Diesel tuning tech
Discussion
The proper kind, I'm not talking just a remap...
I have an 05 plate 320d and I'm on the quest for more power, it's already remapped so I'm looking for the next step.
Today I have spoken to a well known turbo company and agreed that we can sort a hybrid turbo of some description out, the spec of which is unknown at present as I'm yet to supply a unit to work with.
Now, after this, I'm a little stuck.
My brother in law has a golf anniversary tdi with 240bhp and 380lb/ft and he has an egr delete pipe. Does anyone know the reasoning behind this?
I'm thinking that with a better turbo, a larger intercooler and a free flowing exhaust with no cat, I'll be looking at similar power but I can't find anyone who has bothered tuning 2/3rds or a real BMW engine with the wrong fuel!
Any hints or tips would be appreciated.
I have an 05 plate 320d and I'm on the quest for more power, it's already remapped so I'm looking for the next step.
Today I have spoken to a well known turbo company and agreed that we can sort a hybrid turbo of some description out, the spec of which is unknown at present as I'm yet to supply a unit to work with.
Now, after this, I'm a little stuck.
My brother in law has a golf anniversary tdi with 240bhp and 380lb/ft and he has an egr delete pipe. Does anyone know the reasoning behind this?
I'm thinking that with a better turbo, a larger intercooler and a free flowing exhaust with no cat, I'll be looking at similar power but I can't find anyone who has bothered tuning 2/3rds or a real BMW engine with the wrong fuel!
Any hints or tips would be appreciated.
It isn't as popular here, but hugely popular in Europe, especially Portugal where the kids tend to go for diesels.
Bigger turbos will help to increase your headroom, but the power comes from the amount of diesel injected (Injection quantity /IQ)
For diesels, you can pretty much forget anything you have learned about petrol tuning, it is easier to reverse your considerations of fuel and air.
ie, on a petrol car, get more air in, the ECU will handle the fuel and make more power.
Diesels control power by varying the amount of fuel, and not varying the amount of air.
Now your ECU works in Nm of torque. It starts by the pedal position, and the engine RPM and works out how much torque to make.
Other tables limit the amount of torque in different gears at different RPMs, a torque conversion table calculates what IQ to inject to make that particular torque level, and a lambda map tells the car if it is OK to use the full amount and not produce black smoke.
Just fitting a bigger turbo will allow more boost (provided the ECU doesn't move the vanes about to reduce it) which means more air, and less of a chance of hitting the lambda map limits (commonly called the smoke map)
The original injection limits and torque limits will still be inplace.
When they are being tuned for big power, you might need bigger nozzles/injectors too, to make sure you can supply the fuel needed for the power. A larger turbo and intercooler to keep temps down, and also monitoring EGTs so the turbo doesn't melt.
Bigger turbos will help to increase your headroom, but the power comes from the amount of diesel injected (Injection quantity /IQ)
For diesels, you can pretty much forget anything you have learned about petrol tuning, it is easier to reverse your considerations of fuel and air.
ie, on a petrol car, get more air in, the ECU will handle the fuel and make more power.
Diesels control power by varying the amount of fuel, and not varying the amount of air.
Now your ECU works in Nm of torque. It starts by the pedal position, and the engine RPM and works out how much torque to make.
Other tables limit the amount of torque in different gears at different RPMs, a torque conversion table calculates what IQ to inject to make that particular torque level, and a lambda map tells the car if it is OK to use the full amount and not produce black smoke.
Just fitting a bigger turbo will allow more boost (provided the ECU doesn't move the vanes about to reduce it) which means more air, and less of a chance of hitting the lambda map limits (commonly called the smoke map)
The original injection limits and torque limits will still be inplace.
When they are being tuned for big power, you might need bigger nozzles/injectors too, to make sure you can supply the fuel needed for the power. A larger turbo and intercooler to keep temps down, and also monitoring EGTs so the turbo doesn't melt.
I have dabbled alot with high power diesel tuning on the VW V10 diesel engine (2 valve per cylinder) that ran in the back of a Radical in the ALMS a few years back, and fitting a bigger turbo and runnign big boost pressures will get you so far then you will hit a brick wall as the cylinder head will just choke the mass-flow of air through the engine, no matter how high you wind up the boost pressure.
The intake ports of a diesel are notoriously restrictive, weather its a 2 or 4 valve head, as they are designed to generate a medium-to high amount of in-cylinder swirl, which is essential for the re-entrant combustion bowl combustion process to work properly........ when your going for high power plan to:
1) go for a "medium" porting job on both the inlet and exhaust ports, this will work just fine, you will reduce the swirl a little, but the mass flow will increase by about 20%
2) Have the valves cust with 3 angles on the seats.
3) Get your cams re-ground for another 1mm of lift and a about 10-20 degrees more duration, take real care of the tip clearances to the piston crowns, 1.5mm is considered a minimum, this will giva another 10-20% of mass flow.
4) aim for a compression ratio in the region of 16:1 when targeting over 100bhp/litre, I suspect your engine will currently be about 18:1, this will be too high and the engine will run way too hot ......
as a guide the LeMans diesels are running in the region of 14:1.......you reduce the compression ratio by taking about 0.5-1mm off the omega style or re-entrant combustion bowl.......if your CR is too high, expect to melt or smash your cast aluminium pistons into small pieces and wreck your engine.......best bet is to probably get some 16:1 pistons from the later BMW 2.0 200bhp I4 motor, that will be much cheaper and easier.
I cant believe you are the first person to do this therefore I suspect someone out there is probably offering a bolt-on cylinder head with all the above already done. Personally I would not fit bigger nozzles until you really need them, generally speaking turbo diesels will happily run at a very high air to fuel ratio, so you cannot "lean" them out like a gasoline engine and damage them.....if you fit big nozzles straight away with poor mass flow of air then all you will do is just belch black plooms of smoke everywhere, as its basically un-burnt fuel.......you will be pleasantly surprised how much a standard nozzle will flow when you do start tuning.
On the V10 VW ALMS Radical engine we were making 550bhp and still used the standard nozzles rated for the base engine which was 300bhp.
The intake ports of a diesel are notoriously restrictive, weather its a 2 or 4 valve head, as they are designed to generate a medium-to high amount of in-cylinder swirl, which is essential for the re-entrant combustion bowl combustion process to work properly........ when your going for high power plan to:
1) go for a "medium" porting job on both the inlet and exhaust ports, this will work just fine, you will reduce the swirl a little, but the mass flow will increase by about 20%
2) Have the valves cust with 3 angles on the seats.
3) Get your cams re-ground for another 1mm of lift and a about 10-20 degrees more duration, take real care of the tip clearances to the piston crowns, 1.5mm is considered a minimum, this will giva another 10-20% of mass flow.
4) aim for a compression ratio in the region of 16:1 when targeting over 100bhp/litre, I suspect your engine will currently be about 18:1, this will be too high and the engine will run way too hot ......
as a guide the LeMans diesels are running in the region of 14:1.......you reduce the compression ratio by taking about 0.5-1mm off the omega style or re-entrant combustion bowl.......if your CR is too high, expect to melt or smash your cast aluminium pistons into small pieces and wreck your engine.......best bet is to probably get some 16:1 pistons from the later BMW 2.0 200bhp I4 motor, that will be much cheaper and easier.
I cant believe you are the first person to do this therefore I suspect someone out there is probably offering a bolt-on cylinder head with all the above already done. Personally I would not fit bigger nozzles until you really need them, generally speaking turbo diesels will happily run at a very high air to fuel ratio, so you cannot "lean" them out like a gasoline engine and damage them.....if you fit big nozzles straight away with poor mass flow of air then all you will do is just belch black plooms of smoke everywhere, as its basically un-burnt fuel.......you will be pleasantly surprised how much a standard nozzle will flow when you do start tuning.
On the V10 VW ALMS Radical engine we were making 550bhp and still used the standard nozzles rated for the base engine which was 300bhp.
Edited by knighty on Thursday 6th October 16:17
Edited by knighty on Thursday 6th October 16:18
TheEnd said:
It isn't as popular here, but hugely popular in Europe, especially Portugal where the kids tend to go for diesels.
Bigger turbos will help to increase your headroom, but the power comes from the amount of diesel injected (Injection quantity /IQ)
For diesels, you can pretty much forget anything you have learned about petrol tuning, it is easier to reverse your considerations of fuel and air.
ie, on a petrol car, get more air in, the ECU will handle the fuel and make more power.
Diesels control power by varying the amount of fuel, and not varying the amount of air.
Nonsense. All IC engines rely on the amount of air they process to produce power. You have a very limited understanding of how engines work if you can post stuff like this.Bigger turbos will help to increase your headroom, but the power comes from the amount of diesel injected (Injection quantity /IQ)
For diesels, you can pretty much forget anything you have learned about petrol tuning, it is easier to reverse your considerations of fuel and air.
ie, on a petrol car, get more air in, the ECU will handle the fuel and make more power.
Diesels control power by varying the amount of fuel, and not varying the amount of air.
330d? 
Blanking off your EGR might release a bit more power, but bear in mind that it's only really open at cruise/idle, so when you want real power, it'll shut off. But it is potential exhaust gas that could be spinning the turbo being wasted, and it's potential oxygen that could be burnt being replaced by exhaust gas.
Straight through exhaust. Not going to be excessivly loud on a turbo diesel. If it is, then you'll want to get a box which has a perforated straight through pipe in it, and surround it with wadding. Get rid of DPF's and all that (dunno if these have them), you want exhaust gas to be able to get away as quick as possible, bar the turbo.
Blanking off your EGR might release a bit more power, but bear in mind that it's only really open at cruise/idle, so when you want real power, it'll shut off. But it is potential exhaust gas that could be spinning the turbo being wasted, and it's potential oxygen that could be burnt being replaced by exhaust gas.
Straight through exhaust. Not going to be excessivly loud on a turbo diesel. If it is, then you'll want to get a box which has a perforated straight through pipe in it, and surround it with wadding. Get rid of DPF's and all that (dunno if these have them), you want exhaust gas to be able to get away as quick as possible, bar the turbo.
Pumaracing said:
TheEnd said:
It isn't as popular here, but hugely popular in Europe, especially Portugal where the kids tend to go for diesels.
Bigger turbos will help to increase your headroom, but the power comes from the amount of diesel injected (Injection quantity /IQ)
For diesels, you can pretty much forget anything you have learned about petrol tuning, it is easier to reverse your considerations of fuel and air.
ie, on a petrol car, get more air in, the ECU will handle the fuel and make more power.
Diesels control power by varying the amount of fuel, and not varying the amount of air.
Nonsense. All IC engines rely on the amount of air they process to produce power. You have a very limited understanding of how engines work if you can post stuff like this.Bigger turbos will help to increase your headroom, but the power comes from the amount of diesel injected (Injection quantity /IQ)
For diesels, you can pretty much forget anything you have learned about petrol tuning, it is easier to reverse your considerations of fuel and air.
ie, on a petrol car, get more air in, the ECU will handle the fuel and make more power.
Diesels control power by varying the amount of fuel, and not varying the amount of air.
The accelerator directly controlling the fuel quantity? Diesels varying their power by different fuel quantities?
If you put a bleed valve on a petrol turbo, you will most likely get more power.
More boost, more air, ECU adds more fuel, job done.
Try the same on a diesel and not much will happen unless you have been clipping the lambda / air-fuel calibration map.
It's going to be a lot harder, as they don't run at a set pressure.
The pressure varies with engine speed and load, and the ECU then has to use another table to work out the injector opening times to get X mg's of fuel for a certain pressure.
All of the ECUs I have seen have this as a table that is made and calibrated, so they don't calculate what to do, they look up pre-programmed data instead.
It's looking unlikely there will be one number you can just change, and it'll suddenly work with new injectors, you'd need to fit them, and remake the table.
The pressure varies with engine speed and load, and the ECU then has to use another table to work out the injector opening times to get X mg's of fuel for a certain pressure.
All of the ECUs I have seen have this as a table that is made and calibrated, so they don't calculate what to do, they look up pre-programmed data instead.
It's looking unlikely there will be one number you can just change, and it'll suddenly work with new injectors, you'd need to fit them, and remake the table.
Pumaracing said:
TheEnd said:
It isn't as popular here, but hugely popular in Europe, especially Portugal where the kids tend to go for diesels.
Bigger turbos will help to increase your headroom, but the power comes from the amount of diesel injected (Injection quantity /IQ)
For diesels, you can pretty much forget anything you have learned about petrol tuning, it is easier to reverse your considerations of fuel and air.
ie, on a petrol car, get more air in, the ECU will handle the fuel and make more power.
Diesels control power by varying the amount of fuel, and not varying the amount of air.
Nonsense. All IC engines rely on the amount of air they process to produce power. You have a very limited understanding of how engines work if you can post stuff like this.Bigger turbos will help to increase your headroom, but the power comes from the amount of diesel injected (Injection quantity /IQ)
For diesels, you can pretty much forget anything you have learned about petrol tuning, it is easier to reverse your considerations of fuel and air.
ie, on a petrol car, get more air in, the ECU will handle the fuel and make more power.
Diesels control power by varying the amount of fuel, and not varying the amount of air.
Pumaracing said:
Nonsense. All IC engines rely on the amount of air they process to produce power. You have a very limited understanding of how engines work if you can post stuff like this.
But you need to add the fuel to go with the air as well, just pumping more air into a diesel won't achieve much, if anything.Robmarriott said:
That's a pain then!
I should have just bought a car with a rotary diesel pump!
There will be quite an amount of headroom in the injectors, and also you can bump up the rail pressure by 100bar too without any problems.I should have just bought a car with a rotary diesel pump!
Regular remapping and a decat pipe should get you to about 200bhp.
Seems like it's time to add an article on tuning diesel engines to my website. Right you 'orrible lot, sit quietly and pay attention. There's no fundamental difference in what you need to do to gain power from either a petrol or diesel engine. There's certainly no need to "reverse your considerations of fuel and air." All engines can be considered as "air limited", in other words with the correct modifications to the fuel system you can squirt in as much fuel as you want but the basic engine design limits how much air it can process and without more air you can't burn more fuel.
To process more air the same modifications work in almost exactly the same way whether the engine is a petrol or a diesel. Bigger valves, properly modified ports, longer duration higher lift cams, more turbo boost. In both cases once the modifications to process more air have been made then it's necessary to adjust the fuel system to add the appropriate amount of extra fuel. In fact both petrol and diesel fuel have almost exactly the same stoichiometry which is the technical term for the theoretical ideal amount of fuel that needs to be added to a given amount of air for complete combustion. For petrol engines the theoretically ideal air/fuel ratio by mass is about 14.6/14.7 and for diesels it's about 14.5.
In practice petrol engines give a bit more power with richer mixtures than stoichiometric and hence at full throttle they ideally run at about 12.6-13.0 air/fuel by mass. In practice diesel engines start to belch black smoke as you approach the stoichiometric point so they are usually constrained to run a bit leaner than that on the road at full power but if you can put up with the smoke then you will also gain a bit more power as you go richer. Try looking up a few tractor pull videos on Youtube and see how those engines behave - if you can see them through the smoke.
Because diesel engines are not "throttled" i.e. they have no butterfly valves to control the air supply like a petrol engine and always run with complete cylinder filling they respond very well to cylinder head mods. With no carb or throttle bodies to further restrict the air intake, diesel engines see the full gain from any improvement in cylinder head breathing that can be obtained. Obviously it might also be necessary to enlarge the intake manifold and any other pipework to and from the air filter to match what's been done to the cylinder head.
Because diesel engines only run at comparatively low rpms there's a limit to how much you can increase cam duration compared to what a petrol engine will tolerate. For standard engines the durations are very similar but a full race petrol engine might have 20% more cam duration than stock whereas a diesel one will probably only cope with 5% or at most 10% extra duration. For road engines it's probably best to leave this factor alone. Also because diesel engines have a very high compression ratio this means the pistons get very close to the valves and it's not usually easy to add much more cam lift or duration without unpleasantly expensive consequences.
So you end up with a fairly easy tuning decision. With no carbs or TBs to worry about and cam changes not being very productive you concentrate on the cylinder head and turbo boost. For substantial power gains you will also probably need to improve the exhaust system to match the extra flow the engine is processing. Because most diesel engines have fairly small valves compared to petrol engines there's usually very good scope for fitting larger ones and porting the head to suit. Many moons ago I got involved with tuning an old Mk 2 VW Golf 1600 diesel and after fitting bigger valves on larger seat inserts, porting the head properly and upping the turbo boost we doubled the power from 70 bhp to 140 bhp which meant it showed a clean pair of heels to most of the similar sized petrol engines in fast road tune like XR2s and 2 valve petrol Golfs. It would also still get the best part of 50 mpg in general use because diesel engines are so efficient in cruise mode and are always running with complete cylinder filling. There are very few petrol engines you can double the power on for road use without massively expensive surgery and without also compromising their road manners and fuel consumption.
I have to admit I rather like diesel engines and their scope for tuning without sacrificing fuel economy and if it wasn't that I've already decided to run my 2001 2.0 Focus ESP until either it or I die first I might even buy one. My money is on the Focus outlasting me as it happens.
Read and inwardly digest the third post in this thread again. I pretty much agree with what was said in it which is fairly unusual on this forum. Well done that man.
To process more air the same modifications work in almost exactly the same way whether the engine is a petrol or a diesel. Bigger valves, properly modified ports, longer duration higher lift cams, more turbo boost. In both cases once the modifications to process more air have been made then it's necessary to adjust the fuel system to add the appropriate amount of extra fuel. In fact both petrol and diesel fuel have almost exactly the same stoichiometry which is the technical term for the theoretical ideal amount of fuel that needs to be added to a given amount of air for complete combustion. For petrol engines the theoretically ideal air/fuel ratio by mass is about 14.6/14.7 and for diesels it's about 14.5.
In practice petrol engines give a bit more power with richer mixtures than stoichiometric and hence at full throttle they ideally run at about 12.6-13.0 air/fuel by mass. In practice diesel engines start to belch black smoke as you approach the stoichiometric point so they are usually constrained to run a bit leaner than that on the road at full power but if you can put up with the smoke then you will also gain a bit more power as you go richer. Try looking up a few tractor pull videos on Youtube and see how those engines behave - if you can see them through the smoke.
Because diesel engines are not "throttled" i.e. they have no butterfly valves to control the air supply like a petrol engine and always run with complete cylinder filling they respond very well to cylinder head mods. With no carb or throttle bodies to further restrict the air intake, diesel engines see the full gain from any improvement in cylinder head breathing that can be obtained. Obviously it might also be necessary to enlarge the intake manifold and any other pipework to and from the air filter to match what's been done to the cylinder head.
Because diesel engines only run at comparatively low rpms there's a limit to how much you can increase cam duration compared to what a petrol engine will tolerate. For standard engines the durations are very similar but a full race petrol engine might have 20% more cam duration than stock whereas a diesel one will probably only cope with 5% or at most 10% extra duration. For road engines it's probably best to leave this factor alone. Also because diesel engines have a very high compression ratio this means the pistons get very close to the valves and it's not usually easy to add much more cam lift or duration without unpleasantly expensive consequences.
So you end up with a fairly easy tuning decision. With no carbs or TBs to worry about and cam changes not being very productive you concentrate on the cylinder head and turbo boost. For substantial power gains you will also probably need to improve the exhaust system to match the extra flow the engine is processing. Because most diesel engines have fairly small valves compared to petrol engines there's usually very good scope for fitting larger ones and porting the head to suit. Many moons ago I got involved with tuning an old Mk 2 VW Golf 1600 diesel and after fitting bigger valves on larger seat inserts, porting the head properly and upping the turbo boost we doubled the power from 70 bhp to 140 bhp which meant it showed a clean pair of heels to most of the similar sized petrol engines in fast road tune like XR2s and 2 valve petrol Golfs. It would also still get the best part of 50 mpg in general use because diesel engines are so efficient in cruise mode and are always running with complete cylinder filling. There are very few petrol engines you can double the power on for road use without massively expensive surgery and without also compromising their road manners and fuel consumption.
I have to admit I rather like diesel engines and their scope for tuning without sacrificing fuel economy and if it wasn't that I've already decided to run my 2001 2.0 Focus ESP until either it or I die first I might even buy one. My money is on the Focus outlasting me as it happens.
Read and inwardly digest the third post in this thread again. I pretty much agree with what was said in it which is fairly unusual on this forum. Well done that man.
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