View Full Version : Altitude vs Hp

10-19-2007, 07:39 PM
I received my sxv550 22 September 2007 after a 2year wait.
STD Exhaust, Derestricted & remapped by dealer.

DynoJet figures:
Mileage= +- 1000Km (+-625miles)
Pwr = 60.1RwHp
Trq = 47.8Nm
Fulng= slightly rich right at the bottom
lean for the rest of rpm range
Alti = 1600m above sae level

Seen figures of 70RwHp is this altitude.
What % effect should altitude have on these machines approx.

Now at +- 1000miles and not a single problem or complaint YET:worship:
Goes like a Bastard. Starts within 2 goes hot or cold. Idles well. No funny noises other than loose chain "sorted" :cheers:

Fantastic forum Thanx
paul xtn

Lunatik Inc.
10-19-2007, 08:34 PM
Try this out.


This calculates you at 10hp down. Right at 60hp

10-19-2007, 10:32 PM
Im sure ill be corrected if wrong but :

ONLY carb'd bikes would lose HP at altitude not injected bikes

PS, De-restrict, Power commander with custom tune 66.7 hp.

10-20-2007, 01:33 AM
60hp is about normal for a 550.

First thing to remember is that we do not have true FI, what we have is what Bosch was using in the 70`s, and GM was using on their trucks in the early 90`s, a throttle body that shot gas into an intake manifold, same thing here, it`s just like a carb but without an accelerater pump or diaphrams with a control box that monitors fuel input at different throttle settings and RPM`s, with no air control.

True FI has air and fuel control, with injector nozzels shooting gas directely into the head, no manifolds or runners like first generation FI, in the early day`s you could get a carb set-up to out perform first generation FI.

The Power Commander, is like having a fist full of jets, and you can really fine tune the Aprilias FI with it, with little hassel, but it`s unfortunate there is little we can do on the fly.

Last week i was at Big Pine Ca. rode from 4200-10,000ft, and a major difference in power, in this situation i would have prefered to have a carb, because i could have made the adjustments needed, but i still had a blast.:cigar:

10-20-2007, 01:34 AM
Im sure ill be corrected if wrong but :

ONLY carb'd bikes would lose HP at altitude not injected bikes

PS, De-restrict, Power commander with custom tune 66.7 hp.

Go to Bonneville Salt Flats (4K+ ft) for example and see how any EFI bike or car will have less power than at sea level. All bikes (and engines) of all types, lose power the higher you go, there's simply less oxygen available, so less fuel is required for the proper fuel/air ratio , which also means less power.

True fully sensored EFI systems (not the Aprilia) simply adjust fuel/air ratio automatically where carbed engines have to mess with jets for that. EFI engines seem to have more power at varying altitudes because they keep their fuel/air ratio optimal, whereas an improperly jetted carbed engine can run weaker (too rich or too lean).

Turbos, blowers, racing (highly oxygenated) fuel and nitrous are ways to get more oxygen into the engine to compensate. :burnout:

My .02 after having been at Bonneville Salt Flats speed trials this year and talking to the fanatical folks there. :cheers:

Lunatik Inc.
10-20-2007, 08:02 AM
good post.

10-20-2007, 11:11 PM
Lack of O'2 of course will rob power but on a carb'd bike it would be tremendous...

I have zero clue on this or that altitude , but I have road at extreme elevation before on both, and on a carb'd vehicle they almost quit running it is that dramatic...

75-80 percent loss at heights such as pikes peak..

But Ihave zero clue the actual losses

10-20-2007, 11:35 PM
..one thing we must remember is that regardless of how the fuel gets in the engine, an engine can only produce power based on the oxygen/fuel available. the advantage to a true efi system is that it constantly adjusts the fuel/air ratio for climate(density) temperature(density) and elevation(density again). In a carburated engine this would have to be done manually..hence SONNY'S expeiance of a lack of power( less air @ higher elevation=running richer=loss of power). its best if we think of the RS/SXV'S system as super trick carbs. they still have to be adjusted for elevation. its not dramatic but is necessary to extract the most performance.
Our elevation is 7500 ft here and I am still trying to establish good baseline numbers here. I hope as APRILIA establishes this line, they see fit to upgrade this system in the near future...just my .02 worth....CW

10-21-2007, 01:29 AM
That`s why i think that the PowerCommander, is a good tool for the RXV.:cigar: