MAFs are relitivley easy to tune but usually more expensive to integrate into a kit form. MAP sesors make more power and are cheaper but require intelligent conversion electronics to convert the signal to a readable one for the ECU. Because of the complexity of the MAP conversion they are harder to tune. We are making them plug-and-play with adjustability as an option.

 

Bump!

Any new updates from Huntley as to a MAP conversion?

 

[quote] The DME simply uses the RPM for reference to the fuel-tables stored in the chip<hr></blockquote>

Motronic in the 944/951 cars does two things to calculate fuel injection requirements:

1 - Determine amount of fuel (injector base pulse width or BPW) directly from the VAF signal and RPM. No other operational parameters are considered at this step.

2 - Modify the BPW based on operational parameters: O2 sensor, enrichments (accel, water temp, air temp, altitude, etc.), tuning adjustment tables (idle, part throttle, and WOT) and the values from the DME adjustment switch.

Step 1 uses the following table for the 89 951:



The resulting value y is a precalculated value that contains the VAF air flow converted to mass (at 75 degrees F), the fuel injector flow rate, and the desired A/F ratio (stoich). The BPW is then calculated in clock ticks (2 usec/tick) as:

BPW = (y/rpm) * 2000

This value is then clipped at this point. For the 89 951 the lower and upper limits are 0.85 and 11 msec. A reference value referred to as Load in later lookups is calculated at this point.

Load = BPW / 25

Step 2 is just modifications to the value calculated in step 1. These include the table lookups that you see in the editors from Protomotive and Bonneville Motorwerks.

Step 1 is what the signal massagers adapt the MAF output to fit. Step 1 is what trips up the people who go to larger injectors, it throws off the Load value which is used in step 2 (I might have a simple fix for that if anyone is interested).

The nice thing about Motronic is that step 1 results in the Load value used in step 2 that really doesn't care how the air flow is measured. It is possible to replace the current VAF based calculation in Step 1 with a MAF or MAP calculation that results in a final value that is the BPW. Then one can then use the step 2 tables to fine tune the system.


[quote] you said the volvo maf, like to one in the earlier link? that thing is monsterous,<hr></blockquote>

The MAF itself is small, I used a long tube at the input. MAF's need laminar flow across the sensor, the longer tube induces this, some designs use screens or grids. Pulsations, reverse flow and non-laminar flow are some problems you may encounter with putting a MAF on these cars. That's why the aftermarket kits put some work into the inlet designs and placement of the sensor, especially for the turbos.

 

Danno I am interested in this, If you must free up your intake, then do one of these MAF conversions:MAF on an NA 944, but I cannot get the link to work.
Dave Fracolli
85.5 944

 

Hi Dave!

Sounds like for an NA car, the Volvo MAF is the way to go. Pick up the sensor at a used-parts place for $30-50 and make a J-pipe manifold to reach behind the headlight for a conical K&N. Then buy of TT's custom-programmed chips and that's it! Complete MAF conversion for a couple hundred bucks!

However, the gains will be minimal; I doubt you'd see more than +10hp on an NA car. The MAF conversions has been a continual debate on the Turbo cars as it is. The increases are all lumped together usually with turbo upgrade, boost-controllers with increased boost as well as chips, K&N and exhaust. So it's tough to separate just the MAF from the entire upgrade package.

One of the things we'll be doing on Travis's car is to install the AFM-Link MAP upgrade. Then dyno the car with the entire stock intake in place (stock AFM, air-cleaner and intake ducts). Then rip it all out and install a K&N with large J-pipe and see what the difference with just changing the intake. Since we'll be using the MAP sensor in both cases, we can rule that out as a contributing factor.

It would be interesting to see before & after dyno charts on your car though...

 

I need to do something as I am having problems at idle with the new cam. Actually that is my plan as soon as I can find a job! Hopefully i will know in a couple of days. I am also interested to see how much HP was gained by installing 88 pistons and reworking the head and intake. TT how much for the custom chips?
Dave fracolli
85.5 944

 

Danno:
How can you get more power with map rather than maf? I always thought that maf sensors were more accurate (given laminar flow) that map. Heated element maf sensors are usually in the center of the bore whereas maps are usually closer to the walls, and therefore closer to lower pressure turbulent flow.

Also, you need an accurate engine effiency number for MAP to convert the rpm to volume. Are you putting this on your black box as an adjustment, or are you programming it? There should be a lot of variance from different mods on different cars. I would also expect the effiency to change based on turbo compressor speed, doesn't it?

Sorry for asking so much, but MAP sounds like a step back from a well designed (and tuned) MAF system.

 

Hmm, I don't think I ever said you get more power from MAP than MAF from a pure technological point. It's in actual practice of implementation that you run into issues with one versus the other. It's rather the combination of MAF kits using piggyback signal-massagers on top of the stock DME that has limitations on power generation. Simply because of the inaccurate control over fuel and zero control over ignition at all.

The unlimited power potential comes from using an aftermarket standalone EFI system that complete replaces the stock DME/KLR computers. This allows you instant control over changes in fuel and ignition. That's where the power increases come from, rather than a MAF vs. MAP comparison. In fact, aside from the flow-limits of each MAF sensor, using either with an aftermarket EFI system should yield similar results.

 

So what is the benifit of your MAP kit as opposed to a MAF kit? Other than the J pipe/K&N conversion? <img src="confused.gif" border="0">

 

Several benefits:

- no flow-limits on the sensor, MAF sensors have a flow-range that they work within. If you upgrade your turbo at a later time, you'll have to dump your MAF-2 sensor for a MAF-4, etc...

- almost infinitely fine fuel-control. Adjustments can be made +/- 128% in 500rpm increments through the entire RPM & load range. You can dial in a fuel-mixture that's perfectly optimized for power. On our test car, we obtained a full-throttle fuel-curve that was between 12.2-12.8:1 from 2000-6000rpm.

- This results in great driveability with infinite flow-capacity. Ask anyone who've tried to install a MAF-4 kit and see what kinds of problems they had with getting the car to idle correctly (much less pass smog). Our kit gives you high-flow yet fine control at idle & low-rpms (no lean spot from 1500-2500 under full-throttle).

- Unlimited upgrade potential is another feature. Since you can't max out the sensor, you can upgrade to larger turbos & more boost easily. Even easier with our custom chipset which will let you plug & play with larger 55lb/hr or 72lb/hr injectors without having to mess with fuel-pressure and re-mapping your entire fuel-map. Just turn a switch on the DME and the chips switch over to the 55lb/hr fuel-map. Turn the switch again and you've got the settings for 72/lb/hr injectors.