Landracing Forum
Tech Information => Technical Discussion => Topic started by: Vishnuatepork on January 02, 2012, 12:49:32 AM
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The preliminary numbers for my VX800 (Suzuki 800 Vtwin motorcycle) are in at 68 hp and 47 ft# torque. I was wondering if anyone could maybe help explain to me the drop in torque. The base line was 51 or 52 ft# and 57HP (different dyno I know but still a drop in torque was not expected....). My Mechanic did say that it was a very flat torque curve, FWIW.
The jetting had not been touched, it was set up for an SV650 (thats how the carbs come), and the ignition had not been touched. I am hoping that we may be able to eek out 70hp, which would mean nearly a 20% increase over stock, not bad IF it hits that. Any educated guesses as to how many % over stock we get by the ignition module alone?
Cheers
Alan
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Can't make any educated guesses without the rpm numbers for the hp and torque on both tests.
Barometric pressure differences, and variation in measurement accuracy on dynos could easily explain that difference.
You would also need to know if both dynos were the same type and using the same correction factor. Even if the two dynos were the same type, and used the same correction factors, variations in the absolute air temperature, humidity and absolute barometric pressure, tire pressure/type, and tie down method (assuming it was a chassis type dyno) could all take their piece of the pie.
Larry
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Larry,
I havent seen the new numbers, it was only a call....What I can tell you is that they are both new (within the past 12 months) Dynojet dynos....Who knows what correction factors are "stock" or normally corrected for/calculated.
Hopefully i'll get to see the charts when the shop reopens for the first time in 2012.
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Alan, there can be this amount of variation with two chassis dynos. Tire condition, how tight the bike is tied down to the dyno, the operator's individual methods, etc. It is nothing to worry about if all other engine health indicators are OK.
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I did a bunch of reading, apparently the loss of torque maybe normal, especially when taking a stock engine and pushing it for more peak hp... I'll have to wait till I get it back on the Island to bring it back to the baseline dyno to see how it actually compares. I dont know rpm for the news values yet....
Once the carbs are dialed in, what kind of performance gain might it possible to get from ignition tuning? 1-4%??? Justa general number, I know theres alot of variables to take into consideration, i am just asking about a general idea of how many more ponies we can might wring out. I know my mechanic knows how, I am asking here because he's in a different state and it costs me nothing to ask here. If i ask at the shop somehow he'll find a way to charge me for his time ;-)
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hope this works, its a pdf of my 1st dyno pull...some room for improvement is evident
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"Pushing"? Did you do any tuning between the dyno runs?
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uhm, yes
everything
cams,
carbs,
pistons,
rods,
intake porting,
exhaust,
ignition module,
diet (both me and the bike)
on
and
on
I say pushing because at a 20% increase over stock, I am guessing we are nearing the limit with bolt on parts. To get more we would have to do more physical engineering (ie boring, machining etc)
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Could be because it is really lean.
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Really lean. Should be in the neighborhood of 12.6-12.8
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It seems that your standard motor put out 57 hp with 52 pounds foot torque and your modified one makes 68 hp with 47 pounds foot torque. Hopefully I am interpreting this right.
It is possible to get more peak hp with less peak torque. The graph shows some data from 2010. Everything was identical except for the intake. In one set of runs I used velocity stacks and in the other set there were pod filters on the carbs. The pod filter setup put out 68 hp and the stack setup made 71 hp. Note how the pod filters produced more torque than the stacks. The stacks moved the torque curve a few hundred rpm higher and they made more hp with less peak torque.
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Depending on his comp ratio he may not need to go to 12.6,Fred. That is actually a bit rich. Around 13.2-13.6 may be better. But looked like he headed to 14+ in the upper rpms and that was lean.
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my compression ratio is 12:1
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The Triumph shop who helps me does my dyno work. The fellow who runs the dyno sets the jetting to produce maximum power rather than to a desired air fuel mixture. It works. The bike runs great.
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The Triumph shop who helps me does my dyno work. The fellow who runs the dyno sets the jetting to produce maximum power rather than to a desired air fuel mixture. It works. The bike runs great.
Absolutely right. Give the engine what it wants. Don't be trying to shoot for some "magic" AF number. There is none. Just changing the fuel could change what it wants, let alone all the other possibles.