TPI adjustment?

[atomicbass2]

Does the throttle position sensor effect the wide open performance or only the idle? The motor is a '99 225 vmax Thanks.

[Hamfisted]

Its used throughout the throttle range to coordinate fuel delivery and spark timing advance. It has a lower voltage limit (.48v) and an upper voltage limit at WOT (5.25v), measured between the pink and the orange leads coming off the TPS with the key ON. You may not see a full 5.25v at the WOT position in your particular setup, but that is the upper limit of the switch. It's more common to see 4-4.2v at the normal WOT position.

-Mike

[atomicbass2]

Thank you Mike...I appreciate your response and sharing. If I may request a little more time ... based your reply... (spark timing advance) would that mean that an incorrectly set TPS may prevent the motor from reaching maximum rpms at full throttle? That would be based on all other variables being correct such as prop selection,fuel volume,compression,etc.... Thanks again for your time and sharing of your knowledge.

[Hamfisted]

Well, I've found my motor runs best (will pull the highest rpm...) if I adjust the TPS to achieve it's max available voltage at WOT, as long as it still shows about .60v-.62v in the idle position. I know the book says .48v-.52v with the idle screw backed off, but that equates to the .60v-.62v when the screw is adjusted for normal idle.


-Mike

[crf34]

Do you need any special tools to check this besides a volt meter on a 175 HPDI

Thanks

[Hamfisted]

With the HPDI you can read it from the Yamaha Diagnostic System plugged into the motor's ECU, or you can just read it between the pink and orange wires there on the TPS with a multimeter (with the key ON...). I've seen people splice in their own leads with capped ends so they could read it easier too (using heat shrink sealed butt splices...). Or Yamaha sells a harness plug that does the same thing if you don't mind paying for it.


-Mike

[crf34]

Thanks alot Mike

[ghind]

I did this just yesterday on a 2002 Ox66 225

I had the proper harness which was handy

The service manual said to disconnect the throttle linkage from the top butterfly. This let the top butterfly close fully. Then the idle screw has no effect and even if your butterflies aren't in perfect sync with each other, you won't have one holding the other open as they are not connected.

You adjust the TPS until it reads between 0.5 and 0.52 volts.

At 730rpm, the TPS will read about 0.62 volts. Be careful to have your multimeter on the right range. There is a lot of difference between 50mv and 0.5 volts for example.

This all applies to the 2002 VX225 and may be different for other motors. get the service manual, it is really, really good.

I also did a sync and link (all the butterflies are now in perfect sync) and set the oil pump linkage.

[reelman]

I got all new fuel diaphrams last summer... (2000 model V-Max 200 hp)
so why should my 3.1 hit top speed for 15 seconds or so then drop 3-4mph on GPS... then gain most of it back slowly...?? I suspect fouled plug or something with fuel but maybe its the TPI.. talk to me... thanks...