supra5677
Pro
Posts: 1279
|
posted June 19, 2007 06:40 AM
To Doug Meyer RE: Cycle World Article
Title :Need For Speed
The Latest Spin on Kawasaki's ZX-12
CW 11/00
Here's part of the article that I found interesting and a some questions I have:
...They were even so kind as to pre-run our bike at an airport in Maxton, North Carolina, using the East Coast Timing Association for verification of speeds. What'd it do for them? Stock best was 192.3 mph, and with the exhaust system 199.1 was recorded. Following that test, the bike was "sealed," crated and shipped to us.
We first ran the bike all stock on our dyno, at which point it produced 161.6 horsepower, 4.9 bhp more than our original test bike, a gain easily attributable to optimized cam timing. With Muzzys exhaust system, output rose to 168.9. Our top speed test site is considerably higher than where Muzzy tested , SOME 2200 FEET CLOSER TO OUTER SPACE THAN MAXTON'S 256 FEET ABOVE SEA LEVEL.
So what's an absolutely optimizwed ZX-12R with an aftermarket pipe do on our high-desert test ground? With an approximately 10-mph tail wind, the pictured motorcycle pased the gun at a remarkable 197.3 mph, then immediately hit the rev limiter. Averaged with an against the wind best of 183.5, you get 190.4, 3.4 mph more than our original stock testbike.
Question 1: How much horsepower do you lose in percentage with altitude?
Question 2: Why is the article inferring that the cam timing was changed?
Question 3: Why was a radar gun used instead of electronic timing?
Question 4: Why only 7.3 RWHP gain with the Muzzy Exhaust?
supra
   
|
dougmeyer
Needs a job
moderated
Posts: 2713
|
posted June 22, 2007 01:07 PM
 Edited By: dougmeyer on 22 Jun 2007 14:07
Sorry, Supra, I missed this.
1. HP loss with altitude is not linear and depends on pressure altitude (baro), temp, and relative humidity.
pressure altitude change is (cumulatively)approximately 2.5% for the first 1000'
6.5% at 2000'
10% at 3000'
14% at 4000'
17.5% at 5000'
These percentages are based on std. temp at each altitude above SL and take into account the normal temperature lapse rate. (Called the Adiabatic Lapse Rate which is 3.5deg.F per 1000')
A + or-15 deg (F) change in air temp equals a 1000 ft change in equivalent altitude. (if you are at Sea Level at 59deg and raise the temp to 74F, it's the same as going up 1000 feet.)
The range in relative humidity between desert dry and saturated (rain) can cause about a 2-3 % hp loss.
All these factors are what a "Correction Factor" on the dyno corrects for.
As an aside, I don't know the conditions CW tested under, but it was 90+F and godawful humid at Maxton. You do the math.
2. The article is insinuating, you are inferring. You are inferring that the cam timing was changed. It was not and had the magazine opened up the sealed engine as they were invited to, they would have seen that. It was checked, however, to make sure it was at stock specs. All three bikes were spot on.
3.Don't know, except that the magazines all use radar. I'd say this is because probably because it takes time, location, effort, and manpower to set up clocks. Clocks take a long time to set up, aim and calibrate. They don't spend a lot of time doing top speed runs.
The magazines all use the same stretches of (public) desert roads around the Mojave desert for their top speed testing (or at least did then). You ride out there, somebody follows in a van with the radar gun and probably cameras and you blast past the editor standing on the shoulder until everybody is satisfied or worried, or scared to death.
4. I don't know. But there is plenty of data, anecdotal and empirical to suggest that this is not the norm.
Doug
|
|
|
|
|
HOME
NEW TOPIC