Having ordered the Turbonetics kit, I've been doing alot of thinking about the whole ECU reflash thing, and it lead to a few questions....

The role and proper functioning of the MAF sensor is critically important with this kit, so with F/I, under what conditions can the MAF run out of resolution? For example, MIA's car has been flawless, but that's in California weather. What about a car that's being run in colder temperatures or higher general atmospheric pressures? Can the combination of F/I and cold, dense air cause the MAF to just plain run out of voltage? If so, what are the possible safeguards to protect the engine.

I know in the stock ECU there are 3 or 4 maps that the ECU can choose from. How does it choose a map? With the T-netics reflash, how many maps are there, and are those maps tuneable to specific geographic regions or driving conditions (or is there a need to do so?)

I guess my biggest concern is the cold days around here. If it's possible to overrun the MAF to the point that the engine is running lean due to limited output voltage, what's the fix?

Or....am I just way off base here and don't understand the system like I should?

 

just pick up an emanage. if you can w/ this kit

 

That is definitely an option. I'm really seeking a little technical advice from the experts on the forum before I start spending more money, especially if it's un-needed. Thanks though.

 

go standalone and get a speed density conversion. maf's are not too great for big boost. im not sure what a decent standalone will run you for the z, but something like the aem ems is under 2grand and can do this.

 

Again, that's great advice if you have the 2K to spend...But it doesn't get me any close to answers to any of my questions. Thanks though.

 

Pretty sure the MAF just reads how much air is entering the combustion chamber to know how much fuel will be needed. EDIT: It can also determine air density...this is how the ECU knows which fuel map to reference. Turbonetics most likely came up with 3 maps. (BTW, there are 3 total fuel maps that the ECU uses ).

 

I dont believe AEM has come out with the EMS for the Z yet. I could be wrong though.

 

Right, I know that the MAF actually reads flow and temperature (so it knows how much air AND how dense it is, the two factors needed to calculate how much oxygen is actually present).

Assuming that the MAF voltage increases when either flow volume increases or temperature decreases (I'm guessing at this operation here), at what flow rate and/or at what temperature does the voltage from the MAF max out? If the Turbonetics system is capable of exceeding the flow rate (at a given temperature) that equals max voltage on the MAF, then a lean condition is going to occur.

Anyone?

 

What do they currently use for fuel management? The emanage clamps it at 5v on the Greddy TT, but if I remember right problems didn't arise until you went close to 9 psi

 

Everything is done via the ECU reflash, so there is still complete reliance upon the MAF to provide accurate data to the ECU. The kit includes the Walbro 255 LPH pump and 44cc injectors, but I don't know that that's relavent for this discussion.

 

The MAF is not really affected tOO much by elevation. More so the amount of pressure seen at the manifold is. Speed Dreams has their car running up in NM and they have not seen the MAF have any probs yet. As for where the MAF "flows out at" Well I don't have the exact parameteres used for tuning on the ECU but from what I gather the MAF has not seen any problems at over 9.5 PSI. This is the biggest single determining factor. Yes the air temp is going to make a difference due to the density of the air. HOWEVER the MAF is not going to care how dense it is. Rather the only concern there really is, is how much air can the MAF see without problems. The actual volume of air being metered should not change significantly by air temp. All three maps in the ECU have been altered to account for the bigger injectors and the turbo. Although I have yet to drive around in 30 degree or lower weather I have driven my car on nights when the ambient temp was in the low 40s.. There have been zero problems with that. I imagine if there was going to be a problem with this the ATI guys in NC who have the reflash controlling their cars would have found this. I honestly don't think you are going to have a problem here. My car and the Turbonetics car have both seen 10 PSI runs before with no problem.

 

Sorry I guess I need to read slower.

But you have a good point, without boost sensing the ECU might be able to compensate for extreme conditions unless it is so safely rich at normal conditions. But the 300ZX TT was run using the ECU and I have to admit I have not looked into how it does it since it is from factory that way.

I guess this would apply to anyone that is running FI with ECU reflash.

 

I would think the MAF definitely cares about how dense the air is. The purpose of the temperature sensing function in the MAF is to calculate just that. Some calculation of flow rate and air temperature is used (and I think you're right, for an N/A car, the atmospheric pressure variance is probably negligible enough that the system doesn't make use of it) to calculate density, which in a system that is pressure indifferent is quite important.

And since the system doesn't care about pressure, it makes sense that higher boost levels haven't caused problems. However, combine an unaccounted for variable (boost) with colder, more dense air, is it possible to reach the signal potential of the MAF?

 

No I think you missed my point. The MAF itself is not going to reach any limit of metering based on density. Of course the ECU cares about this but the density of the air will not affect the MAFs ability to meter. That calculation is done at the ECU. The MAF is simply a heated wire and temp sensor. As air flows into the MAF the ECU sends added voltage to the MAF to keep the wire heated and using that it determines the amount of airflow based on how much voltage it needs. It also takes the temp of the air and sends all that data to the ECU for processing. The density of the air is not going to change either of those variables. The AMOUNT of air being flowed across the MAF sensor will definitely be a factor however. With cfm not changing greatly based on temp it is going to come down to HOW MUCH air flows across the sensor as opposed to how dense it is. The ECU will be adjusting for density. And as I said the ECU has been altered to do so correctly...

 

NOW I understand. Cool....Thanks very much MIA.

 

Hope I helped some....

 

Hotwire MAF metering is arguabley the BEST way to run an engine, in particular, an FI application. The MAF not only measures the volume of air, which is the critical, but as Mia mentioned, in measures temp and humidity, and determines the ideal ouput voltage to be returned to the ECU.

The problem occurs when the MAF is maxed out at 5.0V which occurs pretty early in the power band, depending on your level of boost. At that point, the reflash is essentially enriching fuel only using one axis....in this case RPM. You can get a decent tune out of this setup at low boost, but it presents problems at higher boost settings.

The eManage in its basic form has the same issue. But when used in conjunction with a MAP sensor, you can full resolution on both the pressure and RPM side of the chart, and you can tune far more accurately in this type of application.

 

Thanks for clarifying Sharif...its hard for me to put stuff in words... Bottom line unless you plan to run MAJOR boost the reflash is fine.

 

Reflash didn't help me.. I hit 10psi tonight and the MAF freaked out. That's in 40ishs degree boston weather btw.

I need to fix this problem asap.

 

The problem is you are hitting 10 PSI. YOu shouldn't be. DO you have the overboost correction pipes? If not you need to get them