My oops , wrong way around
Timing Question
Thread Starter
Melting Slicks
Joined: Jun 2005
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From: Arkansas
Timing Question
I have a 90-92 SD TPI installed in my 82. Custom chip.
I unplug the est connector and set the base timing at 6 degrees BTDC. When I plug the connector back in the timing jumps to 28 degrees BTDC at idle.
I was wanting to make sure this is normal .....because my car runs like crap right now and everything is new....I wanted to check this first before I start troubleshooting other things.
I unplug the est connector and set the base timing at 6 degrees BTDC. When I plug the connector back in the timing jumps to 28 degrees BTDC at idle.
I was wanting to make sure this is normal .....because my car runs like crap right now and everything is new....I wanted to check this first before I start troubleshooting other things.
Last edited by 1982CorvetteDude; Dec 30, 2008 at 03:59 PM.
Le Mans Master
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From: Australia
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From: The Top of Utah
It sounds like too much to me. The jumping up is proper, as explained, but 28° is more than I've ever seen. Of course, what ever it jumps to is what is programmed into your custom chip. That chip must be for an engine with a lot of duration. Are the ECM, chip, and engine a matched set?
Does "90-92 SD TPI" mean 1991 - 1992 speed density Tuned Port Injection? If so, the 1992 used the LT1 with a totally different ignition system.
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Originally Posted by 1982CorvetteDude
I have a 90-92 SD TPI installed in my 82. Custom chip.
RACE ON!!!
Le Mans Master
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From: Australia
Pro
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From: Toronto ON
Le Mans Master
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Race Director
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From: The Top of Utah
"For SD '730/727 $8D
Total Timing = BaseTiming + Main Spark Table + PE Timing - Knock Retard"
Total timing at WOT maybe. Except maybe in theory and actual programming how do knock retard and especially PE figure into the ignition timing at idle?
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- 1986 Original Owner -
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From: The Top of Utah
Originally Posted by Ray Quayle
It's the LV8 Load Varible.
Obviously I have to get more into programming and tuning. I have just barely started reading a book on that just now.
I still say, "It sounds like too much to me. The jumping up is proper, as explained, but 28° is more than I've ever seen.". And let me clarify, at a normal idle speed.
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Racer
Joined: Jun 2007
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From: Sandy Ut
Well I will throw my 2 Cents in. I have a 90 and my stock timeing unpluged was set to around 6 BTDC and when I pluged it back in the timing jumped up a ton, but I would say that yours jumped way to much. I am thinking mine jumped to somewhere near 20 but I could be wrong. I would go out and do it again, except the motor is out of the car this winter.
Melting Slicks
Joined: Mar 2004
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From: Pittsburgh Pa
It sounds like too much to me. The jumping up is proper, as explained, but 28° is more than I've ever seen. Of course, what ever it jumps to is what is programmed into your custom chip. That chip must be for an engine with a lot of duration. Are the ECM, chip, and engine a matched set?
Does "90-92 SD TPI" mean 1991 - 1992 speed density Tuned Port Injection? If so, the 1992 used the LT1 with a totally different ignition system.
RACE ON!!!
Does "90-92 SD TPI" mean 1991 - 1992 speed density Tuned Port Injection? If so, the 1992 used the LT1 with a totally different ignition system.
RACE ON!!!
i know if you get a programmed chip you wound not want more then 6 degrees base timing or it will run terrible.. and like mentioned above you need to get the idle to like 850 to make sure you are setting the timing correctly.
Le Mans Master
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From: Australia
LV8 = inverse RPM * airflow * scalar
From 3rd Gen Prom
"LV8 = (((DRP * gms/sec) / 256) * Scalar) / 64
The DRP can be found be reversing the RPM calculation:
DRP = 983040 / RPM -gives- 983040 / 1550 = 634
Then gms/sec at 14.01 and the scalar of 80 (decimal):
(((634 * 14.01) / 256) * 80) / 64 = 43 (the LV8, or Load Variable, 8 bits)."
As you correctly state there would be no PE or knock retard at idle.
1000 rpm is hi-lighted because that is where the cursor was when I took the screen shot.
Bottom line is he needs to know what SA has been programmed on his tune and what base timing it was set for.
NB;Many people with stock chips have reported gains bumping the base timing to 8-10 degrees.
Last edited by rodj; Dec 31, 2008 at 11:01 PM.
