Detonation

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Can someone tell me, if I'm looking at the timing arrow on the belt cover and the 6 notches in the crank pulley are to the RIGHT of the mark when I use the timing light, was I ADVANCED or RETARTED.

I can tell you that it was WAY OFF when I broke in the cam and I think the engine may have been pinging, for 20min. Problem was I needed to do the 2000RPM thing to break in the new lifters etc.. and couldn't check the timing.

Also, this car has a knock sensor, so will that help to minimize detonation damage. Do note that I adjust the timing manually on this car by moving the distributor.
 
I'd think it is advanced, if the indicated timing is to the left of the timing marks. If it's not even hitting the timing marks, wouldn't it be way off? On my car I think the last timing mark is 20 degrees BTDC, which is twice spec (spec calls for 10 degrees).
 
When you say 6 notches, do you mean 6 nothces that indicate the timing, as in timing marks on a fixed little tab that cover the crank pulley?

Like this:

timing_mark.jpg
 
You can tell whether you're advancing or retarding the timing by the idle speed. Advancing the timing will increase the idle speed while retarding will decrease the speed.
 
OK, let me explain what happened. And tell me what to do. I turned the car on after overhaul, and I immediately needed to break in the new camshaft and new lifters for 20 min at 2000 RPM.

Once I started the car, there was an insane exhaust sound like a leaking manifold, like the car was coughing. It seemed slow like it was going to stall then I hit the gas hard and went to the 2000 RPM, and held it there varying it for 20 min. Insane smoke was coming out but my guess is this was oil that was all over the block and was just burning off after the overhaul. There was also a strange rattling or spinning sound - that went away after the 10 min mark. The valves had quite a bit of oil in them when I was assembling, and the pistons were well oiled during assembly.

Then I looked at the exhaust manifold to header pipe flange and it was glowing red, it was SO HOT (after this 20 min). Take foot off gas, it would do the coughing thing again, and almost stall. Coolant gauge never went into red. Radiator fan was working and would turn on and off on it's own.

Smoke started to calm down after 20 min until now it's gone completely.

Put the timing light on it next try and there is an arrow like where your tab is above in the photo with the lines in it, it's just an arrow, and those lines that indicate the degrees are on the pulley. The lines on the pulley were WAY OFF to the right side, almost 45 degree off.

I started to turn the distributor AGAINST the direction of the rotor spinning, which means I turned the distributor CLOCKWISE as the rotor turns COUNTER-CLOCKWISE. I turned it all the way to the end of the range and it brought the timing marks within the arrow but not to the center (15 degree BTDC + or - 2 degree is what the manual says for timing) I got it to like 5 degree at the end of the range. So then I lifted up the distributor and jumped 1 tooth by turning it CLOCKWISE. Now I swung it to the other end of the range where the hold down bolt is, and it's close but on the other side, so it's sitting at +25 degrees right now at that maximum of the range. The car sounds WAY smoother and that strange exhaust noise is gone. However, the radiator last night started to get steamy and it smelt like coolant was evaporating and I saw liquid on the bottom of the radiator. I turned the car off. Coolant gauge never moved off of center.

So as you can see, I can't get it to 15 degrees because 15 is in the MIDDLE of the two distributor teeth.

Now here's the messed up thing. I SUSPECT the LH camshaft pulley (distributor is on LH side too) is off by 1 tooth at the timing mark. I couldn't get it to line up when installing the belt no matter what, the dot on the pulley was either to the left of the mark or the right of the mark on the timing cover. I installed the pulley with the dot to the LEFT of the mark on the rear cover. In other words, it was half a tooth off on either side.

QUESTIONS:
a) Could this POTENTIAL 1 tooth off on the timing belt cause the scenario where I can't get the distributor to line up to 15 degree BTDC?

b) In the initial scenario, did I detonate the engine if those timing marks were down to the RIGHT side in your photo. In other words, I was likely NEGATIVE degrees, as when I rotate the distributor CLOCKWISE, the timing marks on the right would move TOWARDS the arrow.

Now I notice at +25 degrees the idle speed seems HIGHER at 1000 RPM. It sounds smooth but it's higher.
 
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Well if your cam timing is off, then I'd go back and start there! But I'd think even if the cam that drives the distributor is off, as long as the distributor was installed correctly, the cam timing wouldn't affect it. Well, it migth now that I think about it because the gears on the distributor are pretty wide, so you might not be able to get the ignition timing adjusted correctly.

If you have the exhaust cam off by a tooth, I'd get that fixed before doing anything else. At least on my car, there's a hex built into each cam where you can stick a wrench on there and turn the cam to get the timing marks aligned.
 
I agree with Drew, you first need to make sure the timing belt installation is correct. That exhaust flange may have gotten red hot because the valve timing was off far enough to allow combustion in the exhaust manifold. But it probably was not engine damaging detonation.
 
The engine wasn't under any load, so something would have to go spectacularly wrong to cause any damage via detonation.

Not saying that your engine is ok... I have my doubts after THAT story. But I don't think you'll have any damage due to detonation.

+2 on the preceding advice: Make sure the cams are timed properly, then proceed to the ignition timing.
 
Thanks guys for the response. I made some progress. Drained the coolant, removed the hoses, removed the drive belts, and now down to the timing belt. Removed the covers.

I can see visually that the RH side camshaft pulley (firewall side) dot is lined up perfectly with timing mark on the cover. I can see that the LH side camshaft pulley (radiator side) dot is off by half a tooth to the LEFT side of the timing mark on the rear timing cover. I can see that the crankshaft sproket is lined up perfectly with the TDC mark (compression stroke) on the oil pump housing.

I'm going to move that LH side pulley to the right by one tooth, because if I move it to the left it's going to be even further away from the dot on the timing cover. Once I move the sprocket to the right by one tooth, the mark will then by approx. half a tooth to the RIGHT of that timing mark, maybe ever so slightly less than half a tooth, it's tough to say.
 
I see what your saying. In that case, I'd consider trying a different timing belt.

If everything is kosher, which it should be, all the timing marks will align perfectly.
 
I too think the marks should align perfectly. Perhaps you would do well to compare the new belt with the old. Do they have the same number of teeth? If the marks are still visible on the old, are they in the same place as on the new one? Perhaps a picture of the belt on the sprockets would help us.
 
There is a Tech service bulletin on the timing belt.
NTB93-154
The camshaft,crankshaft sprocket,tensioner springs were changed on VG30E all applicable models.Be sure to use a belt with the correct tooth shape.
New design is half round
Old design is square
A couple of other thoughts.Is it possible the cam sprockets are interchanged or on reversed?
I have no idea how they look or the key position but on some engines the sprocket is marked f or front or l R but if turned over it also has marks and will fit the opposite side,the mark will be slightly off.
No idea if this is the case here.

Edit Found this on the TSB
http://maxima.theowensfamily.com/tsb/NTB93-154.pdf
 
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Thanks guys, I moved it over last night one tooth to the right. The belt actually has no markings on it, and the old one had no markings either. Plus the markings won't tell me where to position the camshaft pullies anyways, as really what the dots mean on the pulley is lining up the knock pin straight up.

Trav that's good info, I checked up on that before I bought the belt and I have the square tooth design because my 93 has a 92 factory production date. Camshaft pulleys only install one way on the VG. LH sprocket goes on radiator side. RH sprocket goes on firewall side.

Now that I moved it one tooth to the right, I'll try it like that. If it runs rough, I'll turn it off immediately so I hopefully won't detonate it.

I looked up retarded timing and this is what I found:
===============
Retarded timing also raises the exhaust gas temperature considerably. This raises the thermal stress on the pistons, spark plugs, valves, exhaust system and turbocharger. In severe cases of retarded timing, the mixture is still burning when the exhaust valve opens. Because turbochargers are driven by the energy in the exhaust stream, high EGTs caused by retarded timing produce so much energy at the turbine that even a fully open wastegate cannot control the boost pressure.
================

I suspect I was grossly retarded when the exhaust manifold-to-header pipe flange got cherry red. Fire was likely entering the down pipe heating it up like crazy. At least it's not the detonation scenario. I also checked the spark plugs and they look perfectly fine. A machinist told me usually you can see clues on the spark plugs if detonation is occuring.

By the way I checked the Maxima forum and they said that the dot doesn't line up perfectly. I also talked to several machinists and they said sometimes the dots don't line up exact, they aren't that accurate SOMETIMES.

Point is, it's a [censored] shoot for me, the LH side was half tooth off on either side of the dot, so I had to pick 1 side. I'm picking the other side of the dot becasue if I moved it 1 tooth to the left, it would be even FURTHER from the timing mark on the rear cover.
 
Thanks Flanso. I think your right about the combustion in the exhaust manifold all the way down to the down pipe. = retarded. When I started moving the distributor and the marks moved towards the arrow, the idle speed went up, and that misfiring sound (exhaust sound) started going away, which means I was advancing it.

Let's see what happens when I seal it up and put the coolant back in.
 
yes, that's from the service manual - same as mine. That's how the LH dot looks now, slightly to the right of the rear cover dot.

Although the cartoon drawing may look that way because of the angle of their drawing, and plus, it's just that - a cartoon.

Thanks though Trav, let's see what happens.

By the way, how the [censored] do you apply 22 lbs of downward force on the belt to check deflection when I'm working in the wheel well. I could do it when it was on the stand, but it's impossible for me to read a ruler when the chassis is blocking it.

How do they do it in a shop, when they change the belt without removing the engine?
 
Originally Posted By: flanso
You can tell whether you're advancing or retarding the timing by the idle speed. Advancing the timing will increase the idle speed while retarding will decrease the speed.


Not always. It can be advanced to the point that it loses power also.
 
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