Tuning the Timing
Thread Starter
Racer
Joined: Jun 2002
Posts: 411
Likes: 0
From: Palm City FL
Tuning the Timing
Last time I was at the track, I spent some time trying to dial in the timing.
I checked the timing by unplugging the brown plug by the brake booster, reving the motor to about two grand and using my dial back light to find zero.
I started with 8 degrees, which is where its been since I assembled the motor. I retarded it to 6* and slowed a couple mph. I advanced it to 10*, and again slowed from my original runs.
On every run (including 8*) i saw knock counts at shift pulling several degrees of timing. That never changed.
I was wondering though if I was doing it right? Am I supposed to disconect the batt to reset the computer after changing the timing?
Is there a way to get the knock retard out during shifting?
I checked the timing by unplugging the brown plug by the brake booster, reving the motor to about two grand and using my dial back light to find zero.
I started with 8 degrees, which is where its been since I assembled the motor. I retarded it to 6* and slowed a couple mph. I advanced it to 10*, and again slowed from my original runs.
On every run (including 8*) i saw knock counts at shift pulling several degrees of timing. That never changed.
I was wondering though if I was doing it right? Am I supposed to disconect the batt to reset the computer after changing the timing?
Is there a way to get the knock retard out during shifting?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Tuning the Timing (severe-1)
What are your shift points? Are you running premium fuel?
Assuming there is not some metallic "clang" causing knock counts, replace the ESC module with the upgrade unit, details on my site (link in sig. below).
You might also try upping the TPS min voltage (at base idle of 450rpm) to .65Vdc and tweak the TPS for max WOT voltage.
Then tweak base timing for best trap speed. Here you only need to open the connector in the tan/blk wire and set base timing at normal idle of around 700-800rpm.
Assuming there is not some metallic "clang" causing knock counts, replace the ESC module with the upgrade unit, details on my site (link in sig. below).
You might also try upping the TPS min voltage (at base idle of 450rpm) to .65Vdc and tweak the TPS for max WOT voltage.
Then tweak base timing for best trap speed. Here you only need to open the connector in the tan/blk wire and set base timing at normal idle of around 700-800rpm.
Thread Starter
Racer
Joined: Jun 2002
Posts: 411
Likes: 0
From: Palm City FL
Re: Tuning the Timing (65Z01)
I am running premium fuel and my shift points are 5500.
How much was that esc module and where is it located? (Funds are tight, Christmas)
I dont know if it will idle at 450rpm, it idles rough at 700.
I will check that out though...
How much was that esc module and where is it located? (Funds are tight, Christmas)
I dont know if it will idle at 450rpm, it idles rough at 700.
I will check that out though...
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Tuning the Timing (severe-1)
Your might want to wait till after the Holidays and you've had a chance to check for other possible knock causes; ESC module GM P/N 16038331 cost me $55 from my local Chevy dealer. It is a rather flat rectangular object located just inside the right fender panel in front of the firewall, near the blower motor housing.
To get to base idle you need to fully extend the IAC pintel and then disable the IAC motor; details on setting base idle and tweaking the TPS are also on my site. These tweaks alone provide more fuel & timing advance so improve throttle response and overall performance. Then taking base timing to the max with no ping is the frosting.
To get to base idle you need to fully extend the IAC pintel and then disable the IAC motor; details on setting base idle and tweaking the TPS are also on my site. These tweaks alone provide more fuel & timing advance so improve throttle response and overall performance. Then taking base timing to the max with no ping is the frosting.
Burning Brakes
Joined: Feb 2003
Posts: 1,246
Likes: 1
From: SouthBend IN
Re: Tuning the Timing (65Z01)
you need to set the base timing at idle, not 2K.
if the car is warmed up it will ( should) stay running when you unplug the timing wire.
Always set base at idle.
if the car is warmed up it will ( should) stay running when you unplug the timing wire.
Always set base at idle.
Thread Starter
Racer
Joined: Jun 2002
Posts: 411
Likes: 0
From: Palm City FL
Re: Tuning the Timing (mike 1985)
I found at idle, the timing was irratic and hard to pinpoint. Maybe it's my Snap-On timing light, its given me trouble in the past
I've always set total timing by revving to 2000rpm and settin to 36*. (obviously carb cars)
I'm not used to seeing 6*.
The only way to know final timing value is with Diacom or Auto-Xray?
How do you tweek the final value without screwing with initial?
I've always set total timing by revving to 2000rpm and settin to 36*. (obviously carb cars)
I'm not used to seeing 6*.
The only way to know final timing value is with Diacom or Auto-Xray?
How do you tweek the final value without screwing with initial?
Thread Starter
Racer
Joined: Jun 2002
Posts: 411
Likes: 0
From: Palm City FL
Re: Tuning the Timing (65Z01)
Okay, i just checked my diacom runs from the other day. My tps voltage at idle is .63 volts. At WOT its 4.65v. I did notice my IAC was aroung 110 counts at idle. Is this okay or should I lower my idle screw?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Tuning the Timing (severe-1)
If that TPS value was at normal idle it's likely around .54Vdc at base idle of 450rpm.
You could try rotating the TPS slightly around the upper screw to get a normal idle value of about .73Vdc, which corresponds to about .65Vdc at base idle. If that value sets a code just back off .01Vdc at a time till the code is no longer thrown.
With a warm engine the IAC count value should be around 28 counts; maybe the pintel or bore is dirty.
You could try rotating the TPS slightly around the upper screw to get a normal idle value of about .73Vdc, which corresponds to about .65Vdc at base idle. If that value sets a code just back off .01Vdc at a time till the code is no longer thrown.
With a warm engine the IAC count value should be around 28 counts; maybe the pintel or bore is dirty.
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Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Tuning the Timing (severe-1)
Okay, i just checked my diacom runs from the other day. My tps voltage at idle is .63 volts. At WOT its 4.65v. I did notice my IAC was aroung 110 counts at idle. Is this okay or should I lower my idle screw?
I had to play with my TB adjustment quite a bit a few weeks ago when I swapped to a BBK 52 mm from the stocker.
Before the swap, I had my counts in the 20-30 range, but the BBK didn't like counts that low. To lower the counts to the 20-30 range, I had to open the TB butterflies to a point that when I lifter off the accelerator pedal at highway speeds, the engine would not drop down in rpm.
I tried all sorts of difference settings - still trying to duplicate the 20-30 IAC count - but couldn't.
I finally fell back on a philosopy I'd use over the years: let the engine tell me what it wants and likes.
Using that, I ended up with counts in the low 50s and all else was normal.
If I remember correctly, max counts are 160, so 110 doesn't leave the IAC much room for increasing idle speed as load on the engine increases - such as when you turn on the A/C.
I suggest you do as I did, play with the TB minimum airflow adjustment screw until you find what works best.
Just my experience.
Jake
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Tuning the Timing (severe-1)
Last time I was at the track, I spent some time trying to dial in the timing.
I checked the timing by unplugging the brown plug by the brake booster, reving the motor to about two grand and using my dial back light to find zero.
I started with 8 degrees, which is where its been since I assembled the motor. I retarded it to 6* and slowed a couple mph. I advanced it to 10*, and again slowed from my original runs.
On every run (including 8*) i saw knock counts at shift pulling several degrees of timing. That never changed.
I was wondering though if I was doing it right? Am I supposed to disconect the batt to reset the computer after changing the timing?
Is there a way to get the knock retard out during shifting?
I checked the timing by unplugging the brown plug by the brake booster, reving the motor to about two grand and using my dial back light to find zero.
I started with 8 degrees, which is where its been since I assembled the motor. I retarded it to 6* and slowed a couple mph. I advanced it to 10*, and again slowed from my original runs.
On every run (including 8*) i saw knock counts at shift pulling several degrees of timing. That never changed.
I was wondering though if I was doing it right? Am I supposed to disconect the batt to reset the computer after changing the timing?
Is there a way to get the knock retard out during shifting?
There is an ESC module that is less sensitive to spark knock and is recommended by Gordon Kilibrew; part # 16038331.
I wouldn't worry about the counts if they're only occurring during shifts.
Jake
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Tuning the Timing (severe-1)
I've always set total timing by revving to 2000rpm and settin to 36*. (obviously carb cars)
RACE ON!!!
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Tuning the Timing (severe-1)
Okay, i just checked my diacom runs from the other day. My tps voltage at idle is .63 volts. At WOT its 4.65v. I did notice my IAC was aroung 110 counts at idle. Is this okay or should I lower my idle screw?
Actually you would do just the opposite.
To lower IAC counts at idle, you would open the TB butterflies using the minimum airflow screw on the TB. The more open the butterflies, the lower the IAC count in order to maintain desired idle speed (burned into the PROM).
If you adjust the TB min airflow screw with the engine running, you may need to shut down and restart before the IAC will again take over controlling idle speed.
Jake
Thread Starter
Racer
Joined: Jun 2002
Posts: 411
Likes: 0
From: Palm City FL
Re: Tuning the Timing (JAKE)
Well its been awhile since i screwed with the TPS or the IAC. I started out asking about timing and went all the way around to setting the idle :crazy: :lol:
Soon as I find a little bit of time a will reset everything again. After that, it's back to the track. Then I'll try the new Knock sensor and check the results.
Thanks guys for adding to my vette "to do" list.
:grouphug: :thumbs: :cheers:
Soon as I find a little bit of time a will reset everything again. After that, it's back to the track. Then I'll try the new Knock sensor and check the results.
Thanks guys for adding to my vette "to do" list.
:grouphug: :thumbs: :cheers:
