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#1 |
Registered User
Join Date: Sep 2004
Posts: 10
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Decal under the hood states initial timing should be set at 0*.
Question is: Would it help my gas mileage(about 11mpg) increase if the timing is bumped to 8-10*btc. (Right now WinALDL reports very few knock counts.) And I just installed a new O2 sensor. Thanks Eddie ![]() 87 R10/TBI/5.7/Auto/3.42/10x31"AT's |
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#2 |
Account Suspended
Join Date: Dec 2003
Location: Texas
Posts: 2,686
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Doenst matter where you set the timing the computer will compensate automatically.
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#3 |
Registered User
Join Date: Dec 2002
Location: Stoney Creek, ON
Posts: 89
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They usually say 4 degrees are safe for a stock engine and you can advance up to 6 with some performance mods. I tried 4 on my stock truck and it knocked badly when the engine was hot and I stepped on the gas.
Jason |
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#4 | |
Registered User
Join Date: Dec 2002
Location: Stoney Creek, ON
Posts: 89
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Quote:
The ecm does not actually know what the base timing is. It assumes the timing is set to 0 degrees and advances or retards the timing according to the input from the various engine sensors. If you advance the base timing too much you can end up with too much advance during normal operation resulting in detonation. When this happens the ecm will have to retard the timing to where it does not knock. What you end up with is a driveability problem. |
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#5 |
Registered User
Join Date: Sep 2004
Posts: 10
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Jason: thanks for the info.
I've adjusted the timing to 4*btc. So far no pinging. Eddie |
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#6 |
Registered User
Join Date: Dec 2002
Location: Stoney Creek, ON
Posts: 89
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Try this forum for more info on tuning TBI engines.
http://www.thirdgen.org/techbb2/foru...php?forumid=17 These guys know just about everything there is to know about GM TBI. |
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#7 |
Registered User
Join Date: Jul 2001
Location: Atlanta GA
Posts: 1,704
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Unless your going to go through the trouble to get a real time set up so you can see how much timing advance, and the knock count the ECM is alowing or you dyno the car your are not going ot know if you are improving or screwing up. If you start tripping the knock sensor its going ot retard MORE then the 4 degrees you advanced it and acully make less power.
\ A lap top comuter and some sharware and a cable and you can do it. http://www.customefis.com/ Sells the cable and has a link to the site that has the Shareware and be a pall and slide the guy $10 on the pay pal for the software. That site also has a good library on how to customize the FI and will burn custom chips off of the data logs off the software.
__________________
Grim-Reaper 70 Pontiac LeMans Sport Convertible, worlds longest resto in progress Looking for 71-72 2wd Blazer or Jimmy Project |
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#8 | |
Registered User
Join Date: Sep 2004
Posts: 10
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Quote:
Eddie |
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#9 |
Registered User
Join Date: Dec 2003
Location: CT
Posts: 454
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Eddie,
I recently coverted over to TBI on my 85 and have been looking at things with Winaldl. Just curious, what numbers are you getting for knock counts? I was getting quite a few like 40 on the highway in a certain RPM/vac range, then hooked up EGR and went down to like around 3 over a 20 minute ride. |
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#10 |
Registered User
Join Date: Sep 2004
Posts: 10
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greg0380:
I get about 30 knock counts a week. This includes about 75% city and rest on the hwy. And usually under 100 miles per week. Intersting thing in WinALDL shows entering closed loop at 120*. Are you seeing the same? One other thing - I'll be installing a single exhaust in the next month or so (removing the non-cat true duals) and considering moving my O2 sensor from the drivers exhaust mainfold to a spot somewheres right after the merging in the y-pipe. This might help get a more accurate AF reading Eddie |
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#11 |
Registered User
Join Date: Dec 2003
Location: CT
Posts: 454
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I'm not 100% sure but I think the stock location for the O2 is on the drivers side about 4 inches below where the stock manifold connects to the Y pipe. That is where I put mine.
I have never pinpointed when it goes into closed loop related to temperature, but I don't think temp. is the only factor. I think if the computer sees that the O2 sensor begins to send valid voltages (.3-.9 volts) then it will go into closed loop. Are you running a stock chip? |
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