SOHO Motorsports Z/G Tech Article 1
Nissan Z/G VDC & Yaw Sensor vs ECU Tuning:

Written by Nik Sohoritis

Since biding our SOHO Motorsports Unlimited Time Attack Infiniti G35 we have received a lot of questions from customer, fans and even shops about how we got from a completely stock 2005 G35 to the Time Attack Beast we have today, that is quite possibly one of if not the fastest G35 around any track. (In case your not familiar check out the Project thread here: https://g35driver.com/forums/g35-cou...torsports.html, or click the site links at the bottom of this post). During the build process we realized many things about this platform that very people may be aware of and things that none of us have ever seen on any forums, and we know because when we hit a speed bump and ran out of options we would check the forums for an answer and never could. Throughout the next few months we will be releasing a series of tech articles about some of the not so obvious issues and technical dilemmas these awesome vehicles can face when seriously modified.

Throughout the next few weeks we will be posting articles that describe some of the issues that we ran into while tuning the stock ECU with removing these items and the sensors that we think are not playing a factor into tuning, that really are. When we began the process of building the G for track duty at the highest level we approached the entire process with a nearly scientific approach. Coming from a Nascar engineering background our tuner and owner Nik Sohoritis has done a ton of research and development putting his education and experience to use in his infamous notebooks and calculations to the many hours of dyno time and amazing results to back it all up. But as we all know calculations and dyno results don’t mean anything unless its put to the test on the track, and thats where our driver Kevin comes into the picture. He has pushed to the limit every single thing the G/Z platform has to offer on track from stock to complete race car. And to this day we continue to use what we learn on and off track to produce not only a faster race car on track, but also better performance for all of our customers. With all of this knowledge we figure it does us no good to keep it to ourselves so we want to share everything we have learned on the forums so everyone else can benefit and hopefully answer a few questions people may have. At the end of the day we love the Z/G and Race community and we want to give back in every way we can.



The primary issue that I would like to start with for our Tech Article series is how the VDC function, whether switched on our off, effects the tuning process on dyno's unless the yaw sensor is removed. The VDC function that comes on the majority of the Z/Gs is meant to help the driver keep control in adverse conditions, but when tuning a modified vehicles there were some issues that we came across while tuning the stock ECU using UpREV. Many of times while tuning the vehicle on the dyno, the tuner will disengage the VDC to prevent the vehicle from going into a “limp mode” before he begins a pull. If the “VDC off” is not illuminated on the dash and the tuner begins his pull, the vehicle will go to about 2500 rpms and will not rev any higher, no matter how far down the accelerator pedal is pushed. Typically if the VDC is turned off, the vehicle will have disengaged the traction control and there should not be any type of limitation on the vehicle, or at least thats what you are led to believe. But in fact this is wrong. Even with the VDC turned off on the vehicle, the vehicle is still using the anti-slip function to ensure that the driver still does not have full control of the vehicle if an incident were to occur, and the ECU would assist the driver in case he were to lose control.



Many times a tuner will see the SLIP light illuminate for a split second while tuning the vehicle and not feel any difference in power and usually not think anything of it. The way that the anti-slip function works is that it will use the ABS system to pulsate brake pressure onto the rear wheel that is rotating faster than the other and bring both rear wheels to the same speed. When this does occur, it sends a signal to the ECU to let it know that the vehicle is starting to lose control and will need assistant to help bring the vehicle back into control. The signal that is sent to the ECU will cause the ECU to retard ignition timing to reduce power output from the motor to aid in regaining control of the vehicle. Not only does the ABS system work together with the ECU in scenarios where the vehicle is starting to lose control, there is also a Yaw sensor that assists as well.



Inside the cabin of the vehicle underneath of the center console and armrest, lies the Yaw sensor. Now you may be asking yourself what is a Yaw sensor and what is its purpose. The Yaw sensor is the brain behind the anti-slip controller, thus when slip is noticed, the ECU will send a signal to the Yaw sensor and the Yaw sensor will work together with the ECU & ABS system to regain traction. A Yaw sensor is used in many forms in the automotive industry whether from Formula 1 to the Street Production road race cars, it is a three axis sensor that determines the angle difference in a vehicle’s heading direction and actual direction, which is better know as slip angle. For example, say that you are in a vehicle heading around a turn at 30 mph and the faster you travel around the turn, the harder it gets to maintain traction, it almost feels like no matter how hard you turn the wheel the vehicle wants to lose control. The angle difference between the direction that the wheels are facing in respect to the direction that the vehicle is facing is known as the slip angle.



With that explained now back to how that applies to our vehicles. When the vehicle is on the dyno and it senses a loose of traction in the wheels, it is re-enacting the example above, but in a much more milder scenario because the ECU does not know whether it is on the street or on the dyno, so the anti-slip will come into play. After doing a little research, we decided to remove the Yaw sensor while at the dyno to determine what the ECU was actually doing when it did not receive any input from the Yaw sensor. We did a couple of pulls and monitored several parameters with the Yaw sensor installed and working properly and then we would let the vehicle cool down to the starting temperature of the previous pulls and did a couple of pulls with the Yaw sensor not installed. We eliminated all of the other variables possible and after comparing the Yaw sensor installed logs and no Yaw sensor logs, we were surprised as to what the ECU was actually doing.

http://youtu.be/G3Y3Z-4Gk_U?hd=1

On the same exact tune, the ECU was removing 3 degrees of timing from 3000 rpm to 6500 rpm on WOT when the Yaw sensor was installed in the vehicle while on the dyno. We were able to recreate this numerous times to ensure that it was not just a coincidence that had occurred and found that the ECU was indeed retarding timing with the Yaw sensor installed and the VDC turned off. Three degrees of timing may not seem like a lot but when it comes down to any form of motorsports whether it is time attack, autox or drifting, you will need all the power that you can get.

We have currently removed the Yaw sensor from our drift and time attack vehicle and have noticed a difference in the way that the vehicle performs, especially in our drift car. With the Yaw sensor removed, the ABS and SLIP light will stay illuminated on the dash, not to worry though the ABS still will work properly and retain its normal features, stay tuned to the next article as we will talk about coolant temperature and how important it is to keep it down to increase horsepower while tuning with a stock ECU and specifically on forced induction setups.

http://youtu.be/MN2DsWdBmvs?hd=1
http://youtu.be/WUL0a-ghPUo?hd=1

 

That is very interesting what the ECU does in relation to the Yaw Sensor.


There is a mod we do here https://g35driver.com/forums/drivetr...-vdc-real.html which puts a switch to the Yaw Sensors Power. Basically it removes the Yaw Sensor all together and you get the same lights.

Cant wait to see what else you guys will write about.

 

Interesting - you found what has been found by many of us but you simply removed the YAW.

Many ppl did the mod thescreensavers posted above ^^^

We all hate the VDC/Yaw being intrusive



I'm looking forward to see what your results were as far as engine coolant. I already know how big of a difference it is for me as I can see huge power drains when its 110* outside and my coolant is around 215-220*. Feels like a different vehicle when its hot vs cool.

 

Wow very good read there! Im curious how much the VDC even in the off position on the street retards the timing if your seeing similar results on the dyno if so i think i may make a kill switch for it like the link above and just use osiris to turn the codes its going to throw off.