# TT 225 diode mod on stock ecu(safe boost level, 3/4bar fpr, ect..)



## steve-o 16v GLI (Jun 26, 2005)

Hello ppl. Ive been a owner of a reflex 1.8t swapped mk3 for a couple yrs and after blowing 3 transmissions in a yr. I had to give up on fwd and am parting it out. So around dec. last yr I bought a 04 TT 225 roadster since I kinda became partial to the 1.8t and the TT was the first car I ever test drove as a kid. Im fairly savvy on the motor. Ive installed my own CTS turbo kit and much more on the mk3 but Im slightly unfamiliar with me7 and the other mk4 equipment/quirks my mk3 didnt have. Ive started the basic mods... cone filter, APR TIP, forge splitter, 3" cat back(have a SS eurojet DP yet to be installed courtesy of volksdude:thumbup::beer, MBC, wot box, 4.3w diode. Thats about it right now. Im still on stock tune.

Thats my back story. now heres my questions.
There isnt much info concerning the 225 and the diode mod. I dont have Vagcom yet and am wondering if anyone has experience with the 225 diode mod. Like what would be reasonable boost to run safely? Also I have a 4 bar fpr. Would putting that in be a good idea or no? The car runs great around 17psi but I have it at 15 since thats all it can do to redline anyway and Im not trying to run lean or anything. 

Any insight would be appreciated.:beer:


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## steve-o 16v GLI (Jun 26, 2005)

noone has a stock tune 225 that did the diode mod and has any feedback for me? Sadly I wont be able to afford meastro or a uni tune for quite a while yet so I just wanna make sure Im not doing anything detrimental.


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## darrenbyrnes (Jan 4, 2005)

Diode mod thread

I ran a diode w/o a tune for a while, but I am a 180Q. I tweaked the tune a bit with Unisettings.

Also - Save the 4 bar FPR for a tune that calls for it like a Stage 2 Revo tune or something.

:thumbup::thumbup::thumbup:

/Actually, I think I still have the diode in there even though I have been running a Revo tune for years.


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## Marcus_Aurelius (Mar 1, 2012)

Hey bud, I'll take a crack at your questions!

With the stock injectors and a diode:
- at 3 bar of fuel pressure, I'd recommend 17 psi at the most.
- at 4 bar of fuel pressure, I'd recommend 22-23 psi at the most.

With that said, doing this blindly without at least VCDS (or wideband sensor/gauge) is not the smartest thing to do. The diode is only clamping a sensor signal so the ECU doesn't triger limp mode from the extra boost. It does not do anything for the extra fuel needed to go along with the extra air. You need to have some kind of way to know what your fueling curve is looking like, that way if your leaning out to dangerous levels, you can add fuel (bigger FPR) or reduce boost to keep things in order.

Another thing to take into consideration is heat, at higher boost, the OEM SMICs are overwhelmed and don't do much at keeping the air charge cool enough (I've seeing IAT in the 70's Celcius at 20 psi of boost) and stock SMICs). If you're doing this, you need to moniter and keep IAT in check as well (upgraded SMICs, water injection etc.)


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## steve-o 16v GLI (Jun 26, 2005)

Sweet thanks for the input guys. Looks like il just keep it at 15ish psi till I can at least get vagcom n unisettings or lemmiwinks. 
On the intercooler side of things I'd love to do a awic setup like yours but I might just go FMIC for ease of install and its my daily driver. Although the silicone intakes/frozenboost 350hp kit doesn't look like a bad beginner setup. 
Also def wana get a maf based w/m injection setup too which just might get done before upgrading the intercoolers. 
Thanks again Max. You are one of my inspirations to finally get my TT

And a pic I had on my phone of when I first got it just for sh!ts n giggles. 







I'm sure you guys in the TT forum will be seeing more posts from me now. Might as well get acquainted.


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## Marcus_Aurelius (Mar 1, 2012)

You'll fit right in, we've got a great core of active members in this forum! :beer:


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## steve-o 16v GLI (Jun 26, 2005)

Yea the 1.8t forum isn't quite as nice as the TT forum I'm finding. 
Didn't make it to any shows this yr. Been blowing all my money on the car. Lol. Hopefully next yr il get to actually meet some of you east coast TT owners on the forums. Haven't gone due to the broken window in my top. Ugh


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## poopie (Feb 22, 2005)

came into this thread expecting a flame war with noobs telling the OP to get a real tune. Came out satisfied that people posted good information. 

I ran a diode mod for years on my wagon until i tore it all apart. It worked pretty well for me


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## steve-o 16v GLI (Jun 26, 2005)

Well I'm def not a noob. Lol I might not know everything but I'm always trying to learn something new. Im moreover new to the TT/me7 platform. I lnow the 1.8t motor like the back of my hand. When i got my CTS kit for my mk3 i installed it myself in less than half the time a shop quoted me for. Lol. I posted this in the TT forum also because the ppl here are much more informative n less opinionated. But notice I still did have to make it clear in my first post that I will do a tune when money permits but for now squeezing a few psi out of the stock setup has been proven to work safely. Might not be the best but it works for the time being.


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## darrenbyrnes (Jan 4, 2005)

poopie said:


> came into this thread expecting a flame war with noobs telling the OP to get a real tune.



And by my first post here I meant:

HEY N00B GET A REAL TUNE!!!


:laugh::laugh::laugh:

/I think I still have some diodes...I'll check and post what I have in case you need one.


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## steve-o 16v GLI (Jun 26, 2005)

I feel all warm and cozy here already:laugh:
:beer::beer:


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## steve-o 16v GLI (Jun 26, 2005)

Ok I have another question now. Since I don't have vagcom yet would it be ok to put the 4 bar fpr in just to be safe? If I understand correctly it won't affect anything negatively (aka running rich) the added fuel will just be calculated out by the ecu if it's not needed.Am I right?

Might not be able to resist the urge to tweak the mbc a lil. Lol


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## Marcus_Aurelius (Mar 1, 2012)

The ECU will correct accordingly whenever the O2 sensor is in charge of fueling aka closed loop (idle, crusing, and some part-throttle but until thresholds are met). WOT and heavily loaded part-throttle, the AFR curve will be fatter/richer than at 3 bar.


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## steve-o 16v GLI (Jun 26, 2005)

Sweet. Thanks for the clarification max. Well I decided to put it in tonight anyway n try it out. Despite my best efforts to keep a rag over it to stop the spray i somehow directed it right into my eyes/face when it popped out! Luckly i have quick reflexes and none actually got in my eyes but that was def the most scary incident i ever had workin on a car! 

After running the car for a short bit at around 20psi both with and without. I must say I def noticed a big difference with the 4 bar. With the 3 bar you could really feel the top end fall off. Now it pulls much smoother throughout the entire rev range. Maybe it's a placebo affect or a miscalibrated butt dyno but I'm satisfied to keep it in for any time I want a lil more boost to play around.


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## steve-o 16v GLI (Jun 26, 2005)

Can't wait to get a uni tune or maestro. I def enjoy driving my stock turbo, barely modded TT more than I enjoyed my BT, fully built trans mk3 1.8t. Sure the mk3 was faster but it's just a completely different beast to the TT. A tune, w/m injection/upgraded IC, haldex controller and maybe a f23 and il be golden.


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## Marcus_Aurelius (Mar 1, 2012)

The difference is most likely not a placebo effect!

With the richer AFR from the 4 bar regulator, the ECU is probably making less timing corrections and that's what you're feeling (I have yet to see a flashed TT without a real good FMIC or W/I, not have a healthy dose of timing pull due to heat... and that's even with an almost flat base timing curve). 

Just the other day, I played with another member's flashed TT (Unitronic). At a bit over 20 psi, he was seeing massive 9-12* timing corrections from onset to redline on all 4 cylinders (the timing showed a +1.5* flashed over the base map when I read his file in Unisetting). By simply removing the added +1.5* of timing, and adding some fuel in the primary fuel channel as well as some enrichment under load, I was able to get his corrections under control. The car was a lot faster and held 18* of timing up top vs the pathetic 12* he was seeing before. 

Get yourself a water injection kit and VAG cable and you can squeeze some good power out of this puppy. :beer:


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## steve-o 16v GLI (Jun 26, 2005)

I'd really like to do an awic setup but it's my daily so relocating the battery and losing my spare isn't something I want to do. That and no one is buying my FMIC setup off my Jetta so I might use the piping n intercooler to fab something up. 
But first on my performance/maintenance list is a tune so I can delete the emissions junk. That's the only thing I miss with the mk3. I could see and identify every vac tube and sensor on that car. Finding n fixing leaks was usually as easy as looking under the hood. Lol but my broken top glass. Yea that's def first.


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## steve-o 16v GLI (Jun 26, 2005)

I think tomorrow if I have time after work il take some pics n make a intro/build thread to move these discussions to.


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