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I designed and built a new DME that works on late model 944 and 951 8-valve engines. It has been running my 1986 944 Turbo for a while now, and I wanted to share my progress to see what you guys think of it.
This DME is meant to be a direct replacement for the BOSCH ML3.1, only radically more reliable. The 30+ year old factory DME is basically starting to fall apart at this point. I have disassembled a lot of DMEs over the years and seen firsthand how bad it’s getting. In my opinion, the main reason for the majority of failures is the poor quality PCB BOSCH decided to use in the ML3.1 design. They really skimped on it to save a buck and everything from cracked solder joints to water damage is the result. If I did nothing else to the design but replaced the PCB with a modern one made from FR4 material and coated with an LPI mask it would likely last twice as long. I certainly could have done that, but I decided to modernize the entire DME design and solve all the known issues while I was at it.
I refer to this replacement DME as a hybrid because I am still using a few of the original parts. However, electrically it is around 98% brand new. Around 300 old electronic parts (including the PCB) have been completely replaced with fresh modern electronics. I used the highest quality parts available and sourced from reputable venders.
I could actually replace the last three with new parts, but the cost/benefit ratio may not be there. I acquired a small batch of new FQS switches form the original vender, but it was expensive and took almost 2 months for them to custom make it for me.
This is a really good thing you are doing here. Nice to see a new more robust option for the tired old motronics.
If you have PCB manufacturing capability, you could make a killing if you could make reproduction AFM wiper boards to go with your DME.
Originally Posted by Ftech9
I designed and built a new DME that works on late model 944 and 951 8-valve engines. It has been running my 1986 944 Turbo for a while now, and I wanted to share my progress to see what you guys think of it.
This DME is meant to be a direct replacement for the BOSCH ML3.1, only radically more reliable. The 30+ year old factory DME is basically starting to fall apart at this point. I have disassembled a lot of DMEs over the years and seen firsthand how bad it’s getting. In my opinion, the main reason for the majority of failures is the poor quality PCB BOSCH decided to use in the ML3.1 design. They really skimped on it to save a buck and everything from cracked solder joints to water damage is the result. If I did nothing else to the design but replaced the PCB with a modern one made from FR4 material and coated with an LPI mask it would likely last twice as long. I certainly could have done that, but I decided to modernize the entire DME design and solve all the known issues while I was at it.
I refer to this replacement DME as a hybrid because I am still using a few of the original parts. However, electrically it is around 98% brand new. Around 300 old electronic parts (including the PCB) have been completely replaced with fresh modern electronics. I used the highest quality parts available and sourced from reputable venders.
I could actually replace the last three with new parts, but the cost/benefit ratio may not be there. I acquired a small batch of new FQS switches form the original vender, but it was expensive and took almost 2 months for them to custom make it for me.
This is a really good thing you are doing here. Nice to see a new more robust option for the tired old motronics.
If you have PCB manufacturing capability, you could make a killing if you could make reproduction AFM wiper boards to go with your DME.
Thanks, just feeding my addiction...
The AFM wiper board is fairly specialized, I would need to look into how something like that is made. It might be a better approach to look into some of the newer armature positioning technologies that have come about. I will add it to my project back log and do some research when I get a chance.
Looks great..what about a conversion for the early cars? What kind of $$ are we talking about here? Is it programmable? I would like to convert to a late model DME and an MAF conversion for my early 944. However, the Mega/microsquirt option comes into play about the 1500.00 price point, which also about the same money for a rogue conversion..Pls correct me if I'm wrong about this..Thanks.
This is a really good thing you are doing here. Nice to see a new more robust option for the tired old motronics.
If you have PCB manufacturing capability, you could make a killing if you could make reproduction AFM wiper boards to go with your DME.
Or what about a MAF conversion? The voltage curves from the afm are known, it couldn't be that much work to work out a translator with all the other electronics being replaced.
Looks great..what about a conversion for the early cars? What kind of $$ are we talking about here? Is it programmable? I would like to convert to a late model DME and an MAF conversion for my early 944. However, the Mega/microsquirt option comes into play about the 1500.00 price point, which also about the same money for a rogue conversion..Pls correct me if I'm wrong about this..Thanks.
“Looks great..what about a conversion for the early cars?“
I already began adapting the design to fit and work with the early 944 enclosure. Most of the circuitry I designed is compatible, but there are some differences that I will need to work out. But there is one caveat, if you have a performance chip in your early DME it will not be compatible with the upgraded electronics. On the plus side you will be able to use any performance chip you like that is made for the late model 944 NA.
“What kind of $$ are we talking about here?“
Price point is going will be between $300 and $400 USD.
“Is it programmable?”
It is just as programmable as the factory DME, it uses the same exact EEPROM and is compatible with all stock and performance “chips” used in late model 944's.
“I would like to convert to a late model DME and an MAF conversion for my early 944. However, the Mega/microsquirt option comes into play about the 1500.00 price point, which also about the same money for a rogue conversion..Pls correct me if I'm wrong about this..Thanks.”
That could be right, I never priced the options that are out there. I currently defer to Josh over at Rogue Tuning for anything on the Performance/Tuning side. It is not currently on my product road map to offer a MAF solution.
Or what about a MAF conversion? The voltage curves from the afm are known, it couldn't be that much work to work out a translator with all the other electronics being replaced.
I don't think it is quite as easy as it sounds to mimic the AFM with a MAF. They respond very differently to changes in air movement and density. It would take someone with a lot of tuning/programming experience to smooth out the differences and make the engine behave properly.
For me, creating a DME to support the newer 16 valve 944/968 and later 911 is basically the holy grail. The engine management is really not all that different except the newer DME has a knock control board that I currently do not have designed. I will get there, but it is going to take some time. I would also need a lot of community support with my current products to justify the investment of time and resources. For perspective, this new DME design I am offering was started way back in 2011 and I didn't have a production ready unit until 2013.
Is there some sort of list or notification channel for when these get released? Specifically thinking about the (hopefully) version for early 944s.
The only notification channels I have are Rennlist and my website. That project is in the very early stages and easily could take 2 or more months to get to production.
Just an FYI... You can run a late dme in an early car, as long as you also use a late afm. And you'd need a late dme as a core.
Absolutely correct, the connector and pin-out is identical between the early and late DME. Except for the Idle Speed valve on the late DME, but that shouldn't matter for an early car.
05-01-2016, 03:41 PM
New DME Option under Development
