Knock Fail-Safe Device

[jskarateka]

I posted this a long time ago but thought I’d bring it up again.

So we have knock sensors, knock gauges, knock alarms, Scanmasters, Powerloggers, narrow bands, widebands, boost gauges, and every one of them relies on the driver to react and lift. I know I’m not alone at being one failed fuel pump/fuel injector/alky pump at WOT away from breaking my $8K longblock.

What about a device that would automatically open the wastegate, or at least attempt to, when knock occurs? Instead of sounding a smoke alarm could it trigger a relay, that opens a small air valve plumbed in-line with a second vac/boost line teed into the wastegate? Knock is sensed, relay opens air valve, full boost pressure bypasses existing boost controller line and opens the wastegate.

What do you think, am I crazy? Would it work? If it did I know I would buy one. If someone makes a ton of money on this please remember me.

 

[DeltaBravo]

I like where your going with this.

But to be clear about "knock control" devises in the TR...they all ready have one. It's the sensor and ECU. ECU will pull timing out when knock is detected via the knock detector. That is the "knock control" devise that should prevent the driver from needing to lift.

However...I understand what your getting at. In a perfect world, that is exactly what happens...after a hard pull, you notice 1-2 degrees of retard on the scan master. No biggy...system is working. Adjust the tune accordingly and push on. But as you mentioned, when something significant fails (because when don't live in a perfect world), no amount of timing retard will save you.

Someone out there must have a simple solution...

 

[Sinister CO]

The safe injection system from snow performance triggers a solenoid to kill boost when low flow is detected by their sensor. Perhaps the same could be done based off the knock sensor somehow.

Sent from my SPH-L720 using Tapatalk

 

[RmvBfrFlght]

The Dynamic EFI EBL SFI-6 Flash ECM has this built in. There are user tune-able parameters for the level of knock that once is exceeded the ECM pulls boost via the waste gate. The amount of boost reduction is also user tune-able.

That ECM can also ignore knock on 2-3 and 3-4 up shifts & 3-2, 4-3 down shifts for a user set period of time. This is handy as tire spin and hard shifting transmissions can easily cause false knock. Ignoring it maintains the power.

RemoveBeforeFlight

 

[b4black]

During a catastrophic failure of a fuel pump, or alcohol injection pump whatever, damage can happen quickly. Getting a wastegate solenoid and then the wastegate to open and drop boost might not be fast enough.

Maybe disabling ignition or fuel injectors electronically will be better. That's how traction control on many cars works. Shut off fuel or spark completely.

 

[jskarateka]

During a catastrophic failure of a fuel pump, or alcohol injection pump whatever, damage can happen quickly. Getting a wastegate solenoid and then the wastegate to open and drop boost might not be fast enough.

Maybe disabling ignition or fuel injectors electronically will be better. That's how traction control on many cars works. Shut off fuel or spark completely.

I was thinking that too, but figured it might be too drastic to cut the engine completely during WOT.

 

[gusszgs]

So the way our stock ECM's work now is say your in 3rd gear at WOT and you get say 5*KR........the ECM pulls 5 degrees of timing. So, if you were running a TT alky chip with 23/21 * timing in default, then that 3rd gear timing would be reduced to 16* correct??

 

[turbo89]

During a catastrophic failure of a fuel pump, or alcohol injection pump whatever, damage can happen quickly. Getting a wastegate solenoid and then the wastegate to open and drop boost might not be fast enough.

Maybe disabling ignition or fuel injectors electronically will be better. That's how traction control on many cars works. Shut off fuel or spark completely.

This X 2

The higher you have the wick turned up .. the quicker the damage happens

When your running @ 28 PSI and zero knock .. then suddenly have a hardware failure or lag .. no way in the world can you back the boost off fast enough VIA wastegate .
But you can DUMP boost via dump valve .

There are knock retard strategy already in place on the stock ECU ... pulls timing .. pulls more timing.. pulls even more timing until it has exhausted the entire ignition retard strategy.. then starts to pull boost until that is exhausted as well.. Aftermarket ECU have even more strategy ability.
If you haven't lifted by then typically its game over and new headgasket time .... the window of opportunity to lift and save things is greatly shortened by just how much power your making. You can knock a stock motor for a bit @ stock boost before things go south .,,. up the boost and power far enough that window can be almost non existent.
Guys use MLS head gaskets and seal up things tight as a drum .. then things knock .. guess what that pressure will go somewhere .. usually out the bottom end. Headgasket is your friend as its a fuse.

Depending on why things are headed south .. pulling ignition may not help ... on most OEM applications FUEL is completely pulled .
the best setup would be to dump boost , cut ignition , cut fuel

 

[RmvBfrFlght]

The biggest issue with cutting spark is that it fills the exhaust system with air & fuel. You may save the engine but when the spark comes back the exhaust system will exit the area.

A full engine cut (via fuel or spark) while under load is abrupt. Nearly violent, but it is better then running over the crankshaft.

RemoveBeforeFlight

 

[turbo89]

The biggest issue with cutting spark is that it fills the exhaust system with air & fuel. You may save the engine but when the spark comes back the exhaust system will exit the area.

A full engine cut (via fuel or spark) while under load is abrupt. Nearly violent, but it is better then running over the crankshaft.

RemoveBeforeFlight

Absolutely .. shutting down fuel and spark @ WOT isn't ideal ... but i have yet to see any damage occur from this.. the rotating assembly has intertia and doesnt stop cold turkey.. and with the 8:1 compression these motors have its somewhat of a cushioned slow down.

Driving over the crank or windowing a block .., not so much

If you've ever hurt a motor on a run that let fluid out ( oil or antifreeze) .. its like being on ice .. @ 120 it can mean having a car to put another motor in or having a totaled car

 

[liquidh8]

The Dynamic EFI EBL SFI-6 Flash ECM has this built in. There are user tune-able parameters for the level of knock that once is exceeded the ECM pulls boost via the waste gate. The amount of boost reduction is also user tune-able.

That ECM can also ignore knock on 2-3 and 3-4 up shifts & 3-2, 4-3 down shifts for a user set period of time. This is handy as tire spin and hard shifting transmissions can easily cause false knock. Ignoring it maintains the power.

RemoveBeforeFlight

I have to get back in the bin for this, I overlooked these tables. I may have some questions in a few days when I get back this weekend.

 

[bison]

The problem is that knock doesn't do much at low power densities. At high power densities its like a bomb going off in the cylinder even if it's very slight. The fail safes I use are:

1. Use adequate octane or anti detonant

2 Speed density ecu with a properly setup timing and a/f target table
3 afuel system that can support nearly 50% more air flow than you plan on running.
4 wide band correction.
5. Fuel pressure correction
6 Knowledge of what the engine can take mechanically

You can still easily damage an engine with zero knock retard when power densities are high.

If you wanted to use a wastegate as you mentioned it would need to be an external with a lot of flow potential and you'd need some type of device to determine when to open it and somehow plumb it



Sent from my iPhone using Tapatalk

 

[TurboBuRick]

A plethora of information abundance.