Turbo sizing...T4, 13BT SP, 9.4 rotors.

[Whizbang]

my needs for my hill climb car necessitate the need for a better than stock turbo. Something of a T4 variety.

BUT i am looking for fast spool. Like seeing full boost by 2500 rpm territory. Given a 13BT street ported engine with 9.4:1 rotors, what would allow me to achieve this goal? a divided T4 would be good im sure. But there is not much available in divided for both turbos AND more importantly, manifolds.

[rotorhead87]

Have you considered thinking about getting the stock turbo sent out to BNR to hybrid it?

[TheDriver216]

Manifolds i would say talk to rotaryshack...

[Whizbang]

Originally Posted by rotorhead87

Have you considered thinking about getting the stock turbo sent out to BNR to hybrid it?

a lot of it is the design of the factory turbine housings, amongst other lag related issues. I have ruled out the idea pending a talk with BNR, but im assuming it wont suit my needs and the stock based turbo wont survive what i through at it.

[proz07]

so whats full boost to you? i mean 30psi full boost at 2500rpm aint happening. and being that you have high comp rotors you will have much better response anyway. i assume this is a 2nd gen being you cant find manifolds for it. and opting for the t4 turbo i would say puts you right around the area of a 60/62-1 t04 at maybe 3000rpm depending on how your exhaust is ported. it just seems you would have much better options going with a t3 for response and power as you can still get 450hp out of one. but for a manifold being 2nd gen you may have to get a custom or being your "building" a car you might look at making your own. if you dont have a welder you can pick one up for a couple hundred from home depot that will do 90% of what you need. it will pay for itself in no time especially if you use it to make your own braces/parts (seam welding)

z

[RotaryProphet]

Have you given thought to an individual throttle body setup (ie, what I was running on my 12a) coupled with a water-air intercooler? For 9 minutes balls out, you're going to have a lot of heat to move, so being able to start with ice water, or even a heat exchanger in the back with dry ice in it might just get you there. (particularly when you're at altitude and the heat output from the turbo is going -up- while cooling efficiency from the air-air intercooler is going -down-)

The intake'll let you make use of more power from less boost as well as keeping the intake path nice and short so that lag is virtually eliminated. You still have to size your turbo for the boost threshold you want, but I find that if you port the exhaust to open ten or so degrees earlier, you'll spool it much faster. (ie, the turbo 12a I had would make positive pressure at 3000rpm and was boosted at about 4500; the same exact setup on the bridgeport made positive pressure as soon as I floored it and boosted at 3000)

Also, have you considered any kind of swanky anti-lag setup? For a real rally car setup, you'll need a ceramic exhaust wheel in the turbo to handle the EGTs, but for 9 minutes all out on a rotary, you probably want that anyway, no?

I would think that a T3/T4 hybrid is what you want for the response, but are you worried about the top end? It'll really suffer if you force the engine to exhale through that tiny exhaust wheel full time. A gigantic wastegate set to ~9-10psi would help alleviate that, though. More boost than that and you'll have backpressure issues no matter what you do.

[Whizbang]

Originally Posted by proz07

so whats full boost to you? i mean 30psi full boost at 2500rpm aint happening. and being that you have high comp rotors you will have much better response anyway. i assume this is a 2nd gen being you cant find manifolds for it. and opting for the t4 turbo i would say puts you right around the area of a 60/62-1 t04 at maybe 3000rpm depending on how your exhaust is ported. it just seems you would have much better options going with a t3 for response and power as you can still get 450hp out of one. but for a manifold being 2nd gen you may have to get a custom or being your "building" a car you might look at making your own. if you dont have a welder you can pick one up for a couple hundred from home depot that will do 90% of what you need. it will pay for itself in no time especially if you use it to make your own braces/parts (seam welding)

z

I can actually get T4 as small as a .69 A/R. For the purpose of the hill climbs, i need the turbo to spool and quick. Top end power does need to be there but a peaky top end is useless. Basically i need to maximize the under curve area. Figure a redline of 8000 or less.

I am equipped with a good Lincoln Electric 115v welder (best one i could buy two years ago). But for a good thicker runner manifold, i would need a welder with a bit more OOMPH or a TIG.

[Whizbang]

Originally Posted by RotaryProphet

Have you given thought to an individual throttle body setup (ie, what I was running on my 12a) coupled with a water-air intercooler? For 9 minutes balls out,......

The intake'll let you make use of more power from less boost as well as keeping the intake path nice and short so that lag is virtually eliminated. You still have to size your turbo for the boost threshold you want, but I find that if you port the exhaust to open ten or so degrees earlier, you'll spool it much faster. (ie, the turbo 12a I had would make positive pressure at 3000rpm and was boos.......ime. A gigantic wastegate set to ~9-10psi would help alleviate that, though. More boost than that and you'll have backpressure issues no matter what you do.

Actually the idea of running an air-water inter-fooler didn't even cross my mind. Might be a worthwhile option since i could use some good cooling aids. Only downside is there is a lot more complexity to it and possibly weight. My other option was to run a standard intercooler (cheaper and simple) and run a CO2 fogger on it with a larger bottle.

I'm probably going to run the stock intake manifold system, at least for now, mostly due to funding. The cage is going to come in at about 3200 dollars, so there is some other costs i need to handle first.

I am thinking about running the intercooler and radiator in a v-mount because i feel i could get better cooling and the units could be better protected when the skidplate is placed. Plus there would be little charge pipe to worry about.

As far as a turbo goes, i can get a very small T4 (even down to .69). So will have to play with it. In regards to heat and the testing different setups, i might just run master power turbos and just replace them cheaply when i either destroy one or want to try another setup.

[staticpat]

Originally Posted by rotorhead87

Have you considered thinking about getting the stock turbo sent out to BNR to hybrid it?

I don't know about the rotaries, but BNR did a hybrid turbo for my old supra. It was the exact opposite of what you want for gravel. It wasn't extremely laggy but hit VERY hard when boost came on. Great for a street car, not so much for low traction events.

Right now I'm trying to decide whether an NA bridgeport is going to be too much for my rallycross car.

[proz07]

uumm how thick of a manifold are you looking at doing? i have a lincoln 110 at the house that works just fine anything up to 1/4in it is gas shielded though not flux core wire. if your worried about penetration get some pure argon shielding gas will help your pnetration(higher heat) and you should be able to tack weld aluminum decently enough for hobby/home shop use or tack and take it somewhere to get tigged for a couple bucks. sure you may not be able to plow through the welding because of duty cycly but that welder should do anything you need to do vehicle wise.

and if your looking at under 8000rpm redline a nice t3 would more than sufice id say. get ahold of shawn at a-spec he would be more than able to set you up with a good idea of what you want.

z