Thread: How to get 400Nm from RRC

Originally Posted by justinc

...And keep it light!!!!!!

power to weight is instantly improved with no engine mods that way...


jc

Yep years ago built up my D2 over time, added bull bar, winch aggressive tyres and more off road goodies. Had a drive of a friends stock D2 TD5 and jumped back in mine and wonder why mine felt so gutless. Then remember all the extra weight I'd added to mine.

My this thread has been busy in the time I was away.

Let us start with the absolute basics of tuning any engine in any vehicle. That is matching air and fuel.
This is why we have an air/fuel ratio. The tuners of petrol vehicles are well aware of what happens when you get it wrong, detonation and/or melting pistons.
The tuners of diesels less so, but the fundamentals are the same.

We have a stoichiometric ratio where if conditions are perfect we can acheive complete combustion and leave no oxygen in the exhaust.
Stoichiometric for diesel fuel is 14.55:1, not much different to the 14.7 for petrol.
We have a bell curve for air/fuel ratio and temperature. This climbs to a peak which is on the lean side of stoichiometric.

Here is a graph from a 2 stroke petrol:


Here is a graph I've modified to show what I needed:


As you can see, we run on the other side of the curve to petrol engines. If they lean out, they hit the hot part of the range and melt pistons.
With diesels if we run too rich, we melt pistons.

I have put a big green band in to show where stock diesel engines run. These are big because it's a range. Where they run in this band depends largely on what NOx emissions they were designed to meet and what other strategies they use to control that (retarded timing, EGR, adBlue etc).

I have put a big orange band in to show the allowable tuning band for a tweaked diesel engine to run. This is where EGT and NOx are considerably higher than stock, but power is too. It is possible to increase the average diesel engines power by ~20% by adding fuel to move it from the stock A/F ratio band to the hot end of tuned band.
This is band because other factors come into play. A poor injection system will start to smoke at a higher (leaner) A/F ratio, a very good injection system may run at 17:1 while completely clean. Injection timing and intake temperatures also affect where you can run with still safe EGT.
Other engineers have run controlled dyno experiments and found the engines maximum efficiency (converting fuel to power) is found at 18:1.

Then there is a gap. This gap is the place you never want to run. But your engine may dip into that point during turbo spool up without any real problems.
Running in that gap is tempting engine failure. Pistons heat, soften and expand until they grab the bores of your engine.

That red band at 16:1. That's the smoke limit. At this point your engine will be smoking like a coal train no matter how good your injection system is. Quite simply the oxygen doesn't have the time to find the fuel so more and more of it goes out the exhaust as smoke.
At this point your EGT is through the roof. The only thing preventing engine failure is the time it takes a piston to heat soak.


Examples:
Let's consider a couple of case studies. Engines which in stock or modified form have a reputation for crapping themselves under high load. Towing, climbing hills or just being driven in hot conditions (like Australia).

1. Toyota 2LT.
This is a 2.4 litre indirect injection turbo engine. They are famous for cracking heads.
In stock tune they aren't that smokey, even driving behind them under full load the exhaust is only a light haze. No black clouds.
Those who've measured EGT put it beyond 800C. But there are owners who've cranked up the boost (thus leaning out the mixture at full load, dropping EGT and moving from the left of the orange band into the green) and aren't cracking heads.

2. Nissan ZD30.
This is a 3 litre direct injection turbo engine. They are famous for not cracking heads (direct injection heads are stronger), but for melting pistons through excessive EGT. Direct injection pistons have a combustion bowl which allows heat to easier get to the centre of the piston. This makes them more susceptible to melting than idi pistons.
JustinC I beleive has measured one.
Just like the 2LT these run very rich stock. Not rich enough to smoke under load. But still rich enough to blow holes in pistons.

3. Toyota 1HZ.
This is a 4.2 litre indirect injection diesel engine. Like most non turbo idi engines they run very rich, almost 16:1, knocking right on the smoke limit. Yet they don't blow black smoke in good condition, just a haze as the idi combustion gives very good air/fuel mixing.
But strap a turbo on, increase the fuelling and down they go. Melting pistons on an IDI engine is difficult as they have a flat surface which heat doesn't get into like a direct injection piston. Yet many have still managed a melt-down with a turbo and a tune that doesn't blow smoke.


Meltdown avoidance
To know a tune is safe and avoid a melt-down there are two things we can do.

1. Measure the outputs (EGT or lambda probe). This is IMO critical. You should not be tuning any diesel engine without being able to measure either the exhaust temperature in the manifold (preturbo) or the oxygen content of the exhaust.
I haven't spent $1k on gauges to impress the lads outside repco. I did it so I know my tunes are safe. An unsafe tune can cost many multiples of that.

2. Calculate and measure the inputs (fuel, cc/stroke and boost density).
This is the hard way. It takes about half a thermodynamics book to calculate air density from the effects of intake temp, boost pressure, compressor efficiency and intercooling. It is less work to calculate the air consumption of the engine (displacement, VE, rpm) and then simple maths (air in cylinder divided by A/F ratio) to know what the MAXIMUM amount of fuel that can be safely injected is at that point.

Torque Limits and checks
Once you've done the above calcs, the results are quite consistent across all direct injection turbo diesels.
They can all produce ~70-75Nm/litre of displacement with no boost.
With boost, it is simply multiplying the intake air density (20psi intercooler gives double the air density of no boost) by the 70-75Nm and displacement.

So a 2 litre diesel.
No boost, ~140-150Nm. Real world example, Nissan YD22, 155Nm.
20psi boost and intercooled, ~280-300Nm. Real world example, VW 2.0tdi, 320Nm, 24psi boost.

4 litre diesel.
No boost, 280-300Nm.
20psi boost and intercooled, ~560-600Nm. Real world example, tweaked 4BD1T.

When these numbers don't add up (for example claimed torque is far higher than calculated) then either the numbers are wrong (gear ratio wrong on the dyno etc) or the tune is extremely rich or lean.
An extremely lean tune has no problem at all. A tune rich enough to step outside those A/F bounds however can cause very expensive engine damage.

Power checks
Power checking is much more difficult than torque. Because the higher rpm of the engine puts more reliance on values such as VE which can vary markedly between engines. Other industrial based engines also have a rated maximum power which is lower and at a lower rpm than the engine can actually acheive.
But the comparisons remain. If boost is not changed from stock, then greater than a ~20% increase is an indicator of a dangerous tune.

Power vs Economy
There is no difference between a safe power tune and a maximum economy tune. As mentioned above, the maximum conversion efficiency from fuel to power is around 18:1 A/F ratio. The furtherest you can deviate from this and still be remotely safe is only 1 point on the A/F scale.
A clean and safe tune that gets the maximum from the turbocharger you have fitted is also the most economical tune you can run. Simply lift your foot a little further if you want to burn less fuel.

Bottom line
Like every other engine (petrol, lpg, 2stroke, 4stroke) diesel engines are limited to what they can safely deliver by the airflow they can process. The #1 tuning tool on a turbo diesel engine is the turbocharger. You cannot safely increase power and torque much beyond stock without a corresponding increase in boost pressure.

EFI tuning parameters
All EFI diesels measure intake flow or pressure and atmospheric pressure. They reduce fuel in situations where boost is restricted, intake airflow is restricted or atmospheric pressure drops (i.e high altitude) or coolant temps get out of hand.
They do this to keep A/F ratios and EGT in check and prevent engine damage in the worst conditions.

Famous examples
Take a look at the videos of the Audi TDI's in le-mans sometime. Contrary to some claims on here there was never a wisp of smoke emitted.
Take a look at some of the clowns on youtube for how not to tune diesels.

Dangerous words
Run the other way if you hear these words from any "tuner":
What's an EGT gauge?
I don't have any EGT measurements right now.
It's all about flow, not boost pressure.
30% power increase, no boost increase.
You can switch between our power and economy tunes.
Any car will blow up if you run it at maximum power.
More smoke gives you more power.
You can't make power smoke-free.
All diesels smoke.
Altitude made it smoke.
Look it's idling and not smoking.
Your DPF will stop it smoking.
We can make a smoke/no-smoke button.

Hard Questions
It doesn't matter which country your proposed tuner is from or what they claim to have done or not done before. You need to ask these questions.

What is the maximum EGT you consider safe?
What is the maximum EGT I will hit on this tune?
What is the maximum safe boost for my turbo?
Do you raise boost pressure? If so, by how much?
What is the maximum torque my driveline can handle?
What is the maximum torque you expect from this tune?

“In theory, theory and practice are the same. In practice, they are not.”

"Well, it may be all right in practice, but it will never work in theory."

"I want to move to theory. Everything works in theory."

"In theory, the difference between theory and practice is small. In practice, the difference between theory and practice is large. "

Just a friendly reminder guys, let's not let this thread go back to where it was a bit ago...

Things have been progressing well since, let's keep it that way.

Cheers - Gav.

Hello,

Very useful post Dougal wich resumes pretty much the basic theory´s of air/fuel when remapping. It´s informative and has little or no traces off attack to anyone or any company Hopeffuly this can became an informative thread and not just an "your not a good tuner thread", just because!

Your examples are from japanese engines, and japenese engines (as all other parts in fact) are known for being reliable when they get everything made in the right way, but also for being crap if not.
For example: both the Nissan rd28t and ZD30, in standart form, overhere are not reliable engines. The first one is known for poor performance and overheating to much (guys simply swap it for the 4 cilinder nissan Cabstar BD30 truck or the toyota 4.1 15-bft and put VNT turbos in them); the second one for simply blowing turbos or melting pistons (the ZD30, in fact, brought a lot of problems to nissan dealers here, in the patrol and the terrano, because they have to replace a lot of engines free of charge in warranty services).

This said, I´m familiared with some of your examples, but they are not td5´s. Do remember that the basics are pretty much the same but all the cars are differents and all have "secrets" wich take long time and development to find out.

There are thousands of command lines in the maps, some are identified, some not. Fuel to air is some of the things you mess with, but you get to mess with engine and throttle response, limiters, etc etc...
In the td5 you can even mess with things either its in hi gear or low gear, making diferent settings ( that´s why asking if the car is in low or hi range is so important in regarding this cars)

In my particular case, I´m very confortable with all those "hard questions" and also with those "dangerous words" (my costumers know that), altough I get the point of some of your examples, but my previous posts, can actually answer all of that

Originally Posted by Dougal

Famous examples
Take a look at the videos of the Audi TDI's in le-mans sometime. Contrary to some claims on here there was never a wisp of smoke emitted.
Take a look at some of the clowns on youtube for how not to tune diesels.

As I believe you noticed, words dont come out of my mouth without sure of what I´m saying... So, again, I have to desagree on you (hopefully my definition of "wisp of smoke" is the same you have...)

.. Audi R18 Lemans vídeo... minute 0.48... minute 1.19... minute 1.21...

[ame=http://www.youtube.com/watch?v=MxmNIBTRLQo]Audi R18 TDI LMP1 Testing At Sebring - YouTube[/ame]

A bit help for you:





And another example - Vw race touareg 5 cilinder...



Regards,

Not taking sides here, and I'm not a tuners arsehole but that Audi definitely has a bit more than a 'wisp' of smoke under hard acceleration...

Originally Posted by td5inside

It was a 2.8 liter And If I remember Lara had to spend a lot more money in to gearbox and halfshafts

To be honest, I think we can get power from a 2.5td5 more than enough for the rest of the car. Zero aerodinamics, drivetrain with weak axles, not so good brakes (defender) its not exactly something you want with hundreds os power

If you want to give more power to a car...fit it with a very good suspension ehhe

P.S. - Realy dont know if the 3.2 tdci can be the answer... All looks good on the paper, even on the road, but what about offroad?!!

if we are talking road speed and LR aero dynamics then we need more torque and lots of it.

Axles shafts are easy to upgrade for reasonable dollars

IMO the R380 is only so good, even in stock rovers doing real work.

What is wrong with the 3.2 off road. Id have it over the 2.4/2.2 every day of the week. I would also have it over a 2.5 tdi making the same power.

That is not rocket surgery I can tell you that much

Originally Posted by bacicat

Not taking sides here, and I'm not a tuners arsehole but that Audi definitely has a bit more than a 'wisp' of smoke under hard acceleration...

I certainly would not call it very much either. Even when not comparing it to the stock diesel cars/4x4 we see on our roads and then taking into account the HP those race engines are making from their respective capacities