Supercharger performance
04-29-2007, 06:06 PM
#253
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Originally Posted by lookingglass
Isn't Porsche using them in their new 911 Twin Turbo? Some company in the US designed it for them if I remember right.
04-29-2007, 11:48 PM
#254
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The Porsche 997 uses a Garret Turbo with variable vanes around the periphery of the turbine. Smiths has a similar approach except it uses gates rather then vanes. More reliable and no overspeed.
Volvo's is more like like a 2-stage turbine system controlled by manifold pressure although it has only one turbine and a stator. They've used VGT systems on their diesel trucks for a while now, but they've had issues with sticking vanes.
Volvo's is more like like a 2-stage turbine system controlled by manifold pressure although it has only one turbine and a stator. They've used VGT systems on their diesel trucks for a while now, but they've had issues with sticking vanes.
05-01-2007, 05:21 AM
#255
Originally Posted by Rotary God
.Exactly. Alot of people miss that point entirely. Many people use an overly small exhaust side on the turbo which only makes it worse. It's a fact that higher exhaust backpressure makes an engine more prone to detonation than lower exhaust backpressure. Hmmmm..... I wonder what that means when it comes to superchargers vs turbochargers and detonation!
Wonder if this will become a major argument in favour the super charger vs the turbo on our engines ........
05-01-2007, 10:17 AM
#256
Probably not.
Corner seal failures are going to be a function of port design, anyway.
BTW - I don't agree with the correlation between higher exhaust "back pressure" and higher detonation. Higher latent heat is the issue with exhaust retention. High port pressure at the exhaust will lead to charge dilution which reduces the likelihood of detonation.
Corner seal failures are going to be a function of port design, anyway.
BTW - I don't agree with the correlation between higher exhaust "back pressure" and higher detonation. Higher latent heat is the issue with exhaust retention. High port pressure at the exhaust will lead to charge dilution which reduces the likelihood of detonation.
05-01-2007, 11:20 PM
#258
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Originally Posted by MazdaManiac
High port pressure at the exhaust will lead to charge dilution which reduces the likelihood of detonation.
05-02-2007, 12:17 AM
#259
Originally Posted by rotarygod
Where the heck did you get that idea???
That is the essence of EGR. You can jack the static temps all you want - if there is an over abundance of non-combustibles in the chamber, detonation will be suppressed.
"Back pressure" is not the actual issue leading to detonation. It is elevated temps in the engine materials from reduced flow.
That is, to some degree, offset by reversion.
05-02-2007, 05:38 PM
#262
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Sorry Ray it's been a busy week with the new job training and all. You actually caught me when I was at a restaurant the other day and by the time I got free it was nearly 10 PM here. I don't remember what time zone you are in but I thought it was too late.
05-03-2007, 11:38 AM
#264
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Originally Posted by Charles R. Hill
If you wait a few more weeks I'll know exactly what to do to it when I get there and Fred will know exactly how to port it, if you wanna do what I am doing. Low compression rotors, maybe? 
05-03-2007, 01:09 PM
#266
Originally Posted by Charles R. Hill
If you wait a few more weeks I'll know exactly what to do to it when I get there and Fred will know exactly how to port it, if you wanna do what I am doing. Low compression rotors, maybe?
No, I want to do a straight rebuild - maybe a slight clean-up of the ports.
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