944JM

I've got the SMT6 and the MAF upgrade. Right now it's been a problem to tune. The biggest problem was ambient temp change causing it to go lean as the ambient temp went up. I've discussed this with Fracolli already. Right now I've just backed the whole system out. Since I've done that, an apparent vacuum leak slowly crept in. After going crazy to find it including pulling the intake and resealing, I found that a new A/F ratio gauge had gone south and was corrupting the signal to the DME. Being new and having worked for 3 month previously we never suspected it. Autometer said it shouldn't happen but it did. Not to bad mouth their meters though as I've always had good luck with them. Now I replaced the gauge and the car runs fine. I just use the gauge to indicate a problem not as a tuning device. Symptoms were rough idle and hesitant stuttering until about 3/4 throttle. It would run but you really didn't feel comfortable doing it.

Geo

An MAF should not appreciably change the mixture with ambient temp. This is another advantage of an MAF. Something sounds funny here.

david fracolli

Actually I have the same problem with my MAF and the Arc2. The system works fine at temps above 40 degrees. Yesterday though it was -10 when i drove it in the morning and i had to back off the low setting 2 clicks to get it to run. This is not the 1st time this has happened either. I have had it set perfectly in the afternoon when the temp was in the low 40's only to have to readjust the ARC2 at night, when the temps are in the low 20's, to get to run corectly.
At this time i am seriously thinking of getting rid of the system as I am tired of having to adj the ARC2 2-3 times ever day.

Geo

There must be an issue with the software in the ARC2. Is that a piggyback or is it a stand-alone?

A hot-wire MAF adjusts the voltage to the wire to maintain a constant temp. By measuring the voltage to the hot wire, it's a relatively simple calculation (well not for me, but for the engineers) to determine air mass being ingested. Ambient air temp should not play a role at all. I wonder if there is a separate ambient air temp sensor in use that is screwing with what should be something simple.

All airflow metering systems try to measure air mass as this is the important thing in determining the amount of fuel to mix with the air. MAP and other sensors require an air temp reading to calculate the air mass using volume and temperature and sometimes other measurements (I think).

A MAF with good software should be good for virtually all operating temps.

I just thought of something else. The other thing that could cause you to go lean is if you are exceeding the voltage the MAF is calibrated for. On the Nissan SR20 engines with big turbos, we have to go to the Cobra MAF becuase While the factory MAF will accomodate about a 50% increase in power, most of the turbo engines are running 100%+ increases.

david fracolli

The arc2 is a piggy back system so there in no programming.

Matt H

The problem you are having is that the MAFs do not have a temp sensor. You can use the one from the original AFM. This has been discussed ad naseum on the Turbo boards. Searc for it and you will be busy for a year.

George I think the TB setup from JME is a tad over 4K dollars, YIKESSSSS. We can talk about it later this month, dont forget I will be staying with you! TonyG and I (as well as a number of others), have been talking about converting to solid lifter and bill cam housings, etc. Looks like about 1500 each if we had 5 others. So far no luck getting more folks (maybe because it appeared it was going to cost 5K).

The problem is as you mentioned, no one is willing to drop that kind of cash on the NA's. I need to go visit Don, does anyone know where his shop is located? I know it is here in the DFW area.
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Geo

OK. This makes me wonder about several other things.

Are you telling me DME for your car is programmed for a MAF?

Does the DME have a self-learning routine? On the Nissans, piggybacks don't work worth a damned because the ECU's self-learning routine and the piggyback are always fighting each other, resulting in driveability issues.

I still think it's a software issue. What exactly does the ARC2 do?

Matt H

It IS is signal massager and not a piggy back. You are modifing the incoming data, essentially converting it from AFM to MAF signal without changing the DME. It really helps to have aftermarket chips tuned for the MAF though.

see
www.splitsec.com

From Split Second

The ARC2 (Air/fuel Ratio Calibrator) provides additional features over the ARC1. These features make it possible to fit a MAF sensor to engines that were designed to operate with vane type air flow meters. It is especially useful for re-calibration of modified engines that have ECU (Engine Control Units) designed for MAP or MAF (Mass Air Flow) sensors, also compatible with GM and Karman Vortex applications. In addition to the low and high load adjustments of the ARC1, the ARC2 also provides adjustments for mid load and acceleration boost.


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Geo

OK, now I'm convinced it's a software issue. Doesn't the DME use an ambient air temp signal? In any event, I don't believe the whole package is operating as a MAF with a proper ECU would.

No offense to anyone, but IMHO piggybacks are just kluged together systems. Yes, some people get decent results from them, but usually hear about people having to constantly putz with them, not unlike this specific case.

Geo

I missed this before my last reply.

I'm not sure if I'm reading this wrong, but yes, you are correct, a MAF does not have a air temp sensor. It doesn't need one. Doesn't care. I think the AFM does have one and this would likely be the problem. The ARC2 is sending a signal based upon air mass, but the DME is making adjustments for temp, something the MAF doesn't need.

Door's always open and you and your wife are always welcome.

He's just west of downtown Ft. Worth. He wanted to help me with my race car (read sponsorship), but it's taken a while to get the damned thing built. Once I get the cage in, I'm going to stop in to see him and talk with him a bit. Since we're pulling the engine, I'll probably want to have him do a few things for me.

Matt H

We can stop by there when you guys are here for the Parade.

The temp sensor is the issue. By using the one from the stock DME the ARC2 becomes very reliable and you dont constantly have to fiddle with it. Remember the ARC2 is just a massager. Loads of info on this, search the turbo board.

Thanks!!

As for the software if you are running the MAF without custom chips I dont know how it would work, I have not hooked mine up yet. I would suppose it works but you are probably not seeing all the benefit from it.
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Lousailor

Speaking of intake manifolds, I've seen several of the shops offering custom versions for turbos, but don't know how they'd work with a non-inducted system. Has anyone tried using a stock turbo manifold on an NA? I kind of like the angle it comes in at, less bends and with a CAI may be close to straightline from a cone filter through the TB.

Matt H

I think the ports would be wrong to use the Turbo manifold and you would have to rig the intake. Might could be done but I have never seen it.
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Geo

OK. I hope to have my car done before Parade. I'll probably come up there as soon as my cage is welded up.

I agree that the temp sensor is the issue. While I don't have direct experience with the ARC2, I suspect the temp sensor is causing the changes in mixture. Remember, a true MAF system does not use a temp sensor and does not need one (other than for some late model emissions stuff). The MAF does not need a temp sensor to measure air mass. I suspect the temp sensor is causing the DME to screw with the mixture.

Matt H

You have hit the issue on the head. The DME is looking for a temp sensor and their isnt one. Since you have a converted system with a massager it isnt a "true" MAF setup.

When you need to come up you are welcome to stay with us. The house isnt much but we have a spare room, if you dont mind animals. I also have some great rates with some OKAY hotels near my office (which would be much closer to West Ft. Worth). Let me know.
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