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[110tHunDer]

 
A lot of you guys know I had the Zipper's 575 gear-driven cams installed by Bumpus H-D in Memphis, TN last fall.  The bike ran great in Maggie Valley while we were there for the CVO event, but Unbalanced noticed some smoking from the rear cylinder (Rinehart true duals) from time to time.  Then, throughout the trip to the AMA Superbike races in Birmingham, AL this past April, the bike was feeling like it was "missing" in the 2,000 - 3,000 rpm range under a light or steady throttle, and I experienced a lot of popping under decel, until the bike was good and hot (50+ miles into a ride).  As if that was not enough, more people there (JR, TCnBham, 07hd110 and others) witnessed more smoking coming from the left pipe from time to time, and while sitting in line to do the parade lap, I was finally able to see it myself.

To make a long story short, I did not ride the bike much since returning from B'ham because we ended up relocating for my job, but every time I got on the bike I was getting more and more annoyed with the poor driveability of the hesitation/miss and the (sometimes very loud) popping on decel.  So, once we got settled in the new location here, I decided to try to have something done about it and ended up taking it to the local dealer here, Andrae's H-D in Champaign, IL, after some help from JR and Brian Rose, the tech at Bumpus who did the original tune, who did a little bit of "scouting" work for me about the talent there (another long story).

So, to try to get to the point here . . . after all of this my bike has been on 3 different dynos.  It was on 2 different dynos with SE air cleaner, SE slip-ons and a Stage I calibration, one in Peoria and the other in Memphis, and then again on two different dynos after the installation of the Zipper's cams, Feuling oil pump & lifters, and Rinehart true duals, Memphis and here in Champaign.  I thought you might find the variance in the dyno sheets quite interesting, as I did and maybe we can have some discussion about the reasons why all these are so different.

First, the dyno sheet from the dealer in Peoria where I got the bike, after the installation of the SE air cleaner, SE one-piece slip-ons, and Stage I calibration:

[110tHunDer]

 
Next up, the baseline dyno run from Bumpus H-D in Memphis (same configuration as above) and also the final dyno run after the installation of the cams, oil pump & lifters, and Rineharts:

[110tHunDer]

 
Note how close the baseline (blue line) is in the Bumpus graph vs. the one from Peoria:

Peoria Max HP  91
Peoria Max TQ  98

Peoria Max HP  89
Peoria Max TQ  98

Makes sense, same tune, similar results on two different dynos, right?  Also, stellar improvement in both HP and TQ adding the cams and pipes.  HP all the way up to 105 and TQ at 117 - WHOOO HOO!

OK, then.  Now here are the results from the dyno run of just the other day at the dealer nearby:

[Unbalanced]

Brian,

1.  Did anyone look into the smoking of the engine?

2.  Are all 3 dyno's dyno jet 250i's with the latest software on them?   What is the weight of each of the drums?

3.  Could any of them possibly of had one of the fan's blowing in the area of your intake

4.  Was anyone sitting on your bike while the dyno's took place or were they on the side of the bike?

5.  Can you say with certainty that the bike was lined up with the tire and the top of the drum and not on either side of the drum when they were running the pulls on the dyno?

6.   Can you say with certainty that the rear tire had full tread and was at 40 lbs psi ?

7.   Where all of these dyno's closed rooms or open to atmosphere or vacuumed?

8.   Are you sure you have no intake leaks or exhaust leaks anywhere?

9.   Do you have dyno runs from both cylinders from all 3 dyno's.   

Sorry lots of questions, but the main ones are the first 5.   This is why I always ask people that are around me here to go to a dyno like Bragging Rights.   I ask this to be able to compare numbers to give validity, because this anomoly is very common.   I even told Howie that when he finally gets down to florida I would love to get him to have a run done by Jim so that we can see how Jim's dyno compares to joes cycle's dyno.

One of the members on the site had his bike dyno'd in gainesville HD and when he came down to see bragging rights his numbers dropped significantly I think he said like 15 torque and 15 horsepower over what he had seen from gainesville. 

I would love to gather the data and then pose the same question to dynojet or matt grosch and see what they say about why the disparity of numbers.

-harry

[110tHunDer]

 
Yep, just 90 HP and 101 TQ on the baseline run with the exact configuration that Bumpus got the strong numbers with.

Then, in the re-tune, they demonstrate getting another 8 HP and 8 TQ just from tweaking the A/F ratio.  Now, the bike's driveability is MUCH improved and the popping on decel has been totally eliminated . . . and, they say the smoking from the rear cylinder was caused by the rich A/F ratio at that cylinder . . . SO, I am a happy camper, but the BUTT DYNO says there is no noticeable difference whatsoever in the way the bike runs now compared to before the re-tune.

So, a couple of pieces to the puzzle that I have noticed while pondering this is one, Bumpus may have tuned the bike without the air cleaner on (see photo below of the bike hooked up to their dyno).  This could be part of the reason they showed higher HP and TQ numbers and also why the A/F ratio was rich on yesterday's baseline run which was done with the air cleaner on.  And, two, notice that the baseline run (red) on the latest chart was done in fourth gear, but the final line (blue) with the 8 HP and 8 TQ improvement was done in 5th gear.  Could these two things explain some of the differences?

I am sure there are inherent differences in the dynos themselves, but it seems there are a lot of "tricks of the trade" being done to show improvement that may not actually be there in real life.  Who knows, but I find it a little difficult to believe that the slight adjustment in the A/F ratio that is shown in the last graph would be enough to get another 8 HP & TQ and that it may be more related to the run being done in 5th gear vs. 4th.

Like I said, the bike is really running great, so I am really pleased with the new tune that was done, and after a half hour ride, returned to the dealer to let the service manager know how happy I was.  But, the conclusion I've come to is that I will no longer place a lot of confidence or emphasis on specific numbers generated by a dyno, based on the experience with my bike.

Hey, JR, it looks like I may have to give my "100HP Club" shirt back to Bumpus?!

[Unbalanced]

Brian do you have a 6 speed?

If you have a 6speed you would pull a run in 5th not 4th.   If you have a 5 speed you would pull a run in 4th gear.

Yes they are playing little tricks to get numbers or make you believe they did something by running in 4th then showing higher numbers in 5th gear.  If it is a 5 speed.

Tuning the bike without the air cleaner is BS you won't run down the road this way and they can use the fans to help augment air flow.

Did they give you dyno runs from both cylinders cause if they didn't they didnt do you any favors until you can see both and compare the A/F.

BTW if they had not already done this to your map, you can usually gain 4-6 torque easily by raising the 100 percent throttle timing from 3000-5500 up 6 to 8 units with the race tuner or power commander.   Generally Harley's base maps are light on the timing.   

[110tHunDer]

 
Harry, I was working on my last reply when you posted your questions.  #1 is answered there.  As for the rest, I only witnessed the first dyno run (top sheet), and don't know all the details of the individual set-ups at each shop, or how each tech runs the dyno.  Naturally, that could cause some of the differences we're seeing.

I know you have been one of the ones most vocal about the differences from dyno-to-dyno, so I thought you might take some interest in this and have some good questions.  Unfortunately, I don't have all the answers, but the variability is pretty obvious here, particularly the current sheet compared to Bumpus.  As you point out, I wonder if these types of large differences exist with the big-name dyno guys, too.

[110tHunDer]

Brian do you have a 6 speed?

If you have a 6speed you would pull a run in 5th not 4th.   If you have a 5 speed you would pull a run in 4th gear.

Yes they are playing little tricks to get numbers or make you believe they did something by running in 4th then showing higher numbers in 5th gear.  If it is a 5 speed.

Tuning the bike without the air cleaner is BS you won't run down the road this way and they can use the fans to help augment air flow.

Did they give you dyno runs from both cylinders cause if they didn't they didnt do you any favors until you can see both and compare the A/F.

BTW if they had not already done this to your map, you can usually gain 4-6 torque easily by raising the 100 percent throttle timing from 3000-5500 up 6 to 8 units with the race tuner or power commander.   Generally Harley's base maps are light on the timing.   

Harry, the bike is a 5-speed, so yeah, all runs should have been done in 4th gear.  I did not get the dyno runs for both cylinders, but I did ask the service writer when I made the appointment if they would be tuning both cylinders individually and was told yes.  I asked the service manager (different guy) the same question today and was again told yes and given a brief explanation of the process they use of tuning the front cyl. first and then the rear.  He talked about having to take into account the different length of the rear pipe, so his explanation seemed legit and I believe both were tuned separately.  As far as the timing, I was getting some very slight initial pinging this afternoon in the heat and humidity when I dropped the hammer on it in both 4th and 5th gears, so it seems the timing adjustment may have already been done by them.  The bike has never had any pinging before, so it seems some advance must be there now.  The pinging was gone this evening when I rode it again.

[Tbone]

Brian,
I'm glad to hear you got things sorted out and you're happy.
When Neil tuned mine, he implied that temperature and humidity had a huge impact on numbers so my thinking is, if the bike is tuned under the worse case scenario, you're better off than the other way around.
Bob

[Unbalanced]

Tbone,

I agree humidity and temp play into this, but that is why they use SAE Corrected mode to help account at least for some of the differences.  It is not perfect, but from the same type of dyno manufacture I do not believe we should be seeing 10 hp and / or tq swings.   What I would really like to do is to find out who are the guys with conservative dyno's and who are the guys where the numbers just roll off ya know.


Brian,
I would love for one/some any of the guys that has used bragging rights or john golden to then go and just have a pull down at the other to compare then extend that to the shops that are most currently being used like latus, bumpus, charlotte, hal's hd, dr. dyno, carl's speed shop, speeds performance plus etc.      It won't account for all the weather changes, but might give us a good idea of accurracy.   I know bragging rights is a very conservative dyno number giving dyno.  I would love to see some of the guys that have had dyno runs elsewhere bring their bike here if for no other reason than giggles run it on his dyno only because it's one i know well.   I know most guys aren't going to jump out and pay the 35.00 bucks just to get a dyno sheet that will probably show lower than they have, but it is an idea.

Whether there is a length in pipe difference I am still not buying why they didnt give you a dyno sheet from each cylinder it wouldn't cost them a thing since they said they already tuned it.   They owe you at least a dyno run on the other cylinder for your own piece of mind to know it is tuned correctly.

I had some of this timing/fuel knock on my 07 bike recently and while everyone was saying tooo much timing pull it out, I took taking some fuel away and advancing the timing in the lower end say 1750 - 3000 range.  This didn't happen if i steadily rolled through the throttle, but when I went from nothing to WOT you would hear it or if you were in too low an rpm for say 3rd gear turned a corner and got on it, because you didnt down shift you would hear it.

I would not let this continue though whether it is a retard or an advance issue I would get it looked into.   Should take but a few minutes to realize which method will fix it add timing / take fuel   retard timing

Thanks for sharing the dyno sheets, you are right this is soemthing that bugs me.   They should be held to a common standard for final print outs whether it is STD or SAE just make it universal.

-harry

[Fired00d]

This goes along w/what I've been trying to convey to people for a long time... Dyno numbers are just numbers. Dyno's are a great tuning tool to get your bike running properly, but the numbers can be skewed to give those that are more concerned with "bragging rights" something to brag about. People should be more concerned w/a properly running motor then the numbers. If you have it tuned properly and you ride it and the "butt dyno" makes you happy, and you don't have any rideability issues then be happy.

 
Ride Safe,
Fired00d
 

[Unbalanced]

Gary,

I agree to a point.   When you are paying for numbers by X builder it is good to know that when you leave his shop that the numbers you were shooting for were infact the numbers you paid to get.   Let say you pay a guy to give you 120/120 and you seem to have this at his shop, but then you go to 2 or 3 other shops and the numbers are 110/110.   Are you expected to be upset, are you just to take it because he gave you what he said he would on his dyno, or do you take the bike because it runs well, but not what you paid him for based on taking it other places?

This is the part that I have an issue with, not soley that the numbers differ by the day.   Heck 1 to 3 changes in the number not going to care about, but 10 is noticable by the butt dyno where 1 or 3 is not.

[grc]

This goes along w/what I've been trying to convey to people for a long time... Dyno numbers are just numbers. Dyno's are a great tuning tool to get your bike running properly, but the numbers can be skewed to give those that are more concerned with "bragging rights" something to brag about. People should be more concerned w/a properly running motor then the numbers. If you have it tuned properly and you ride it and the "butt dyno" makes you happy, and you don't have any rideability issues then be happy.

 
Ride Safe,
Fired00d
 

I agree completely.  The way most shops have their dyno's set up, it's doubtful you could get the same numbers two days in a row with the same bike and operator.  Most make no effort to control ambient air temp or intake air temp/humidity/barometric pressure, and yet those items make a huge difference with an air cooled normally aspirated engine.  The SAE correction factors don't seem to help standardize the results like they should either.  I know from past experience that they work in a lab quality dyno cell where all the parameters can be closely monitored and controlled, but most DynoJet setups I've seen are far from a controlled environment.

IMHO, the only really important items on a typical DynoJet chart are the AFR and the shape of the torque curve.  If you're looking for bragging rights for your next bench racing session, I'd suggest you forget hanging the dyno chart on the wall and find a local drag strip that holds amateur "run what ya brung" sessions.  Hang the resulting time slip on the wall instead; at least that has some validity.

Jerry

[Fired00d]

Gary,

I agree to a point.   When you are paying for numbers by X builder it is good to know that when you leave his shop that the numbers you were shooting for were infact the numbers you paid to get.   Let say you pay a guy to give you 120/120 and you seem to have this at his shop, but then you go to 2 or 3 other shops and the numbers are 110/110.   Are you expected to be upset, are you just to take it because he gave you what he said he would on his dyno, or do you take the bike because it runs well, but not what you paid him for based on taking it other places?

This is the part that I have an issue with, not soley that the numbers differ by the day.   Heck 1 to 3 changes in the number not going to care about, but 10 is noticable by the butt dyno where 1 or 3 is not.

In the scenario you're giving I would have to say I would accept it as he's provided what he promised. If the bike is running well (tuned properly w/no rideability issues) then I would be happy. I wouldn't expect that mechanic/builder to travel around testing his build on several dyno's to give you an "average" number. More then likely the numbers he is predicting for the build are numbers he's seen previously from this build on his dyno. With all the differences in dyno's/dyno operators and all the "nature" (heat/humidity/altitude) provided differences I feel it's hard to compare dyno numbers from different machines/operators.

 
Ride Safe,
Fired00d
 

[erniezap]

120/120 on one dyno, but 110/110 on another?  This is a tough one due to all of the vaiables involved, but I would tend to be happy if the builder got the numbers from his dyno since that is what he was basing his estimate on.  Hell, if you wanted to be the "dyno king" by showing big numbers, put the big "top end" cam in the bike, remove the ari cleaner, and run 100+ octane racing gas and you'll get all fo the number that you want.  It would be useless since the bike would ride like chit on the 91 octane Califonia gas under normal conditions, but you'd have your bragging rights.   

Dynos are great for giving you before and after pictures of a mod, and for setting AFR.  After that, the butt dyno is what matters.