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01-06-2020, 09:35 AM #1
Knock Sensors for 03-04 Cobra and MS3Pro PnP
I know this was discussed in the MS3 megathreads but wanted to give it it's own thread. For those with the MS3 that want to add Knock Sensors what is the best route to go. Location was discussed here https://www.modularfords.com/threads...ensor-Location and was decided that the bolt hole below the engine mount is best to use a step stud.
What is the best sensor to go with?
Any idea the best way to set it up in tunerstudio?
Any other info to add?
01-06-2020, 10:38 AM #2
01-06-2020, 10:54 AM #3
Are you using one knock sensor location on just one side of the block?
Or 2 knock sensor locations, one on each side of the block?
01-06-2020, 11:30 AM #4
01-06-2020, 12:40 PM #5
What fuel? You don't need knock sensors with e85
01-06-2020, 01:14 PM #6
Josh and I talked about this for a few minutes this morning and he thought it would be a good idea to get the info in one place for everyone. The knock sensors are probably more important to a set up like mine that will still see 91 octane. Even with a conservative tune.
I started looking into adding the sensor since my ECU is out and I can access the AUX plug. But when I looked up the inputs in Tunerstudio they didn't match the pinout of the PNP AUX plug.
01-06-2020, 08:03 PM #7
Resonant sensors are an OEM style of sensor that is usually usually tuned to a particular frequency and bore size. Bore size primarily determines the frequency of the the knock signal and therefor the point in the audio spectrum that is associated with knock in an engine of a particular bore size.
If the sensor has been tuned to that frequency, whenever that frequency is detected a piezo electric crystal in the sensor will output a voltage that approximates +1V. The MS3Pro ECU will interpret the presence of this voltage as indicative of knock and implement its pre-programmed knock suppression logic. Because these sensors are bore specific they do not transfer or translate well to other engines especially with larger or smaller bores.
A flat response, wide band sensor, on the other hand, listens across a wide frequency range usually between 5 and 18Khz. By using digital filters the sensor can be "pointed" at the frequencies that the Internal Combustion Engineer (ICE) wants to monitor for knock. When the sensor detects the sonic signature of abnormal combustion in its listening window it will produce an electric signal which the ECU reads and again begins its pre-programmed knock suppression logic.
The Bosch sensors that look like this,
tend to be the wideband sensors.
Tuner Studio has a complete section on Knock Sensor Settings beginning in § 7.3.7 Knock Sensor Settings in the MS3ProUltimate manual v. 1.205
The Mach I tune for the MS3Pro PnP unit uses the stock Ford wideband Bosch sensors. It might just be worth the effort to go into the TunerStudio s/w to see how and where DIYAutoTune set them up in the Mach I code. By copying their work you may well be able to use the same pinouts (unused on the Cobra harness) and integrate the wire pigtails into the existing harness wire bundle making for an easy and clean install.
Use two knock sensors, Ken. They aren't that expensive and MS provides support for both. The second sensor procvides a significant step up in individual cylinder knock specificity and therefore mitigation / correction.
01-06-2020, 10:02 PM #8
I just did a quick search using the part number on the sensor in the manual. That was the closest I could come up with. Naturally I'm still in the planning stages at this point. The short term goal is to get the wires connected to the AUX plug and ran behind the glove box. I did that for the flex fuel sensor so I wouldn't have to remove the kick panel again. I'm also wanting to run the wires for a speed sensor so I can eventually use traction control. A couple hits the other morning proved that might be useful.
Are we able to look at the Mach software? Also, would the Cobra computers have the pins in the main plug for the knock sensors? To be honest. I'd probably stick with using the AUX plug to keep things mostly simple. That's just me though.
The other thing that's throwing me is in the manual it says to hook up the knock sensor to the sensor input and return. There's nothing listed as that on the PNP. And maybe it's just me misunderstanding, but I don't see anything in the knock sensor settings in the TunerStudio software that match up with the AUX plug.
01-07-2020, 10:46 AM #9
The speed sensor and traction control can bring a breath of fresh air in these cars, as you've already discovered. The MS approach is especially attractive if you use their % slippage model for initiating traction control. Using % slip allows the ECU to optimize the torque to the tire on virtually any surface.
If you search on eBay you can find original Helms Wiring manuals for 03/04 Cobra's and Mach I's. It is a single manual that covers both, with the differences between the two wiring schemes documented very nicely.
Last edited by eschaider; 01-12-2020 at 04:10 PM. Reason: Spelling and Grammar
01-16-2020, 07:37 AM #10
- Join Date
- Nov 2010
I have my car running and knock sensor connected but I havent got to the point of setting it up so this is a timely discussion.
FWIW the Ford 4.6 Bosh knock sensor is like 10-20$, I suggest getting the one with the oem pigtail because its silicone, super heat resistant, and long enough to get out out past the headers.
It's nice that they have included that circuit because I had to buy a kit and install it in the MS3x, as Ed mentioned they could have used most any input for it so if its not documented in the manual they gave you call em up.
I have searched their software and downloads area and the PnP Mustang product page but don't see a tune to download. If anyone gets that tune please share. I have a feeling the knock sensor are is not configure, that might give them some responsibility.
Also if any one gets to the point of setting it up and test please post result here as will I.
01-16-2020, 03:42 PM #11
You are right about not seeing the tune in their downloads. I didn't search much farther because I had downloaded it previously. I suspect it is over in their support site somewhere but Here is the 99-04 GT tune I downloaded from their site a while ago.
p.s. The ModFords website does not recognize .msq filetypes so I changed the filetype to a MS Word filetype .docx. After you download the file switch th filetype back to .msq and the TunerStudio s/w will recognize it. Don't forget to build a new project for it so it doesn't change any of your existing Terminator code.
01-16-2020, 05:38 PM #12
This is what I received from Matt about the knock sensors: "The MS3Pro PNP uses the pins on the 104 pin connector that a Mustang GT would use - pin 57 for knock sensor 1 and pin 102 for knock sensor 2."
I was only going to run one sensor, but I'm looking at running two.
@MustangMikeMia, will those work with the iron blocks? I would think the aluminum would resonate at a different frequency than the iron. I'm no engineer, just thinking off the top of my head.
01-16-2020, 07:21 PM #13
Sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. Abnormal combustion (detonation) produces a distinct sonic signature in an engine. That is the good news, for detection purposes. The bad news is the sonic signature is tied to engine bore size and combustion chamber geometry. As you vary either or both of those two metrics the sonic signature of knock is also changed.
When we use knock sensors we are actually using small microphones to listen to the 'sonic signatures' of everything that is moving in the engine. Through the use of software filters we can ignore frequencies we are not interested in and point the microphone or perhaps more accurately tune the microphone to listen for those frequencies we have determined represent knock. When we listen to a particular frequency with our ears we hear a series of compression and rarifaction waves transmitted through the air at some number of cycles per second. One cycle per second is 1 Hz.
If we place a sound source at the end of a rubber bar and excite the other end of the bar at some predetermined frequency the probability that the far end of the rubber bar will vibrate at all, is small. The reason is that the energy of the sonic wave is absorbed by the soft rubber and converted into heat energy before it can reach the far end of the rubber bar. Do the same thing with a minimally compressible or non compressible medium and the sonic wave energy will arrive at the far end not measurably modified and likely not modified even over longer distances.
An other attribute that will be affected by the medium is the amplitude or volume of the sound wave. The softer material again absorbs the sonic wave energy turning it into heat energy and the amplitude measurable at the far end is diminished sometimes so much you can not hear the tone at all.
When we start looking at cylinder blocks in cast iron and aluminum it is clear without the use of instrumentation that cast iron is harder than any of the casting aluminums used for cylinder blocks. Not withstanding the difference in hardness the 356 T5 or T6 aluminums that are used in block castings are still impressively hard. Not only are they hard but if you locate the knock sensor somewhere near the center of the middle two cylinders the distance to the edge of the farthest cylinder approximates 200mm or less than 7.875 inches.
The block material and the distance to the farthest cylinder likely become insignificant in the detection process. What is most significant is the actual sonic signature or frequency which is why ECU manufacturers either OEM or aftermarket use tools to "listen" for particular frequencies they have determined signify detonation. Guys like DIYAutoTune and MegaSquirt have spent considerable time and monies earmarking these frequencies. Even with those, not insignificant efforts, the frequencies can move around because of bore size among other metrics.
If you have access to dyno time you can see on the dyno when additional timing no longer contributes the same sort of power increases it had previously. You may not be knocking yet but you are a hair's breadth away from knocking. Your engine is telling you to back off. If you use the knock sensing capabilities of the MS3Pro system you can probably identify the knock signature on your screen and use it as the gold standard to stay away from.
Bottom line it will be similar engine to engine within a given engine family and increasingly vary as bore size changes, combustion chamber geometry changes and basic engine metrics change. On our engines we know that 93 octane and 20˚ of timing is pretty frisky. If your day at the dyno tells you additional timing is bringing reduced power increases then the fat lady has sung — time to take a safe step back. Look at what kind of sound signature the knock sensor is 'hearing'. Dollars to donuts that is what you want to avoid.
BTW I know this is an old saw but, don't use the dyno to try to hit hero numbers. It is a tuning tool not a race track. Get the car properly tuned and then work out race track issues at the race track. Don't attempt to do it on the dyno.
01-17-2020, 12:06 PM #14
01-22-2020, 10:43 PM #15
Thanks for the link Ed. My sensors showed up today and I'm hoping to get everything in and wired this upcoming weekend. All that's missing is my ECU.