Competition dual turbos

[Gizmo 007]

This may be in the wrong forum, but here it is anyway ...



I'm thinking of adding dual turbos to my setup. Here's the question.

I might be able to get another turbo that is slightly larger than the HX35. I already have a modified HX35 now. so could I team up the two turbos and gain anything? Or will I be causing more of a restriction than a gain?



I would like any and all comments, including pitfalls of using it as an everyday driver with duals (gotta sound cool ).



Thanks guys

 

[TxDieselKid]

The restriction should not matter in my thoughts, but who am I? Sounds like fun to me, think i might join in one day.

Andrew

 

[csutton7]

most twin setups use a pretty good size turbo as the #2 turbo---don't have all the answers, but this is what I've garnered---2 turbos of likewise performance may work, but may not work like you'd want-----chris

 

[DBR]

Gizmo, I built a twin set-up on my 97 for towing using a 14cm HX35 (Piers Special) and a 16cm HX 40 with, what I believe to be, good results. I can’t say from experience if to of the same size compressors would work or not, guess would be no. DBR

https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=25629

 

[MY6EATSV8'S]

basically you need the outside turbo to be able to supply the motor with enough air to supply the hp you desire. The inside turbo should be at least a hx35 but you need a big enough housing to flow the added exhaust and cant have to big of ex housing because thats the one getting things started. Same of the outside turbo. Usually the ouside is around a hx55 or slightly bigger turbo with a 18 or 22 housing.

 

[HVAC]

Twin Turbos

My first twin charger configuration-

#ad

 

[HVAC]

Goals

Gizmo,



What is your expectation for a twin charger setup?



Do you have a problem that you think twins might illeviate?

 

[Cummins Corvette]

Anyone know how well a Garret/airesearch tv 7511 would work with a ar ratio of . 75 on intake, and . 96 on the exhaust? I've got one sitting here, and would like to use it for something.

 

[Mark_Kendrick]

I'm wondering why you would need them. . like HVAC said.



Unless you are planning on getting into tractor pulls or well above the 400hp mark you can do well with a single turbo.



If you do a lot of towing and are gonna be upto 450 or so hp a B1 would be ideal.



After you get to stage 5 or bigger injectors and try to use it for a daily driver/tow vehicle it gets difficult to manage the EGTs.



This is near the 500hp mark ... . at least 475 or so.



Once the Stage 5 or bigger injectors go on you have a hard time getting a turbo to flow enough air to keep down EGTs and spool up with acceptable speed. This is when twins become necessary. not to say that a truck w/less hp could not benefit from twins but the expense would out weigh the gain.



to fit twins you'd have to remove or relocate the passenger side battery. Not a big deal but in comparison a B1 is half the price and almost a bolt-on operation.



HVAC and Piers are doing a lot with twins. Take their advice to heart. They have spent many thousands of dollars and hundresd of hours on MANY different turbos. Their experience is vast and valuable.



L8r,

MK

 

[Diesel Freak]

I have been doing a lot of thinking on this. No matter how good a single turbo system is, it is a compromise.



Twin turbos give you the benefit of having fast low end spool up, and high peak boost with relatively low drive pressures. I am thinking about using a PDR modified HX35 with a 14 cm housing with the wastgate set at 20 to 25 psi, and a non wastgated HX55. I just looked up the specs for the HX55, and the compressor outlet flange OD is 80mm. Do any of you know the nominal ID of the outlet? The HX55 weighs 50. 6 pounds, so I want to mount it as close to the engine as possible to limit the moment on the exhaust manifold. I am considering using an ATS manifold mounted with the outlet pointing up to give a little more room for the HX55 which would be mounted below the HX35. This should be relatively easy to fab up since I have access to a whole bunch of 304SS 40, 50, and 60mm nominal ID piping, elbows etc. with ISO, and NW flanges.



Anyone else have any ideas?

 

[Diesel Freak]

Originally posted by CAnderson

Anyone know how well a Garret/airesearch tv 7511 would work with a ar ratio of . 75 on intake, and . 96 on the exhaust? I've got one sitting here, and would like to use it for something.

See if you can find the minimum allowable oil pressure for the turbo..... most Holset turbos require a minimum of 30 psi within 4 seconds of startup

 

[Mark_Kendrick]

Originally posted by Diesel Freak

I have been doing a lot of thinking on this. No matter how good a single turbo system is, it is a compromise.



Twin turbos give you the benefit of having fast low end spool up, and high peak boost with relatively low drive pressures. I am thinking about using a PDR modified HX35 with a 14 cm housing with the wastgate set at 20 to 25 psi, and a non wastgated HX55. I just looked up the specs for the HX55, and the compressor outlet flange OD is 80mm. Do any of you know the nominal ID of the outlet? The HX55 weighs 50. 6 pounds, so I want to mount it as close to the engine as possible to limit the moment on the exhaust manifold. I am considering using an ATS manifold mounted with the outlet pointing up to give a little more room for the HX55 which would be mounted below the HX35. This should be relatively easy to fab up since I have access to a whole bunch of 304SS 40, 50, and 60mm nominal ID piping, elbows etc. with ISO, and NW flanges.



Anyone else have any ideas?

I don't know about this for sure but. . I think a highter wastegate setting on the HX35 will be in order.



when the exhaust goes through the first turbo you lose 3-400* of temperature. this reduction reduces the drive pressure for a large turbo that needs that energy to spin-up and continue to make boost.



I would think that wastegating to 25 psi would be too low. I think the gate would open before the second turbo spooled and boos would 'hang' so to say at 25 psi until the HX55 spooled . . if it ever spools properly.



Setting the waste gate to 50-55 psi seems more logical. The HX35 is going build alot more absolute boost compared to a single turbo yet will never make more than the equvalent of 44psi on a single. Because the air entering the turbo will be pressureized already the HX35 will easily make 50-???? psi of clean cool boost. Once the large turbo is spooled the 35 is not working hard at all to turn 20psi at the inlet into 60 or 80 psi at the outlet.



Boost is measured as an increase in pressue. . normal input is ~14psi so for 30psi of boost the absolute pressure would be 44psi. . a 200% increase. increase the inlet pressure to 30psi and the turbo can now make 90psi and still see the same load.



There are some factors that change the factors that I don't know about. the efficiency of the compressor seems to change with the increased density. . meaning you probably won't get the 90psi but i'd guess at 75-80 psi.



HVAC can give you a better real world asessment.

 

[Diesel Freak]

Mark, that is way too high. 50 psi with a PDR35 is way out of its efficiency range... . drive pressure would be over 60 PSI on that turbo alone. The idea of twins is to keep both turbos in the most efficient part of the compressor map to keep intake air as cool as possible. I am shooting for 50-60 psi total boost with great spool up at 1500 rpm.

 

[Sled Puller]

Keep in mind it IS possible to have TOO much air, and not enough fuel.

 

[Mark_Kendrick]

Originally posted by Diesel Freak

Mark, that is way too high. 50 psi with a PDR35 is way out of its efficiency range... . drive pressure would be over 60 PSI on that turbo alone. The idea of twins is to keep both turbos in the most efficient part of the compressor map to keep intake air as cool as possible. I am shooting for 50-60 psi total boost with great spool up at 1500 rpm.

50 psi is off the map if input pressure is 14psi. by the time an HX35 hits 40 psi the big turbo should be making some boost. An increase of only 5psi on the input moves the top of the map (35 or so psi is what's pratical ) to 35/14=2. 5 . . 2. 5*19= 48psi!!!



The boost will get better and better as the HX55 spools. the more the 55 adds the less the 35 multiplies keeping it constantly at the waste gate pressure or near it.



I know your HX55 will produce much more than 5 psi.



I think Gene is using an HX35 as part of his twins. . he has hit over 80psi!!!!!!!!!!(he blew a hose too)



Gene is right. . you'll be wanting more fuel. More fuel will make more boost possible.



if you exceed 60 psi of boost I'd O-ring the head. . this is the limit of reliabilty. if you hit 80psi you'll probably only do it once and have to replace the head gasket.

 

[Mark_Kendrick]

You only have stage 2 injectors. You'd be better off spending the money on a good single turbo.



I'd call Kurt Yardley. He has about the best single turbo for the under 475 crowd with the ability to tow.



If you want 500+ and streetabilty I'd go with twins... If not, it's not worth the trouble.

 

[DBR]

Mark;



My twin set-up works well for towing and doubt I have more than 325 hp to the rear wheels. I don’t know if there is a single turbo out there that is able to produce 30 psi at 1500 rpm; I want my power down low, real low.



I don’t waste-gate the primary turbo as it is my opinion that it is not necessary. I’ll be calling Piers soon to purchase a non-waste-gated 14cm housing to replace my waste-gated 14 that I have now. Anyone want to take a guess as to why you may not want to waste-gate the primary if it’s an “hx35” ? “Havac no fair answering the question”

 

[CUMINNTSTRKN]

dbr



i am going to wastegate the hx-35 on my twin setup to keep boost down around 65-70psi.



jim

 

[DBR]

Are you making any modifications to the hx35, or will it be stock?

 

[CUMINNTSTRKN]

dbr



are you asking me? i have mitchells twins. the hx-35 is bone stock. except i have to add a external wastegate and wastegate the exhaust after the big turbo. otherwise when the 35 wastegates it would drive the big turbo harder. the big turbo has a 5'"inlet and outlet it is bigger than a hx-55.

jim