Oshin951

What is better ?

BoostGuy951

Good Question! You're in for alot of different opinions. I chose a MAP. I just like the idea of there being absolutely no airstream restriction. Alot of people swear by MAFs, though. You'll need to do some searches of the site, you should find more than enough info to make your decision.

Good Luck!

Danno

Different factors with lots of overlaps. Here are some threads:

01-11-01: <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=001713&p=" target="_blank">Installed MAF and ADJ Regulator... problems!!! </a>
01-11-17: <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=18&t=000502" target="_blank">arc2/arm1/maf#4 problems (long) </a>
02-03-01: <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=18&t=000814&p=" target="_blank">ARC 2 - Cool start settings vs. Warm settings</a>
02-03-13: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=000910" target="_blank">one big maf kit problem, help </a>
02-08-07: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=002110" target="_blank">A bit rich...but my buddy's CBR600 can't keep up! </a>
02-09-16: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=002444" target="_blank">MAF Stuff.....AGAIN!! </a>
02-10-19: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=002726" target="_blank">gauge project done (almost) </a>
02-10-26: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=002788" target="_blank">Huntley Racing stuff? Suggestions please </a>
02-12-14: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=003261&p=" target="_blank">Mods for 87 951 </a>
03-06-09: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic;f=18;t=005471" target="_blank">map vs maf </a>

That said, MAF has improved tremendously over the past year. Our <a href="http://www.gururacing.net/DigitalMAFupgrade.html" target="_blank">Digital-MAF upgrade</a> for older systems has really given people control and resolution over their MAF kits with EFI-style 3D mapping based upon load X RPM compared to older 4-knobbie adjusters (flow-limits is still an issue).

Given the removal of a major restriction in the intake tract (the AFM), the differences between a MAF and MAP as far as flow is minimal (both dramatic over stock anyway). A big 77-85mm MAF will flow 90-95% of the air as the MAP's unobstructed intake. The major restriction in the MAF is the sensing tube across the middle of the airway and the various step-up and step-down adaptors used for the J-pipes.

BTW, check out what the most prevalent auto-maker uses on their engines... Honda!

fast951

There are many opinions regarding this subject. My intention is not to speak badly of any other product out there. Just my personal opinion!

I like the MAF as it’s a good indicator of the amount of air your engine is consuming. The Map indicates pressure, which is not a direct indication of the air being consumed. At a given boost level, a large turbo flows much more air than a smaller turbo. The MAF will generate a larger signal when used with the larger turbo, as the MAP will give you the same signal as the boost has not changed. So the engine is consuming more air, but the signal to the DME did not change.
Also, when changing the volumetric efficiency of an engine (cam, exhaust, intake..)
The MAF will compensate (to a certain degree).

As in anything you buy, there are good products and bad ones. Not all MAP kits, and not all MAF kits are the same. A MAF must be sized to support a certain HP level, too small
and you max the output at a lower RPM.

A great setup is to use the signal from the MAF and a second signal from a MAP. This is
What the Vitesse PiggyBack does. You can alter your fuel & timing based on LOAD(MAF signal)/ RPM and you can add a MAP sensor and use its input to as the third parameter. 3D tuning LOAD/RPM/BOOST…

m42racer

Ok, I'll throw in my lot here too. I agree that MAF are probably more accurate in many ways but we must compare apples with apples here.

If you say that MAP's measure pressure and MAF's measure airmass then thats correct, but conversions are never left to the plain exchange of air metering devices.

Take the MAP conversion here. Yes it will measure manifold pressure and be the load value in the fueling. But wait, and conversion MAP or MAF requires adjustment to the fueling to get the correct A/F required. So whatever the manifold pressure, Turbo size etc., etc., the mapping still needs to be adjusted. The differences here are typically what the load value of the algorithim is based upon. Same goes for MAF. It uses air volume as its load value. RPM been common always. Now if you talk TPS as a load value, now your talking problems that can be found. typical problems for example are A/C loads etc. Manifold pressures change, but TPS stays the same. Usually TPS is only used on N/A race applications where no accessory loads are present. In most systems TPS is used as a correction value with RPM and MAP or MAF been used.

So the idea of which is better is hard to define. both have their good points. I would say that if a perfect idle and off idle transistion was required then MAF would be the way to go. That is you have the PERFECT chip to go with it. If unrestricted air flow, and good throttle response with torque been a need, then MAP with the PERFECT chip is the way to go. As Danno pointed out, Honda's are all MAP based. And the one thing you have too admire about those engines is the power they produce from such small engines and thats all from intake system parts.

fast951

The MAF will compensate for variation in the Volumetric efficiency of the engine. As Ve directly affects the Mass of air used by the engine. A MAP does not and requires constant retuning. Of course, if you deviate too much from initial settings, both systems will require retuning.

I agree, both systems must have good tuning chips to work correctly so does the AFM.

The MAF is not restrictive. The only restriction I see is the Air Filter in front of the turbo. The Turbo inlet is 3", the J-pipe is 3", the MAF sensor is 3+" and there is the Air filter...

I owned a 3.0L 951 with Motec, it had a MAP sensor. Idle, on/off boost transition and all around drivability were not there. A minor vacuum leak (and cars do get them) and it messes things up.

I believe the MAF is more flexible and the way to go. The MAP sensor is less expensive than the MAF sensor (just the part). Why is it that the 993TT and 996TT all use MAF?

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.

m42racer

Absolutely. This is what this forum is about. The opinions of users.

I must ask, how MAP is not affected by the VE of an engine. Both are affected by the VE. As soon as MAP changes, so does the VE. Same for MAF. As for retuning, I think this more about the original tune, not how the load is measured. I'm sure in some cases the overall tune could be better with MAF, as could the tune with MAP in some cases. I think its all in the CHIP, and what control you have over the MAP of MAF. The use of digital devices on either is far superior over the old style analog **** devices. Still they are better than nothing at all.

fast951

The point I'm making is that a MAF is capable of handling moderate changes in Ve without the need to retune. A MAP based system must be retuned.

When the Ve increases, the engine will use more air. The MAP is measuring pressure, so at 15psi pressure there is more air going through the engine with higher Ve. Yet the MAP signal is the same, so you must retune or you will run lean.

With a MAF, when there is more air, the signal will be higher. Since the signal is used by the DME to alter fuel/timing, you don't need to retune. As the DME will use the higher signal to figure out the duty cycles for the injectors.

A huge variation in VE requires a retune with any system.

Danno

VE changes will show up as variations in manifold-pressure... <img border="0" title="" alt="[Wink]" src="wink.gif" /> <img border="0" alt="[bigbye]" title="" src="graemlins/xyxwave.gif" />

m42racer

Yes sir. I'm not sure what he is saying. Maybe he does not undersatnd modern EFI systems danno. I undrestand them to be very smart and can make changes thro interpolation. Maybe we are seeing something here differently, but talking about the same.

AlexE

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by m42racer:
<strong>Yes sir. I'm not sure what he is saying. Maybe he does not undersatnd modern EFI systems danno. I undrestand them to be very smart and can make changes thro interpolation. Maybe we are seeing something here differently, but talking about the same.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I am pretty sure that Fast951 understands modern EFI's.... We are not dealing with a modern EFI system. We are dealing with +20 year old technology in our 951's. Like you stated earlier lets talk apples to apples..... I think Porsche is doing ok using MAF on their high end turbo's just as Honda is doing wonders in their econoboxes.

What is the better solution for a 20 year old car???

The answer to Oshin951 .......... is that there is NO right answer to such a broad question just opinions. Just like Fast951 stated in his first post.

fast951

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by m42racer:
<strong>Yes sir. I'm not sure what he is saying. Maybe he does not undersatnd modern EFI systems danno.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">m42racer, very good observation!!! I'm impressed, did you figure this on your own??

I wonder why I even bother discussing thing with you. You are much smarter and more informed than I can claim... The thread is all yours, go ahead and share your wealth of knowledge about modern EFI. I'm sure many are waiting to take notes..

I guess I'll figure things out the hard way. And I'll stick with the old EFI and the MAF.

m42racer

I was not trying to **** you off here. You made a statement that the MAP based systems do not effect the VE of an engine, or something like that. It seems that Danno and I agree that it does or can make a dfference. If you put it out there, don't get all offended if people counter your opinion(s). I get it all time. You seem to have a braod knowledge of many things, much of which I probably could not match with you, but on somethings you show that your knowledge is not complete. From discussions here we can all learn. Its not about who knows the most. For that we have Danno. Comparing different systems is a good topic. We just need to give complete facts so that all information is correct.

Keep discussing, because we all learn from it.

fast951

Discussing things is fun and should be productive. However, statements such as yours, add nothing to the value of the conversation. So your statement "I'm not sure what he is saying. Maybe he does not undersatnd modern EFI systems danno." adds nothing to the value of the discussion, except to be insulting. If that's the way you feel, why even bother having a discussion with someone that does not understand the subject at hand?

Again, if you re-read my earlier messages. We are comparing "MAP Sensor" to "MAF Sensor" on the 951. With a Motronic system that was designed for a "AFM sensor". So let's stick to the facts. Where did the subject of modern EFI come from?

I still believe that the MAP sensor does not compensate for a change in Volumetric Efficiency as well as a MAF sensor. I never said that a MAP does not affect Ve!

Also I pointed out that because a MAP sensor is not restrictive, it does not mean that a MAF is restrictive... And it's not as I pointed out.

I would like to hear your theory on how "Under the same boost" a MAP can compensate for air flow. (Again, a K27 flows more air than a K26 at 15psi! Same boost more air. The MAP generates the same signal for 15psi)..

And no you did not **** me off! However when I'm having a discussion that I feel is not going anywhere I just walk away.

As I made sure I stated earlier, there are many opinions. If you expect people to have a discussion with you, they must listen to your argument and you should listen to theirs. There is no need for statements that have no purpose except to insult others. If you think someone does not know what they are talking about, then prove your point and walk away.

Which I'm about to do....

Oshin951

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

Thanks for the help I guess I got to look into this a bit more and see which one is for me.

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