XUD Compound turbo project.

[ADV_93]

Im looking to start a project on my car in which i use compound twin turbo set up. Just a few things i need some help with are...
1. which turbochargers do i use?
2. How do i look at set it up right. Im currently rebuilding a strengthened XUD. 
If anyone could help me out, would be appreciated, thanks.

[Seb_Ryan]

Problem you have is not many people have done it.. Youll need to study alot of compressor maps for turbos to work it out, i doubt people who have spent weeks working it out will just share it with everyone unfortunately

[zx_volcane]

Just out of interest, what is drawing you to a compound setup?

For all out power or increased power range over revs?

A suitably sized modern vnt will suit most setups and give good power / spool


That being said, I can understand wanting two turbos under the bonnet just becasueracecar

You'll want a smallish vnt for hp and a large wastegate for the lp - although some research into good combos will be needed. There are a few that have done it on similarly sized diesels, so perhaps a bit of a google might bring up some good turbo combos.

[Piggy]

all what he said ^^^^

[Ruan]

First thing to do is to really get to grips with what you're looking at and understanding compressor maps, figure the maths behind how much airflow you want/need... Once you've got that under your belt then the sizing of the turbochargers will fall into place...

Get out of the idea of "one to spool fast", "one for high rpms" - they have to be matched better than just lobbing two turbos together, you need to not only know their spool characteristics, but their characteristics at high pressure/low flow and low pressure/high flow - two seemingly identical turbochargers can have two totally different characteristics in terms of how they perform with regards to pressure/flow.

Compounding is win, but exactly as Tom said above, you can likely get similar performance to what your injection pump will provide, or exceed what a realistic VE pump without extreme (and detrimental to driveability) modification with a good, modern variable nozzle turbocharger... End of the day, you can now buy small diesel suitable 350hp capable Garrett VNT turbochargers off the shelf!

[ADV_93]

First thing to do is to really get to grips with what you're looking at and understanding compressor maps, figure the maths behind how much airflow you want/need... Once you've got that under your belt then the sizing of the turbochargers will fall into place...

Get out of the idea of "one to spool fast", "one for high rpms" - they have to be matched better than just lobbing two turbos together, you need to not only know their spool characteristics, but their characteristics at high pressure/low flow and low pressure/high flow - two seemingly identical turbochargers can have two totally different characteristics in terms of how they perform with regards to pressure/flow.

Compounding is win, but exactly as Tom said above, you can likely get similar performance to what your injection pump will provide, or exceed what a realistic VE pump without extreme (and detrimental to driveability) modification with a good, modern variable nozzle turbocharger... End of the day, you can now buy small diesel suitable 350hp capable Garrett VNT turbochargers off the shelf!

I am seriously considering VNT but then it's getting it to work. It's very hard/impossible to get a VNT to work mechanically. Mapping and electronics seems complicated to me at the moment, but i like to do all the work myself. Also the reason for the compound setup is because it's full of win. I've researched a lot into compounding and i understand it, but i'm not too familiar with compressor maps. 

[Piggy]

 I've researched a lot into compounding and i understand it, but i'm not too familiar with compressor maps. 

Oxymoron right there.

Also, who told you a VNT controlled by a boost can is hard/impossible to setup?? I have the arduino system, and I also ran boost can...boost can took me about 45min to get setup.

Arduino still isnt right after £100-150 of bits and days and days and days and days of work!

[silverzx]

That's because Arduino's are sh1t.

[mr_fish]

VNT on a boost can is fine, just making the fitment to the engine/exhaust and mounting the can will take you the time.

Piggy has the benefit of working on fairly easily. When its down the back its a bit of a twunt.

[Sambarker]

VNT on a boost can is fine, just making the fitment to the engine/exhaust and mounting the can will take you the time.

Piggy has the benefit of working on fairly easily. When its down the back its a bit of a twunt.

This was last weekends project on the 305

[Chairchild]

mechanical vnt control is pants at best, and an exhaust brake at worst. Did my dissertation on the subject - one setup gave so much resistance, we couldn't start the engine! lol

[Piggy]

If thats the case then you set the vane stop incorrectly

[Dum-Dum]

Basic mechanical control of a VNT with a boost can is INCREDIBLY easy. Yes you can make it so restrictive it wont start and yes you could screw it out so much you would never come on boost but if you understand the difference between what the 2 screws do and have an EMP set up then tuning is easy enough.

The only thing I would want would be either a better knowledge of the travel of different boost cans at different pressures or to be able to adjust the length of the VNT operation lever but that's pretty advanced thoughts really (although still not as hard as sorting a decent compound set up)

This is how a boost can works a VNT https://www.youtube.com/watch?v=QtqfNFnnps4

[Chairchild]

The only thing I would want would be either a better knowledge of the travel of different boost cans at different pressures or to be able to adjust the length of the VNT operation lever but that's pretty advanced thoughts really

Or.. you make your own, with adjustable spring rates. One for boost reference, one for EMP reference, and a throttle controlled camplate




Like I did


and the extracted dyno info:



power line is all over the place - which is why I said it was toss




As for compound, got a few setups in play atm - with this being the latest "food for thought" setup



Still got a lot of work to do on the overall design - but the general gist is 8kw of power, 20:1 gearing, self-contained oil supply. Expected to supply boost for 10-15 seconds at a time - NOT continuous boost

Here's the donor HX55 turbo, for size comparison



Just 4 teh lulz

[Dum-Dum]

The only thing I would want would be either a better knowledge of the travel of different boost cans at different pressures or to be able to adjust the length of the VNT operation lever but that's pretty advanced thoughts really

Or.. you make your own, with adjustable spring rates. One for boost reference, one for EMP reference, and a throttle controlled camplate




Like I did

That is f*cking ridiculous

[bashbarnard]

By the time you've done that couldve done a proper ecu imo

[zx_volcane]

Good on you for putting all that together and doing some proper research, you had it on a proper engine dyno aswell? Brilliant imo

Was this part of a course, dissertation or similar?

As a lashup, a vnt on a boost can is a quick way of getting them to work to a certain degree. plenty fine for a cheap peugeot and overal way betetr than a wg equivalent

but just as your dyno graphs shows, if you wind them up for spool, they choke up initially until the vanes open and then flow better as they get on - hence the dip.

electronic vnt control is pretty complex and really does need a ton of live mapping to fine tune it all - needs a mix of open and closed loop control to get it nailed perfectly - and that would be just for one combination of engine + turbo + fuel + power

[Chairchild]

Dissertation subject for my BEng degree in Automotive Engineering I was supposed to have a budget of £50, but the engine rig itself ran to over £1k in costs, lol. Machining time for the rest of the controller was estimated to have "cost" about £5k, if it wasn't done by the uni technicians in the workshop.

I've got a Diploma in electronics engineering too, so avoided doing a proper ecu, because I knew it *could* be done. And where would the fun be in that?

I don't have any clear pictures of the final complete engine rig - but I've got plenty of the build:











Annoyingly, the proper controller STILL lies unfinished... it's missing the two link rods and cam setup



So this was thrown together instead - preload was adjusted with washers/turbo bearings, lol






And yes, any vnt control is unique to each engine/turbo combination. You wouldn't believe the amount of people who fit bigger/hybrid vnt turbos to a remapped car, and wonder why the ecu throws a wobbly! But keep an eye on this fella:

https://www.facebook.com/dieselpowered?fref=ts

As he's in the process of manufacturing standalone vnt controllers, which can be easily mapped to suit your setup

[Poodle]

Wow lol, shame it's bigger than the turbo and useless for applying in an engine bay really.

[Dum-Dum]

The lash up version actually makes it easier to understand whats going on.

VAG 1.6 diesel?

[ADV_93]

 I've researched a lot into compounding and i understand it, but i'm not too familiar with compressor maps. 

Oxymoron right there.

Also, who told you a VNT controlled by a boost can is hard/impossible to setup?? I have the arduino system, and I also ran boost can...boost can took me about 45min to get setup.

Arduino still isnt right after £100-150 of bits and days and days and days and days of work!

How contradictory? I understand the compound setup, but not how to read a compressor map. Put your horse back in its stable.

---

Basic mechanical control of a VNT with a boost can is INCREDIBLY easy. Yes you can make it so restrictive it wont start and yes you could screw it out so much you would never come on boost but if you understand the difference between what the 2 screws do and have an EMP set up then tuning is easy enough.

The only thing I would want would be either a better knowledge of the travel of different boost cans at different pressures or to be able to adjust the length of the VNT operation lever but that's pretty advanced thoughts really (although still not as hard as sorting a decent compound set up)

This is how a boost can works a VNT https://www.youtube.com/watch?v=QtqfNFnnps4

Is this simply opening the actuator and putting the spring underneath the diaphragm then closing it back up? I'm guessing you still have the full boost at cruise with this set up?

[Piggy]

You said you had researched a lot into compounding...

You can't research into compounding without researching compressor maps.