Timing and Idle Speed

Advancing the timing is synonymous with "free horsepower." This is the cheapest modification that you can do to an SR20DE engine. SR20DE engines come with the timing set from the factory anywhere between 10 to 15 degrees BTDC. If you advance the timing, then you will at the least gain crisp throttle response and at the most gain horsepower. But how much timing do you need to advance? In their July 1999 issue, SCC advanced the timing of their 1991 Sentra SE-R to 21 degrees and gained 6 hp. They claim that there was no detonation what-so-ever. Mike Kojima, however, believes that there is no horsepower to be gained beyond 19 degrees. As such, he suggests advancing the timing between 17 to 19 degrees and using 92 octane gas. I think Mike's advice is safer than SCC's 21 degree timing. Mike insists that you use 92 octane gas. So please do so. If you do not detonation might destroy your engine.

Here are the tools that you will need:

• A timing light. I purchased an Innova digital timing light. In addition to measuring the timing, it allows me to measure the idle speed on a digital display screen. The price was $99 from Pep Boys.

• A 12 mm socket with a ratchet or a 12 mm wrench.

Here is the method as stated in the FSM:

1. Start engine and warm it up until engine coolant temperature indicator points to the middle of the gauge. Ensure engine speed stays below 1,000 rpm.

2. Run engine at about 2,000 rpm for about 2 minutes under no-load [this means turn off all accessories].

3. Rev engine two or three times under no-load, then run engine at idle speed for about 1 minute.

4. Turn off engine and disconnect the Throttle Position Sensor (TPS) The TPS is shown in the image to the left. It is the plug that is on top (brown). An SE-R mailing list member told me that only the the 1998 and 99 models come with two plugs. I f you have a pre-1998 model you should only have one plug. That will be your TPS.

5. Start engine.

6. Rev engine (2,000-3,000 rpm) 2 or 3 times under no-load [This will lock the engine in timing mod]. Let engine run at idle speed.

PS: When I was at the SoCal February 19th meet, Mike Kojima set my timing. The procedure that he followed was a lot simpler than the one listed in the FSM. He warmed up the car to normal operating temperatures, disconnected the TPS while the car was still running, revved the engine three times to about 3,000 rpm to lock in the engine in timing mod, and then adjusted the timing. I like this procedure and I will use it in the future.

Hook up your timing light to the battery terminal and the inductive pickup to the number one plug wire as shown in the picture to your left and your right. The Innova will immediately begin to read your idle speed and the strob light will flash. Turn off the strob light from the control panel on the timing light.

There are two bolts to the distributor, one on top and one on bottom. Loosen both of them as shown in the images to the left and to the right.

Aim the timing light so as the timing light, the pin (pointer) above the crank pulley, and the marks on the crank pulley are in a straight line. The image to the left is taken in a straight line and shows the pointer (pin) that I am referring to. While your flashing the timing light, have a friend move the distributor cap in a direction that will advance the timing marks on the pulley. The timing marks are shown in the image to the right.  On the 200SX SE-R the 13-15 degree mark is marked with a solid white paint strip. You need to move the distributor in a direction that will move the pointer above the pulley to somewhere between the 15 and 20 degree mark. If you want 18 or 19 degrees position the pointer a shade below the 20 degree mark. If you want 17 degrees position the pointer in between the 15 and 20 degree mark.

If you are running Unorthodox Racing pulleys, then your crank pulley does not have the solid white 13-15 degree mark. Simply position the pointer a shade below the 20 degree mark. That should give you 18 degrees.

If you are running JWT S3/S4 cams with the stock ECU, set your timing to between 13-15 degrees. The JWT cams do not like advanced timing. My car gained more power (3-4 hp) up top when we lowered the timing on the S3 cams from 18 to around 15 degrees.

If you are running the JWT S3/S4 cams with the JWT ECU, set your timing to 15 degrees and use 92 octane gas.

While the TPS is still disconnected, you can check your idle speed. The FSM recommends setting your base idle (with TPS disconnected) to 750 rpm. To adjust your base idle turn the idle speed adjusting screw that is shown in the image to your left. Since I am running JWT cams, I set my base idle 50 rpm higher. This has helped reduce the lumpy idle speed due the the JWT cams. After your done reconnect the TPS. The tachometer on the Innova should read 800 rpm. As you can see from the image to the right my idle is higher than the 800 rpm recommended by the FSM.