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[Ironhorse]

I'm not sure this is the correct area to post this, moderators please feel free to move it.



The bike is a bone stock CVO 103. Stock heads, cams and throttle body. Only changes is a true dual conversion kit and D&D 1.75 Police Interceptor slip-ons. Tuned with a TTS Mastertune - Blue Dongle.

The first tune was done by Bob Lobenberg in the bay area on a DynoJet dyno. The bike had a "Y" pipe and Bob got his readings off sensors he stuck up the tailpipes.

The second tune was done Gene Thomason on a SuperFlow Dyno. The bike now has a "True Duals" conversion kit. I made the change over after cracking my "Y" pipe. Gene got his readings off O2 sensors installed in bungs in the headpipes.

Both tuners are well respected in their field.

I'm not concerned about the numbers being different. I understand enough to know that numbers cannot be compared off two different dyno machines.

What I do find interesting is the curve. The tune by Lobenberg has a "Peak" at 4k rpm, where as the tune by Thomasen is "Flatter" from 3K to 4.2K, in what I call the rideability range.

My question to the dyno guys is, since the build is the same, could this be the result of changing from a "Y" to a "True Dual" conversion kit? I always heard that when going to "True Duals", one looses low end torque. Maybe I'm not seeing it here.

Any other comments?

Mark

[grc]

I think if you were to plot the curves on one chart using the same scale for both, you would find that there really isn't that much difference in the shape of the curves in the rpm range you mentioned.  I didn't bother to try to pick out individual data points and superimpose them on the other chart, but you could do that with full size copies if you like. 

Jerry

[Ironhorse]

Thanks for that Jerry. So then I guess, there is no difference and no loss going from a "Y" to "True Duals". No significant losses, and gains either. Interesting.

[ltank]

Dyno Runs are no always spot on. You take the same Bike on the same dyno but let two different people secure the bike and yo can get different readings as you would with two different operators.

[tweeter13]

It's hard for me to read them on my computer. But I don't see a air fuel ratio on the one on the right.  The one on the right to me appears to be leaner than I would like to see in my opinion but I could be wrong.  I would like to see what some of the guys that run a dyno say. 

Todd. 

[Ironhorse]

Tweeter13, I guess I should have asked him for the AFR reading, however I was more interested in the TQ curve. The bike is not exhibiting and signs of being lean, at least so far. More will be revealed in the heat of summer.

ltank, I know enough to understand that dyno sheets and numbers can be deceiving. That is why I do not chase numbers, but rather rideability. As for it not being spot on, well my butt dyno can't really tell how much more tweaking it needs. Thomasen did say that further tweaking would not yield any further significant gains for streetability. I do agree that different tuners and different machines will yield different results. But are the differences significant enough? I'm not sure, so I will defer to your expertise in this area.

I was just curious about the torque curves and wanted to know if that was the result of going to the True Dual exhaust.

[Trapperdog]

All that extra smog in SoCal robbed your numbers on the second dyno Mark 

[Ironhorse]

All that extra smog in SoCal robbed your numbers on the second dyno Mark 

And the gasoline here is lower in octane too Roger!

[Doc 1]

True duals got a bad rap in the days of Rinehart True duals......it wasn't so much the header pipe that was the tq robber in the lower rpm's. The 2.5'' mufflers were the biggest problem with the tq drop. Not all True duals kill the lower rpm area. Rush true duals with the 2'' baffle work well for an example.
Doc

[Fullsac Performance]

True duals got a bad rap in the days of Rinehart True duals......it wasn't so much the header pipe that was the tq robber in the lower rpm's. The 2.5'' mufflers were the biggest problem with the tq drop. Not all True duals kill the lower rpm area. Rush true duals with the 2'' baffle work well for an example.
Doc

100% spot on! And back in those days the Rineharts were on little 88" motors. TQ curves were destroyed and all True Duals
were classified the same.

steve@fullsac.com

[OBB]

True duals got a bad rap in the days of Rinehart True duals......it wasn't so much the header pipe that was the tq robber in the lower rpm's. The 2.5'' mufflers were the biggest problem with the tq drop. Not all True duals kill the lower rpm area. Rush true duals with the 2'' baffle work well for an example.
Doc

100% spot on! And back in those days the Rineharts were on little 88" motors. TQ curves were destroyed and all True Duals
were classified the same.

steve@fullsac.com

Great,,, now you two have those little cog$ in my brain turning again. I heard a $et of them at Maggie Valley a few month$ ago and loved them.

[Ironhorse]

OBB,

I gotta say I am very pleased with my FullSac TrueDual conversion kit and 1.75" baffles. I like the conversion kit as it keeps OEM clearances. The Rineharts stuck out too far for me.

Mark

[Fullsac Performance]

OBB,

I gotta say I am very pleased with my FullSac TrueDual conversion kit and 1.75" baffles. I like the conversion kit as it keeps OEM clearances. The Rineharts stuck out too far for me.

Mark

If you stay with  1.75-2.0 cores in the mufflers your bottom end power is still OK, but you will still be 5-6 HP down over compared to an X Pipe or a good 2 into 1.

SG

[FLTRI]

Mark,
I believe if you were to ask Gene to furnish a sheet using the "Dynojet" calculation the numbers would be very close as well as the curve.
Pipe selection on a stock/mild builds are much more forgiving than selection for high performance/high compression builds.
Take the 2 sheets and superimpose them against the light and you will see the difference between the exhausts...it isn't much!
While the "y" pipe system had a very successful life span it became obvious when o2 sensors were installed, the "y" system didn't supply the rear cylinder o2 sensor with reliable sample quality which, in turn, caused bikes to self-"untune" and start running poorly, especially during slow, in town maneuvering.
Happy New Year,
Bob Lobenberg

[SBB]

Happy New Year,
Bob Lobenberg

Hey Bob!
How you been doing.
Both my bikes with your tune are running great.
I still think you should move back east. California is a long way for me to go for a tune.
Hope all is well with you and yours!


SBB