Knock sensor location SBF?

[Daniel Lorenz]

Hi again,
trying to install the last sensors on the engine for the EFI.
One that I haven't been able to get any good information on yet is where I should place the knock sensor.
I found several threads that warned about placing two (one for each bank), but none that actually talked about the best location for a sensor on the original block.
Any thoughts?

Second question is placement of IAT (inlet air temp) sensor.
I will have a hard time fitting it in the collected inlet or throttle body.
So I was thinking about drilling it in the lower air filter plate that mounts onto the throttle body.
The sensor would not read the average air temp in the inlet, but atleast it reads the ingoing air.
Would that be accurate enough?

 

[Daniel Lorenz]

I'll add a last question.
CTS placement (coolant temp sensor) is tight for me since i use fuel rails that collide with the predrilled 3/8 bungs in the rear coolant locations on the intake.
How wrong would the reading be if installed in a 90 degree elbow to connect the sensor?
I understand that the flow in the elbow will be limited, but the sensor would still be in the vicinity of the main coolant flow.
See picture to maybe understand the dilemma

 

[JP Verweij]

By my knowledge, knock sensors are not universal at all. They need to be calibrated for a specific frequency corresponding to the engine & location they are fitted to.

You might concider a different route with EGT sensors as a safety control feature for your EFI system. EGT acts way quicker then a knock sensor.

 

[Joel Heinke]

My experience is that you'll get a much lower coolant temp reading at the rear of the engine versus the front. On a 5.0L engine in my Cobra, I tried locating the temp sensor for coolant fan in the hole at rear of intake. The engine temp as measured by gauge sensor at the front of the engine would be well over 200 degrees and cooling fans were not activated by the 190 degree sensor. I relocated the cooling fan sensor to upper radiator hose and cooling fan would activate at the temp it should. In addition, I don't think you'll get an accurate reading by putting the sensor in a tee or 90 fitting as it will be removed from the coolant flow.

It was a pain to locate the additional sensor in the radiator hose (didn't have any available ports at engine front) but it's where the coolant is at its maximum temp. You should also consider the thermostat when positioning the sensor. Until the thermostat opens, the temps upstream will be different than in the engine itself. If you locate an ECT sensor beyond the thermostat, the ECU will likely get a delayed reading during engine warmup. If you have limited ports in the engine front, you might want to prioritize the ECT sensor placement over a gauge sensor placement.

 

[Ian Anderson]

Not a good plan to add an extra piece.

I did just that on my motor and ran a T piece on the oil sensor location to get pressure and temp. Engine was breathed on 3.9 Rover Derrived V8…..from Morgan….same engines in Land Rover and Range Rover and those ran coil coolers.

Water would run at 85 to 90 Celsius
The oil temp from the T piece ran 55 to 60 Celsius
Infra red thermometer on the sump was around same temp as water.

Knowing this I could then estimate the oil temperature and if it went up I looked for somewhere to park and cool down

Ian

 

[Michael]

Daniel, the temp sensor probe has to be immersed in coolant flow path at all times to read accurately. Adding an elbow could end up holding the probe in a static air/steam pocket.

You may want to modify the fuel rail with a flush AN plug and then re-drill and tap another hole location for the fitting.

 

[Adam C.]

We typically mount the knock sensors high in the valley, between the middle cylinders on overhead cam engines, and on the outboard side of the cylinder block on pushrod engines.
Pushrod engines have too much valvetrain noise in the valley and heads that will cause false positives.
Calibration is necessary. We also have sampling windows around the combustion events to avoid the noise of valve closing events as much as possible.

 

[Ryan L]

Makes you wonder if this is one of the considerations in firing order these days.

 

[Daniel Lorenz]

We typically mount the knock sensors high in the valley, between the middle cylinders on overhead cam engines, and on the outboard side of the cylinder block on pushrod engines.
Pushrod engines have too much valvetrain noise in the valley and heads that will cause false positives.
Calibration is necessary. We also have sampling windows around the combustion events to avoid the noise of valve closing events as much as possible.

So that would mean that your recommendation for a SBF would be on the outer side wall of the block then?

Regarding adding EGT's I did have a plan on doing that, but since Holley doesn't like to cooperate with the rest of the market I can't buy a stand alone EGT/CAN reader. I have to buy Holley's EGT module that costs as much as the whole EFI system.
It's outrageous!

 

[Adam C.]

On the outside near the deck surface between cylinders 2-3 and 5-6. Get as close as you can to the bolt column. The mounting needs to be very rigid.

EGT: Most sensors robust enough for daily use are too slow (thermal capacitance too high) to get accurate readings on anything but a steady state dyno pull. We use 1/8” dia thermocouples mounted temporarily in the header primary just outside the exhaust port during calibration. Even then, it takes about 30s to get to steady state temp readings. Race teams use 1/6” TCs but they fail within a few pulls. Use enrichment to target 1650F.

 

[Daniel Lorenz]

Last time I installed an EGT sensor it was a narrow tip version.
Main body was 3/8 and tip was 1/8 to get faster response times.
Don't know if it was fast enough, since I sold the car shortly after.