dart pro 1 turbo set up
TECH Apprentice
Joined: Nov 2005
Posts: 304
Likes: 0
From: Newmarket, Ontario
Importance of turbine selection with engine eff. / goals Great Discussion keep it up,
On a side note I agree with MM, once you a fixed amount of air at a fixed temp in the combustion chamber and the valve closes, it should be identical. The only thing that must be considered is if the additional boost pushes the compressor map into a better or worst eff. range. how does this effect the backpressure / heat between the turbo/heads and on the durability of the engine.
One thing to think about (same turbo)...
1) Turbo flows 80lb/min @ 20psi and is 85% eff.
2) Turbo flows 80lb/min @ 15psi and is 65% eff.
No doubt the increased pressure heats the air more, however if when considering the effect of both the increased pressure and turbine eff. the air temp was lower, wouldn't this be a better setup?
On a side note I agree with MM, once you a fixed amount of air at a fixed temp in the combustion chamber and the valve closes, it should be identical. The only thing that must be considered is if the additional boost pushes the compressor map into a better or worst eff. range. how does this effect the backpressure / heat between the turbo/heads and on the durability of the engine.
One thing to think about (same turbo)...
1) Turbo flows 80lb/min @ 20psi and is 85% eff.
2) Turbo flows 80lb/min @ 15psi and is 65% eff.
No doubt the increased pressure heats the air more, however if when considering the effect of both the increased pressure and turbine eff. the air temp was lower, wouldn't this be a better setup?
Originally Posted by cablebandit
i dont understand how the 20psi combo sees more backpressure since it has to use more of the exhaust energy to spin the turbo........please someone try to explain this to me cause i dont understand that.
say 10psi boost you have 15psi exhaust backpressure
20psi boost you have 25psi backpressure etc.
in a good designed system this ratio is fairly constant.
it seems you get more and more heat when you run more boost which means compressing the intake air more and more. That leads to detonation, use of higher octain racing gas, you would have to lower timming. With a fully cnc ported head you wont have to use more boost to move more air as you would with a head that it would take less boost to move the same amount of air. CFM's is what i look for not boost. Then the stock cast heads are 15* and the aftermarket heads are mainly 11* better air flow. Thicker castings too. Ya feel me
