The lack of a Knock Sensor in a GT

BlackICE said:

Does anyone know the reason for the omission of a Knock Sensor in the GT? I have read that knock sensor are difficult to get working right at high rpms. Is that the reason? I doubt it since many cars reving past 6500 still use knock sensors. Does this mean if you do a pulley swap and get a bad batch of gas you could hole a piston?

BlackICE

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It's the computer that is the real issue. Ford never got a good knock sensor setup until the 2005 Mustang which uses the new Spanish Oak processor.

For what it's worth, the 2003/2004 Cobra (factory supercharged if you didn't know) did not have knock sensors either. I've probably tuned 200+ 03/04 cobra's to 500-700 RWHP and never had one let go due to detonation.

Is there any aftermarket knock sensor that will work with the GT computer, isn't called eeck 5

Knock sensors, any good units out there?

BlackICE said:

Without a knock sensor the car is missing a safety net, even in stock trim. If any of the following happened:

1. the fuel was a lower octane than stated on the pump

2. plugged up fuel filter from dirty gas

3. fuel pump malfuction, lessen fuel flow and or pressure

4. fuel injectors plugged up

would increase the chance of detonation. I think that is one of the reasons that Ford has the fuel mixture set rich at WOT.

I would like to increase the boost, but add a safety net at the same time. Does any of the car tuners out there think this is a good idea, or am I just a worry wart?

BlackICE

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BlackICE,

Your points are well taken. My past experience with knock sensors was a while back, however, it's very difficult to reliably detect true engine detonation, under all conditions. I had tested and installed a couple different units many years ago and it's just a difficult thing to do! These systems were just never reliable. Even if a factory engine is equipped with one, the moment someone tries to change something on the engine, i.e. exhaust, ECU mapping, boost, RPM cutoff point, etc., the whole thing can "get confused and stupid" right away. During detonation, the acoustical/vibrational waves are sometimes complex and at very high RPM's it can be difficult to sort all of this data out. Even changing the percentage of antifreeze in your coolant could mess up the acoustical signature that the knock sensor "sees"!

There may be some good units out there, however, I feel that if our GT's had a factory knock sensor and it had provided the ECU with momentary "false negative" readings, you could really beat up your engine in a hurry! So, if anything mentioned above were true, then a knock sensor would have too much responsibility for safe engine management.

I think that knock sensors are fine for your regular daily driver luxury car in which the engine will never be modified.

In the case of the GT, if ever hear your engine "knocking" (detonating), you could have a bad batch of gas (did you let a friend barrow the car?) or your engine is overheating (look at the gauge)! In case of bad (low octane) gas, you just need to keep your foot "out-of-it" and drive more conservative until you get some better gas in it! Loud exhaust will prevent you from hearing detonation. Also, one last note, if you can hear an engine knocking (or "pinging") then the detonation level is usually severe...

Also, it seems as White Petunia has a "biological" knock sensor. Those are the most expensive type!

Jay
www.gtsaver.com

analogdesigner said:

BlackICE,

Also, it seems as White Petunia has a "biological" knock sensor. Those are the most expensive type!

Jay
www.gtsaver.com

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The most expensive type known mankind. Mine kept telling me to "knock it off" all day long.

Dave

Biosensor

BlackICE said:

I have a biological knock sensor too. When the unit is installed in the car I don't have any concerns about detonation, but sometimes it is removed from the car while I am driving.

It is interesting how the bio knock sensor's performance changes over time. At first it doesn't work too well and after marriage it works much better.

BlackICE

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As a single person, you guys crack me up! Jay

Jay is absolutely right about this. For an example, look at even high end fuel injection companies. They don't offer a knock sensor option even though most turbo/supercharged builders would buy them.

The latest thing is ion sensing. Actually looks at what is happening in the combustion chamber and fixes the spark for best operation. It senses the combustion as it begins. Quite expensive now, but some car companies are starting to use this technology and prices will eventially come down. When this happens, the better aftermarket FI companies (I know Autronic is on top of this) will offer it. Then the spark advance will automatically tune itself!

Knock Sensor???? Mine is a Governor. She screams slow down anytime the boost goes above zero. I have never won a race with her in the car.

Ion sensing!

Bart Carter said:

Jay is absolutely right about this. For an example, look at even high end fuel injection companies. They don't offer a knock sensor option even though most turbo/supercharged builders would buy them.

The latest thing is ion sensing. Actually looks at what is happening in the combustion chamber and fixes the spark for best operation. It senses the combustion as it begins. Quite expensive now, but some car companies are starting to use this technology and prices will eventially come down. When this happens, the better aftermarket FI companies (I know Autronic is on top of this) will offer it. Then the spark advance will automatically tune itself!

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Bart,

This is very interesting! I would like to do some reading on this as I am very curious. Thanks, Jay

Here is some more reading:

Ion 1

Ion 2

The new BMW M5 and M6 V10 engines use Ion sensing combustion control also.

Ion knock sensing info, thanks!

Guys,

Nice finds! Now I have something to read between projects!

Jay
www.gtsaver.com

Sorry to dredge up an old thread, but since I recently installed my Whipple and had it tuned by PSI Motorsports, I came across a bit more info.

According to Patrick at PSI, the sound/vibration of the blower itself created false knock, thereby rendering the sensors powerless. Seems reasonable...I know that installing bigger cams in a couple of my Vettes has resulted in similar issues.

PSI has a dozen or more very fast Lightnings and Cobras in the shop at any given time, and apparently the Lightnings (Ford's first blown mod motor) actually have knock sensors installed in the block, but they were never activated in the computers code.

I find that last tidbit very interesting...in an era of cost cutting, installing inactive knock sensors seems a bit wasteful, but I suppose the design/production may have been in place when the programmers decided the false knock issue couldn't be overcome.

Like BlackICE, I was surprised at the lack of knock sensing in our not-so-inexpensive motors, but like all of you other Whipple owners, I'm just going to keep the tune conservative and keep an ear open for any tell tale signs of detonation.

BlackICE said:

Does anyone know the reason for the omission of a Knock Sensor in the GT? I have read that knock sensor are difficult to get working right at high rpms. Is that the reason? I doubt it since many cars reving past 6500 still use knock sensors. Does this mean if you do a pulley swap and get a bad batch of gas you could hole a piston?

BlackICE

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Its ROUSH. Instead of spending the time to get the knock system to work properly, and the PCM was more than capable of it, they make the motors ultra safe with low octane gas. Even the new PCM in the Shelby GT500 could use them, but they don't. Instead, they are setup so they will not detonate, even under hot temps, with 87 octane. Thats why everybody can put pulleys and spark in them and get another 50-75hp with no sweat. They call out 91 octane, are just above edge of detonation with 87. Roush did the powertrain development on these vehicles.

A knock sensor, if with some false readings, is better than no knock sensor at all. There are many degrees of detonation, and you can have the sensitivity set low enough that you can only pick up the highest level of detonation, which destroys engines. Faint knock will typically not hurt something, it's prolonged detonation (multiple seconds). When you just hear a "ping ping" and it goes away, this will not hurt your engine. "ping ping ping ping ping...." will

Thanks,
Dustin

The knock sensor bosses are on my engine and I am installing knock sensors.