Modifying a Diesel

[Welshbeef]

With petrols the route to more power is simple and commonly known but diesels? To me all I ever hear about is remap and that is it are there any other ways to modify a diesel?


Also what would a STD stage one stage two stage three modification to hype power?

I have heard of a Fabia vRS with nearly 300bhp out of a 1.9 vag unit but that is the only one. Which is good going from a 130bhp STD unit but if you started with a much bigger unit and power tp start with the absolute final position would be notably higher.

Really interested in hearing what the ph knowledge is on this and please no dagadaga or just buy a petrol nonsense. If you have any such posts please don't add to the thread as this is not s diesel v petrol thread in anyway just about diesel modification.

[XitUp]

http://www.bankspower.com/

[Howitzer]

I tweaked the pump on my Land Rover Defender and it made it a far nicer drive, not huge amounts of extra power but a noticeable difference.

I can't stand smokey diesels, it's not done well imo and just done for more power, it looks ridiculous.

The power you can get out of the american light truck engines though is incredible....

http://www.youtube.com/watch?v=QKUACSlIRCU

http://www.youtube.com/watch?v=BAJVJTNTLWM&fea...

Dave!

[PaulG40]

Don't know too much about tuning diesels although a lad on clubgti changed his engine to a 150 in a fabia and started there, don't know power and torque but it shifts!

Lloyd Allard (Allard Intercoolers) is a good person to know about tuning diesels, his road Sear cupra was 450lb/ft at one point.


Only thing I do know is clutch needs to be uprated and possibly conversion to a single mass flywheel as it'll kill a dual
Mass one.

[StottyZr]

I never see FMIC's on diesels, is there a reason for this? (common sense would tell me diesels aren't effected by air temps like petrols are but this is a guess )

[Welshbeef]

I find it really interesting that when it comes to diesel modification I have only ever heard of mapping the BMW diesels. This of course is a very cheap modification at c£500. Take my 330d as an example a remap can increase power from 231bhp up to 306bhp which clearly is a very substantial increase but what else can you do? Or is it a case of the cost is prohibitive and therefore it's just financial sense to go for the remap and then you don't really need anymore..... But what if you do want more?
I mean what's the max usable power I could get out of my engine??

[Sir J Savile]

Propane.

[XitUp]

Pretty much whatever you can do to tune a petrol turbo engine, you can do to a diesel turbo engine.

People tend not to do it because the limited power band doesn't really make a fun car to drive.

Look at some of the yank trucks with HUGE turbos on them, they make crazy power.

[anonymous-user]

The only really fundamental diffence is that on a CI engine the fuels flame front moves slower (as the fuel is less volatile). This limits the maximum rpm at which the engine can make peak power (because you must have finished burning all the fuel before a certain point in the power stroke). Hence on a SI engine, you have 2 routes to making more power either 1) increase the torque by using say a turbocharger to increase the airflow, or 2) increase the rpm at which the torque is maximised (i.e. cam change etc to move torque up the rev range)

On a CI engine, you can only increase power by increasing torque at a fixed rpm. This means that any tuning you do is really about getting the maximum charge density. Hence, normal routes of increased boost, less back pressure, reduced intake losses etc all work.

The inital "big win" for diesel tuning (and one which all the aftermarket tuners use) is to remove the "smoke limitation" mapping from the calibration (especially at low rpm before the turbo can catch up and ensure an excess air condition) OEM's are forced (through emissions limits and visible tailpipe smoke concerns) to run lean, even at WOT. Aftermarket tuners simply remove the smoke limit, and then the basic WOT fuelling target gets applied at all rpm's/airflows, moving the mixture rich and producing significantly more power.

Eventually, if you really don't care about smoke, you end up like these Drag diesels:

http://www.youtube.com/watch?v=XUQ2rtm7axQ ;-)

All the normal tuing methods like port flowing, compression ratio increase, valve size increase, etc etc all work, but are very expensive compared to just hooking up a laptop and flashing in a cal that adds 15% more fuel everywhere!

(also, port mods are very difficult to do, because modern diesels have multiple intake ports and are incredibly sensitive to charge movement (designed to keep the injected fuel in highly turbulent zone)

Also for clarity, diesels are affected by intake charge temperature like gasoline engines, but because you only inject the fuel as you want to burn it, they do not suffer any detonation or pre-ignition effects, and as a result, the drop in BMEP vs intake charge temperature is approximately 70% to 40% smaller than for a gasoline engine.

Edited by anonymous-user on Saturday 3rd September 10:13

[soda]

It can be done but would cost a fortune. Same idea as a turbo petrol engine, more air and fuel in equals more power. The torque involved wouldn't be long in killing most gearboxes/diffs though. As an example an older 330d with 184bhp as standard will most likely get a rumbly diff over 240bhp, it could take more even without changing very much but the drivetrain wouldn't handle it.

Bigger turbo and injectors, bigger intercooler, free flowing exhaust. I recall reading a piece recently about a Scandinavian Merc, 450bhp with the turbo off a Scania. Older engine though so a bit simpler wiring wise but I'm sure some serious drivetrain work was also needed.

[Welshbeef]

Given the fact on my car the exact same autobox is used for the 335d does that mean then there is zero risk gearbox wise in upgrading the 330d to 335d outputs?

I'm guessing that the 335d's bigger turbo is infact the same as the 330ds single turbo but with wick turned up?

[Cemesis]

Lots of mapping of VAG stuff (Audi, VW, Skoda and Seat) out there. Plus using parts from the 150 and 170 in the lower power version to bring it up.

I recently got an Arosa 1.4TDI with 75bhp and a £199 map takes that to over 100bhp and 200Nm.

[NHK244V]

StottyZr said:

I never see FMIC's on diesels, is there a reason for this? (common sense would tell me diesels aren't effected by air temps like petrols are but this is a guess )

It's cos your not looking ?
mondeos deffo have em cos i just changed one along with a front bumper, a fair few ealyer TD's have top mounted ones mainly cos they were added to a non turbo shell later inproduction as the manufacurer tweaked the diesel performance.
search for the derv doctor or look here http://www.tdocuk.com/index.php
the mod on that forum write for PPC.

Edited by NHK244V on Saturday 3rd September 15:05

[redgriff500]

Very basically you add more fuel as they all run lean.

When you get black smoke (too much fuel) add air (up the boost)

The limits as with petrols are clutch, gearbox and engine failures.

All tend to fail with TORQUE not bhp.

None have a set breaking point so it depends how lucky you feel.

Best place for info is the specific model forum you are interested in as its all been done before.

My Transporter started as 104bhp and is currently at dyno proven 148bhp running bio on all std components. I'm happy at that although others are running close to 200bhp but have spent a LOT more.

Edited by redgriff500 on Saturday 3rd September 15:12

[Welshbeef]

I'd be quite interested to see how say a 3ltr tdi does with a twin turbo setup sequential but a small turbo to start with then a scania truck massive turbo to kick in at 2000rpm full boost.

I'd imagine it would be very very big bhp numbers.

[maniac0796]

Common rail turbo diesels are quite easy to get big gains out of, most of that being in a remap, which will alter the pressure the wastegate opens, possibly up the injection duration and fuel pressure.

Mechanically, blocking off your EGR valve will help, as that means more exhaust gas is going to the turbo, and that the engine isn't loosing oxygen. Bigger turbo, injectors and intercooler can all help. Opening up the inlet and exhaust to get better volumetric effecieny can help aswell.

I'd say it's easier to get large gains from small money out of a common rail turbo diesel than any petrol car. N/A petrol cars require cams, cylinder heads and all sorts throwing at them, and turbo petrols are usually working on a razors edge with stock internals. But these diesels just take it.

[redgriff500]

Welshbeef said:

I'd be quite interested to see how say a 3ltr tdi does with a twin turbo setup sequential but a small turbo to start with then a scania truck massive turbo to kick in at 2000rpm full boost.

A huge turbo will cut in closer to 3-4k rather than 2k.

My standard turbo only comes into effect at 2k

[Welshbeef]

redgriff500 said:

A huge turbo will cut in closer to 3-4k rather than 2k.

My standard turbo only comes into effect at 2k

But a scania 12ltr only revs to 1,500 revs max

[Old Gregg]

Welshbeef said:

But a scania 12ltr only revs to 1,500 revs max

I think you might find you're a little bit out there.

[Zwoelf]

Welshbeef said:

I'm guessing that the 335d's bigger turbo is infact the same as the 330ds single turbo but with wick turned up?

No. It isn't.

Welshbeef said:

I'd be quite interested to see how say a 3ltr tdi does with a twin turbo setup sequential but a small turbo to start with then a scania truck massive turbo to kick in at 2000rpm full boost.

This is effectively what it is.

Welshbeef said:

I'd imagine it would be very very big bhp numbers.

Not particularly, big torque numbers, but power is limited by the max rpm capabilities/limitations of a diesel engine. As you tune diesels, the amount of torque tends to be where the gains are most made, however - limited by lower rpm limits the more the power goes up, you can end up with big outputs - but only available over a narrow band.

313PS (309bhp) & 464lb ft for the current 335d/535d/640d/740d/X5 and X6 3.5d I think.

Which is fine for efficiency for an engine that runs at a constant speed putting out peak torque constantly, but at odds with generally accepted and enjoyed notions of sportiness. That's why big trucks, boats and trains employ powerful diesel engines, it's the right type of engine for the right application.

For sportier driving, enthusiasts tend to favour a good amount of usable torque that builds progressively to peak power near to or at the top of the rpm band to allow for responsive performance over a wide range of engine and road speeds via suitably chosen and well spaced gear ratios. Which takes you back to a powerful large-ish capacity NA petrol engine...

I wondered how many posts it would take you to get from a serious diesel tuning thread to working a mapped 335d into the equation. Hilarious, as ever.