Marcel Burkett

Well the guy who made the down payment on my single last December recently contacted me and said that he has the balance of money for me , so It seems like I will be selling it after all . I also noticed that the price of the GT42 has since gone up from $1750 to $2400 (on ATP's site) , which is almost the same as a pair of smaller GT-R turbos . So i guess the cost factor has been negated , so now I am leaning more and more toward a pair of custom twins ! , how do you guys think a pair of GT35R 's with 0.63 a/r turbines will suit the needs of my new semi pp motor ?? , I am looking for the air flow to make big power , but the response of a smaller turbo since my car is primarily a street machine. I also read a post where a member said that he was getting compressor surge when using one of those turbos , should this be a concern ?, is the GT35 not a proper match for the 13B ? , will this be a bigger problem with two of them ??

Howard Coleman

iTrader: (6)

marcel,

the gt35r makes 65 lb/min. that's one gt35r...

65 lb/min times 10 divided by 1.3 equals 500 rw rotary hp.

(2), (as in two gt 35r's) times 500 equals 1000 rw rotary hp.

all of the above is premised on the motor being able to spin two really big wheels. it probably can at 9000 rpm. below 9000? probably pretty doggy.

i suggest you find something around 75-80 total lbs per minute.... 575 rwhp will fry just about any street tires you will find. you did say your car is primarily a street machine...

good luck,

howard coleman

Carl Byck

In Supra land 2x2835 are pretty darn laggy for their output. A properly sized single allows SOOOO much more flexibilty, and can make 1000hp if that is what you are ready for. A GT74, or 76 will make near 1000 hp if you can spool it, if not you can downsize, those turbos are ~1000.00 on supra forums(plenty for sale)and you can use those guys results to choose a proper hotside. The Supra guys found out they can make the power pretty easily, supporting it in the long run is a different story. Go to the dyno section of Supraforums. 1000rwhp is passe. Carl

t-von

iTrader: (8)

I used that formula for a 20b and got 325 rw rotary hp.

65lb/min times 10 divided by 2.0 equals 325 rw rotary. Maybe I don't get it but, why is it lower?

Howard Coleman

iTrader: (6)

the 1.3 does not relate to displacement .

1.3 is used for all rotaries including the 20b. the formula is used to find peak rwhp relating to the maximum airflow from various turbos.

since there is fixed amount of oxygen in 65 lbs/min ( at standard temperature and pressure) a fixed amount of maximum hp can be made regardless of the number of rotors. the caveat being that frictional losses are somewhat different comparing 2 and 3 rotor motors...

howard coleman

t-von

iTrader: (8)

Thx for the clarification. This turbo talk is finally starting to make since to me. LOL

So in other words, for example if this turbo made 500 whp on a 13b at say 25psi this same turbo would make 500whp on a 20b but at a lower boost level because the 20b breaths better? And even though the boost level is lower on the 20b, the turbo would still be at it's max efficiency but at a lower boost level? Did I make any since?

Marcel Burkett

Any one else have an input ??? , I understand what Howard says , but the only other turbo I think may be suitable for my needs is the GT 30 , the GT30's flow is 50lb/min , would a differance of 10 lbs/min make such a big differance in spool time??

HEns

a twin gt30 setup will still be a pig on the street, id suggest a twin gt25 setup for the street, you will have a nice powerband, which should see full boost by 3000-3500rpm.

the biggest id consider is a twin gt28 setup as sold by a few places such as rx7store.com i believe, you might want to search around the forum for a dyno sheet.

teamafx

iTrader: (4)

im twin t04e's, ill be having a dyno sheet soon

Howard Coleman

iTrader: (6)

i agree w HEns..

the gt30 does between 52 and 65 lbs/min depending on how it is configured.

that would make between 800 and 1000 rwhp. ( of course assumes the motor can spin the compressors to the max) it might happen at 9000 but as HEns correctly states, it would be a Kia around town.

the GT28 makes between 31 and 35 lbs.
that'd be between 477 and 538 rear wheel... with the above caveat.

the GT25 makes 31 lbs or 477 rwhp.

pick your poison.

howard coleman

Marcel Burkett

Have you driven (boosted) the car yet ?, how does it spool ?, are your turbos bb ? , what 's your porting type ?

I know that the GT28's will work , but I think they'd be a bit too small . I am thinking , the smallest I'd go is a pair of GT30's . I used to have a 1/2 Bp with a large turbo that everyone said would have been too laggy and would have spooled after 6500 RPM . They were wrong !! , in fact from 6300 to 6500 RPM the boost moved rapidly (spiked) from 12.5-13 straight to 20+ psi !! , the turbo was making 12psi boost by 5000 RPM and thats with a pair of 35mm gates and no boost controller . I am wondering if you guys are taking my porting into concideration ??

Marcel Burkett

A few members have come on here and said that their GT42R equipped FD's are producing insane power with minimal lag ??, so why would a pair of smaller units with less rotational mass and pushing the same volume of air through a set of "Big Ports" spool any slower ??
There is an full bodied FC with a pair of HKS GT3037 's (GT30's) running 9's on a bridged ported motor , that certainly doesn't suggest too much lag ! ,mow I'm not bitchin' about what you guys have said , in fact I am greatful for you thoughts and your interest , but all these questions stay in my head un-answered . Given the price of one of those GTR turbos I just don't wan to make the wrong decision (twice) !!

bolo_fd

iTrader: (2)

i wouldn't be worried about money if ur thinking of making that kind of power because you're going to be breaking alot of stuff. hahaha
i hear a few people with twin setups but havn't seen any dyno sheets. i would really like to see how these turbos are working out for people.

Marcel Burkett

I already broke and fixed everything , the only weak points left are my axles.

gkatzens

Do you understand how to read a compressor map? The surge line on most larger turbos means you can't use them in a twin setup that hits ~15psi before about 6000rpm. I'd bet money that's why Kevin Wyum's turbos failed...

Marcel Burkett

I havn't seen a surge line on any of the GT series maps , so its a bit difficult to see where surge would be likeky to happen.

Marcel Burkett

Correct me if I'm wrong , but doesn't HKS make a twin GT3037 kit for the FD ?? , if this is so , then I guess the GT30R turbos would be what I'm looking for since they share the same specs or even the smaller GT3071 R ??.

Xcessive

I think the gt30rs would be a good pick, from our supra experience. The compressor maps are pretty broad compared to rhe gt35rs. We had to have precision turbo make us custom
gt35rs for our supra because the original ones surged real bad. Gt30s=1000hp & gt35rs=1400 hp Gt4276r= 1100hp
We run GT4276rs on a couple fds and they spool and rock!!!!!!!!! with the big footprint and seans manifold. Ralph

t-von

iTrader: (8)

We keep hearing how the Gt42r rocks on an Fd but, we never get to see any dyno numbers showing the power band. Would you have any dyno plots?

Marcel Burkett

Finally , input from someone who's actually done it , not "dissin" the rest of you , but real world experience is sometimes (most times) different than the theory .
I think the GT3071 (71mm compressor wheel , 50lbs/hr) should be adequate , I dont need more than that , with a pair I should get good response and plenty of air to make some good power.

RageRace

Why not just go pt88 midframe and be done with. If your doing it just for the pimp factor, thats one thing. But, "IF" you dont have a packaging issue, why go twins. You seem like your adding compexity for nothing.

Marcel Burkett

I've read all the pro and cons , when it comes to going twin , I've owned and driven a Large Single equipped car for close to a year , although not at full potential , I still have some driving experience , so I know how a large single is on the street . After all this , I have decided that I AM going twin , I am prepered to get it done and working right , the complexity involved isn't an issue for me , I can do most every thing required , except weld , an this I can get done professionally and very cheaply. So , I guess I am trying to say , please dont change the thread into a twin vs. single one , I just want some input into what twins to choose , I think I have finally decided on the GT3071R , thanks guys for all your help.