Big Single V Big Twins (~500+rwhp)

[Brockas]

Just posting up my personal experience with both setups.

Went from twin HKS 2835 (rated to 760hp, roughly the same size as GT-RS's)

to a single GT3582R (rated to 750hp), with a GCG T4 rear housing.

Not much else changed on the car (slightly bigger fuel system, more out of security than necessity). In terms of things that would affect the power, it was a simple bolt-off bolt-on job.

There isn't any headwork, and the cams are 270' x 10.8mm Procams.

The GT35 setup isn't anything special. Ebay manifold and some ceramic coating...

Bold lines = GT35, thin lines = 2835's.

Blue = power

Green = torque

(The GT35R line stops at 7500rpm, but we took it to 8100 with power staying above 500hp).

The results speak for themselves....

We believe there is another 20++hp in it minimum if we push the tune and sort some restrictions in the intake / exhaust, but I wanted a direct comparison between this and the old twin setup before we change anything else.

Edited July 22, 2009 by Brockas

[R31Nismoid]

You virtually make everything the same as Marko's RB30DET if im reading it all correctly

Just a question though...

Why do you have the dip between 3500-4000rpm? Turbo looks like its ramping up nicely and then sorta drops off for a bit... any comp surge?

[Brockas]

Just a question though...

Why do you have the dip between 3500-4000rpm? Turbo looks like its ramping up nicely and then sorta drops off for a bit... any comp surge?

Haven't asked Sean (my tuner), but from what I gather that 'ramp up' is just as he increases the throttle percentage, then once its at 100% throttle it builds boost.

It definitely doesn't have a flatspot on the street at 3500.

Here's the low-boost tune (1.5bar, ~22psi), and it has that same ramp up as Sean increases throttle, but in a different RPM range.

Edited July 22, 2009 by Brockas

[SysLink67]

That has completely thrown a spanner in the works for me, I was going to go twin low mount with a 2.8L stroker kit.... after looking at that a single seems to do a better job...

Any other pro's con's of single setup?

What work / parts have you included in your built engine?

Do you find Allstar garage know their tuning? what ECU do you run?

My car is r32 gtr. Would have thought a single larger turbo would have more lag? I'm building my configuration with only response in mind, would a single be applicable for this?

Cheers

Rob

[Adriano]

Hows the transient response? I would agree that thats just the throttle ramping up, as its making about the right power n/a there.

Edited July 22, 2009 by Adriano

[zebra]

Im Impressed

Peak power at 6500 on high boost

but cant help notice that the 1.5 Bar tune (low boost) after 6500rmp makes the same power.

What is high boost? boost drop off maybe? or was it tuned that way?

[fatz]

100 ponies at 3k

500 at 4700

man this thing would do awsome skidz

vids please( of skidz) i give no shit for dyno vids!

does it chirp second on wet grass??

[discopotato03]

I tend to think that a GT2835 , from memory cropped GT30 turbined GT3071R in 52T , is a bit more than half a GT3582R so twinned would have more capacity and start later than the GT3582R .

A "GTRS" uses the smaller 9 bladed GT28 turbine in 76T , the 2835's cropped 10 bladed GT30 turbine is a couple of mm larger in 84T .

A closer comparison could have been a pair of GT2530's (GT2860R 63T) vs the GT3582R in of course twin scroll twin gate form .

Just my thoughts , cheers A .

[9krpm]

Could you let us know what dump pipes did you have with the big twins?

[Lithium]

A closer comparison could have been a pair of GT2530's (GT2860R 63T) vs the GT3582R in of course twin scroll twin gate form .

Just my thoughts , cheers A .

Yeah as much as I am pro-single turbo, this comparison is like the other side of the typical twins vs single comparisons where people would get a T88 RB26 and run it on an engine set up to run twin GT2530s and say "Look, they made similar power but the GT2530s spooled way better! Twins ftw!". A paid of GT2835s are quite a bit more serious than a single GT35R, though having said that the lag seems quite substantial for a GT35R and he says its rated to 750hp?! Is it definitely a GT3582R?

Good power, either way

[Brockas]

Dump pipes were CES ceramic coated ones.

Disco, you're probably right, in a perfect world I'd love to compare it to 2530's etc, but after reading the 2835's were rated to 760hp (as mine were either the 46T or 42T versions, I forget) and the 35R at 750hp, it's still not a bad comparison.

fatz, Haven't had a chance to do any skids yet, will this weekend when I go to the track. Yeh, she'll spin one up on wet grass....

Zebra, high boost is 1.8bar, but we suspect we've reached the point where we've maxed either the intake or exhaust, as more boost increases the midrange but not the top end. We'll look into this soon, and will see if it makes another 20+ hp.

Adriano, so far I've found the transient response to be quite good. At any speed over 4k the 35R spools bloody quickly and you're rarely ever waiting for power. With the old setup, I had to keep it above 5500rpm for the same throttle response.

Syslink, Sean at Allstar knows his shit, but if you're south of the river Ant Scali @ x-speed is also brilliant. Either of these two will be able to help you out. I am running a PowerFC non d-jet.

Talk to Gav Beer, as he has a similar setup as yours. 2.8L with low mount 2860 -5's. Last time I spoke to him about his setup, he told me that if he were to do it all over again, he would go a single HKS T04Z instead of the twins.

The advantage for the single for me is simplicity if something goes wrong at the track. It's easy to work with, plus a single has less surface area on the rear exhaust housing, so less heat as well.

This is a complete list of whats in my motor:

N1 24U Block

TOMEI Forged 86.5mm Pistons

Pauter Forged Rods

TOMEI Gasket Kit 1.2mm 87.0mm bore

ARP Rod bolts

JUN Valve guides

ARP Head Studs

ARP Main Studs

TOMEI Procams (270' x 10.8mm)

TOMEI Valve Springs

TOMEI Cam Sprokets

TRUST sump extension

JUN High Flow Oil Pump

N1 Water Pump

Cheers

Edited July 23, 2009 by Brockas

[Lithium]

Disco, you're probably right, in a perfect world I'd love to compare it to 2530's etc, but after reading the 2835's were rated to 760hp (as mine were either the 46T or 42T versions, I forget) and the 35R at 750hp, it's still not a bad comparison.

You said it again - where did you get the idea that the GT3582R is rated at 750hp?

http://www.turbobygarrett.com/turbobygarre...2R_714568_2.htm

[Angus Smart]

4088r gets close to 750

[Brockas]

You said it again - where did you get the idea that the GT3582R is rated at 750hp?

Actually not sure!!

In my head it was always a 750hp turbo (from back when I had one on my first car a few years ago).

In regards to twins v single, as I said in my first post, I'm simply posting up personal experience with both setups I've used. I'm not trying to say all singles are better than all twins, but if anyone was tossing up between these two setups for their own car.... well... heres some real world results.

[Swiper the Fox]

peak torque 1500rpm earlier should help at lot at the track. HKS 2835's have never impressed me...the guy i originally bought my HKS 2530 kit off 'upgraded' to them...they never made the expected result for him. You really need to pump big boost through them to work with a big head and cams...if not...forget it.

Good result though...nice one.

Edited July 23, 2009 by DiRTgarage

[Lithium]

In regards to twins v single, as I said in my first post, I'm simply posting up personal experience with both setups I've used. I'm not trying to say all singles are better than all twins, but if anyone was tossing up between these two setups for their own car.... well... heres some real world results.

Yeah cheers for sharing, its a really nice example of a GT3582R setup - should be good to hear how it goes at the track, please share your impressions when you get a good chance to try it out

[discopotato03]

Actually I should have asked before , were those 2835's running RB26 type GT28 IW turbine housings or the HKS T28 flanged GT30 turbine housings and external gate/s .

Really those cropped GT30 turbines don't like living in GT28 turbine housings and the turbine efficiency in this form is a bit lame .

I am curious as to the turbine housing on the GT35R , I think ATP Turbo in the US have been selling a T4 flanged turbine housing to suit 35R's but not sure if it was twin scroll or not .

From a point of view of convenience that cast TS HKS low mount RB26 manifold may be a show if you were interested in looking for one but they're not common . They have a cast divider leading up to the top waste gate mounting point .

I think the theory is that the TS housings help increase volumetric efficiency either side of the peak so increase the average I suppose .

Yes I fully understand the less bulk and complexity of the single vs the twins . My private theory is that with elevated power levels like yours it's getting a bit restrictive trying to force that much exhaust gas volume through a "T3" sized flange and turbine housing .

Full Race (LOL Twin Scroll) Geoff Raicer has said that once you get up close to 500 Hp worth of exhaust gas flow the pressure rise starts to limit power and increase temperatures .

Also if you look at big ratio "T3" (I think Euro T4 is the proper name) flanged turbine housings in twin scroll form the inlets can only get so large without the walls getting too thin .

Anyhow should feel pretty frisky with around 200 Hp/liter particularly when its starts 1000+ revs sooner .

To pull it down significantly further probably means more cubic inches and dollars .

Have fun , cheers A .

[Lithium]

Full Race (LOL Twin Scroll) Geoff Raicer has said that once you get up close to 500 Hp worth of exhaust gas flow the pressure rise starts to limit power and increase temperatures .

Scarily enough, there are people now claiming up around 900hp on T3 hotsides these days!!

8.75 @ 162mph on E85 with a T3 flanged turbo in a 4door car running interior/glass etc is a bit mad and not something I've have ever expected to see without NOS:

[SimonR32]

ah me hubber she so friendly

so much better than those shit low mounts, well done

now get down to x-speed... give me a call and ill give you my run number to overlap the graphs!!!

[Brockas]

Actually I should have asked before , were those 2835's running RB26 type GT28 IW turbine housings or the HKS T28 flanged GT30 turbine housings and external gate/s .

Really those cropped GT30 turbines don't like living in GT28 turbine housings and the turbine efficiency in this form is a bit lame .

Yes I fully understand the less bulk and complexity of the single vs the twins . My private theory is that with elevated power levels like yours it's getting a bit restrictive trying to force that much exhaust gas volume through a "T3" sized flange and turbine housing .

The specs of the 2835s can be found below. Not sure if it helps. They were the 48T .62 versions rated to 380hp each:

The main reason I went with the GCG T4 rear housing on the 3582 was because I believed the T3 flange was going to cause a serious restriction. So far no complaints, however I can't definitively say it's better unless I tried the T3 flange on my car.