fast951

Sid, no problem here. Just trying to understand what you were describing.

There are many ways for fault detection and recovery. Actually it is one of the hardest thing to do, as there are so many variables and conditions in place. We opted to handle our fail-safe the way we did (even though it was very time consuming to design, implement and test) for many reasons.

Having many customers using their cars on the track and under race conditions, we wanted the least intrusive mechanism in place. Things always happen at the wrong time, killing the engine (fuel or ignition cut) at the apex of a turn is very dangerous, and could send a racer into the wall. Not to mention a racer on his last lap, hitting a performance wall (limit boost or engine cut) and losing the race because of a fail-safe method. It will be outrageous!
On the street, it's not any better, imagine merging into traffic and you hit a ignition or fuel cut.
Not something I want to experience myself on the street or the track! Which is why we opted for a non-intrusive mechanism, yet still be able to warn the user. Even the RPMs at which we alarm the driver were designed to be the least intrusive. Again, the abrupt cut of power at the Apex (or merging traffic) is not something I want.

blown 944

Again, it would be wiser for Josh to explain exactly what he has done. From my experience it was not violent but just limiting. I have only experienced it at low load so that is my reference. Knowing Josh, he probably has other perameters set to deal with failures.

Eric_k

I can tell you the vflex boost sensing is a nice feature. At my last race the diaphragm inside the wastegate tore, sticking the wastegate shut. Instead of running the boost way up and possibly blowing the engine, it hit the overboost protection. I'm sure it prevented me from doing some serious damage!

fast951

Again, I'm not asking how things are implemented. Since, you made a point of telling us that your system also has a fault handling by limiting boost to 3psi (or 5psi). I was just trying to understand what you were describing from a driver point of view. If you don't care to share, that's fine..

The goal of this thread is to make V-FLEX and V-MAF+ users aware of how we handle the MAP fault so they can identify the fail-safe condition.

blown 944

Hmm, it must be the Internet and my limited comprehension. Honestly, I wasn't trying to cause any riffs in any way by chiming in. I am truly glad that there are failsafes built in to either of these items. I was just making reference since it just happenned to me.

From a driving standpoint I was happy that I was immediately notified (via limp mode) as I'm sure any user would be.

I didn't mean to detour your thread. I hope that either way any information provided is helpful.

Obviously you are working hard to provide a solid product (as you have been doing) and I deeply respect that....

fast951

Hi Eric, glad it worked for you. What you experienced is the main reason in 2007 I decided to introduce boost to the DME. When the WG gets stuck or the pressure line burns up (or comes lose), boost builds up so fast it's almost impossible to catch in time.. Safety is very important, as they say "you can't win the race if you don't finish".


With the V-FLEX software you have (and with the latest V=MAF+), the user is able to set overboost and rev-limit values to meet his/her liking. In addition, the user is able to set complex alarms which will save the day (ex. If boost over 5psi and AFRs leaner than 12:1.. The actual values are user selectable)..

If the user does not set the desired limits, the DME has code to identify what is considers "unsafe conditions" and to attempt to save the day. As an example, by default, you get a max RPM that you cannot exceed. so you don't over-rev the engine if you forget to set the rev-limit.

fast951

I didn't think you are trying to detour the thread. No problem with you making it known that your system has fail-safe.
I'm always interested in knowing how different people handle or solve a problem. Hope I was clear with my description of our solution to a very serious potential problem!

Rogue_Ant

John, I completely agree that using a MAP sensor to modify/dictate ignition timing without fault protection is ludicrous. I do like your new "user notification" method, however I disagree with still allowing full boost during a MAP sensor fault - but this thread is not the proper place for that discussion.

Sid's software tends to change fairly often, as he is one of my pre-release testers...

That said, his softwares MAP sensor fault detection/protection is based on the same protection built-in to all of my Tunes:

The DME continually checks the MAP sensor for proper operation, and will default to a "fail-safe" fuel/timing tune, or a short (~1sec) fuel cut depending on the situation. The boost limiting feature that Sid mentioned is accomplished by fuel cut, typically around 3-5psi of boost. This feature determines an approximate boost pressure by an airflow/RPM calculation, and allows us to trigger the fault in the event of MAP sensor "soft failure" (where the MAP sensor is still sending the DME a signal, however the signal is incorrect or not realistic).

Mighty Shilling

Shouldn't you be enjoying a margarita right now?

fast951

Thanks for clarifying. So it appears that what Sid described (fuel cut) is what is taking place. Not a approach I would take due to the risks involved, as I described earlier. A fuel cut at the apex of a hi speed turn will unsettle the car, it is not something I (or any racer I know) can live with.

As far as the fuel cut to limit a 3-5psi based on air flow. Well, I'm not sure it's accurate as various engines flow differently off boost (3L, head work,...).

Regardless, it's your system, and you solve it the way you want.
I agree this this thread is not the place for that a discussion.