Rb25De+Tt With A Difference...

[blk94r33]

In light of my intended DE+T conversion, have been doing some researching about different set-ups, what response/power/reliability issues they get etc and have come up with the following "facts"

RB20DET turbo on a RB25DE+T can make 7 psi by roughly 2000rpm

Rb25DET turbo on a RB25DE+T can make 10 psi comfortably by roughly 3500rpm

My question/theory is, would it be possible to combine these two to make an engine that has a nice fat power curve, boost by very low rpm, but a good power figure by redline?

Ie. if the RB20 turbo was set up in a remote/low mount position, set to 7psi, the RB25 turbo set where-ever it will then fit, set to a higher figure (to avoid the smaller turbo working too hard), with the necessary plumbing to prevent air-flow back through the smaller turbo further in the rev range. What other problems could this present? (Also, i'm using these turbos purely as a guide to explain my idea.)

I remember seeing a set-up in which a smaller turbo was used to spool a larger one, but nothing quite like what i'm thinking....

Thoughts? Flames...?

Edited December 14, 2010 by blk94r33

[JonnoHR31]

costs too much and is too hard for 99.9% of applications.

standard rb25 turbo should make 10psi by 2500-2700 if everythings working properly.

[joeyjoejoejuniorshabadoo]

so you want to make an RB25 de+t+T?

hope you have deeeeep pockets

[blk94r33]

so you want to make an RB25 de+t+T?

hope you have deeeeep pockets

Lol. I thought the costs would probably out-weigh the gains, but was looking at it more from an idea/theory, not necessarily a DE+T+T, even a DET+T maybe. Everyone wants good response, no lag, but to be able to hold it through the entire rev range, I though this might do it?

[joeyjoejoejuniorshabadoo]

if you run them as twins, then you will only have half the manifold supplying each one, so the boost figres are effectively halved

[StealthX]

You'd need some pretty fancy exhaust work to make this happen.

And using the stock turbos would be a waste of time, you'd barely see over 320hp at the wheels, with alot of f**king around.

If you want to do this properly, I'd set it up like this:

Small turbo with BIG (60mm+) wastegate leading into big turbo with smaller (Two 44mm) wastegate

Two boost controllers (set the big one on the small turbo to ~10psi), then the small WG on the big turbo to 15-20psi

Should net you about 400-500hp depending on the turbos and boost.

-GT2560r ($1200) for the small turbo

-GTx3076 or 3540 or similar ($1900-$2200) for the big turbo

-custom manifold (at least $2000-$2500 including all the WG plumbing etc.

Then add $ for the tuning and water/oil lines and not to mention all this wouldn't even be worth it on a standard motor.

p.s. see this:

[TiTAN]

custom twin turbo manifolds to suit 25 head + 2860-9 turbos or for the same power level stick an internal gate GTX3071R/GT3076R on the standard RB25 manifold for much less $$$$

[StealthX]

custom twin turbo manifolds to suit 25 head + 2860-9 turbos or for the same power level stick an internal gate GTX3071R/GT3076R on the standard RB25 manifold for much less $$

Nah man I think he's referring to a compund turbo set-up, not just a standard twin.

[TiTAN]

he may be reffering to a compound setup however its just not cost effective when its going on a bog standard car.

[blk94r33]

In light of my intended DE+T conversion, have been doing some researching about different set-ups, what response/power/reliability issues they get etc and have come up with the following "facts"

RB20DET turbo on a RB25DE+T can make 7 psi by roughly 2000rpm

Rb25DET turbo on a RB25DE+T can make 10 psi comfortably by roughly 3500rpm

My question/theory is, would it be possible to combine these two to make an engine that has a nice fat power curve, boost by very low rpm, but a good power figure by redline?

Ie. if the RB20 turbo was set up in a remote/low mount position, set to 7psi, the RB25 turbo set where-ever it will then fit, set to a higher figure (to avoid the smaller turbo working too hard), with the necessary plumbing to prevent air-flow back through the smaller turbo further in the rev range. What other problems could this present? (Also, i'm using these turbos purely as a guide to explain my idea.)

I remember seeing a set-up in which a smaller turbo was used to spool a larger one, but nothing quite like what i'm thinking....

Thoughts? Flames...?

As i've already said, i'm using this set-up as a way to explain my idea, an idea spawned from my interest in doing a turbo conversion.

Nah man I think he's referring to a compund turbo set-up, not just a standard twin.

Yes! Not just a standard twin-turbo-split-manifold, rather one smaller turbo to run the low rpm duties/good response, then "switching" to a larger turbo for high rpm/good final figure. I think "turbo x-trail" gets the line i'm thinking along? I though simply using a GTR with one smaller and one larger (than factory) turbo, but this would defy the point like hamish said only half the exhaust gas would flow to each at any given time. I'm thinking a set up that allows the best of both worlds, using full exhaust flow to the smaller turbo for bottom end and vice versa. Does anyone understand what i'm trying to explain or is my rant best taken elsewhere?

[StealthX]

he may be reffering to a compound setup however its just not cost effective when its going on a bog standard car.

agreed.

As i've already said, i'm using this set-up as a way to explain my idea, an idea spawned from my interest in doing a turbo conversion.

Yes! Not just a standard twin-turbo-split-manifold, rather one smaller turbo to run the low rpm duties/good response, then "switching" to a larger turbo for high rpm/good final figure. I think "turbo x-trail" gets the line i'm thinking along? I though simply using a GTR with one smaller and one larger (than factory) turbo, but this would defy the point like hamish said only half the exhaust gas would flow to each at any given time. I'm thinking a set up that allows the best of both worlds, using full exhaust flow to the smaller turbo for bottom end and vice versa. Does anyone understand what i'm trying to explain or is my rant best taken elsewhere?

Yeah we get it, but unless you're willing to go all out and make upwards of 500hp, its not going to be cost effective, nor is it going to be much better to drive than a well sized single turbo...

[blk94r33]

You'd need some pretty fancy exhaust work to make this happen.

And using the stock turbos would be a waste of time, you'd barely see over 320hp at the wheels, with alot of f**king around.

If you want to do this properly, I'd set it up like this:

Small turbo with BIG (60mm+) wastegate leading into big turbo with smaller (Two 44mm) wastegate

Two boost controllers (set the big one on the small turbo to ~10psi), then the small WG on the big turbo to 15-20psi

Should net you about 400-500hp depending on the turbos and boost.

-GT2560r ($1200) for the small turbo

-GTx3076 or 3540 or similar ($1900-$2200) for the big turbo

-custom manifold (at least $2000-$2500 including all the WG plumbing etc.

Then add $ for the tuning and water/oil lines and not to mention all this wouldn't even be worth it on a standard motor.

p.s. see this:

Cam, you are winnar! I thought I had an original idea, but alas foiled again. Lol.

As with the 320hp/standard turbo thing, this isn't about the biggest peak figure, rather getting the area under the curve. Would you prefer 500 peak horsepower but low boost until 5000 rpm, or have the power come in at low rpm and slowly raise through the rev range?

[PM-R33]

You thought you had an original idea with a compound turbo setup? lol it's been done for decades.

HUGE costs and as others have said, you need to do it with large turbos to get the effects. Small turbos would not do a thing.

[blk94r33]

You thought you had an original idea with a compound turbo setup? lol it's been done for decades.

HUGE costs and as others have said, you need to do it with large turbos to get the effects. Small turbos would not do a thing.

I'd heard of the setup with one turbo powering another (ie one turbos "boost" spooling another), but not this, so thought i'd ask. Ah well...

[wolverine]

Google "sequential turbo' and make yourself sick with the daunting task of reading it all.

[blk94r33]

On another note, has anyone done any digging on variable vane turbos from a performance aspect?

[STATUS]

simple easy solution is to run the sc14 toyota supercharger first them compound it with a larger turbo. We have seen similar repons to what your talking with sc14+GT3540 with an out put around 370rwkw... the supercharger has more parasitic loss so it wont make the 400 rwkw like it made without it.

wanna see 1000hp of coumpound boost? (mates with the above gt35 + sc14 i mentioned above)

VH45 + GTK1000 + eaton 4500(?)

[ARTZ]

Good son of rajab , just give me a V8

[paulr33]

yeah its a lot of complexity and work for minimal gains, the costs dont justify it

besides a basic GTST (like mine) can wind up 12psi before 2800rpm so how much more do you need really?

it's all in the tune

[STATUS]

yeah its a lot of complexity and work for minimal gains, the costs dont justify it

besides a basic GTST (like mine) can wind up 12psi before 2800rpm so how much more do you need really?

it's all in the tune

unfortunatley many people want more power, so there is definatley merit in a compound system especially if your handy. The 370rwkw compound setup i listed above was done at home in the garage for less than $1500 including buying the charger and all relevant parts.

370rwkw with the same response as your setup..... WIN WIN.