DYNO question

[Pappy]

after last nights dyno pulls, one product we tested was showing a 10 mph increase on top end. i didnt have time to ask then, but ill ask now.


how does a product (not gearing or tires) show a top speed increase without changing the gearing?

[kazpr]

I dont know but what all did you dyno? Come up with some new ideas for the R? Please do tell :)

[MY450R]

maybe some kind of cdi box or something
yeah what were you dyno ing

[Taco]

Originally posted by Pappy
after last nights dyno pulls, one product we tested was showing a 10 mph increase on top end. i didnt have time to ask then, but ill ask now.


how does a product (not gearing or tires) show a top speed increase without changing the gearing? Only other way to get a speed increase is to be able to get more RPM outta the motor.

[LS@GtThunder]

How?? By raising the RPM - My guess is you tested a Vortex CDI.

[lukester720]

Originally posted by LS@GtThunder
How?? By raising the RPM - My guess is you tested a Vortex CDI.

Thats what I was thinking.

[Pappy]

Originally posted by LS@GtThunder
How?? By raising the RPM - My guess is you tested a Vortex CDI.

thats correct, however i always thought that top speed was controlled ultimatley by gearing?

[quadrcr161]

Originally posted by Pappy
thats correct, however i always thought that top speed was controlled ultimatley by gearing?

from what i understand its a collection of HP, gears and RPM.

but once you open the door and raise the hp, and the the rpm, top speed will raise. i have it in my head but i can explaine it like i want. :)

[Southtown00]

It is all gearing. When you raise the RPMs though you are maximizing how fast your wheels spin though. No matter what gear ratio you have, 11,500rpm will have a higher speed than 8000rpm. Think about it, when your in the same gear, do you go faster at 4000rpm or when you are closer to the rev limiter? Also, the dyno will show more top speed than real life because there is no wind resistance, but not 10 mph worth.

[lukester720]

Mabey Gabe will bust out the ole' gearing calculator and give us the rundown. The main question I have is did it seem to add any power at all Pappy? I have the cdi but I don't have a dyno:(

[86atc250r]

Ultimately gearing and RPM both play very significant roles in top speed MPH (which is why you go faster at 7000 RPM in 5th gear than you do when idling in 5th gear).

If the engine was able to pull top gear past the old revlimit (with the new CDI), then top speed will be increased.

If you know the sprocket and actual tire size, you can use a gearing calculator to figure out just how much difference raising RPM makes in the equasion.

http://home.earthlink.net/~gellett/trx450r.htm

[joe1l]

1000 more RPM in 5th gear would give you close to 10 more mph. This is why the YFZ's are geared so small but still maintain a high top speed, due to that 11,500 Rev limit.

Its just a simple math equation:)

[red2004 TRX450R]

Originally posted by Pappy
thats correct, however i always thought that top speed was controlled ultimatley by gearing?

Pappy are u kidding!!!
I hope you are
I allways take your advice !!!

:eek2: :huh

[Pappy]

no i am still correct....if a 38 hp engine with stock gearing will run a top speed of 78 mph, a 55 hp engine will run the same top speed but it will get to the top speed faster

[Pappy]

Originally posted by red2004 TRX450R

I allways take your advice !!!

:eek2: :huh

advice is what it is.....thats why i dont make bold statements but merely advice or suggestions.because i will be the first to say i learn new stuff everyday:D

[86atc250r]

Not if the 55hp engine can pull the machine to a higher RPM without running out of power to overcome rolling and wind resistance.

But yes, in theory horsepower does not matter -- only RPM and final gearing..

In reality though, HP (or really, torque) is just what drives the RPM to pull the gear.

[Pappy]

Originally posted by 86atc250r
Not if the 55hp engine can pull the machine to a higher RPM without running out of power to overcome rolling and wind resistance.

But yes, in theory horsepower does not matter -- only RPM and final gearing..

In reality though, HP (or really, torque) is just what drives the RPM to pull the gear.

exactly, as long as the test paramaters are the same my thinking is correct.


i geuss my main question has been answered, i just didnt take the effects of the increased rpm into account for there being a higher top speed.

[lukester720]

Did the CDI show any type of power gain over stock? Did you dyno the different settings? I have the CDI but no place close to go dyno it.:confused:

[Pappy]

the only number i paid attention to was peak HP. and i only watched it for a few runs. it didnt make any more power per say but offers other advantages as described above.

i didnt want to know too much info so i could be unbiased in my opinion of the product when i read the final review.

i will say that the man running the dyno has been impressed by the machines he has tested with the ignition so i reckon that says something.

[86atc250r]

The dyno also won't show part throttle response differences

This became very clear when doing comparisons with the FCR vs the stock carb.

No HP difference & no difference in timed drags, but when ridden, there is a world of difference in the way the quad responds to throttle input.

[Pappy]

after seeing some numbers and the stock numbers i am reconsidering what i do to my engine. for me the money outlaid may not justify the increase in power ( i know numbers dont always tell the story)


the way i figure it all ill be doing is paying for my quad to kill me faster:devil:

[lukester720]

Originally posted by 86atc250r
The dyno also won't show part throttle response differences

This became very clear when doing comparisons with the FCR vs the stock carb.

No HP difference & no difference in timed drags, but when ridden, there is a world of difference in the way the quad responds to throttle input.

I agree, I just didn't know if he had before and after sheets or something.

[Pappy]

when the review comes out it will have before and after numbers.



i just re-read what i posted and man...i sound old:( i never thought id think more power wouldnt be a good thing

[lukester720]

You will be putting the review on this forum I take it?

[Pappy]

im not certain, i am not doing the review thats why i didnt want to comment on hard numbers.

[86atc250r]

Just remember that the dyno doesn't tell the whole tale unless you are just looking at pure straight line acceleration.

If you just looked at the dyno the FCR would look like a worthless mod -- however, after you've ridden a 450R with an FCR you'll know that you're not seeing the whole picture.

Another consideration is with an ignition - the most valuable property is that it raises the revlimit. Even though with most engines, power is falling off near the limit, there is still plenty of useable power up there for real riding situations.

If you build an awesome engine, you'll be hating the limiter.

[lukester720]

Is GTThunder doing it? AAhhh, anyways keep us posted on where to find the review.

[Pappy]

well, thats my dilema.

i have a chance to have a damn fine engine built with all the goodies, including the ignition and the 41fcr.

im just not sure if i personally need much more power then i could gain by a complete rebuild versus a cam and the other mods listed above.

[86atc250r]

Depends on what you're looking to do with the engine.

Personally for woods racing, I'd leave the stock carb in place and run a 500cc kit & a hotcams 2 or HRC. Nice smooth, easy to ride power across the board.. Relatively inexpensive and reliable.

For dunes, tt, or maybe even MX, I'd get wilder and use the FCR, and do a number of other things -- wilder cam than the HRC, higher compression, etc.

[Karizz]

Originally posted by Pappy
no i am still correct....if a 38 hp engine with stock gearing will run a top speed of 78 mph, a 55 hp engine will run the same top speed but it will get to the top speed faster

Oh...that explains alot to me now..when I was in Baja CA last January with my brand new stock 450r I was running flat out wide open on a 40 mile long dried up lake bed and a stock 400ex was running same speed as me...I was like wtf...I thought I had the fastest quad...lol......elementary my dear Watson,elementary!..lol