Quote:
Originally Posted by soxfan143
The reason the T28's are choking so badly on this motor is because of the manifolds they are bolted to. If you put a GT2871RS on this motor with a Full-Race quality tubular manifold DESIGNED for that turbo and motor it would spool up at 3K and pull like a freight train to redline. The other main problem is the lack of efficiency in the turbine sizing and design when applied to this motor.
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like a freight train to red line...im sorry this is a bit hard to believe. Just because you put a larger A/R exhaust side on a turbo doesnt mean it will automatically flow like you want it to. If you get too big, you will over flow the turbo. I do agree with the fact that the turbine size and design was a poor choice for this motor. But...That t28 will only flow so many lbs/min so you are limited to the power you will be able to produce at any boost pressure. Forget a minute about the pressure....The simple fact that you are limited on the amount of air this turbo can move.
Not saying i can tell the future but even if this turbo was capable of 350 - 400 whp, you'd be sqeezing the life out of it. I would rather have a larger turbo, sacrafice a little mid range power and it pull like balls up top, while keeping the longevity of the turbo.
As for the back pressure issue....i KNOW you need back pressure. me saying "back presssure ftl" doesnt mean i just wanted 0 back pressure. A lot of how the turbo spools up has to deal with at what angle the exhaust gases hit the turbin wheel. It of course, starts with the quality and design of the turbo manifold you use but after that collector, it works like this...
With smaller turbines, the exhaust gas velocities are higher and hit the wheel more tangentially.
The exhaust gases are the line at which they hit the wheel (the ball)
This provides quicker spooling of the turbo and more back pressure at higher rpms.
With larger A/R turbines, the exhaust gas velocities or lower and hit the wheel more radially. I dont have a picture for this, but imagine that the exhaust gases enter the wheel going from the circumference inward along the radius. This delays spooling but creates less back pressure at higher rpms allowing it to breath.
...if you didnt already know all this, i hope this helped.