Bikemans stag 2 tune for turbos

[Fack]

Rotax’s words specific to that engine.

Power loss relative changes in elevation aren’t fixed across different engines, and on a system that’s compounded by a turbo, it gets even more complicated than a linear percentage loss.

Case in point - does a 5hp engine stop making power past 1k feet elevation?

The question was asked and Skank posted his results. The guy does a lot of testing and has real world experience with these tunes at that elevation.

Fack

A chart in a Rotax Aircraft Engine Shop manual says 5hp loss for every 1000ft elevation increase. [Lazair Aircraft w/503 fan manual]

Ok then, according to BRP values, then...
@ sea level, 165hp
@ 8000 ft, 165hp
@ 9000 ft, 160hp
@ 10000 ft, 155hp
@ 11000 ft, 150hp
@ 12000 ft, 145hp

Since its a constant, then...
Stage 3, 95 octane is 30+hp
@ sea level, 195hp
@ 8000 ft, 195hp
@ 9000 ft, 190hp
@ 10000 ft, 185hp
@ 11000 ft, 180hp
@ 12000 ft, 175hp

...so what if it lost power? I'd still be happy with that at 12k feet.

 

[Dynamo^Joe]

The book actually says "percentage" loss of power.
I put 5hp because of the snowmobile engines we're mostly talking about 800~850 cc and percentage of snowmobiles that ride over 12000 feet is small compared from sea level to 12000 feet.

I talk with "rule of thumb", meaning; a broadly accurate guide or principle, based on experience or practice rather than theory
which I can prove it's fairly accurate by with a common sized snowmobile engine having a gram amount adjusted for every 1000 feet, AND Brp specs also prove this in their elevation spec sheets, gram amounts and clicker position / elevation range of 2000 ft.

This is cut and paste out of the 503 rotax manual
100% @ 0000' elevation
89% @ 3280' elevation
78% @ 6560' elevation
60% @ 9850' elevation
56% @ 13120' elevation
53% @ 16400' elevation

If an example summit engine had 150 hp at
then...
100% @ 0000' elevation [150hp]
89% @ 3280' elevation [134hp]
78% @ 6560' elevation [117hp]
60% @ 9850' elevation [90hp]
56% @ 13120' elevation [84hp]
53% @ 16400' elevation [80hp]

can calculate an 850T and an 850N/A engine power by those percentages and break them down into 1000 ft increments.

I do no testing, none. I sit behind a laptop, watching sleddin vidyas, w/a notepad and a pencil parakeeting other peoples information in between reaching in my LinQ carrypack, eating chicken wings, slurping a Busch beer and "hope" my tuning "theories" work.

Joey

 

[1709]

The book actually says "percentage" loss of power.
I put 5hp because of the snowmobile engines we're mostly talking about 800~850 cc and percentage of snowmobiles that ride over 12000 feet is small compared from sea level to 12000 feet.

I talk with "rule of thumb", meaning; a broadly accurate guide or principle, based on experience or practice rather than theory
which I can prove it's fairly accurate by with a common sized snowmobile engine having a gram amount adjusted for every 1000 feet, AND Brp specs also prove this in their elevation spec sheets, gram amounts and clicker position / elevation range of 2000 ft.

This is cut and paste out of the 503 rotax manual
100% @ 0000' elevation
89% @ 3280' elevation
78% @ 6560' elevation
60% @ 9850' elevation
56% @ 13120' elevation
53% @ 16400' elevation

If an example summit engine had 150 hp at
then...
100% @ 0000' elevation [150hp]
89% @ 3280' elevation [134hp]
78% @ 6560' elevation [117hp]
60% @ 9850' elevation [90hp]
56% @ 13120' elevation [84hp]
53% @ 16400' elevation [80hp]

can calculate an 850T and an 850N/A engine power by those percentages and break them down into 1000 ft increments.

I do no testing, none. I sit behind a laptop, watching sleddin vidyas, w/a notepad and a pencil parakeeting other peoples information in between reaching in my LinQ carrypack, eating chicken wings, slurping a Busch beer and "hope" my tuning "theories" work.

Joey

Joey, have you done any testing on chicken wings? need to know who makes the best?
Lol.

 

[Fack]

Your numbers make sense for a naturally aspirated engine but the doo turbo is running out of breathe at 8k feet. So, close the waste gate as tight as you want - there’s nothing left to give above that elevation.

Which is exactly why you’re not going to add much weight above those elevations. The power you are seeing is the backside of a downhill slide. You can add boost at lower elevations where the density is greater but you’ll feel THAT power start to decrease sooner than doos advertised 8k feet, because the turbo is falling off. The turbo is only capable of so much and you can’t simply move the curve up to match what the stock numbers have done.

So let’s say that turbo is capable of 165 horsepower at 8,000 feet..... well... it’s probably going to stay close to 165 horsepower at 8,000 feet.

Which supports Skank’s findings.

There’s probably some gains to be realized by tuning but the turbo is the limiting factor as the air gets thin.

Something about chicken wings??

Fack

The book actually says "percentage" loss of power.
I put 5hp because of the snowmobile engines we're mostly talking about 800~850 cc and percentage of snowmobiles that ride over 12000 feet is small compared from sea level to 12000 feet.

I talk with "rule of thumb", meaning; a broadly accurate guide or principle, based on experience or practice rather than theory
which I can prove it's fairly accurate by with a common sized snowmobile engine having a gram amount adjusted for every 1000 feet, AND Brp specs also prove this in their elevation spec sheets, gram amounts and clicker position / elevation range of 2000 ft.

This is cut and paste out of the 503 rotax manual
100% @ 0000' elevation
89% @ 3280' elevation
78% @ 6560' elevation
60% @ 9850' elevation
56% @ 13120' elevation
53% @ 16400' elevation

If an example summit engine had 150 hp at
then...
100% @ 0000' elevation [150hp]
89% @ 3280' elevation [134hp]
78% @ 6560' elevation [117hp]
60% @ 9850' elevation [90hp]
56% @ 13120' elevation [84hp]
53% @ 16400' elevation [80hp]

can calculate an 850T and an 850N/A engine power by those percentages and break them down into 1000 ft increments.

I do no testing, none. I sit behind a laptop, watching sleddin vidyas, w/a notepad and a pencil parakeeting other peoples information in between reaching in my LinQ carrypack, eating chicken wings, slurping a Busch beer and "hope" my tuning "theories" work.

Joey

 

[1709]

deleted

 

[1709]

A Ski Doo race member runs the race tune it`s 8 to 10 pounds of boost they test and

It was built and tested in togwotee and the RMSHA Circuit. so if they run that kind of boost,
the stage 2 should be no problem.

 

[nytro41]

OK, very interesting, rule of thumb, 5HP = 1 gram of weight, Stage 2 is 20HP = 4 grams.

Depends on clutching company. Some don’t add weight when you add hp ?

 

[1709]

Depends on clutching company. Some don’t add weight when you add hp ?

if you are running the same peak RPMS, and do not add weight when you add Hp, you did not add enough HP to make a difference. now if you ported your engine and raised the peak RPMS then you would not add weight and some times you might have to take some weight off to get to the peak RPMS.

 

[nytro41]

if you are running the same peak RPMS, and do not add weight when you add Hp, you did not add enough HP to make a difference. now if you ported your engine and raised the peak RPMS then you would not add weight and some times you might have to take some weight off to get to the peak RPMS.

Not necessarily true. you add HP you have to add weight if you are using the same Cam Arm. Change the Cam Arm up and you can run a lot less weight while maintain the RPM the motor (in this instance a stock motor stock pipe) is supposed to be running at. Take a look at Ibexx clutching (Ibexx.com) They do it a lot differently.

 

[1709]

This thread is about adding a stage 2 tune and how much pivot weight did he have to add, same cam arm. not about changing to a different cam arm.

 

[Inthe8s]

Well the 984 arms are WAY to light..... I took the 150/350 spring out and put a 90/280 in and weights now weigh about 52grams, and cross bolt total weight is 108g PER ARM.... that's with a 280ish final force.....and yes this is stage 3 and not 2 but you get the picture..... "Pray for SNOW" !!!

 

[Blk88GT]

Race dept has tunes out there. Mentaberry has one of em....

 

[1709]

Well the 984 arms are WAY to light..... I took the 150/350 spring out and put a 90/280 in and weights now weigh about 52grams, and cross bolt total weight is 108g PER ARM.... that's with a 280ish final force.....and yes this is stage 3 and not 2 but you get the picture..... "Pray for SNOW" !!!

Yes but you changed the helix, what is the end degree of that helix? 38? 36? if so, that`s why you can run more weight. and you put in a stiffer secondary spring, both will effect the weight of the cam arms.

 

[nytro41]

This thread is about adding a stage 2 tune and how much pivot weight did he have to add, same cam arm. not about changing to a different cam arm.

For sure. My point was with a stage 3 if you change the cam arm you can run the same weight as the stage 2 and get the same response due to not slinging as much weight. you can achieve that by changing springs or helix as well. but you don't necessarily have to. sorry didnt mean to hijack the thread

 

[sledhead_24_7]

Race dept has tunes out there. Mentaberry has one of em....

 

[1709]

this thread is about the bikeman`s stage 2 tune.

 

[jdrmx]

Ive been following this thread, i just put in Joeys clutch kit, I, along with the op's original question, am interested in more detail regarding the stage 2 tune.


Sent from my iPhone using Tapatalk Pro

 

[1709]

Anyone else running these tunes ?