Thermodynamics of Twin Turbos?
09-09-2010, 04:42 PM
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Thermodynamics of Twin Turbos? So Im trying to pick out some twins that arent too laggy and dont choke up. Heres my conundrum:
Currently I have a T70 with a .96 A/R. If you have 2 .68 turbos, would that equal 1.36 or are the dynamics entirely different?
I hope that makes sense lol
Currently I have a T70 with a .96 A/R. If you have 2 .68 turbos, would that equal 1.36 or are the dynamics entirely different?
I hope that makes sense lol
09-09-2010, 05:43 PM
#2
A/R numbers are somewhat misleading in that two turbos with the same A/R exh housing can move vastly different amounts of exh gases due to blade pitch, count and turbine diameter. It seems that the A/R is only really good for sizing them against the same model turbo or to give a general idea of what you are dealing with. Atleast this is how I understand it.
Would love to get some clarification.
09-09-2010, 05:57 PM
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twin turbos usually make very little more hp and tq than a single due to the fact that u r cutting the exhast air in half...which wont allow the turbo to spool as fast...but it makes a little more porwer because of the lack of back pressure....u would make a toon more power with one 108 mm turbo than u would with twin 60 mm... i guess it really depends on what size the turbo is...but think of force= mass x acceleration...the mass of the "air" will aaccelerate the turbine and create ur force...so the more air the more power!!
09-10-2010, 06:04 AM
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twin turbos usually make very little more hp and tq than a single due to the fact that u r cutting the exhast air in half...which wont allow the turbo to spool as fast...but it makes a little more porwer because of the lack of back pressure....u would make a toon more power with one 108 mm turbo than u would with twin 60 mm... i guess it really depends on what size the turbo is...but think of force= mass x acceleration...the mass of the "air" will aaccelerate the turbine and create ur force...so the more air the more power!!
spooling a 108mm turbo at 2500rpm with my motor is not going to happen, no matter what exhaust housing you get it with.
it is really not fair to compare a single 108 to twin 60's as far as top end hp goes, twin 76's is a much better comparison
09-10-2010, 07:58 AM
#6
The dynamics are different. You can't just add up the A/R. A/R is just a ratio, so flows can be drastically different depending on the overall size of the turbo.
My advice would be to look at what people are running with twins. You can crunch all of the numbers to size the exhaust housing appropriately, but you'll be just as far ahead by snooping around other people's setups.
Also, spool time has just as much to do with the setup as it does with what turbo you have picked. You can get an otherwise laggy turbo setup to spool rather quickly by running the proper type of boost controller (ball-n-spring), retarding timing in the tune, changing downpipe sizing (pinch it a bit), and wrapping the exhaust.
So.....I would pick turbos to meet your HP goal, then start fidgeting with it to reduce lag. Most twin setups (up to 800-900 HP or so) spool relatively quickly anyways.
My advice would be to look at what people are running with twins. You can crunch all of the numbers to size the exhaust housing appropriately, but you'll be just as far ahead by snooping around other people's setups.
Also, spool time has just as much to do with the setup as it does with what turbo you have picked. You can get an otherwise laggy turbo setup to spool rather quickly by running the proper type of boost controller (ball-n-spring), retarding timing in the tune, changing downpipe sizing (pinch it a bit), and wrapping the exhaust.
So.....I would pick turbos to meet your HP goal, then start fidgeting with it to reduce lag. Most twin setups (up to 800-900 HP or so) spool relatively quickly anyways.
09-10-2010, 09:39 AM
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You have to go to the turbine map for each turbo to get a close quess.
Look at the same turbo with different AR's here. 63AR = 22.5lb/min flow......1.06AR = 32lb/min flow....roughly a 42% increase in flow.
You don't want to match the twin ar flow to a single T70 turbine flow to get the same spool-up....they'll choke...if a single T70 96ar T4 flowed 28lb/min you don't want twins that flow 14lb/min each.
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09-10-2010, 03:34 PM
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Now it's down to budget and goals and trans.
Auto or stick?
I've used twin 54's, 61's and 76's.
If I wanted a pure street car on pumpgas that spooled great and would work well with stick or auto.....and I was starting over from scratch.....I'd go with GT3582R's (61mm) with T3 turbine and 0.8x AR. Or a clone from Precision, etc.
If I already had a T70 I would use it due to $$.
If I already had 61's with o.68AR turbines....I would use them due to $$...68 vs 81 on a street car is not a big deal....
Auto or stick?
I've used twin 54's, 61's and 76's.
If I wanted a pure street car on pumpgas that spooled great and would work well with stick or auto.....and I was starting over from scratch.....I'd go with GT3582R's (61mm) with T3 turbine and 0.8x AR. Or a clone from Precision, etc.
If I already had a T70 I would use it due to $$.
If I already had 61's with o.68AR turbines....I would use them due to $$...68 vs 81 on a street car is not a big deal....
09-10-2010, 04:47 PM
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M6. Id like 600whp and Im on a budget, not a tight one but I dont want to spend 1k per turbo. Looking at the Masterpower T60 w/t4 flange here are the specs:
810027 T-60-P Trim Turbine:60.5mm/84mm .70a/r Compressor:74mm/76mm .68a/r
810027 T-60-P Trim Turbine:60.5mm/84mm .70a/r Compressor:74mm/76mm .68a/r
09-10-2010, 06:03 PM
#15
Now it's down to budget and goals and trans.
Auto or stick?
I've used twin 54's, 61's and 76's.
If I wanted a pure street car on pumpgas that spooled great and would work well with stick or auto.....and I was starting over from scratch.....I'd go with GT3582R's (61mm) with T3 turbine and 0.8x AR. Or a clone from Precision, etc.
If I already had a T70 I would use it due to $$.
If I already had 61's with o.68AR turbines....I would use them due to $$...68 vs 81 on a street car is not a big deal....
Auto or stick?
I've used twin 54's, 61's and 76's.
If I wanted a pure street car on pumpgas that spooled great and would work well with stick or auto.....and I was starting over from scratch.....I'd go with GT3582R's (61mm) with T3 turbine and 0.8x AR. Or a clone from Precision, etc.
If I already had a T70 I would use it due to $$.
If I already had 61's with o.68AR turbines....I would use them due to $$...68 vs 81 on a street car is not a big deal....
I'm going for twin GT3582Rs with the .81 exhaust housings on my forged 347 build so I'm curious if I'm going in the wrong direction.
It will be basically a stock LS6 with forged rods, -8.6cc pistons, springs, pushrods, and studs.
I'm not looking for anything ridiculous, just decent response and around 750-800 to the wheels.
09-10-2010, 06:20 PM
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Are you talking twin GT3582Rs or a single?
I'm going for twin GT3582Rs with the .81 exhaust housings on my forged 347 build so I'm curious if I'm going in the wrong direction.
It will be basically a stock LS6 with forged rods, -8.6cc pistons, springs, pushrods, and studs.
I'm not looking for anything ridiculous, just decent response and around 750-800 to the wheels.
I'm going for twin GT3582Rs with the .81 exhaust housings on my forged 347 build so I'm curious if I'm going in the wrong direction.
It will be basically a stock LS6 with forged rods, -8.6cc pistons, springs, pushrods, and studs.
I'm not looking for anything ridiculous, just decent response and around 750-800 to the wheels.
That's my favorite "all around" turbo in a twin for stock to 428 cubes. Stock cubes plus 81ar turbine has potential of +1000rwhp pushed. 428 cubes plus 1.06ar = +1000rwhp pushed......great turbo.
09-10-2010, 11:00 PM
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I agree on 3582R's.
They are just expensive.
2 GT61's from FI are less than one 3582R.
I didn't suggest 61's due to stock motor w/stick and low hp goal. I'd personally go with 61's if it didn't require twice the work the single 80mm will to make fit. S10's are as bad as Fbody but with less room after you get rid of most everything.
2 61= 1 88mm = fast by most anyone
They are just expensive.
2 GT61's from FI are less than one 3582R.
I didn't suggest 61's due to stock motor w/stick and low hp goal. I'd personally go with 61's if it didn't require twice the work the single 80mm will to make fit. S10's are as bad as Fbody but with less room after you get rid of most everything.
2 61= 1 88mm = fast by most anyone
09-11-2010, 12:36 PM
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Rick
