-
TDR Magazine subscribers receive more than the magazine! You also gain additional forum privileges!
Details here: TDR Privileges
Subscribe to TDR Magazine here: https://www.tdr-online.com/
Engine/Transmission (1994 - 1998) Twin turbo set-up?
- Thread starter DBR
- Start Date
Attention: TDR Forum Junkies To the point: Click this link and check out the Front Page News story(ies) where we are tracking the introduction of the 2025 Ram HD trucks.
Thanks, TDR Staff
- Status
The twin turbo setups that I have seen use a modified HX-35 as the smaller primary (or secondary... depending on how you look at things... )... . and then a great big Garrett... like a T-88 or bigger as the secondary.
I'd think that the secondary would have to have a really big turbine housing to make things work right..... otherwise you are choking the exhaust twice and defeating the purpose. When exhaust flows from an area of smaller diameter to an area of larger diameter, it accelerates..... so if you had similarly sized turbine housings the exhaust acceleration that makes using the big turbine housing possible wouldn't exist. Big turbine housing = lots of exhaust flow to get it going... but once it is going, the hopefully LARGE compressor wheel attached to it's shaft is moving a lot of air. The compounded twins idea works great for this reason... . the little one helps the big one get going, and in turn the big one compresses the atmospheric air charge before the little one further compresses it... so you get LOTS o' BOOST!
Perhaps someone who's 'in the know' would be better suited to answer this query correctly. *HINT, HINT*
Matt
I'd think that the secondary would have to have a really big turbine housing to make things work right..... otherwise you are choking the exhaust twice and defeating the purpose. When exhaust flows from an area of smaller diameter to an area of larger diameter, it accelerates..... so if you had similarly sized turbine housings the exhaust acceleration that makes using the big turbine housing possible wouldn't exist. Big turbine housing = lots of exhaust flow to get it going... but once it is going, the hopefully LARGE compressor wheel attached to it's shaft is moving a lot of air. The compounded twins idea works great for this reason... . the little one helps the big one get going, and in turn the big one compresses the atmospheric air charge before the little one further compresses it... so you get LOTS o' BOOST!
Perhaps someone who's 'in the know' would be better suited to answer this query correctly. *HINT, HINT*
Matt
I haven't yet, but will try that simply because I already have both turbos and the numbers are close.
The HX-40 isn't big enough to be the big turbo in a twin setup if you are running lots of boost and RPM.
My goal is an efficient 50 psi, and with an automatic I always keep her under 3200 rpm.
With these limitations, I'm still in the efficiency band of the HX-40 although who knows exactly what efficiency that is. Holset doesn't let out their complete efficiency maps for some reason.
I'm going to mount the HX-40 on the manifold so the hot gases go through it first then to the smaller turbo. The cooler air coming out of the first turbo will lose volume and the restrictions from the HX-35 should be lessened.
With the HX-40 on the manifold I should be able to keep the stock intake filter location.
I'll be sure to keep everyone posted on how it works out. The trouble is, there is really a LOT of work to mount and plumb in the second turbo. And to be honest, I'm intimidated right now.
For number gunkies, I suggest getting some turbocharger books like "Turbocharging" by Hugh McInnes. It walks you through crunching the numbers, picking the right turbos and even covers how to calculate for twins and intercooling.
-Chris
The HX-40 isn't big enough to be the big turbo in a twin setup if you are running lots of boost and RPM.
My goal is an efficient 50 psi, and with an automatic I always keep her under 3200 rpm.
With these limitations, I'm still in the efficiency band of the HX-40 although who knows exactly what efficiency that is. Holset doesn't let out their complete efficiency maps for some reason.
I'm going to mount the HX-40 on the manifold so the hot gases go through it first then to the smaller turbo. The cooler air coming out of the first turbo will lose volume and the restrictions from the HX-35 should be lessened.
With the HX-40 on the manifold I should be able to keep the stock intake filter location.
I'll be sure to keep everyone posted on how it works out. The trouble is, there is really a LOT of work to mount and plumb in the second turbo. And to be honest, I'm intimidated right now.
For number gunkies, I suggest getting some turbocharger books like "Turbocharging" by Hugh McInnes. It walks you through crunching the numbers, picking the right turbos and even covers how to calculate for twins and intercooling.
-Chris
here is some of the stuff I've learned about twins(for the second time after darn computer shutdown on about the 5th paragraph the first time grrrrrr)
hx35 flows 600 cfm at 36psi, hx40 flows 800cfm at 40psi, h2e/hx50 flow 1000cfm at 40psi(h2e doesn't go off its map until 48 psi and has one of the highest p/r wheels holset offers), hx55 flows 1050 cfm, and hx 60 flows 1600 cfm.
basically in order to make twins work and funtion correctly in series they are set up to multiply boost. Ideally the first stage is the turbo responsible for spoolup(the one clossest to the motor), meaning it needs to have very little lag. The second stage is the one reponsible for collecting all the air neccessary for feeding the first stage turbo and meens that is has to be twice as big. In order to multiply boost correctly both turbos must operate in their maps to elimate over heating the air, hot air carries less oxygen. That means you should have both turbos operating at say 25psi so both are making the coolest air possible but have enough available to create huge amounts of boost, ie less egt. The problem is that an outside turbo large enough to sustain the amount of air necessary to supply 600hp(hx60 is off the signature 600) has a huge exhaust housing the would be fine for high rpm but would need to be hybrid by some one like Pias from Bell turbo in order to make it work in normal operating rpms that most of us including me drive in. That also applies to the inside turbo, in order to make the inside turbo fast enough and big enough you need to make use of a wastgate as to use a small enough housing to eliminate as much lag as posible and to flow enough to not be a bottleneck after max boost is achieved. I am currently using a Bell turbo hybrid h2e that is to be my inside turbo for my twins. This turbo is twice as fast(1400rpms) as my stock hx 40 16cm2(1800 maybe 1700rpm pickup) was. But sence I am not staged I can still only manage 38psi at 1300 degrees. I hope in the near future that I will have twins that I am confident everyone can use, and hopefully can afford.
maybe this helps,
Adam
hx35 flows 600 cfm at 36psi, hx40 flows 800cfm at 40psi, h2e/hx50 flow 1000cfm at 40psi(h2e doesn't go off its map until 48 psi and has one of the highest p/r wheels holset offers), hx55 flows 1050 cfm, and hx 60 flows 1600 cfm.
basically in order to make twins work and funtion correctly in series they are set up to multiply boost. Ideally the first stage is the turbo responsible for spoolup(the one clossest to the motor), meaning it needs to have very little lag. The second stage is the one reponsible for collecting all the air neccessary for feeding the first stage turbo and meens that is has to be twice as big. In order to multiply boost correctly both turbos must operate in their maps to elimate over heating the air, hot air carries less oxygen. That means you should have both turbos operating at say 25psi so both are making the coolest air possible but have enough available to create huge amounts of boost, ie less egt. The problem is that an outside turbo large enough to sustain the amount of air necessary to supply 600hp(hx60 is off the signature 600) has a huge exhaust housing the would be fine for high rpm but would need to be hybrid by some one like Pias from Bell turbo in order to make it work in normal operating rpms that most of us including me drive in. That also applies to the inside turbo, in order to make the inside turbo fast enough and big enough you need to make use of a wastgate as to use a small enough housing to eliminate as much lag as posible and to flow enough to not be a bottleneck after max boost is achieved. I am currently using a Bell turbo hybrid h2e that is to be my inside turbo for my twins. This turbo is twice as fast(1400rpms) as my stock hx 40 16cm2(1800 maybe 1700rpm pickup) was. But sence I am not staged I can still only manage 38psi at 1300 degrees. I hope in the near future that I will have twins that I am confident everyone can use, and hopefully can afford.
maybe this helps,
Adam
Thanks for the info, folks. I am currently working on the following project and perhaps you can provide some assistance. I have two hx35's and two hx40's to play with. I have the 12, 14, and 16 housings for the 35's as well as the16 and 18 for the 40's. My approach here is that there are many folks that have purchased the hx 40 and are no longer satisfied with that level of performance or, like me, are just wanting to try something different. . The outcome I wish to achieve is lower egts for towing and the elimination of low end lag. I have returned my truck to the following configuration: stock governor springs, 370's, delivery valves, and #11 fuel plate with Piers' hx35 and16cm housing. This combo is excellent for towing. I limit my fueling to achieve no more than 1350 egt. which puts me at around 32 psi on my turbo. My biggest concern is smoke while towing, or any driving for that matter. The hx40 works nice, but it comes at the cost of low end smoke.
My thinking here is to use the hx35 /12 as primary and the Hx 40/16 as secondary. I have already fabricated the exhaust side of the set up, which was much easier than I thought. I'm presently fabricating the piping for the cold side of the turbo. My intent here is to set the wastegate on the primary (hx35/12) to 20psi and then set the waste gate on the hx40 to 45 psi, taking the pressure signal from the same source. My goal is to increase the amount of boost I can deliver at the same fueling level and lower the egt to below 1250.
So any comments or ideas?
My thinking here is to use the hx35 /12 as primary and the Hx 40/16 as secondary. I have already fabricated the exhaust side of the set up, which was much easier than I thought. I'm presently fabricating the piping for the cold side of the turbo. My intent here is to set the wastegate on the primary (hx35/12) to 20psi and then set the waste gate on the hx40 to 45 psi, taking the pressure signal from the same source. My goal is to increase the amount of boost I can deliver at the same fueling level and lower the egt to below 1250.
So any comments or ideas?
Hello DBR
first off let me tell you what I think, well know. The only way to lower egts wile pulling is to sustain higher boost, the only way to do this is use more than one turbo. I have about the biggest turbo we can possibly use as a singe and I can still only sustain 38 psi at 1300. The only way to make more boost is by staging/multiply boost. I was told once that if I make 25psi from the outside turbo to the inside, then make 25 more with that I'd have 92psi. Both of these turbo would be operating well within their highest efficiency islands, meaning the coolest possible air in other word containing the most possible oxygen. I think your putting together a system with a 35(600cfm) on the inside that will spoolup fast even with a 14 to lessen backpressure, and keeping its boost down to around 15psi as to not cavatate that pump and building to much discharge temp. Then put the 40 around 30 psi before that inside turbo to keep from breaking shafts(the 40 has a 8mm shaft, same as the 35) because if you fragment that, there goes two turbos. Also If you spin it over 36 psi your taking it off its map. One thing to keep in mind here is the 40 is spinning 130k to make 40psi, the h2e/hx50 is only spinning 105k to make 42psi. The only problem hear is the h2 has the smallest of 17cm2 with a bigger R than a hx40 also no waistgate. Once again hybrid is the best solution for this. If not your going to have a 50psi max system, maybe.
I think the 35 will work for the inside, just not the outside.
first off let me tell you what I think, well know. The only way to lower egts wile pulling is to sustain higher boost, the only way to do this is use more than one turbo. I have about the biggest turbo we can possibly use as a singe and I can still only sustain 38 psi at 1300. The only way to make more boost is by staging/multiply boost. I was told once that if I make 25psi from the outside turbo to the inside, then make 25 more with that I'd have 92psi. Both of these turbo would be operating well within their highest efficiency islands, meaning the coolest possible air in other word containing the most possible oxygen. I think your putting together a system with a 35(600cfm) on the inside that will spoolup fast even with a 14 to lessen backpressure, and keeping its boost down to around 15psi as to not cavatate that pump and building to much discharge temp. Then put the 40 around 30 psi before that inside turbo to keep from breaking shafts(the 40 has a 8mm shaft, same as the 35) because if you fragment that, there goes two turbos. Also If you spin it over 36 psi your taking it off its map. One thing to keep in mind here is the 40 is spinning 130k to make 40psi, the h2e/hx50 is only spinning 105k to make 42psi. The only problem hear is the h2 has the smallest of 17cm2 with a bigger R than a hx40 also no waistgate. Once again hybrid is the best solution for this. If not your going to have a 50psi max system, maybe.
I think the 35 will work for the inside, just not the outside.
I think it will work nicely.
My concern is spoolup speed. Turbos are of course driven by the difference in thermal energy across them. With a single turbo, you have the entire difference from manifold conditions to downpipe conditions driving the turbo. With a twin setup, you have only the difference between the manifold conditions and the intermediate conditions driving your primary turbo which is less than the energy available with a single turbo if ANY energy AT ALL is being extracted from the second turbo.
Once you get it up and running you need to try to get both turbos to have the same pressure ratio. You adjust this by swapping out your exhaust housings. This doesn't mean 22. 5 psi for the first turbo and 45 psi for the second.
With an overall limit of 45 psi as you mentioned.
45psi = pressure ratio of 4. 06
You would then need a pressure ratio of 2. 01 across each turbo at max boost. You multiply the pressure ratios just as Adam says above.
This would result in only 15 psi coming from the first turbo.
I can't wait to hear more about this. Mainly what exhaust housings you end up with and how fast the spool up is.
Don't get scared from the above comments about boost limits. In this setup, although the HX-40 is producing 30 psi of boost, it will be operating at a 2. 01 pressure ratio, and as far as the HX40 can tell, it will be producing only 15psi of boost and has a LOT of room for more.
You select turbos by calculatiing pressure ratios and flow rates to find efficiency bands. Talking about turbo limits and using BOOST PRESSURE as a limit only applies for single turbo systems. Don't be misled.
Good luck,
Chris
My concern is spoolup speed. Turbos are of course driven by the difference in thermal energy across them. With a single turbo, you have the entire difference from manifold conditions to downpipe conditions driving the turbo. With a twin setup, you have only the difference between the manifold conditions and the intermediate conditions driving your primary turbo which is less than the energy available with a single turbo if ANY energy AT ALL is being extracted from the second turbo.
Once you get it up and running you need to try to get both turbos to have the same pressure ratio. You adjust this by swapping out your exhaust housings. This doesn't mean 22. 5 psi for the first turbo and 45 psi for the second.
With an overall limit of 45 psi as you mentioned.
45psi = pressure ratio of 4. 06
You would then need a pressure ratio of 2. 01 across each turbo at max boost. You multiply the pressure ratios just as Adam says above.
This would result in only 15 psi coming from the first turbo.
I can't wait to hear more about this. Mainly what exhaust housings you end up with and how fast the spool up is.
Don't get scared from the above comments about boost limits. In this setup, although the HX-40 is producing 30 psi of boost, it will be operating at a 2. 01 pressure ratio, and as far as the HX40 can tell, it will be producing only 15psi of boost and has a LOT of room for more.
You select turbos by calculatiing pressure ratios and flow rates to find efficiency bands. Talking about turbo limits and using BOOST PRESSURE as a limit only applies for single turbo systems. Don't be misled.
Good luck,
Chris
Last edited:
trins
DBR,
there is a company that builds the twin turbo set up with all of the tubing and turbos. there web site is www.enterpriseengine.com. once at the home page go to special projects on the left side and that will be the set up.
DBR,
there is a company that builds the twin turbo set up with all of the tubing and turbos. there web site is www.enterpriseengine.com. once at the home page go to special projects on the left side and that will be the set up.
Okay, now I really have to move out closer to `yall!
On one hand:
I'd love to put together a twins setup on my own, but for the asking price that the folks that are selling their setups for it would almost be tough to beat 'em, especially seeing as they have already done the R&D and include everything soup to nutz. $450 for ATS manifold and at least $2k worth of turbos, and you haven't even started the whole plumber's nightmare yet... . getting close to the $4k quick-like.
On the other hand:
The personal satisfaction of saying that I (partially) designed and/or copied and built a twin turbo system for my truck would be unimaginable.
I'm going to be really patient on this one, I think for once that in the end everyone's going to be happy... no matter what route they choose.
Matt - sitting on the 'homemade'/'store-bought' twin turbo fence
On one hand:
I'd love to put together a twins setup on my own, but for the asking price that the folks that are selling their setups for it would almost be tough to beat 'em, especially seeing as they have already done the R&D and include everything soup to nutz. $450 for ATS manifold and at least $2k worth of turbos, and you haven't even started the whole plumber's nightmare yet... . getting close to the $4k quick-like.
On the other hand:
The personal satisfaction of saying that I (partially) designed and/or copied and built a twin turbo system for my truck would be unimaginable.
I'm going to be really patient on this one, I think for once that in the end everyone's going to be happy... no matter what route they choose.
Matt - sitting on the 'homemade'/'store-bought' twin turbo fence
I'd like to further clarify my motive so that there are no misunderstandings of my intentions. I'm not looking to copy or steal anyone else's R&D. If so, I would purchase one of the available twin turbo kits outright and merely copy them. In addition, it is not my goal to sell anything. My motive is to simply use the equipment that I (and many others) already have: the HX40 and the HX35. I don't believe that it is necessary to purchase an ATS manifold nor would one need to purchase additional turbos. The goal is to use what we already have. It may not be the best choice for twins, but it just may work for a mild 350 h. p. truck intended for towing. The twins that I have read about appear to be for the big boys striving for high h. p. numbers. I'm just attempting to assemble the hardware for a twin set-up cheaply and easily to produce a useful modification that I and other do-it
yourselfers could fabricate. The system may fail, but it is no great loss, I'm only out a few hundred bucks in hardware and some time in the shop. Thus far, the investment I have made in the fabrication of the exhaust side manifold totals $10 and the cold side is at $50 with several hours combined of planning and fabricating.
I would be more than willing to share what I have done if others are interested in my approach (I would be happy to attach photos to this posting if interested parties could provide information on how to do so).
I cannot stress enough that this project was not started as a means to compete with any of the vendors or to copy their designs. It was meant to be fun home project (these trucks are my hobby). This forum contains many very knowledgeable do-it-yourself type folks who bring their professional experiences (myself included) that make them more than capable of multi-staging two compressors, so those folks interested and want to contribute lets have some interesting dialog and see what develops .
yourselfers could fabricate. The system may fail, but it is no great loss, I'm only out a few hundred bucks in hardware and some time in the shop. Thus far, the investment I have made in the fabrication of the exhaust side manifold totals $10 and the cold side is at $50 with several hours combined of planning and fabricating.
I would be more than willing to share what I have done if others are interested in my approach (I would be happy to attach photos to this posting if interested parties could provide information on how to do so).
I cannot stress enough that this project was not started as a means to compete with any of the vendors or to copy their designs. It was meant to be fun home project (these trucks are my hobby). This forum contains many very knowledgeable do-it-yourself type folks who bring their professional experiences (myself included) that make them more than capable of multi-staging two compressors, so those folks interested and want to contribute lets have some interesting dialog and see what develops .
I'm with you, DBR. I don't want in any way to upset any of the vendors, and I sure as he|| do not plan on making any money off of any of my research for a couple of reasons: 1) I don't know enough about these trucks to reliably produce products that even work properly. 2) I lack the amount of time and financial resources to produce and distribute said products.
Diesels are a huge part of my life, but I have lots of other things I have to worry about. It is very unfortunate that it would be kinda hard for me to combine my major with diesels... . I'm so passionate about them.
I really hope that everyone can learn from not only this thread, but the Roundtable as a whole... . so far it has been invaluable to me!
Keep this thread goin'!!!!!
Matt - certifiable diesel fanatic
Diesels are a huge part of my life, but I have lots of other things I have to worry about. It is very unfortunate that it would be kinda hard for me to combine my major with diesels... . I'm so passionate about them.
I really hope that everyone can learn from not only this thread, but the Roundtable as a whole... . so far it has been invaluable to me!
Keep this thread goin'!!!!!
Matt - certifiable diesel fanatic
the 40 has been used in most of the twin setups I know of currently running around, with a 16 and spring setup on the waistgate to allow any sort of major pressure to open it, then going to an h2e with a 17 housing to take over. This is making 55psi in most Nowels red rocket. He as I feel the h2e is to small as the second stage, but its working.
as for using what you have, shoot you already have it so use it. I will prolly work better than either has as a singe.
most importantly have fun.
as for using what you have, shoot you already have it so use it. I will prolly work better than either has as a singe.
most importantly have fun.
Is the H2E bigger than the HX-series turbos?
Matt
Matt
its about the same size as a hx55 but has no waistgate stock.
That picture is worth a million words!
I'm a huge fan of that setup... I don't care if I have to move the battery!
So, is the bigger of the two an HX-55, or somthing else... . ?
The smaller one "looks" like a stock HX-35.....
I can't wait until I see/hear/drive/own a setup like that in person!!!!!
Matt
I'm a huge fan of that setup... I don't care if I have to move the battery!
So, is the bigger of the two an HX-55, or somthing else... . ?
The smaller one "looks" like a stock HX-35.....
I can't wait until I see/hear/drive/own a setup like that in person!!!!!
Matt
h2e and hx40
Nice set-up HVAC, like the LPG regulator in the back ground. What did you do with your shock tower? 
I've chosen to go the easy route and fabricate an under over combo, just finished machining out the cold side fitting today with the help of a coworker. I'll be able to clock and remove the set-up from the truck tonight and begin welding out the cold side piping on the bench. The last item to struggle with will be the oil returns, that will have to be done while on the truck, and me under it. Time to buy a lift for the shop. When I get the cold side piping done I'll take some pictures and post them.
I've chosen to go the easy route and fabricate an under over combo, just finished machining out the cold side fitting today with the help of a coworker. I'll be able to clock and remove the set-up from the truck tonight and begin welding out the cold side piping on the bench. The last item to struggle with will be the oil returns, that will have to be done while on the truck, and me under it. Time to buy a lift for the shop. When I get the cold side piping done I'll take some pictures and post them.- Status
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
Turbo Diesel Register
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
