single Vs. twin turbo

[Arctc Wolf]

don't use wheel and tire combo's 2 compare to turbo wheels. u forget that 2 keep the same diameter, more tire has to be used on a 15" wheel than a 17" wheel, and makes up for the difference. neways, back to turbo's.

after the exhaust valve opens, it takes time for it to reach the turbo. the amount of time it takes depends on how close the turbo is to the heads. this is why ppl don't tent to put turbo's far away from the heads except in a few strange cases. yes, ppl have put them somewhat far away, but this is usually done to allow use of equal length primaries to also help spool the turbo faster and create less backpressure thru the turbo itself. something that also affects spool up, is the distance the air has to travel through the piping and into the motor. the shorter the path, the quicker boost will be achieved. granted, this might only account for 100-300 rpm, and not much of a worry on a street car, but on the dragstrip, it could mean a loss by a bumper, or a win by a bumper.

There is usch a thing as too small a wheel though. Larger wheels have better aerodynamic qualities because the material can be more precisely shaped than on smaller wheels. this is why civic's and integra's can't run twin turbo setups. because out motor has enough displacement, we would be able to run a twin-turbo system on our cars that would be efficient, but as I said b4, costly due to the amount of fabrication involved, as well as the clearancing and spacing inside the engine bay itself.

[qksl2]

<blockquote>quote:</font><hr> don't use wheel and tire combo's 2 compare to turbo wheels. u forget that 2 keep the same diameter, more tire has to be used on a 15" wheel than a 17" wheel, and makes up for the difference. <hr></blockquote>

Unfortunately that is wrong. A 15" tire weighs roughly 60% of what a 17" tire does. They use the exact same properties as compressor and turbine wheels, and are affected by the exact same physical forces. This is not debatable. The farther away the weight is from the axis, it takes exponentially more energy to spin it to the same velocity. Someone here will understand what I'm talking about...

<blockquote>quote:</font><hr> back to turbo's.
after the exhaust valve opens, it takes time for it to reach the turbo. the amount of time it takes depends on how close the turbo is to the heads. this is why ppl don't tent to put turbo's far away from the heads except in a few strange cases. yes, ppl have put them somewhat far away, but this is usually done to allow use of equal length primaries to also help spool the turbo faster and create less backpressure thru the turbo itself. <hr></blockquote>

The distance is ONE variable. And it's not strange instances where longer paths are used, its more powerful instances. By tuning the turbo manifold w/ the correct diameter pipes, and for the accoustic and flow properties (taking into account exhaust gas temp, velocity, and firing order), you can create a long tube primary manifold that spools much quicker than a more turbolence prone, "smash 'em together" log style manifold. The reason people use shorter manifolds is 1)cost, 2)packaging, 3)heat control... and they attempt to justify it by saying that it "spools more quickly". The reality is that a properly designed long primary manifold is far better.

But I digress... as I like single turbo styems better myself, just wanted some facts and misconceptions rested. ;)

[QUOTE Larger wheels have better aerodynamic qualities because the material can be more precisely shaped than on smaller wheels. this is why civic's and integra's can't run twin turbo setups. [/QUOTE]

Huh? Seems quite unrelated there.

And remember that displacement is only one factor to turbo sizing, RPM is the other.

Ian

[ July 26, 2003: Message edited by: qksl2 ]</p>

[jamie]

there's that turbo company that has the turbos in the rear of the car. isntead of a muffler...

other than that, i can offer nothing to this debate.

[qksl2]

I saw that... crazy sleeper setup there lol.

Ian

[xjarayax]

Not crazy sleeper from behind, or when they drive through a puddle, not to mention the oiling system alone on that thing cost $500, or maybe $800. To me it's a joke.

[ July 27, 2003: Message edited by: xjarayax ]</p>

[jamie]

they offered up reasons why a puddle or dirt won't affect it. it uses a special filter. and that it would take entirely to long to get up to the engine to break it. or something like that. plus it seemed to be more efficient than any other setup out there...

[slow]

efficient, and mounted 10 feet from the heat source... don't quite understand how that works.

On the twin vs Single debate, Normally the single turbo's used are larger than twins, (even combined) so on most cars with single turbo conversions, they are setup for high rpm horsepower. Look at some of the fastest supras, 4000 they start to spool, then just make crazy power.

Most single vs twin setups are apples and oranges, and hard to compare.

I do not see anybody doing TT's on a 3.8 easily. I would like to be proven wrong.

The single seems to be a better solution, but still is very hard to actually acomplish, I am not too familiar with the 3.8 f-body's & owners, but am learning more. But assuming they are similar to the 3.8 stangs, 95% of people who talk about turbos just talk, and very few follow through.

I wish anybody the best of luck.

Ryan.

Ryan.

[Arctc Wolf]

ok, sure, a 10 lb., 15 inch wheel has it's mass closer to it than a 10 lb. 17 inch wheel, but u also have to put tires on those wheels, and to get the same diameter tires on each rim, the 17" rim will require 2 inches less of sidewall total(basically 1 inch less all the way around), so the weight can be made up for here. I know what u mean about all this. this is why a 2.75" driveshaft will get u more power on the top-end than a 3" driveshaft will that is made of the same material.

I know that euqal length and tuned headers will help make a lot more power, a lot less backpressure, and quicker spool up, but there is a limit untill u get too long and a shorter, unequal length header will start to spool quicker. in a perfect world, u want a tuned, equal length header that is as short as possible.

basically, when comparing wheel sizes, I was showing how some cars can use twin-turbo apps, and some can't. if the motor is too small to run twin turbo's w/ decent areodynamic specs on their wheels, then they'd be better off using 1 bigger turbo. compressor and turbine wheel design also affect spool up and choke limits. This is why garrett's new turbo's are able to spool quicker than most others, because they improved on their wheel's aerodynamic designs and make them easier to spin and so they pick up more air to force into the motor.

[qksl2]

^^^Well, I'm glad you agree with me now. ;)

<blockquote>quote:</font><hr> 95% of people who talk about turbos just talk, and very few follow through.
<hr></blockquote>

Exactly. That's why there's so much mis-info in this thread.

Ian