Do many people mod the 2.5TDI engine ?


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Jan 30, 2011
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just wondering if many people mod these or are people more into the petrols etc ?

If so whats the best things people do etc no silly expensive stuff

I cant imagine many people mod them but thought id ask see what type of figures and things people have i see alot of people with things in there sigs but not sure which is petrol diesel etc etc, this is my first diesel car and im use to hondas with no torque so this makes a change haha!
I belive there 150bhp standard, with a remap you should see 180bhp.

If you look in the diesel section theres a guy whos done a fair bit to his 2.5tdi and i belive hes got it running around 220bhp or something like that.
hi mate ive been looking at these myself and curious of tuning potential. A chip makes a massive diffrence apparently. For example quote for the 150bhp model increase to 177bhp and torque from 310nm to 385nm. Other than that id be curious what else, exhaust etc?

How do you find the car by the way? Fast..ish? or slugish! Im doing over 50miles everyday with my 1.8t but with my mods im really enjoying the power but sticking to 70mph id be better with a diesel :)
You can get out of 150hp 2.5tdi around 200-210hp with stock turbo and nozzles if the engine is in good shape. With bigger turbo and nozzles you go waay over that. 230-280hp.
I'm targeting to some day with biturbo solution. ;)
That would be fjtwelve 260 Bhp+, mine isnt far off either. There's a lot you can do to a v6 tdi, swapping nozzles for larger ones and upgrading the turbo is a start. I dont really like generic remaps as they limit the torque low down (to protect the clutch) so a high quality tuning box from PSI or Steinbauer really does the trick. Swapping the turbo with the one from the 180Bhp AKE engine (has a larger compressor wheel) is a start and Iveco/Bosio race nozzles also return a healthy power output. The v6 has twin intercooler as standard wich are fine up to 270Bhp. The clutch is strong on these and the DMF will take a pounding. The diesel isnt built or geared for drag races but will really be in its stride on motorway where they pull the same in any gear. I have a GT2559 turbo fitted on me quattro (will be soon replaced with a BV 50 from the 3.0 Tdi as its better flowing and i got-it for a song) wich is a bit laggy but really good at high speeds. However my Iveco nozzles are allready maxed out even with the Steinbauer box turned to maximu. Later AKE engines also had a 3 plunger injector pumps wich can supply a lot of fuel but will only play ball up to a point. The biggest problem is there are not many people preppared to mod them pumps (same pumps were fitted on big 6L cummins engines in the states and there are pumps moddified to fuel over 1000 Bhp) as many diesel specialists will only put them back to Bosch specs ! Also by swapping the nozzles to larger units from lorries or tractors will need adressing in the tune/remap as the engine will shudder at iddle ! Thing is again, tunners know jack **** when it comes to a "custom" remap and strugle to work with- much easy to slap a generic map and charge hundreds for the privilege ! My v6 tdi quattro does 160 mph whilst still returning high 30 Mpg average...
Wow im impressed what you can do with these engines. So to see 200bhp on these for example could you just remap and then??? can you just put in new nozzles with out any problems then or do they have to be mapped in?
Its better to start with a tuning box (some find it fine for a while) but you kinda get bored and want more ! Swap injectors and turbo THEN remap so the map can take in consideration the mods you added. Also removing the cats off will allow the turbo to spool nicely whilst still passing the Mot. Its not the Bhp thats impressive its the torque they put out- 400Nm+ from 1350 rpm's all the way to 4000 rpm's ! Pity there are not many off the shelf mods available but there are a few companies who offer hybrid turbo's wich are plug and play and good for 260Bhp. I would rather go with a tried and tested Garrett GTB2260VK turbo off the 3.0 Tdi audi a4 244Bhp as its good for over 300Bhp yet spools as fast as the stock blower !
just be careful of chocolate cams and folowers and self imploding fuel pumps if pushed.

^^ Adamss24 above knows hiz shiz listen to him, or read on FJtwelves or quattrojames in the B6 forum, both of those have had "experience" in these too
Deffo stay away from plug and play tuning boxes. Do a google search and you will find out why. A proper remap is the only way forward.
Dont slate them mate, there are some really good ones out there but they are expensive! Me car done 190 Bhp on stock 150 Bhp engine with just a PSI Motorsport chip (i have the AMD printout). This is not a plug-in box but it goes into the ECU and triggers the advance solenoid + the quantity adjuster. Also the Steinbauer P-Box does exactly what they claim up to 40 Bhp/50Nm on a stock motor. Custom tuning is hard to get in uk Diffas, as you might know ! I have yet to meet someone who really know to "custom" tune a v6 tdi in uk ! Most geeks know how to flash a tune with a good tool but very few understand that engine in order to maximise its potential...and to take in consideration mods !
V6 isn't soo popular within the modding world here ! And as i say, there are not many overhere who really know how to tune these engines... I will go to Netherlands next week to pick 2 sets of race 683 Bosio nozzles, drove fjtwelve a6 the other day and it puls really well- harder than mine in 3rd gear. I have maxed out me nozzles allready and the car is running too lean. Thing is i would like to tune my car by myself but i dont feel confident enough to tackle the job myself and i dont wanna brick my ecu ! I had tried once to upload a map onto a friends car with a kwp2000+ interface and i have managed to upload mp3 files (!) onto the ecu ! Cost me dear that experience so i let the professionals do it !
Yea well. I've new dynosheets;

277/1.6bar and 267/1.5bar. We really needed to drop iq above 4000rpm because the emp is getting really high (2.5bar).
But I think it's really good for that small turbo I have, gt2060v - means e61 beemer 30d wheels inside the stock turbo.
Little video too;
Audi A4 2.5tdi dyno 203kw 570nm - YouTube

Last time I posted the problem with the idle - turned out it was bad nozzles. Now runs pretty smooth.
Impressive ! Well done... What's the full spec on your lump ?
Nothing that much. All parts are almost stock, even they are from different engines.

-base engine 150hp AKN
-ported/cleaned heads BDG
-pistons from AKE
-stock/hybrid turbo with wheels: 44.5x60comp / 50x45turbine (from e61 bmw)
-fuel pump with AKE distribution head
-nozzles from cummins 5.9l cr
-autobahn 1.8t fmic kit
-SRE-clutch kit
-3bar map
i've got a 2.5 Quattro, and i've found a "localish" company called remap wizard, who'll get my 150, upto 187 for a sniff under £200, but is it worth de-catting 1st, and if so how do i do it, as i can't find any de-cats at all,
also is it worth putting a air filter on the car (i've seen a pipercross viper kit, NEW at a really silly price (so much so, i think it's an error ) :D
finally i've mailed that many people about remapping, can anyone tell me where does a map and a before and after rolling road.
Many Thanks
ah right, ok, thanks, jus thought this £200 filter was good, hehehee, guess i'll stay STD then.... Actully how do performance PANEL FILTERS rate??
Spend your money on a better turbo, the gt2052 from the 180Bhp drops right in ! The allroad v6 tdi injectors are the biggest fitted by the factory so they are good for about 220 Bhp. More than that and you'll need to go aftermarket: Bosio, Iveco, Cummins,etc.
Why drop in 180hp version? It's the same as 150hp version. Wasting your money. All the nozzles are same flowrate - old ones
have 5x0.18mm and newers 6x0.16mm holes, difference is in pumps / ecu iq-rate. You will have same output power with 150hp
and 180hp engines, 180hp and newer 2001-> engines usually have limited 52mg /str iq for some reason and therefore unable to
have more than 195-200hp output power.

Best way to tune it up is add cummins cr nozzletips, adjust them and add bigger turbo like 2056v or even with 60 comperssor.
Why drop in 180hp version? It's the same as 150hp version. Wasting your money. All the nozzles are same flowrate - old ones
have 5x0.18mm and newers 6x0.16mm holes, difference is in pumps / ecu iq-rate. You will have same output power with 150hp
and 180hp engines, 180hp and newer 2001-> engines usually have limited 52mg /str iq for some reason and therefore unable to
have more than 195-200hp output power.

Best way to tune it up is add cummins cr nozzletips, adjust them and add bigger turbo like 2056v or even with 60 comperssor.

Hey Diffas, I've contacted you over YouTube a long while ago, so if I sound familiar (doubt it), that's why.. I'm currently driving a 2004 B6 2.5TDI and am now finally looking into more performance. I've been reading, digesting and reading some more and I keep finding your answers to many topics. Now I'm reviving this 4-year-old gem, hoping to finally clear this last hurdle.

However, there are still doubts when it comes to the fuel pump. I have a BCZ engine (163bhp), and from what I've heard is that this pump is limited to roughly 220-ish bhp due to the IQ you've mentioned. Many other sources say that it's only on the AKE that there's a 2-plunger limited pump, so I'm currently in a big doubt as to what mine is (and, how I can find out). Additionally, no matter how or what I search, I can't seem to find anything to remedy the situation: who can remove the restriction, or what's there for me to do, to remove it if it's a physical restriction.. The car already has a full 3" stainless exhaust straight from the turbo (2,5" DP for about 4", then immediately 3" diameter), without any cat or muffler.

Your B5 has always been an example for me, so yea, you're kinda my idol so to say ;).
Oh dear. What a old topic. :)

These pumps are very mysterious. Pumps them selfs are not limited but but duration is limited. That means that you can bypass stock nozzle limits by changing bigger nozzles. So lets say most of the pumps
are "limited" to 52-54mg/stroke. That is just calculated duration value from IQ measuring solenoid. Every ms that solenoid is open means some mg of fuel. So lets say you get 200hp with 54mg/str and you switch to nozzles that are about 30% bigger. So with that same amount of duration you get 30% more fuel to cylinder in same time. In real life it is not that simple, but in matter of simplifying it is. Therefore you may expect 260hp with supporting mods. That sounds simple. Well it is and at the same it's not. This is the thing that grinds my gear very badly. With VCDS you are able to read your solenoid status, it works mostly between 20-80% value. With 80% value solenoid is reached it's maximum duration, so not that much power gain there after that. Thats how I've seen it. Like you said - it's like theres nobody who exactly know how these pumps work. I'm reaching 80% value with my current nozzles on 4800rpm with 39mg/str and 3800rpm with 43mg/str. 39mg/str is the maximum IQ for stock 150hp engine - so that is very confusing to me. My conclusion is that with really big nozzles filling "chamber" pressure drops and you need more duration from IQ solenoid to keep it up. I really don't know how it really works but this is some conclusion I have made.

So now you ask how come I'm having such a big power with these "+66%" nozzles. Of course there may be that the nozzles I'm having are bigger than they claimed. Other thing is that I've made some mechanincal changes to to vp44. As starter I believe AKN has smallest pump elements of all 2.5tdi engines. I've but bigger 3-plunger high pressure AKE elements to pump and adopted it on pump bench.
You are not able to do much with test bench - it passes or fails. You just need to input pump values you need to calibrate, so with bigger pump head pumps IQ was set very low and thats why I'm having
some rough idle. It's the same thing you have with vp37, that when you set basic IQ level as low you get you are able to have more fuel with same amount maximum IQ. I'm not that good with explaining but let me give some example. So lets say you have pump that has basic IQ 6mg/str and maximum IQ on revs 50mg/str, so there is actually 44mg/str increase in fueling. Then you have pump IQ set to 1mg/str and same 50mg/str you actually get 49mg/str fuel increase and thats 5mg more - more power. If you get my point? :)

Mainly there are not known options to remove pump ecu limits because the pump ROM is burned after successful pump test on the pump bench. Once it is burned - it stays there. Unless you erase it and burn again. Pumps itself are capable of big power for sure - see 800-1000hp cummins engines with vp44. Problem is how have full access and control over the pump.

Aaand what comes my current setup, it is working very nice. Even with the nozzles that are bit low quality and therefore bit too smokey for my taste. I'm pretty sure car has over 350hp after last mods and has less smoke than earlier with same ecu. I'm on the right direction. :)

I took one acceleration video few days ago with my "high fuel ecu":
Hoping to get better results on this season standing mile events. :)
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Thanks Diffas, and yea, it's old. But it is still one of the most relevant and most informative. Saw no reason to start yet another 2.5TDI topic.

That said, I think I'm catching your drift on your story. I know these pumps can (physically) deliver insane amounts of fuel, so I'm not worried about their actual performance. It's indeed the software. Plus, when you add different nozzles, you'll surely get different actual measurements than what the software thinks it's giving (if the pump + ECU think they're delivering 40mg/str with the stock nozzles, and you increase nozzle size, you actually get more mg/str, I'd think, hence messing up the readout values).

350 horses would be awesome, but I don't think that's feasible for me. I drive it for 30-40K km a year, and need it to run when I want to (it has a clean record of never failing on me, though costing quite a penny to maintain). I also do not have the funds to fix it "overnight" should it break down (conrod or pump failure), so I need it to remain somewhat safe. Pushing it, but not to the ragged edge. Anything between 250 and 300 is good enough, coupled with a fat 500-600Nm. The clutch will need replacement, though I won't do that until it starts to slip.

That said, I can't seem to find anything on the BCZ (2004) 2.5 TDI in terms of tuning (and what kind of pump I've got). I can probably get my hands on the proper nozzles and a turbo once I decide/find out what I need (I just can't afford to try 5 different kinds of nozzles ;) ). ECU remapping shouldn't be an issue - I work for XT Motorsport here in the Netherlands and we've got some close contacts with proper software guys.
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I would not to be worried about running big power and big kilometers. My car is on everyday use and used on my daily job so last year I run with it almost 40k. I've done+ 210k in 7 years, so know what I'm talkin about. :D

It's never good when you need to do some "tricks" to get fuel out, but in this case it is necessary evil. :)
Fair enough, it's just hard to get by the parts over here (especially when you want to keep it affordable). Job market isn't exactly flourishing at the moment either...

Thing is - my turbo has been replaced 120K km ago, and it's starting to whine slightly when cold. If I need to replace it, I'd rather do it with a better one for the same sort of money. My nozzles/injectors haven't been replaced or cleaned since day 1 (340.000 on the clock now), and the car's been running some sort of tune since factory. It's being taken care of, but it has had a working life; cruising at an easy 110 (55mph), but flooring it regularly, and especially in high gears (5 and 6).

Anything near 300 is preferred, anything over 300 is a bonus but no target. I tend to think that I'll be getting myself into all sorts of problems if I do.

I would sincerely appreciate any help/shopping lists/nozzle-injector tips to achieve the goal though, as you've obviously got more hands-on experience than most others.
Grave digging here. I have not been much on the forum lately but i want to make upgrade post to this thread. Last few years i have slowly building my b5 2.5tdi with three turbos compound setup. I have currently runnin just bit over 400hp and i believe there is lot of power left on table. My setup is is as runnin BW S362SXE as a low pressure turbo and twin K03-029 as high pressure turbos. Stock AKN 2plunger pump and used "cpc +90% over stock nozzles (at least claimed). Custom grind camshafts and slight mods on the heads but still runnin same heads what i put back in the days 2011 or so. I think they really needs to be ported properly. I run it on 3.7-3.8bar of boost to keep lamba/smoke level down. I think it is the quality of the nozzles that give some smoke even lambda is 1.4-1.45 on full power.
Heres is my latest dyno.

and the youtube video:

I only managed to get few runs last summer. First and only 1/4 was 12.7 / 180kmh. That was only time I was able to run quarter, mostly we have 1/8mile here. That 12.7 was 8.3s on 1/8th and best 1/8th i had later was 8.08 so i think 12.4-12.5 is totally possible. Probably going to increase power a bit and try to go 11s. Here is video collection of the quarter and 8th pulls.

Incar video of some street racing...thats with the ~390hp:
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Little update here too. Made some fueling upgrades and minor turbo upgrades on the wintertime. Did visit the same dyno to see comparable results.
This time it was pretty decent power gains. Unfortunately car went to limp on the dyno but nevertheless it reached 469hp (4800rpm)/768nm(3800rpm). On the road i didnt not notice the problem but on the dyno when you max out map sensor long time it goes to limp mode. On the road you are only few secods on the gear so it never goes to limp. This combo spools faster than previous and 650nm is usable from 2800rpm onwards. This is the mid rpm pull from 3000 to 4800 (when the limp mode hit). 4bar of boost, lambda 1.5+, egt max 750c.