Just a few minutes ago I read another post on the RSR forum stating that the TPS wasn't needed and made no difference in the performance of the Road Star. This isn't true and if anyone's interested I can explain what the difference is and why it's necessary.

'SPLAIN IT TO US LUCY!

Okay but I've got to go to work now and if I don't get a chance to log in at work I'll write it up sometime after I get off at 3:00.

Your going to have to explain what this person said because when i read it it may me a bit confused too. Here is his quote about the 42 carb and only the 42 not the cv carb most have from the factory. Not stepping on your toes here.

The 42 does require the use of a Dyna ignition but, contrary to what some believe it does not need the TPS connection when a Dyna is used... It is just an extra expense that has no measurable or proven difference in ride or performance.

I think you would need it anyways, right!

07roadstar wrote:
Your going to have to explain what this person said because when i read it it may me a bit confused too. Here is his quote about the 42 carb and only the 42 not the cv carb most have from the factory. Not stepping on your toes here.

The 42 does require the use of a Dyna ignition but, contrary to what some believe it does not need the TPS connection when a Dyna is used... It is just an extra expense that has no measurable or proven difference in ride or performance.

I think you would need it anyways, right!
Yes, it's just as important with the stock carb as it is with the HSR carb. The TPS controls timing whichever type of carb one is running. At work now, I'll give a better explanation later including its importance with the Dyna.

Why you need a TPS...I'm surprised Erbman hasn't stepped in here? TPS is for smooth acceleration from takes off....

but were awaiting

Erbman wrote: TPS, VOES, NO MOD: I've run this carb in all configurations. Here's what I noticed on my bike with my final set-up of the TPS mod compared to the VOES or no VOES. 1st let me say this, using a VOES or No VOES I did not notice a concern able difference between the 2. VOES to TPS, I immediately noticed a change in idle tone, sounded more even, I guess you could say. I also noticed a smoother acceleration from a stop, and picked up a few MPG's in city riding (under 45mph) Something else I noticed when my initial TPS install, After tightening down the screws, the resistance changed on me by about 200 ohms lower that where it was set to, idle was way to slow till I corrected the resistance, but it can also be corrected by adjusting the pilot screw richer, but the latter is not the right way to do it, something told me to recheck the resistance, so correct resistance, lean the pilot screw.
Why the TPS, I called and spoke to one of the techs at Dyna, who also so happens to own a Roadie, and also runs the TPS mod. When the TPS is initially set for resistance at idle, the voltage going to the ignition module is approx .8v. WOT curve is achieved at approx 3.5v, but between the .8volts to the voltage that turns the switch to wot curve, every .2v affects the curve. Without the mod you miss out on all these fine points. He too, also felt the results that I did, idle, smoother acceleration.

07roadstar wrote:
Your going to have to explain what this person said because when i read it it may me a bit confused too. Here is his quote about the 42 carb and only the 42 not the cv carb most have from the factory. Not stepping on your toes here.

The 42 does require the use of a Dyna ignition but, contrary to what some believe it does not need the TPS connection when a Dyna is used... It is just an extra expense that has no measurable or proven difference in ride or performance.

I think you would need it anyways, right!

that pic is my bike look alike

Samson wrote:
Why you need a TPS...I'm surprised Erbman hasn't stepped in here? TPS is for smooth acceleration from takes off....

but were awaiting

Erbman wrote: TPS, VOES, NO MOD: I've run this carb in all configurations. Here's what I noticed on my bike with my final set-up of the TPS mod compared to the VOES or no VOES. 1st let me say this, using a VOES or No VOES I did not notice a concern able difference between the 2. VOES to TPS, I immediately noticed a change in idle tone, sounded more even, I guess you could say. I also noticed a smoother acceleration from a stop, and picked up a few MPG's in city riding (under 45mph) Something else I noticed when my initial TPS install, After tightening down the screws, the resistance changed on me by about 200 ohms lower that where it was set to, idle was way to slow till I corrected the resistance, but it can also be corrected by adjusting the pilot screw richer, but the latter is not the right way to do it, something told me to recheck the resistance, so correct resistance, lean the pilot screw.
Why the TPS, I called and spoke to one of the techs at Dyna, who also so happens to own a Roadie, and also runs the TPS mod. When the TPS is initially set for resistance at idle, the voltage going to the ignition module is approx .8v. WOT curve is achieved at approx 3.5v, but between the .8volts to the voltage that turns the switch to wot curve, every .2v affects the curve. Without the mod you miss out on all these fine points. He too, also felt the results that I did, idle, smoother acceleration.

Well geeze, would ya give a guy a chance to go read, and who said it. Last time we had words on this issue, he had never tried one on the Roadie, but on the Vstar 1100 I think is what he told me. I don't and won't make a comparison to an apple and an orange, if you get the gist. On a similar note, I only know of one person who said he felt no difference in any way when he installed the TPS mod, oh well, what can I say. All my comments were strictly based on my observations and no diagnostic testing since a dyna run was not going to show any performance gains since the TPS has no effect on a WOT run, the ignition module will be at WOT timing with a TPS or no TPS.
As I said, there was a distinct difference in exhaust note tone, and I don't have the best of hearing, so if I can hear that difference at idle, and the only change was the TPS, seems the only logical explanation is the TPS. The additional of a few mpg better in city riding, was based on multiple tanks of gas, not just one or 2, probably closer to 8 to 10 tanks. There are plenty of others that have done this mod, and I have not heard of any negativity about it. I just use common sense, if in closed throttle curve, there is a slight timing change for every .2v and we are approx. at .8v at idle and WOT timing starts at 3.5v (for arguements sake), there are approx 13 timing changes before WOT. How can that not affect performance in the low end???

Any way, thats my take
use what ya need, toss the rest

Ok, I'm back and I'll try to explain although Erbman has done a pretty good job.

Back when cars used distributors there were two separate mechanical advance mechanisms. The flyweights which advanced the ignition according to engine speed and the vacuum advance which added in more advance during light throttle operation. The engine would run without the vacuum advance connected just not as well during light loads. During full throttle the spring in the vacuum advance mechanism overcame the low vacuum signal and shut it off. That old fashioned system worked very well.

Now the TPS - It can be thought of as the electronic equivalent of the old vacuum advance. At low throttle openings the TPS signals the igniter that the load is low and more timing advance can be added over and above what has already been added according to engine speed. Disconnect the TPS and the only advance the timing will get is whatever was determined by the engineer to be the maximum the engine can sustain at full throttle at any given engine speed..

Like Erbman said the engine will run the same at full throttle without the TPS but you'll give up the efficiency and extra fuel mileage available at light throttle loads. Which is probably where most of us spend the majority of our time anyway.

Any of the aftermarket ignition boxes are the same, if they use the TPS signal them maybe they can help performance but if not then it would seem to me to be a step backwards.

Questions?

Well nice bike you have there too!!