Evo torque and horsepower
Stellar HDF Member
Joined: Aug 2013
Posts: 3,419
Likes: 3,526
From: Texas
below 5252 rpms, torque is always higher than than horsepower. above 5252 rpms, horsepower is higher than torque at 5252 rpms torque and horsepower are the same. You measure torque and calculate horsepower.
12.6 afr is considered best for horsepower.
This is what I tuned to for drag racing, maximum power. I used this for water cooled and air cooled motors. My 1996 Ultra Classic has 10 to 1 wiseco pistons, ev27 cam, about 13.5 is as lean as I can run it with out it running hot.
This was my 1998 Suzuki drag bike, msee how the lines cross at 5252 rpms
12.6 afr is considered best for horsepower.
This is what I tuned to for drag racing, maximum power. I used this for water cooled and air cooled motors. My 1996 Ultra Classic has 10 to 1 wiseco pistons, ev27 cam, about 13.5 is as lean as I can run it with out it running hot.
This was my 1998 Suzuki drag bike, msee how the lines cross at 5252 rpms
Last edited by RLH3175; Jan 1, 2017 at 06:17 PM.
Thread Starter
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Tourer
Joined: Jul 2006
Posts: 298
Likes: 12
From: Villa Rica, Georgia
Ignition is a Dyna 2000 module set on single fire and a dyna coil, screaming eagle plug wires and NGK plugs that Scott included. Checked my build sheet and the pistons are 10.5 to 1. The shop did a compression test and he said it was about 190, if I remember right. Ignition is on curve 3 with a 6 inch voes.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,025
Likes: 7,549
From: Poolville
I went back through your posts and came up with this...Now, with a 190 psi ccp it all calculates out to 10.4:1 really not an optimal compression for the W8 but with a better tuner (which I recommend highly) you might still see 90/90. Not sure how your pipe matches up to the equation. I know Scott really likes to put a Supertrapp to that configuration.... I would definitely go to a 180 main and put the needle on the second grove and a 23 on the pilot (just my suggestion, I'm not a Mikuni guy). In your post of#13 you said "after the tune the guy at the shop said I was lean on the bottom and rich on top, 20 pilot 170 main" so you went to a 25/165. you are very rich on bottom and lean on top........ even the mid is a little rich which would indicate a needle change to step 2.
Your motor is still starving for fuel on the top end.... you can do the swap on the jets yourself or find a new shop. one with a very good reputation.... One more thing I don't know of anyone running a D&D on an Evo. what size are the head pipes? 2"? 1 3/4" is the biggest you want to go on an Evo....
You also said that Scott wanted to do the W6. Is that what he set everything up to and did you later decide to use the W8? cause this just doesn't jive. I know he likes 10.8:1 for the W8 and like others said the W8 build is not as reliable as the W6 and will beat the **** out of your motor.... How do think my crank pin sheared. If you go to my profile and go into my "New Mods" album you will see what a W8 should do at 10.8:1 But then I'm using an S&S E carb...
Your motor is still starving for fuel on the top end.... you can do the swap on the jets yourself or find a new shop. one with a very good reputation.... One more thing I don't know of anyone running a D&D on an Evo. what size are the head pipes? 2"? 1 3/4" is the biggest you want to go on an Evo....
You also said that Scott wanted to do the W6. Is that what he set everything up to and did you later decide to use the W8? cause this just doesn't jive. I know he likes 10.8:1 for the W8 and like others said the W8 build is not as reliable as the W6 and will beat the **** out of your motor.... How do think my crank pin sheared. If you go to my profile and go into my "New Mods" album you will see what a W8 should do at 10.8:1 But then I'm using an S&S E carb...
Last edited by 98hotrodfatboy; Jan 2, 2017 at 08:46 AM.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,070
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From: Ohio
You have a good safe Evo engine build at 10.5 with a W8, you don't have any torque dip in the graph showing a good exhaust and correct parts match. Number 3 setting on the Dyna is soft for a light bike and the engine set up as I suspected so still more on the table.
You can do what you want as we just are making suggestions to your post, it is your engine, several members have posted WOT AFR target isn't 14.0 and suggestions are uniform. I run a 130 at 12.5 AFR because it is safe for a heat building monster prone to sticking pistons, 80"-96" Evo's run best at 13.2-13.4 but a carb isn't a perfect metering device that may drop to 12.8 before cleaning up to 13.0 13.2 13.4, can't buy into perfection. Something else to consider is the dyno run was in a controlled temperature room and not a 98 degree day that will let AFR's go leaner due to more cylinder heat burning the fuel quicker.
Suggestion on the table to richen the main jet 1 and jump the the timing setting to 2 on a light bike, if detonation becomes present pull it back to 3 and done.
You can do what you want as we just are making suggestions to your post, it is your engine, several members have posted WOT AFR target isn't 14.0 and suggestions are uniform. I run a 130 at 12.5 AFR because it is safe for a heat building monster prone to sticking pistons, 80"-96" Evo's run best at 13.2-13.4 but a carb isn't a perfect metering device that may drop to 12.8 before cleaning up to 13.0 13.2 13.4, can't buy into perfection. Something else to consider is the dyno run was in a controlled temperature room and not a 98 degree day that will let AFR's go leaner due to more cylinder heat burning the fuel quicker.
Suggestion on the table to richen the main jet 1 and jump the the timing setting to 2 on a light bike, if detonation becomes present pull it back to 3 and done.
Thread Starter
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Tourer
Joined: Jul 2006
Posts: 298
Likes: 12
From: Villa Rica, Georgia
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