Evo torque and horsepower
Seasoned HDF Member
Joined: Nov 2009
Posts: 15,705
Likes: 22,718
From: Farmington ,MS
The first thing you need to know is...HP is a math formula.
Dyno's do not measure HP...all they measure is torque...
Numbers can vary greatly...depending on the operator, AND the weather.
The only way you are going to get much improvement on those numbers is to: increase the CID, or dramatically shorten the life of the engine...with mods that make the engine very "peaky" and not fun to ride on the street...but looks good on a dyno sheet.
That all depends on what RPM your "torque peak" occurred at...yours occurred at 5,437 RPM...if you had a little smaller cam, or more cubic inches... your torque would be higher than your HP.
Last edited by Tom84FXST; Jan 1, 2017 at 12:31 PM.
Club Member
Joined: Aug 2008
Posts: 22,840
Likes: 17,868
From: Lafayette, Louisiana
Chasing 3 hp will likely result in blowing up the engine at the worst or emptying your bank account at the best.
You repeatedly state you are blown away by how it feels and how it rides. Since that is the case, who needs a dyno printout?
Besides torque in the low to mid rpm is what will make a Harley fun to ride on the street. A high rpm big twin with very little low rpm torque might be good on a race track, but in most daily riding is far from ideal.
You repeatedly state you are blown away by how it feels and how it rides. Since that is the case, who needs a dyno printout?
Besides torque in the low to mid rpm is what will make a Harley fun to ride on the street. A high rpm big twin with very little low rpm torque might be good on a race track, but in most daily riding is far from ideal.
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Tourer
Joined: Jul 2006
Posts: 298
Likes: 12
From: Villa Rica, Georgia
Thanks again guys, I probably would have been better off with the woods 6 cam the Scott told me about first. The reason for the dyno tune was 1- to satisfy my curiousity and 2- I kept playing with the jetting and had no idea which way I was going, after the tune the guy at the shop said I was lean on the bottom and rich on top, 20 pilot 170 main. It has a 25 pilot and a 165 main now with the stock needle in the center notch.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,023
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From: Poolville
Last year, 2016, I had the engine in my 98 fxdl rebuilt by Hillside Cycle. Stage 2 heads, woods 8 cam, S&S roller lifters and rockers, HSR 42 with the round mikuni filter that clamps right on the carb with no adapter, and some other goodies. I didn't go big bore but the cylinders were cleaned up for the wiseco pistons, I think they are 10 or 10.5 to 1. I did the heat cycles and break in recommended by Hillside. I had a RBRacing prostock pipe on it for a while then switched to a D&D fatcat, sounded like I had a nascar stock car behind me with the RB pipe. The bike runs like a freight train and seemed to have endless power. At around 1200 miles I had it dyno tuned by a small independent shop here in Georgia. I ened up with 88 hp and 85 ft. lbs. of torque, I was thinking I would see numbers in the low to mid 90's on both. I thought the torque would be higher than the hp, that has me bit confused. My question is should I have it tuned again at another shop or are those some good numbers? I'm still in the learning process about tuning Harleys. What do you guys think? Thanks, and A Happy New Year to everybody.
First off I would like to thank you guys fot the remembrance of the 3 hp.... I have a tear in my right eye..... Lol... Thanx....
I am extremely familiar with that W8, stage II heads build from Scott. Can you please posts dyno sheet and i will decifer it for you. I don't believe you have it tuned properly. A 170 main is very lean for that build and Will keep your numbers low.. Also a W8 wants 10.7-10.8 static.. At 10-10.5 a W6 with a different pipe would give you the same numbers you currently have.... You should be running a. AFR of 13.2-13.4 for that build.... Not big on 42 mik either.... Did you have the intake opened up? Do a compression test and post The ccp as well...
Dyno sheet....... Please....
Last edited by 98hotrodfatboy; Jan 1, 2017 at 04:39 PM.
FWIW, in my opinion, peak HP numbers on IC engines used on the street are meaningless. Ignore them.
Single numbers for torque are also nearly worthless.
What matters is the shape of the torque curve. You want a smooth ramp up to about 1500 or 2k RPM, and a nice, flat curve from there up to around 4k or 5k ish RPM.
As mentioned, there is too much variability in the dynamometer process to worry about small differences (say, less than 5%).
Single numbers for torque are also nearly worthless.
What matters is the shape of the torque curve. You want a smooth ramp up to about 1500 or 2k RPM, and a nice, flat curve from there up to around 4k or 5k ish RPM.
As mentioned, there is too much variability in the dynamometer process to worry about small differences (say, less than 5%).
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,070
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From: Ohio
14.0 is on the lean side and actually can cost you horsepower numbers at that setting, yes the term lean in mean is true but you need to be at 13.2-13.4 as mentioned. Personally I wouldn't hesitate to change the main jet 1 jet richer and will be at your target, 14.0 isn't what you would say "safe" jetting with a warmed up air cooled Evo, it will live but not a target area.
More info is at 14.0 a warmed up Harley engine should be on the edge of detonation or detonating, I'll bet the timing is pulled back to control the carb cross over detonation area which means timing pulled is horsepower lost when splitting numbers. Richen the main jet and move the timing advanced 1 setting if adjustable. When monitoring AFR's each degree of timing change affects AFR by example 13.8 basically drops to 13.7 richer with 1 degree of timing pulled back but pulling timing isn't a goal to get correct AFR's, the dyno tuner may said close enough and didn't want to make 1 more jet change to be perfect.
More info is at 14.0 a warmed up Harley engine should be on the edge of detonation or detonating, I'll bet the timing is pulled back to control the carb cross over detonation area which means timing pulled is horsepower lost when splitting numbers. Richen the main jet and move the timing advanced 1 setting if adjustable. When monitoring AFR's each degree of timing change affects AFR by example 13.8 basically drops to 13.7 richer with 1 degree of timing pulled back but pulling timing isn't a goal to get correct AFR's, the dyno tuner may said close enough and didn't want to make 1 more jet change to be perfect.
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Seasoned HDF Member
Joined: Aug 2008
Posts: 5,070
Likes: 2,115
From: Ohio
[QUOTE]
]
Your W6 will flip that torque higher and lower the HP slightly, the W8 is at 47 intake opening which means it is letting some air out of the cylinders and looses torque in the lower RPM's but all out in the mid range. A W6 is at 42 intake timing and builds more compression but falls off earlier in the RPM's, a W6H is a good cam that can carry into the 6000 RPM range. With a heavy bike a W6 is the answer, with a light bike just run your set up and there is some more WOT giddy up with AFR's if you choose to chase it.
Chasing max numbers sometimes leads to not able to leave it alone so be aware of that, some of us have already been thru this and just trying to pass on experience. I ended up leaving mine alone after 130 cubes and a death wish was close tuning it in real world riding. We joke now about Hotrod chasing 3 hp but he traveled a tough road and wasn't laughing at that time.
Thanks for the replies. If I'm looking at this readout right it appears the afr is right at 14. The test was run up to 6000 rpm. I always assumed that the torque would be higher than the hp just because of the nature of the engine, thats the part that had me confused. And as for lifting the front wheel, it does get light in the front end, dont think I want to try wheelies with 14 inch apes. When running up through the gears it dam near wants to blow me off the back, definitely a fun ride!![/QUOTE
Your W6 will flip that torque higher and lower the HP slightly, the W8 is at 47 intake opening which means it is letting some air out of the cylinders and looses torque in the lower RPM's but all out in the mid range. A W6 is at 42 intake timing and builds more compression but falls off earlier in the RPM's, a W6H is a good cam that can carry into the 6000 RPM range. With a heavy bike a W6 is the answer, with a light bike just run your set up and there is some more WOT giddy up with AFR's if you choose to chase it.
Chasing max numbers sometimes leads to not able to leave it alone so be aware of that, some of us have already been thru this and just trying to pass on experience. I ended up leaving mine alone after 130 cubes and a death wish was close tuning it in real world riding. We joke now about Hotrod chasing 3 hp but he traveled a tough road and wasn't laughing at that time.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,023
Likes: 7,548
From: Poolville
[QUOTE=1997bagger;15800378]
There it's a lot of truth there bagger. My relentless path did nothing but shear my crank pin....... That time and cost out waighed The pleasure for sure.... Sure It beat up oj 103's and even 110's but it still cost me in The end........
]
Chasing max numbers sometimes leads to not able to leave it alone so be aware of that, some of us have already been thru this and just trying to pass on experience. I ended up leaving mine alone after 130 cubes and a death wish was close tuning it in real world riding. We joke now about Hotrod chasing 3 hp but he traveled a tough road and wasn't laughing at that time.
Chasing max numbers sometimes leads to not able to leave it alone so be aware of that, some of us have already been thru this and just trying to pass on experience. I ended up leaving mine alone after 130 cubes and a death wish was close tuning it in real world riding. We joke now about Hotrod chasing 3 hp but he traveled a tough road and wasn't laughing at that time.