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Compound turbos
by
Hoble
on 10 Nov, 2012 13:43
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I've been told my turbo choices won't make the power I am aiming for, 250whp would be ideal.
Current plans are to run a k03 and a large t3, 50 trim with a .48 ar.
I would like to boost pretty early and I'm only planning to rev to 6.
What do you think?
Lee
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#1
by
745 turbogreasel
on 10 Nov, 2012 14:40
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the AR48 T3 on my 2.5 seems to make more heat than boost at 6000RPM/1BAR.
I might have more than 110HP, if it's cold out anyway.
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#2
by
RabbitJockey
on 10 Nov, 2012 16:55
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the AR48 T3 on my 2.5 seems to make more heat than boost at 6000RPM/1BAR.
I might have more than 110HP, if it's cold out anyway.
depends on what compressor is attached, but a 2.5 at 6k at 1 bar would be flowing quite a bit more than a stock wheeled .48 can flow, couple that with a compressor that can flow that much either, and yes u will make lots of heat and back pressure
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#3
by
Hoble
on 10 Nov, 2012 17:19
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What would you recommend for turbos?
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#4
by
justiz00
on 10 Nov, 2012 18:17
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Sorry for the book and please don't chew my head off. It all seemed relevant when I convinced myself to type it.
I cant help you with a small turbo but the larger one based on my (garrett's formulas) math you for 250 fwhp you would need the following. 34lb/min of air and a 3.2 pressure ratio. Looking thru their compressor maps the only two that are not in the surge or spun into orbit are the GTX2863R 63mm 56 trim .60A/R at a 73% efficiency or the GTX3067R 67mm 55 trim .60A/R at a similar 73% efficiency. That is based on ~30lbs of boost, .38bsfc, 1psi intercooler drop and my 5xx ft above sea level. I could only guess the small turbo would spool the larger on which opens a wastegate in the manifold to bypass the exhaust housing of the small turbo to get the max unrestricted flow to the larger turbo. This keeps the larger turbo out of surge until the motor can accept the flow. I have heard the small turbo is correctly sized for the stock motor where the large turbo is sized for max power. Granted this is all for a sequential setup, not a true compound. Managing drive pressure while running all of the exhaust flow thru the small turbos exhaust housing seems incredibly inefficient.
Check out this link for sizing formulas and general turbo tech.
http://www.turbobygarrett.com/turbobygarrett/choosing_turboYes his piping looks busy, but check out the routing and his explaination of operation. Granted its a different application but another small displacement motor making a lot of power on more than one turbo. One of Aki's builds had a setup similar to this (pipe routing).
http://www.youtube.com/watch?v=y-Me6yWApzY&feature=related
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#5
by
Hoble
on 10 Nov, 2012 20:17
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Haha id rather someone type a book then give ***ty answers
I've actually seen that video before when I was researching the setup. My original turbo choices where made when the build was tight budget. Now it's not so much... And as for bypassing the turbo I have a 44mm tial. Actually have two. For first and second turbo
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#6
by
RabbitJockey
on 10 Nov, 2012 20:34
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Sorry for the book and please don't chew my head off. It all seemed relevant when I convinced myself to type it.
I cant help you with a small turbo but the larger one based on my (garrett's formulas) math you for 250 fwhp you would need the following. 34lb/min of air and a 3.2 pressure ratio. Looking thru their compressor maps the only two that are not in the surge or spun into orbit are the GTX2863R 63mm 56 trim .60A/R at a 73% efficiency or the GTX3067R 67mm 55 trim .60A/R at a similar 73% efficiency. That is based on ~30lbs of boost, .38bsfc, 1psi intercooler drop and my 5xx ft above sea level. I could only guess the small turbo would spool the larger on which opens a wastegate in the manifold to bypass the exhaust housing of the small turbo to get the max unrestricted flow to the larger turbo. This keeps the larger turbo out of surge until the motor can accept the flow. I have heard the small turbo is correctly sized for the stock motor where the large turbo is sized for max power. Granted this is all for a sequential setup, not a true compound. Managing drive pressure while running all of the exhaust flow thru the small turbos exhaust housing seems incredibly inefficient.
Check out this link for sizing formulas and general turbo tech.
http://www.turbobygarrett.com/turbobygarrett/choosing_turbo
Yes his piping looks busy, but check out the routing and his explaination of operation. Granted its a different application but another small displacement motor making a lot of power on more than one turbo. One of Aki's builds had a setup similar to this (pipe routing).
http://www.youtube.com/watch?v=y-Me6yWApzY&feature=related
the small turbo compresses more so the larger turbo might only need to push 15psi into the small turbo which could then turn that to 30 psi so the surge line is not much of an issue. there are a ton of turbos that will work, just depends on cost and what u really want.
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#7
by
Hoble
on 10 Nov, 2012 21:16
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How about some examples? I don't want to spend like 5 grand on turbos but I am willing to pay for quality gear that will last and meet/ exceed my needs.
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#8
by
RabbitJockey
on 11 Nov, 2012 07:41
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I can only really give suggestions I've never built one and very few people to be able to say what works, but on the cheap or used end for the small turbo a t25 off a Saab or volvo or a smaller Mitsubishi turbo off a Volvo or dsm would be ok and for the larger turbo a 60 trim .63 t3 from a ford 2.3 would be alright or a holset hx30. When it comes to new turbos there are so many different brands that each have a *** ton of options it's really hard to just suggest which ones the only thing I would say to look for is for a small turbo shoot for one that is capable of about 200hp for the large one shoot for one that's good for 300-400hp and I think going to the larger exhaust side is probably best because compound are going to spool faster anyway and a larger exhaust housing makes for a more efficient turbo
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#9
by
Hoble
on 11 Nov, 2012 14:57
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I'm not looking for cheap but I'm not looking spend a fortune ether.
Thank you for that info. That has set me on a whole new research path.
I do have another question though. What is lb/min or kg/min? Is that equivalent to psi but over a period of time? Similar to kmph to km or mph to miles?
I am new to the turbo math and mapping stuff. No idea what half of what I'm looking at is.
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#10
by
RabbitJockey
on 11 Nov, 2012 15:55
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I'm not looking for cheap but I'm not looking spend a fortune ether.
Thank you for that info. That has set me on a whole new research path.
I do have another question though. What is lb/min or kg/min? Is that equivalent to psi but over a period of time? Similar to kmph to km or mph to miles?
I am new to the turbo math and mapping stuff. No idea what half of what I'm looking at is.
Psi and lbs/min kg/min are totally different measurements. Psi is a measure of pressure the others are a measure of mass flow. U can use formulas and do it yourself or u can use online turbo calculators to figure out the amount of psi u need to attain a certain mass flow to attain a certain hp goal
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#11
by
RabbitJockey
on 11 Nov, 2012 15:56
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Garrett's website has good write up on how to do it all
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#12
by
justiz00
on 12 Nov, 2012 09:00
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When I ran the numbers I figured a 22:1 A/F ratio so I would not be smokey under boost. For an 18:1 A/F you could use a smaller turbo @ 28.5 lb/min at a 2.87 Pressure ratio, this would probably open up a lot more options.
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#13
by
Hoble
on 12 Nov, 2012 10:12
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#14
by
RabbitJockey
on 12 Nov, 2012 14:06
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Those are good choices but I think I'd go a bit smaller like a gt2056 for the small one and a gt2860 for the big but everything is a guestimation
