What happens to the timing if you advance the TPS?
Posted July 15, 2002 - 01:41 PM
Posted July 15, 2002 - 03:07 PM
Here’s what I know.
TPS positions are used to make computations based on a pre set map within the control unit.
On this bike, the CDI is the control unit, and within it is most likely some type of number crunching chip fed by formulas burned into an EPROM with which Yamaha has an algorhythm for what the ignition curve is given throttle application.
The TPS is essentially a potentiometer in which a current is controlled and delivered to the CDI of which dictates position.
Of course when you rotate the TPS clockwise, you're tricking the computer (or shifting your position on the map) causing the map to calculate a more open throttle position, (ie, you're at 1/2 and it thinks your at 3/4).
Now with all that aside, unless someone has managed to download the information in the EPROM, we really don't know what you'll be getting from various changes.
However, during my road race days, (on a different bike) I noted TPS voltage at closed and open positions, then correlated these to performance.
This however, shifted both fuel (EFI) and timing, causing the bike to burn cooler, and produce more power and emissions.
I sure hope someone has a more applicable answer.
If not, try it out and tell us what you find.
Posted July 16, 2002 - 04:05 AM
Good description. Minor point, instead of programming a processor with the algorithms, they just burn a ROM chip with the map. There isn't any fancy electronics, just a ROM lookup table. Think of it as a spreadsheet, rows are RPM, columns are TPS, value in cells are the degrees to advance spark. On the 250F forum, look under 'CDI 101' post.
Posted July 16, 2002 - 04:40 AM
Uh What exactly did the Professor say
All I know in stock from is this
1st gear, 2nd gear 3rd gear Break hard turn left, Hold on real tight, 3rd gear wfo 4th down shift break turn right, keep turning keeeeeepppppp turning oh gad a ktm what to do AHHH BERM SHOT 3rd gear WFO over the ktm
[ July 16, 2002: Message edited by: E.G.O.**** ]
Posted July 16, 2002 - 05:49 AM
I'm just calling the ROM an EPROM, and I'm getting a little too carried away with the issue that there has to be something pulling numbers.
Aka, some form of higher processing power that’s reading the info off the ROM. But please correct me if it's simpler than that.
And I don't know of anyway of getting the info from the ROM without some serious hacking, something I'm clearly not capable of.
I'm sure someone out there has means for a programmable module.
Posted July 16, 2002 - 06:01 AM
I am sure Yamaha would be very perturbed if that is done and published with out written consent.
There is a guy on the cannoondale site that has been hacking his computer. Dont know how far he has gotten, but it is a concept that may work.
If there is a hook up one can hack anything
plus, I would assume Yamaha had the smarts to place a Non Writable rom / eprom in the gizzards of the beast, so one would also have to redesign for a read write rom/eprom
[ July 16, 2002: Message edited by: E.G.O.**** ]
Posted July 16, 2002 - 08:51 AM
Here is a better question that I just thought of. If the TPS is just a pot, Im wondering what the computer does when its open, or completely closed?
Posted July 16, 2002 - 11:23 AM
I guess I should have mentioned a few more things.
Unless a bike comes from the factory tuned for something other than ultimate performance (say emissions or ridibility for the masses), there's not much, if any, benefit in making this modification.
Ignition timing map changes are usually required when something with the machine is modified. The most influential are cam profiles and timing, but higher compression pistons and certain race fuels may warrant some changes as well.
Be cautious because shifts in timing can heat an engine up and may cause damage.
Lastly, what works best with the bike running, may result in a bike that won't start. Since, I'll have to assume there is a "consideration" in the map for a dead engine.
I guess I should have added this disclaimer before I said go out and give it a try.
Sorry about that.
Posted July 16, 2002 - 11:32 AM
Posted July 17, 2002 - 03:49 AM
I assume you'll just disconnect it at the first connector. If you actually take it off the carb, let me know where you find the torx with the dimple in the middle.
Posted July 17, 2002 - 07:15 AM
Lisle Tools makes those.
Most automotive parts stores either carry them, or can get them.
Posted July 17, 2002 - 07:33 AM
Thing is, if the norm seemed that these weren't set correctly from the factory, then there is a good chance that our TPS were set correctly either.
Posted July 17, 2002 - 08:02 AM
well next year im going to be running a 13.5:1 piston, VP fuel, thunder alley pipe and silencer, a milled head with ported and polished intake and maybe ported exhaust.
will i REALLY need to adjust the TPS???
[ July 17, 2002: Message edited by: thumper4life ]
Posted July 17, 2002 - 11:06 AM
First of all, I don't think moving the TPS on this bike is going to do much at all. We'll let Shawn have the final word on that.
Also keep in mind that there's a difference in "changing the map" and "changing the timing", (crank position).
The only thing you may need to do, if anything, is a change in timing - unless you find the bike is impossible to start, or unless you change out your cams.
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