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Discussion Starter #1 (Edited)
This procedure outlines one method of adjusting the ignition timing's base advance on '00 and '01 Sentra SE 2.0s, equipped with the SR20DE engine. Though it is theoretically possible to advance the ignition timing on QR25DE and QG18DE engines, this article will not help, because they do not have distributors; they use more modern but arguably less friendly coil-on-plug ignition system. To complete this procedure, you will need a standard timing light and 12mm wrench or socket; I'd have both tools handy, if I were you. ;)


First on the order of business is to get your engine up to operating temperature. You don't have to be hot, necessarily, but the ECU has to be ready to accept your changes, and the coolant temperature has to be normal (not cold) to do so. Go for a trip to Dairy Queen or something and go through the drive through. This has a double benefit, in that you will certainly spend enough time with the engine running that the needle will be up, and that Blizzards rock! I prefer the Butterfinger Blizzard, but I digress...
If you have a manual transmission, leave it in neutral. If you have an automatic, it should be in either Park or Neutral. Once the engine is up to temperature, you need to rev the engine past 3000 three times. The FSM says "Rev engine (2,000 to 3,000 rpm) two or three times under no-load," but we're not exactly following the FSM-approved method here. ;) Just to be thorough, I rev higher and rev three times just to be very sure that I've set the triggers right on the ECU.


Next up is to disconnect the TPS (Throttle Position Sensor) harness. There are two plugs attached to sensors behind (on the firewall side of) the throttle body. The top one is brown, and it's the one we're concerned about. I'm not sure exactly what the gray one is or does, but leave it alone. When you disconnect the TPS, you should hear the idle speed noticeably rise; just like if you turned on the air conditioner. This picture is pretty poor, but you should at least be able to see the color, position, and location of the plug I'm talking about. Mine is currently disconnected; it should be placed directly over the gray connector.


Once the ECU is in the timing adjustment mode, it's time to hook up the timing light. It doesn't have to be fancy; mine is a Craftsman model from Sears that's quite a several years old. I remember helping Dad by using it to diagnose the rough idle in our '79 Lincoln Continental. That car died a horrible but unspectacular death long before I got my driver's license, and I know that the timing light has been in our garage far longer than that. You can invest in one with a digital tachometer and a dialback function if you like, but they're simply not necessary.


Generally, they have three connections; a spark plug wire probe, a positive power clip, and a negative power clip. The probe goes around the wire for plug #1; make sure that it's securely around the wire, and not stuck open. You can see which wire triggers #1 in the third picture of this group.


Attach the power wires as directed in the light's owner's manual. You can see how my light attaches directly to the battery posts. I wouldn't recommend that you attach to the battery posts, but again, laziness got the better of me. If I had arced the connections, and there were a leak in my battery, the battery could have exploded, sending me on a trip to the Emergency Room.


Good thing the ambulance station is at the end of my block, eh?

This is where things get just a little bit hairy. Where you stand while checking the ignition timing is important. If you are not standing directly above the accessory drive pulley, you will not be able to accurately read the advance indicator marks, and you may not get the rest of the procedure right because of it.


You should stand on the passenger side of the car, with your feet almost directly out from the axle. This isn't Canon, but do be careful. Place the timing light between the coolant overflow tank and the cylinder head, and check the base timing as it's adjusted on your car. You can't see very clearly in my picture where the pulley is, but you should trust me, it's down there. If you drew an imaginary line along the red stripe on my light, it points directly at the marks on the pulley and the indicator.

First, verify that your ignition timing is adjusted properly, then aim for your performance and fuel consumption goal:

15 degrees of advance is stock. Use 87 octane or better fuel.
17 degrees is recommended for a little power. Use 89 octane or better fuel.
19 degrees is where SR20DEs with stock internals and computers generally make their best power. Use 91 octane or better fuel.
You can get away with lower-octane fuels than these if you live in high altitudes, but unless you have a dyno and are able to tune it on the spot, do not exceed 19* of advance.


To actually adjust the timing (advancing or retarding), you need to physically turn the distributor in its housing. There are two bolts holding the housing down, as illustrated in these pictures; you must loosen them both, or the housing will not turn. Don't go crazy with this, just back them out enough so that you can twist the housing. They should still be tight enough that you can let go of the housing, and the timing doesn't change on its own.
When the bolts are loose, rotate the housing counter-clockwise (top towards the firewall) to advance, or clockwise (forward) to retard. When you've reached your ideal timing setting, tighten both bolts down, and clean up. Reattach the TPS harness, turn the engine off, and restart the engine to assure that you didn't damage anything. The odds of you damaging something are pretty slim, but anything is possible, right? :)


To recap, the Nissan ECU is a very sophisticated thing. To adjust the base timing, you have to jump through hoops to prove to the ECU that you know what you're doing and that you intend to do it. The first hoop is getting the engine to normal temperature; this makes sure that the ECU is running the engine in (!!!) normal mode. Next, you rev the engine three times, to get the ECU's attention, as if you were knocking on the door. Third and finally, you disconnect the TPS, which tells the ECU that you either intend to adjust the base timing, or that you intend to adjust the base idle. As always, failure to follow these directions exactly may not produce the result you wanted.


It's also recommended that you disconnect the battery overnight after changing this, and let the ECU spend a couple of days getting used to the new capabilities of the ignition. When done properly, this advancing procedure has been dyno-proven to yield several horsepower, sometimes as much as 6 HP in various places along the curve! Enjoy your handywork and your Blizzard; you da' man! ;)

Written by: CowboyDren
 

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The cars are set at 13º +- 2º from the factory.

stock cammed (sp?) cars like 19º or so, at least with the newer lowports. 91 intake cammed cars don't like quite as much. Aftermarket cams like the S3's or S4's like a lot less, around like 13º's.

The reason you won't see a factory car running 19º is because they are designed to run crappy 87 octane gas. Also, even if they specified 91 octane or better there's still a chance of detonation at higher ambient temps and/or with poor tuning. That'd be a lot of hassle for manufacturer's to deal with under manufacturers warranty when everyone's car was out of tuen they'd start knocking, with the possibility of blown motors... probably not a good idea...
 

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JustinP10 said:
The cars are set at 13º +- 2º from the factory.
Actually they are suppose to be set at 15 degrees +/-2 from the factory. But we all know that's not always true.

By the way, how the hell'd you get the degree's to show? (What character keystrokes is it?)
 

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DOH! You're right. Brainfart.... :-\

Alt + 0186 =)
 

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how high altitude are u talkin? im at 8000 if i run 19 degrees should i still use 91?
 

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I bumped the timing on my 93.5 two days ago, using this post and the FSM as backup. Just one point, in the FSM it says to
1. Get engine to operating temp.
2. Rev 2-3 times.
3. Turn off engine and disconnect TPS.
4. Restart and rev 2-3 times to 2000-3000 rpm.
5. Check and adjust timing.
6. Check idle again.
7. Turn off engine and reconnect TPS.
At this point I also checked for slop in the rotor/distributor (should have done this first) adjusted and rechecked timing. I found a degree of slop and readjusted back up to +19.
Makes a noticable and nice difference in performance.
Thanks for the writeup and pics.
 

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Actually, Gorilla, you can use 89. The higher your altitude, the lower the octane requirements. Actually, '00-02 (roller) G20s can most likely get away with 89 as well, since that's what I run in my '01 Sentra these days. If it doesn't knock, you don't need more octane. If it does knock, you either need more octane or less timing.

As Justin said, factory timing is 15°, ±2°. ;) The timing is set at this number to allow you to run 87 octane fuel, and to keep the idle smooth. The ECU then adds and removes timing respectively, according to RPM, throttle position, and knock sensor feedback. When you bump the timing, the ECU assumes that the mechanical advance (distributor's physical orientation) is still set at 15°, even though it's actually 19°. This makes the entire timing map more agressive by 4°, which releases more power from the fuel.

When you bump up the timing a bit, the idle quality may degrade slightly, but it's not annoying at all in my case, and the power gain is 100% worth the trouble.
 

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I just tried the ignition timing procedure posted on this board and the procedure posted on the SE-R.net board. The procedures are 180 degrees out on which way to twist the distributor to advance the timing. The SE-R said the engine would probably die if the throttle body connector was removed which mine did. I had to get my daughter to keep her foot on the gas peddle to keep the engine running. It was hard to check the timing because the idle speed was varying all over the place while my daughter tried to keep it at 800 rpm as shown on the tach. This boards procedure said the idle speed should go up to 1000 rpm with the throttle body connector removed. It looked like the timing was about right so I left it where it was. With the throttle body connector reconnected the idle speed stabilized and the timing mark was at about 14 or 15 degrees (in the white painted area) so I guess it is good. Could I adjust the timing with the throttle body connector connected? It appears it would give a much more stable reading.
 

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victor said:
I just tried the ignition timing procedure posted on this board and the procedure posted on the SE-R.net board. The procedures are 180 degrees out on which way to twist the distributor to advance the timing. The SE-R said the engine would probably die if the throttle body connector was removed which mine did. I had to get my daughter to keep her foot on the gas peddle to keep the engine running. It was hard to check the timing because the idle speed was varying all over the place while my daughter tried to keep it at 800 rpm as shown on the tach. This boards procedure said the idle speed should go up to 1000 rpm with the throttle body connector removed. It looked like the timing was about right so I left it where it was. With the throttle body connector reconnected the idle speed stabilized and the timing mark was at about 14 or 15 degrees (in the white painted area) so I guess it is good. Could I adjust the timing with the throttle body connector connected? It appears it would give a much more stable reading.
What's happening is your base idle is off, you want the revs to be around 850 iirc with the TPS disconnected, if it's off then it needs adjusting...

You can't adjust it with the TPS connected cause the ECU would just retard it back...
 

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Victor, it's probably time that your entire intake (tb, manifold, and emissions gear) gets a thorough cleaning. After cleaning, you'll need to enter the timing/idle mode I mentioned above, and set your base idle to 800 (manual) or 850 (auto), IIRC. Whatever the high limit is on idle speed; refer to your owner's manual.

After that, adjust the timing. As for the SE-R.net vs. My directions concerning rotation, mine are right. I initially blindly copied the SE-R directions, and they were wrong, so I fixed my copy. As for my proceedures differing from the FSM proceedures, I said that plainly in the first part of my directions. My way is a LOT faster, and just as effective.

:p ;)
 

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if I was to take my car in and have the timing advanced...how much do you think it will cost and what should my timing be advanced to??
 

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Many people report $20, since it's a 5-minute proceedure. For $25, you can get your own timing light and do it yourself whenever you like (especially for Californians). The optimal setting for 91-octane fuel is 19°.
 
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