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Turbo upgrade / modification 200tdi


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Good evening all.

So I am after some of you wisdom or real time experience with regard to upgrading the standard 200tdi discovery turbo charger. Honest experiences if you please in the performance area V cost etc.

I am trying to decide whether or not to fit a VVT / VNT on to my current set up but have not found many testimonials to the positive but to be fair neither many to the negative.

My current set up is :-

Discovery 200tdi engine approx 150k miles

Double width intercooler (2x standard intercoolers welded end to end and re-piped)

Current turbo waste gate adjusted (18psi max, no movement in waste gate)

Boost diaphragm pin replaced with genuine bosch upgrade

Various tweaks to FIP (max fuel, non boost fuel, boost actuation rate)

285x75x16 BFG KM2 tyres

3.54 diffs

1.211 transfer box

So what will I gain or loose? Not looking for any more top end as 80-85mph is enough before things start to complain, expecting a more positive harder pull away with additional torque and less turbo lag.

Your thoughts please, regards Ash

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What's a Genuine Bosch Boost Pin Upgrade? Is it just a re-profiled boost pin?

Set it all back to standard.

Stage 2 head works

Mild tweak of the wastegate

Make intercooler flow a tadge better

12.00 to 12.30 on the diaphragm with some careful star wheel tweaks

Change the ring and pinions

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Different engines use a different profile pin depending on the required engine characteristics.

Nkk turbos ( I think ) offer a upgraded fixed vane turbo that looks like an interesting option with offers of a rolling road session also.


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VNT is win-win if you can make it work.

The turbo produces boost much lower down the rev-range giving less lag and a much wider power band.

Just need to take a look at the HS2.8 variant of the 300tdi to see the torque spread difference.

The trick is getting it to work well without ECU control!

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Has anyone actually tackled this successfully? I wouldn't mind a little challenge making a standalone vnt control ecu. Setting up a micro controller with a pressure sensor to drive a little solenoid using a PID control loop could be quite fun...

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honitionhobbit "What's a Genuine Bosch Boost Pin Upgrade? Is it just a re-profiled boost pin?" You are correct in your thinking, It is a genuine bosch pin with a different profile not a cheap unit from one of the shows.

I like the idea of some head work to allow better breathing and yes the intercooler could be more efficient but would this really effect low down torque before the turbo starts to work?

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Daan did some interesting research work on 'coolers - worth looking at; it's in the write up about his motor

I've been messing with 200's for years now - since '91

I reckon the biggest difference pound for pound was the head work. I also found that most of the 'classic' power fixes - like boost pins and too much pump tweaking (ooer) simply robbed Peter to pay Paul - you lost out lower rpm grunt but gained in mid and top range. This is exacerbated by over gearing - ie lobbing on a set of tyres that are 10% over standard in OD and the best part of 20% wider; and have a great rolling resistance due to being super grippy in the mud...

Hence the gearing suggestion. If you throw in a Defender T box it would be better - obviously not a 1.66 early box because then it will top out at 55mph, but a 1.44; or change the R&P's

Then take the engine back to standard settings - default if you like. Whip the head off and get it ported, valves re cut and ground. Whilst you can see inside, give it some love - maybe even go on to new rings, valve guides, stem seals etc. Once that's done, lose the boost pin and tweak the pump carefully and by the book - 15 minutes at a time. Road test it and mark the changes. You'll feel when you lose the bottom end response, then back off.

Big intercoolers are not the way to go - bigger than standard is cool. The best for a 200 seems to be the 300 plus 50% jobbie that Alisport do...

If you want more power then look at a Nitrous spray - massive power increase and easy to control

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Crumbs, I first read it as a technical excise in turbo upgrading.

Leave turbo alone, fit some 4.7 ring an pinions to get rid of that 13.5% increase in gearing your tyres have put in.

yes that's right, 13.5% increase in gearing from tyre size and then add the rest for rolling resistance etc, when we go laning I run 16/18 psi, this is optimum for traction and ground impact, but horrendous on fuel economy as any bits of black top can be really felt against normal 30 pound all round.

Follow the Hobbit!!! Old school head work and gas flowing gives far better driveability, yes it can be either expensive or time consuming, but in this day and age it's not attractive as it's not a bolt on solution like a VNT etc,. ie, no real resale vslue if you break it where as you could put the VNT up for 3/4 of what you paid and sell it same day, performance head might sit for months!

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In a turbocharged engine, theres little point messing around with "traditional" tuning like cylinder head work.

All the work you do on the cylinder head is easily replicated by a 1 or 2psi increase in boost pressure. Sure, if your trying to achieve MEGA power figures, you need both, but bang for buck tuning is more boost and more fuel. Adding a VNT will transform the engine way more than any head work ever will.

Why are you trying to suggest he should revert his fuelling modifications back to standard? All thats going to achieve is less fuel, and thus less power. Wind it up until it smokes, back off a bit. I've done exactly that to my isuzu motor, and it makes more power everywhere. It throws in so much fuel that if you floor it with the rpms too low (ie off boost) it chucks out clouds of black smoke, but that doesnt matter because fuel = power and gets everything moving faster. A diesel engine will make maximum power POURING out black smoke, but EGT's are typically too high for longevity at max load and it looks unsightly, so engines are tuned to run leaner at the expense of power. If your willing to put up with some smoke, more power is available. There should be no reason that turning up the pump somehow "steals" low end grunt. Whats more likely is the truck feels faster up top (because it is) and the same amount of low down power now feels lacking.

For the intercooler, fit the biggest one you can. Why on earth would you choose to fit a smaller one? You want the lowest charge temperature you can achieve, to get the most oxygen into the cylinders. Typically the space available limits the size anyway, but theres no advantage in not fitting the biggest one that will fit in the gap. It wont add lag, its a myth. The turbocharger is flowing hundreds of cubic feet of air per minute, you cant increase the size of the intercooler by enough to cause any lag, its internal volume is insignificant compared to the air the engine is consuming.

Changing the gears? Thats just going to make it annoying and revvy. Surely the whole point of fitting a 1.2 TB is to get the revs down and make the whole thing more comfortable and less ear-bleedy. Simply take a look at any road car with a bit of power, and you realise your not screaming down the motorway at 3000rpm. My 330d does about 1800rpm at 70. Its quiet and refined, it makes full boost at 1500rpm. If i want a shorter gear, i'll stick it in 3rd or 4th instead. If i want the car to go faster, i'll remap it, rather than driving around everywhere 2 gears lower than normal.

The advantage of the VNT system is it gets the turbo boosting earlier giving you more air (and thus the ability to add more fuel and make power) in the lower part of the rev range.

Theres a pre-existing microcontroller project to control a VNT turbo here:


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here we go again?

Can you tell me which of the fuelling adjustment screws on the Bosch VE pump "robs peter to pay paul"?

Because i've had a good olde play with mine, and none of them have that effect...

They all have a specific purpose. Some will give you more power when off boost, some will give you more power everywhere, and some will give you more power when on boost. But none of them will steal low down power and replace it with top end power as you suggested.

It makes sense ofcourse that the engine will produce more power up the top end. Thats just how engines work. And with a wastegated engine that doesnt produce proper boost until 2000rpm, thus limiting what you can do in the 1000-2000rpm range, the more you tune it, the bigger the step change gets at 2000rpm and thats where the VNT comes into its own. But your not removing low down power, you just start to notice the off boost zone more because its producing proportionally less power than the engine is once the turbo has spooled up.

The TGV engine produces maximum torque at 1400rpm, compared with the standard wastegated engine producing maximum torque at ~2000. That 600rpm difference makes a MASSIVE difference to how the vehicle drives, even without the fuelling screwed up to the max, simply by supplying far more air and thus allowing far more fuel and thus power to be produced at that part of the rev range.

Plenty folk have reported on how the TGV drives compared to the standard 300tdi, and plenty folk have reported on how the VNT upgrades for the TD5 have transformed it too. Why do you think they are all lying?

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I was referring to the standard 'fast response' I know better, he must be wrong attitude of some internet posters, using big long posts to prove the wrongness and rightness of differing opinion, rather than discuss what might or might not be right...

I can't be bothered to argue. I just can't. It's a new tactic I am trying on social media. Let the OP follow your guidance as you are obviously right and I am so obviously wrong.

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So your going to dismiss all his pre-existing modifications as junk, then try to blame me for being "one of those internet posters" for saying that i dont agree with you and explaining why?...

Boost pin upgrades are a common theme in Bosch VE tuning. Its a fundamental part of how the pump manages fuel enrichment for on boost fuelling, and is a common modification when running raised boost pressure or a different turbocharger, to better match the pumps fuel delivery to the new airflow. Its not an opinion. Its a part how the device works. If you dont get enough LDA enrichment, you end up having to turn up the max fuel screw instead, which dumps in extra fuel everywhere, much like i've done on mine. I didnt want to spend the money on an improved pin, and clocking the factory LDA pin to max position was not enough. So i cranked the max fuel instead and now it idles a bit high and puffs black smoke in certain conditions. An enhanced LDA pin is a far better way to increase the fuelling than using the existing adjustment screws on the pump.

His post was asking about the benefits of a VNT, and his requirements (more low down torque and less lag) exactly fit with what a VNT does, yet your telling him to remove the cylinder head and start doing very expensive porting/gas flowing operations on it instead? Something which, at best, will give very mild improvements to torque between 1000-2000rpm because theres no turbo boost down there, compared with the MASSIVE hike you'd get from a VNT turbo in the same region...

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Why the attitude, Hobbit? You've made some pretty glib statements and been called on them. Surely this is normal within what should be an informed discussion?

I have to agree with Aragorn: By what mechanism does changing the fueling at the top end have to adversely affect the bottom? I also agree that head work is unlikely to yield much gain at low revs, which is what the OP is asking for. It's a diesel engine, which means very conservative lift duration and very little or no overlap; it's not ever going to flow particularly well without a turbo packing the air in. Port match and equalise flows if you're feeling fussy, but leave it there and spend the money elsewhere. Making sure compression is tip-top with fresh rings, valve guides and lapping as suggested is a good place to start before moving on to pushing more torques ( ;) ) out of it, though. Otherwise you're into a lot of messing with the flow bench and dyno testing to check what you're doing is *actually* having a positive effect within the desired envelope - it's unlikely to be straightforward. Unless you can find someone that's done the work on that head design, has arrived at a good solution and has figures to back it, but I can't honestly see how any kind of porting could bring about the gains you'd find with a properly sized VNT turbo, which is why I'd be looking that direction. I notice there are various conversion kits available, though I'd be wary that the purely mechanical actuator actually gets best out of it compared to an electronic solution.

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Something ash hasn't pointed out is A. This set up is in his 88" bowler thus it's quite a bit lighter so can pull the gearing. & B. He used to work as a diesel engineer at a diesel specialist. So he does know his way round diesel engine/pump.


I disagree on gearing Mike! Now some back ground is coloured in I think 4.1 diffs, still think 3.54 too high for 200Tdi power train out of a Disco with the raise in gearing from the tyres!

My own Disco on std 235/70 16 tyres is plenty quick enough without running out of gears until I hit 80mph, I find even the 235/85 a tadje too tall for my own driving style, others just say wind the pump up and give it higher boost, 15psi at manifold(post intercooler) and just enough smoke to make me think twice about flooring it when blue lights are within good eyesight is enough for me.

Maybe if I take a eurobox in the new year then perhaps a full rebuild is on the cards?

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I will add my little here. I had a performance head on my 300tdi disco with with the big intercooler pump tweak, Turbo at 18psi and on 33's and it was great, Never running out of torque. They do work well. The only other thing I would have done to it would be fitting a vvt just to help get the revs going when towing.

Speaking to someone who had actually had his 90 on rolling road when fitting his boost pin and he said he gained 50lbf ft and lost 1bhp.

Fitting a fancy Turbo would be great, there just blooming expensive. I know of someone who fitted an Turbo off an Audi 2.5 v6tdi to his 200tdi and controlling it with a td5 actuator. That might be a cheaper option.

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VVT on a Tdi?

With the definition I've always applied to that it would be a fairly mammoth project, but interesting to see it done.

I can agree some with Mr hobbies sentiments.

Engine design is all about compromises, there's no magic bullet, and whatever you do there's a trade off somewhere along the line.

Of course, strapping a VNT on the side and blowing more air in will allow you to burn more fuel at lower revs, but it will have a knock on effect asides the increase in bottom end performance.

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To throw a left-field question in.... does the forum think that bolting a VNT to a TDI engine, that produces much more torque at much lower revs is going to end up knocking the big ends out the engine?

I'm sure the TDIs were only ever designed for getting the torque lump at 1800, if you move that down to 1200rpm, with lower oil pressure and flow, could this spell trouble?

Discuss :P

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Its a really good question and one of the reasons I've never wanted to try to extract too much extra power and torque out of a TDi. I reckon adding an extra cylinder and its extra bearings is a safer way if you want reliable power, say designing for 200K miles?

However for a weekend toy or weekend vehicle adding a bit more power with a turbo mod, well if it wears out quicker it doesn’t really matter in the great scale of things. Its typically already done 170K miles and in its new configuration may do another 20K miles so quicker wear isn’t the end of the world.

When I rebuilt my current 300 TDi it was showing a fair bit of wear in the bottom end bearings at 178K miles but that was a typical 'farm maintained' vehicle with tar for oil.

I wonder if Bowie69's question could be answered by determining what bottom end wear is like in most lumps at 200K miles of normal use?

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