Timing at idle...
Thread Starter
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Timing at idle...
...what are you shooting for? Looks like I've got about 32* at 950 idle. Base of 6* and computer is adding 26*. Seems high to me. Would something like 21* total be more acceptable? Or is it just becuase I have a higher idle with this cam.
Engine Speed : 950rpm
LV8: 43
IAC: 14
Timing: 26.4 + 6 32.4* total.
Engine Speed : 950rpm
LV8: 43
IAC: 14
Timing: 26.4 + 6 32.4* total.
Melting Slicks
Joined: May 1999
Posts: 2,037
Likes: 0
From: Sarasota FL
Re: Timing at idle... (scorp508)
Shoot for what your engine likes. With a hot-cam-ish cam, mine's higher than stock. I found my idle timing by turning the distributor with the engine idling until I found best vacuum, then burning the advance into my program. I've been told too much advance at idle increases heat and wear, so don't go too far.
Also, I like to shoot for 0 IAC with a warm idle and no accesories on. With the cammed motor, you'll need the full range of the IAC for it to work well.
Also, I like to shoot for 0 IAC with a warm idle and no accesories on. With the cammed motor, you'll need the full range of the IAC for it to work well.
Drifting
Joined: Mar 2001
Posts: 1,636
Likes: 3
From: Lafayette IN
Re: Timing at idle... (scorp508)
I am running a slim 19 in the bin right now. With my cam, it needs to come up some. However, in SD bins, there are adders and subtracters in the routine (that aren't listed in TC FWIR) that can be added if you get ahold of a hack...
so actual timing becomes Base + Advance +/- (adder or subtractor). About the only thing I can see these being used for are corrections for RPM that would react too slowly to IAC movement.
http://forums.corvetteforum.com/zerothread?id=556467
so actual timing becomes Base + Advance +/- (adder or subtractor). About the only thing I can see these being used for are corrections for RPM that would react too slowly to IAC movement.
http://forums.corvetteforum.com/zerothread?id=556467
Intermediate
Joined: Aug 2002
Posts: 35
Likes: 0
From: Iowa City IA
Re: Timing at idle... (scorp508)
I have been playing with 6E code (ARAP & APYP) for about 4 years now. Only in the last year have I played with the 32B code (ABTZ) in my 88.
The last scan I have for my ABTZ code shows:
Engine Speed = 750
Load = 42
IAC = 44
Spark Advance = 22.9
I have my own scan software, which I trust.
I am not familiar with the EASE software. Do you know if EASE is showing you words 39 & 40 or 41 & 42 of the serial data stream? Words 39 & 40 reflect the timing with respect to TDC which would include the initial 6 degrees. Words 41 & 42 are with respect to the reference pulse, which is the additional timing that the computer adds to the initial 6 degrees. In other words, there is a 6 degree difference between the 2 sets of data.
The last scan I have for my ABTZ code shows:
Engine Speed = 750
Load = 42
IAC = 44
Spark Advance = 22.9
I have my own scan software, which I trust.
I am not familiar with the EASE software. Do you know if EASE is showing you words 39 & 40 or 41 & 42 of the serial data stream? Words 39 & 40 reflect the timing with respect to TDC which would include the initial 6 degrees. Words 41 & 42 are with respect to the reference pulse, which is the additional timing that the computer adds to the initial 6 degrees. In other words, there is a 6 degree difference between the 2 sets of data.
Intermediate
Joined: Aug 2002
Posts: 35
Likes: 0
From: Iowa City IA
Re: Timing at idle... (scorp508)
OK....
Are you asking if the 32 degrees of advance are normal? If your advance table is the same as my ABTZ code then at 1000 RPM and a Load of 48, the table shows 32 degrees. The ECM is supposed to interpolate, but I suspect it comes close to the 32 degrees.
I would suggest changing it to resemble the newer 1989 APYP code. The APYP timing table shows 22.5 degrees at the same RPM and Load.
By the way, this is one of the reasons I have switched to running the APYP code in my 88.
Are you asking if the 32 degrees of advance are normal? If your advance table is the same as my ABTZ code then at 1000 RPM and a Load of 48, the table shows 32 degrees. The ECM is supposed to interpolate, but I suspect it comes close to the 32 degrees.
I would suggest changing it to resemble the newer 1989 APYP code. The APYP timing table shows 22.5 degrees at the same RPM and Load.
By the way, this is one of the reasons I have switched to running the APYP code in my 88.
