Finally - I got a chance to install the PCV in the bike and take it into the dyno room. Many of you have asked questions, many have reported problems, some info on the web just confirmed that almost everybody is struggling with the PCV and even more with the Autotune.

While I have not done detailed auto-tune testing - YET - I think I found several possible root causes of why various users and tuners are struggling to get it to work.

First of all the PCV does not behave like the good old PCIII. A custom map made for the PCIII cannot be transposed 1:1 for the PCV. Was a 50:50 chance that they could work, well they do not. Custom maps have to be re-done for the PCV to be precise.

This article is not about horsepower numbers, but rather about how to avoid or solve some very common issues with the PCV on the 2009+ VMax.

Missing Power

This issues has been reported before but I want to make sure that people are aware of it. The PCV gets its power from the injectors only. When the bike is not running and you are trying to go into diagnostics, the missing power on the PCV will mess up the TPS readings and will create an error condition for the ECU. This is the very same behavior as seen on the 2009 R1. 

Have seen posts on the internet that made people get ride of the PCV because of that because they thought something is wrong. The work around is simple: Connect the PCV to USB so it has the power it needs when you go into diag mode. Alternatively you can wire the red power cable from the PCV into the red/blue switched power on the bike. That way the PCV gets constant 12V whenever the ignition is on - even if the engine is not running.

Bad, Bad Digital Ground

If you have been around with the RS Warrior and the PCIII this might bring back bad memories. Remember the days when Warriors would surge, idle badly, ride sloppy and simply not run right?

If this is news to you check out this old article form 2003 on rswarrior.com: Perfect PCIII Install

Well, it turns out Dynojet did it again: they laid down another golden egg for us. Lets make the PCV install simple and combine digital and regular ground. Somebody did not learn from their mistakes.

Guess we have to write-up a Perfect PCV Install description, to make the PCV work the way it should.

Long story short, the TPS signal is not clean when it get to the PCV - its actually digital ground that is messed up. It is way too jumpy when you monitor the voltage on a running bike. This will most likely depend on the bike and will be more or less pronounced on some bikes. Here is how you can check it: If you have the bike running at idle, open the PCV software with the PCV connected via USB and monitor the TPS voltage in the throttle position calibration screen. If it is not nearly rock solid, you got a problem.

The fix: disconnect (cut) the black/white wire that heads to central ground and wire it to the digital ground of the sensors (more details to follow). Once you have done that, the TPS voltage will be rock solid, and the TPS readout inside the PCV software will no longer jump around.

For the Autotune to work at part throttle, this will be crucial. A jumpy TPS signal with make the Autotune come up with bad mappings - sounds familiar?

Loaded or Not

We ride our bike on streets, highways, race/drag strips. Wherever and however you do it, you put a fair amount of load on the engine. To simulate this on a dyno companies like Dynojet have long used so-called Eddy Current Brakes. You dial in a load factor, or a progressive load curve (to simulate increased wind resistance for example) and you can test in more similar real world conditions. Still not perfect but a big step towards that.

Lets have a look at a custom mapped AF curve I did today for an 2009 VMax with UFO 4-1 pipe, Monster Big Air, Topspeed, EXUP eliminator and the all might PCV - not so much at first, but once it was wired up right, it actually worked very well.

Check out the first chart: {nomultithumb}

Looks like a decent AF curve, at least starting at 2,500 rpm, right down the reference line. This would be just a baseline to start tuning for peak power, but its a very solid start.

That 2,000 rpm thing. Surely looks lean, doesn't it? Rather than just richen it up, lets look a little bit under the cover of what is really going on. 

How long did that run take on the unloaded Dynojet 250?

Here is the same chart based on time:

Turns out that entire 5th gear run took about 7 secs. Pretty cool, jut not real life. If you where to put the bike in 5th, idling around at 1,200 - 1,500 rpm, how long do you think until you hit redline? Well its gonna be more than 20 secs in 5th. Of course this will be different in every gear.

Lets use the Eddy Current Brake to mimic that. You can do various complex brake models, for this test I am using a very simple 60% brake setting. Nothing progressive, just to give us an idea of what is happening:

What has happened? The extra load on the dyno has slowed down the acceleration dramatically. What happened in 7 seconds takes now about 18 seconds. Dial in more brake and it will get slower. To the point where you can completely stall acceleration if you have to at a certain rpm. For now the 60% brake will do.

What is immediately visible next to the longer duration of the run, is that the very same fuel map is starting to draw a different AF line. Some bumps, leaner across the board, simply different to what we just saw unloaded. To make things even more clear, lets switch back to the rpm based view and overlay both runs:

See it? Looks like two different maps all together, when in reality the map is identical, but the load on the engine has changed. At 2,000 rpms it no longer lean at all, its right where it needs to be. The AF curve settles very quickly after rolling into WOT. However, now we have some lean and rich spots and overall a map that is too lean. Right here you see the main reason why certified tuning centers must have an Eddy Current brake. Without it you are tuning for charts, not real world.

It gets even better.

Wrong TPS Signal

If all of that has been done correctly, there is yet another chance to mix things up. Yamaha did not make it too easy to pick the right wire, colors are hard to read and the PCV install does not help either. It uses a crimp on connector to pick up the TPS signal.

Took me a while to come up with this one, but now that I can reproduce it, it makes total sense. I am sure there are some bikes out there that have that problem and here is what happens:

Again same map, totally screwed up low and mid range. What could be a perfect map, looks like a butchered mapping. 

If your bike feels like it has a flat spot with a map that should match your setup, this could easily be the problem. Make sure you check for that. 

How can you tell? Go into the PCV software and check the TPS reading when you go to WOT at 2,000 rpm. If it says 100%, you are on the wrong TPS signal. The reading at 2,000 rpms should say 35ish%.

Accelerator Pump

One of the most misused features of the Power Commander family. While it can be helpful, it can also be really detrimental to good tuning. due to the YCCT varying the throttle between 1,500 and 5,500 rpm, a too sensitive accelerator pump will mess with your readings and power. Always start with the accelerator pump feature turned off, only enable it when you have a perfect map and a dyno handy to measure under load what is happening.

Well, it was a productive afternoon after all. If you are running a PCV with or without the Autotune and experience problems, surging, too much popping (assuming the AIS is already off) or simply end-up with a map that does not seem to perform at all, make sure you check for these common problems. They will kill your day, or worse make you dump the electronics or maps that could be helpful in so many ways.

Any one of these issues alone will totally mess with the Autotune and the AF curve.

As always: This information is provided without implied warranties. Make sure you know what you are doing and consult a professional technician if you are in doubt. This information is for off-road racing applications only!

Ride safe!