I've done a couple of dyno runs since fitting the new cams and here are a couple of observations when looking at the results. The result above is better after a little tuning than the woeful first run...
The print out up top was from the last run 3 days ago.
I was just shy of 105hp with the Kent cams and fueling was pretty flat at just over 13 A/F ratio. 155 mains / needle 3rd from top.
With the new cams and 162.5 mains needle 4th from top, A/F was just on 13 until 8000rpm and started to drop to mid 12's by 9000rpm.
The main problem was a huge drop down to mid 10's on my A/F from 4700rpm to 6000rpm and a massive dip in my torque curve.
I actually lost 10NM of torque in this region and lost HP plus I made no extra max HP.
I then attached my own O2 sensor which reads from the headers and not just a sniffer in the tail pipe.
I took my own A/F readings and they where similar just a little richer than the dyno result.(Akra can fitted with good seal)
So with the info I had and reading I could take from my O2 sensor I started tuning once again...
Shifting the needle back to the 3rd from top made a small gains in response and things improved with further advance timing changes in the mid range but still a big hole in the mid range torque curve.
( needle 2nd from top found it hunting for fuel)
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1 thing was apparent though, with the air box I made up fitted, my A/F readings from 7500rpm actually went from 12.5 and steadily climbed to low 13's , the opposite to the dyno results because from 180km onwards there is plenty of air being fed into the box.
I found an extra 2.5Hp on my max reading by changing the muffler from the shorter Akrapovic R6 can to the Megacycle can I had made up which was slightly longer.
But with not a complete seal around the link pipe it gave me a 1.5 points higher A/F reading than at the headers with my own O2 sensor. The dyno O2 sniffer sat pretty close to where the can joins the link pipe so something to be aware of.( A little sealant fixed this problem so the A/F reading on the map above has been corrupted to read leaner by the leaking muffler join.
But I still have a big dip( all be it not quite as bad as the first run -5hp at 5500 and -10 at 6000rpm) in the mid range torque as you can see and A/F on the dyno results but this is why the dyno is just a tool to help tuning and not the be all and end all as my A/F with the O2 sensor on the road is a lot more stable and there is just a slight hesitation if I'm at full throttle by 5,000rpm plus the different top end A/F ratios.
So I suspect this dip in the curve on the dyno is actually from the Accelerator pump and lack of air flow at the dyno room. That's right where your twisting that last 30% of the throttle to WOT.
My next dyno run, I'll dis-connect the Acc pump to see how things go.
I feel I may have to adjust the level of fuel stored in the Acc pump to give me a shorter shot of raw fuel when twisting the throttle.
