Carpokes Porsche Forum

7. Overboost Maps

Adjusting out the Overboost protection is a key task when ‘chipping’ a 944 turbo. Overboost protection is what causes the notorious ‘brick wall’ people describe when the boost goes too high and the DME cuts all power. Fortunately, this is an easy adjustment to make in TunerPro with our XDF. It’s a simple one-row scale with boost limits (expressed in PSI) for various RPM levels. Tuners often max out these cells with 255 (FF hex) across the board (in the BIN) to effectively eliminate this function. The XDF is set up to show values in approximate PSI values, with a max of 20.85psi. The XDF does the math behind the scenes and actually stores values from 0 to 255 in the BIN. So don’t be surprised to see 20.85 in the table after entering something higher. 20.85 in the XDF table is stored as 255 in the BIN, the highest number possible. Alternatively, you can increase the limits to something realistic for your boost levels, to preserve some protection from run-away boost. Just be aware the boost levels in the XDF are approximate. The DME overboost function doesn’t actually look at ‘boost’ but instead is based on engine load. The XDF just translates that into approximate boost levels, and those approximations can be off if the motor is bigger than normal, has a more efficient turbo, etc.

8. Full Throttle Fuel Maps

This is the map that attracts a lot of attention when ‘tuning.’ When running a 944 Turbo at 15 or 16psi, knocking (aka pinging, preignition, or detonation) is a critical concern. Gasoline consumes oxygen when it burns. At an AFR of 14.7:1, in theory, pump gas will have just the right number of oxygen molecules to burn all the gas, not too many, not too few. It’s also the sweet spot for minimizing the various emissions, so the car is designed to run at this AFR most of the time via its closed-loop O2 system. However, at full throttle the closed-loop system is turned off and tuners end up adding more fuel to the mix. The extra fuel helps cool the intake charge and makes it less prone to knocking. Up to a point, extra fuel also helps make more power. A good starting point is to shoot for about 11.8:1 at wide open throttle from the onset of boost all the way to redline, with little to no knock. Note that the factory let's the AFR lean out a bit on the top end, most likely mirroring the torque curve produced by the relatively small factory turbos.

The XDF maps are set up in theory so that you can enter your target AFR for each RPM range, but in practice there are too many variables for it to work with precision. Don’t expect to plug in 11.8:1 and necessarily see that on your wideband, especially if your motor is not stock. So use the numbers in the map as directionally correct, but don’t stress if you have to enter a 10.8 in the table to see 11.8 in practice. The only thing that matters is the AFR you see on your wideband. A little variation is ok, but don’t let it get much above 12 when on boost or you put your head gasket at risk. If you dip into the 10’s, you’ll be losing power and will eventually bog the motor. Here’s the factory Turbo, Turbo S, and a couple aftermarket maps for reference. The wide variation among the maps makes clear It's best to tune your car based on the actual wideband results -- not someone else's map!


Factory '86 944 Turbo full throttle map.



Factory full throttle Turbo S map.



Map from aftermarket chip A



Map from aftermarket chip B

9. Full Throttle Timing Maps

Be very careful with these maps. Too much timing advance can cause excessive engine knock and blow a head gasket in very short order. Ask me how I know. If you venture into full throttle timing, work in very small increments and keep a close eye on your knock monitor. Fuel octane rating is important here too. West Coast 91 octane will ping sooner than East Coast 93. For reference, here is a stock ’86 full throttle timing map, compared to a Turbo S map and a typical performance chip map. I wouldn't try to add timing like the aftermarket chip unless you have the fuel/octane to support it and can tune on a dyno to see if the extra timing is actually yielding any extra power. Sometimes chasing an extra 2 horsepower isn't worth the risk.


1986 944 Turbo Full Throttle Timing Map



1988 Turbo S Fill Throttle Timing Map (more boost, less timing)


Aftermarket Full Throttle Timing Map

10. Idle Speed Maps

While maybe not the most exciting, a solid idle can add significantly to the overall manners of a car. If you have an aftermarket camshaft or other changes that would benefit from a faster idle, we have you covered. The idle speed adjustment is a Carpokes exclusive, thanks to some very smart Carpokeans who were able to help pinpoint the code logic and location of the idle speed maps. Thank you johnb and Dave W! The main idle speed table has 3 cells tied to engine temps, and the XDF allows you to set the RPM for each of the three heat ranges. The XDF posted below contains a second idle control map you can try if the primary map does not affect idle speed. We discovered in the process of uncovering the correct 3-cell idle map location that there is at least one other potential map location that might come in to play on some cars. Without getting into the details here, if you have a Focus 9 Tech DME or any car where the wire to PIN 28 of the DME was previously cut to install a map sensor, the alternate 4-cell idle map may control. If so, be aware the A/C idle map will not work. If you ground DME Pin 28 (like the factory did) and/or talk to F9-Tech about making that change in its DME, you should be able to use the primary 3-cell map and the A/C idle control map.

If you opt to set a different idle speed when the A/C is on, just be aware that the rpm you enter only controls when the compressor is on, so when the compressor cycles on and off, the rpm will cycle between the A/C idle rpm and the standard idle RPM. As such, you may want to avoid making the A/C idle significantly faster than the standard idle.

11. Other Maps

With the XDF posted here on Carpokes, you have access to many other maps, including:

High Altitude Fuel Adjustment: The altitude sensor/switch under the dash tells the DME when the car is above 1000 meters. The DME then scales back fuel by a fixed percent to cope with the thin air. A fairly crude adjustment (but could be repurposed for other uses potentially).

Air Temp Fuel Compensation %: Adjusts fuel as a function of air temp. This is a carry-over from the Rogue Tuning XDF. MAFs generally account for air temp, so this was likely a table that Rogue Tuning zero'd out for MAF-equipped cars.

Idle Fueling Map: Allows you to set target AFR's at idle. The closed-loop system will mask most changes and bring the idle back to 14.7 unless these values are beyond the system's range. You want the mixture to produce a solid idle without relying on the closed-loop system, however. Otherwise you'll notice a hunting idle as the system works to bring the AFR in line. As such, it's best to disable the closed-loop system when making changes to this table (as you would when setting base idle speed).

Idle Timing Map: As the name implies, this is timing advance at various idle speeds. The DME uses timing to make quick adjustments to idle speed, so resist the urge to bump the timing way up. It will idle well with double the advance, but the RPM level may not seem as steady on transitions, etc.

Part Throttle Timing Map: This is timing advance when the car is not at idle or under full throttle. The table is based on engine load -- basically how hard to are pushing the motor (based on adjusted air flow meter readings).

Part Throttle Fueling Map: Same as the part throttle timing maps, just for targeted AFRs. Worth keeping an eye on knock and AFR at part throttle, especially under heavy load. That said, the stock maps have worked really well on my 3 liter motor.

Rev Limit: Set the upper rev limit to whatever you'd like, even a super-low valet mode.

Low RPM limit for Coasting: This is a temp-based table to set the RPM level at which the injectors will turn back on when coasting.

FQS Timing : The number of degrees to advance or retard timing when the FQS is set to position 4, 5, 6, or 7.

FQS Timing Threshold RPM: This is the RPM above which FQS timing changes will become active. Stock is 1600 rpm.

RPM Limit for Closed Loop: As the title implies, the closed-loop system turns off above this RPM (if not already turned off by the full throttle map).

Ignition Dwell Timing: This is the 7 x 12 ignition dwell table, based on voltage and RPM. The old XDF posted on the TunerPro site had a dwell map entry but it had errors and didn't work. Our's does. That said, this table is best left alone unless you really know what you're doing.

AFM Transfer Table 1, 2 & 3: More 'difficulty level B' maps (for those building a MAF or alternate load measuring system).

12. Downloads

To protect against Bots and Ne'er-do-wells, please find the following files available here in our download section.

Factory 944 Turbo DME BIN (24 Pin)
Factory 944 Turbo 1989 BIN (28 Pin)
Factory 944 Turbo S DME BIN (28 Pin)
Carpokes Basic Performance Chip (24 Pin)
Carpokes Basic Performance Chip (28 Pin)
1986 Factory KLR BIN
1989 Factory KLR BIN
Experimental KLR BIN without overboost
Carpokes XDF File (24 Pin)
Carpokes XDF File (28 Pin)

Reference and deep dive links.

KLR Deep Dive. johnb's deep dive into the KLR and its code can be found on github here

Idle Maps. Details and quirk with Focus 9 DME found in this discussion.

DME Dynamic Data Locations. For a list of dynamic engine parameter locations, see this post.

How DME Maps Work. To see the basic structure of DME maps and how the code interprets them, see here.

Deep Dive on Engine Temp. See here.

Injector Dead Time Increments. See discussion here show how deadtime is stored in the code.

Dwell Table Break Points. See here for details on dwell table layout.

List of all DME Maps. Download a list of all maps on the DME here. Helpful if looking for an obscure map not in our public XDF file.

Go to the first post.

Hi Tom, where did you get the OEM maps? I would like to get my hands on the 16V and 8V NA maps if possible.

I have TunerPro and wanted to look at the stock ignition timing maps for my S2 but havent found a good source. The only thing I found was some tunerpro files on the old RogueTuning website, but I am not sure if those are actually the OEM maps or if they have been modified in some way.

Appreciate any insight.

Tom, in your opinion, is this the better route to go than trying to go the MAF route for us California/strict smog guys?