Custom DME chips

[Alex89]

You guys have me a bit surprised here, I didn't think this turbo is that big. I clearly don't understand the specifications well. It was compared to a LR S48 when I bought it which I understand is only slightly larger than a K26/8. If I'm wrong here I guess I should modify my plans accordingly.

Most (all?) of the MAF kits I've seen are sold with a tuning package. Is there a MAF option that will work with a chipped DME like we've been discussing?

Tom I just ordered a copy of that book, thanks for the recommendation.

[Tom]

Well Lindsey claims the S48 is good for 480hp. If that's even close, the AFM would max out way before that. But turbo claims and the real world are two different things, and you can always turn the boost down as John says. John's a real engineer while I'm a shade tree hacker, so consider the source (and listen to him) but what I would do is install the turbo and log pin 7 of the dme to see how much boost you can run before the AFM maxes out. Then back off a little to give it a buffer for changing conditions. My concern would be that the new turbo is laggy on the bottom end, yet you'll need to turn the boost down on the top end, resulting in less power under the curve (fun) than a stock turbo. No idea if that's likely, but it's possible.

There are two kinds of popular MAF kits currently on the market: 1) Vitesse Racing with its rewritten 'true maf' code; and 2) everything else.... All of the non-VR MAFs work the way you describe, meaning the DME still processes the MAF signal as if it were the AFM signal. The MAF is telling the computer the air mass, and the DME thinks it's being told the air volume, so not ideal. That approach 'works' but the tune tends to be a compromise and less able to deal with ambient changes, etc. That's why a lot of those systems come with a user tunable piggyback -- to allow for fiddling since no one tune is likely to be great across all situations. When the DME processes the MAF signal as air mass, like VR, you can get a factory-like tune across a very wide range of conditions.

So with that limitation in mind, you could pick up a MAF sensor with sufficient range and tune a chip to run the motor with it. That's exactly what the early MAF kit suppliers were doing around the turn of the century. I'm sure that could be a fun project, if you accept the inherent limitations. The other option that might be of interest if you are a hacker at heart is one of the hacker-friendly stand-alones like the MicroSquirt. It's a bigger project with lots of electronics and tuning challenges, but without the inherent limitations of using a mass air sensor on an air flow computer....

[Alex89]

Tom I just reread the claims from Lindsey Racing on the Super 48. They say the turbo is "capable of 480 HP" but also state it is comparable to a K27/8 "in size and power output." (I'd misread this previously, thinking they said K26/8.) Forum browsing shows people getting 270 to 300 RWHP from a K27 which is still around what I was expecting. Further down the page LR also states their Super 61 is "capable of 610HP" then offer a dyno curve maxing out at 401 RWHP with 21 psi of boost. I have to assume when they say "capable" they're referring to lab bench conditions which are unachievable in a real world application.

In any case this whole project is really just an experiment for me and my first foray into major modifications. I probably should have found a smaller turbo for my setup, but for now I think I will stick with the turbo I have, keep the stock AFM and see how it turns out. I like your suggestion to monitor pin 7, I've also been laying out a basic Arduino-based data logger to collect data from a few other pins. I can and probably will swap to a different turbo, MAF, standalone (MicroSquirt), etc. setup in the future but for now am curious about what the stock DME can do.

John (Fast951) I just realized who you are; I didn't recognize you by your user name. Thank you for your input. I do plan to study and understand the theories before I attempt any tuning. That is actually why I'm posting about this now, even while my car is in pieces. I'm hoping to have a good understanding and plan before the car is assembled and ready to start. I'll appreciate any other guidance you can offer.

[Tom]

Yes, totally agree on the "capable of" horsepower numbers. I'm 'capable of' eating right and getting an hour of cardio every day, but.... Sounds like you have realistic expectations and are doing it in part for the fun/challenge, so team Carpokes is onboard! I've done lots of Arduino stuff over the years too if helpful. Both the SpeedoBooster and the Track Nanny here on carpokes are based on an ATmega 328 with Arduino bootloader. Also look at DataQ for stupid cheap data loggers. Keep us posted! This is my kind of project.

[mwc951]

Alex89...
Cool to want to learn to burn your own file on a chip. You're more brave than I am.
Seems like the whole MAF/MAP/Chip technology for our cars has evolved into practically
a plug & play set up. My experience has been with a Vitesse VMAF+ chip board, MAF & MAP sensors
little to no "tune" is needed. Very VERY close to spot on AF ratios after installing the system.
Change turbo, intake, exhaust the system compensates for the change.
Rest easy knowing VR offers the best customer support in the business as well as the knowledge to offer a rock solid kit.

DannoXYZ...
Good to see you on the forums after all these years!
If you recall, you still owe me a functioning DME chip or a refund from our business transaction in 2004/2005.

[Dave W.]

This looks like a fun thread.
I've been burning my own chips on my 951 for nearly 12 years so I have plenty of experience. I'd recommend that you get an Ostrich from Moates net so you can upload changes in realtime via your laptop. It's much easier that burning a chip and R+R the DME with each change. I have several pages of notes and addresses for various parameters, so just ask.

[gruhsy]

This looks like a fun thread.
I've been burning my own chips on my 951 for nearly 12 years so I have plenty of experience. I'd recommend that you get an Ostrich from Moates net so you can upload changes in realtime via your laptop. It's much easier that burning a chip and R+R the DME with each change. I have several pages of notes and addresses for various parameters, so just ask.

Guessing you did your tune for your Stroker motor?

What DME do you have stock or Rogue?

Mods with your Stroker?

[Dave W.]

This looks like a fun thread.
I've been burning my own chips on my 951 for nearly 12 years so I have plenty of experience. I'd recommend that you get an Ostrich from Moates net so you can upload changes in realtime via your laptop. It's much easier that burning a chip and R+R the DME with each change. I have several pages of notes and addresses for various parameters, so just ask.

Guessing you did your tune for your Stroker motor?

What DME do you have stock or Rogue?

Mods with your Stroker?

I have the stock DME. I started tuning it when the car was still stock. The stroker motor was built 4 years later.

Nearly everything is modded now. The main mods are a 2.85 hybrid stroker, 8.5 compression, 9R cam, full intake and exhaust, MSD Blaster coil, converted to run on E85 fuel, 3bar fpr, Bosch 044 pump and 1000cc injectors. Tuning is split between the stock DME and a MAF Translator Pro, which is a speed/density conversion that replaces the AFM with a 3bar MAP sensor and GM IAT. It also has integrated, tunable EBC. The best part is that the Translator is also fully tunable via TunerPro RT. I now have two USB cables in the car; one for tuning the stock DME and the other for tuning the Translator.

When I converted to E85 I went through the DME code and found many tables that reference fuel vs air temp and fuel vs coolant temp (aka 'head temp'). Those tables were needed since E85 requires a lot more fuel during startup and at cold temps.

It's not available anymore, but there's a little bit of history behind the MAF Translator Pro. Joshua from Rogue tuning used to be very active on the FullThrottleSpeed forums and wrote several detailed posts to help 951 owners get started with the Translator Pro. A few years after that Joshua released his own chip, MAF and tuning system.

[JamesM]

I know this is an old post, but I am getting in to this, I have some old chips I wanted to read but the old rogue tuning files do not include a xdf file for the earlier 944 NA with the 24 pin. If anyone knows where I could find one if one exists it would be appreciated. Also, I know the early na uses a 2732a but what does the later 28 pin dme use, because I could always convert to that and mess around with that instead if I can't find the file I need for the 2732

[DannoXYZ]

JamesM, check out this post with map locations on earlier 4K chips ('82-85). Enough info for you to make your own XDF.
http://forum.tunerpro.net/viewtopic.php?t=2964

For '86-87 24-pin 944NA DME, convert it to use 28-pin EPROM with procedure here:
http://forums.pelicanparts.com/porsche- ... -chip.html
Then you can use the 28-pin BIN and XDF.