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Discussion Starter #1
Hey guys, Just wondering

If I were to run turbos with an exhaust A/R of .65 A/R on the primary turbo, and .75 A/R on the secondary. Same turbos, just different A/R sizes.....

What would be the advantages and disadvantages of a setup like this?

You would have a fast spooling setup and still have the top end? right?

Thanks.:)
 
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Discussion Starter #2
I answered a question similar to this a while back and I was dead wrong...you cant run two turbo's with different A/R sizes because they will "fight" against each other or somethin like that....I thought it would have been beneficial but it isnt.


later

Hamid
 

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TurboTurd said:
Hey guys, Just wondering

If I were to run turbos with an exhaust A/R of .65 A/R on the primary turbo, and .75 A/R on the secondary. Same turbos, just different A/R sizes.....

What would be the advantages and disadvantages of a setup like this?

You would have a fast spooling setup and still have the top end? right?

Thanks.:)
No advantages. The smaller turbo would be a restriction on the top end.

Tons of other stuff to list...just leave it at it's not worth it to prove that it won't work.
 
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Discussion Starter #4
Hey guys, Thanks for the replys.

I did read a thread on here about someone asking if his HKS GT2835 turbos could be setup sequentially, and the answer came out to be not worth it, like you guys have stated.

But what made me reiterate this was seeing a Skyline GTR with HKS GT2835R turbos with a custom manifold set up with a .67A/R on the primary and a .73 A/R on the seconday. You can see the second turbo come online on the dyno sheet.

Heres the pic of the setup HKS GT2835Rs with .67 Primary and .73 secondary, with custom manifolds:



and heres the pic of the Dyno Chart:




Nice Typhoon by the way! :)
 

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Go with smaller twins then 2835 or 2835R, the ideal setup for an MKIV which hasne't been tested *yet is running the HKS twin starter kit and purchasing two HKS 2540R turbos. Won't go as high on power as the 2835(R) turbos but will get more then rnough with what I was told spool similar to a single..
 
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Discussion Starter #6
Suprascene.com said:
Go with smaller twins then 2835 or 2835R, the ideal setup for an MKIV which hasne't been tested *yet is running the HKS twin starter kit and purchasing two HKS 2540R turbos. Won't go as high on power as the 2835(R) turbos but will get more then rnough with what I was told spool similar to a single..
Heh, I don't quite own a car *yet*(only 15yrs old) but I was just woundering why they have used a setup with different A/R sizes. Is it because they can spool faster than the traditional twin setups and still maintain the montserous top-end?

Not sure about turbo sizes tho, I am trying to find an ideal setup for a 3000GT that will bring me to about 750-800awhp or so.

The reason I am planing on GT2835R's is because from what I have read/researched, they are:

--Newer generation of turbochargers that use the newer Garret core that can handle a higher shaft speed and greater thrust loading than the older cores.
--Better exhaust housing and impeller design (their exhuast wheel is larger than either the HKS GT3037 or HKS GT3037S turbos - they are 90 trim as opposed to 84 trim *i think*)
--The compressor (both wheels and housings) is a better design, in that the efficiency curves of the turbos are almost identical, except the HKS GT2835Rs have an 0.50 A/R and the HKS GT3037/GT3037S series have a 0.60 A/R, which translates to more lag in a street and circuit application with the 3037 series.
--The compressor wheel in the HKS GT2835R is better suited to overspeed (it has a lower efficiency drop off rate when pushing past the efficiency curve).
--They are great turbos for the street and circuit racing and can still provide a fairly respectable level of power to boot.

:D

Or will I be better off with a custom twin TS04 setup?:)
I should be launching from 6000rpm+, so lag is not really an issue, but if I can get if down, why not!?!:D I will be putting power to the ground as effieciently as possible with AWD too.

Sorry about all this sounding like BS and all, but I hope to actually do this some day! :)
 

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I think on the exhaust side it would be ok because you have an equalizer pipe going between the two collectors. What I would worry about with that type of setup on the intake side. Like someone said before they would be fighting eachother. When the turbo with the smaller A/R kicked in, some pressure would probably go back up the pipe to the turbo with the bigger A/R until that turbo spooled. This would be similar to not having a BOV and the turbo surging. Maybe you could put a BOV next to the outlet of the .73 turbo, but then that would blow off a lot of necessary boost. Just my $.02.

-amir

p.s. where did you find the compressor maps for the 2835's and other HKS turbos?
 
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Discussion Starter #8 (Edited)
That pic is of the standard HKS kit - that's not sequential. There are no provisions there for sequential operation. It's very similiar to mine. Furthermore, there is no flex pipe on the downpipe, which means that header will crack right before the flange to the head.

In sequential operation, you must have equal size turbos. If they are running parallel, the only thing that will show up on the dyno sheet of different A/R twin turbos is turbulence.

The A/R for the 2835 series is customizeable. For the Supra, it is available from .61 to 1.04, for example. You get the turbo setup you want.

For a VR4, this is not even an issue. Stick with a twin 16G setup or something similiar.
 
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Discussion Starter #9 (Edited)
Thanks Guys for the info:)

Amir - I haven't found any compressor maps for any HKS turbos, the info about the GT2835R's, I got from the owner of that Skyline, he got 600awhp on that run (444kw)! :eek:

Walser- Very impressive Trap! Going 140mph in the 1/4 must be a nice feeling!

I have a question, since you are using the HKS GT2835's, do you know what would be another twin setup "equivelent" to the GT2835's? Any IHI turbos? (ex. IHI RX6B-TWC77) or any TD-05/TD-06 turbos? (20G, 25G?)

Thanks alot:)
 
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