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slalombuggy
Samba Member
Joined: July 17, 2010
Posts: 9147
Location: Canada
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 Posted: Sat May 04, 2019 6:48 am Post subject: Re: Twin Turbo Kit |
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My favorite compound turbo engine is in the Joint Venture truck. 4 90mm turbos feeding 2 10-71 superchargers blowing into a V16 2 stroke diesel tugboat engine.
brad |
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Chip 
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Sat May 04, 2019 8:16 am Post subject: Re: Twin Turbo Kit |
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| clonebug wrote: |
Forget the parallel twins..... twins in series would be the way to go.
Have the small turbo fed air by the big turbo.
Under low demand the small turbo would basically draw air through the big one but at high power levels the big one would feed pressurized air to the little one for a compound boost level.
This is kind of interesting......lots of info on youtube on compound, sequential turbos if you want power. You have to weed through the BS. |
Here is my attempt. Started this project a little over a year ago. Decided it's time to move forward again. Pulled the single off and bolted back on the compound cartridge. Just needs a couple hoses made and it should be ready to rock and roll.
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FullFender
Samba Member
Joined: October 25, 2014
Posts: 647
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| Posted: Sat May 04, 2019 8:54 am Post subject: Re: Twin Turbo Kit |
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| oprn wrote: |
| I would also be very concerned about the small turbo grenading from overspeed when the big turbo came on strong!. |
At first youd think so, but when the large turbo comes on all it is doing is raising what the small turbo thinks is atmospheric pressure. So a single turbo would see roughly 14.5 lbs/square inch of AP, add a second turbo (compound) running 20lbs of BOOST pressure. Now your smaller turbo thinks atmospheric pressure is 34.5lbs (20lbsBP + 14.5lbsAP) and adds 10lbs of boost pressure to the mix. Now we are left with 30lbs of compounded boost pressure that reaches the engine (subtracted 14.5 for atmospheric). I think I got that right   In the video, he is has an internal gate in the small turbo, and an external wastegate in the manifold that bypasses the smaller turbo and dumps into exhaust right before the large
| Chip B. wrote: |
Here is my attempt. Started this project a little over a year ago. Decided it's time to move forward again. Pulled the single off and bolted back on the compound cartridge. Just needs a couple hoses made and it should be ready to rock and roll.
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Looks great! What size is the motor? Turbos? |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Sat May 04, 2019 9:13 am Post subject: Re: Twin Turbo Kit |
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Thank you! This is just my theory test setup. If it yields a really good result I'll make an attempt at packaging it a little cleaner. I just wanted to do this as cheap as possible at this stage.
Engine is a 2276, turbos are Subaru flanged td05-16g and t3/t04e.
I eliminated the internal gate on the Subie turbo, mainly for the ability to clock the little guy however was needed. I just run 2 external 38mm gates now. |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12743
Location: Western Canada
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| Posted: Sat May 04, 2019 9:45 pm Post subject: Re: Twin Turbo Kit |
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| FullFender wrote: |
| At first youd think so, but when the large turbo comes on all it is doing is raising what the small turbo thinks is atmospheric pressure. So a single turbo would see roughly 14.5 lbs/square inch of AP, add a second turbo (compound) running 20lbs of BOOST pressure. Now your smaller turbo thinks atmospheric pressure is 34.5lbs (20lbsBP + 14.5lbsAP) and adds 10lbs of boost pressure to the mix. Now we are left with 30lbs of compounded boost pressure that reaches the engine (subtracted 14.5 for atmospheric). I think I got that right In the video, he is has an internal gate in the small turbo, and an external wastegate in the manifold that bypasses the smaller turbo and dumps into exhaust right before the large |
Ok, that makes sense I think. The small turbo is seeing a higher density air so it is actually being asked to move a larger mass of air or in other words is is being loaded heavier? Overspeed is more of a thing that happens when a turbo is unloaded - as in throttle shut upstream of the inlet? |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26790
Location: Colorado Springs
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| Posted: Sat May 04, 2019 9:49 pm Post subject: Re: Twin Turbo Kit |
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Putting an intercooler between the two turbos it makes even more sense.
Same type of advantage as a two stage air compressor. |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Sun May 05, 2019 1:07 am Post subject: Re: Twin Turbo Kit |
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| modok wrote: |
Putting an intercooler between the two turbos it makes even more sense.
Same type of advantage as a two stage air compressor. |
This is definitely something that will be addressed in V2, if it goes that far. For now, I'll just have one after the pair. |
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FullFender
Samba Member
Joined: October 25, 2014
Posts: 647
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| Posted: Sun May 05, 2019 8:02 am Post subject: Re: Twin Turbo Kit |
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| oprn wrote: |
Ok, that makes sense I think. The small turbo is seeing a higher density air so it is actually being asked to move a larger mass of air or in other words is is being loaded heavier? Overspeed is more of a thing that happens when a turbo is unloaded - as in throttle shut upstream of the inlet? |
You got it. In a compound turbo system, the larger turbo is considered low pressure, and smaller turbo considered high pressure. Overspeed is when you have no regulation of boost pressure, like running without a wastegate. That causes excessive boost spikes, and spins the turbo past its operational/safe point. It can still happen with a wastegate if you run more boost than it can handle. |
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clonebug
Samba Member
Joined: January 29, 2005
Posts: 4028
Location: NW Washington
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| Posted: Sun May 05, 2019 8:29 am Post subject: Re: Twin Turbo Kit |
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| modok wrote: |
Putting an intercooler between the two turbos it makes even more sense.
Same type of advantage as a two stage air compressor. |
W/I gives really good results.....
_________________
| vwracerdave wrote: |
Take a good long look in the mirror and report back on what you see. |
| Paul.H wrote: |
| That one line on that chart is probably better info than you can get from this place in a month |
My Megasquirt Fuel Injection Turbo Buggy Build
Water/Alcohol Injection
Audi TT intercooler
Upgraded to MS3Pro-Evo
EcuMaster PMU16
ECUMaster ADU5 Digital Dash
http://www.shoptalkforums.com/viewtopic.php?f=3&t=127936 |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12743
Location: Western Canada
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| Posted: Sun May 05, 2019 3:21 pm Post subject: Re: Twin Turbo Kit |
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| Purely academic interest on my part, I doubt I will ever have the budget to play that hard! |
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theDrew
Samba Member
Joined: May 17, 2011
Posts: 1155
Location: Camas, WA
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| Posted: Mon May 06, 2019 7:54 am Post subject: Re: Twin Turbo Kit |
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ChipB -- what are your target boost pressures? Cool stuff, I'd love to hear the results of your science experiment.
_________________
Turbo 2276 MS3X build http://www.thesamba.com/vw/forum/viewtopic.php?t=673125
1985 Vanagon Campmobile w/ 2005 EJ25 |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Mon May 06, 2019 8:48 am Post subject: Re: Twin Turbo Kit |
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| theDrew wrote: |
| ChipB -- what are your target boost pressures? Cool stuff, I'd love to hear the results of your science experiment. |
Probably pretty similar to now, mid to high 20's. I am more looking for the fast spool of the little turbo, and the flow of the big one. My current setup doesn't really start spooling until 4000+, which is fine on a race track and fun on the street. But I intend to spend much less time on the track than in recent years and want to enjoy the turbo power more on the street without having to rev it to the moon(sure is fun though!) Honestly I could probably just invest in a really nice modern turbo and get the best of both worlds. But, I had most of this stuff laying around, and figured it was worth a shot. |
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theDrew
Samba Member
Joined: May 17, 2011
Posts: 1155
Location: Camas, WA
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| Posted: Mon May 06, 2019 9:05 am Post subject: Re: Twin Turbo Kit |
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well i wish you luck with it -- I've been planning on moving to a ball bearing brand name turbo one of these days to help with spool earlier in the RPM range...man they dont give those away tho!
_________________
Turbo 2276 MS3X build http://www.thesamba.com/vw/forum/viewtopic.php?t=673125
1985 Vanagon Campmobile w/ 2005 EJ25 |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Mon May 06, 2019 9:47 am Post subject: Re: Twin Turbo Kit |
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| theDrew wrote: |
| well i wish you luck with it -- I've been planning on moving to a ball bearing brand name turbo one of these days to help with spool earlier in the RPM range...man they dont give those away tho! |
Nope, the Garrett Gen 2 GTX stuff looks pretty sweet. |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Fri May 31, 2019 8:01 am Post subject: Re: Twin Turbo Kit |
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Link
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theDrew
Samba Member
Joined: May 17, 2011
Posts: 1155
Location: Camas, WA
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Fri May 31, 2019 9:51 am Post subject: Re: Twin Turbo Kit |
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| theDrew wrote: |
| nice! test spin yet? |
Not yet, ran out of vacuum line for 2nd wastegate and sensor plumbing. Picked that up last night, need to get out there this morning to finish it. |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Fri Oct 09, 2020 9:53 pm Post subject: Re: Twin Turbo Kit |
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| Been a while since I first started that compound setup. Totally forgot about this thread until scrolling through the my replys section. Unfortunately I only had the setup on the road for about a month. I put a few hundred mile on it during that time though and definitely saw some interesting results. Other issues made me pull the engine out of the car and eventually I pulled the plug on the compound project all together. I never had the car on a dyno or anything, but the limited driving I did showed real promise from the system. The big turbo in the compound setup had previously been on the engine as a single and really didn't start making boost until 400-4500rpm. With the compound setup, I was seeing 20psi by 4000rpm. My wastegate strategy wasn't working very well though and as the big turbo spooled up, the little turbo slowed down, so I didn't see much of a compound effect, more like a transition. I had a map sensor placed after the pair of turbos, and also one between them, so could see the spool of each unit individually. Another thing that happened over and over was that the big turbo would shoot way over its target pressure. The fast spool was cool though. I had plans to relocate one of the wastegates to a better spot, but then never got there. The engine was wounded before I even started this project, I didn't know how bad until I tore it apart later, but it sure wasn't healthy and I could tell. My plan after this was to attempt to package that mess under the car in a way that would allow me to retain the closed decklid and stealth look of the car. However as I tried to make changes to the engine while it was apart, I realized that the 2 turbo thing just wasn't ideal for what I was trying to do. The turbos I was using were old, turbo technology has come a long way since I purchased the t3/t04e back in 2012. I decided that life would be way simpler if I just bought a nice new tech big single instead. Packaging is easier, tuning will be easier, power potential is much higher, and hopefully spool is better than my previous single was delivering. In conclusion, I think the compound thing definitely has merit. But its gonna require some tinkering to get the system optimized. I know of others that are looking to jump in and continue down the path. Hopefully they will share their progress. |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12743
Location: Western Canada
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| Posted: Sat Oct 10, 2020 5:29 am Post subject: Re: Twin Turbo Kit |
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Thanks for the update!
My gut feeling is that achieving the correct balance in turbo sizing between the engine displacement and between the two turbos is going to be the key to success. You and I don't have the budget for that kind of R&D! Just picking random turbos may prove to work somewhat at some point but is time consuming to say the least and expensive for sure.
Too many guys that do home turbos shoot for the moon on HP and end up with something far less than ideal in my view. I think that is what lead you down the twin turbo path in the first place.
VW is doing the twin turbo thing now with the TSI model so they have invested in the R&D already. It would be interesting to put that turbo package as is on an air cooled VW and see how it works out. The engine in my daughter's TSI Jetta is a 1600 so that would be the place to start with an air cooled one. |
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buguy
Samba Member
Joined: November 17, 2003
Posts: 4915
Location: Port Orange, FL
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| Posted: Sat Oct 10, 2020 6:42 am Post subject: Re: Twin Turbo Kit |
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| I think chip nailed it, turbo technology has greatly improved making the need for twins more obsolete. Certainly does look cool though. I love the look of a well laid out and welded header like the OP though! |
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