SUPERTUNER
TY 4 Stroke Master
- Joined
- Aug 16, 2003
- Messages
- 1,257
- Reaction score
- 2
- Points
- 691
- Location
- Waterbury, Connecticut
- Website
- www.easterncycleperf.com
Seems as there is some confusion on the TPS switch adjustments that I want to clarify for all of you that don't know these few things.
It has been my experience that Yamaha sets the TPS at approximately .70 from the factory. Naturally there is going to be deviation and tolerances with this setting. Please do not panic when you check yours and it is .698 or .710. It really is not as critical as most people think.
The mechanical happenings when you change your TPS setting:
It is a known scientific fact that you need heat to make horsepower. Because the TPS influences the advance curve, by adjusting the TPS switch to a higher number, this begins the advancing of the ignition sooner in the run. This puts more heat into the combustion chamber. Your engine is a heat pump. How many BTU's of heat you generate is directly relative to how much power you will make for the size of engine you have. Ignition Timing moves the heat your engine is capable of making around. Advancing the ignition timing puts the heat in the combustion chamber where it is required to make power. Retarding the timing puts the heat out in the primary headers of the pipe. Often when customers come to me for our dyno service, we check ignition timing. When we find ourselves struggling to make power with what is supposed to be a powerful engine we usually find that the ignition timing is stock or only slightly advanced. Now these statements apply to both 2 as well as 4 strokes. Let's say we are tuning a 2 stroke engine of 1000cc for Open Pro Stock dragracing. This engine comes in and makes 249 HP on the first few pulls on the dyno. I check the ignition timing and find it to be only slightly advanced. I suggest that the ignition timing be advanced more. We do so and next dynorun we experience a massive power increase with a 6-10 HP gain! The customer is elated but during the recall on the EGT guages, he sees that we only made 950 degree's during the run. Before with the retarded timing we made 1175 or so. The customers usual statement then is..."imagine how much more power we are going to make when we lean the carbs down and get the heat back". I reply..."if you lean it down, you will sieze the engine". The customer looks quizzically at me and I explain it like this...By advancing the timing, we took the heat that the engine is capable of making at moved it back into the combustion chambers where it is needed to make the power. By moving the heat back into the combustion chamber, we moved the better source of the explosion further away from the EGT probe which is located some 12 inches away from the centerline of the sparkplug thereby making the EGT probe not experience as much heat because it is all back in the combustion chamber. Advance timing...put heat in the combustion chamber...retard timing put heat in the pipe where the EGT probes are located. So as you can see, the probes will get hotter quicker with retarded ignition timing but the power will also drop. This puzzles many folks that are used to EGT tuning their engines. For this reason, I don't personally put a tremendous amount of faith in tuning with EGT guages.
Now when you adjust the TPS switches on your RX1, you make the ignition timing begin its advance curve sooner due to the new found relationship of throttle position to TPS switch. What this does is generate heat sooner during the run. This creates a situation where more heat is generated for a longer duration of the dragrace thereby having the engine at a higher output of power for a longer time of the run thereby lowering the ET. Often, what this does to the engine and pipe is it heats the engine, but yet cools the pipe in short dragrace style runs of the sled. This is why you are all experiencing less top end with the TPS readjusted on long runs. A hot pipe will rev higher...a cool pipe will rev lower. This is scientific fact and not only my opinion. However in a dragrace situation, you elapsed time (ET) will be quicker with the timing advanced correctly. This is due to the fact that you make heat sooner during the run thereby putting more power output by the engine for a longer period of the run.
If any of you are trail riding and go on long distance runs at WOT, you will probably experience what may feel like a slower top speed. In many cases it doesn't surprise me that you will slow down because what has happened is that you reached the top speed that your engine is capable of doing in less time. The pipe doesn;t get as hot and you lose top peak RPM as a result. ET wins dragraces, not MPH. Might not be a bad idea for you serious trailriders to leave the TPS setting stock. Use an advanced TPS setting for dragracing only.
Hope this helps some of you.
Freddie
It has been my experience that Yamaha sets the TPS at approximately .70 from the factory. Naturally there is going to be deviation and tolerances with this setting. Please do not panic when you check yours and it is .698 or .710. It really is not as critical as most people think.
The mechanical happenings when you change your TPS setting:
It is a known scientific fact that you need heat to make horsepower. Because the TPS influences the advance curve, by adjusting the TPS switch to a higher number, this begins the advancing of the ignition sooner in the run. This puts more heat into the combustion chamber. Your engine is a heat pump. How many BTU's of heat you generate is directly relative to how much power you will make for the size of engine you have. Ignition Timing moves the heat your engine is capable of making around. Advancing the ignition timing puts the heat in the combustion chamber where it is required to make power. Retarding the timing puts the heat out in the primary headers of the pipe. Often when customers come to me for our dyno service, we check ignition timing. When we find ourselves struggling to make power with what is supposed to be a powerful engine we usually find that the ignition timing is stock or only slightly advanced. Now these statements apply to both 2 as well as 4 strokes. Let's say we are tuning a 2 stroke engine of 1000cc for Open Pro Stock dragracing. This engine comes in and makes 249 HP on the first few pulls on the dyno. I check the ignition timing and find it to be only slightly advanced. I suggest that the ignition timing be advanced more. We do so and next dynorun we experience a massive power increase with a 6-10 HP gain! The customer is elated but during the recall on the EGT guages, he sees that we only made 950 degree's during the run. Before with the retarded timing we made 1175 or so. The customers usual statement then is..."imagine how much more power we are going to make when we lean the carbs down and get the heat back". I reply..."if you lean it down, you will sieze the engine". The customer looks quizzically at me and I explain it like this...By advancing the timing, we took the heat that the engine is capable of making at moved it back into the combustion chambers where it is needed to make the power. By moving the heat back into the combustion chamber, we moved the better source of the explosion further away from the EGT probe which is located some 12 inches away from the centerline of the sparkplug thereby making the EGT probe not experience as much heat because it is all back in the combustion chamber. Advance timing...put heat in the combustion chamber...retard timing put heat in the pipe where the EGT probes are located. So as you can see, the probes will get hotter quicker with retarded ignition timing but the power will also drop. This puzzles many folks that are used to EGT tuning their engines. For this reason, I don't personally put a tremendous amount of faith in tuning with EGT guages.
Now when you adjust the TPS switches on your RX1, you make the ignition timing begin its advance curve sooner due to the new found relationship of throttle position to TPS switch. What this does is generate heat sooner during the run. This creates a situation where more heat is generated for a longer duration of the dragrace thereby having the engine at a higher output of power for a longer time of the run thereby lowering the ET. Often, what this does to the engine and pipe is it heats the engine, but yet cools the pipe in short dragrace style runs of the sled. This is why you are all experiencing less top end with the TPS readjusted on long runs. A hot pipe will rev higher...a cool pipe will rev lower. This is scientific fact and not only my opinion. However in a dragrace situation, you elapsed time (ET) will be quicker with the timing advanced correctly. This is due to the fact that you make heat sooner during the run thereby putting more power output by the engine for a longer period of the run.
If any of you are trail riding and go on long distance runs at WOT, you will probably experience what may feel like a slower top speed. In many cases it doesn't surprise me that you will slow down because what has happened is that you reached the top speed that your engine is capable of doing in less time. The pipe doesn;t get as hot and you lose top peak RPM as a result. ET wins dragraces, not MPH. Might not be a bad idea for you serious trailriders to leave the TPS setting stock. Use an advanced TPS setting for dragracing only.
Hope this helps some of you.
Freddie
POWERHAULIC
VIP Member
Nice post Freddie 8)
SUPERTUNER
TY 4 Stroke Master
- Joined
- Aug 16, 2003
- Messages
- 1,257
- Reaction score
- 2
- Points
- 691
- Location
- Waterbury, Connecticut
- Website
- www.easterncycleperf.com
Nice avatar MXZ900! 8)
Frostbite
TY 4 Stroke God
Sure sounds like the function of a distibutor to me :lol:
Seriously, what do you feel the maximum voltage one should run the TPS at for short bursts? PB
Seriously, what do you feel the maximum voltage one should run the TPS at for short bursts? PB
POWERHAULIC
VIP Member
Nothing wrong with a little healthy exercise is there Freddie :!:
170plus
TY 4 Stroke Junkie
- Joined
- Jan 14, 2004
- Messages
- 541
- Reaction score
- 3
- Points
- 893
- Location
- washburn maine
- Country
- USA
- Snowmobile
- 2021 polaris assault 850,18 sidewinder ltx,14 nitro xtx,06 apex rtx,
exercise is good ,like i said the other day i dont mind watching her run at all 
Blue shadow
TY 4 Stroke Guru
When I am trail riding I leave it stock ,when drag racing I move the tps .It only takes a second to make a change.What I did is drill a 1/4 inch hole in front were you can t get at the second screw .Hope this helps
Great info Supertuner, Thanks. Question for you regaurding turbos. From what I understand Turbos love exhaust heat. Would you gain anything by decreasing the voltage with a turbo?
1xr
Expert
What happens if you retard the tps more than stock, would that increase topend?
SUPERTUNER
TY 4 Stroke Master
- Joined
- Aug 16, 2003
- Messages
- 1,257
- Reaction score
- 2
- Points
- 691
- Location
- Waterbury, Connecticut
- Website
- www.easterncycleperf.com
wildbill said:
While this theory is a commonly known characteristic, I think that way of thinking stems back to years ago when none of the good 4 stroke engines had as elaborate shape to the combustion chamber, so when a lot of exhaust heat is realized, this actually meant that the CC had enough heat in it to make better power. Being that the exhaust sytem heat could be measured, most would think that a hot exhaust makes better power all the while it actually being the heat got transferred back to the CC and that is what created better power. With the better shaped CC's, I think we are seeing a better heating and flame travel (thereby heating the CC better and easier) and this is the reason power is going up.
1xr...good question, but my hunch would be that it would hurt. Once again, you need heat to make HP and taking away heat will produce less power. Of course this is all relavent to wether or not the CC is becoming overheated in the first place. My hunch once again is that it is not...even on long runs. Try it though and let us know what you experience. You may have to make several back to back runs just to get the CC up to a degree of heat that is proficient in making power.
Freddie
spray25
TY 4 Stroke God
wildbill said:
With a turbo I wouldn't think you would want to advance the timing for fear of detonation. Thoughts anyone?
POWERHAULIC
VIP Member
spray, wildbill was referring to retarding the timing with a turbo.
welterracer
TY 4 Stroke God
after riding my warrior after adjusting the TPS i found this... It really didnt make a huge midrange difference.. IT ALLREADY HAD MORE POWER THAN IT COULD GET TO THE GROUND.. BuT it did seem to pull more slowly from 90-100mph.. and took longer to get to 100+
If i get the chance to do it over i will not touch it.. I also had notice that when i would be riding and let off the gas the rpms would stay at 2500 for about 15 seconds before returning to 1500... It didnt do that before!
If i get the chance to do it over i will not touch it.. I also had notice that when i would be riding and let off the gas the rpms would stay at 2500 for about 15 seconds before returning to 1500... It didnt do that before!
