I realised I have no idea about TDi tuning

[Mr MXT]

I was chatting to friend the other day who has fitted an FMIC to his L200 Warrior and wanted to know what performance gains he was likely to get from it. Now IMO, without a boost increase he won't spot any discernable power gains but thats by the by.

Here is an extract of the email I sent him: "Forgive me if im teach egg sucking: For a PETROL engine -- As you increase boost pressure, the intake gas is compressed more, making it hotter which increase charge (i.e. inlet gas) temperatures. This increases in cylinder temperatures which means the fuel can ignite before the spark. Basically as the piston is coming up the cylinder you get the BANG rather than when it is as top dead centre.

I’m thinking though its not the same for a derv as you don’t have a spark. The derv ignites because of the pressure in the cylinder and temperature increase. So I’m not sure!"

I'm pretty sure my thinking around detontation on a petrol engine is correct, and that running cooler intake temps allows you to run more boost - but does this have the same effect on a derv?

Confused of Milton Keynes

[lazy_b]

Mr MXT said:

I was chatting to friend the other day who has fitted an FMIC to his L200 Warrior and wanted to know what performance gains he was likely to get from it. Now IMO, without a boost increase he won't spot any discernable power gains but thats by the by.

...

I'm pretty sure my thinking around detontation on a petrol engine is correct, and that running cooler intake temps allows you to run more boost - but does this have the same effect on a derv?

Confused of Milton Keynes

I think you're right - but it's a bit more complicated than that.

It's all down to the different duty cycles between turbo petrol engines and turbo diesels. Forgetting light-pressure turbo petrol engines for a minute...

The petrol turbo will only be generating significant boost for short(ish) periods of time at or near WOT. The intercooler is behaving more as a heat sink than a heat exchanger; it will have time between boost episodes to cool off. This is why VAG can get away with a side-mounted intercooler, out of the main airstream, on their 1.8T engines.

The diesel turbo will be boosting whenever the engine is under moderate or heavy load. For example, it will be generating boost most of the time while the vehicle is climbing a hill. The intercooler needs to be a better heat exchanger that the intercooler on a petrol engine, so mounting it at the front will be better. The intercooler on the VAG 2.0 PD turbo diesel (at least, on my Skoda Octavia) is sandwiched with the radiator.

Edited by lazy_b on Sunday 27th February 11:25

[anonymous-user]

The major problem is that with a common rail diesel, the injected fuel quantity is NOT directly determined by intake airflow!! So, fitting a bigger IC, will bring down charge temperatures, increasing air mass flow, but no more fuel will be added, so no more torque will be produced (the engine will just operate in a leaner condition)


The only time intake mass flow has a limiting effect on fuel quantity is during the transient "smoke limit fuel mass clipping" where the injected fuel quanity is temporarily limited to prevent excessive smoke whilst the turbo gets up to speed and increases the intake mass flow sufficiently to support the target AFR.


BTW, boost pressure will actually fall, as the EMS will be able to get to the target mass flow at a lower plenum pressure due to the denser intake air.

[dblack1]

What most people dont understand about diesels is that what controls the timing of the ignition on a diesel is the actual injection sequence. Not to say I know everything about diesel, turbos, or turbo diesels (I actually dont know much about diesels), but air, not fuel/air mix, is the only thing that goes into the cylinder through the intake valve. the fuel is injected by an injector inside the cylender. detonation is not possible with a diesel (assuming its properly timed) because the fuel is not injected into the cylinder until its time for it to ignite. I am unsure of the purpose of intercoolers on diesels (remember i said i dont know much about diesels), and i can only speculate about their purpose.

[chuntington101]

Would an intercooler not help lower the EGts on a deisel? i allways here the US guys (ok they get big V8 ddeisels that sound really fun) saying that EGTs are a killer on their engines....

Chris.

[anonymous-user]

If you've made a complete set of donkey trousers of your fuel timing then maybe EGT might be a problem, but generally no.

If you have remapped your engine controller to add a greater fuel mass, then a denser air charge will enable a greater BMEP without exceeding the smoke limited AFR value. (you will also gain a small power advantage from the reduced EBP (turbine pressure ratio is more favourable as you need less compressor work to move the same intake mass flow, but it's be in the order of 1 or 2bhp on a std engine, which isn't much for fitting several hundred ££ of FMIC.....)

[stevieturbo]

chuntington101 said:

Would an intercooler not help lower the EGts on a deisel? i allways here the US guys (ok they get big V8 ddeisels that sound really fun) saying that EGTs are a killer on their engines....

Chris.

Add more air without any extra fuel and EGT's will drop, as will power.

[chuntington101]

stevieturbo said:

Add more air without any extra fuel and EGT's will drop, as will power.

yueah thats what I thought steve. Just didn't really understand how much gose into tuning a derv! esp these modern ones.

off topic but i was googleing compound turbocharging the other night on the net and found a guys in the US with a triple compound setup (thats one MASSIVE turbo feeding a medium sized one feeding the little stock one) on a Ford 7.3 powerstroke i think. There was no intercooler as far as i could see!

[stevieturbo]

chuntington101 said:

yueah thats what I thought steve. Just didn't really understand how much gose into tuning a derv! esp these modern ones.

Ive no idea about the actual complexities of a modern CR diesel. But from a very simplistic approach, the above applies.

It seems modern CR diesels dont just inject once per cycle....but many times. As for how much and when, I have no clue. It does sound a bit more complicated in some ways than petrol tuning.

Although there are a couple of aftermarket ecu's available now to run CR diesels. Not sure how they will take off. Mostly geared towards engine transplants or dyno testing though but would equally be at home in a vehicle.

Adaptronic's top of the range ecu can do it, and Specialist Components in Norfolk have an ecu that can do it.

[anonymous-user]

Current CR diesels are using 7 injection events, all targeting at producing a very controlled cylinder pressure profile during the compression and power stroke. By carefully injection multiple small quantities of fuel as the cylinder volume varries (and hence the pressure and temperature also varries) the optimum compromise can be found wrt emissions, BMEP, acoustic and transmitted noise and of course fuel economy. Unfortunately, pretty much everything you do to make the engine quieter results in a poorer fuel economy, the current black art in diesel calibration is striking that balance, making the engine quiet enough to keep the NVH reasonable, but in the face of massive pressure to eak out every last mile from the fuel to get tailpipe Co2 down.

With the introduction of the lower particulate limits for EU5 compression ignition engines, minimising certain sized soot particles has also become increasingly important, as even with a DPF, fuel economy suffers when you have to "regen" the DPF. (better to not make the "smoke" in the first place!!!)

Thats on top of all the normal EOBD/diagnostics and driviablity calibration that goes on......

[chuntington101]

Max_Torque said:

Current CR diesels are using 7 injection events, all targeting at producing a very controlled cylinder pressure profile during the compression and power stroke. By carefully injection multiple small quantities of fuel as the cylinder volume varries (and hence the pressure and temperature also varries) the optimum compromise can be found wrt emissions, BMEP, acoustic and transmitted noise and of course fuel economy. Unfortunately, pretty much everything you do to make the engine quieter results in a poorer fuel economy, the current black art in diesel calibration is striking that balance, making the engine quiet enough to keep the NVH reasonable, but in the face of massive pressure to eak out every last mile from the fuel to get tailpipe Co2 down.

With the introduction of the lower particulate limits for EU5 compression ignition engines, minimising certain sized soot particles has also become increasingly important, as even with a DPF, fuel economy suffers when you have to "regen" the DPF. (better to not make the "smoke" in the first place!!!)

Thats on top of all the normal EOBD/diagnostics and driviablity calibration that goes on......

Fook me! there gose the idea of odern big deisels ever getting into the kit car world then! lol It seem like just getting an engine to run is an achievment.

How dose this imapc tthe aftermarket world? I hear the Banks do ECUs for the US guys now. THink they are only doing mailorder tunes and they need to be used as part of their power packages (intakes, intercooler, exhaust, etc.).

I have heard of some people drag racing using these engines also. How do you go about getting the most power/torque out of a deisel, not worrying about the fuel or the emissions (ie keeping it simple)? lol

Chris.

[anonymous-user]

Luckily, any modern CR diesel will "run" with just one injection event, it just won't be very quiet or emissions friendly (it'll make the power just fine, although you may exceed the peak cylinder pressure limit as you have much less control over the acceleration of the cylinder pressure trace)

The "aftermarket" CR ecu's i know about tend to do 2 events, a pre and a main. This gives a big improvement to combustion noise, but would get nowhere near the OEM emissions or noise targets.


The two biggest challenges in CR diesel control are getting accurate and repeatable control of fuel injection pulse timing (OEM are better than 0.1 crank degrees resolution (at 5000rpm = 3.3uS (millionths of a second)) and driving the solenoid or piezo injectors correctly (they require a high voltage (~50 to 100v) peak and hold driving technique to get them to open and shut quickly enough. The OEMS are quite clever in this respect as they use the inductance of the injector itself to Boost the 14v to 100v odd, so their drivers are very small physically. (most aftermarket stuff reqiures a seperate large driver box)

Edited by anonymous-user on Tuesday 1st March 13:05

[chuntington101]

Max_Torque said:

Luckily, any modern CR diesel will "run" with just one injection event, it just won't be very quiet or emissions friendly (it'll make the power just fine, although you may exceed the peak cylinder pressure limit as you have much less control over the acceleration of the cylinder pressure trace)

The "aftermarket" CR ecu's i know about tend to do 2 events, a pre and a main. This gives a big improvement to combustion noise, but would get nowhere near the OEM emissions or noise targets.


The two biggest challenges in CR diesel control are getting accurate and repeatable control of fuel injection pulse timing (OEM are better than 0.1 crank degrees resolution (at 5000rpm = 3.3uS (millionths of a second)) and driving the solenoid or piezo injectors correctly (they require a high voltage (~50 to 100v) peak and hold driving technique to get them to open and shut quickly enough. The OEMS are quite clever in this respect as they use the inductance of the injector itself to Boost the 14v to 100v odd, so their drivers are very small physically. (most aftermarket stuff reqiures a seperate large driver box)

Edited by Max_Torque on Tuesday 1st March 13:05

Very intresting stuff Max! is there any ways of having a veriable flow injector? Just thinking that might be easier to control than simply having to turn on and of a conventional injector would it not?

Also you mentioned 'peak cylinder pressure limit', is that the deisel version of dept.? is it just pushing the engine a bit harder than it normally would? What are the problems with runnng the engine in this state of tune?

FInalyl, i hear that aftermarket tuning (either via a box or a proper remap) is getting more popular. What do these actually modify with regard to fueling? Do they just increase the amount of fuel injectored during ALL injection instences or just some of them? Or do they do away with some of them and run fewer?

Thanks,

Chris.

[anonymous-user]

chuntington101 said:

Very intresting stuff Max! is there any ways of having a veriable flow injector? Just thinking that might be easier to control than simply having to turn on and of a conventional injector would it not?

Also you mentioned 'peak cylinder pressure limit', is that the deisel version of dept.? is it just pushing the engine a bit harder than it normally would? What are the problems with runnng the engine in this state of tune?

FInalyl, i hear that aftermarket tuning (either via a box or a proper remap) is getting more popular. What do these actually modify with regard to fueling? Do they just increase the amount of fuel injectored during ALL injection instences or just some of them? Or do they do away with some of them and run fewer?

Thanks,

Chris.

making a true varriable flow injector would be possible, but be a bit of a 'mare, as the fuel atomisation and distribution pattern would vary with flow! The low cost adoption of precise "digital" control (most modern ems system are running with twin processors @ approx 500MHz) means an On or OFF approach is still favoured (it also gives you the quickest transient response where required,unlike say maybe reducing fuel pressure during some point of the engine operational area)


Peak cylinder pressure is just that, it's the design point for the mechanical system. i.e. when designing the reciprocating parts (crank, rods, pistons) and the containment systems (block/liners, head gasket, bolt system etc, even the mechanical strength of say the cylinder head). Based on this value (typically ~160 to 180bar for a modern CR diesel (vs ~100bar for gasoline engine) the engine calibration teams will optimise the output without exceeding it. It actually doesn't limit total torque output, as you just calibrate a longer burn instead of a short sharp one (but because you are burning over a larger crank angle (and hence cylinder volume) you loose more heat to the chamber, so efficiency is worse).

Generally exceeding Pmax is not instantly a failure, but if you do enough cycles above Pmax, mechanical/material failures will occur eventually. (typically, at the design point, the engine will do an 180hr HST without failure (180hrs continuous at peak power!!)


Most of the aftermarket boxes just fool the system into adding more fuel in a pretty adhoc basis. usually by intercepting and modify the fuel rail pressure sensor output. (so the ecu thinks the fuel pressure is low and so adds some more) Whilst this undoubtly will make more BMEP (more fuel will go into the engine) you really don't know the results on emissions, power, economy, or mechanical life!

On the latest EMS systems, the burn rate/fuel quantity is actually controlled in a closed loop fashion via "knock" sensors listening to each combustion event!!

[chuntington101]

Max_Torque said:

making a true varriable flow injector would be possible, but be a bit of a 'mare, as the fuel atomisation and distribution pattern would vary with flow! The low cost adoption of precise "digital" control (most modern ems system are running with twin processors @ approx 500MHz) means an On or OFF approach is still favoured (it also gives you the quickest transient response where required,unlike say maybe reducing fuel pressure during some point of the engine operational area)


Peak cylinder pressure is just that, it's the design point for the mechanical system. i.e. when designing the reciprocating parts (crank, rods, pistons) and the containment systems (block/liners, head gasket, bolt system etc, even the mechanical strength of say the cylinder head). Based on this value (typically ~160 to 180bar for a modern CR diesel (vs ~100bar for gasoline engine) the engine calibration teams will optimise the output without exceeding it. It actually doesn't limit total torque output, as you just calibrate a longer burn instead of a short sharp one (but because you are burning over a larger crank angle (and hence cylinder volume) you loose more heat to the chamber, so efficiency is worse).

Generally exceeding Pmax is not instantly a failure, but if you do enough cycles above Pmax, mechanical/material failures will occur eventually. (typically, at the design point, the engine will do an 180hr HST without failure (180hrs continuous at peak power!!)


Most of the aftermarket boxes just fool the system into adding more fuel in a pretty adhoc basis. usually by intercepting and modify the fuel rail pressure sensor output. (so the ecu thinks the fuel pressure is low and so adds some more) Whilst this undoubtly will make more BMEP (more fuel will go into the engine) you really don't know the results on emissions, power, economy, or mechanical life!

On the latest EMS systems, the burn rate/fuel quantity is actually controlled in a closed loop fashion via "knock" sensors listening to each combustion event!!

Thanks agian max.

So for a max power effort engine you would probably only have two injection instences per cycle? Would that be a little one and then a single big one? How would an aftermarket setup know how much fuel to inject? what peramitors do you monitor when tuning? What do you do when you run ouit of injector? can you run higher rail presures?

also do dose the amount of fuel per instence increase or is it a staic amount? I would guess the injector is held open a little longer each time. Or do the first 4 increase in time and then the remainder reduce as there is less O2 in the cylinders to burn?

I ahve heard of people using LPG injection on deisel engines. Is this any good if you are after performance? how doe that effect the way the engine runs? Can will it let you run anymore boost/make more power?

Thanks,

Chris.

[anonymous-user]

chuntington101 said:

Thanks agian max.

So for a max power effort engine you would probably only have two injection instences per cycle? Would that be a little one and then a single big one? How would an aftermarket setup know how much fuel to inject? what peramitors do you monitor when tuning? What do you do when you run ouit of injector? can you run higher rail presures?

also do dose the amount of fuel per instence increase or is it a staic amount? I would guess the injector is held open a little longer each time. Or do the first 4 increase in time and then the remainder reduce as there is less O2 in the cylinders to burn?

I ahve heard of people using LPG injection on deisel engines. Is this any good if you are after performance? how doe that effect the way the engine runs? Can will it let you run anymore boost/make more power?

Thanks,

Chris.

if you really only care about producing the maximum BMEP, then a single, rapid injection at the optimum crank angle will get you that. You need large injectors to get the pulse time short, so all the fuel goes in as fast as possible, and burns as quickly as possible to limit the heat lost to the cylinder walls. This will make decent power, but would sound terrible, as the rate of rise of cylinder pressure would be enormous (literally an "explosion" rather than a burn)

Small pre injections are used to increase the temperature in the cylinder before the main injection occurs, this helps increase the flame speed of the burning fuel, decreasing the burn time (again = more efficient). "high speed" modern diesels really only became possible (making peak power >4000rpm) due to the usage of this pre injection events (although precise control of the turbulence and mass distribution within the cylinder also plays a huge part, hence lots of modern 16v diesels with 2 intake tracks controlled by seperate valves)

CR diesels will run at approx 100:1 AFR at idle, down to a smoke limited minimum AFR of approx ~16:1. Tuning an aftermarket system would rely on dyno work to establish the torque response to various fuel quantity and timing settings.

when you run out of injectors, like every fuel injection system you're a bit stuck! increasing the fuel pressure will only return a Root2 increase in mass flow, but typically an OEM system will control to varying rail pressure during different operating modes.

The distribution of the total injected fuell quantity across the multiple injection again depends on what you are trying to achieve. many hrs of engine dyno work with in-cylinder pressure measurement, Exhaust gas analysers (NOx, THc, O2,NMHc, Co) and "Fast FID" devices for particulant measurement will be spent by an OEM to optimise all these overlapping and interacting parameters.

[davepoth]

Smoke limited to 16:1, but what's the optimum AFR for diesel?

I guess a lot richer going by this:

[anonymous-user]

Just like a gasoline engine, optimum BMEP will be at an AFR where you guarantee to use everylast air molecule, so peak output will be down at around ~11:1, but at this point, the smoke particulate formation is very poor, hence all that crap flying out of those stacks!!!

[chuntington101]

how dose such a low air to fuel raito effect the turbos? i guess its more the particulates that are going to clog them up.

Also i hear of company in the IS called Banks racing. they specialise in the GM Duramax 6.6ltr V8 32 valve derv engine. THey have pushed over 1300bhp out of drag engines with NO smoke out the exhaust at all! Think i read that they are spinning the motors to well over 6K and are looking to go to 8K rpm!!!!!!

They also build some pretty intresting marine engines (inc. supercharged and trubos charged (same as the VW 1.4 engine) version) and some intresting twin turbo'ed crate engines. Below is the link to their site.

http://www.bankspower.com/ main website

http://www.bankspower.com/racing for the intresting stuff.

If only this kinf of work could go in to some of the derv engine we see over here! how nice would it to see a 350-400bhp deisel golf/mondeo engine? would definately things a little more intresting in the motoring world i think.....

Chris.

[anonymous-user]

chuntington101 said:

how dose such a low air to fuel raito effect the turbos? i guess its more the particulates that are going to clog them up.

Not a problem from that respect, nothing really can stick to a turbine going round at 150krpm, the centripetal accel just chucks it straight off !!