Water Injection Thread

[Jemison Richard]

Header tuning is done to help scavenge the cylinder and ensure a clean fresh
charge.  Turbo charging does the same thing by increasing the pressure at
the intake side.  The turbine on the exhaust side represents a restriction.
If it didn't the turbine wouldn't turn!  As such, no tuning of the exhaust
is going to help move the gases through the pipes any faster or better.  You
could make the turbine less restrictive but this is tuning the turbo to
higher rpms with more lag time on the bottom end.

Most turbine kits have fairly short runs to maintain as much heat as
possible (the realm of turbos is the realm of thermodynamics).  It is the
energy of the exhaust gases that drives the turbine.  So, short runs, even
insulate the pipes to retain as much heat as possible.  On the back side of
the turbo, make the exhaust pipe as large as you like! 

Also turbine housings determine the characteristics of the turbo.  Larger
housings produce higher HP by passing more exhaust gas allowing the
compressor charge to purge the cylinder but can leave a hole on the bottom
end as there is a lag in changing the speed of the turbo.  Smaller turbine
housings are much more responsive and can change compressor speed much more
quickly but can become restrictive at higher rpms.  this is the reason some
cars have multiple turbos.  To cover holes on the bottom while providing the
necessary volume at the top end.  

If your application can produce max hp with a single turbo while at the same
time not experiencing lag on the bottom end, money spent on multiple turbos
is wasted money.  On the other hand, if you can only obtain max volume with
a setup that leaves a lag at the bottom end, it is possible the only
recourse will be 2 (or more) turbos.

Quick recap:  A good turbine combination is the marriage of the right
compressor with the right turbine housing.
	compressor must be large enough to supply sufficient volume of air
required at max rpm
	The turbine determines how fast the compressor spins. 
	Bigger turbine housings will flow more exhaust gases but will take
longer to change the speed of the turbo (expecially at low 
		low rpms)
	Smaller turbine housings will flow less exhaust gas but will spin up
much faster (no bottom end hole). 
	There is no advantage to be gained by trying to "tune" the exhaust
by either pipe length or pipe matching at collectors.

Good luck!

Rick

> -----Original Message-----
> From:	Gary Derian [SMTP:gderian at cybergate.net]
> Sent:	Sunday, January 03, 1999 10:39 PM
> To:	diy_efi at efi332.eng.ohio-state.edu
> Subject:	Re: Water Injection Thread
> 
> A couple thoughts:
> 
> Transmissions only see  torque.  Power ratings are not technically
> correct.
> If someone is rating a trans for power, find out the rpm range and
> calculate
> the torque they really mean.  The only effect power has is to heat up the
> lube.  An oil cooler can fix that problem.  Usually its the output side
> that
> breaks when in 1st gear due to the torque multiplication.
> 
> Intercoolers are great for cooling compressed intake air resulting in
> higher
> mass flow.  Water injection is great for its anti-detonation qualities.
> Use
> both!
> 
> A heavy flywheel absorbs torque when the car is accelerating, especially
> in
> the lower gears.  This reduces the stress in the transmission.  It also
> smooths the torque which also helps.  But don't dump the clutch, here the
> flywheel weight hurts the trans.  I think a soft clutch is a great way to
> save transmissions.
> 
> 180 degree headers on a V-6?  Wouldn't routing each bank into a turbo (3
> into 1) result in 120 deg and every other pulse into each turbo?  Same for
> intake.
> 
> AWD is really great for low traction conditions and year-round driving.
> Rear wheel drive with a mid engine and sticky tires should be nearly as
> good
> on dry pavement with way less complexity.  How and where do you drive?
> 
> Gary Derian <gderian at cybergate.net>
>