What happened to the torque between two similar builds?

[hdrider47]

I am trying to understand what is different that causes two very similar builds to have 12 pounds of torque difference at 2500 rpm. First build was a 2007 Heritage with 103 kit, se204 cams. se performance heads , flat top pistons, SERT, and Rush Mufflers with 2 inch baffles. The second build is a 2009 Road King with same heads, pistons, 103 kit, and cams. The RK also has Rush mufflers with 2 inch baffles. Both have about 200ccp. The RK has a SEST instead of SERT. Both dyno tuned by same tuner on same dyno.

The differences that I am aware of between the 2 bikes are the throttle-by-wire in the RK, different factory headers, and a larger/heavier rear tire on the RK (180 vs. 150 rear tire). The peak numbers are less on the RK, but not that different (Heritage 104T/89HP vs. RK 101T/85HP. The peak numbers could possibly be explained, at least in part, by a little cooler weather when the Heritage was tuned. The thing I am trying to understand is the large diffence of 12 pounds of torque at 2500 rpm. Could the differences in the throttle, headers, and rear wheel size make this much difference in low end torque? Thanks for any help on this.

[skidmark316]

Which one had the extra 12 ft/lbs?

[Mtclassic]

for one thing they have different gearing. just because they had the same tuner does not mean he got the most out of each of them unless he is a good tuner. He may just have gotten lucky with the one that produced more. If the RK made more torq it may be fl is a little more effecient at putting the power to the rear wheel, on the other hand the big hunk of rubber could be the reason it made less.

[claydbal]

sest, sert, gearing, and balancers. was tire pressure the same? air filters removed, same oil, belt tension, same gas, same station, filled same pump on same day? yada, yada.

also remember the FBW opens slower.

this is a great example why you dont chase numbers, take em to the track.

[splitting_lanes]

Originally Posted by claydbal

also remember the FBW opens slower.

Isn't FBW not fully open until after 3k or something?

[hdrider47]

The Heritage had the higher torque at 2500 rpm, Heritage 92T and RK 80T. The difference in torque are mostly below 3000 rpm. Does anyone know if FBW doesn't open fully until 3000 rpm? If that is true, could that be most of the difference?

[relxn88]

Originally Posted by hdrider47

The Heritage had the higher torque at 2500 rpm, Heritage 92T and RK 80T. The difference in torque are mostly below 3000 rpm. Does anyone know if FBW doesn't open fully until 3000 rpm? If that is true, could that be most of the difference?

I can't be quoted on this, but I think the fly-by-wire will not go over 60% throttle until 3000 rpms. ALSO, I think the SEST has a throttle progressivity adjustment to change the throttle to act the same as cable operated bikes.

[springer-]

Originally Posted by hdrider47

The Heritage had the higher torque at 2500 rpm, Heritage 92T and RK 80T. The difference in torque are mostly below 3000 rpm. Does anyone know if FBW doesn't open fully until 3000 rpm? If that is true, could that be most of the difference?

Actually 2750 RPM. Here is a dyno comparison we did when it first came out. It explains what throttle positions can be achieved at what RPM. This was for an 08 with TBW.

http://www.v-twinforum.com/forums/bi...ert-tuned.html

[hdrider47]

The difference does seem to be right at about 2750 rpm. Will the throttle progress adjustment on SEST overide the 2750 rpm full throttle programming so that you can have full throttle starting at lower rpm with the plates fully open? or, is the SEST adjustment something different?

[BVBOB]

I would guess the biggest influence is the throttle body and pipe, keep in mind if it was done on a dynojet model dyno the heavier tire will have an effect basically because the dynojet is really just an accelerometer, getting the heavier rotating mass takes longer and the torque curve is based on rpm vs time. Now, couple that with the builds being dyno'd at a different time and likely different conditions and I can see where differences can come into play.

[relxn88]

Originally Posted by hdrider47

The difference does seem to be right at about 2750 rpm. Will the throttle progress adjustment on SEST overide the 2750 rpm full throttle programming so that you can have full throttle starting at lower rpm with the plates fully open? or, is the SEST adjustment something different?

My understanding is it allows the user to change the throttle progressivity to match the ecm with the hand grip at any rpm. Same as cable operated bikes. For ex., 100% throttle at 2000rpms would be 100%, not 60%.
I have an older version of the SEST software and it doesn't have this option in it. I think it was the newer, updated, SEST that has this option in it. If your SEST doesn't have it, you can probably update the software in the SEST that you have. Maybe someone else has more info.

[hdrider47]

Does anyone know if the SEST throttle progressivity adjustment gives 100% throttle openings below 2750rpm? If not, wouldn't this result in lower torque at low rpm for all FBW systems using SEST? If SEST doesn't do it, does TTS Mastertune have that ability?

[claydbal]

does this SEST adjustment control the blade and slide? does the slide still fall shut at higher rpm?

[relxn88]

Originally Posted by claydbal

does this SEST adjustment control the blade and slide? does the slide still fall shut at higher rpm?

Claydbal, I believe Doc had posted an explanation with a picture of the actual throttle progressivity constant. I'd post what he said, but I searched and can't find it. I believe he said, the throttle blade will follow what ever is set in the Throttle Progressivity constant. For example, the originial setting for 80% throttle at 2200rpms might be 48%, then the throttle blade would only open 48% instead of 80%. But, if you change the 80% throttle constant (in the SEST table) at all rpms to 80%, the throttle blade will open to 80%(instead of 48%) at all rpms. This should make it just like the cable operated bikes. Both, TTS and the newer SEST can do this.
At least, that's the way I remember it. Maybe somebody would have better luck with a search than I did.

[claydbal]

thanks relaxn, but im curious if it controls the blade, or the slide also. you can hold the throttle open and the slide will fall back shut!