Advance Timing Help

[wannamjd]

I want to advance the timing on my car, but I've gotten alot of conflicting information from the boards. Does anyone know for certain if this is possible or will my ECU always set the BTDC timing at 10 degrees? (standard for K8) I've read through my Chiltons shop manual and it seems simple enough, short the TEN (test engine) jumper in the diagnostic connector while the engine is idling, use a timing light, and rotate the distributor to adjust the timing.. easy enough.. the problem is I don't have a timing light and I don't want to spend 50-100 bucks for one. Could I do this by the TLAR (that looks about right) method? Or I guess in this case, that sounds about right...<P>I know that I will have to run 92 octane gas, from what I've read. But I'm still unclear as to why changing my spark timing would require more octane? Isn't higher octane just for higher compression ratios?<P>Here's some other posts I found:<P>ZUNE MX-3 Gs <A HREF="http://www.mx-3.com/cgi-bin/ultimatebb. ... 5&t=001236" TARGET=_blank>http://www.mx-3.com/cgi-bin/ultimatebb. ... =001236</A> <P>Searching in Probetalk I founded this post:<P>To advance base timming then <BR>1.start the car <BR>2. with the car running ground the STI conector <BR>3. loosenthe two bolts that hold the distributor in place. <BR>4. use a timming light to calibrate and move the distributor just a little at a time. <BR>5. when you get it where you want it the tighten the bolt back down and remove the jumper between the ground and the STI conector <P>In my case I have added as nuch as 9 degrees of timmng, but if the car mis fires or backfires then you need to retard it somewhat or use a better graade of fuel.<P>boostedmx <A HREF="http://www.mx-3.com/cgi-bin/ultimatebb. ... 1&t=001025" TARGET=_blank>http://www.mx-3.com/cgi-bin/ultimatebb. ... =001025</A> <P>turning the distributor sets the base timing in the mx3. it does effect the ignition timing. to get an accurate reading u will have to use a timing light. crank angle sensors sense where the crank is at. its a signal sent to the computer for reference purposes. there are a bunch of reference signals used by the computer to determine if timing needs to be advanced or retarded. but the base timing will always remain the same- and is adjustable. <P>And this article:<BR> <A HREF="http://mw.dsm.org/tipdetail.asp?TipID=13" TARGET=_blank>http://mw.dsm.org/tipdetail.asp?TipID=13</A> <P>Thanks guys!<p>[ September 26, 2002: Message edited by: NCRedGSV6 ]

[lazzyie]

considering that the whole purpose of the knock sensor being to run the engine to the brink of detonation, im 90% positive that the old trick of advancing timing doesnt work anymore because of all the sensors involved, the timing advances automatically throughout your powerband, as for using racing gas to stimulate the ecu into reponding, DUH!, im sure dave/pelado will correct me if i am wrong though.

[andy]

I liked the third example you gave best.<BR> <A HREF="http://mw.dsm.org/tipdetail.asp?TipID=13" TARGET=_blank>http://mw.dsm.org/tipdetail.asp?TipID=13</A> <P>This topic comes up alot between the three boards. You must have done a search,(thank you) otherwise you wouldn't have examples.<P> You can adjust the distributor to effect the base timing. This effect is only present at startup. After which the ecu will<BR>optimize the timing based on sensors.<P> About the octane, I use 92-93.<BR>Opinions vary all over the place from low to high,(89-94). I would also refer back to your third example as my answer. If you switch octanes,<BR>allow some mileage to pass before making a positive or negative decision.<BR> In conclusion, do more research and when your 100% sure of your answer let the rest of us know.<P> Andy P. 93 GS

[BATTOSAI]

I´m working on modifying it by altering the reading of two sensors. As soon as I have something reliable I will post it as soon as possible. Think I´ve got some clues from an additional ecu´s builder (you know those little boxes installed before the ECU)

[Kid Racer]

Isn't the whole point of changing the timing done so you can run a higher octane gas more efficiently(for more HP)??? The higher the octane gas, the longer it will take to burn.right? a higher octane gas also burns more completely therefore giving more HP. But to run a higher octane gas you have to advance the timing because the gas will take longer to ignite/burn. I guess if you ran a really high octane fuel with stock timing the fuel wouldn't burn until after the piston already passed TDC(the top) and in turn losing hp. I have asked a couple of shops about changing the timing and they said the computer would try to change it back and make the engine run crappy.<P>BEWARE This may not be true! If it isn't, I would like to know, so please post.

[Mike 94PGT]

The goal of advancing the timing is to maximize cylinder pressure when the crank pin sweeps past TDC: the higher the pressure here, the more work is done on the piston on the way down on the power stroke. Usually, running advanced timing will require the use of knock-resistant (read "high octane") fuels due to the increases in peak cylinder pressure. Lower octane fuels may experience detonation when used in a high-advance spark setup.<P>Regarding setting the disty position on 92-94 V6s: turning the disty does nothing to affect the overall spark timing. When you set the base timing, you ground the TEN pin. This forces the PCM to set a fixed spark advance value. More importantly, it forces the PCM also to use the NE1 crank position sensor in the distributor (mounted on the igniter.) So the PCM is getting crnak position signals referenced from the sensor in the disty: if the disty is rotated, the sensor moves and, therefore, so does the crank position signals with respect to the crankshaft's true position. Once this "base" timing is set, the TEN pin is released and the PCM (a) is allowed to vary the spark timing and (b) reverts to using the NE2 crank position sensor (mounted near the crank pulley.)<P>With the PCM getting crank speed & position info from this sensor its clear that the position of the NE1 sensor makes no difference. Setting the base timing is really only doing the following:<P>- sets the cranking sparktiming to 10oBTDC (the PCM uses NE1 during cranking)<BR>- properly positioning the rotor in relation to the plug towers on the disty cap<BR>- setting the position of the camshaft position sensor (the other sensor on the igniter)<P>It does not affect run-time spark timing. All you're doing is moving the cranking-timing out of spec, the plug towers away from where they should be and altering when the PCM gets cylinder #1-coming-to-TDC info.<P>The knock sensor is not used as suggested. Spark timing is derived from numerous factors, ranging from load & RPM to a corrective term for idle-speed stabilization. All of these terms are added together and then several terms, such as high-intake air temp and knock retard terms, are removed from the sum to get an overall spark timing value. If the PCM 'hears' knock from the knock sensor it will simply increase the value of the knock retard term.<P>Running on knock-threshold timing all the time would be very bad for emissions and power. Timing requirements for an engine vary alot during operation, ranging from high levels of advance during light-load cruise to low levels during low-RPM, high-load operation.<P>Spark timing changes should really only be accomplished by changing the PCM calibration tables. The K series V6s benefit from small increases in overall timing but not much. Too much is as bad as not enough: if the cylinder pressure peaks too early, the piston is having to do excessive work against the prematurely expanding mixture as it rises on compression.

[lazzyie]

to Mike!!!