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Old 06-30-2021, 08:06 PM   #1
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996 DME tune work in a 2.7?

I bought a neglected '04 base without a key. I don't know if I'll fix it or part it out, but I'd like to see if the engine runs okay. I can get a DME/Immobilizer/Fob set from a 3.6L 996 to install and test it. They are both compatible 7.8 DMEs, with the same part numbers, but I expect the 3.6 will have a different fuel map than the 2.7. Will it adapt enough to get the engine running? Any harm in trying?

The car came to Oklahoma a few years ago from around San Antonio. Anyone recognize it? That's a big badge decal.


Looks like it was cared for prior to the last owner.

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Old 06-30-2021, 11:28 PM   #2
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if the pn are the same then it will be ok. fuel maps will be different but it should at least let it start.
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Old 07-01-2021, 07:11 AM   #3
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Don't do this unless you plan on a 986 flash. The MAF housing sizes are different and the dme will not be able to compensate for this difference.

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Old 07-01-2021, 08:35 AM   #4
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Quote:
Originally Posted by ike84 View Post
Don't do this unless you plan on a 986 flash. The MAF housing sizes are different and the dme will not be able to compensate for this difference.

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Well Ike, that led me to here: https://www.renntech.org/topic/21472-fuel-air-mixture/ which is where I found that the 996 has a 3.5" tube and the 986 uses a 3". That thread was about putting a 996 engine in a 986, which is sort of the opposite problem, but for testing purposes I may just put the MAF in a bigger housing.

Alternatively, I don't have access to a PST-2, but I could make a set up to bench flash the tune from the car's existing DME to the 996 DME using Galletto. Chances are that I'd 'brick' the DME though since my knowledge is pretty shallow in that realm.
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Old 07-01-2021, 11:48 AM   #5
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You can do this. You said you just wanted to see if the engine starts. I wouldn't do this long term (more then a few minutes anyway) but at least it would allow you to start the engine.

Of course if the only reason to start the engine is to see if it is locked up, you could just crank it over by hand to see if it turns. Will be a PIA with the plugs in, but you could do it.
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Old 07-01-2021, 05:03 PM   #6
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Thanks for the replies. The 996 DME is just to see if the engine runs and probably drive the car in my driveway to evaluate it. It factors in to whether or not I part the car out or repair it. If I decide to do the repairs, I'll either put money into a new key or have the correct tune loaded.

The odometer shows 190k miles, but the engine serial number shows that it was a factory replacement engine - no idea how many miles are on the engine or when it was replaced. Just another cheap project car to learn a few things, then probably get my money back out of it.
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Old 07-02-2021, 05:43 PM   #7
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If you run the 996 on the stock 986 airbox, you will run very rich. Too rich. The dme can't compensate, it will throw the cel, and may kill your cats in the process. If you're gonna do this , at least change the MAF housing. It's 3.25, not 3.5". There is a bmw part that will work and I can dig up the part number for you, but you will have to splice it into your existing intake somehow.

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Old 07-02-2021, 06:32 PM   #8
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Quote:
Originally Posted by ike84 View Post
If you run the 996 on the stock 986 airbox, you will run very rich. Too rich. The dme can't compensate, it will throw the cel, and may kill your cats in the process. If you're gonna do this , at least change the MAF housing. It's 3.25, not 3.5". There is a bmw part that will work and I can dig up the part number for you, but you will have to splice it into your existing intake somehow.

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Thanks for the 3.25. I have a large collection of odd parts and I'm pretty sure I can find a tube that will work or adapt one. Audi A8 or Mercedes ML430 is probably about right.
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Old 07-03-2021, 07:27 PM   #9
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Thanks for the 3.25. I have a large collection of odd parts and I'm pretty sure I can find a tube that will work or adapt one. Audi A8 or Mercedes ML430 is probably about right.
Here's what i used

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Old 09-26-2021, 05:23 PM   #10
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Today I finally had enough free time and spare parts to get the car running. So far it has just run on jack stands for a warm up and basic checks, but the stock intake with the 996 electronics it sounded good after the lifters stopped rattling. There is no particular plan for what to do with this car yet. It seems to run fine so far, but I expect that it will need some correction to run optimally with the 996 DME. I may get the correct tune for it, run it with a larger intake and MAF tube, or pull the engine and put it in another car. The engine is a factory replacement engine from '04:



The car has been sitting since some time in 2018. To get it running I also needed to replace the fuel pump. I tried rigging an old pump from a scrapped '01 in there, but it turned out bad too. R.A. had VDO pumps for about $200 so I went with that. Replacement was pretty simple with the correct part.

Now my curiosity has moved on to the difference between the fuel system of 986.1s and 986.2s. In 2002 models the fuel pressure regulator was moved from the rail on the engine to the sender in the tank. The unit in the tank looks pretty much like what sits on the fuel rail. I know Ike has a thread about using the 986.2 injectors in a 986.1 and that they just need to be slightly modified for fitment.

So, If we take a 986.2, 3 chain, DME 7.8, M96 engine and put it in a 2001 model how do you want to handle the fuel system? Swap the hoses and sender or just use the fuel system from the 2001 (I think we'd need a fuel rail from a 2001 on the later engine)..?
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Old 09-28-2021, 05:11 PM   #11
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Quote:
Originally Posted by 78F350 View Post
Today I finally had enough free time and spare parts to get the car running. So far it has just run on jack stands for a warm up and basic checks, but the stock intake with the 996 electronics it sounded good after the lifters stopped rattling. There is no particular plan for what to do with this car yet. It seems to run fine so far, but I expect that it will need some correction to run optimally with the 996 DME. I may get the correct tune for it, run it with a larger intake and MAF tube, or pull the engine and put it in another car. The engine is a factory replacement engine from '04:







The car has been sitting since some time in 2018. To get it running I also needed to replace the fuel pump. I tried rigging an old pump from a scrapped '01 in there, but it turned out bad too. R.A. had VDO pumps for about $200 so I went with that. Replacement was pretty simple with the correct part.



Now my curiosity has moved on to the difference between the fuel system of 986.1s and 986.2s. In 2002 models the fuel pressure regulator was moved from the rail on the engine to the sender in the tank. The unit in the tank looks pretty much like what sits on the fuel rail. I know Ike has a thread about using the 986.2 injectors in a 986.1 and that they just need to be slightly modified for fitment.



So, If we take a 986.2, 3 chain, DME 7.8, M96 engine and put it in a 2001 model how do you want to handle the fuel system? Swap the hoses and sender or just use the fuel system from the 2001 (I think we'd need a fuel rail from a 2001 on the later engine)..?
I don't rember for sure how the pressure regulator is controlled on the 986.2, but I want to say it's also by vacuum hose. If that's the case (meaning that it isn't controlled by the dme) then you should just be able to reuse the entire 986.1 fuel system as is, including the rails. Injectors will need to be modified to fit the rail (assuming it has the later Bosch injectors) and you'll need the bank 1 crossover tube boot that has the vacuum line connection routing to the pressure regulator valve (salvage that from the original engine), then you should be good to go.

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Old 04-11-2022, 06:06 PM   #12
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Here's some follow-up. The 996 DME works to start and run the engine without making any modifications. It does not work perfectly. The 996 tune is different for the ABS, PSM, and Variocam.


I did put in a larger diameter MAF tube and it seemed to run better through the higher range RPMs.

After starting to part out the car, I swapped a few parts back on and did a Rallycross using an 04 Boxster S DME set. No check engine for the Variocam, but I ran over a big rock and did this:


With a new sump plate on it and the car still not dead, I just ran it in an Rallycross again. No rocks this time, but I started loosing coolant after a delightful spin into the deep grass. Tires... I just need to figure out what tires to use.
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Old 04-12-2022, 06:11 AM   #13
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When pushing a new tune using piwis 2 software, you actually have the ability to only push fuel maps (it's almost as though Porsche expected engine swaps!) and leave the rest of the programming as is. Check out my thread in the diy section - this is what I did when I changed my MAF housing to a larger diameter. Btw, if you didn't change the MAF housing at first when you did the tune, you were likely running VERY rich (until the dme could bring it back into range using closed loop operations). I did the opposite - I put a larger MAF housing before pushing the 996 tune and the car ran so lean that it, well, let's just say it wasn't pretty...

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Old 04-12-2022, 06:13 AM   #14
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Also, what camera are you using on your dash? The video is excellent!

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Old 04-12-2022, 08:58 AM   #15
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Even after the years I've been buying and playing with these, I still don't have a PIWIS or PST2. I may try using Galleto software to read the original DME and transfer the tune info to the 996 DME. Truth is I have other projects and cars that I care about and this one is a low value beater that I can destroy with no worries. ...Still it's useful to have around for these events. *I'm not trying to be competitive, just 'blowing off some steam'.

For a camera, I used a GoPro Hero7 Black. It works well shooting 2.7k at 60 FPS with motion stabilization.
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Old 04-12-2022, 09:50 AM   #16
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Ahhh gotcha. If you ever want one just let me know and I can help you set it up. The piwis 2 is good for all Porsche models up to 2015 or 18 (I don't remember off the top of my head).

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