1.9TDI PD compound sizing

[adamss24]

Out of curiosity, what trailer with heavy loads do you tow ? I used to tow a iffor Williams 2.7t trailer with my old allroads v6 tdi (tuned AKE gtb2260vk/bosio race 683 nozzles and also tuned BAU with same modifications) without much bother and had all sorts of vans(t4 lwb, transits,etc),xj jags, bmw 7 series LWB, s500 lwb and never had issues starting up on inclines as such. Basically if it got on the trailer i would tow it !
The reason I mentioned you best to get a dedicated tow car is because you can have a really stout car with the weight to handle heavy loads and still run the torque necessary to pull the loads without being pushed by the load on braking/deceleration !
A Touareg v6 tdi with the aisin 8 speed gearbox will tow anything you can think of !

 

[miniCotulla]

well, you don't really need it to make crazy amounts of boost down low, 7psi or 500mbar is going to be plenty motivation to get even something like an s300 turbo spooled up, with the greater exhaust energy...
Think of the supercharger and engine just as a 3-liter engine rather than a 2.0.

Yes.
There are actually many applications where you unload a mechanically coupled compressor just by venting/recirculating the discharge. There is very little parasitic loss when there is no pressure differential across it.

I think a flapper valve won't work in this application, as long as the turbo is charging through the SC the pressure front and back of the valve will be the same. Or did I miss something?

 

[miniCotulla]

Out of curiosity, what trailer with heavy loads do you tow ? I used to tow a iffor Williams 2.7t trailer with my old allroads v6 tdi (tuned AKE gtb2260vk/bosio race 683 nozzles and also tuned BAU with same modifications) without much bother and had all sorts of vans(t4 lwb, transits,etc),xj jags, bmw 7 series LWB, s500 lwb and never had issues starting up on inclines as such. Basically if it got on the trailer i would tow it !
The reason I mentioned you best to get a dedicated tow car is because you can have a really stout car with the weight to handle heavy loads and still run the torque necessary to pull the loads without being pushed by the load on braking/deceleration !
A Touareg v6 tdi with the aisin 8 speed gearbox will tow anything you can think of !

I only tow up to 1,5t, but there are many steep hills in my area. For really heavy loads my brother has a V6 Allroad with low range. The low range alows you to start at every angle, not matter how heavy the trailer, like it was a flat street.

 

[adamss24]

Yep, low range allroad will make. Huge difference ! Had a petrol 2.7 twin turbo allroad about 10 years ago, really nice car but rather thirsty ! Never had the chance to enjoy the low range gearbox although I was contemplating swapping the box to my AKE allroad at the time ! Ended up selling it to a mate of a mate that still owes me money for the car ! Damn !

 

[miniCotulla]

Does anyone know if the bearings and seals in an Eaton Supercharger can withstand 3 bars of boost? The clutch will be disengaged and the flow routed around the supercharger but the pressure is still there.

 

[miniCotulla]

I see no easy way where you can avoid the "step" in manifold pressure as well as in the vehicle performance during the switchover. The frequent on-off of the supercharger might also decrease the life compressor and certainly the clutch.

I think a step should be avoidable when I open the valve and clutch after the turbo is already spooled and delivering the same or more boost then the SC. Or do you mean a step as the load from the SC is taken away while opening the clutch? But the SC should already be unloaded when the pressure before and after is the same (turbo already took over)

Do you think the constant starting and stopping of the SC will damage it and it's clutch? The clutch is stock on mercedes units, I think they are built for that or is this only an emergency shut off and not active during normal driving? In my application the SC would disengage everytime the turbo spools and engage when I take my foot of the throttle.

It seams like a good idea as the mercedes unit should already deliver 0,7 bars of boost at idle (according to an online calculator). Essentially simulating a way bigger engine to the turbo.

Where can I find a 3 inch bypass valve?

 

[TDIMeister]

I think...

You can speculate it, but I've actually investigated and modelled it. When you have two compression devices in series, the pressures multiply - that's why it's (erroneously) called compounding. If you have an "already spooled" turbo delivering, say, 2 bar absolute, and the SC downstream delivering, say, 1.7 bar absolute (0.7 plus atmospheric, to use your numbers), the result is 3.4 bar abs (2.4 bar boost). At that moment, when you disengage the SC, you don't just subtract its 0.7 bar boost contribution, but you return to 2 bar absolute from the turbo only. That's what I mean by the "step" in manifold pressure. There are ways to mitigate the step by sophisticated control, which I investigate in my thesis. Although it's for a 2-stage turbo system in an Otto engine, most of its findings nevertheless apply to a coupled SC/TC setup and for Diesels as well.

 

[Fix_Until_Broke]

There's a few options for a bypass valve (if you really think you need a 3" one...?)

A large wastegate will work

Else look up 059 145 901 C

 

[miniCotulla]

You can speculate it, but I've actually investigated and modelled it. When you have two compression devices in series, the pressures multiply - that's why it's (erroneously) called compounding. If you have an "already spooled" turbo delivering, say, 2 bar absolute, and the SC downstream delivering, say, 1.7 bar absolute (0.7 plus atmospheric, to use your numbers), the result is 3.4 bar abs (2.4 bar boost). At that moment, when you disengage the SC, you don't just subtract its 0.7 bar boost contribution, but you return to 2 bar absolute from the turbo only. That's what I mean by the "step" in manifold pressure. There are ways to mitigate the step by sophisticated control, which I investigate in my thesis. Although it's for a 2-stage turbo system in an Otto engine, most of its findings nevertheless apply to a coupled SC/TC setup and for Diesels as well.

As far as I understand a roots style SC can't be used for compounding as it doesn't compress the air itself. It acts as an air pump. As soon as there is more pressure on the inlet of SC it doesn't contribute anything to the system anymore.

 

[miniCotulla]

There's a few options for a bypass valve (if you really think you need a 3" one...?)

A large wastegate will work

Else look up 059 145 901 C

How is 059 145 901 C controlled? Just by changing the spring to make it open on different pressures?

 

[adamss24]

I still believe a compound turbocharger system as in the 2.0 tdi biturbo from the crafter engine, Mercedes’ 2.2cdi engine is the way to go however you can try the 3.0d bmw engine or the 3.0 tdi Audi biturbo engine !
The crafter biturbo setup is the smallest in its class, the Mercedes is the 2nd smaller and the bmw twin turbo is the largest there is !
A few years ago I was contemplating the same idea in a 1.9 tdi golf mk2 however I realised a single, large hybrid turbo is more than adequate and it kept the reliability issues down to nothing ! I still have the twin turbo Mercedes setup if you want me to take some measurements however is quite a large Jobbie to fit in the already crammed b5 engine bay !
I suggest you look at the Passat/arteon twin turbo setup, it delivers 245bhp in stock form and goes over 300 bhp with a remap however that engine breathes a lot better and the stage inter cooling is done already from the factory !

 

[miniCotulla]

I still believe a compound turbocharger system as in the 2.0 tdi biturbo from the crafter engine, Mercedes’ 2.2cdi engine is the way to go however you can try the 3.0d bmw engine or the 3.0 tdi Audi biturbo engine !

In theory yes but also no as there is really no space for two turbos without removing the airbox. Furthermore the only tuner that would do such a project told me to size the two turbos really close together to make control easier, essentially negating the the benefits of compound charging. He doesn't like the idea of bypass valves as I have no way of controlling them.

The Supercharger can live on the other side of the engine and delivers boost at idle which should completely get rid of the hard hill starts.

 

[miniCotulla]

I still believe a compound turbocharger system as in the 2.0 tdi biturbo from the crafter engine, Mercedes’ 2.2cdi engine is the way to go however you can try the 3.0d bmw engine or the 3.0 tdi Audi biturbo engine !
The crafter biturbo setup is the smallest in its class, the Mercedes is the 2nd smaller and the bmw twin turbo is the largest there is !
A few years ago I was contemplating the same idea in a 1.9 tdi golf mk2 however I realised a single, large hybrid turbo is more than adequate and it kept the reliability issues down to nothing ! I still have the twin turbo Mercedes setup if you want me to take some measurements however is quite a large Jobbie to fit in the already crammed b5 engine bay !
I suggest you look at the Passat/arteon twin turbo setup, it delivers 245bhp in stock form and goes over 300 bhp with a remap however that engine breathes a lot better and the stage inter cooling is done already from the factory !

The B5 engine bay actually isn't crammed. It's just that the turbo side is crammed, the other side isn't and has lots of room to play with.

Newer passats and the arteon also have transverse engine layouts aka just a golf and won't fit in a longitudinal setup.

 

[diffas]

Semes like you have figured your setup out so it needs to build now. Go for it!

 

[miniCotulla]

Semes like you have figured your setup out so it needs to build now. Go for it!

Let's see. If TDIMeister is correct and there is no good solution to avoid a step it might have to change.

I need the car in winter anyways, this can start in March at the soonest.

 

[Fix_Until_Broke]

How is 059 145 901 C controlled? Just by changing the spring to make it open on different pressures?

Physics - When the pressure on one side is higher than the other + the spring force, it opens

I'd recommend not trying to control it (a bypass in general) - control the SC behind it or the turbo in front of it and let the bypass do it's thing.
If your tuner wants the turbo's similarly sized, you may want to investigate other tuning options.
A roots SC can be used for compounding - it grabs air from one side and pushes it to the other side

 

[miniCotulla]

Physics - When the pressure on one side is higher than the other + the spring force, it opens

I'd recommend not trying to control it (a bypass in general) - control the SC behind it or the turbo in front of it and let the bypass do it's thing.
If your tuner wants the turbo's similarly sized, you may want to investigate other tuning options.
A roots SC can be used for compounding - it grabs air from one side and pushes it to the other side

Ok but in this setup the pressure would always be lower before the SC. This valve would never open.

Running full compound would be possible but I think this will kill efficiency.

 

[miniCotulla]

Physics - When the pressure on one side is higher than the other + the spring force, it opens

I'd recommend not trying to control it (a bypass in general) - control the SC behind it or the turbo in front of it and let the bypass do it's thing.
If your tuner wants the turbo's similarly sized, you may want to investigate other tuning options.
A roots SC can be used for compounding - it grabs air from one side and pushes it to the other side

As far as I understand I would have to disconnect the SC clutch before this bypass can open, resulting in a massive pressure drop. Is there a way to avoid this? At lower RPMs I probably can't inject as much fuel as there is air with this setup anyways, so I would have to tune around this in the ECU to ignore that sudden drop in pressure.

 

[altz1]

Does the Eaton m62 has bypass valve inside? If yes, could use this to slowly bypass SC before opening clutch.

 

[miniCotulla]

Does the Eaton m62 has bypass valve inside? If yes, could use this to slowly bypass SC before opening clutch.

Nope, but I had the same idea with an extra blow of valve opening just over the pressure the SC delivers on its own. And after that disengaging the clutch. With the Audi Bypass valve that @Fix_Until_Broke mentioned this should allow a free flow for the turbo once the SC is turned off.

 

[Fix_Until_Broke]

Maybe I'm oversimplifying this, but...If you put a 3L fixed displacement supercharger on a 2L engine (corrected for the relative displacement vs shaft speed, etc), as far as the turbo is concerned, it's a 3L engine. Size the turbo for the mass airflow (power) and pressure ratio that you want and that's it. The pressure ratio that you need for a 2L engine at XX power is much different than a 3L engine at the same power and RPM, so the idea of bypassing the SC is a bit confusing for me.

Some crackpot ideas below...
You could put the SC first, feeding the turbo with the Audi bypass around the SC so once the turbo spools it'll draw around the SC as necessary. The bypass spring is very light. Low RPM, pre-spool operation the SC will just push through the turbo.

You could go twin turbos, they don't need to be in close proximity - plenty of options there.

You could go SC only and throttle the air into the SC to unload it at low power/airflow operation for improved efficiency (though with some added throttling losses)

You could do the turbo --> supercharger combo with the bypass around the SC and a throttle in front of the SC effectively unloading it and forcing the air around the bypass. Most of these throttle discussions wouldn't need to be crazy restrictive, just enough to balance things out. Lots more control strategy required though.


Curious to see what you end up with and how it works!

 

[miniCotulla]

Maybe I'm oversimplifying this, but...If you put a 3L fixed displacement supercharger on a 2L engine (corrected for the relative displacement vs shaft speed, etc), as far as the turbo is concerned, it's a 3L engine. Size the turbo for the mass airflow (power) and pressure ratio that you want and that's it. The pressure ratio that you need for a 2L engine at XX power is much different than a 3L engine at the same power and RPM, so the idea of bypassing the SC is a bit confusing for me.

Some crackpot ideas below...
You could put the SC first, feeding the turbo with the Audi bypass around the SC so once the turbo spools it'll draw around the SC as necessary. The bypass spring is very light. Low RPM, pre-spool operation the SC will just push through the turbo.

You could go twin turbos, they don't need to be in close proximity - plenty of options there.

You could go SC only and throttle the air into the SC to unload it at low power/airflow operation for improved efficiency (though with some added throttling losses)

You could do the turbo --> supercharger combo with the bypass around the SC and a throttle in front of the SC effectively unloading it and forcing the air around the bypass. Most of these throttle discussions wouldn't need to be crazy restrictive, just enough to balance things out. Lots more control strategy required though.


Curious to see what you end up with and how it works!

The supercharger has 1 Liter displacement. I want to bypass it as there is no need for 3 bars+ and it would be really inefficient as the SC on full rpm robs 30HP and puts a lot of heat into the system. I would like it to only help the turbo spool up.

Putting the SC first would require an insane amount of piping as the SC is on the other side of the engine.

Twinturbos are really hard to implement in the space I have and I don't have a tuner that is confident tuning this kind of setup. Sizing the turbos is another issue. There are no compressor maps for most of the popular turbos out there.

Turbo+SC+throttle: do you mean like a throttle body? I have seen this on smaller Mercedes superchargers.

 

[turbobrick240]

An electric supercharger from something like the Audi SQ7 would be interesting.

 

[miniCotulla]

An electric supercharger from something like the Audi SQ7 would be interesting.

This needs 48V, so no use in an old car

 

[Fix_Until_Broke]

48V is a very solvable problem - just the supercharger needs that, not the whole car...

 

[miniCotulla]

48V is a very solvable problem - just the supercharger needs that, not the whole car...

Yes 48V is easy, the amperage this electric turbo/supercharger needs is not.

 

[Fix_Until_Broke]

How many amps does it need?

 

[turbobrick240]

145 amps@48V for the 7KW blower. The SQ7 has a 3KW generator charging a 48V battery to power it.

 

[Fix_Until_Broke]

Whew! Maybe replace the supercharger with a 2nd alternator at 48v?

 

[adamss24]

Did you look at Volvo’s s60 biturbo/compound system ? Is as compact as it gets, get the large turbo hybridised with a billet compressor and you should have your cake and eat-it ! I reckon it will do your requested boost low down and it will be reasonable easy to implement as everything’s vacuum controlled including the bypass valve ! Loose the emission implements (egr,etc.) and you should have a decent spooling combo which can work in longitudinal engines !