I have seen a couple guys going to a MAP sensor based fuel adjustment map for boost tuning. For the minimal cost I am curious why Greddy did not do this from the start instead of using MAF voltage vs rpm for the fuel correction. There must be a reason they went with the method they did. I am sure they did R and D on both methods because they sell both options. Any opinions??

 

Wow, the greddy setup doesn't come with the MAP harness? I assumed it did. Sorry, can't help out as to why though.

 

The MAP sensor option is over $100 in additional costs...that is probably the first reason.

The second reason is that I think a MAP based system would not meet CARB requirements, which was a goal of the Greddy kit. Of course, this doesn't make a whole lot of sense...but CARB is lame....because even if Greddy included the MAP sensor, it would still use the MAF signal under normal cruise conditions, and switch to MAP under boost.

The MAF sensor is not necessarily a bad thing when cruising around...and not WOT.

The third reason...which I just thought of now, is that the kit is designed for 5.6psi, so a MAF sensor based system is perfectly fine. A MAP sensor would only be required if you increase airflow beyond the limites of the MAF....probably around 9psi or so.

All that being said....you can also buy the optional MAP sensor and knock yourself out!. I still like the Greddy kit the best out of all the TT options.

 

From what I've heard, still trying to find verification, the MAP sensor/harness is strictly used for 'tuning' purposes, by fuel pressure I assume, once you max out and clamp the MAF.

Somebodys' got to figure out some way to keep the airflow referenced system by either scaling back MAF voltage or optimally tricking the ECU into accepting a larger MAF.

I'm hoping Split Second has the answer.

 

The MAF is clamped and the eManage controlls the injectors by using the MAP sensor input at WOT. I think this solves all the issues.

 

There's been alot of talk about the MAF sensor and tuning, using a MAP instead, maxing out the airflow of the MAF, blah, blah, blah..
So I'm just curious, does anyone else here notice that the MAF placement on these kits is exactly the way Bosch has repeatedly told SR20, CA18, and KA guys NOT to do it? That Nissan has NEVER designed a turbo motor this way? That JWT is the only kit to set up the engine management the way it should be with the MAF upstream of the turbos behind the air filter? That every NA SR20 and KA engine boosted with an E-manage or Apexi SAFC was not set-up the way these other kits are for the VQ?
Well, anyhow, to answer your question.. I have no freakin' idea why any of these kits are set up the way they are, using the MAF alone to register airflow and boost is beyond me. Anybody?

 

Yeah, I noticed. So did several others when the designs for the first SC kits came out. My guess... manufacturers tested it, saw it worked ok at their boost settings and said screw it. Too much trouble to relocate.

 

Greddy would have had to run a single filter intake to run the MAF the way you are talking about. This is a hell of lot more plumbing complexity for virtually no beneift. It makes no difference if the MAF measures air as its sucked into the turbo vs. pushed into the TB. At least I can't figure out the difference. Now that I think about it, the MAF reading AFTER the turbo has compressed the air has to be more accurate then measureing pre-compressed air. Also, relocating the MAF would require splicing and an extention to the harness...again...added complexity for no benefit.

 

Two more feet of pipe routed along the front of the engine is hardly a hell of a lot more plumbing. JWT seemed to fit it just fine.

It makes no difference if the MAF measures air as its sucked into the turbo vs. pushed into the TB.[/QUOTE]

Except that the maker of the MAF (Bosch) has repeatedly stated this is a great way to screw up the unit and mess up your A/F ratio.

At least I can't figure out the difference. Now that I think about it, the MAF reading AFTER the turbo has compressed the air has to be more accurate then measureing pre-compressed air.[/QUOTE]

What!?!?somebody should let Nissan in on this fact. They've designed a system that has allowed RB motors to pump 700hp with the MAF right where it should be and now we figure out it's all wrong. The guys over at www.SR20forum.com should be ashamed, not running the MAF where it's the most accurate for all these years. God forbid their A/F ratio ever look as haggered as some peoples' do on this forum.. or what will happen when someone tries running higher boost or rpm when the MAF is already maxed out on airflow.. I'm sure they'll come up with more band-aids to heal a poor set-up.

Also, relocating the MAF would require splicing and an extention to the harness...again...added complexity for no benefit. [/QUOTE]

Except that the MAF would still be right where it is in the stock location? Again, JWT has the set-up and no fitment issues. Hell, the PE set-up moves the MAF further than the JWT placement.
What's been done is a lazy and really cheap way to manage an engine. There are better alternatives, used on every other boosted Nissan, Subaru, etc.. that use a MAF and have run much better with better tuning potential than the cheap set-ups found on most of these kits. It's a shame too, cause the E-manage can really be put to better use. JWT is coming out soon and I imagine more will follow thier tuning example, as EVERY other system on EVERY other manufacturer that uses a MAF does not rely on the MAF to measure boost.
EDIT: damn quotes...

 

I still don't see any benefits. And the MAF is just measuring air..not boost. It would get maxed out at some point...whether you install it before or after the turbos. RB motors and OEM turbos use a MAF sensor that has a much higher flow and measurment capacity than our N/A tuned MAF sensor...that is why they can generate tons of power without MAF issues.

I'd like to understand the reasoning that BOSCH claims it damages the MAF sensor by placing after the turbo. Air is air...so why would it be damaging? The only thing I can think of, would be if the intact charge is warmer just before the throttle body vs. right before the turbo compressor...but I am just speculating becuase I dont really know if that is the case. I suppose the heat could be damaging to the MAF, and maybe that's the reason for the warning.

And what are these "ragged" A/F charts you are refering to. Every A/F chart I've seen on this board looks smooth and progressive...of course a bit rich...but that is not a function of the MAF location.

As i stated....a MAP sensor is best iin higher boost conditions on our car....this avoids all the issues with our MAF sensor, and is a better way to go when boosting greater than 8.5psi or so.

Also, please tone down your sarcasm...it detracts from the otherwise very intelligent discussion we are having.

 

When I say measure boost, I am not referring to the MAF acting as a boost controller, but relying on the MAF to account for the pressurized air coming out of the turbo. This is not its intended purpose, hence why it is not set up this way by any other manufacturer. The MAF should be used to measure the intake of air by the turbos only, not the amount of pressurized air produced by the turbos. You follow? Bosch has informed many SR and KA guys the danger of boost running through the MAF, as one lb of boost is not the same as one lb of vacuum on the sensor. The increase in temp alone has an effect on the sensor to measure voltage properly, and the charge of air has destroyed MAF sensors over time. Consider that without a blow-off valve, the charge can destroy turbos, now consider that air slamming back past the sensor every time the throttle is closed has shot MAFs to crap before. You might think only 5.5 or 6.5 psi is small, and ineffective, I believe otherwise over time, and apparently so does Bosch.
Before the filter, the MAF is rarely maxed out. The MAF on the VQ can handle much more flow than the SR or KA MAFs, it is similiar to the VK. SR guys only need to replace their MAF when approaching 400 hp, or a good bar of boost. The RB doesn't come with anything larger than our motor, but it does come with two of them. Even so, the MAF will not be maxed out by anything close to what we are running. Think about it, right now the MAF can measure what, 7psi of airflow within relative safety? You think the turbo's will pull that much air by themselve's? Hardly. The MAF is being maxed out right now because we are measuring 7 lbs of boosted air through it.
Even then, the A/F might be progressive, but way off the mark for a well tuned turbo motor. This is probably a blessing in disguise as the high compression will benefit from the lower intake charge temps, but the MAF should never be the bottleneck on any motor.
Even with forged low comp pistons, what good is it going to do if you up the boost on your Greddy system and your MAF is maxed out? Probably won't happen with you I'm sure, but doesn't it strike you as odd for such a kit to have so heavy a limitation to the output? Why even use TD05's for such limited capacity? I think Jesseenglish hit the nail on the head - they saw it worked all right for THEIR boost settings.
Now, what is the solution, bigger MAF? Good luck, that is a bandaid that still doesn't solve the bottleneck problem. MAP? More power to you and the Honda boys, I think MAP is the way to go as well- but not in conjunction with the MAF. You mentioned clamping the MAF and relying on the MAP for WOT, and anything else that might push more air than the MAF can register, but why even use the MAF at all? The maps for idle and part throttle aren't any more difficult to create than for WOT. They all require dyno time and guessing to come up with a tune that works. The E-manage will support it, but not very well I think. AEM would be better with their MAF to MAP conversion set-up. Of course, it's stand-alone and multiple pressure sensors are included to do the job right, but then that's the quandary we're in right now isn't it?
I applaud everyone's creative thinking with these kits. I've read some really wild ideas, and am happy for everyone that is happy with their set boost levels. However, it was asked why no MAP sensor was included from the start. I am merely extending this question, to why should we need one at all?

 

Well said. Thanks for the input.

 

The wire to send the map sensor data from the e-01 to the emanage is only ~$20. I am using it and I will be tuning my fuel maps to the map sensor.

 

Good points. None of these kits are perfect...but if we wanted to wait for absolute perfection, nobody would ever buy a turbo.

 

if perfection is what your looking for you would have to dump the e-manage and get a real stand-alone.

 

Oh boy...don't get me started on the drawbacks of a stand-alone for a street 350Z. It is not the magical cure-all.

 

Ummm, the MAF itself doesn't care what pressure the air is at (other than perhaps Bocsh's concern about physical damage). It measures the mass of air flowing past, whether at 5 psi or -0.1 psi.

If you are maxing out the MAF after the turbo, you will max it out before the turbo as well, simply because you are moving the same mass of air (low pressure, high flow before the turbo, high pressure, low flow after the turbo).

Now, it may be that the MAF actually looses accuracy at higher pressures, and that would be another reason to run it pre-turbo, but you won't alleviate the problem of hitting the limit of the sensor.

Also, if you run the MAF pre-turbo, what happens when the wastegate opens? Aren't you venting air that you sucked in through the MAF, and therefore won't you run richer due to the lack of that vented air? Or would you be running an additional sensor (like a MAP) to control the fuel under boost and therefore the MAF is basically not performing a useful function when a wastegate would be functioning? Or does a wastegate only vent the exhaust around the turbo to keep it from spinning too fast and therefore it doesn't affect the intake air?

Thanks,
D'oh!

 

I don't know what your plans are for your Z but for mine I plan on having it modified past a simple bolt on and go turbo kit. So do you think that the e-manage is a better system for the Z? I have seen what the e-manage does for hondas and all you end up with is a rebuilt motor and an empty pocket. Just curious as to what all your drawbacks are on a stand-alone? I'm new to Z's but have seen standalones in everything from street hondas and 69 camaros to turboed s2000's and 240's. They all seem to work pretty well when installed and tuned by someone that knows what they are doing.

 

As I wrote earlier, a lb of boost is not the same as a lb of vacuum. You are right in that the MAF measures mass, but I think you are confusing that with volume. The MAF doesn't measure volume of air. Hence why it cares about boost and why it will not be maxed out before the turbo. Consider that before the turbo, it will measure an air mass of whatever the atmospheric pressure is in your town in psi. So your MAF measures whatever psi is in the air and sends it on to the turbo where it is compressed, the key word, and then comes out heavier by however much boost over atmo the turbo is set at. This is increased mass of air, but not volume. And as we all remember from science class, this equates into denser air. This dense air has more mass per volume, and is measured in pounds exerted onto a square inch, psi, over and above the atmo (boost) and is sent on down to the throttle. If the MAF were in this tract, the volume of the air would be the same, but it has greater mass due to compression and therefore, as just discussed, is denser air per the same volume. The CFM, or volume, of air ingested by the turbo is the same as expelled, that is just simple physics, and the simple way a turbo makes power. By cramming more air into the same volume is where the power comes from, as denser air allows more air mass per the volume of air sucked into the combustion chamber. Obviously though, the turbo cannot compress the air and keep up with volume in the same instant, hence we have lag. But, it is key to remember that volume is the size of air charge, not the mass, and volume is not measured by the MAF.

Now, it may be that the MAF actually looses accuracy at higher pressures, and that would be another reason to run it pre-turbo, but you won't alleviate the problem of hitting the limit of the sensor.[/QUOTE]
It is not the pressure that screws the reading, it is the tmperature. The MAF Nissan uses is a hot-wire sensor type, and this allows the MAF to measure and equate for those variables that affect mass such as temps, humidity and altitude. This is an advantage over the MAP sensor which requires the use of other sensors for this information. The wire runs voltage that is affected by temperature, as most electronics are, temperature that is in extremes when measuring compressed air. This means the MAF measures the increased mass of air, but does so with regards to the temperature also, and adjusts the reading to compensate. The same way the MAF reads denser air at night when it is cool out, it measures the extra mass of air in regards to the temperature as well, or when it is really humid out and the air is denser the hot wire voltage changes with the extra chill from the moisture and registers the extra mass. The MAF is not air temperature dependent mind you, but inherently works using the air temp as a variable. All hot wire or hot film MAF sensors work this way. Think about it, the pressure of ambient air is a product of temperature and mass, thus any factors that change these two variables (turbo) will in turn change the MAF reading. The MAF senses the extra mass created, but also the extra temperature generated, to calculate for the denser air. This, coupled with the physical charge of the boosted air, is why a lb of boost is not the same as a lb of comparably innocent vacuum.

Also, if you run the MAF pre-turbo, what happens when the wastegate opens? Aren't you venting air that you sucked in through the MAF, and therefore won't you run richer due to the lack of that vented air? Or would you be running an additional sensor (like a MAP) to control the fuel under boost and therefore the MAF is basically not performing a useful function when a wastegate would be functioning? Or does a wastegate only vent the exhaust around the turbo to keep it from spinning too fast and therefore it doesn't affect the intake air?[/QUOTE]
Well, the wastegate does not have anything to do with the MAF. It is the physical means to control the boost by limiting the kinetic energy of the exhaust gasses transfered to the turbine via a pressure activated valve that allows the gas to bypass the turbine in route to the collector. This valve can be incorporated into the turbine housing or the manifold, but both work off the pressure coming from inside the compressor housing. This allows the desired boost level to be set and the valve to open or close as necessary to maintain the maximum boost limit.
EDIT: I am sure you were thinking of the BOV, but I need to get to work and will be glad to post on that later if you would like. These are good questions.

 

You are wrong about the eManage....when i get some time and energy. I will write up a detailed thread on the pros and cons of stand-alone vs. eManage.

Again, it all depends on your application. If you intend to run 500whp, then I would go stand alone, but for 98% of our purposes, in the sub 450whp range, the eManage is terrific, and highly programmable. No MAF conditioning....just controlling pulse width and timing.