Help me read my dyno results

[steves]

Wheeler said it's running pretty good... and the numbers look okay. May have some room in the midjet to make adjustments?

Clicky for big pic.

[Mat0302]

I was told that the torque curve should be as smooth as possible. thats about as much as i know

[md86]

Um , I already TOLD you what I had to say at Wheelers . I thought you said it was "close enough" .
If it were ME though , I woulda asked him what he thought about changing the mains , as it seems a little off up top , which would mean you'd have to play with the needles and pilots too , but still ...... But that IS a pretty smooth curve

[steves]

Um , I already TOLD you what I had to say at Wheelers . I thought you said it was "close enough" .
If it were ME though , I woulda asked him what he thought about changing the mains , as it seems a little off up top , which would mean you'd have to play with the needles and pilots too , but still ...... But that IS a pretty smooth curve

I've got an email in to Dale Walker... I didn't forget what cha said... 8)

[md86]

That's good , because I'm not sure I remember .....

[The CyberPoet]

OK, here goes (Fuel-Air):

Idle should sit around 14.2 - 14.7:1. This will help keep the plugs from fouling while warming up, idling. Your idle fueling is excessively lean, and at 18+ :1 ratio, I'd expect you to have problems starting the bike without choke or throttle input.

The next thing you see on CV carbs is always a drop, with the fuel getting richer. This represents the throttle being opened (mixture richens), the engine builds a bit more vacuum, then finally gets enough vacuum available to raise the slides (the downward trend bounces back upwards between 2-3k on your dyo sheet; on a Kat, I'd expect the downward movement to return to an upward motion by 1800-2500 RPM, depending on which springs are installed).

From here on out, you're trying to hit a target (with a jetkit or aftermarket tuning) of 13:1 - 13.2:1, which is the optimum performance fuel-air ratio for any gasoline based engine (13.2 with perfect "lab" gasoline, 13:1 with most blends including minor ethanol). The fact that yours is showing around a 12:1 ratio much of the time tells me that the mix is way too rich (rich enough to foul plugs and build excess carbon in the cylinders).
Most times, you'll see a small dive or spike somewhere in the 4k-5k range due to the harmonics on the exhaust & EPA fueling test points, then it resumes the general trend of whatever was happening before.

Hope that helps clear it up and makes sense to you. Basically it boils down to:
Idle circuit too lean
Main circuit/slide-response too rich.

Cheers,
=-= The CyberPoet

[steves]

Dale's suggestions...

"Back out the fuel screws to 3 turns and see how it runs, leave the snorkel in for now and remove one shim"

Guess I might be booking some more dyno time....

[Sin]

yeah i agree with cyber thats a nasty fuel curve like he said way lean on start up and part throttle like 1/8 turn then goes off the deep end rich soon as the needle and emulsion tube and float pick up then continues to the main jet drop a clip on the need and maybe even down a jet size on main and either a bigger pilot jet next size up or crank out the mixture scres like dale walker says i just dont think 3 turns or even 4 turns are gonna bring it back from 18to1 to 14.to1 cause it says max18 thats where the scale stops who knows how lean it really is

[steves]

yeah i agree with cyber thats a nasty fuel curve like he said way lean on start up and part throttle

Have to also remember, that since there is no o2 sensor on the collector, that the A/F results aren't accurate at all in the low range....

[Sin]

yeah i agree with cyber thats a nasty fuel curve like he said way lean on start up and part throttle

Have to also remember, that since there is no o2 sensor on the collector, that the A/F results aren't accurate at all in the low range....

what you mean you have the o2 sensor out and just a open hole?????

[steves]

yeah i agree with cyber thats a nasty fuel curve like he said way lean on start up and part throttle

Have to also remember, that since there is no o2 sensor on the collector, that the A/F results aren't accurate at all in the low range....

what you mean you have the o2 sensor out and just a open hole?????

No o2 sensor.... it's a carb'd bike. So the sniffer in the pipe.

[Sin]

then the readings are correct then the sniffer is just a really accurate o2 sensor using a o2 sensor is a ok way to tune it will get you pretty close but the sniffer which is a 4 gas analyzer is the best way

[steves]

then the readings are correct then the sniffer is just a really accurate o2 sensor using a o2 sensor is a ok way to tune it will get you pretty close but the sniffer which is a 4 gas analyzer is the best way

Right... but at low RPM, Wheeler said the sniffer isn't as accurate, which is why there is the big drop off on the A/F readings.

[Sin]

then the readings are correct then the sniffer is just a really accurate o2 sensor using a o2 sensor is a ok way to tune it will get you pretty close but the sniffer which is a 4 gas analyzer is the best way

Right... but at low RPM, Wheeler said the sniffer isn't as accurate, which is why there is the big drop off on the A/F readings.

maybe his isn't all the ones ive used are dead on regardless of rpm and ive probably spent more time with various bikes on the dyno then anyone here i spents 9 days on the dyno with my busa alone that got $$$ build a motor and spend another 1200 bucks on the dyno time to get it fine tuned but it was worth it it screams and gets good milage 42mpg

[The CyberPoet]

I've never seen a sniffer that was more than 1/10th of a point off on fuel-air if the engine was already running when it started logging (since exhaust gases displace the contents of the pipe once the engine is going). Hell, even the Gunson analyzer ($180 or so if you want one at home) is accurate to within a 10th of 1 fuel point.

Cheers,
=-= The CyberPoet