Performance Chips & Knock Sensors

[Embs]

NO CHIP WARS please......


Can a aftermarket and/or performance chip disregard the input from knock sensors and still allow the motor to run?


I recently test drove a turbo body with Vram engine transplant.
The exhaust was really quiet and I could hear the car knocking under load from 4.5K up to 6K. I was driving next to a concrete wall. I couldn't believe the timing wasn't retarted by the DME to compensate. If the exhaust would have been any louder, you would not have been able to hear the knocking at all.


The owner of the car denied being able to hear anything, I know what I heard.


The car had a Cyntex chip.

Todd

[tsuter]

Maybe the car had no knock sensors at all so the ECM had no inputs. Might or might not give a CEL for that.
Microphone type knock sensors aren't worth much anyway. They can detect and cause retard on sounds other than knock and miss on real knock.
Current high tech EFI engine management (Delphi etc.) uses ion sensing across the plug gap to detect knock in the cavity itself. In other words the spark plug and wire acts as the knock sensor itself. It is highly reliable and cannot be disabled other than by running wires with the incorrect resistance.

[Embs]

It had the sensors, I saw the leads coming out of the shroud. There was no CEL (as in most 3.6 transplants).


I don't know how effective the Porsche 993 knock sensors are??
I just know that knocking / pinging is NOT a good thing with these engines.

[Lorenfb]

The inputs from the knock sensors can ALWAYS be disabled. They can be ignored
just like any other DME input. It's all a result of how the firmware (EPROM data)
is modified. Typically ignoring the knock sensors is how the performance chips
can advance the timing without the DME overriding the new advance curve of the
chip. Advancing the timing is really what provides the potential for a performance
increase.

[Embs]

Originally posted by Lorenfb
The inputs from the knock sensors can ALWAYS be disabled. They can be ignored
just like any other DME input. It's all a result of how the firmware (EPROM data)
is modified.

I was hoping that you would chime in here. I suspected this was the case. Isn't disregarding the knock sensor inputs a potentially dangerous situation, especially for a 993 engine?


One problem is that many of the exhaust systems (especially on the 3.6 transplants) are so loud that you can't hear the knocking / pinging.


It was an 84 degree day when I test drove the turbo bodied varioram car. It was pinging like wild on 93 octane. The owner denied being able to hear it...

Todd

[tsuter]

I can't believe any reputable chip designer would intentionally ignore/disable the inputs from the knock sensors.

I guess you could ask Cyntex.

Those inputs are very simple, you get a knock read you drop one to three degrees from the advance map, you get it again you drop again until it goes away.


edit:

the problem with the microphone type is the ECM may get bad reads on other noises or no reads on knock when it should.
That's why new technology in ion sensing is vastly superior as you are detecting in the cavity itself with the plug gap resistance and you can then even adjust advance by cylinder.

[tsuter]

For you software weenies, here is a screen shot from my Delphi Automotive software for my 1.8 liter EFI ECM.

Notice I have marked the "disable knock sensors".

As I said before however, no "reputable" software designer would do this and give the EPROM to a customer. But some software does allow the disabling of knock control as a tuning tool.

I know why but I'm not telling.

[Lorenfb]

"I was hoping that you would chime in here. I suspected this was the case. Isn't disregarding the knock sensor inputs a potentially dangerous situation, especially for a 993 engine?

One problem is that many of the exhaust systems (especially on the 3.6 transplants) are so loud that you can't hear the knocking / pinging.

It was an 84 degree day when I test drove the turbo bodied varioram car. It was pinging like wild on 93 octane. The owner denied being able to hear it...

Todd"

You're right on Todd. I couldn't have expressed it better! It's the combination
of heat, the extra timing advance, and the lack of the knock sensors. That motor
will probably need rings and pistons before long.

"I can't believe any reputable chip designer would intentionally ignore/disable the inputs from the knock sensors. "

Please! Get real. Those guys do a lot of things, many of which they are
unaware of that cause other problems.

[tsuter]

Originally posted by Lorenfb
"I can't believe any reputable chip designer would intentionally ignore/disable the inputs from the knock sensors. "

Please! Get real. Those guys do a lot of things, many of which they are unaware of that cause other problems.

You talkin bout me man??? Those is fitin words!!

[Lorenfb]

"As I said before however, no "reputable" software designer would do this and give the EPROM to a customer. "

People do all kinds of things to sell products. What planet do you come from?

[tsuter]

Look two screens up Loren. If I disabled the knock control in the program and sent you a new calibration or eprom to load and you blew up your motor with detonation, I don't think I'd do much work again.

But as I said the key word is "reputable".

Gotta go work on a guys program now. A Calli guy!!!

[ChrisBennet]

Iread someplace that Saab is or has stopped using their Trionic (p?) knock detection. Too bad, it was a neat system.
-Chris

[Embs]

Loren,

Can you start the engine and disconnect either or both of the knock sensors and notice any change?

How could you detect that they are/are not being utilized by the DME?

As always, thanks for your input.


Todd

[Wil Ferch]

I don't want to start another Loren / Steve wong exchange, but...
1.) certainly anyone who does chips may do so unscrupulously and ignore the knock function.
2.) SteveW is rather unique in that he can /does design a form of "poor-man's " knock sensor for the 3.2's ( which never came with knock control), by designing a basic ignition advance / fuel profile, then captures intake air temp readings and uses that to retard advance in a sort-of open loop fashion for hot running conditions. Seeing that he's not overly aggressive with advance timing in the first place shows this to his credit for conservatism.
---Wil

[Embs]

Originally posted by Wil Ferch
I don't want to start another Loren / Steve wong exchange, but...

Yes, I don't want to either Wil. I am looking at this from the 993 varioram engine perspective. This engine came with and needs the knock sensors to properly and safely run.

On the Vram, the hall effect sensor basically reports the ignition advance to the DME and depending on knock sensor input retards or advances the timing to optimum. What happens with the Cyntex chip is the timing is advanced without regard to the engines knock conditions.

Todd Embs

[tsuter]

That is a question for Cyntex.

If they are "piggybacking" on the stored DME ignition map then they could be adding advance when the knock sensor is saying to retard. (editorial: piggybacking is bad design by the way).

If they have replaced or in fact updated the stock DME ignition map then the knock sensors can serve their intended purpose and retard on the replaced or updated ignition map.

[Lorenfb]

"2.) SteveW is rather unique in that he can /does design a form of "poor-man's " knock sensor for the 3.2's ( which never came with knock control), by designing a basic ignition advance / fuel profile, then captures intake air temp readings and uses that to retard advance in a sort-of open loop fashion for hot running conditions. Seeing that he's not overly aggressive with advance timing in the first place shows this to his credit for conservatism."

Someone swallowed it "hook, line & sinker". Never heard so much B.S. It just
keeps on coming! It's laughable. The naive just suck it up!

To check out the knock sensors on the 993, you really need the Porsche
Hammer or ST2 tester.

[tsuter]

Tooo funny Loren! I couldn't understand that either!!!! An ignition map using RPM and IAT as the X and Y axis? If you got intake temp why not put in a MAP sensor and do it right? Oh well. Too much for tired minds me thinks!

[Steve W]

Originally posted by tsuter
Tooo funny Loren! I couldn't understand that either!!!! An ignition map using RPM and IAT as the X and Y axis? If you got intake temp why not put in a MAP sensor and do it right? Oh well. Too much for tired minds me thinks!

Ignition maps use RPM and the artifical load signal of the AFM to lookup the base ignition value. There is no reason that these base values cannot be trimmed by other factors such as the engine temperature, intake air temp, rate of rpm change, and in this thread, knock sensors. Think about it.

Perhaps some of you should stick to what you do instead of making statements about which you do not know.

[ChrisBennet]

Originally posted by Lorenfb
The inputs from the knock sensors can ALWAYS be disabled. They can be ignored
just like any other DME input. It's all a result of how the firmware (EPROM data)
is modified. Typically ignoring the knock sensors is how the performance chips
can advance the timing without the DME overriding the new advance curve of the
chip. Advancing the timing is really what provides the potential for a performance
increase.

Could you give some specific examples of chips that do that i.e ignore the knock sensor? Do you know of any that don't?
-Chris