Turbo; JH or PL?

[jdbubb at verizon.net (Dan Bubb)]

>From the Garret website listed below:

? Engine Volumetric Efficiency. Typical numbers for peak Volumetric Efficiency (VE) range in the 95%-99% for modern 4-valve heads, to 88% - 95% for 2-valve designs. If you have a torque curve for your engine, you can use this to estimate VE at various engine speeds. On a well-tuned engine, the VE will peak at the torque peak, and this number can be used to scale the VE at other engine speeds. A 4-valve engine will typically have higher VE over more of its rev range than a two-valve engine.

That paragraph by itself pretty much answers the question of JH or PL since power is proportional to VE. 

>From Wikipedia:
Volumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders.

The range of VE for a specific engine type is obviously, at least to me, a function of "tradition" methods of improving engine performance. All of those "tradition" methods are aimed at getting more air into and out of the engine which is the definition of VE.

"Traditional" methods needs to be defined within the context of a forced induction engine though. Building an engine with an 11:1 CR wouldn't improve performance if you only had 88 octane gas available just as raising CR on a turbo engine will limit boost and ultimate power.
Camshaft design is also different for forced induction, specifically in the area of valve overlap. Lift and duration can be increased, but overlap needs to be limited to reduce diluting the incoming mixture with exhaust due to the high backpressure in the exhaust system.

An engine that has a higher VE (incorporates "traditional" performance enhancements that are appropriate for a forced induction application) will make more power for a given boost.
And an engine that has a higher VE will be able to run higher boost.

At this point I'm done explaining.
You don't seem to be able to understand how VE could be a function of port or manifold design.
You don't seem to understand that the mass of air in a given volume at a given pressure can vary based on its temperature.
You don't seem to be able to correlate the fact that inefficiencies increase the pressure and heat output of the turbo and therefore the load on the engine while attaining a given pressure at the intake valve.
Not understanding would be fine except you fight me every inch of the way when you either truly don't understand, or you do understand and need to twist what I say to maintain your point.
I have several fine examples should you need to debate this in further mindless excruciating detail.
Dan


From: "LEF" <rocco16@sbcglobal.net>
Sent: Friday, January 12, 2007 8:23 AM
Subject: Re: Turbo; JH or PL?


My response in (parenthetical bold)...

larry
sandiego16v

  From: Dan Bubb 

  anybody that subscribes to Larry's beliefs will never win a race in a boost restricted racing class (...at least not by turning up the boost.  :)  Rules that prohibit the use of certain tools don't prove those tools are ineffective.  In fact, they rather indicate the opposite... ) since the they will have lost the only tuning tool they believe they have at their disposal. (Not the only tool, just the quickest/easiest/cheapest tool; increased boost.)
  As a matter of fact they'll never win a race in a racing class with unrestricted boost.
  Want proof?
  Just go here:
  http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html
  and check out the formulas that reference volumetric efficiency (VE) i.e things that improve airflow into and out of the engine, like ports, manifolds, cams and exhaust systems. Yep, they're part of the equation.
  (I hope others reading that tech article (tech103) can find those references to ports, manifolds, cams and exhaust systems....I couldn't.  A nice paragraph in tech101 talks about the pros and cons of both cast log-type exhaust manifolds  and fabricated tubular-style exhuast manifolds, however.  Maybe I'm looking in the wrong place, Dan, can you point me to a specific part of that link ?   I'm willing to learn.)

  Pressure
  Power to create the pressure
  Heat created from producing the pressure that reduces density and mass air flow
  Detonation caused by the higher heat.

  They all come together and if you make no attempt to optimize the system they all get worse and limit power.
  (Dan, optimizing the system was not the subject of this discussion.  Applying traditional methods (aggressive cams, increased compression, porting & polishing, low restrictions intake and exhaust manifolds, etc.) of increasing hp to the turbocharging arena is the subject.  If you are inferring that applying traditional methods to a turbo engine is "optimizing", then THAT is where I disagree.  I maintain that increasing boost is easier/quicker/cheaper than those traditional methods of increasing the power output of an engine.)

  Again, anybody wants an explanation feel free to ask.
  (Looks like we've both just about explained ourselves out....)
  Dan


   
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