odonnell

I don't have a 951, but I'm posting here because I'm sure some of you have used NA blocks when building a turbo motor and have sage advice. Basically, I'm after a knock sensing setup for my NA that I can rely on to be accurate for this block.

I'm not going to use a KLR, just run the sensor to my standalone and pull timing if knock is detected. I will eventually have the ignition table tuned on the dyno, but I want to be safe if I ever have to get lower octane fuel in the middle of nowhere or if something else changes in my tune that affects timing later down the line.

So given that the block is an '83, what are the best options for using a 951 knock sensor? It looks like it just bolts on. Any modification I would need to do, as far as physical drilling or tapping of my block?

Thanks for any insight!

Humboldtgrin

This is an 87 944S block. You may want to use two sensors like Porsche did. Don't know if an 83 block has previsions in the blocks casting for them to mount. If so you will need to drill and tap. The turbo only uses the front knock sensor mounting location.

V2Rocket

I don't remember if the boss is there or not on the 83 blocks.
But like I said the other day, I was able to put the sensor on an unused boss down by the bottom AOS port (on a 951, the intake manifold bracket bolts here) and pick up knock using a 951 sensor wired to the auxiliary port on my stereo. You can hear the knock sound distinctly through the speakers...pretty neat.

Mikes3.0cabturbo

thats neat, does the knock sensor just pass thru all noise or is it filtered to the knock frequency when it plays thru the stereo?

V2Rocket

There is very low-level background noise of the injectors firing and the cam lifters moving.
Kind of a quiet ticking in the background...but the knock sound is VERY distinct, the rattling/popping sound you would hear by ear, just amplified.

All I did was take a standard 3mm male-male auxiliary cable, cut the plug off one end, soldered the knock sensor wires onto it, ran the (long) wire into the cabin and plugged into the front of my stereo in the aux. port and turned it on.

odonnell

Interesting. Have pics of the location?

I'm planning on using KnocksenseMS (http://www.viatrack.ca/) which has an indication LED as well as informs MS to pull out timing. My only concern is that it would interpret head noise as knock. Unless it's smart enough to differentiate.

Raceboy

951 uses a single knock sensor in the middle where two M8 bolts are. I installed that way onto my 85 block that I used to build 2.5liter 16v Turbo engine. Works very well when reference noise levels are tuned for different engine load/rpm.

Early blocks do not have castings for dual knock sensors.

odonnell

Right - I'm just going to use one. Did you have to drill and tap the 85 block? I have a manifold-off service planned and will just pop it in with a suitable bolt if it's already drilled and tapped. Otherwise I'll do what Spencer did and find another place for it.

Raceboy

No need to drill or tap, the thread was already there for single sensor.

odonnell

Just to update this, I had to drill and tap a flat boss on my '82 block. Straightforward though.

Another question, relating to using an early block for turbo duty: the cylinder wall thickness. It's thinner than my '86 951 block. I'm going to run the '82 block, but was wondering what the real world limits are for safe power on them, if anyone happens to know. I was thinking in the neighborhood of 350 bhp for this engine - the rest of the engine will 100% be up to the task but if anyone can weight in, it would be appreciated.