What does knock sound like?
 

I've heard audible knock before, mostly in full-size trucks pulling a load on low octane gas. I don't think I've ever heard it on a small 4-cyl. I was getting a slight waver (just a jiggle really) in my oil pressure gauge but never looked at it before now, so I don't know if what I'm seeing is normal.

I'm gonna run it tonight with the wastegate actuator disconnected and see if the gauge moves naturally at high RPM's out of boost.

But back to the question. What does it sound like on a small 4-cyl? I've got all sorts of new noises coming from the car thanks to this new turbo and can't pick out any obvious knock. I may pull the timing back to 8* until I get a WB for safety.

Any observations?

it's sound like a muffled can full of marbles shaking around. gotta listen closely, already enough rattles and shakes ;)

You've probably heard it a million times and just never realized it, especially if you drive in traffic with your windows down. Usually you'll hear it (from other cars) under slight acceleration or maintaining speed going up hill. Some people say it sounds like marbles, but there's really no accurate comparison.

Knock/ping/detonation/pre-detonation wouldn't have any effect on your oil pressure. (EDIT - I take that last statement back, read on) You say you've heard it on a big gasoline engine? It sounds the same on a small engine.

Once your ear is trained for it, there will be a neuron rearrangement in your brain going from your ear to right foot and you'll be amazed at how fast you let off the gas when you hear it ;)

[mr mackey]Detonation is bad, mkay[/mr mackey]

actually, The 90-94 oil pressure sensors are carbon resistance sensors. As the carbon is compressed, the resistance changes. Detonation shock waves travel through the carbon sensors with massive changes in resistance that is indicated by the gauge needle flickering wildly to the left.

you're fucking with me, right? lol :ugh2:

no go try it. boost 12psi without an intercooler and 10* timing.

quick search on m.net

Nope. I've seen it myself. However I think it quite prone to giving one a false positive.

What happened to the good old days when an oil pressure gauge was an oil pressure gauge? Guess I learned something today...but that's just plain odd.

It's an interesting side effect of how the sensor is constructed. I didn't realize (as Braineack pointed out) that the pressure sender was a carbon transducer but it makes sense- that would be a relatively inexpensive way to construct a reasonably accurate pressure sensor. It's also a good way to construct an inexpensive microphone, which is exactly how they did it in old-style full size telephones.

"rattle rattle rattle BANG BANG BANG boohoo boohoo boohoo. Oh man, fucked up my engine! :( "

The thing that really started to worry me wasn't the knock I could hear, but the knock I couldn't here. Friends I know that are running a link with a knock sensor show many knock events that they could never hear.

In my experience, it's sounded like rapidly-moving marbles in a can...almost like a mini Gatling gun.

yeah, ironically to me it sounds like pouring all my loose change in a coffee can so I can afford a new motor.

What you're telling me is that knock on a big motor sounds the same as knock on a small motor... that's good to know. I'm not hearing anything like that. How much should my oil gauge move when my engine is knocking? Will it make full left throws? or is it more of a slight 10psi flicker?

Now the next question. Is there an actual reliable/cheap/easy install/aftermarket knock sensor, maybe with a dash-mounted light that's worth looking into. It doesn't have to integrate with anything, just function as a standalone. For some reason, I'm really paranoid about this knock thing all of a sudden.

just watch the oil gauge, it will flicker pretty wickedly.

I'm sure there are more out there, this is the one I've heard most about.
http://search.ebay.com/search/search...tSearch=Search

That looks pretty spiffy, and less than $110 shipped on ebay. :yippee:

does it work?:confused:

From what I read on NASIOC a while back it does. You will need to by a proper knock sensor to go with it. The prices listed do not include one.

eh theres always a catch :P

The knockblock is cool because it will output an analog signal with knock, so if you could easily integrate it into either a gauge or an ecu that doesn't have on board knock sensing.

I think you can get a knock sensor for dirt cheap.

Yup. I like the FM one because it goes in place of one of motor mount bolts, but you could roll with a GM one for less $$.

Actually, I have the FM one that came with my (busted) Link, so if anyone needs the manufacturer name and part number, I'll get it.

and then abruptly stop :gay:

the FM sensor is a typical bosch unit found on saabs (among others). They will sell that knock sensor specific motor mount boss/bolt separately. It's the perfect solution IMO as it places the sensor below the crank centerline. I'm using one and had my sensor located all over the side of the block- with the near the front being the noisiest, and the lower motor mount (FM locale) the least noisy.

I think I"ve heard, its a rappid banging sound, that one day when someone sabotaged my miata for destruction lol , its like marbles kicking the shit out of a metal can, when oil was near gone thats when it started, somtimes can be heard under really heavy load, maybe If I didnt listen to so much damn loud rock music I could hear better :)

You confirmed that your link is toast? Was this a new or used unit?

Bummer.

Jay

It's believed to be faulty, pending analysis by Jeremy. So I'm sending it back to FM.

At least they didn't tell you that it was a user error and get bent :) Doesn't help your situation any. Mine still sitting in my basement waiting for the weather to get nice.

well they also haven't called back with my RMA # so......
:x:

i found a link with 550s on ebay,right now its only $100.
http://cgi.ebay.com/ebaymotors/1990-...QQcmdZViewItem

god dammit i hate you who ever is selling that why is it as soon as i buy something a better deal comes up :( atleast he sounds like a duche and wont end early. oh well it isnt that much of a better deal.

ahh well I wouldn't sweat it bro, there is always better/cheaper/faster. and it's missing all the sensors. to put it in perspective, the Link board is ~55% the total cost of the Link. You also need the IAT, MAP, and Knock sensors, and also the boost control solenoid, which are probably $400-500 total. Plus he's showing the closed case, who knows what's really inside, and if it's really a Link board, it will need a chip update. :dunno:

Also, I'm not sure what those 4 wires exiting the ecu case are for.

FWIW, I'm sold on the J&S Ultra Safeguard units. If you don't want to buy new, you can find them used for ~$250 if you're willing to wait.

John also gives great support. I sent mine to him for some custom programming that I requested to work with my Autronic ECU. Got it back a week later and it works great.

The knock sensor on my TEC2 was completely useless. So much background noise that you couldn't see minor knock. Same problem when I tried to use det cans. The knock was already pretty bad by the time I could hear it over the rest of the engine. Any 'dumb' knock sensing system is going to have the same problem. You need a system that looks for knock only when it's likely to happen in the combustion cycle.

Now I THINK that the TurboXS knocklite does use a detection window, but it still counts on you seeing it and reacting to it. I also don't like how you can't directly adjust the sensitivity on it. The J&S can correct knock so fast that I don't even notice it on the monitor, but my datalogs show that it pulled timing.

When I forgot to export the emanage map my car knocked really bad. It didn't sound like marbles, more like a faint rod knock. I heard it when I was taking off from a dead stop, I pulled over right away, exported the map and it went away.