tecart

My car: 1986 944 turbo, arc2 arm1 maf#4 kit. Now my mechanic is setting up base idle and adjusting the idle position screw and the throttle stop adjuster screw on the right side of the throttle body(the screw with factory yellow paint on it that stops the throttle), anyhow we want to set rpm at idle at 950 rpm's, and i was wondering what settings to put the ARC2 at for low, mid, high and accel, when setting the car up for this. I am concerned that by adjusting the rpm's to 950 and using/leaving the arc2 settings the way i have them now will throw out/negate the real way to acheive a true idle number. Should we set the ACR2 to the zero adjustments position for this repair? That would mean to turn all the ***** to the 12:00 position and go adjusting the idle from here or adjust the idle with my arc2 settings like they are now(about 4 clicks left and right from 12:00, except high ****, that one is +6 for extra fuel), what do you guys think, put settings to 12:00 or it doesn't matter what settings the arc2 is at for setting base idle? thanks if you know, Huntley, SFR, GURU, AMW...what is proper way to do this if i have a maf kit, not the autothority one

Perry 951

You want to set the ARC-2 first. I started at 12:00 on all of the *****, and needed to richen it up as I went along.

I did not have a dyno, so I had to set it up on the street. I kept it pretty rich until I got to the highway. On the way, in low load situations, I fiddled with the mid setting to keep it a tad rich. I increased load slowly and leaned out the top end with the high settings. Once I was sure to stay a little rich, I fine tuned the mid and low settings as I came off the highway.

Back to your origional question... I would leave the stock settings of the TPC and Idle Screws until you have the A/F nailed down. Once you have that, adjust the idle where you want it. Chances are that changing the ARC-2 could change the idle you have set. I had a low idle after I was done with tuning, and increased idle with the air bleed screw.

tecart

what im trying to say is that i know my base idle settings are off, therefore my car runs ok at idle because im overcompensating for the wrong base idle settings thru my arc2, what im trying to do is get back to the stock idle mixtures and go from there, can i do that by setting the arc2 at the zero position(12:00) on low mid high and accel or do i have to disconnect the arc2 and reconnect the stock afm? Please realize that my low settings are way off from where they shoud be if my base idle was set properly. Because its not, i am over-adjusting my low **** at idle. Now all i wish to do is set the base idle properly so i do not over compensate for idle rpms and overuse the low **** setting. What is the way to make sure you can adjust for base idle and be sure you arc2 is not being overadjusted? What i mean is say i put a maf kit on my car and the idle settings are perfect, but some mechanic 6 months later adjusts my idle screw and throttle stop plate screw by mistake, then the car runs like crap so he then adjusts the low and mid **** on my arc2 to get the car to idle ok, now the car idles ok but the true base idle if off and the overcompensated arc2 will show bad readings when on "cold starts", all because im overcompensating a problem and trying to correct it with the arc2, and now that setting is not "true" either. See what im getting at, so how do I get back to the true base idle without the arc2 sending readings while im trying to get to the stock settings? Once im back to stock, i believe my arc2 will never have to be adjusted on cold starts, but how to do this?

Perry 951

About the only way you can get it back to stock is to set it up in the stock configuration. You would then disable the idle air valve and set the base idle.

Reconnect the MAF and ARC-2, adjust for proper A/F, then go back and tweak the idle with the idle air valve disabled.

tecart

that makes sense perry, but derrick told me a few years back that it was possible to do what i am asking about with the whole kit inplace and hooked up, i just forget the process, did he say put all the arc2 settings to 12:00 or do something with the maf kit harness, i forget and hope someone has done this without having to take it all out and put it back in if you get me...

Perry 951

I hear ya. 12:00 settings are supposed to reflect the stock values. When I set mine up, the stock values would not cut it because of the increased airflow of the MAF. So in a sense, you can't adjust it to the "stock" settings because you have 2 non stock components in the system. (the MAF sensor and the ARC-2).

You can try and disable the idle air valve and reset the idle as best as possible, and work from there, but I would set up the ARC-2 how you want it, with the proper A/F ratio, then go back and reset the idle.

If you do the idle first, then tweak the ARC-2, you will have to go back and reset it again anyway, since the low and accel adjustments can effect the idle speed and quality.

Hope that helps.

guardsred951S

I like Perry's approach: set up the top and then mess with the bottom. That's how it's done with small engines like chainsaws and weed wackers and low throttle is always a pain to adjust. One thing you want to stay away from is a lean condition in the high rev ranges. Beyond that, why can't you just take the car out for a spin on the highway, set up the high/mid throttle and then park it and doodle with the idle until it runs the way you'd like and the throttle response is good?

About setting the idle, my old car had a high idle of 1100 rpm or so. Steady but high. We turned the screw on the top of the intake to the inake manifold <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" /> and we were able to adjust it right to where we wanted (~900 rpm). Do this, then set the idle mixture up for a good steady idle.

I may be oversimplifying this as I don't know the details or the ARC2.....

<img border="0" alt="[bigbye]" title="" src="graemlins/xyxwave.gif" />

Danno

No need to get so complicated. Leave all the ARC2 ***** where you've got them optimized for performance.

Then adjust the LOW **** so that you have quick dithering of an AF-meter. This will mean that you've got the MAF voltage close to a point on the idle fuel-map where the fuel-value matches the airflow you've got. This usually works within a 3-click range on the ARC2's low ****. Your actual idle speed may or may not change with this adjustment. Then it's another small step to re-adjust your idle speed and that should do it.

tecart

is this the same concept for people with a engine mgt. system also? i mean adjust your fuel 1st for proper idle and power, then 2nd reset the base idle and bypass screw, then 3rd readjust your fuel mixtures if step #2 changed anything right?
Is this the right way 100 percent to get the right base idle with a MAF kit, Also less important to me but im wondering what people with a map kit do to adjust base idle also, do they follow the same 3 steps above? thanks for all the info.

jimbo1111

Why was your idle high to begin with? Don't over look vacqume leaks before you start to battle them buy adjusting everything else.

Danno

"Is this the right way 100 percent to get the right base idle with a MAF kit, "

Ok, we should break this down even further. There are two distinct steps here that should be distinguished: (1) adusting idle-air flow and (2) adusting fuel to match that flow.

Adjusting idle-air flow is done through mechanical bypasses. The throttle-plate stop, the bypass screw and the idle-stabilizer. These should be set to factory specs so that the proper CFM is flowing. This must be done first.

Adjusting idle fuel is next and in the stock configuration, the TPS click will select the idle-fuel map on the chips. The AFM voltage will then determine which cell on the map to reference and the proper amount of fuel is dispensed.

With a MAF kit, what you're trying to do with the adjustments is have the MAF-sensor generate a signal that's similar to the stock AFM under the same air-flow conditions. The LOW **** issued to massage low-voltages. However, the MID and even the HIGH **** tends to have overlaps that will change the LOW idle voltage as well.

So what you're trying to do is juggle the four ***** so that your voltage at idle is low enough to match the airflow (indicated by dithering), yet stil keep the voltage at high-flow high enough to select the richer zones on the chip's fuel-map.

What should not done is to use the ARC2's LOW **** to adjust idle speed. By leaning or enriching the mixture enough, you can actually change the idle-speed, but you'll have skewed the look-up point on the idle fuel-map so far off that the O2-sensor feedback can't center it around a 14.7:1 stochi. mixture.

The fuel adjustments for power is completely separate from idle. However, you need a system with fine enough adjustments with enough resolution that changing idle mixtures won't mess up your partial-throttle or high-end mixtures as well and vice versa (imagine an ARC2 with 144 *****.. <img border="0" title="" alt="[Wink]" src="wink.gif" /> ).

"Also less important to me but im wondering what people with a map kit do to adjust base idle also, do they follow the same 3 steps above? "

They just plug it in and that's it! The MAP-sensor is pre-programmed to emulate the AFM's output exactly. So no adjustments or programming is required. Provided that the mechanical parts of your car are within spec such as throttle-body closing position, TPS click, bypass-screw opening, and idle-stabilizer so that the proper amount of air is flowing at idle, the fuel-value pointed to on the chips by the MAP-sensor will be exactly the same spot that would be chosen under stock conditions with the AFM.

DanD

Ok,
Not really having to do with Idle but more with what the Arc II is doing.

Here is a spreadsheet with the data from my last dyno run. I need to tweak the Arc II to smooth out the A/F ratio.

<a href="http://members.rennlist.org/dan10101/dynoairfuel.xls" target="_blank">Excel spreadsheet of Air Fuel Ratio</a>

First, under full throttle (dyno run) do the low and mid do anything at all?

I think I know some of what the setting do. (Low, Mid, High and Accel). But I need a check.

I think the High just moves the A/F up and down the range. Like the Red line in the top graph.

I think the Mid could be used to tune the bottom picture of the actual dyno run. Flattening out the bell as shown by the yellow line.

I don't know how to get the big lean bog at the lower (no boost yet) rpm ranges.

I guess what I'm asking is what do I do to flatten out the A/F ratio.

Note: To get the bottom picture from the top (real lean) maroon graph to the bottom (too lean then too rich) dark blue graph, I turned the high and accel 2 clicks richer each.

Click on the link above to see what I'm talking about.

I may need to reword this, but right now I need to go to bed..

tecart

Thanks Danno for the help, i dont want to overkill this issue but what im saying is my throttle plate screw and throttle bypass screw are way out of spec./stock settings. Therefore we know my cars idle is wrong and the arc2 im using is overcompensating for that. My arc2 settings are off but I keep them to get a good idle. The low **** is not set right like it would be if i were to get the idle set right to begin with. I again am asking how do i set the base idle and be 100 percent sure the arc2 isnt adjusting the rpms, thereby giving my mechanic a false rpm reading. Because he is resetting base idle and using my dash rpm gage to get it to 950 rpm's at idle, the bad settings on my low **** switch are not allowing him to tune the car to a true 950 rpm's. The arc2 needs to somehow be taken out of the loop to get a true setting for resetting base idle speed and i know for a fact the arc2's low **** setting if affecting his ability to get a perfect base idle set, the arc2 is leaning out some fuel at low, and therefore affects idle speed, therefore i want to disable the arc2's ability to change idle speed at all until i get my stock base idle speed set, then i will use the arc2 to change fuel to match performance, do you understand me? Ive never had such a hard time trying to explain something but i will keep trying until it makes sense, im not trying to be a dunce, but i have been told by derrick at HR that if your base idle is set wrong then when you try to get a good idle/and dithering on the arm1, it will be hard to do, you will be trying to overcomensate with your arc2 to get a good idle without going full lean or rich. That in turn will make you have to adjust the arc2 1 or 2 clicks alot when temps. vary at startup, i believe this is true to a degree, also he states that low to mid range performance/ turbo spoolage can be affected if your base idle if off and you use the arc2 to compensate for that. This is an issue for me too with my bigger turbo, i need it to spool up as fast as i can get it to so im just fixing all sources of delay. I know my base idle is wrong, the bypass screw is screwed in almost all the way in and im at 1050 rpm's, i cant get the idle revs any lower unless i use the arc2 and lower the low **** a click or 2, this in turn lowers the idle to 950 but now the arm1 shows full lean on the scale and the car starts to stumble as it needs for fuel for the cold start. Then i have to raise the arc2 **** so i dont die out, my idle climbs to 1050 again and im repeating this over again and again, also once the car warms up, its time to lower the low **** a click to get to the 950 rpms again. I dont have any vaccume leaks or any bad sensors, i just know the problem and the 90% solution, and just need to set the base idle and throttle plate and bypass screws to stock but i have to make sure the arc2 readings do not sent signals while we do this, get me yet? Perry did have a great idea, but i heard this can be done without doing a changeover, i just needed the details, i guess ill have to call HR, i though he said just put all the dials to 12:00 but i forget, sorry for rambling. P.S. a perfect solution is a custom chip but again there is a need to set the right base idle with no devices screwing you up as you reset it like my arc2 does. Post back if you got any ideas

Perry 951

Dan - What injectors are you running? To richen up the lean bottom end, add a few more pounds of fuel pressure. Of course, you'll need to back off the high **** a little, and perahps the mid as well.

Tecart - I messed with my MAF kit for several days trying to tune it as menioned above by Danno and bt Derrik on the other posts. It did not work for me. I had mine tuned in less than an hour by limping it to the highway, setting up the top end (from way rich to perfect), then went home and corrected the idle. After that, I had no mixture issues except for the cold start.

Danno

"im saying is my throttle plate screw and throttle bypass screw are way out of spec./stock settings. Therefore we know my cars idle is wrong and the arc2 im using is overcompensating for that. "

Exactly, we need to get the mechanical parts down first before we try to adjust the electronics. Can't use the electronics to adjust air-fuel mixtures to compensate for a mechanical issue.

"My arc2 settings are off but I keep them to get a good idle. The low **** is not set right like it would be if i were to get the idle set right to begin with. I again am asking how do i set the base idle and be 100 percent sure the arc2 isnt adjusting the rpms, thereby giving my mechanic a false rpm reading. Because he is resetting base idle and using my dash rpm gage to get it to 950 rpm's at idle, the bad settings on my low **** switch are not allowing him to tune the car to a true 950 rpm's. The arc2 needs to somehow be taken out of the loop to get a true setting for resetting base idle speed and i know for a fact the arc2's low **** setting if affecting his ability to get a perfect base idle set,"

Find a new mechanic, heh, heh... Well here's the problem. You cannot just set the ARC2 LOW **** to zero and assume that it's putting out the same signal as a stock AFM at idle because the MAF sensor has a completely different voltage-reponse curve than the AFM. Best way, then is to measure the output air-flow signal going into the DME (pin#7 green/red-stripe). It should be about 0.79-0.85 volts at a 950rpm idle. Add/remove about 0.10v for each 100rpm above and below. Notice and mark which LOW **** setting corresponds to this output voltage. This is your real 'zero' position.

Keep the ARC2 there and adjust the mechanical aspects of idle (throttle-plate stop, bypass-screw, idle-stabilizer, leaks, etc.). Refer to your other thread on how to do this as well as a test for vacuum leaks. You need to make sure the mechanical aspects are OK and within spec before you can adjust the electronics.

Also do not use the dash RPM gauge, it can be off by as much as 150rpm depending upon the phase of the moon. Only adjust your idle using a SUN tach or other diagnostic tool.