(Off-topic) Throttle body voltage

Not V4 related, not even ducati related so mods, you can move if needed. It's a good little mystery that I'd love to get folks like @bp_SFV4 or @RickD996 or @andyb etc. to weigh in on.

Objective: GP2 stock throttle throw is way too long for me. I am looking for a quick turn throttle.
Background: GP2 uses KTM 890 Duke R motor and throttle. ECU is different.
Sit rep: KTM PowerParts sells a factory quick turn throttle for the 890 Duke. I got my hands on one. Installed on GP2. Ran it around the block and bike runs and butt dyno agrees its quick turn.
Wrinkle: Kramer HQ says yeah no, the new quick turn throttle may drive the throttle, but will mechanically limit full throttle opening.

So I did two things:

1. Hooked up my Bluetooth OBD MX+ scanner to the KTM diagnostic port (with an OBD2 adapter of course) and used the Torque app to pull throttle opening values. I compared both stock throttle at wide open and new KTM quick throttle at wide open. Both outputting same voltage. I repeated the test with engine on in neutral + wide open, and engine on in 4th gear (clutch in, bike still on stand) + wide open. Both throttles read same voltage in all situations.
2. Then I pulled the airbox off and physically verified with my own eyes that the throttle butterflies are opening fully vertical at WOT with the quick turn throttle (engine on, 4th gear and bike on stand with clutch in).

So the mystery - is Kramer HQ just mistaken/unfamiliar with what quick throttle I am using? Or are they correct and is the ECU somehow going to override throttle demand out on track and use hard-coded values basically nullifying quick turn data I am seeing in garage? Keep in mind the GP2 does not have any IMU/TC so ECU doesn't really have to override throttle demand based on other variables. So how it behaves on a stand in garage should be how it behaves out on track, correct??

I'll be on track on Sunday to verify but figured it's worth posting to get some thoughts.

Only one way to find out!

Logic sounds reasonable. Does Kramer offer a qa? Surprised it's not standard.

I would think if you're seeing the same voltage with both throttles at full twist you are good to go. It sounds like with your OBD device you could leave it plugged in and log it on a ride and make sure the value you saw in testing is the value you get on the ride.

bp_SFV4 said:

I would think if you're seeing the same voltage with both throttles at full twist you are good to go. It sounds like with your OBD device you could leave it plugged in and log it on a ride and make sure the value you saw in testing is the value you get on the ride.

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I support this theory.

One way to verify is use an app to measure your acceleration between the two setups, 60-130 or whatever.

OK update in case anyone is curious. Quick throttle is a go. Man what a difference a quick turn throttle makes, I love it. @craig bush I can't wait for Brad to get the Domino throttle back in stock for the V4 before next COTA day.

Thanks all.

TomFoolery said:

OK update in case anyone is curious. Quick throttle is a go. Man what a difference a quick turn throttle makes, I love it. @craig bush I can't wait for Brad to get the Domino throttle back in stock for the V4 before next COTA day.

Thanks all.

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Agreed. I’ll look forward to hearing your impression!

Craig, have you confirmed that the Domino does in fact have less rotation stop to stop than the stock throttle? The Domino literature states a10% reduction (quick turn) but I have both throttles side by side and there is either no difference in degrees of rotation or if there is, I can’t measure it.

Could it be the Domino gets to the voltage for full throttle faster even if the mechanical rotation is the same?

endodoc said:

Craig, have you confirmed that the Domino does in fact have less rotation stop to stop than the stock throttle? The Domino literature states a10% reduction (quick turn) but I have both throttles side by side and there is either no difference in degrees of rotation or if there is, I can’t measure it.

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Sorry buddy - I haven’t.

bp_SFV4 said:

Could it be the Domino gets to the voltage for full throttle faster even if the mechanical rotation is the same?

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Good thought.

What I noticed most about the Domino throttle is how positive and direct it feels.

Domino has 2 pots, same voltage. I will compare graduated voltage graphs tomorrow. I build an interface for the V4 domino throttle that changes the pot voltage to match the 1199/1299 (mits ECU) as Domino doesn’t make a throttle for that series. Now I can change the behavior of the Domino via programming in the interface to do what I want it to do, I can also change the APS mapping in the ECU to open whatever I want at whatever % of throttle I want so skys the limit electronically, however that doesn’t change the mechanical degree of rotation of the throttle itself, maybe. I’m going to hack a Domino sometime this week and look at it mechanically. They supposedly have available different spring rates as well.

craig bush said:

Sorry buddy - I haven’t.




Good thought.

What I noticed most about the Domino throttle is how positive and direct it feels.

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No worries. Agree it’s a super nice piece.

Totally a shotgun guess. Just playing around with my V4 and looking at the values of the various sensors, there's a maximum requested torque which comes on before full throttle. There are so many different values related to the throttle.

Off the top of my head, I'd think you'd want a heavy spring but in practice that may not be the case.

Don’t know. What’s on there is very comfortable. Anyone using the Domino, this mod was nice addition. It’s a machined delrin bushing that fits precisely in the throttle end. I use lithium grease on it and assemble. Takes all the end wobble out of the throttle shaft. Throttle feels like it is on roller bearings. Very enjoyable to ride with and the mod is quick and easy. Dan Kyle used to sell a version for the HRC throttle which is where I pirated the idea.

I'd think the stock V4 throttle would benefit from that.

bp_SFV4 said:

Totally a shotgun guess. Just playing around with my V4 and looking at the values of the various sensors, there's a maximum requested torque which comes on before full throttle. There are so many different values related to the throttle.

Off the top of my head, I'd think you'd want a heavy spring but in practice that may not be the case.

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Throttle spring is a complicated variable. On little race bikes (e.g., Yamaha R3), it is common practice to replace throttle spring with something much lighter. The throttle won't snap back as fast and bike will 'hang' in the power band with less effort. Since you are going to be wide open more than you are going to be closed and when endurance racing for instance, a lighter spring significantly eases stress on throttle hand/wrist. Made a huge difference to my old R3.

With a big beast like the V4, adding all the other electronics such as EBC and TC... I am not sure if lighter spring is better or worse. I remember reading the Domino spring is actually heavier and snaps closed more definitely than stock?

I am with Craig. Its possible domino achieves quicker turn than stock because the voltage it sends for varying degrees of motion could be higher.