Pondering detonation and such:

The most common cause of detonation seems to be engines going lean for (whatever reason), and it would make sense that on a properly tuned engine with good injectors, the major cause would be fuel pressure - either from higher than normal flows due to cold air, or higher boost, or a failing fuel pump/electrical system.

However, if there's no spark, there's no detonation.

So, if there were a sensor that could monitor fuel rail pressure, and if it dropped below what it was supposed to be at, cut spark, this might help save some engines.

Same thing with the O2 sensor voltage - even with a narrowband, it should be pegged rich under boost. So, if it starts to go lean above 3psi or something, cut spark. This may or may not save the engine, because the O2 only shows things after the fact, but if there was a gradual leaning, it may be able to catch things fast enough.

Is this something worth investigating, or is it just a solution looking for a problem?

-=Russ=-

 

I had a similar idea but a little different. I have a Nordskog Digital Fuel pressure gauge and it has an aux output. This gauge will send a signal to the aux output depending on where you set the psi warning too to control a secondary device. Basically it provides a ground for whatever you hook it up to. I was going to hook it to a solenoid and use it as a electrical blow off valve. The solenoid valve I have is the one I have used for a past water injection project. This solenoid valve is going to be tapped into the IC piping just like a BOV. I was going to set my warning level at 39psi so if my fuel pressure gets below this level, the solenoid would open venting any boost. No boost no detonation. Only problem with my idea is if your base fuel pressure is 40psi and your boosting 15psi your fuel pressure would be 55psi. If you have drastic fuel pressure loose at this boost level, I don't think the engine would survive anyways due to the loose in fuel pressure until it reached the 39psi warning point to open the valve. Anyways I haven't experimented yet so who knows if it would work or not.

 

What happens when the sensors fail?


-Ted

 

Same thing you have without the cut - a blown engine.

This isn't a setup that should ever actuate, but it's another layer between a failure somewhere and a blown engine.

I like the idea of hitting the blowoff valve as well. Are they normally able to be actuated electronically?

The solution to the rising fuel pressure is to have a differential pressure sensor (or just put the pressure sensor in a box pressurized by the boost, should be the same difference). The fuel pressure should always be X PSI above the manifold pressure, so if you can use a differential sensor or make your own, this will track properly with changes.

-=Russ=-

 

A'PEXi (or Defi`) can do differential pressure readout on it's gauges.
I got to see this system on hIGGI's FC...kinda neat.


-Ted

 

Was this part in reference to my idea? If so I'm having a hard time visualizing it's operation.

 

Yes. You were talking about your gauge having a 39psi warning, and that not being terribly useful under 15psi (with 55psi fuel pressure).

I'm saying, you don't *care* what the absolute pressure is, you care what the differential pressure is. If the fuel pressure in the rail is less than 40PSI over the manifold pressure under boost, cut the ignition. I was just discussing simple ways of making a cheap pressure sensor into a differential pressure sensor by toying with it's reference pressure (if it's designed that way).

-=Russ=-

 

Ok I see. Your explanation was still referring to ignition cut due to the pressure differential while mine was referring to venting boost through the electric solenoid. I can change the psi warning level on my gauge.

 

Yea. I don't think the blowoff valve is the best way to approach this - this is an emergency failure system, and the idea is to absolutely, without question, cut the ignition if something starts going wrong. The blowoff valve will take time to react, and the ignition cut is more or less instant.

-=Russ=-

 

Well actaully the solenoid valve I would use is instant in it's operation. As I said earlier I used it on my water injection. As soon as the voltage is applied, boom it's fully open. Besides if the ignition is fully cut, doesn't that make the car un-drivable? If the electric BOV/solenoid stays open, the car is basically NA because the turbo can no longer build boost.

 

Or the compressor starts sprinning freely, adding wear and tear on your turbo... Face it, when **** goes wrong it goes way wrong, and you're due for a rebuild.... all you can do is everything in your power to make sure it happens later, rather than sooner....

 

First off, I don't care what you say. It's not instant. No physical device on the macro scale is instant. Very, very fast, sure.

Second, the goal is to eliminate the chance of detonation as soon as possible after detecting a problem. The O2 sensor is *probably* going to be too late, but fuel pressure could be an early warning. Blowing off the boost will take several combustion cycles to lower the pressure appreciably. Cutting ignition is effective as soon as it's enabled.

Third, a full ignition cut *would* make the car undrivable, if it were sustained. I would most likely have a manual reset on the device (possibly inside the car). If it cut ignition, it would keep ignition cut until you manually reset it, requiring you to be aware of the problem. If you know there's a problem, you can keep the engine out of max boost (or, really, boost at all) until you get somewhere to fix it.

Again, this is not anything that should EVER actuate under normal driving, but if it did ever trigger, it could be the difference between finding a wiring problem/failing fuel pump/etc before it totally failed, and rebuilding an engine for unknown reasons.

-=Russ=-

 

That would only happen if you continued to beat on the car while it was having problems. I quick drop in boost pressure would tell you that something is wrong.

 

Damn dude I thought you and I were having a discussion on the same thing. We are both trying to accomplish the same goal here. What's your problem? (you don't care what I have to say?) Why in the hell did you start this thread. Either way should work fine.

 

No, I'm just pointing out that NO physical device is instant. Sorry, nitpicking. Nothing against your idea or you personally.

Back to your regularly scheduled discussion.

-=Russ=-

 

You may need to start another thread in the performance section to get more views, ideas, and opinions? We really need a device like this.