one of Grumpy's posts, min air rate, idle speed,
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one of Grumpy's posts, min air rate, idle speed,
https://www.thirdgen.org/forums/diy-...r-min-tps.html
I found this thread and I think that Grumpy was talking about about drilling small holes in the butterflies on the TBI unit. Can anyone shed some light on this???
I found this post after searching TGO for setting min air rate on TBIs.
I understand the procedure for closing the IAC and adjusting min air rate. And I know that the idle is controlled by the ECM and usually doesn't require adjusting the min air rate screw.
That said, I have read many inconsistencies as to the proper setting of the idle speed itself using the minimum air rate screw. ... I have read to set the idle speed at what the commanded idle speed is in the chip, and I have ALSO read that you should set the idle speed about 125RPM less than what the chip commands. Which is it????
Another thing I'm left wondering is what exactly my idle speed should be set to given my combination of stuff. My stock combo used the ASDU9567 bin (350/auto). The thing is I no longer have an automatic, I swapped to a T56... And, I have some minor modifications like a 2030 cam, p&p heads, yada yada. As far as I understand it, stick shifts should idle slightly faster than their automatic counterparts, and also, the more cam, the faster the engine likes to idle.
I found this thread and I think that Grumpy was talking about about drilling small holes in the butterflies on the TBI unit. Can anyone shed some light on this???
I found this post after searching TGO for setting min air rate on TBIs.
I understand the procedure for closing the IAC and adjusting min air rate. And I know that the idle is controlled by the ECM and usually doesn't require adjusting the min air rate screw.
That said, I have read many inconsistencies as to the proper setting of the idle speed itself using the minimum air rate screw. ... I have read to set the idle speed at what the commanded idle speed is in the chip, and I have ALSO read that you should set the idle speed about 125RPM less than what the chip commands. Which is it????
Another thing I'm left wondering is what exactly my idle speed should be set to given my combination of stuff. My stock combo used the ASDU9567 bin (350/auto). The thing is I no longer have an automatic, I swapped to a T56... And, I have some minor modifications like a 2030 cam, p&p heads, yada yada. As far as I understand it, stick shifts should idle slightly faster than their automatic counterparts, and also, the more cam, the faster the engine likes to idle.
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Re: one of Grumpy's posts, min air rate, idle speed,
What Grumpy was posting about is the turbo Buick engine. In which the TPS setting is critical for that ECM. It is also a MPFI set up. Same as the '89 TTA.
For a TBI set up best to have the IAC steps at 5 - 10. On a warm engine and no additional loads. This is what Pablo is referring to.
For idle speed, can bump it up a bit. What ever makes the engine happy.
RBob.
For a TBI set up best to have the IAC steps at 5 - 10. On a warm engine and no additional loads. This is what Pablo is referring to.
For idle speed, can bump it up a bit. What ever makes the engine happy.
RBob.
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Re: one of Grumpy's posts, min air rate, idle speed,
He was talking about a cross fire system with no hac in 2000...Pablo was talking about a turbo buick... so I don't think anything there applies to your engine today...
What are your IAC counts and TPS reading at idle?
If you do the procedure correctly it should be 100 rpm below idle RPM in chip, then when reattaching IAC to control idle and get IAC counts... I like 10 to 20.
If you now have a manual trans then start with a manual chip. There are many differnces, not just idle. Your not going to get idle higher than chip by doing this procedure correctly, ECM will always try to go to programmed RPM. The procedure is rarly needed unless the TBI unit was rebuilt or it is going on a conversion engine or modified engine. Or if there is so much wear that throttle blades are stuck shut on bores at idle...
What are your IAC counts and TPS reading at idle?
If you do the procedure correctly it should be 100 rpm below idle RPM in chip, then when reattaching IAC to control idle and get IAC counts... I like 10 to 20.
If you now have a manual trans then start with a manual chip. There are many differnces, not just idle. Your not going to get idle higher than chip by doing this procedure correctly, ECM will always try to go to programmed RPM. The procedure is rarly needed unless the TBI unit was rebuilt or it is going on a conversion engine or modified engine. Or if there is so much wear that throttle blades are stuck shut on bores at idle...
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Re: one of Grumpy's posts, min air rate, idle speed,
Ahh I see.
So you do set the idle 100rpm lower than what the chip commands... Okay.
I've taken your advice EagleMark and I've started with a new bin, asdw9544 which is a 350/MT combo instead of 350/AT.
I know that the ECM commands the idle reggardles of where that screw is at, I burn my own chips so I have been tinkering around with different idle speeds in the target idle speed vs coolant temp lookup table. I was just trying to establish the proper relationship between that lookup table in the ECM and the screw for min air rate....
So you do set the idle 100rpm lower than what the chip commands... Okay.
I've taken your advice EagleMark and I've started with a new bin, asdw9544 which is a 350/MT combo instead of 350/AT.
I know that the ECM commands the idle reggardles of where that screw is at, I burn my own chips so I have been tinkering around with different idle speeds in the target idle speed vs coolant temp lookup table. I was just trying to establish the proper relationship between that lookup table in the ECM and the screw for min air rate....
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Re: one of Grumpy's posts, min air rate, idle speed,
You'll be way happier tuning a manual bin to start than an auto bin, there's only a bazillion differences in IAC logic etc... between the 2.
Now if you change idle, in my $42 xdf it is "IAC - Desired C/L Idle Speed" then you would want to be totally warmed up and do min air setup about 100 rpm below what you set. That gives IAC enough room to cover controlling idle. Since you have a cam you may want a little more base timing at distributor but remember to add that in Initial Base timing in bin.
I have a lot of work into $42 XDF and ADX for TunerPro including data tracing important parts and you are welcome to use them.
http://www.gearhead-efi.com/Fuel-Inj...Information-42
Now if you change idle, in my $42 xdf it is "IAC - Desired C/L Idle Speed" then you would want to be totally warmed up and do min air setup about 100 rpm below what you set. That gives IAC enough room to cover controlling idle. Since you have a cam you may want a little more base timing at distributor but remember to add that in Initial Base timing in bin.
I have a lot of work into $42 XDF and ADX for TunerPro including data tracing important parts and you are welcome to use them.
http://www.gearhead-efi.com/Fuel-Inj...Information-42
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Re: one of Grumpy's posts, min air rate, idle speed,
Ahh I see.
So you do set the idle 100rpm lower than what the chip commands... Okay.
I've taken your advice EagleMark and I've started with a new bin, asdw9544 which is a 350/MT combo instead of 350/AT.
I know that the ECM commands the idle reggardles of where that screw is at, I burn my own chips so I have been tinkering around with different idle speeds in the target idle speed vs coolant temp lookup table. I was just trying to establish the proper relationship between that lookup table in the ECM and the screw for min air rate....
So you do set the idle 100rpm lower than what the chip commands... Okay.
I've taken your advice EagleMark and I've started with a new bin, asdw9544 which is a 350/MT combo instead of 350/AT.
I know that the ECM commands the idle reggardles of where that screw is at, I burn my own chips so I have been tinkering around with different idle speeds in the target idle speed vs coolant temp lookup table. I was just trying to establish the proper relationship between that lookup table in the ECM and the screw for min air rate....
Hit the Tuning Guide Book stickys up top of this forum. Chapter 5, '8063/'7747/'8746 ECM, IAC Logic thread.
RBob.
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Re: one of Grumpy's posts, min air rate, idle speed,
We are talking of 2 differant ways to set IAC counts.
From the tech tips page is way I am describing. Doing it this way there is no way to get 5-10 IAC counts. Unless luck is a factor?
But if you did not do it the way described in Tech Tips section and left IAC plugged in you could adjust throttle blades to get an IAC count of whatever you want. If you set it to low like 5 counts in summer you will have no counts and higher then programmed idle in winter.
From Tuning Guide IAC logic. The way RBob is explaining.
If you set it to low like 5 counts in summer you will have no counts and higher then programmed idle in winter. Which is why I shoot for 10 to 20 and have IAC counts all year long.
From the tech tips page is way I am describing. Doing it this way there is no way to get 5-10 IAC counts. Unless luck is a factor?
Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.
Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.
Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.
Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).
Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.
Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.
Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).
From Tuning Guide IAC logic. The way RBob is explaining.
MECHANICAL EFFECTS:
(I want to thank Bruce Plecan for discovering and documenting this gem).
With a TBI system, the IAC steps at idle can be crucial. Again, I am
referring to the hot'r street type engines. A rumpity-rump engine needs all the help it can get to idle. One area to be addressed is that of the throttle blade setting.
A typical TBI system will idle with an IAC count of 35 to 45. On a cam'd engine, zero steps may be better. Myself, I shoot for three to five steps with a warm engine, and no A/C. The reason for this has to do with the injectors residing above the throttle plates.
During idle, the TBI injectors are designed to spray onto the bore walls.
When this happens, the fuel runs down the walls, and past the throttle blades. The air speed past the throttle blades is very high. This action shears the fuel into vapor that is then able to travel to the chambers.
If the engine idles with a high IAC count, this IAC air is bypassing
the throttle blades, hindering the flow of fuel into the plenum. By
opening the throttle blades and reducing the IAC counts, there is a greater volume of air drawing fuel past the throttle blades
(I want to thank Bruce Plecan for discovering and documenting this gem).
With a TBI system, the IAC steps at idle can be crucial. Again, I am
referring to the hot'r street type engines. A rumpity-rump engine needs all the help it can get to idle. One area to be addressed is that of the throttle blade setting.
A typical TBI system will idle with an IAC count of 35 to 45. On a cam'd engine, zero steps may be better. Myself, I shoot for three to five steps with a warm engine, and no A/C. The reason for this has to do with the injectors residing above the throttle plates.
During idle, the TBI injectors are designed to spray onto the bore walls.
When this happens, the fuel runs down the walls, and past the throttle blades. The air speed past the throttle blades is very high. This action shears the fuel into vapor that is then able to travel to the chambers.
If the engine idles with a high IAC count, this IAC air is bypassing
the throttle blades, hindering the flow of fuel into the plenum. By
opening the throttle blades and reducing the IAC counts, there is a greater volume of air drawing fuel past the throttle blades
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Re: one of Grumpy's posts, min air rate, idle speed,
EagleMark, yeah it seems as if starting with a manual based bin is going to be a better deal.
Where did you find the time to create that definition file.... I have been using the plane jane
$42 mask and it doesn't have anything compared to yours. I wish I would have found your mask sooner..
The notes you added for each parameter is very helpful as well, I've been trying to study up on that.
Yeah since I have a moderate cam I have been running just a hair under 5 degrees initial spark advance, seems to work well.
And I do have the initial spark advance in the chip set to reflect this static timing.
I stand corrected. I backed the screw off just a tad now have 7 steps at the commanded idle speed, with no engine load, fully warmed up. All seems well.
Where did you find the time to create that definition file.... I have been using the plane jane
$42 mask and it doesn't have anything compared to yours. I wish I would have found your mask sooner..
The notes you added for each parameter is very helpful as well, I've been trying to study up on that.
Yeah since I have a moderate cam I have been running just a hair under 5 degrees initial spark advance, seems to work well.
And I do have the initial spark advance in the chip set to reflect this static timing.
I stand corrected. I backed the screw off just a tad now have 7 steps at the commanded idle speed, with no engine load, fully warmed up. All seems well.
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Re: one of Grumpy's posts, min air rate, idle speed,
So are we saying that either method will get you there??? I did it the first way I described (unplugging the IAC) and the idle speed seemed okay, plugged in scantool (WinALDL) and the counts were anywhere from 0-5....
Using RBob's method posted above, (and with everything plugged back in of course), I adjusted the screw until I got 7 counts at idle....
How does that old adage go? There's always more than one way to skin a cat??
Using RBob's method posted above, (and with everything plugged back in of course), I adjusted the screw until I got 7 counts at idle....
How does that old adage go? There's always more than one way to skin a cat??
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Re: one of Grumpy's posts, min air rate, idle speed,
Yes but doing it with IAC plugged in you need to turn off motor.... wait.... start and reconfirm. It goes into detail if you read the IAC logic thread RBob posted why.
I haven't read that in years...
The $42 adx is mine but the $42 mask/XDF is not all my work! I actually don't know how to dissamble and there were no authors in any of them? I don't like taking credit for someone elses work.
But I did take 4 $42 masks and combined them all including comments from all and comments from Dissasemblies, orginized them and set up things like main Spark and Main VE and etc and have them set for data tracing as well.
You need to use the ADX and XDF together and while data recording click the data trace button and you can see exactly where in fuel or spark the engine is running in the bin. Works on your old logs to. Finds an exact spark cell when you are looking for knock or?
I haven't read that in years...
The $42 adx is mine but the $42 mask/XDF is not all my work! I actually don't know how to dissamble and there were no authors in any of them? I don't like taking credit for someone elses work.
But I did take 4 $42 masks and combined them all including comments from all and comments from Dissasemblies, orginized them and set up things like main Spark and Main VE and etc and have them set for data tracing as well.
You need to use the ADX and XDF together and while data recording click the data trace button and you can see exactly where in fuel or spark the engine is running in the bin. Works on your old logs to. Finds an exact spark cell when you are looking for knock or?
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