The perfect twin turbo system RB26

[ATpossible]

Engine: RB26DETTDisplacement: 2.6LHP Goal: 500whp or 588-600hp(flywheel) assuming 15% lossTurbo setup: Twins

got my info from garrett turbos and i have a question about the difference when going twin turbo.

basically my question is in regards to psi and air flow required when going this route.

do i need to set a boost controller to 28.8psi? Where each turbo does half the work or do I have it set to 14.4 where each turbo will combine to make my overall psi of 28.8?

can the engine handle 28psi in stock form? am i even calculating it right cuz 28psi for only 500whp seems like a lot.

i can show my calculations for anyone wondering where i got my #'s.

oh and going off the compressor maps it seems like the gt2871r is the way to go, but i've never seen anyone suggest that big of a turbo for twins in my goal range. i only remember turbos like gt2860r or gt2530r if my memory serves me right.

i fear something is off ...help please

[BoostFab]

pretty much. you can do either sequential or parallel setup. stock setup are parallel.

http://en.wikipedia.org/wiki/Twin-turbo

[Coolwhip]

GT2530'sGT2860-5GT2860-7

will all get you there. GT2530's being the more popular of them all it seems.

[ATpossible]

pretty much. you can do either sequential or parallel setup. stock setup are parallel.

http://en.wikipedia.org/wiki/Twin-turbo

i know they are stock parallel...i've never heard of anyone doing sequential other than the supra...seems too difficult. however that isn't the question.

GT2530'sGT2860-5GT2860-7

will all get you there. GT2530's being the more popular of them all it seems.

yes but im looking for the best one for the job and this is what i got...using their formulas. i guess i would like a reason or graph as to why its perfect for my setup and also has potential to do a lil more if i choose down the road. here is my graph, like i said idk where i messed up to get bigger than gt2860r which is what i thought was needed.

[StricNyne]

fd rx7 is sequential but u see that birds nest of vacuum lines lol

[BoostFab]

you could go with larger turbo to achieve that power at a lower boost

[gawdzilla]

may i suggest following what has been tried and true instead of your internet bench racing research. staring at the compressor map isn't telling you much without knowing how the motor flows. pretty sure there are thousands of fanboys who have thoroughly dreamt about the godliest turbo setup to no end.

[StricNyne]

imma prolly just get r34 n1 and call it a day its good for 600ish to crank

[HxC_Nismo]

GT2530 FTW!

[ItzGenX]

I am personally going to go with a pair of GT2860R -5's (little better then N1 turbos in terms of flow). 600whp is almost pushing it, but 500whp is in it's happy range. They are almost the same as HKS 2530's but cheaper (1.8K vs 3k a pair). Also, bolt-on afair can give me less headaches.

As for your boost question, do you even know how boost control works?! The air will reach 14psi inside the intake tract (most accurate if measured at the intake manifold). At 14psi, each turbo is pushing 14psi. The boost controller will feed this 14psi via valve or solenoid to both wastegate actuators where they both open and regulate boost. 14psi of air plus 14psi of air into the same chamber equals 14psi of air! The only difference is the turbos need to work less (lower shaft speed) to reach 14psi because it has a partner that spools at about the same time, causing them to REACH that set pressure of 14psi sooner (double work, not double pressure). They both act as one (so just pretend you have a single turbo twice as large; example 25lb/min x 2 = 50lb/min big turbo).

[ATpossible]

fd rx7 is sequential but u see that birds nest of vacuum lines lol

really i've read about them i guess i forgot

you could go with larger turbo to achieve that power at a lower boost

ya but i really want twins although no real justification just wanna leave it that way

may i suggest following what has been tried and true instead of your internet bench racing research. staring at the compressor map isn't telling you much without knowing how the motor flows. pretty sure there are thousands of fanboys who have thoroughly dreamt about the godliest turbo setup to no end.

no the the compressor map helps decide the best turbo for what you want. if you are so smart you would know that. sorry for trying to get the best POSSIBLE setup and for reading almost 6 hours straight before asking a question.

imma prolly just get r34 n1 and call it a day its good for 600ish to crank

thought about it but i decided against it

GT2530 FTW!

prolly since i've seen it suggested a lot but the money thing is what is keeping from not continuing to see other options

I am personally going to go with a pair of GT2860R -5's (little better then N1 turbos in terms of flow). 600whp is almost pushing it, but 500whp is in it's happy range. They are almost the same as HKS 2530's but cheaper (1.8K vs 3k a pair). Also, bolt-on afair can give me less headaches.

As for your boost question, do you even know how boost control works?! The air will reach 14psi inside the intake tract (most accurate if measured at the intake manifold). At 14psi, each turbo is pushing 14psi. The boost controller will feed this 14psi via valve or solenoid to both wastegate actuators where they both open and regulate boost. 14psi of air plus 14psi of air into the same chamber equals 14psi of air! The only difference is the turbos need to work less (lower shaft speed) to reach 14psi because it has a partner that spools at about the same time, causing them to REACH that set pressure of 14psi sooner (double work, not double pressure). They both act as one (so just pretend you have a single turbo twice as large; example 25lb/min x 2 = 50lb/min big turbo).

like the suggestion which was prolly the first choice just from seeing other people's but still wanted to research more. i honestly was getting a headache trying to understand the manifold pressure and each turbo psi. thanks for explaining it...now i know although it doesnt make sense to me hope you are right...and if you are

[Bluefire]

Go with tried and true setups. To properly utilize a compressor map, you need to know too many specific variables. Your pretty much guessing on everything, which means your results will be pretty skewed. Even your target boost level is going to be wrong because you'll have some amount of pressure drop through you intercooler and piping setup.

-Bluefire

[StricNyne]

i noticed no one mentioned twin t51z is it cuz of price ?

[ItzGenX]

i noticed no one mentioned twin t51z is it cuz of price ?

Price is probably a huge factor in it. Most of these high name japanese brands can be cross referenced to Garrett half it's price over here in the US and just as good. I personally don't feel the need to buy the most expensive of two turbos if they are exactly the same except one is just rebadged and price retagged. It isn't because I am Garrett biased (I like a lot of IHI turbos too), but to simply put it, most of these other turbos ARE Garrett cores with a 50% mark up. Some specs I do know Garrett do not offer, which can easily be found with custom made wheels mounted on Garrett cores via other US vendors that won't rape you sideways, such as, Full-Race, Turbonetics, ATP, Precision, etc. It is not like we are buying knock off turbos. The funny part is Garrett turbos over in Japan are marked up in price due to importing fees they have to pay. Those guys think they are great but pricy, so end up going with a discounted Japanese name like Blitz,HKS,Greddy,Apexi etc (wierd eh?). In the end, yes, many do decide on price. If I wanted to just throw away money, I'd go play the lottery.

[StricNyne]

hahah i think i am going to go the dash 5 i read that it does flow better than n1, and for similar price, i found brand new n1 for like 1700 shipped for pair if i can find -5 for similar or maybe a lil more i would get em

[ItzGenX]

hahah i think i am going to go the dash 5 i read that it does flow better than n1, and for similar price, i found brand new n1 for like 1700 shipped for pair if i can find -5 for similar or maybe a lil more i would get em

Yea they do flow a little more then the N1 (-7) turbos. Usually you can find a pair of -5 or -7 for between 1650-2000 shipped. Average going price is around 1800 shipped. I mean you can't beat that with a 10 foot stick. You get twin turbo upgrades with dual ball bearing, GT wheel technology, completely bolt on for the price of a big single GT42. I have put myself into it plenty of times about going single or upgrading the twins. If going single, it would actually end up costing more with a quality manifold, grade A turbo, wastegate, lines, and custom plumbing. The main reason people used to go to singles was cause upgrading the twins to something nice would cost an arm and a leg. Now the tides have turned and *** backwards!

[HxC_Nismo]

i got my gt2530 twins with hks dumps for only $1800 and they only had 5000kmh on em thats why i bought em

[TSL]

no the the compressor map helps decide the best turbo for what you want. if you are so smart you would know that. sorry for trying to get the best POSSIBLE setup and for reading almost 6 hours straight before asking a question.

And if you were smart you would recognize good advice when you see it.

Ironic that you question the intelligence of someone else after you come here and ask one of the most stupid boost related questions i have ever read. Given that you clearly have no idea of how air flow and boost pressure works i would suggest you stop wasting your time staring blankly at compressor maps and listen to the good advice you have been given and stick with a proven combination.

[ATpossible]

Go with tried and true setups. To properly utilize a compressor map, you need to know too many specific variables. Your pretty much guessing on everything, which means your results will be pretty skewed. Even your target boost level is going to be wrong because you'll have some amount of pressure drop through you intercooler and piping setup.

-Bluefire

thanks i got the info of garrett's website although i do no it wont be right on it can get you close if done right

i noticed no one mentioned twin t51z is it cuz of price ?

you are right

Price is probably a huge factor in it. Most of these high name japanese brands can be cross referenced to Garrett half it's price over here in the US and just as good. I personally don't feel the need to buy the most expensive of two turbos if they are exactly the same except one is just rebadged and price retagged. It isn't because I am Garrett biased (I like a lot of IHI turbos too), but to simply put it, most of these other turbos ARE Garrett cores with a 50% mark up. Some specs I do know Garrett do not offer, which can easily be found with custom made wheels mounted on Garrett cores via other US vendors that won't rape you sideways, such as, Full-Race, Turbonetics, ATP, Precision, etc. It is not like we are buying knock off turbos. The funny part is Garrett turbos over in Japan are marked up in price due to importing fees they have to pay. Those guys think they are great but pricy, so end up going with a discounted Japanese name like Blitz,HKS,Greddy,Apexi etc (wierd eh?). In the end, yes, many do decide on price. If I wanted to just throw away money, I'd go play the lottery.

i agree 100%

hahah i think i am going to go the dash 5 i read that it does flow better than n1, and for similar price, i found brand new n1 for like 1700 shipped for pair if i can find -5 for similar or maybe a lil more i would get em

where did you buy them?

Yea they do flow a little more then the N1 (-7) turbos. Usually you can find a pair of -5 or -7 for between 1650-2000 shipped. Average going price is around 1800 shipped. I mean you can't beat that with a 10 foot stick. You get twin turbo upgrades with dual ball bearing, GT wheel technology, completely bolt on for the price of a big single GT42. I have put myself into it plenty of times about going single or upgrading the twins. If going single, it would actually end up costing more with a quality manifold, grade A turbo, wastegate, lines, and custom plumbing. The main reason people used to go to singles was cause upgrading the twins to something nice would cost an arm and a leg. Now the tides have turned and *** backwards!

the extra stuff you speak of is the main reason im keeping the twin setup

i got my gt2530 twins with hks dumps for only $1800 and they only had 5000kmh on em thats why i bought em

the closest i've seen was 2200 i believe for used. i just dont know how i feel about used turbos. how did look when you got them? and where did you get them from? thanks

And if you were smart you would recognize good advice when you see it.

Ironic that you question the intelligence of someone else after you come here and ask one of the most stupid boost related questions i have ever read. Given that you clearly have no idea of how air flow and boost pressure works i would suggest you stop wasting your time staring blankly at compressor maps and listen to the good advice you have been given and stick with a proven combination.

did you realize he didnt give any real advice?

now since you make it sound that you were born with the knowledge of boost how about explain instead of saying its a dumb question or give me a link to read more about it myself. you are just as much of a *** as he is and both equally stupid. i dont know boost/air flow and you do so that means you are now you are the smartest? lol dont bother with the thread if you aren't going to contribute

[TSL]

did you realize he didnt give any real advice?

He did give advice, excellent advice. Look and read...

may i suggest following what has been tried and true instead of your internet bench racing research.

lol dont bother with the thread if you aren't going to contribute

Don't bother with life if you can't handle harsh reality.
Modified by TSL at 2:43 AM 8/5/2008

[WhatsADSM]

Reading compressor maps is a great way to start researching for a turbo. However gawdzilla's point is 100% true. Looking at real life results is equally as important

Now with that said your compressor map math is definately off if you are coming up with 500whp out of 2871s at ~29psi, so I wouldn't trust those results anyways.

[ATpossible]

He did give advice, excellent advice. Look and read...

Don't bother with life if you can't handle harsh reality.

Modified by TSL at 2:43 AM 8/5/2008

you read it. what is tried and true? he didnt mention which one(s)! and i've read and can only recall certain instances that were similar to mine but no one close enough to mine or for me to realize it anyway. once again thanks for the help

Reading compressor maps is a great way to start researching for a turbo. However gawdzilla's point is 100% true. Looking at real life results is equally as important

Now with that said your compressor map math is definately off if you are coming up with 500whp out of 2871s at ~29psi, so I wouldn't trust those results anyways.

that is what i figured once i finished all the math they had. so i messed up somewhere. can anyone guide me so i know for future reference.

maybe start at step one. can it be agreed that i need 65lbs/min of air flow for my goal. or is that my first mistake?

[WhatsADSM]

65 sounds about right.

[ATpossible]

awesome atleast im on the right track...how about psi required for this sized engine? stock rb26, thanks again for conformation

[StricNyne]

this might help you out a bit also

http://www.skylinesaustralia.c...60R-5

8 pages of dyno results with a ton of turbos, and differant setups

[BoostFab]

why not bump it to the GT30* ? a bit extra leg room for more power at a lower boost.

[WhatsADSM]

Sounds like you are working at this backwards or something.

To do the compressor map you will need figures on the VE of the engine in question through the rev-range.

You then plot the engine flow (based primarily on engine size and VE) over various pressure ratios and see which pressure ratio will give you the 32.5 (TT remember) lb/min you are looking for.

awesome atleast im on the right track...how about psi required for this sized engine? stock rb26, thanks again for conformation

[ATpossible]

this might help you out a bit also

http://www.skylinesaustralia.c...60R-5

8 pages of dyno results with a ton of turbos, and differant setups

wow thanks so much i like already from first page i saw some setups similar to mine. thank thank thank

why not bump it to the GT30* ? a bit extra leg room for more power at a lower boost.

thanks for the suggestion but now i think im just trying to understand more of how people choose the right turbo(s) for their goal. dyno graphs are great too!

Sounds like you are working at this backwards or something.

To do the compressor map you will need figures on the VE of the engine in question through the rev-range.

You then plot the engine flow (based primarily on engine size and VE) over various pressure ratios and see which pressure ratio will give you the 32.5 (TT remember) lb/min you are looking for.

ya i was using general number given by garrett and i came up with 28 psi required to get 500hp out of a 2.6L engine. here is my calculations, see where i messed up?

MAP=[65*639.6*(460+130)]/(.95*7500/2*158)= 24528660/562875= 43.57psia

43.57-14.7= 28.8psig(sea level)

65=lbs/min639.6=gas constant460=part of equation idk what though130=intake manifold pressure which they say range from 90-130.95=VE which they say is 95-98% for 4 valve heads7500=rpm at redline158=engine displacement in cubic inches

did i mess up?

thanks again for help guys

[WhatsADSM]

wow thanks so much i like already from first page i saw some setups similar to mine. thank thank thank

thanks for the suggestion but now i think im just trying to understand more of how people choose the right turbo(s) for their goal. dyno graphs are great too!

ya i was using general number given by garrett and i came up with 28 psi required to get 500hp out of a 2.6L engine. here is my calculations, see where i messed up?

MAP=[65*639.6*(460+130)]/(.95*7500/2*158)= 24528660/562875= 43.57psia

43.57-14.7= 28.8psig(sea level)

65=lbs/min639.6=gas constant460=part of equation idk what though130=intake manifold pressure which they say range from 90-130.95=VE which they say is 95-98% for 4 valve heads7500=rpm at redline158=engine displacement in cubic inches

did i mess up?

thanks again for help guys <IMG NAME="icon" SRC="http://is.rely.net/3-78-13854-l-9FLoUlU ... jsFPXQ.gif" BORDER="0">

I just use a online calculator to calculate the air flow through the engine, under given conditions.

Then use a generic BSFC to get the horsepower... but again its math and all theory so take it for what its worth.

Stealth316 has a great site:http://www.stealth316.com/2-air-fuel-flow.htm

Using 80*F (~15* over a 65* day), and 14.2 for ATM. (Assume 1000' above sea level). That gives you 32.218 g/CF for the density of air.

Then because we are talking about a highly modified RB26 I used 7800 RPM (you do know the redline is 8k right?) and 98% VE. Along with the 32.218 g/CF air density you get 3902.9 lb/hr at a 2.6 PR or about 23.2PSIg.

With a 12:1 AF, .55BSFC, on 3902.9 lb/hr you get 591.35HP. ~500whp.

I dunno where your calculations are going wrong because you are likely calculating in vastly different units. I suggest just using the online calculator.

[ATpossible]

I just use a online calculator to calculate the air flow through the engine, under given conditions.

Then use a generic BSFC to get the horsepower... but again its math and all theory so take it for what its worth.

Stealth316 has a great site:http://www.stealth316.com/2-air-fuel-flow.htm

Using 80*F (~15* over a 65* day), and 14.2 for ATM. (Assume 1000' above sea level). That gives you 32.218 g/CF for the density of air.

Then because we are talking about a highly modified RB26 I used 7800 RPM (you do know the redline is 8k right?) and 98% VE. Along with the 32.218 g/CF air density you get 3902.9 lb/hr at a 2.6 PR or about 23.2PSIg.

With a 12:1 AF, .55BSFC, on 3902.9 lb/hr you get 591.35HP. ~500whp.

I dunno where your calculations are going wrong because you are likely calculating in vastly different units. I suggest just using the online calculator.

thanks again! u r awesome. i will check the math again and see about the online calculator.

actually i wasn't 100% sure on the redline i figured it was 7500 cuz i read it gets max hp at 6800 and redline is usually 5-600 rpms later plus i saw the gauge cluster which begins lined reds at 7500 so it made sense if it was 7500. good to know about the 8k rpm though.