dlr944

Just finished installing the ARC 2, ARM 1, new EGO and 3" MAF last weekend. Once the car is warmed up the ideal settings are as follows:
LOW MID HIGH ACCEL
9:30 1:00 8:30 12:30

Unfortunately, during a cold start the car appears to be running to lean and will shut off. However, if you turn the LOW setting up to 10:30 the car will idle fine but once warmed up the car runs to rich at idle (first or last blue light on ARM1). So leaving the LOW setting at 10:30 I tried backing down the MID setting to 12:00 or 12:30. This did not change the rich idle condition but it did cause a stumble or lean condition when rolling on the throttle. So I tried adjusting the HIGH setting down a bit but this also did not change the rich idle.

Using the above setting I must turn up the LOW setting to 10:30 during a cold start and then back it down to 9:30 to avoid a rich idle condition. I still not able to achieve the dithering at idle. Any suggests would be appreciated. Before installing the MAF, I did not have this problem. Do I need an adjustable FPR??

BTW:
I am using the stock FPR and stock turbo (K26-8) with APE Stage II chips. Also I have a dyno time scheduled for March but I am not sure this will solve my idle problem.

Perry 951

Well.. you need to tweak on it a little more. Took me the better part of a month to get mine right. I found if you can get it on the highway at like 55, start tuning there in 4th gear with the High setting. Then Mid when you slow down on an off ramp. And the low when you leave the light. Pretty much the reverse of what Split Second says. I nailed mine right on after that. Perfect dither at warm idle. If you have not done so, replace the O2 sensor with the 4 wire that is sold as part of the kit. This helps since the ARC-2 was designed using that particular sensor.

As for the cold / warm settings.. I asked this a while ago and got no response. When cold, I needed to up the high setting 1 click as to not lean out.. and to achieve a decent idle. After a mile or so, I'd need to click it back because it was rich. Since I have the ARC-2 in the glove box, it becomes a pain to click this and click that every day when it was supposed to have temperature compensation.

Anyone? Bueller?

rage2

You need to have a really rich mixture on cold starts. When I first got SDS installed, I had my engine down to -20C and spent 1/2 a day tweaking my cold start fuel enrichment. The car will not start at all on a "warm" curve. From -20C to about 20C I had to add enrichment to get a stable idle during an engine warmup phase from -20C to 55C.

The factory programming obviously had this since my car started perfectly stock, the ARC2 should not matter in this scenario as it modifies the stock fuel curve (i think?)

There's a decent sized window for AFR during idle. Too lean or too rich, and the engine will stall.

Perry 951

Since the stock chips (or aftermarket) have temp correction.. this is why I cannot figure it out. It was the same running the MAF off the J boot and with the Stage 3 Piping. I don't think that the placement of the sensor could cause this.. although velocity over the hotwire at idle is minimal. Still.. there are several of us running Huntley and SFR MAF kits, so why isn't everyone having this issue?

rage2

A lot of people don't drive their cars in winter, so they never experience the problem. The enrichment at 15C (summer temps) is so minimal that the difference is just a rough idle, not a stall.

Perry 951

<img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" /> Hey.. it's cold out.. someone with a MAF equipped 951 please head out and go for a little drive and report back!

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

dlr944

Thanks Perry & Rage for the comments.

Perry, are you still having to adjust the ARC 2 on cold start ups? Or did you solve this problem once you finally tuned the ARC 2?

Thanks
dlr944

Perry 951

Well.. I can turn the ***** all I want, but the damn thing won't run. I had a fire a few months back......

However, before that, I almost always needed to give a click every morning.

David Salama

I've been tweaking my ARC II settings for the last year. I really believe this adds to the fun of ownership. How many other cars out their can make a couple of adjustments in the car and drastically change their power output or idle.

As you may recall, I was having problems with a rich idle after installing my 55# Siemens injectors. My ARC II settings were 10:30,2:30,8:30,12:30. With prolonged idling, I would get white unburnt fuel smoke out the tailpipe. I tried changing to a 4 wire o2 sensor, and replaced my plugs, but no help.

Well I finally figured it out. By turning down my ARC II low setting to 9:30, and opening up my idle adjustment screw on top of the throttle body, I am able to stop the white smoke. The O2 sensor will dither stoich regardless of white smoke or not. The O2 sensor exposed to unburnt fuel will falsly think the mixture is lean, and signal the injectors to make the mixture even more rich, which creates a viscious cycle. Once the viscious cycle starts, the only way to stop the smoke is to drive aggressively for a minute and burn the fuel. I am able to close down my idle screw for a few seconds, and see white smoke start, then open it up about 1/2 turn to see it disappear. All the while, the ARM1 dithers! My final ARCII settings are 9:30,2:30,9:00,1:30 with a fuel pressure of 36-38 psi w/o vacuum. I do not need to further adjust my low setting when cold vs hot.

Good luck! <img src="graemlins/jumper.gif" border="0" alt="[jumper]" /> <img src="graemlins/jumper.gif" border="0" alt="[jumper]" /> <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />

951and944S

Hey guys, to add to the adjustments from cold to warm,I seem to have an intermittant problem, present more thna not though.

When blipping the throttle or between shifts, my revs seem to come back to idle too slowly.
Sometimes the revs stop falling at 1500-2000, then if not touching the throttle, they will fall back normal, to 900rpms within a few seconds.

This unpredictability, causes shifting issues around town, as you never know where the revs will fall to. Sounds like a vacuum leak, to me, but damned if I can find one, the car runs great otherwise and pulls extremely hard.

Anybody else have this problem..?

ARC,ARM,SFR MAF,SFR stg 1 turbo, HR chips.

Perry 951

Mine did the same. The idle control valve was sticking. Try and shoot some WD=4- in either of the hoses that run to it. It helped mine. (I also thought of a vac leak, so if this does not help, I'd start looking a little harder. May want to remove the intake)

David Salama

Are you sure your throttle position sensor is properly positioned. With the car off, you should be able to hear the click as you pull up on the throttle cable slightly, and it should click again going back down. Also, try puting some silicone (dielectric) grease into the connector for the TPS. Good luck.
<img src="graemlins/jumper.gif" border="0" alt="[jumper]" /> <img src="graemlins/jumper.gif" border="0" alt="[jumper]" /> <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />

rage2

While reading the Lindsey Racing website tonite, I stumbled upon something :

[quote]A very unique feature about Lindsey MAF's is our VAT inlet air temp sensor along with the hot wire sensor. The air temp sensor in the factory vane air meter is key to the start up and warm up stages of the engine. In addition, knowing the inlet air temperature, the computer adjusts fuel mixture and timing for correct engine performance in all conditions. The factory put one in the inlet airstream on the original air flow meter for good reason and so did we!

If the competition claims they have this capability, just ask them one thing. How many wires are coming from your meters sensor? Only the 6 wire Ford sensor has inlet air temperature sensing capability. Unfortunatly, that technology has not yet made inroads into the aftermarket world of the Porsches. So how do you tell if a system has 6 wire technology? Simply count the wires coming from the sensor. So what's this all mean. If you don't have 6 wire technology, and we don't either, you need a independant VAT sensor, and WE DO have that! Call us if you need more information or explanation.

Only Lindsey racing's MAF kit provides you this accuracy, plus the ability to fine-tune your air-fuel mixture with our MAC II Mass Air Controller.

Some companies MAF systems program nominal default values for the temp settings into their software, but the engine only runs correctly when the engine is at this operating temperature, not necessarily during start-up and warm-up. Others tap into the engine's water temp sensor, this temperature value too does not give the computer the correct signal plus this method is also not as responsive as with inlet air temperature sensing. As the engines water temperature fluctuates, so does your mixture and timing.<hr></blockquote>

This sounds like what you're experiencing with the rough cold idle, the temperature signal the DME is using is from water temp, not inlet temp.

951and944S

Thanks guys, I did check for TPS, as Tim recommended, and I don't have any vacuum leaks, so I'll check for the idle valve later.

Rage, I remember reading that when choosing a MAF, but since I'm in Louisiana, the temp is pretty constant here, and at sea level also, as a matter of fact Fat City is actually BELOW sea level, LOL....
Can the VAT be incorporated separately...?

Also, because I had intercoler pipes and stainless inlet pipe fabbed before my turbo upgrade, my inlet pipe is 2-1/2 ID (as opposed to 3" turbo inlet) and steps up to the turbo via a purocil adapter.
Question: Would the smaller inlet pipe's increased air velocity be misinterpreted as mass..? It seems that the increased velocity passing the "hotwire" would falsly report inlet air...
This make any sense....?

dlr944

Rage 2:

You mentioned that DME is using an input from water temp, not inlet temp. The 944 manual shows #22 DME terminal connected to the factory temp sensor in the original AFM.

The ARC 2 uses this terminal to connect a (grey) wire to the ECU Temperature Input (green) wire on DME harness terminal #22. This takes the place of the factory ECU Temperature Input. My quess is that the hot wire does not provide the proper resistance during a cold start (enrichment).

Any suggestions??

Thanks
David