Single turbo conversion ..

[cortexx]

I've been reading alot of information regarding twin turbo vs single turbo applications on an RB26 but i'm having a hard time really finding good reliable info on what constitures a responsive single setup.

Is having a smaller single setup a viable soultion for a reliable 600ish hp with great response ? I know some of you have singles running , what power , usuable power band , response do you have from them and what (if it exists) is a perfect siingle setup ?

I know this is a loaded question also so i'd like to keep debating polite (if possible) and factual.

I ask this because it's something that isn't out of the realm of my future plans.

[r33_gtst]

The bigger the turbo the longer the lag
For your goal of 600hp, a gt35 could get you there
Borg Warner have some of the best big single turbo's right now
A semi built or built motor will increase spool time also
I'll let the guru's take it from here, I'm no scientist, just a science student

[gtrjon]

There is no lag as long as your in the right gear. granted your power band will be shorter but most big singles have built motors that can rev a little higher to increase the power band. anyway im one of the few on here with a big single set up. i have a fully built long block from the ground up with some tomei 270 10.25 pro cams and the built head to match along with a 6boost manifold, a bw 91-79 67mm turbo, and a tial 60mm wg. I make right now 512awhp @18 psi on 92 pump with meth on rgs mustang dyno. I make full boost at ~5100rpms. hope some of that info helps

[coston]

Could you potentially make the same power with twins and reach full boost at a lower rpm? Or would that require a significant increase of boost pressure compared to the 18psi you mentioned

[NismoS-tune]

Single turbo setups are cheaper, lighter, less confusion piping/hoses/shuffle, same response or better and big power. There aren't many big power twin cars out there like there are big singles. The ONLY benefit to twins is the bragging rights that you have twins. Even neons and cobalts have single turbos man. I went twins cause I was clueless. I should have gone twin scroll, which is what I'm looking into for my new project car.

[coston]

Figured so. Just thought I'd ask for the sake of this thread haha

[cortexx]

OK ill admit it - i have my eye one one of these :-

http://www.treadstoneperformance.com/product.phtml?p=1849&cat_key=578&prodname=Borg+Warner+7670+EFR+Turbo

with a 6 boost twin scroll T4 flange manifold.

[Dragon Humper]

Good fuel and an agressive off-boost tune will help alot in the "lag" department. Even running 92 with Ethanol in it will work too, you really ramp in the ignition timing off boost and pull it back a bit as you get to about 70% of your low boost target. I am running 36deg at WOT and up to 39deg below WOT to give me as much torque as possible. This also gives you as much exhaust energy as possible spooling the turbo quicker.

I got full boost from dead in the water at 5200ish and as low as 4400ish if the turbo has some wind in it already. And that is with the second biggest single turbo that Trust makes (T88H-38GK is the next step up).

I would much rather run a slightly oversized single at 17psi to get 600hp than perfecly sized twins at 24psi (N1s for instance) to get the same thing. The engine will be much cooler and happier.



Jon.

[r33_gtst]

There is no lag as long as your in the right gear. granted your power band will be shorter but most big singles have built motors that can rev a little higher to increase the power band. anyway im one of the few on here with a big single set up. i have a fully built long block from the ground up with some tomei 270 10.25 pro cams and the built head to match along with a 6boost manifold, a bw 91-79 67mm turbo, and a tial 60mm wg. I make right now 512awhp @18 psi on 92 pump with meth on rgs mustang dyno. I make full boost at ~5100rpms. hope some of that info helps

5100 rpm full boost on a fully built long block? Wow, I thought it would have been much less.
I hit full boost at 4100rpm on my hx40 (roughly the same as a gt35) @ 20psi
How much wheel hp does 1psi on your set up add? If I can remember mine is 14.4rwhp per psi

[Skym]

Compound turbocharge engine with small turbocharger, big turbocharger (lag less turbocharger setup) -

http://www.youtube.com/watch?v=42Xa1HO1IwI

Driving with a compound turbocharged engine -

http://www.youtube.com/watch?v=42Xa1HO1IwI

Gives best of both worlds, power, response.

Some put a small supercharger, bigger turbocharger, as shown on this compound turbocharged 4cyl Lotus Elise -

http://www.youtube.com/watch?v=DD2XAs-871o

The idea came from the supercharger, turbocharger compound setup they used on the old Group-B rally cars in Europe (Lancia Delta S4 with KKK turbo, Roots supercharger) -

http://www.youtube.com/watch?v=ZXzkkGqv9Es

Do some research on those Group-B rally cars (1985 Lancia Delta S4, etc) -

http://www.groupbrally.com/lancia.shtml

It has been done to RB26, there's a photo (red top RB26) floating around the internet somewhere at I think was Tokyo Autosalon showing how it was done with supercharger, turbocharger compound setup. But have never seen it installed in a Skyline.

In Japan Bee-R compound turbocharged a S15 -

http://www.youtube.com/watch?v=4SjNgVH_HN0

[collector240sx]

cortexx,

If your serious about going single, I wouldn't blame you one bit. It's a lot easier to work on the engine, looks better, and most of the research in the last 15 years has been in mid to big frame turbo. The turbo that have came out the last few years are really efficient, but you still have to choose one that is right for your application. Spend some time online looking at air flow table, and see how your application would fits on the table, it will give you a good idea where you'll see peak efficiency and how long you'll be in. This is were choosing the right sets of cams to give you the right flow can bring you real good gains.

And I would suggest that you look into the quick spool valve, on supra it's been proven to spool over 500 rpm quicker with it.
Might not sound like much but trust me it's enough.

You can also look at minimizing the length of your intercooler pipes, and keep them at the optimum size for flow. The less air to displace between the outlet of the turbo and inlet of the intake, the better (less to air to compress, less lag).

P.S. One problem with running a big single is when you want to run low boost on a good quality manifold. Since the manifold are usually design for maximum flow, they don't let enough air out of the waste gate. Some use twin waste gate to try and resolve this issue, with some success. The real solution is to have a smooth curve from the manifold to the waste gate, not that 90% turn crap that you see on most manifold, but this make the manifold flow less efficiently.

Anyway good luck

[gtrjon]

5100 rpm full boost on a fully built long block? Wow, I thought it would have been much less.
I hit full boost at 4100rpm on my hx40 (roughly the same as a gt35) @ 20psi
How much wheel hp does 1psi on your set up add? If I can remember mine is 14.4rwhp per psi

it completely changes how much power you gain or even lose for that matter each psi you change. there is no standard every psi i up i gain x whp. rule of thumb is 10whp per psi tho. although that can change greatly

[gtrjon]

on another note i have to say 6boost twin scroll manifolds are hands down the best on the market for the $$. i have to say full race makes a great unit but at almost double the cost of the 6boost its no comparison. and not a fan of the "quick spool valve"

[cschepp]

Paul I have thought about going this route a couple times and I really seeding see why I wouldnt. The rpm of full boost usually arrives around 4-5000 rpm and the potential hp is amazing compared to twins. Of course you see those crazy Japanese cars with 1000 hp running twin gt35's or something stupid like that but why not run one turbo. It's so much easier to work on and it does look killer. But the only thing that holds me back is if I get pulled over and the cop asks me to pop my hood, then I would have some explaining to do

[r33_gtst]

^why would you have some explaining to do let alone pop your hood?