Looking for advice on compound turbos
- Thread starter co04cobra
- Start date
PowerstrokeJunkie
Active member
I have a wastegated t4 mount with s366, and just so happen to have a new s480 for sale.. Just sayin....
Yea Ive been pushing for awhile. If it blows Ive got a few spares and a built motor laying around here somewhere. LOL
Well I wasnt planning on changing everything, but PM me the specs and a price.
First off I think some might be confused what size your turbo really is as its not the aftermarket ones that are listed on Garrett's site. The gt45 family designation can give the impression of a turbo with larger wheels than what it actually has.
While its built on a gt45 frame its much closer to a GT4094 but with a smaller inducer on the comp wheel 62/94 instead of a 67/94 of a 4094 and the turbine wheels being basically the same @ 87/77. You compare this to a 38r and you can see it has actually a smaller inducer on the comp but a larger exducer. As its the inducer of the compressor wheel that controls actual incoming air flow rate "what takes the bite" you can compare that to other turbos that have a 62-63mm inducer as far as cfm or lb/min per revolution. As the wheel has the OD of a gt4294 comp wheel you can compare trims of the two The GT4594 63/94 comp wheel has a trim of 45 compared to the gt4294 70/94 trim of 56 so a rather sizable difference of air flow for wheels from the same family.
Minus the exact mass from the larger exducer it size in ratio to the inducer should help it spool fast and have the surge line moved way over so that it would never be an issue. So on the compressor side its not moving more air "per rev" than a 38r.
Where the GT4594 does have real benefit for a 7.3 is breathing on the exhaust side which should allow for a higher boost to drive pressure ratio. Its the same as that of the gt4094 @ 77/88 with a 78 trim. So it moves a good deal more air than the 38r @ 68/77 but a bit less than a gt4294 with its 82/90 turbine wheel. Also with the larger turbine T6 @ 1.33 housing added to this.
So to make the easiest comparison it's a gt4088 in compressor flow rate performance and a gt4094 in turbine wheel performance. IMO it actually makes a fairly nice single street turbo for the 7.3 from the specs and I think co04cobra agrees with this.
Below is all just my opinion and I have not personally run a compound setup to please keep that in mind:
The issue though is trying to use it as the atmosphere in a compound setup. Personally I do not see it working well. While it does have a larger turbine side than some of smaller single turbos its still not even as large as a gt42. IMO that being the smallest atmosphere I could ever see on a 7.3 and I personally would not choose something that small.
I do not see it as a good idea to use it as a compound turbo in either position IMO. Its setup to be a good single turbo. Fast spool up and bottom end boost is the goal of a HP turbo and while the comp wheel is not that bad the turbine is too large in ratio not to mention the huge housing. This would be the opposite of what would be ideal for fast spool up and boost building.
For the atmosphere turbo its just the opposite. You have a too small comp wheel and larger but still smaller than even a smallish atmosphere turbo turbine should have. The housing ratio is more inline though. Could it work as a HP turbo yes. Not ideal though. Could it work as a atmosphere turbo IMO its even worse of a choice.
IMO if you are going to go to all the trouble of piping, mounts, oil lines, waste gate for both stages its worth it to get the turbos properly sized. Best case for using it IMO would be to make it the HP turbo. Then pick up a pull off the equivalent to a GT47 from another OTR engines and use that. That would at least give you a more balanced setup. It would not add as much to the bottom end as a turbo with a proper smaller turbine setup but you would get a good boost from the middle to upper with it in use with the gt47 or something similar.
While its built on a gt45 frame its much closer to a GT4094 but with a smaller inducer on the comp wheel 62/94 instead of a 67/94 of a 4094 and the turbine wheels being basically the same @ 87/77. You compare this to a 38r and you can see it has actually a smaller inducer on the comp but a larger exducer. As its the inducer of the compressor wheel that controls actual incoming air flow rate "what takes the bite" you can compare that to other turbos that have a 62-63mm inducer as far as cfm or lb/min per revolution. As the wheel has the OD of a gt4294 comp wheel you can compare trims of the two The GT4594 63/94 comp wheel has a trim of 45 compared to the gt4294 70/94 trim of 56 so a rather sizable difference of air flow for wheels from the same family.
Minus the exact mass from the larger exducer it size in ratio to the inducer should help it spool fast and have the surge line moved way over so that it would never be an issue. So on the compressor side its not moving more air "per rev" than a 38r.
Where the GT4594 does have real benefit for a 7.3 is breathing on the exhaust side which should allow for a higher boost to drive pressure ratio. Its the same as that of the gt4094 @ 77/88 with a 78 trim. So it moves a good deal more air than the 38r @ 68/77 but a bit less than a gt4294 with its 82/90 turbine wheel. Also with the larger turbine T6 @ 1.33 housing added to this.
So to make the easiest comparison it's a gt4088 in compressor flow rate performance and a gt4094 in turbine wheel performance. IMO it actually makes a fairly nice single street turbo for the 7.3 from the specs and I think co04cobra agrees with this.
Below is all just my opinion and I have not personally run a compound setup to please keep that in mind:
The issue though is trying to use it as the atmosphere in a compound setup. Personally I do not see it working well. While it does have a larger turbine side than some of smaller single turbos its still not even as large as a gt42. IMO that being the smallest atmosphere I could ever see on a 7.3 and I personally would not choose something that small.
I do not see it as a good idea to use it as a compound turbo in either position IMO. Its setup to be a good single turbo. Fast spool up and bottom end boost is the goal of a HP turbo and while the comp wheel is not that bad the turbine is too large in ratio not to mention the huge housing. This would be the opposite of what would be ideal for fast spool up and boost building.
For the atmosphere turbo its just the opposite. You have a too small comp wheel and larger but still smaller than even a smallish atmosphere turbo turbine should have. The housing ratio is more inline though. Could it work as a HP turbo yes. Not ideal though. Could it work as a atmosphere turbo IMO its even worse of a choice.
IMO if you are going to go to all the trouble of piping, mounts, oil lines, waste gate for both stages its worth it to get the turbos properly sized. Best case for using it IMO would be to make it the HP turbo. Then pick up a pull off the equivalent to a GT47 from another OTR engines and use that. That would at least give you a more balanced setup. It would not add as much to the bottom end as a turbo with a proper smaller turbine setup but you would get a good boost from the middle to upper with it in use with the gt47 or something similar.
exactly! It's doesn't move the poundage.
silverpsd_06
New member
So tarm an actual housing off of a 4094 would fit on his turbo? I know the options for that turbine wheel for a 4094 go all the way down to a .85 a/r t4
Different family of turbos. Its a GT45 frame.
What I was referring to was the wheel sizes and comparing actual flow. You see GT45 and we think of the wheels we see for the aftermarket 45s. But in this case its a stock turbo for a OTR so smaller wheels on the big frame.
What I was referring to was the wheel sizes and comparing actual flow. You see GT45 and we think of the wheels we see for the aftermarket 45s. But in this case its a stock turbo for a OTR so smaller wheels on the big frame.
PowerstrokeJunkie
Active member
Marty
New member
Going to a 38R style or 66mm turbo would not be a step back. With a turbo in front of the other.... the 66mm will spool like a 71 or a little larger. Therefore smaller is better, as long as you can gate around it once drive comes up and get the excess energy to the low pressure turbine.
Ideally I'd like to do any 62-66mm turbo, keep exhaust wheel and housing small with a 60mm+ gate. Feeding a 105 or better. Big exhaust wheel, big exhaust housing. 44mm gate. That would be for power.... make the low pressure smaller for mostly dd/towing... IE: 95mm or so. Same exhaust principles though.
Just my $.02....
Ideally I'd like to do any 62-66mm turbo, keep exhaust wheel and housing small with a 60mm+ gate. Feeding a 105 or better. Big exhaust wheel, big exhaust housing. 44mm gate. That would be for power.... make the low pressure smaller for mostly dd/towing... IE: 95mm or so. Same exhaust principles though.
Just my $.02....
Marty any examples of turbos like you are saying. 38r feeding a S475?
OK let me change directions for just a second. My plan was to try and compound this setup for maybe around 3k, and in somewhat of timely fashion. If I was going to switch everything. I would end up changing injectors and putting in my built motor.
There really is no need for me to do that when the truck runs and drives completely fine.
Would it be possible to send this turbo off to bell turbo and have billet wheels installed? Possibly add headers and tweak the tuning to try and help spool. It may be easier in the long run.
If I change EVERYTHING I know how it goes. 2K will turn into 12K. Ive been thinking before I put that much in this truck I would try a 6.4.
OK let me change directions for just a second. My plan was to try and compound this setup for maybe around 3k, and in somewhat of timely fashion. If I was going to switch everything. I would end up changing injectors and putting in my built motor.
There really is no need for me to do that when the truck runs and drives completely fine.
Would it be possible to send this turbo off to bell turbo and have billet wheels installed? Possibly add headers and tweak the tuning to try and help spool. It may be easier in the long run.
If I change EVERYTHING I know how it goes. 2K will turn into 12K. Ive been thinking before I put that much in this truck I would try a 6.4.
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Marty
New member
Nah. Didn't say anything about a 475 lol.
38r and 483 would make a good 550 and be responsive. Change that second charger to 595/105 etc.... make another 200+ HP...... that 45 leaves you limited. Too small for LP. Too big for HP. If you make it your hp you will not have nearly the spoolup you do now....
38r and 483 would make a good 550 and be responsive. Change that second charger to 595/105 etc.... make another 200+ HP...... that 45 leaves you limited. Too small for LP. Too big for HP. If you make it your hp you will not have nearly the spoolup you do now....
38R feed by a 5518 or 4718. I would personally go with the 5518 but the 38r/4718 is a proven combo. The difference between the two is the 5518 has the same comp but a larger and much more efficient turbine wheel. The 4718 comp wheel has IMO a great map for a atmosphere turbo. But the turbine is a bit weak hence the 5518 which IMO gets you the best of both.
silverpsd_06
New member
I wouldn't do headers just to try to help spool at 1k your pretty close to just buying a 38r.. Sell the 45 and I even think there was a gt55 on craigslist around here for 500 or so 92mm with a 1.32 on it.. Once you get a good set of compounds on it you will love the truck trust me a single has no advantages unless it is strictly competition use.
Tarm your saying this http://www.workturbochargers.com/pr...age=flypage.tpl&product_id=103&category_id=50 with a 38r?
Im def looking for more then 550hp going back to Martys setup with the 38 and 483.
What could the 38 and 5518 support? Still streetable? Fast spool?
Im def looking for more then 550hp going back to Martys setup with the 38 and 483.
What could the 38 and 5518 support? Still streetable? Fast spool?
Marty
New member
Anything with a HP that is 66mm or smaller will be streetable. The main reason the 38r is more responsive then an s4 series 66 is because it has a much smaller shaft, smaller exhaust housing and a much smaller turbine. The bb probably helps too but I suspect the reasons I listed before are most likely the main ones.
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Marty
New member
Those reasons also limit its horse power as a single. Ie: on average the s466 will make at least 75 mote horsepower, all other things constant.
silverpsd_06
New member
http://www.youtube.com/watch?v=zlptKJT8YzE
This is Charles' setup originally 400/400's 38r and gt 4718 I think he towed with it almost every day and had put down somewhere in the neighborhood of 650ish
This is Charles' setup originally 400/400's 38r and gt 4718 I think he towed with it almost every day and had put down somewhere in the neighborhood of 650ish
MadDiesel73
New member
On a budget u cant beat at s366 ($500-700) and a 4718 ($1500) if u want faster spool swap the 366 for a 363 ($900) if you want a cheaper lp its hard to beat forced inductions gt88/gt91 or their s488 ($1250)
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