Cheapest DIY Servo Bypass

Yeah, I read it. Until I see more concrete proof, I still hold firm that my little free resistor mod gave me what I needed (as have others who have done it). From what I've seen, with my own use and also following Dr Steve's build, the servo resistor and Graves plug do the same job. I have yet to see someone that's taken one of those plug n play units apart to see exactly what's involved.

SheWolf wrote:

Yeah, I read it. Until I see more concrete proof, I still hold firm that my little free resistor mod gave me what I needed (as have others who have done it). From what I've seen, with my own use and also following Dr Steve's build, the servo resistor and Graves plug do the same job. I have yet to see someone that's taken one of those plug n play units apart to see exactly what's involved.

If you look at Steve's design it uses resistors.

There's no other way for the graves expensive pos to accomplish what it does without using resistors.

The 5 cent trick.........................uses a resistor.

The main debate though would be does the servo actually send information back to the ECU or is that just a one-way street?

Something comes from the ECU to tell the servo to move the EXUP one way or the other. Does the servo then send anything back to the ECU?

I'd be shocked to hear that it does. Not sure why it would.

If no information is being relayed back to ECU from servo, then any claims to increased power or performance regardless of how you alter the servo are simply wishes in the wind.

I would also assume that if the Graves piece has any performance advantage it would be advertised heavily. We've all spent lots of money for more performance.
Here's the description from Graves:

Quote :

Graves Motorsports EXUP Servo Eliminator Yamaha R1 2002-2003 + 2007-2008, R6 2006-2012, WR250X/R 2008-2011 and FZ1 2006-2011.

Description: Graves Motorsports Universal EXUP Eliminator is a simple plug-and-play application that allows the removal of the EXUP valve and motor without setting the "Check Engine light" being activated when using a full racing exhaust. Furthers the weight savings after EXUP removal and allows for a cleaner appearance. It will eliminate error codes 17 & 18 ONLY.

No mention of any performance enhancing what-so-ever.

My point exactly. Simple. If it's simple, then there can't possibly be anything more than what's been done with the resistor. It does the same job the resistor does, just costs a helluva lot more.

I'll preface this post by saying I am no expert, and the only way to know for sure if the EXUP motor feedsback into the ECU and changes anything with fuel curve, would be to do a back to back dyno run( actual dyno..not butt dyno) with the resistor in and with the motor itself in.

This is my theory, based on what I think I know.

1. The Yamaha EXUP system, both on this bike and others, serves a two fold function. One is to lower exhaust noise at idle, and the second, and more important, is to increase torque at lower RPM. These motors, and the inline four design they are based off of, do not typically make a lot of power down low in the RPM range. Not a big deal when you have four cylinders firing. Bigger deal when you only have one cylinder.

2. Based on looking at the wiring diagrams, I think the "other" wires do not feed back into the ECU..but instead get further input FROM the ECU/ other sensors. The wires going to the motor, are also tied into the speed sensor and throttle position sensor. Being that you need the valve closed at lower RPM to make more torque, and more open at higher RPM to make more HP, it would make sense to have these sensors feed into the control of the motor. Almost like a PLC loop system.

3. Japanese do not typically make things more complicated than they need to be. Germans and British do enough of that.

4. CEL's are usually thrown when a sensor is not working. The ECU's only get the idea that something is not working, when it does not get the resistance back to the ECU. Only one set of wires is needed for that. Thus, why a resistor is only needed to connect two pins.

Conclusion: Based on what I mention above, I personally feel there is no difference between the resistor cheap fix and the Graves unit. My guess is that if someone smashed the graves unit, it would just be either one resistor, or a couple, still doing the same thing , and just tricking the ECU into thinking the motor was still there working, in place.

Doug, there's a huge debate over what the EXUP does.

Many will side with the camp that it's ONLY an emissions and noise device.

It there was any power benefit at any place in the powerband why wouldn't race teams and aftermarket pipe manufacturers include such a device in their products?

Why wouldn't Honda and all the other companies utilize something of that nature?

I don't say you're wrong - just that there's wiggle room for much debate regarding the EXUP and what it does.

Which further complicates the idea that the Graves unit provides any performance advantage at all.

Racing is not apples to apples comparison, since they are never interested in the lower part of the RPM range, to put around at low speed. High speed, high power, high RPM is typically what they are interested in.


Not that Wiki knows all, but makes sense to me:

http://en.wikipedia.org/wiki/Four-stroke_power_valve_system

As I said....it's a debate.......

DougZ wrote:

...
2. Based on looking at the wiring diagrams, I think the "other" wires do not feed back into the ECU..but instead get further input FROM the ECU/ other sensors. The wires going to the motor, are also tied into the speed sensor and throttle position sensor. Being that you need the valve closed at lower RPM to make more torque, and more open at higher RPM to make more HP, it would make sense to have these sensors feed into the control of the motor. Almost like a PLC loop system.

3. Japanese do not typically make things more complicated than they need to be. Germans and British do enough of that.
...
Conclusion: Based on what I mention above, I personally feel there is no difference between the resistor cheap fix and the Graves unit. My guess is that if someone smashed the graves unit, it would just be either one resistor, or a couple, still doing the same thing , and just tricking the ECU into thinking the motor was still there working, in place.

Not that it really changes anything... I believe the "other" wires you were refering to (BL & L) are actually just 5V power and ground. That conclusion is based on those same wires applying power to the TPS. The TPS output depends on those wires supplying steady voltage. Makes me wonder if you just threw us (Americans) under the bus with the Germans and British

My theory on it is that the BL, L & W/R wires function basically just like the TPS except, that instead of it measuring the throttle position, it's measuring the position of the servo motor. If that's accurate, then the W/R wire gives motor position to the ECU. Does the ECU actually use it for anything other than possibly throwing a code 18 (stuck motor)? I have no idea. A good hardware hacker could probably give us a definitive answer. No, I'm not suggesting that someone should hack the ECU, just stating one way that we could get an answer. Dyno test would still provide the best answer IMO.

Now for the fun part: making an assumption about the way the ECU controls the motor and based on the way the "cheap" servo eliminator is connected, it could very easily provide feedback to the ECU that would look exactly like the servo feedback. I'm thinking it should be called the elegant servo eliminator instead of the cheap servo eliminator.

A side note for Motokid, I have a Honda Firebird (CBR) that has an EXUP. According to this wiki page: http://en.wikipedia.org/wiki/Four-stroke_power_valve_system , there are other names for them like HTEV & H-VIX.

yep...I saw that. Thanks.

Here is that link I posted, incase you missed it.

http://en.wikipedia.org/wiki/Four-stroke_power_valve_system

Guilty as charged. Sorry about that! To top it off I called the crotch rocket a firebird when it's actually called a fireblade.

LOL..it's all good.

motokid wrote:

Why wouldn't Honda and all the other companies utilize something of that nature?

They do, but have different names.

Good pickup with Yami making NO POWER CLAIMS with Graves mod.

If we conclude from this that Graves vs Servo has no performance difference. And if we conclude resister vs Servo has no performance difference (based on multiple butt dynos) than that means TwilightZone has picked a correct internet handle to go by.

SABMATIN wrote:

Hello all! I found this sweet little tid-bit while surfing the web today.

http://www.yamahafz1oa.com/forum/showthread.php?t=109692
Has a post for a plug that would mate up with the male plug when you unplug the EXUP servo.





6 Position .090 Waterproof Connector Female Half.

Fits wires from .5mm - 1.25mm (22 - 16 AWG).

Tough plastic housing with inner seal. Seals on each wire.

Used for ExUP Connector on some Yamahas.
RFW 6P090-Female


6 Position .090 Waterproof Connector Female Half.

Fits wires from .5mm - 1.25mm (22 - 16 AWG).

Tough plastic housing with inner seal. Seals on each wire.

RFW 6P090-Female

http://easternbeaver.com/Main/Elec__...FKWH/fkwh.html

You can use this to connect the SheWolf resistor fix. YOU MUST ORDER 3 to get the base price over $20 or the shipping will be around $300.... If you order 3 the shipping and total is only $25

Must be an issue shipping from China. I believe I may do this, do the SheWolf resistor fix and then fill the open end of the plug with Silicone. That way it is waterproof and quickly unplugged if stock parts need to be reinstalled.

Not sure if we need the Male or the Female half? What do you all think?

Hey guys, I want this connetcor but when I go to the web site it says : 306$ for shipping !!!! do you know an other place to buy it without this shipping price ?

>"Good pickup with Yami making NO POWER CLAIMS with Graves mod.

If we conclude from this that Graves vs Servo has no performance difference. And if we conclude resister vs Servo has no performance difference (based on multiple butt dynos) than that means TwilightZone has picked a correct internet handle to go by."

Hmmm... Notice that I said that the peak power was the same. When the ECU bypass with the resistor comes on, yes it really comes on.
But I feel the power feed is changed in the low to mid-range of the power band. I guess other people could try the servo hooked up (or resistor plug) and resistor. Report back. Try it yourself... see what happens.

Only way for sure is if somebody finds out the ECU and mods... or do multiple dyno tests and examine the low to mid rage of the power band.

The EXUP valve is the absolute last part of the chain of events that happens in the intake, combustion, exhaust equation.

Why would the electronic brain that controls air-fuel mixtures and combustion and what-not care what happens at the EXUP valve?

By that time everything that could happen regarding combustion has already happened.

motokid wrote:

The EXUP valve is the absolute last part of the chain of events that happens in the intake, combustion, exhaust equation.

Why would the electronic brain that controls air-fuel mixtures and combustion and what-not care what happens at the EXUP valve?

By that time everything that could happen regarding combustion has already happened.

Another good point of logic.. Unless someone can come up with concrete evidence that it does more than send an error code to light the cel, i'm sticking with the conclusion that's all it does. Fool the cel anyway you want, the bottom line is no code thrown. Theories that it changes the idle mixture, headlight brightness, clutch freeplay, etc are just speculation & have no solid evidence to support it.

That said, IF someone can show a logical reason to think otherwise, or prove a connection, i'm all ears.

Marylucky wrote:

Hey guys, I want this connetcor but when I go to the web site it says : 306$ for shipping !!!! do you know an other place to buy it without this shipping price ?

My shipping quote was $347! That is 50 times the price of the connector.

Get the price of what you're buying up a bit and shipping will look a lot better. 3 of the 6P090 Female Half connectors and shipping is now showing $4.37.

Heoz wrote:

Get the price of what you're buying up a bit and shipping will look a lot better. 3 of the 6P090 Female Half connectors and shipping is now showing $4.37.

Yeah I just send an email to him and he said to meet 20$ order to have a decent price

motokid wrote:

The EXUP valve is the absolute last part of the chain of events that happens in the intake, combustion, exhaust equation.

Why would the electronic brain that controls air-fuel mixtures and combustion and what-not care what happens at the EXUP valve?

By that time everything that could happen regarding combustion has already happened.

Again, I am not an expert or anything, BUT, from what I have read and know about bikes, exhaust pulsing, and how it affects torque, IMO, its(EXUP) only there for getting some low end power than would not be there if the EXUP was not.

The smaller opening( EXUP partially closed), gives the motor more torque down low where it needs it, and then opens up and allows more flow, up high, where it is not needed. Some back pressure is needed to help create torque. In theory, if you could run a straight pipe, straight back from the header, the length of where the exhaust would be, the bike would have no guts down low. BUT, it would be great on the top end.

Heck, I am not that old, and I have even heard where old Harley guys would tune their exhaust systems by welding a washer on the end of a bolt, on end( think lolipop), and that in the end of their pipes. They could turn the "lolipop" to get the amount of low end and high end they wanted, by altering the amount of back pressure they needed.

Again, I think the resistor is only needed to trick the ECU, and the communication, if there was any, was from the ECU to EXUP based on other sensors like speed sensor, etc telling the EXUP to be open or closed, and NOT, the EXUP telling the ECU where it was. Like you had said..its after the fact.

I used a 1/4W 10K resistor and did the mod. I had no CEL and bike runs fine. I don't really notice a difference, but my bike it pretty much stock.

Thanks Wolf!

DougZ wrote:

motokid wrote:

The EXUP valve is the absolute last part of the chain of events that happens in the intake, combustion, exhaust equation.

Why would the electronic brain that controls air-fuel mixtures and combustion and what-not care what happens at the EXUP valve?

By that time everything that could happen regarding combustion has already happened.

Again, I am not an expert or anything, BUT, from what I have read and know about bikes, exhaust pulsing, and how it affects torque, IMO, its(EXUP) only there for getting some low end power than would not be there if the EXUP was not.

The smaller opening( EXUP partially closed), gives the motor more torque down low where it needs it, and then opens up and allows more flow, up high, where it is not needed. Some back pressure is needed to help create torque. In theory, if you could run a straight pipe, straight back from the header, the length of where the exhaust would be, the bike would have no guts down low. BUT, it would be great on the top end.

Heck, I am not that old, and I have even heard where old Harley guys would tune their exhaust systems by welding a washer on the end of a bolt, on end( think lolipop), and that in the end of their pipes. They could turn the "lolipop" to get the amount of low end and high end they wanted, by altering the amount of back pressure they needed.

Again, I think the resistor is only needed to trick the ECU, and the communication, if there was any, was from the ECU to EXUP based on other sensors like speed sensor, etc telling the EXUP to be open or closed, and NOT, the EXUP telling the ECU where it was. Like you had said..its after the fact.

So if indeed the ECU needs to know if the servo motor is functioning, and that's the only thing it cares about, the resistor trick should provide that feedback. Which is why no resistor throws a CEL code.

Since the American versions of the wr250r/x have no sensors in the exhaust there's no way for the bike to know if there actually is an EXUP valve or not. All that information would come from servo motor. Correct?

As long as the bike "thinks" the servo is operating there should be no performance difference or advantage to using the Graves $60 part over a home-made pc board, or a simple Radio Shack resistor. The resistor provides just enough information to the ECU for it to think the signal sent to the servo has activated the EXUP and therefore whatever compensation are needed get done.

This might again be further complicated by guys like rydnseek who did ride with the CEL code showing, and nothing in the servo plug, and felt no discernible difference in performance or power output.

motokid wrote:

Since the American versions of the wr250r/x have no sensors in the exhaust there's no way for the bike to know if there actually is an EXUP valve or not. All that information would come from servo motor. Correct?

It's concievable that the intake air pressure sensor would measure a difference based on the position of the EXUP valve. I'm certainly not giving it much credence though.

motokid wrote:

As long as the bike "thinks" the servo is operating there should be no performance difference or advantage to using the Graves $60 part over a home-made pc board, or a simple Radio Shack resistor. The resistor provides just enough information to the ECU for it to think the signal sent to the servo has activated the EXUP and therefore whatever compensation are needed get done.

It's also possible that the resistor provides enough feedback to prevent the error light and make it appear that the motor is moving. But, it might not give the same indication as the potentiometer that's in the servo. In which case it might cause some extra work for the ECU as it might be trying to adjust the valve position over and over.

Seems a simple test for the above with the resistor in use would be to use a digital meter like the ones that folks use to watch their battery. Connect the meter to the leads used to move the servo (B/G & B/R), and go ride. If the voltage is fluctuating repeatedly when the valve is adjusted, then the ECU is getting a workout. After the info that follows though, I'm having a doubt that the valve moves enough that one would even see it on the digital meter.

I found this link describing the EXUP on a 4 cly engine: http://www.yamaha-motor.ca/technology/technology.php?group=M&tech=EUP

I also found where people are saying that the exup valve is sprung in the open position on the WR. Further, when the bike is started and idling that the valve stays in the open position. After watching the video that mtb posted years ago (mtb's last post in this thread) https://wr250rforum.forumotion.com/t651-exup-when-will-it-work?highlight=exup , I'm having a serious doubt about the EXUP being more than a paper weight.

Perhaps mtb had some mods that had an affect on the EXUPs function. Would be nice to see a video like that one on a completely stock bike.

I also found an elaborate R1 exup replacement circuit: http://biketransplant.tripod.com/exup_replacement.gif

Thanks for posting that thread with mtb's video. I kept thinking about looking for it but never got around to doing it.

Yes...as stated earlier, there's lots of debate about what the EXUP does and that many people think it's mainly a pollution and/or noise device and nothing more.

How would an intake air pressure sensor get any information from some place roughly 10 inches away from the cylinder on the exhaust side of the equation?