do knock sensors extend the life ...

[Kurt B]

of those engines that have them?
Anyone know when 911s first got knock sensors and is there any evidence they might extend the life?

I was in the 84 a few days ago, and even though I'm easy on the car now, I decided to gun it on the freeway up through third.
Now, after around 5,000 rpms (full throttle) in third (but not in other gears probably due to the wind resistance at 3rd and higher gears but not those lower), the car pings like a mother fukker and a bunch of gray smoke shoots out the exhaust (as I can see in the rear view mirror).

Anyone know if this means my 84 is going to visit the reaper, and given this, does a car with a knock sensor get some additional life because it would retard the timing in such conditions?

thanx.

[Bill Verburg]

Do knock sensors extend the life of those engines that have them?

Absolutly, as long as they are working, see the recent threads about damage from preignition.

'89 964 was the first oem implementation, and is one of the reasons 964/993 t/p's are such a good decision.

lots of cars will be knocking inaudibly, if you hear it regularly that is not a good sign

As the miles are piled on, carbon buildup in the combustion chamber raises the cr making older engines more susceptible to this malady.

[Kurt B]

Thanks bill. The part about squirting water into the afm (through the filter I guess) enough to almost make the engine die and repeating a few times seems insane--people using this to get out the carbon.
If I do this, will it work?
I squirt enough to almost get the car to die, and repeat a few times, and then let the car sit a day, and the carbon will absorb the water and weaken and potentially blow out on start up later?
Is this really a workable solution or snake oil?

[Bill Verburg]

If I do this, will it work?

Dunno, that technique has been around for ages, never tried it myself, My C3 used to audibly knock when leaded gas disappeared , I just switched to 93 octane which cured the problem. If you are experiencing knock w/ 93 then there isn't much else to do but try things like that.

[Chuck Moreland]

Kurt

Squirting water can definitely remove carbon. And in my experience it doesn't need to sit overnight, the carbon comes out immediately.

The first time I did this I had another car parked 6 feet behind the exhaust pipes (RSR muffler). The front of the car was splattered with bits of carbon.

Yes, it works.

[Kurt B]

I'm going to go for it. No doubt, the 84 is a pinger. Thanks. I'll let you know what happens (crossing fingers).

[tshih]

Too much water in the engine will hydrolock and die from bent conrods as water left in the Comb chamber is noncompressible.

Chuck Moreland, the carbon from the exhaust may be from the cat, pipes, and muffler. I really doubt it is carbon from the engine.

[Bill Verburg]

Originally posted by SoCal911SC
They can help, but can only do so much, as you have found out with your car.

If your car is "pinging like a MF" you are damaging the engine, knock sensor or not. If it is audibly pinging, the knock sensing system has maxed out and isn't helping past that point anymore.

He has an '84, no knock sensors

[Tyson Schmidt]

Ever seen the combustion chamber of a car with a bad head gasket that's leaking coolantr into the combustion chamber? Totally clean of carbon compared to the other cylinders. The trick does work. Just be careful.

About 7 years ago, my old 2.4 T motor was pinging under low rpm high load situations, so I decided to try this trick. I was pouring water very slowly down the throat of #4 cylinder (mfi) when one of co-workers startled me. I flinched, and spilled a bunch of water into #4 at about 3000 rpm. The motor died.

It started back up and ran fine after that, but it slowly began to smoke more and more over time. I put about 25K miles on it after that, but the smoking became worse and worse. Eventually, when Jack Olsen and I were running my car at a DE, it became really bad. We made it all the way back to L.A. from Pahrump Nevada, however.

When I tore the motor down, I found a piston pin circlip had dislodged and tore up cylinder #4. The constant hammering also cracked the crankshaft, and hammered #7 main bearing. The motor was almost a complete write-off.

It wasn't until about a month later that I remembered the decarbonising incident, and then it all made sense. At the time, I just couldn't figure out why the circlip broke.

Just be very careful how quickly you pour in the water, and make sure you keep the rpm's up while you do it. On non-MFI or carbed cars, it will be very difficult to make the same error I did though, so you should be safe. In fact, it may be difficult for you to get enough water in there to do the job, since it is awkward, and all 6 cylinders are getting the water.

[Chuck Moreland]

Originally posted by tshih
Chuck Moreland, the carbon from the exhaust may be from the cat, pipes, and muffler. I really doubt it is carbon from the engine.

SSIs into a new RSR muffler. I don't do cats.

Good idea to use a squeeze bottle to avoid the spill-hazard Tyson experienced.

[jyl]

I've been interested in ways to add a knock sensor to the 3.2s. Here is one method that I've read good reports on:

http://www.jandssafeguard.com/safeguard.html

Still, it seems to me that your car should not be pinging (assuming right fuel and not Death Valley hot), and finding out why it is would be the first step.

[wheatdog]

I've decarboned a few cars over the years and I NEVER pour water into the intake in any way. I use an adjustable spray bottle like a used trigger pump windex bottle. Set the idle up high(2500 or so) and spray the mist into the intake until the engine starts loading up. Back off on the amount being sprayed if the engine rpms drop way off. That's water in the bottle not windex!! Usually there will be a good shot of poop out the exhaust if the combustion chamber is caked. This avoids the possibilty of liquid locking the engine and possible bent rods etc.
Works for me and haven't damaged one yet.

Mike

[Kurt B]

I did try it (before I read tyson's note )...a little at a time, and i never really got the car to die or really shift its RPMs.
After I had a little in there, I started it, and raised the RPMS just a tad (like 3k and it did die). I started back up after it set for a few minutes and I just let it idle.
After that and making some phonecalls I decided "water + Kurt B + intakes = destruction" and decided to go get some additive that will maybe help instead. So, I got B-chemtrol or whatever it is (white steel can) and put that in and filled it up.
I didn't race it around much. Sounds fairly good after putting the additive + 89 octane in it. Idling nice today

I'll post it something goes wrong. It's got plenty of miles already, so if it starts smoking, then I'll just have to tear it down.

[Steve@Rennsport]

Kurt:

If I might suggest,.............

Use 91 in the Carrera, not 89. Thats not enough octane for a moderately (normal) carboned engine in warm-to-hot weather.

Detonation (pinging) just hammers the living hell out of the pistons, rings and bearings. That pinging noise you hear (over the normal noise of these engines) are 220K psi pressure spikes and it trashes these engine components in short order.

If you hear that, back off the throttle immediately, otherwise your bank account will suffer for it. You would not believe the number of these engines we've disassembled over the years with broken rings caused by detonation. In most of these cases, the owner claimed never to hear a thing so if you actually hear it, its very bad.

[Wil Ferch]

What about sub-audible preignition?....

Also..can experts here describe a detailed approach to doing the water injection for a fairly stock 3.2 ??

Wil

[Steve@Rennsport]

Originally posted by Wil Ferch
What about sub-audible preignition?....

Also..can experts here describe a detailed approach to doing the water injection for a fairly stock 3.2 ??

Wil

Hi Wil:

No such thing; its called "sub-audible detonation" which is a different situation.

Pre-ignition occurs when a glowing piece of carbon or a hot spot in the chamber lights off the fuel/air mixture before the plug fires. One usually finds melted ring lands and/or holes in piston crowns when this happens.

Detonation occurs when: (1) either a trapped pocket of fuel/air near or at the edge of the chamber spontaneously ignites due to heat or pressure or (2) the spark occurs at the wrong time.

The net effect in each case are huge pressure spikes and in the case of pre-ignition, melted engine components.

Water injection (not the decarboning procedure) can be used for detonation suppression if a very small & fine mist of water is sprayed into the engine under load. The problem is that many Porsche intake manifolds are designed to run "dry"; this means that they do not evenly distribute liquids to each cylinder, only air. Some cylinders get more liquid than others and its very difficult to correct that. One must simply inject water into each port above the fuel injector.


One note about using water to decarbonize an engine. This is not a risk-free endeavor and can result in small chunks of this hard carbon getting trapped between the valve and valve seat. I've seen this happen several times over the past 30+ years and the divot left in the seat and valve seat requires a valve job to repair. I just saw another one here recently in a 993,.......

Personally, I would use several treatments of Techron or LubroMoly Ventil Sauber each one followed by a few hundred miles of high RPM, high load operation. If that doesn't do the job, its really time to take it apart and do it right.

[Diesel_mp5]

Yha I definatly agree with Steve.... You need to use the highest octane gas avaliable expecialy if youre fuel is oxygenated. You should regularly be adding a cleaner to youre system, B-12 is good, if you arent driving it often. Fuel goes bad and seperates and will lead to knocking, and stink..... My 79Sc sat for 3 months, I started it up.. I thought it was going to blow up.. I changed the fuel filter and removed the bad gas. She ran like a champ. Diesel_mp5

[fastpat]

Originally posted by Kurt B
of those engines that have them?
Anyone know when 911s first got knock sensors and is there any evidence they might extend the life?

I was in the 84 a few days ago, and even though I'm easy on the car now, I decided to gun it on the freeway up through third.
Now, after around 5,000 rpms (full throttle) in third (but not in other gears probably due to the wind resistance at 3rd and higher gears but not those lower), the car pings like a mother fukker and a bunch of gray smoke shoots out the exhaust (as I can see in the rear view mirror).

Anyone know if this means my 84 is going to visit the reaper, and given this, does a car with a knock sensor get some additional life because it would retard the timing in such conditions?

thanx.

The old trick was to fill a coke bottle up with tap water and dribble it into the carb (remember those) while the engine is running at about 2k rpm. If you trickle it in slowly enough, the engine won't lose rpm's at all. Don't drown it. Of course the last time I did it was in the days before O2 sensors, so I can't tell you what getting that sensor cold will do for the engine speed, but, you don't want to pour it in fast enough to kill combustion. It's the physical action the water has with the carbon at the same time it partially flashes into steam which loosens and carrying the carbon particles out the tail pipe.

After the water trick, you do want to then drive the car long enough to boil the excess water out of the muffler. Say, about a 20 minute drive on your favorite road should do it.

Pat