Bike Feels Diff. at High Altitude - Honda Motorcycles - FireBlades.org
Honda FireBlade Discussion of the Honda CBR 900RR, Honda CBR 929RR, Honda CBR 954RR, and Honda CBR 1000RR Motorcycles.

User Tag List

Reply
 
LinkBack Thread Tools
post #1 of 31 Old 08-16-2008, 2:28 AM Thread Starter
 
Join Date: 04-15-2008
Location: Northern Colorado
Age: 35
Posts: 393
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 12
 
Bike Feels Diff. at High Altitude

Hey Guys. I just moved to Fort Collins, Colorado about 5400 ft up, from New York basically at sea level. I've only been on my 954 for about 5 minutes, but I definitly noticed a difference in power. Is this normal? Also, they only sell 91 octane up here and I had a little 93 octane left from the last fill up in NY before I trailored it out here. Please let me know if you guys know of any complications with this. I didnt think it would mess with the bike considering it is fuel injected. Any help is appreciated. THANKS!!
partyhardryan16 is offline  
Sponsored Links
Advertisement
 
post #2 of 31 Old 08-16-2008, 4:54 AM
 
Join Date: 09-07-2007
Location: A Canadian now back in Canada.
Age: 67
Posts: 1,787
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Reputation Power: 26
                 
Re: Bike Feels Diff. at High Altitude

Yeah, lower power at elevation is normal. You will lilkely find the gas mileage improves, too.

I'm not going to touch the octane issue (except to say tht if it was me I wouldn't worry about it).
ghbzorro is offline  
post #3 of 31 Old 08-16-2008, 5:42 AM
 
Join Date: 06-06-2007
Location: coal point australia
Age: 49
Posts: 420
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 15
     
Send a message via MSN to sb1000rr
Re: Bike Feels Diff. at High Altitude

yeah no power at altitude is normal, no need to mess with it....
sb1000rr is offline  
Sponsored Links
Advertisement
 
post #4 of 31 Old 08-16-2008, 6:16 AM
 
Join Date: 07-08-2007
Location: Washington
Posts: 228
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 13
 
Re: Bike Feels Diff. at High Altitude

With mine the power loss is huge. I go from sea level to around 6000 ft. Every step of the way is noticeable above 2000 ft; but especially above 4000 ft.
BALDGONZO is offline  
post #5 of 31 Old 08-16-2008, 6:45 AM
DUX
 
DUX's Avatar
 
Join Date: 07-07-2004
Location: DE, USA
Age: 48
Posts: 2,041
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 21
       
Re: Bike Feels Diff. at High Altitude

I just read an article about a Range-Rover test high into the mountains on their new turbo diesel.

Different engine and much higher elevation, but if I remember correctly the guide told the reporter to expect to lose about 3% of the power for every 1000ft climbed.



DUX is offline  
post #6 of 31 Old 08-16-2008, 7:10 AM
Global Moderator
 
bladeracer's Avatar
 
Join Date: 11-14-2003
Location: Perth, WestOz
Age: 53
Posts: 32,034
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Reputation Power: 229
                     
Re: Bike Feels Diff. at High Altitude

You have less engine compression.
Your compression is a _ratio_ of the ambient pressure.
I don't recall the figures but at 5400ft ambient is probably down around 11.5psi compared to 14.5psi at sea level.
A 12:1 engine simply multiplies the ambient pressure so 12x14.5 is a lot higher pressure than 12x11.5.

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
bladeracer is offline  
post #7 of 31 Old 08-16-2008, 8:10 AM
 
Join Date: 08-10-2008
Location: Qaanaaq, Greenland
Age: 50
Posts: 222
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 12
 
Re: Bike Feels Diff. at High Altitude

to put it bluntly ... higher altitude = less oxygen = less power.
red08 is offline  
post #8 of 31 Old 08-16-2008, 8:26 AM
Global Moderator
 
bladeracer's Avatar
 
Join Date: 11-14-2003
Location: Perth, WestOz
Age: 53
Posts: 32,034
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Reputation Power: 229
                     
Re: Bike Feels Diff. at High Altitude

This is true in as much as if you have only 80% of the air density/pressure then you also have 80% less O2 content in the combustion mix.
Even re-jetting for this though you're still going to have less compression.
I assume you can run significantly higher compression ratios at higher altitudes without detonation to bring the compression back up equivalent to sea level - 15:1 at 5000ft would bring you back to the 12:1 ratio. I've never lived anywhere where's there's mountains so can anybody confirm this?

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
bladeracer is offline  
post #9 of 31 Old 08-16-2008, 8:34 AM
 
Join Date: 08-10-2008
Location: Qaanaaq, Greenland
Age: 50
Posts: 222
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 12
 
Re: Bike Feels Diff. at High Altitude

Quote:
Originally Posted by bladeracer View Post
This is true in as much as if you have only 80% of the air density/pressure then you also have 80% less O2 content in the combustion mix.
Even re-jetting for this though you're still going to have less compression.
I assume you can run significantly higher compression ratios at higher altitudes without detonation to bring the compression back up equivalent to sea level - 15:1 at 5000ft would bring you back to the 12:1 ratio. I've never lived anywhere where's there's mountains so can anybody confirm this?
I am no engineer but isn't it the oxygen that supports combustion and not the pressure? So theoretically if you had sea level pressure with the same low oxygen level of high altitude wouldn't you still have a decrease in power?
red08 is offline  
post #10 of 31 Old 08-16-2008, 8:41 AM
Global Moderator
 
bladeracer's Avatar
 
Join Date: 11-14-2003
Location: Perth, WestOz
Age: 53
Posts: 32,034
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Reputation Power: 229
                     
Re: Bike Feels Diff. at High Altitude

Of course.
The pressure merely determines the amount of power produced from the charge in the combustion chamber.

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
bladeracer is offline  
post #11 of 31 Old 08-16-2008, 9:50 AM
 
Join Date: 07-20-2008
Location: Clio, Michigan
Age: 40
Posts: 271
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 12
 
Re: Bike Feels Diff. at High Altitude

Their gas should be oxygenated to compinsate for the higher altitude. Your gas mileage should improve also. My truck got 60-70 miles more out of a tank of gas in Arizona then here in Michigan.
08silvercbr is offline  
post #12 of 31 Old 08-16-2008, 12:35 PM
 
Join Date: 04-29-2008
Location: Nashville, TN
Posts: 24
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 0
   
Re: Bike Feels Diff. at High Altitude

Quote:
Originally Posted by partyhardryan16 View Post
Hey Guys. I just moved to Fort Collins, Colorado about 5400 ft up, from New York basically at sea level...I definitly noticed a difference in power. Is this normal? Also, they only sell 91 octane up here...
It's completely expected a normally aspirated engine will produce less hp at higher altitude.

The general rule of thumb is you lose 1% hp for ever 333 ft altitude gain. You also lose 1% hp for each 11F temperature increase, and lose more from humidity increase.

To pick a worst-case example, the hp difference between a low humidity 50F day in New York City vs a 90F humid day in Ft. Collins could be:

3.6% hp loss from increased temperature
3% hp loss from increased humidity
16.2% hp loss from higher altitude
================
22.8% total hp loss

IOW a bike producing 150 rear wheel hp on a cold, dry day at sea-level would only produce 115.8 hp on a hot, humid day at high altitude.

The effect is called "density altitude". There is little you can do to regain the lost hp except for forced induction.

Rejetting a carb will only minimize the loss to the above amount. It will not regain sea-level power or even approach that.

Most fuel injected engines have a barometric pressure sensor and will automatically reduce injected fuel to match the diminished oxygen level at high altitudes. Increasing engine compression ratio won't significantly help.

The engine must run at a certain air/fuel ratio to produce best power. There is simply less oxygen at higher altitudes, so the fuel must be reduced to maintain the same a/f ratio. Without this change the engine runs overly rich, and the loss is even greater.

Even with fueling changes, less fuel is burned per unit time, which means less power produced.
joema is offline  
post #13 of 31 Old 08-16-2008, 12:42 PM
Global Moderator
 
bladeracer's Avatar
 
Join Date: 11-14-2003
Location: Perth, WestOz
Age: 53
Posts: 32,034
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Reputation Power: 229
                     
Re: Bike Feels Diff. at High Altitude

Quote:
Originally Posted by joema View Post
Increasing engine compression ratio won't significantly help.
Why not?
Two otherwise identical engines running the same perfect air/fuel ratio but one with 12:1 and the other with 9:1 compression ratios then the higher ratio engine will produce more power from the same air/fuel mix.

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
bladeracer is offline  
post #14 of 31 Old 08-16-2008, 2:07 PM
 
Join Date: 04-29-2008
Location: Nashville, TN
Posts: 24
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 0
   
Re: Bike Feels Diff. at High Altitude

Quote:
Originally Posted by bladeracer View Post
Why not?
Two otherwise identical engines running the same perfect air/fuel ratio but one with 12:1 and the other with 9:1 compression ratios then the higher ratio engine will produce more power from the same air/fuel mix.
The poster was asking what practical changes he could make to mitigate his 954's hp loss at high altitude. The simple answer is increasing his bike's compression ratio is not a practical solution for the magnitude of power loss he's experiencing.

There is a relationship between thermodynamic efficiency and compression ratio, such that a 1-point increase will produce an approximate 1% increase in thermodynamic efficiency: 7.2 What is the effect of Compression ratio?

However: his 954 is already running 11.5:1 compression ratio. You theoretically might increase this by 1 point to about 12.5:1 (the new CBR1000RR runs 12.3:1). It would require new engine components, and wouldn't be practical for him, but it theoretically could be done.

That increase might buy him 1-2% more hp. But (as shown above) he's probably down 20% in hp vs sea level. A 2% increase isn't nearly enough.

Also higher compression ratios also require higher octane fuel, which the poster already said was a problem. Hs new location has *lower* octane fuel.

So in addition to the cost of major internal engine mods, he couldn't run pump gas anymore.

If practicality, cost and engineering were no obstacles, there are various internal engine mods that could increase hp: increased displacement, higher compression ratio, different valve timing, increase redline, etc.

But none of those are addressing the core problem: reduced oxygen per unit volume at altitude. Rather they increase hp at both sea level and altitude.

The only long-term solution (on that bike) is forced induction. Nitrous injection might be a short-term solution.
joema is offline  
post #15 of 31 Old 08-16-2008, 2:59 PM
 
Join Date: 07-08-2007
Location: Washington
Posts: 228
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Reputation Power: 13
 
Re: Bike Feels Diff. at High Altitude

bladeracer I agree with you most the time, but this time your explanation isn't quite right.

red08 was blunt and correct.

joema is spot on and should given extra kudos for taking the time and sharing his knowledge with all of us. Thanks joema!
BALDGONZO is offline  
Reply

  Lower Navigation
Go Back   Honda Motorcycles - FireBlades.org > Honda Motorcycle Models > Honda FireBlade

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Honda Motorcycles - FireBlades.org forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
A valid e-mail address is REQUIRED. You will not have access to any site features until you activate your account using the activation e-mail that is sent to this address.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Feels like rev limiter at 9k on 06' cbr1000rr classic079 Honda FireBlade 14 12-31-2014 2:20 PM
900RR - back to high altitude, lost so much power danny_isr Honda FireBlade 9 07-05-2007 2:17 AM
Map Q's 07 w/ akrapovic high altitude Crdhelipad Introductions 1 04-02-2007 4:24 PM
Bike Idling high at stops...why?? gabester76 Honda FireBlade 6 12-04-2005 10:20 PM
Back on the bike - feels good! Bacchus Off-Topic 16 02-27-2005 7:38 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome