rage2

[quote]Originally posted by PrerYDoG:
<strong>So what would be the effect of taking an LR MAF Kit and adding an ARC-2 to it? Would this have the ability to better tune the fuel curve over the RPM band, and still allow for cold start issues to be solved?</strong><hr></blockquote>

It depends. If the LR kit enriches only during cold temeratures (where MAF may not be so accurate), then yes, it would be the ideal solution. If the LR kit uses the temp sensor fed into DME#22 green wire, it would double compensate, as Huntley puts it. Depends on how the kit was designed.

[quote]Originally posted by PrerYDoG:
<strong>Knowing that, we would know how adding a temp sensor to other MAF kits with the ARC2 would work.</strong><hr></blockquote>

I checked on the Split Second web site, and the ARC2 only has a temperature output signal, no temperature input signal. You will need *another* piggyback module just to compensate when the MAF isn't accurate (cold starts, etc). I'm guessing LR's MACII has this cold compensation capability built in (just a guess here).

Huntley Racing

As eluded to, the fixed resistence going to term #22 from the ARC2 is only a NOMINAL signal generation. It is not intended as compensation, but rather as a fixed level from which the MAF can do its compensation. We could set it lower or higher and that would only cause slightly different settings on the ARC2. The overall authority of the air temp signal is very, very low. What that means is that full scale the input to term #22 has little effect compared to say the H2O sensor. You can add a temp sensor and 'HELP' the cold start issue but at the expense of hurting the hot running mixtures of the car. Again I asked for those with the 'cold start' issue to collect sme simple data for me to correlate into a pattern. If there is a problem, that is the way to find it. I am not trying to turn my back on this but in fact searching for the solution, but I need your help!

951and944S

drl,

Fair enough, I was once new here as well, and the reason for everyone's visits to the forum, is and should be to learn and share. My appologies are extended to you, if I came off a little harsh.
I only commented on something brought up earlier in the thread, a legitimate point IMO. Any thread is open for posting anyway, and even if my point was received as being a little OT, it still doesn't warrant a negative reply, once again,IMO.
To reitterate, No offense was intended..

To all others involved here, if you read the thread from the beggining (I wish you would), and you had previous experience with me and my personality, so to speak, I don't think you'll find I made any out of place comments. I bought one of the first MAF's SFR sold, so new they were at the time, I actually sent back a SS setup to use my stock AFM, and traded this setup for the hotwire type. As far as "generic" MAF's as I stated earlier, and other post I've seen, questioning the value of these housings with a sensor, I AM aware that they are nothing special. About six months ago I sent a Ford MAF housing and sensor to SFR, to see if they could incorporate the type in their kits, because I have access to them in finite quantities.

Enough said, (I'll ramble too long),
Once again appologies extended to anyone who was offended, and good luck, with the cold start issues.
Or move to La., the air's real warm and dense down here.........

951and944S

Back to the discussion, I think Derek brought up a valid point, about other issues, multiplying the problem.
When high performance mods are made, engine tune and general condition are sometimes put aside.
Then after the parts are installed the upgrade in question, sometimes get unfairly blamed for emphasising a problem that existed the entire time.
What I mean in this case is, the potential, for the DME to make adjustments for temperature conditions, is replaced by a known value, with the ARC, possibly exposing weak or leaking injectors, vacuum leaks and the like.
My own idle problems were, solved so far by replacing the idle air valve (thanks Perry), which must have been stuck, or intermittantly sticking.
On the other hand, I have a less than perfect auxilliary air regulator (same purpose for S model) that leaks vacuum when the connector is in place, but runs OK with the connector disconnected, causing the vacuum leak to stop.
These DME's were way ahead of their time, and they are able to compensate for less than perfect conditions. A freind, who's a GM master tech, (highest level in GM mechanics) stated that Cadillac was the cutting edge as far as American cars in technology. When I gave him an article from Jim Pasha, on the Motronic DME, considering an 87 S incorporates multiple knock sensors among other things found only on S models, he was humbled, by what he thought was cutting edge..!

Cheers

Jon Schepps

Derrek asked for input from MAF owners, so here's mine. I've been using his "stage 3" system for several years. I live in NJ - 30 degree winters and 90 degree summers. NEVER had any cold start issues. In fact, rarely have had any need to touch the ARC2 since it was initially set up, except to experiment with different boost levels.


Jon
'86 951
Turbo Cup Car wannabe

dlr944

[quote]Huntley responded: You can add a temp sensor and 'HELP' the cold start issue but at the expense of hurting the hot running mixtures of the car. <hr></blockquote>

Derrek again thanks for commenting on this thread! So here’s an idea… if we want to help the cold start issue why not add a temp sensor that feeds a resistance between 6.8k ohms (32F) and 2k ohms (72F). This would assist with cold start issues but would not interfere with the hot running mixtures of the car due to the fact the resistance does not go below 2k ohms.

BTW: I’ll send you an email regarding the sample data you asked for. Hopefully others will follow.

951and944S

Out of respect for the flow, of this thread, and posters here who, I respect, I contacted Mark via email, concerning comments directed towards me.

Cheers

tecart

HEY 951and944S i think most of us here including me are using the big 3 maf kits so your statement about generic maf kits isnt anyones concern as far as i have been reading, are you? i use a stage#4 huntley racing maf kit and have had 2 of them, i sent one back 2 years ago because if this issue and the idle dropping thur 800 on fast stops or accels and then pressing in the clutch, this is the 2 big maf issues ive read about in over 200 posts, after i sent the kit back and put my stock meter on the problems didnt exist ever, now i decided to give it another try and bought it again but the same things are happening, now i do know a maf#3 kit with smaller meter and placing the maf meter as far axay from the turbo will totally fix that issue as verified by over 30 people including john anderson and even derrick himself said this, and kindly offered to swap the #4 for a #3 at any time if i couldnt handle this idle falling thru issue but im living with it ok, but the cold start and temp. sensor issue here is a possible 2nd red flag to realize when buying these kits, now if it is a problem let them tell us a corrective way to help lessen the problem or fix it totally, i know i tried to give it more fuel with upgraded chips and bigger fuel pump and fuel regulator and fuel pressure and dme switch, let the 3 tuners please decide if this is a problem and if they will fix it for us under a "hidden recall" i know john and derrick will stand behind this and if not i will pay to get a temp. switch if they offer it too, but please, we are all talking about the huntley and sfr kit i believe and its wiring setup with the #22 dme terminal, lets shut up and let them both explain this solution, im sure they are testing our theory out even now as i type and how to bandaid it? i need to know, the truth is out there...

Huntley Racing

Those that can collect the data I have requested please forward it to dkhajavi@huntleyracing.com Thanks!

H Dog

[quote]
So here's the deal. Remeber the (grey) wire from the ARC 2 that connects to DME terminal #22 ECU TEMPATURE INPUT (green wire). Well the output (grey) wire from the ARC 2 DOES NOT CHANGE WITH THE TEMPERATURE!!!! This output is a fixed resistance!!! So your car now thinks that it is always warm out!! No wonder I was having problems starting my car in cold weather. The original AFM has a temperature sensor built into it. To compensate for the cold air (more density)you need more fuel. My belief is that without this temp sensor your car can not react or add more fuel to compensate during cold start up (ie enrichment).

To fix this problem I plan to add an input Temperature sensor from Bosch.. If your interested in this solution let me know and I'll update you on my search for an equivalent Temp Senor and if this cures the problem. HOPE THIS HELP OTHERS ON THE LIST
<hr></blockquote>

and...

[quote]
We lack fuel enrichment because the ARC 2 inputs a fixed resistance to the ECU. Again this input does not change based on temp - it's designed for the track. If the temp sensor is in your MAF and it produces the same temp. vs resistance (ohms) as the factory sensor then your in luck. However, I am pretty sure it's not there or disconnected, otherwise these kits would plug the MAF temp sensor directly to terminal #22 of the DME and not the ARC 2.
<hr></blockquote>

plus

[quote]
I don't seem to be getting my point across. The grey wire from the ARC 2 is a fixed resistance between 1.5k to 2k ohms. Therefore, the DME thinks that the temperature is roughly 72F. (You can figure out this by looking at the resistance vs temp. of the AFM in the 944 Manual).
Using the grey wire from the ARC 2 is fine if you live in a mild part of the country or use your car for the track. For track cars this is probably the perfered method because you now have one less sensor which could fail.

If you want temperature control, then you need to figure out a way to tap into the MAF assuming it has a temp sensor that's compatible with the DME or add independent temp sensor that connects to the DME. In either of these cases you just remove the grey wire (it's just there to send a fixed resistance to the DME) and connect the new temp senor to DME input. This is of course is my belief.

<hr></blockquote>

and

[quote]
Ooo, oooo, oooo, I'm first to respond. The temp issue is really kind of funny....The reality is that the early Motronic cars like the 944 Turbo do have different mixtures hot/cold because they just do, stock too....Those with no starts or very rough running have other problems which may be made worse with an MAF vs the original AFM.... Reiterating what I have said all along, MAF sensors do not need air temp sensors on these cars.
<hr></blockquote>

and

[quote]
Again the open issue is what is the purpose of the original air temp sensor? What does the DME do based on this input? It’s a basic I/O question. Derrek care to answer this for us?
<hr></blockquote>

and finally

[quote]
When I played with a motronic EEPROM editor a few years back, I remember the fuel map to be a 3D map of load and RPM. Load is a function of airflow and temperature, so with a fixed temerature setting as AKA951 suggests, there would be no temperature correction.

However, to my understanding, MAF measures air mass, meaning the amount of O2 molecules that pass through the wire, so it should be "compensated" for temperature and humidity. So technically speaking, it should NOT need any correction (thus a fixed temperature resistance sent to the DME), and the signal from the MAF sensor can simply be used as a Load signal.

That's all fine and dandy, but VAF to MAF conversion folks (not just 951's) are still experiencing cold start roughness. Another interesting note, is that Ford, Bosch, Hitachi, and many other MAF sensor makers are now integrating inlet temperature into their MAF units as a 6 wire solution, meaning that an inlet temperature is useful for *something*. Maybe the MAF sensors aren't accurate at cold temperatures, and a secondary temp sensor is used for corrections at low temperatures? If that's the case, you can't wire a temperature sensor to DME #22, because once the MAF heats up you will be running rich (DME calculates load from MAF and temperature settings regardless of what the temerature is). If that's the case, the ARC2 will need to modify the DME#22 signal from a temp sensor only at cold temperatures.
<hr></blockquote>

The stock Bosch L-Jetronic fuel injection system uses a barn door flap air meter. This meters the volume of air entering the engine. But combusion works based on mass, not volume, so the system also looks at the air temperature to determine the mass (PV = nRT, the ideal gas law). THIS IS WHY THE BARN DOOR HAS A TEMPERATURE SENSOR.

When you install a MASS airflow sensor, the system knows the MASS. It does this by measuring the current needed to maintain a specific temperature in the wire. If more mass flows across the wire, the system needs more current. If less mass flows, then less current. It automatically compensates for altitude, temperature, humidity, etc. etc. So it doesn't care about the air temperature. So yes, Huntley racing is correct in that you don't need this sensor.

HOWEVER, the L-Jetronic system also needs to know the ENGINE temperature. This is taken from the COOLANT, not the ambient air -- after all, if you've been driving 200 miles on a cold winter day, the ambient air might be -10, but your car is fully warmed.

The L-Jetronic system uses the ENGINE's coolant temperature to determine if the car is under hot or cold start mode. Exactly what the L-Jetronic does with this information, I'm not 100% certain, but it DOES enrich the fuel mixture via a 5th injector when cold.

By the way, the 944 Turbo's Motronic system is indeed L-Jetronic based. The Motronic only adds ignition timing to the mix, and then utilizes these load maps to determine timing, fuel, etc.

By upgrading to a MAF you're getting what Bosch calls an LH-Jetronic system, or L plus Hot wire.

So adding another air temperature sender to your MAF would, by my analysis, be a total waste of time.

But if you could figure out why the DME is no longer getting the message that the engine is cold (i.e. coolant is less than 50 C), then this might correct the problem. Clearly the tuners know about this -- Lindsey says you need another sensor, and Huntley says that you should stop looking at the air/fuel ratio meter -- but no-one has developed a workable solution.

I wonder why not.

I also wonder if people with the Autothority kit have this problem. I doubt it, otherwise they'd be screaming their heads off. To me, then, it appears that the addition of the ARC 2 is the problem (I don't own ANY MAF yet, pending these kind of discussions).

Not knowing how the ARC 2 is wired limits my ability to analyze this, but that's where I'd start looking.

H Dog

I wrote earlier:

[quote]
The L-Jetronic system uses the ENGINE's coolant temperature to determine if the car is under hot or cold start mode. Exactly what the L-Jetronic does with this information, I'm not 100% certain, but it DOES enrich the fuel mixture via a 5th injector when cold.
<hr></blockquote>

I've done more research. The 5th injector is the L-Jetronic's Cold Start Valve. It injects more fuel into the engine when cold, because the fuel condenses on the intake manifold and cylinder walls.

During cold start and warm-up, the engine typically needs 2x - 3x the normal amount of fuel to run, due to this condensation.

and then I said

[quote]
When you install a MASS airflow sensor, the system knows the MASS. It does this by measuring the current needed to maintain a specific temperature in the wire. If more mass flows across the wire, the system needs more current. If less mass flows, then less current. It automatically compensates for altitude, temperature, humidity, etc. etc. So it doesn't care about the air temperature. So yes, Huntley racing is correct in that you don't need this sensor.
<hr></blockquote>

and I also said

[quote]
So adding another air temperature sender to your MAF would, by my analysis, be a total waste of time.

<hr></blockquote>

There are two kinds of MAFs out there: Constant Temperature and Constant Power. Constant Temperature MAFs heat the wire to a constant differential of 100 C. As the air flows across the wire, it cools down, and the ECU increases the voltage at the wire to maintain the differential. Therefore, the MAF MUST KNOW THE OUTSIDE TEMPERATURE to function.

The Constant Power MAF simply applies a constant voltage to the wire and measures the temperature of the wire. The temperature drop is proportional to the mass of the air flowing across it. This type of MAF is less popular since it does not adjust for changes in ambient temperature, among other things.

[quote]
But if you could figure out why the DME is no longer getting the message that the engine is cold (i.e. coolant is less than 50 C), then this might correct the problem. Clearly the tuners know about this -- Lindsey says you need another sensor, and Huntley says that you should stop looking at the air/fuel ratio meter -- but no-one has developed a workable solution.
<hr></blockquote>

The L-Jetronic's Cold Start Valve is controlled by the Thermo-Time Switch. This switch is a mechanical bimetal switch which senses coolant temperature. If the coolant is cold (eg -20 C), it allows the Cold Start Valve to operate for up to 20 seconds. As the coolant warms, the time the Cold Start Valve is allowed to operate is reduced until around 20 C, when it turns off the Thermo-Time Switch.

Also, the L-Jetronic has an Auxiliary Air Valve. This allows air to bypass the throttle at idle, allowing additional air into the engine. This air is needed at cold start-up because of the increased frictional resistance of the cold engine. The Auxiliary Air Valve is a mechanical device, heated upon initial start-up. Once warm, the valve closes, and no more air gets through. However, its temperature is not dependent upon the coolant temperature (some are, actually, being partially submersed in the coolant stream, but the Bosch units appear to be electrically heated, like a toaster).

SO WHAT DOES THE LH-JETRONIC DO FOR COLD START AND WARM-UP OPERATION?

Well, the LH-Jetronic (H = hot wire) does NOT have a Cold Start Valve, nor a Auxiliary Air Valve, nor a Thermo-Time Switch.

Instead, the ECU reads the coolant temperature and determines, from a preset map, whether to enrich the fuel when cold/warm-up.

Furthermore, the ECU also controls the Idle Control Unit (which replaces the Thermo-Time Switch). The Idle Control Unit not only gives additional air at cold start, but also allows for additional air if the load increases at idle (i.e. you turn on your rear defroster and windshield blower, and the LH-Jetronic automatically revs the engine).

Because the MAF keeps the Auxiliary Air Valve intact, I suspect that this functionality should not change with the addition of an MAF. Therfore, cold start and warm-up problems are coming from a lack of additional fuel being injected into the intake manifold.

Therefore, there are a few conclusions:

First, if you have a MAF which operates by Constant Temperature, then it's already sensing the ambient temperature, and you shouldn't try to add one.

Second, if you have a MAF which operates by Constant Power, then it can't react to an additional ambient temperature sensor, and you shouldn't try to add one.

Third, connecting an ambient temperature sensor to the unused sensor input in the L-Jetronic box will probably give very strange results.

Fourth, it is unclear why the addition of an MAF suddenly causes the Cold Start Valve and Thermo-Time Switch to stop working properly. Some of these kits apparently only need a generic chip set to function properly, then add on the ARC-2 controller to give the right amount of fuel. In this case, I guess that these chips only remove the overboost protection, and enrichen the mixture slightly.

Other kits with custom chips for the MAF must not only enrich the mixture appropriately (thus obviating the need for the ARC-2), but also manage the Thermo-Time Switch properly given the new hardware.

Fifth, the LH-Jetronic comes with an ECU which is EXCEPTIONALLY clever compared to the ECU in our cars. Ideally you'd want to retrofit this system into your car, too -- in other words, you're upgrading only half of the air metering system, and forgetting about the brain. Sure, you can either live with somewhat less than optimal results or perhaps not drive your car unless it is warm out, but this solution does not appear fully worked out.

Again, these are my guesses, but until someone can show that these cold drivability problems are really caused by some other factor other than the Cold Start Valve being somehow disabled, my $1500+ stays in my pocket.

Danno

So ah... where is this 5th injector on our L-Jetronic cars that's used for cold-start enrichment?

Naplesguy06

Ok it's been 11 years now and Huntley went the way of the Dodo.Now what is the conclusion to the cold start sensers necessity? Mafs have come a long way and who wants to play with an arc2 when we now have navi, satellite XM and hands free bluetooth. What is the conclusion here to the crucialness of the cold start senser in these mafs

Busjunky

Thanks for bumping a really old thread! I have a arc2 fuel controller and need to know how to install it on my 951. Can anyone help me out please? Split second has not responded to my emails lol.