m42racer

Hey 951, don't give up now.

As for my comment about your knowledege of EFI systems, it was never meant to insult you. As I said later on, mybe we are talking about the same thing, just from a different angle. But your comments about MAP not changing the VE is not correct. Let continue here and I will choose my words more carefully.

I would start off here to say I thin there is nothing wrong with a MAF setup. My understanding here is that with Federal requirements for leaner burning engines, a more precise way of measuring the air was needed, to meet the emmisions limits. Honda have done this with MAP, as have several other makers. Most common is MAF. MAF was certainly not choosen for perfromance reasons.

That all been said, lets get back to the topic at hand. Your comments regarding MAP and its ability to compensate for changes in VE I still do not agree with. Lets first see what VE is.

VE = actual cfm (measured),
----------------------
theoretical cfm

theoretical cfm = rpm x displacement
-------------------
3456

The question here is how acurate is the MAP verses MAF sensors. Most MAP sensors have very fine resolutions, pressure verses mili volts. I'm sure the MAF is similar. It all comes down to the software and how it interputs this infromation. The VE of an engine is based upon the calculation of measured air.

Even with all of this data, what we are talking about here is the change over from a AFM to either a MAP of MAF. Whatever we change to, mapping still is required to compensate for the differences. So if we take a MAP conversion, the measured air (load value) is used along with RPM and other inputs to equate the fuel volume required. At any given air volume (MAF) or pressure (MAP) compensation is done in the mapping to get the desired A/F. The measured air is used to base the load value. Interpolation is then used between these points to smooth out the values. So your comment about the 2 turbo's each running 15 psi is correct if no mapping is done. But mapping is done, so at 15psi aMAP system uses this pressure as a reference value (load)to base the fuel calculations on. The amount of air at 15psi is the same whether measured from a pressure sensor of MAF. Now if you did not change the mapping and changed over the Turbo's then you are dead right. But you would most probably be very lean too. Also, without changing the mapping, you would also be lean if using a MAF.

I'm interested in hearing your thoughts here. With our continued discussion, others may learn with me.

aka 951

I think both of you are correct here. The point is that MAP sensors only measure pressure where as MAFs measure air flow. The argument that I believe fast is trying to make is that if nothing is changed in your configuration, other than the a more efficient turbo, the MAF will be able to compensate by outputting more voltage while the MAP sensor will return the same voltage (assuming running the same boost pressure).

Danno will probably argue that the MAP wil counter by measuring the intake temp and adjusting fuel based on the colder intake temps of the more efficient turbo. Unfortunatly this adjustment does not compensate for efficiency in the turbine section which leads to less backpressure and better VE. Also changes such as exhaust, valves, etc. probably won't be recognized by the MAP sensor either.

One of the problems with MAP sensors is the specific one fast is eluding to: their inability to account for modifications to improvements in VE. As m42 stated the MAP sensor software can be revised to compensate for VE changes and with the Link system in particular this sounds like a relatively easy task. So you're both right.

With all that said, I'm not sure if a MAF or MAP really makes much of a difference on a stock turbo'd car. With the 280-300 rwhp dyno numbers some of the turbo S guys are putting up just with the Guru chips, it seems to me that the turbo is already maxed out.

fast951

Erick, you got the idea.

M42racer, once tuning is done with the MAP and the MAF everything is fine, let's use this as our base and we'll keep boost as a cosntant. The job of the MAP and the MAF is to generate a signal to be used by the DME.

Once you change the VE of an engine (different valves, intake, exh., turbo or ???) the volume of air used by the engine will change (UP or DOWN) at a given RPM & BOOST level.

My point is that the MAF is capable of compensating for the change in Air Mass (caused by the change in VE). So the MAF senses the change and pass the correct signal to the DME which in turn will adjust the fuel mixture.

The MAP does not detect the change is the volume or mass of air, and generates the same signal (based on boost which is constant). The DME gets the same signal and generates the injector duty cycles based on the original calibrations and not accounting for the increase or decrease in the air that just entered the engine.

As I said earlier, a HUGE change will require retuning with both systems. A smaller change requires a retune with the MAP but not the MAF.
So in my opinion a MAF is more user friendly.

Also, the change in temp affects the output of the MAP to a great degree. The map is on the pressure side of the intake, the same side that experiences a big deviation in temp.

Since we are getting technical, check out this spec for a XXX MAP sensor. You see the effect of temp...

<img src="http://boards.rennlist.com/upload/MAP001.gif" alt=" - " />

<img src="http://boards.rennlist.com/upload/MAP003.gif" alt=" - " />

So to summarize this issue. We agree on some points, but we disagree on others. You pick a MAp and I pick a MAF.. The bottom line, is whatever works for you...

porshhhh951

I think it will be great if people that have experience with both the MAF and MAP on the 951 can jump in and share with us their impressions.

i just recently had a maf(among other things) system put on by lindsey racing.I am very happy with the drivablity of the car.Performance wise i am very pleased with my maf system.My 951 idle's like a sentra,pulls like a 911 turbo,and can get gas mileage like a civic(off of boost short shifting i got 28mpg).Bottom line i am a very very happy maf customer....and by the way mine isint even digital(although i plan on making it so in sept.) <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" /> <img border="0" alt="[cherrsagai]" title="" src="graemlins/drink.gif" />

Luke

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Danno:
<strong>The thing with upgrading a car using bolt-ons, is that it's tough to change the engine's VE-volumetric efficiency. Removing the stock intake and going to the MAP system changed the stock specific-output from 40HP/Ltr•BarBoost to 59HP/Ltr•BarBoost. That's why we need 20psi to generate the 364rwhp; double the stock HP, yet we only increased boost 35% (absolute).

The other way of increasing VE is with internal mods like increasing compression, port & polished head with 7-angle or fully-contoured valve-seats. Solid-lifter conversion and matching cam, etc. This would be an expensive way to achieve 364rwhp.

What we are also spending time doing is getting precise calibrations to minimize tuning-time for the end-user. </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica"></font>

• <font size="2" face="Verdana,Tahoma,Helvetica">This is a quote from : <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic;f=18;t=004654" target="_blank">guru 364</a></font></li>

<font size="2" face="Verdana,Tahoma,Helvetica">Danno is explaining the process of preparing the 364 kit. I am assuming the 364 kit will utilize his MAP kit.

m42racer

I still must be missing something here. You state that if you change valves, turbo etc, you will change the VE. Then you say a MAF will sense the difference in air mass if the boost is not changed. I get this bit, but not the bit about changing the VE?

If you change the VE would you not in the real world remap the engine? Just how much can you change without remapping to take advantage of the change. I get your point, but if I can say this, it appears to me that to make your point, you have not taken into account what would be required to do under normal circumstances. If this is not the case, I will accept that the MAF is a better way to go. Just having a problem accepting your reasoning, while knowing what normally is required to be done. As for the temp effect to MAP, yes it does, but then that why you run a temp sensor. Most MAF sensors have temp sensors don't they.

I think that there is a place for both here. But I also believe you must understand the differences and how they can affect the final outcome. To say one is better, we must know the application. To say MAP cannot compensate and the MAF can, is a very broad statement, without first making full allowances for how the MAP signal is used and that under typical applications remapping is always required to be done.

Danno

We need to stop talking in black & white, all-or-nothing, qualitative terms.... Because this complete leaves out the actual implementation and quantitative issues. There are roughly three steps to tuning:

1. install hardware upgrades
2. dyno-tune and re-program:
_ a. chips or
_ b. piggyback signal-massager (MAF, MAP, etc.) or
_ c. standalone EFI system
3. repeat #2 as necessary

A lot of people are looking for the 'magic bullet' hardware item in #1 where they can just buy something and POW! they've doubled their HP. Many people forget that by far, the largest amount of time and money will be spent in #2, optimizing your air-fuel ratio for the particular configuration you have.

Both MAP and MAF systems are piggybacks on top of the stock Bosch Motronic v.3 DME. As such, there are some algorithmic and procedural steps that must be followed. Comparing the pure MAP and MAF technologies is arguing over the 3-5% of the whole solution. When looking at any system, the features that help you in the tuning step#2 is what will really make the difference, not the underlying technologies used in step #1.

One feature that's a real time-saver and allows for precision tuning is 3D mapping with load X RPM referencing. That's because you want to take a look at the dyno-sheet and say, "Ah ha! At 3000-3500rpm we need to add some fuel and remove some from 4500-5000." A system that will allow you to take the next step and make that correction easily and quickly is where the real value can be found.

BTW, for those with standalone aftermarket EFI systems like SDS, Tec-II/III, AutoTronic, GameBoy, etc. what sensor are you using?

More on the technical backgrounds and implementation of MAF vs. MAP later...

TT

A system solely based on MAP and IM temp cannot account for changes in the Ve of an engine. Systems like those Honda uses can detect changes in Ve by monitoring the AFR using switching O2 sensors. By monitoring the actual running AFR and comparing it to what was calculated using the MAP, IM temp and the current Ve table, such a system can detect changes and update the Ve table during operation. GM has actually put both MAP and MAF on certain vehicles. They update the MAP Ve tables using the MAF and could operate off of either alone if one failed.

As to why certain manufacturers choose MAP or MAF, it most likely comes down to $$$. Honda's use of MAP means they only have to manufacture and stock one type of sensor. Ford alone has 15+ different models and sizes of MAFs.

Personally I'm sticking with MAF since it is the easiest to adapt to the existing DME.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> I would say that if a perfect idle and off idle transistion was required then MAF would be the way to go. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Larger diameter MAFs tend to have problems measuring air at low flows so this is not necessarily true. Fast951, have you had a chance to use any of Pro-M's Univers plus models?

m42racer

Danno, this was point, but I took the long way round. When 951 stated that a MAF could compensate when a MAP could not, my thinking was he forgot about the real world where your step #2 is required.

Someone else here just added how Honda may use O2 sensors with MAP. Danno, doesn't your MAP device take an input from an O2 sensor? Again, theory is great to banter back and forth, but in practice things are always a little different.

fast951

I always said that tuning is required. I also said that big changes in Ve require retuning for both systems. So I didn't forget step #2 (Tuning).

However, a minor modification to Ve, will not require retuning with the MAF but will require retuning with the MAP.

I agree with Danno, that the tools used for tuning are very important. That's why I picked a MAF and bundled a PiggyBack with it. It offers full 2D or 3D mapping with Data Logging. The PB allows the user to fine tune the car after making modifications.

TT I have read some of your earlier posts, and your technical knowledge is impressive. No I have not tried the "Pro-M's Univers plus".

m42racer

Both will require it. Any change to a 951 engine with a MAF will require remapping.
Or you are accepting a poorly running engine. Still everyone has their own idea of whats a good running engine.

fast951

It appears that we will never agree on this one.

A MAF is more forgiving, as it compensates for minor changes, and your engine will not be poorly running (and I speak from experience). However with a MAP it will REQUIRE retuning or it will be a poorly running engine.

We are back to my initial comment. There are many opinions...

aka 951

TT is dead on as usual. I was wondering how Honda got away with MAP on a street motor where wear is an issue. As he says, the oxygen sensor reports the air/fuel to the ECU which decides how much to change the VE mapping. I believe newer MAFs do this also. Not sure if its because OBDII. Older MAF systems like those used on Saabs did not change the mapping because the MAF sensor's told the ECU the condition of the motor based on the voltage outputted. On a comparable MAP system the ECU would always believe that the engine was brand new.

fast951

aka 951, thank you for giving an example of yet another change in Ve where the MAF compensated for it and the MAP did not.

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

TT

An example for small variations in Ve is the stock cars. My 944 popped a ring around 160k miles. The Ve surely went to hell (#4 read 90lbs compression dry, 130 wet) between the high miles and busted ring. The engine still worked fine and it still passed emissions (amazingly it was still within the 1l/1000km oil consumption spec).

Bottom line is a MAF/VAF system that has no intake leaks will adjust for variations in engine efficiencies. You have to go to more advanced systems to get the same result with a MAP.

As to which one to choose, depends on how much dyno time you want to invest. MAF: very little to none. MAP: depends on how different your car is from the development cars (none if your car is pretty much in the same condition). Hell, if WOT power is all you want, no driveability, just put a big 4 barrel on the car and it will work fine.