John Speake

I seem to remember the S4 knock system is effective somewhat lower than 3500rpm, when at large throttle openings.

Any situation where there is good cylinder filling...

With those later cars you can change the amount of retard per step as the system tries to kill the knock on the affected cylinder(s). You can also change the speed of each retard step.

Vlocity

I'm including a pic of my inlets before I went the SC route. The internal duct is a 3 inch ID suction pipe like they use on an industrial water pump. No collapse.....It's wrapped with the standard Nascar style reflective insulator.

I also put a small section just on top of the radiator to reduce that transfer in the area before the air pickup. Whether that little bit help or not I don't know, but you could lay your hand on the area without getting burned.

I am very interested in the Knock lite....although I'm not sure where to mount the sensor since my intercooled manifold is in the way of the first choice.

Any thoughts?

Last question are you running an LM-1 ?

Thanks.

Ken

Louie928

Hi Ken,
Nice insulating work. It'll help.
You asked about thoughts.... Regarding the Knocklite. Don't waste your time and money. Go with the real deal.
http://www.jandssafeguard.com/

Your intercooler should have enough room under it for knock sensors since it does for the S4 and up. Of course that is a hassle ^6 to take the SC off to mount the sensors and re-mount it again. For sensor placement, and from what I've read, the sensor needs to be placed on the cylinder block not the heads. Remember that it is the block that "rings" when detonation happens. The frequency of the"ring" is determined by the bore diameter. Any mounting of the sensor on the head picks up too much valve train noise and it's ascoustically insulated by the head gasket from the block. It must be mounted solidly to the block and about halfway down the bore is optimum if that is possible. The valley location of the stock sensors fits that criteria, however hard to get to. I did some testing on a GT block I have to see if there was another spot that would work. There is a couple of bolts at the girdle parting line that do work. The forward bolt (better of the two) is between the motor mount attach points and can't be reached with the engine in the car. The rear one works, but is quite far back and the front cylinder acuostics are attenuated. Faced with no sensor or this mounting point, I'd use this. You'd need a sensor on each side since the attenuation from one side to the other of the block is to much.

This less than ideal sensor location doesn't make such a difference with the J&S because the J&S develops a cylinder by cylinder background noise threshold. Cylinders with less sensor sensitivity have their knock threshold automatically adjusted upward as you run the engine normally.

Sensor location recommendations I'd follow are 1) The stock valley location with two sensors. 2) Valley location with one sensor in the forward mounting spot. 3) one sensor on each side at the mounting point in this picture.

https://rennlist.com/forums/attachme...1&d=1199726412
Sensor mount.jpg

Darien

Outstanding Louie If there's a way to test the difference between those and other locations versus the stock ones, that would be great info!

I've been hoping to find an "alternate" location for the knock sensors that wouldn't require removal of the SC

PorKen

Both of my 86.5's have shown little tendency towards knock. Granted, both have had the intake oil injection (PCV) system removed, and don't have cats.

With my old 86.5 and clone chip, I only could hear knock on 90°F+ days, when the cam timing was advanced. With the current 'super-chip', I don't register any knock with the KnockLite, even with 89-octane. Then again, it's only 40°F outside, right now.

To get some knock to test the light, I had to reinstall the clone chip, disconnect the WOT throttle switch input to the EZF, and drive up a steep hill. When it flashes red, you can hear the knock, but with the yellow you can't. (I backed off the throttle with either.)

For when the weather warms up, I'm installing a 5-pos rotary switch in place of the factory fader. That gives me four levels of high load retard, using the air temp input on the EZF (combined with ST programming, EG. 0,2,4,6,8), if I get a light. For stockish engines, like mine, I think this will be fine.

I reckon (turbo)supercharged engines would do well to have an automatic system, like Louie.

SWAG, but maybe the 85-86's smaller valves, and larger head volume make for less swirl, so the mixture doesn't burn quite as fast as 87-, and so is less prone to knock. (Whatever the reason, it's superior! )

Louie928

The front cylinders are quite a bit down in sensor output than the back three on the side the sensor is mounted and you get almost nothing from the other side. I didn't note how much difference. Enough to make me tear off my airbox, throttle linkage, and coils to open up the valley and mount the sensors there. Even so, I'd say sensing detonation in the back 6 cylinders is a lot better than none. At the time, I didn't know the J&S had a dynamic noise threshold for each cylinder. If anyone is contemplating mounting sensors there and want to use a J&S, give him a call as he will increase the max gain on his unit to be able to sense using a lower level sensor output. Connecting the sensors in parallel gives about 70% of the output that one sensor produces. If you need two sensors, then that is what you have to live with. The normal J&S has enough gain to work with two sensors when they are mounted in the valley. I'm not sure about this lower location. If mounting them there, have J&S (John) increase the gain so you know you'll have enough.

Bill Ball

The stock knock sensor bolt torque is rather low and supposed to be important. Would that alternative girdle location be OK with low torque on that bolt?

PorKen

You could use a stud, and two nuts?

hacker-pschorr

Interesting - same plugs I'm using under boost. The old hot-rod rule of running the coldest plug you can without fouling is skipped by a lot of tuners today.

Todd is using a non-projected NGK plug with his car one step cooler. Very popular plug with the boosted crowd.

PorKen

The NGK cross for WR5DC is BPR7ES, so the next coldest would be BPR8ES (NGK heat numbers are reverse of Bosch)... might have to try that. The colder the plug, the smaller the head chamber volume, too.

I haven't had any problem with carbon on either the '81 or '86 with the coldest Bosch#.

Pizza

I currently have my TS super charger off and would like to add the J and S knock sensors to my car (86.5). I have 3 plugged off spots in my V (see pic). Where do I put the sensors? Should I buy the sensors from J and S or use Porsche ones?

Thanks

hacker-pschorr

Todd is using the NGK plug on the left. It's the same heat range number without the "P" in the part number.

They are actually a very popular plug with not only the import turbo world, but snomobile racing. Our local farm supply / hardware store (Fleet Farm) stocks them for about $1 a piece.

Vlocity

Ditto for me, I have yet to "hear" any knock. I also have the oil injection (PCV) removed and it is routed to a catch can and also have the Cats removed. One other item that goes along with my very large cold air intake is that I have the tubular exhaust manifolds fully wrapped with header wrap as well as the entire exhaust. My under hood temps are about as low as you could hope for.....

That looks like a great system.....why is it that every time Louie posts it costs me $500. LOL (Although a lot less expensive than an engine)

Thanks for the picture....I just couldn't recall what mine looked like. Great questions...

What are you using for gasket material during your reinstall?

I will have to budget for the J & S. My next order of business is to get an LM-1 installed so that I can eventually Sharktune. Is the base unit good enough or do I need the one that also logs RPM.

Regards,

Ken

Vlocity

I may have to give those plugs a try.....funny you mention snowmobiles....that's the plug that I was running on my Skidoo Mach Z when I had the Nitrous installed. Sled was set up for Ice drag racing.

Ken

PorKen

Aha, the P indicating projection tip.

The coldest 928 threaded Bosch projected tip is the 5, WR5DC. But the regular, non-projected tip goes at least to 2, WR2CC. (D = projected, C = regular) According to a quick web search, the regular tip of the same heat range runs cooler. Higher compression, or supercharged engines like the regular tip, because the flame front can't be blown out as easily. Projected is better for emissions, and low speed operation.

So, I could try a WR5CC, especially if I dial in some cam advance (once I get the fueling right, and find where the real peaks are).

Sidebar: I found that non-resistor plugs don't work well with non-Bosch ignition amps.