333pg333

Just in terms of staged injectors, I heard of a guy in a Race BMW with this setup and one of the inj failed on the track at high boost but he wasn't aware of it until the engine blew up. Is this a possibility, and/or could this happen with single inj anyway?

theedge

If his second injector failed then he would have had fuel for idle and not noticed idle quality go down, but ran way lean due to lack of fuel on boost. The single inj would have to fail partly open so theres some fuel, just not enough for a proper AFR.... Which I dont know if thats a very common failure mode.

blown 944

4 channel EGT with warning is good for this reason

Chris White

I am sure the engine preformance would have been 'off'. Any driver that keeps running their engine hard when it is not running 100% pretty much gets what they deserve.
In a staged system the second injector does not come on until the first is at 80% - so the engine would have run fine until the driver got to high boost and high rpm, then there would have been a noticable change, not a real big change but it should have been noticable. The only reason to continue at that point is big prize money for winning!
This is also a good reason to have individual egt monitiors - the cylinder with the faulty injector would have a much higher egt.

On a 'normal' single injector per cylinder system an injector failure is seriosly noticable.

fast951

With the prices of WB systems so low, I don't understand why anyone opt not to use one on a race car. If a injector fails (single or staged), the AFR will be off.. You wouldn't know which injectors failed (or for this matter if the fuel pressure regulator or the fuel pump) is failing, but you would know that something is wrong and hopefully you'll back off of it.

Now for those that do not pay attention to AFR while under load, there is a easy solution! Program the system to wake them up. Let's suppose you are WOT, under boost and your AFR goes leaner than 12.5:1 (or 12:1 or whatever you want), or your EGTs go up or the Intake temps (after turbo) go up. (Whatever the user wants to program as a fault condition). Then the system will throw a warning and will shut it down for you (limp mode). This system is will be coming to the Motronic Store near you

333pg333

Well this may have been some time ago so lets assume he didn't have sensors wired up to some form of limp mode, if he was running a low c/r, very high boost car, could it have literally taken a split second to detonate or would there been enough warning signs of his motor feeling "off" for him to slow down or stop and look at his gauges?

Chris White

I might be a bit harsh on your BMW buddy, its possible that the miss was not very noticeable – but I have had quite a few people show up here with completely trashed engines with the comment that it wasn’t running quite right at the track. One comes to mind where the oil pressure went to 0 as he neared the pit in – but he missed pit lane (during a club race) so he went for one more lap….at speed….with 0 oil pressure. Didn’t quite make it all the way around. Now he has a nice new engine.

So part of this is, hopefully, a clear message – if something seems wrong then check it out, hoping it will clear up is not a real good strategy!!

Kool

Thanks for taking time to talk to me last night Chris.

I will be in touch.

Now ot your point above it simply amazes me how some people are so oblivious as to how things work. I just don't get it. Especially a racer who presumably should know more about what is going on then the average Camry driver. But I suppose people like the above "one more lap" are what keeps the lights on.

John in your limp home how are you reducing engine performance? A simple rev limiter or is it more creative then that?

fast951

This applies to mere critical parts than the engine! Suspensions, handling... on the track you have to be in tune with your car. The same applies for the street, however on the track you have less time to zoom in and figure out you are about to be in deep trouble... Ok, back to scheduled programming!

fast951

Handling critical abnormal conditions is fairly complicated. A very harsh approach and the user will dislike it. A very linient approach and it will not work.

We identified various conditions to be of various severity and will be handled differently.

As a example, when running the V-FLEX software, if we detect a error with the MAP sensor we'll take action. A error can be in the form of a disconnected MAP sensor plug (no power) or a disconnected vacuum line or a pinched vacuum line, even a very slow responding MAP signal. When this error is detected, we initiate a soft-cut. Meaning we pull lots of timing out, you will notice a degradation in power so you can investigate (we hope). This soft-cut remains in effect as long as the DME is powered, will reset with power off, to be triggered again if needed. Basically, we consider the MAP sensor to be a critical input, if it fails we lower the performance. Having said that, not having a MAP sensor does not mean you are running high boost, we just can't detect the boost. Obviously, the soft-cut does not apply in some area of the powerband (idle, light load cruising) will not be affected, however under load/WOT it will trigger the soft-cut. Keep in mind, the MAP sensor fault detection takes place across the powerband.

Another soft-cut takes place if the DME sees boost over a certain value on pump gas..

There are other conditions that we consider as CRITICAL and require a total shut-down, HARD-CUT. The user is able to set these condition! With the PiggyBack, you are able to set overboost, Rev-Limit, Engine TEMP or Intake Temp limits to initiate the cut.

Now let's assume you set your overboost cut to 20psi (or your rev limit to be X rpm), once you exceed this level we trigger the DME to shut it down, we initiate a rev-limit type of a shut down. The engine cut remains in effect as long as the cut condition(s) are in effect.

The mechanism of initiating a rev-limit type cut is a bit complicated. The engine cut is based on your RPM and your LOAD (ex. rev limit is set to 3200rpm, the cut time/intensity must be softer than a cut at 6500 rpm). I can set the rev limit to 3500rpm (via the PiggyBack) and I can hold WOT and the RPM will stay at 3500...

There is an area in the powerband that we consider a limp-mode (low rpm, low load) that we allow the engine to run even if the above conditions are in place. Basically, you cannot set the rev-limit to be too low that you cannot drive the car. Also, at this RPM level it's not normal to be on boost.

When it comes to the Rev Limit, the user has the ability to set it anywhere between a Min and a Max, below or above which we take control.

As you can see, a normal shutdown or engine cut, becomes a fairly complex task. The soft cut is automatically initiated, the hard-cut is based on the user input. The user should always set the rev-limit and the overboost protection.

The hard-cut gets cleared as soon as the condition that triggered it is cleared! So if you hit your set rev-limit the cut takes place as long as you are exceeding the set limit.

We are working with a Wideband Vendor to be able to extend the user definable critical triggers or alarams not just to the overboost or rev limit but to additional important variables. You will be able to set this complex condition to initiate. As a example, you can set the a cut to be initiated under the following conditions: RPM higher than X rpm and/or BOOST higher than Y psi and/or EGT higher than Z deg and/OR throttle positin is greater than W angle.

Leave it to a engineer to take a simple idea and make a system out of it LOL.

Hope this explains the cut. Let me know if you have any questions.

Kool

Yeah that certainly explains it.

That is defenitely an engineers solution to what seems on the surface to be a simple solution.