRob said:
The NHRDA race director told me after the event that pass wasn't accurate. He said nothing added up and the mph light hung after the ford passed the traps first. Just what I was told.
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I didn't know that. It does make sense though compared to what he was running the rest of the day and compared to the ET.
 
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