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Idle Tuning Using Hptuners


Krambo
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On 11/28/2008 at 9:59 PM, Krambo said:

 

Yes sir, I intentionally left that out as from what I am gathering, some tuners like to drill a hole and others say if it idles fine in all conditions and the IAC can meet the required flow for idle control, why mess with hardware. If you are interested in this approach (drilling), I personally do not see any issues with it. Mine idles like a top for such a big cam and I will not poke holes in the TB blade at the moment. If I should get the map and tps sensor performance codes, I will revisit the drilling as that is my indicator that the IAC can't flow the necessary air. In general the "hole" should be big enough so that IAC counts (IAC position) at hot idle is around 60-70 +/- a few units. Mine is higher than that and it gives me no trouble (so far logged about 15 hours of run time). If you wish to drill your throttle body, I would quote this approach rather than "wing it":

 

First your drill bit size:

(drill bit size in inches) converted into mm, that answer squared, then times "pi" yields roughly the mm2 size of a circle (the hole to be drilled). Here is a table to take the guess work out of it:

 

Bit Size in Inches.........change in mm

1/64.......................... 0.5

1/32.......................... 2.0

3/64.......................... 4.5

1/16...........................7.9

5/64 ..........................12.4

3/32...........................17.8

7/64 ..........................24.2

1/8.............................31.7

9/64...........................40.1

5/32.......................... 49.5

11/64.........................59.9

3/16...........................71.3

13/64.........................83.6

7/32...........................97.0

15/64.........................111.3

1/4.............................126.7

17/64.........................143.0

9/32...........................160.3

19/64.........................178.6

5/16...........................197.9

21/64.........................218.2

11/32.........................239.5

23/64.........................261.8

3/8............................285.0

25/64.........................309.3

13/32.........................334.5

27/64.........................360.7

7/16...........................387.9

29/64.........................416.2

15/32.........................445.3

31/64.........................475.5

 

Now, pull up your idle log you ran with the configuration I attached as a download link in post #1. See what your IAC was at hot idle. Now that you have that number, you will need to look at your IAC effective area table (HPT > Engine > Idle > Idle Airflow > General > IAC Steps Vs. Effective Area). Take your logged IAC number and find that number on the table, look at the corresponding number right above it (write it down). Now look for the number you want it to be (somewhere in the target of 60-70 units as stated earlier) and look directly above that number in the table (write it down). Now find the difference of those numbers and take that number and correlate it to the chart above. Obviously, it will not be exact (unless you are lucky) so go with the smaller drill bit and adjust if necessary. Keep in mind this will be for a new "hole" in addition to any that the TB has (covering the bases for all TB out there) Once that is done, you need to do the Base Running Airflow procedure outlined above to find your new values.

 

Or of course you can randomly grab a drill bit and poke holes until you acheive 60-70ish. :uhoh:

 

Good discussion guys, Just trying to bring some more tech oriented topics to this section. Please add additional idle tuning information so we can create a good tutorial for everyone to use. :cheers:

B

Worst advice I have ever read 

On 11/28/2008 at 9:59 PM, Krambo said:

 

Yes sir, I intentionally left that out as from what I am gathering, some tuners like to drill a hole and others say if it idles fine in all conditions and the IAC can meet the required flow for idle control, why mess with hardware. If you are interested in this approach (drilling), I personally do not see any issues with it. Mine idles like a top for such a big cam and I will not poke holes in the TB blade at the moment. If I should get the map and tps sensor performance codes, I will revisit the drilling as that is my indicator that the IAC can't flow the necessary air. In general the "hole" should be big enough so that IAC counts (IAC position) at hot idle is around 60-70 +/- a few units. Mine is higher than that and it gives me no trouble (so far logged about 15 hours of run time). If you wish to drill your throttle body, I would quote this approach rather than "wing it":

 

First your drill bit size:

(drill bit size in inches) converted into mm, that answer squared, then times "pi" yields roughly the mm2 size of a circle (the hole to be drilled). Here is a table to take the guess work out of it:

 

Bit Size in Inches.........change in mm

1/64.......................... 0.5

1/32.......................... 2.0

3/64.......................... 4.5

1/16...........................7.9

5/64 ..........................12.4

3/32...........................17.8

7/64 ..........................24.2

1/8.............................31.7

9/64...........................40.1

5/32.......................... 49.5

11/64.........................59.9

3/16...........................71.3

13/64.........................83.6

7/32...........................97.0

15/64.........................111.3

1/4.............................126.7

17/64.........................143.0

9/32...........................160.3

19/64.........................178.6

5/16...........................197.9

21/64.........................218.2

11/32.........................239.5

23/64.........................261.8

3/8............................285.0

25/64.........................309.3

13/32.........................334.5

27/64.........................360.7

7/16...........................387.9

29/64.........................416.2

15/32.........................445.3

31/64.........................475.5

 

Now, pull up your idle log you ran with the configuration I attached as a download link in post #1. See what your IAC was at hot idle. Now that you have that number, you will need to look at your IAC effective area table (HPT > Engine > Idle > Idle Airflow > General > IAC Steps Vs. Effective Area). Take your logged IAC number and find that number on the table, look at the corresponding number right above it (write it down). Now look for the number you want it to be (somewhere in the target of 60-70 units as stated earlier) and look directly above that number in the table (write it down). Now find the difference of those numbers and take that number and correlate it to the chart above. Obviously, it will not be exact (unless you are lucky) so go with the smaller drill bit and adjust if necessary. Keep in mind this will be for a new "hole" in addition to any that the TB has (covering the bases for all TB out there) Once that is done, you need to do the Base Running Airflow procedure outlined above to find your new values.

 

Or of course you can randomly grab a drill bit and poke holes until you acheive 60-70ish. :uhoh:

 

Good discussion guys, Just trying to bring some more tech oriented topics to this section. Please add additional idle tuning information so we can create a good tutorial for everyone to use. :cheers:

 

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