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TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old October 17th, 2017, 17:51   #31
TDIMeister
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A little more engine engineering for those interested. It's no big surprise that a 3.9 L 4BT develops rated power at "only" 2400 RPM (9.52 m/s mean piston speed) and the 1.9 TDI at 3750 RPM (14.875 m/s), but do you really know why? There are many factors why these two engines develop their rated powers at RPMs that they do, but many parameters scale with the very important mean piston speed (MPS, eg. in-cylinder turbulence, swirl intensity, port flow velocities, etc.). We could take the analysis further. The upper limits of MPS - high-20s m/s in F1/Cup engines, into the 30s m/s for Top Fuel drag racers, are dictated primarily by tribological considerations (maintaining an oil film in the piston ring-cylinder interface) and tensile mass forces taken up by the pistons and connecting rods.

If we set a criterion to limit kinetic energy in the reciprocating group to be roughly constant, which would translate to strain energies that the rods have to take, then the disparities of MPS between say a 4BT and an ALH TDI almost disappears.

Kinetic energy is proportional to the mass times velocity squared.

Mass is proportional to the cube of a characteristic dimension, I'll use bore diameter d here.

So, the kinetic energy is related to d^3*MPS^2.

With the criterion of constant kinetic energy, there results a relationship of bore diameter vs MPS as
MPS is proportional to d^(3/2).

Now let's plug in some numbers:
TDI bore: 79.5mm
4BT: 102mm

Taking the TDI as a baseline with MPS = 14.875 m/s,

14.875 *(79.5/102)^(3/2)=10.23 m/s, which is pretty close to the value of the 4BT's MPS at rated power. The remaining difference can be attributed to the 4BT being designed for heavier duty durability than a TDI.

The take home message here is also that it is not realistic to have a 4BT rev to the same RPM as a TDI, but one can go further to say that it is comparing apples to oranges even to match MPS. Rather, there is a physics-based rationale to relate and scale MPS between engines of different sizes using energetic or mechanical strength criteria.
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Old October 18th, 2017, 01:55   #32
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Quote:
Originally Posted by TDIMeister View Post
A little more engine engineering for those interested. It's no big surprise that a 3.9 L 4BT develops rated power at "only" 2400 RPM (9.52 m/s mean piston speed) and the 1.9 TDI at 3750 RPM (14.875 m/s), but do you really know why? There are many factors why these two engines develop their rated powers at RPMs that they do, but many parameters scale with the very important mean piston speed (MPS, eg. in-cylinder turbulence, swirl intensity, port flow velocities, etc.). We could take the analysis further. The upper limits of MPS - high-20s m/s in F1/Cup engines, into the 30s m/s for Top Fuel drag racers, are dictated primarily by tribological considerations (maintaining an oil film in the piston ring-cylinder interface) and tensile mass forces taken up by the pistons and connecting rods.

If we set a criterion to limit kinetic energy in the reciprocating group to be roughly constant, which would translate to strain energies that the rods have to take, then the disparities of MPS between say a 4BT and an ALH TDI almost disappears.

Kinetic energy is proportional to the mass times velocity squared.

Mass is proportional to the cube of a characteristic dimension, I'll use bore diameter d here.

So, the kinetic energy is related to d^3*MPS^2.

With the criterion of constant kinetic energy, there results a relationship of bore diameter vs MPS as
MPS is proportional to d^(3/2).

Now let's plug in some numbers:
TDI bore: 79.5mm
4BT: 102mm

Taking the TDI as a baseline with MPS = 14.875 m/s,

14.875 *(79.5/102)^(3/2)=10.23 m/s, which is pretty close to the value of the 4BT's MPS at rated power. The remaining difference can be attributed to the 4BT being designed for heavier duty durability than a TDI.

The take home message here is also that it is not realistic to have a 4BT rev to the same RPM as a TDI, but one can go further to say that it is comparing apples to oranges even to match MPS. Rather, there is a physics-based rationale to relate and scale MPS between engines of different sizes using energetic or mechanical strength criteria.
I don't understand what bore diameter has to do with mean piston speed?
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Old October 18th, 2017, 12:05   #33
Yucca
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Originally Posted by TDIMeister View Post
Apart from Andy2, I have not seen any 400+ HP or even 350+ actually realized in a VE, even though in theory it's possible (I have even done the calcs).
We have had many +350bhp VE setups in Finland. My 388bhp ALH is one example

https://postimg.org/image/ohhm3rdif/

- 1.9ALH Block with H-beam rods
- Ported head from npsheads.com
- Custom CAM
- Borg Warner S356V
- HFLO-X 0.341 Nozzles
- Stock 11mm pump
- Tdituning.fi tune

Engine is now in my Chopped Lupo 3L for Standing Miles.
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Old October 19th, 2017, 06:23   #34
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Awesome idea, I hope it pans out. I don't have much to add, other than I am a huge fanboy of diesel tractor pulling. I think if you are allowed to run an intercooler, you absolutely should! I see a lot of guys with "hot farm" tractors that do not, but all the guys that run the best do use them. If they are allowed, you would be crazy not to run it along with water/meth. (only water injection is allowed here in VT).
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Old October 19th, 2017, 08:21   #35
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Originally Posted by vtpsd View Post
Awesome idea, I hope it pans out. I don't have much to add, other than I am a huge fanboy of diesel tractor pulling. I think if you are allowed to run an intercooler, you absolutely should! I see a lot of guys with "hot farm" tractors that do not, but all the guys that run the best do use them. If they are allowed, you would be crazy not to run it along with water/meth. (only water injection is allowed here in VT).
We can run them, I just don't know if it would do any good without having much vehicle speed? We don't go much slower than the big tractors, so maybe it's still beneficial?
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Old October 19th, 2017, 08:42   #36
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I think it still would be beneficial. Construction equipment and farm tractors still have intercoolers. Its still going to dissipate some amount of heat, even if you are moving slowly.
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past:11 second audi 90 20vt monster, 20vt swapped audi 90 winter beater, 10vt swapped 4kq with efi and many many other 5 cylinder audis, and a few 1.8tq's
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Old October 19th, 2017, 09:05   #37
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A radiator standing still in the corner of your bedroom still heats the whole room. Ideally you want lots of airflow but even just plain convection will eat a bunch of heat from an intercooler.

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Old October 20th, 2017, 10:07   #38
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Air-Water intercooling allowed?
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Old October 20th, 2017, 10:13   #39
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Also, even though this is a VW specific forum, have you considered a Mercedes OM604? If that engine fits within the displacement limit rules for the class, it's worth a look.


Steve.
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Old October 20th, 2017, 18:26   #40
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Air-Water intercooling allowed?
Yes, we can do pretty much anything we want. My limiting factor is space to fit it and weight. Considered it though also
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