First Dyno Pull

[gofast68]

I've had my '94 for a little over a year now and have taken it to a local Dyno to check the AFR. I didn't want them tuning the bike or monkeying with anything, so I had 3 pulls to see how close I got the jetting. The bike runs okay since I don't have much to compare it to except for this site. What has made me really curious as to my jetting is my MPH at the local track. I live in Salt Lake City, so I'm in the nose bleed seats. I cannot get the bike to really pull on the top end as I would have expected the famed Vmax would. The most MPH I can get is 109. I've got a few passes posted up in the quarter mile thread from last year. It really hasn't changed much this year except I can launch it harder.

The first pull is a WOT pull. The Second is a 50% throttle pull and the third is a 25% pull. Overall, I think the jetting is pretty close. Could probably be tuned up just a bit to smooth things out, but not too bad for my first CV carb attempt. I've been completely through the carbs and cleaned all the gunk out. They were virgin before me. The bike was kept in excellent shape by the previous owner.

Here's my settings:
Main Jet - 147.5
Pilot Fuel Jet - 37.5 (stock)
Pilot Air Jet 1 - 90 (stock)
Pilot Air Jet 2 - 160 (stock)
Dynojet Stage 1 Needle - Clip 2
Stock Slide Springs

Stock airbox with K&N. The Y has been removed, but I still have it.

Muffler has had a 1 inch hole cut out of the baffle. Essentially, a hole saw was put down the exhaust hole and a 1" hole cut. I can see the header through the muffler. I can imagine it was only done to improve the sound. The rest of the exhaust is stock.

I have converted to the coil on plug setup as I had a coil go bad and didn't want to spend all the money for the same crap. Aside from that, the bike is 100% stock and just barely bumped over 14000 miles.

I am the second owner of the bike and with some of the above mods, I have had to deal with what was presented to me.

The day the dyno pulls were made, it was 93 degrees. I have been unable to get the humidity or DA numbers, but am working on it. The graph shows that the pull was corrected, but I don't know by what factor. My physical elevation where this was taken is about 4400 ft.

With all that said, it appears to me that the top end is not there, also proven by my lackluster MPH in the quarter. The bike doesn't miss, doesn't cough, idles smooth, runs smooth and for all intents and purposes, has no problems. With looking at everyone else's "stock" dyno pulls, mine is behind by 10-15 horses on the top end. The torque doesn't look too bad, but there's no Vmax horsepower.

WTF? Any thoughts and/or idea's? I've wondered about weak valve springs maybe or the diaphragms not opening all the way on the top end? I'm grasping at straws because the bike really doesn't seem to have an obvious problem.

 

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http://www.vmaxforum.net/showthread.php?t=3411&page=8&highlight=muscle

Check out this thread. The last page has VmaxinID's dyno results. He is also up in the clouds (altitude). He got 107HP if I remember right. And he has hmf pipes and a jet kit. Altitude kills HP.

This is the only thing I know of to compare your pull to. But, looking at the two, I'd say your right in line.:confused2:

 

[gamorg02]

i'd like to know what the scale is on the a/f. you have that WOT dip in the midrange that seems to plague every vmax!

i actually assume the bottom of the graph on the Y scale is 10. i would say maybe try leaning your needle as lean as it can go and u still have no change in driveability?

 

[gofast68]

i'd like to know what the scale is on the a/f. you have that WOT dip in the midrange that seems to plague every vmax!

i actually assume the bottom of the graph on the Y scale is 10. i would say maybe try leaning your needle as lean as it can go and u still have no change in driveability?

Yeah, I obviously can't take a picture. The red dotted line is 13 and the line above is 14, the line below is 12.

The dip appears to be the vboost coming on. I have seen the same thing where they go pig rich before. I don't know what would be the best steps for cleaning the vboost transition up.

 

[sidwin]

I lived in SLC and it does kill HP but if you look at his dyno sheet it has SAE correction for altitude. if his corrected hp is only 91 i bet his uncorrected is a good bit less. You should ask for your data file and then download winprep and see all the changes.

 

[naughtyG]

The first thing I would do is put the Y back on the airbox and take it for a run to see how it goes.

Next I would double check the Vboost is working properly:
- do you hear it cycle when you turn the bike on?
- have you adjusted your Vboost cable recently, to make sure the butterfly valves open fully?
- with the bike warmed up and on its center stand, blip the throttle to get the motor past 6k rpm while watching the Vboost valve. Does it open fully? It should start moving at 5850 rpm and be fully open by 7000.

 

[dannymax]

The first thing I would do is put the Y back on the airbox and take it for a run to see how it goes.

Next I would double check the Vboost is working properly:
- do you hear it cycle when you turn the bike on?
- have you adjusted your Vboost cable recently, to make sure the butterfly valves open fully?
- with the bike warmed up and on its center stand, blip the throttle to get the motor past 6k rpm while watching the Vboost valve. Does it open fully? It should start moving at 5850 rpm and be fully open by 7000.

+1 My first thought too! unk:

 

[tfisher65]

The first thing I would do is put the Y back on the airbox and take it for a run to see how it goes.

+1 and get rid of the "Dynojet Stage 1 Needles" and go back to stock.

 

[gamorg02]

+1 and get rid of the "Dynojet Stage 1 Needles" and go back to stock.

think so? i'm wondering if u can go leaner on the s1 needles than stocks.

 

[tfisher65]

I believe the S1 needles have a smaller/faster taper which would make it richer through the power curve. Am I right guys?

 

[gamorg02]

I believe the S1 needles have a smaller/faster taper which would make it richer through the power curve. Am I right guys?

tough to tell from the pic and i don't feel like digging thru my needles again but u could def be right, however it also looks like on its leanest setting (if thickness is equal all the way down) they can be leaner than stock.