Timing, what should it be at?
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
Originally Posted by RRT vette
BTDC
Burning Brakes
Joined: Jun 2006
Posts: 1,096
Likes: 28
From: Baltimore MD
Originally Posted by Sam Lam
..and some people (like I used to do!!!) will encourage you to kick the timing to somewhere between 8 and 10 degrees BTDC. Don't do this! If you ever obtain and use a scan tool, you will understand the previous sentence
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
rel3nd: In the L98 engine, the performance of the engine is programmed into a chip within the ECM. The ECM "assumes" a 6 degree BTDC timing. Advancing the timing above 6 deg TDC just increases your total timing by the difference. This causes your entire main spark table off by how ever much you change the timing above 6 degrees. A 2-4 degree increase may give you a little more "seat of the pants" feel of idle but it is quickly extinguished by the ESC if you get enough knock counts under load at high RPMs. The scan tool just allows you to visually see how the detection of knocks reduces the timing as the RPM and load are increased. I am learning with my scan tool and I am sure there are otheres who know a lot more about this than ole Sam 
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Originally Posted by Sam Lam
rel3nd: In the L98 engine, the performance of the engine is programmed into a chip within the ECM. The ECM "assumes" a 6 degree BTDC timing. Advancing the timing above 6 deg TDC just increases your total timing by the difference. This causes your entire main spark table off by how ever much you change the timing above 6 degrees. A 2-4 degree increase may give you a little more "seat of the pants" feel of idle but it is quickly extinguished by the ESC if you get enough knock counts under load at high RPMs. The scan tool just allows you to visually see how the detection of knocks reduces the timing as the RPM and load are increased. I am learning with my scan tool and I am sure there are otheres who know a lot more about this than ole Sam
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Burning Brakes
Joined: Jun 2006
Posts: 1,096
Likes: 28
From: Baltimore MD
Originally Posted by Sam Lam
rel3nd: In the L98 engine, the performance of the engine is programmed into a chip within the ECM. The ECM "assumes" a 6 degree BTDC timing. Advancing the timing above 6 deg TDC just increases your total timing by the difference. This causes your entire main spark table off by how ever much you change the timing above 6 degrees. A 2-4 degree increase may give you a little more "seat of the pants" feel of idle but it is quickly extinguished by the ESC if you get enough knock counts under load at high RPMs. The scan tool just allows you to visually see how the detection of knocks reduces the timing as the RPM and load are increased. I am learning with my scan tool and I am sure there are otheres who know a lot more about this than ole Sam
Thanks again.
Team Owner
Joined: Sep 2002
Posts: 22,209
Likes: 12
From: OBAMA IS HITLER
Originally Posted by cuisinartvette
I never felt any difference or noticed improvement in ET by advancing timing.
SOTP is king on the street for a daily driver, numbers are show off points and bragging rights for the hobbiest racer.
Pro
Joined: Jun 2001
Posts: 520
Likes: 6
From: Elverson PA
Originally Posted by Sam Lam
rel3nd: In the L98 engine, the performance of the engine is programmed into a chip within the ECM. The ECM "assumes" a 6 degree BTDC timing. Advancing the timing above 6 deg TDC just increases your total timing by the difference. This causes your entire main spark table off by how ever much you change the timing above 6 degrees. A 2-4 degree increase may give you a little more "seat of the pants" feel of idle but it is quickly extinguished by the ESC if you get enough knock counts under load at high RPMs. The scan tool just allows you to visually see how the detection of knocks reduces the timing as the RPM and load are increased. I am learning with my scan tool and I am sure there are otheres who know a lot more about this than ole Sam
rel3nd: In the L98 engine, the performance of the engine is programmed into a chip within the ECM. The ECM "assumes" a 6 degree BTDC timing. Advancing the timing above 6 deg TDC just increases your total timing by the difference. This causes your entire main spark table off by how ever much you change the timing above 6 degrees. A 2-4 degree increase may give you a little more "seat of the pants" feel of idle but it is quickly extinguished by the ESC if you get enough knock counts under load at high RPMs. The scan tool just allows you to visually see how the detection of knocks reduces the timing as the RPM and load are increased. I am learning with my scan tool and I am sure there are otheres who know a lot more about this than ole Sam
If you run better gas than the recommended 87 octane to you still see pinging in the high rpms? My car seems to run well at 8 deg advance, but I use 93 octane. Maybe I am better with the owners manual recommended 87 and 6 deg of base timing.
I once saw a magazine article in a Chevy mag about the editors at the track tuning a tpi motor they put an HSR on. They got about a 1/2 second improvement running about 12 deg instead of the base 6. When guys program chips don't they just advance the timing anyway? The point of the magazine article was that you can dial your car in to your mods by changing the timing and the fuel pressure. I am so confused......please help.
Here is the link. I understand they add timing due to increased air flow, but most people here have different mods that increase their air flow and lower temps. http://www.gmhightechperformance.com...hird_gen_iroc/
Dave
Last edited by black85; Nov 18, 2006 at 09:54 AM.
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
Black85: Your questions are beyond my knowledge of the TPI engine. I suggest you send a PM to "gbody5" as he is very good with tuning on TPI engines.
Rel3rd: I use Turbo Link for a scan tool and you will need a laptop computer. The Turbo Link package comes with a cable and software. The software is Windows based and the software is very friendly. Here is the web site and there is a demo available from the site: http://www.turbo-link.com/. The cost of the package is $280.
Rel3rd: I use Turbo Link for a scan tool and you will need a laptop computer. The Turbo Link package comes with a cable and software. The software is Windows based and the software is very friendly. Here is the web site and there is a demo available from the site: http://www.turbo-link.com/. The cost of the package is $280.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
I need time to really play with my scanner, but I've been running 8* and 87 octane in my 87 for 4-5 years, no pinging and last time I ran the scanner I was within all parameters. Mines all stock and I really feel I get better performance at 8 vs. 6*. I wonder if mileage plays a factor here, I have 110K on the clock (i.e. timing chain stretch).
Pro
Joined: Jun 2001
Posts: 520
Likes: 6
From: Elverson PA
Maybe. I have 130k. But the main thing I am trying to say is, from that article, it looks like you can advance the timing when you have increased the airflow to your motor. It doesn't say exactly that, but it does say that they thought the new intake manifold would require more advance. They then prove it on a dyno and on the dragstrip. They also mention it would be intersting to see how much a custom chip would help them, if at all, after dialing in fuel pressure and timing.
Basically, if your car is stock I wouldn't really think adjusting the timing would help too much. If you have done mods to get more air into your engine faster, than you could probably add timing advance. I would love to hear someone's thoughts that knows more about this.
Dave
Basically, if your car is stock I wouldn't really think adjusting the timing would help too much. If you have done mods to get more air into your engine faster, than you could probably add timing advance. I would love to hear someone's thoughts that knows more about this.
Dave
