Water injection (was: Re: fuel cooling intake air)

[Axel Rietschin]

----- Original Message -----
From: "Bruce Plecan" <nacelp at bright.net>

> > It is my general perception that diesel engines runs slower than SI
> engine.
>
> Our small diesel (least as called by another in another post) is run at
> 6,000 to 6,500 rpm
> My gas engine I spin to 5,500 rpm.

We previously mentionned "higly tuned" SI race engine (I assumed "car
engines"), and often, those engine runs well above the speeds you just
mentionned. I've heard of water injection in circles discussing F1 engines
from back in the turbo days, in terms that corroborate the thermochemistry
aspect of WI. I didn't realized it at the time. Sure, those peoples had
different constraints and very different operating ranges. Also, I believe
that Sir Henry Ricardo was involved in some serious competition engine
research. BTW, check out www.ricardo.com - there is a lot of interesting
bits on their site.

> > Also, it seems that the benefits of water on combustion are realized at
> high
> > rpm [...]
> >If we are talking F1 engines, it may well be
> > around
> > 18000 rpm or more.
>
> It would seem like the upper 25% might be a resonable figure.
> Say 14K+ on that app..

At 14K and up, I can more easily imagine having serious problems to burn
that mixture in the 40-50 useful degrees. It's just incredible that some
engine can actually run in the 20K range.

> Folks often sem to obsess on advancing, and sometimes miss other items.

I agree. That's why I believe it is necessary to measure and record things.

> > Also, IMHO, the maximum torque speed (as in your statement above) is
> > certainly not a speed where any "excess of energy" cannot be "converted
in
> a
> > timely manner" - or it would not be the "maximum torque" speed, indeed.
>
> You've lost me with that statement.

Maximum torque speed if where the engine is the most efficient, right? So,
empirically, at that speed the energy is "converted in a timely manner".

> > Then, given that, as noted by Mr. Colon, "the total energy is of course
> the
> > same" and that you need "sufficient fuel and air" so I still fail to see
> how
> > you can _gain_ anything by making your engine swallow its air already
> > saturated with water vapor.
>
> Saturated?. At what level is that?.  My version is, just experimenting
with
> the mine amount of timing, lean best performance, plus 1-2 graduations
> (depends on fueling adjustments), and min water for best performance
(again
> plus a couple percent).  I consider reliability, as a very important
> concern.

I implied that the air had to be saturated given the water flow you've
mentionned (a gallon/min IIRC). Sure, saturation depends on air temp, but as
it drops, you may well end up at 100% RH at some point in the intake system,
then it would start raining :)

>  They claim the gain comes from
> > vapor pressure, so no complex thermochemistry here, according to them.
>
> I can claim all kinds of things.  So all information posted today, just
> stops because of their claim?.
> That just make sense to me.

No, nothing stops. It just gives a little more perspective on the subject.
Maybe not black or white. I don't question anyone's credibility, but the
least I can say is that we can observe many different opinions on the
subject.

> Like I said we tune for performance, so I can't guess at actual ratios, if
> not visible at our 6,500 rpm I doubt it would be much on your 8,000 rpm
> engine either.  If I correctly understand what your saying.

It is not visible on my engine, indeed.

> > Also, what Saab is
> > able to achieve in a research lab may not be easy to reproduce at home.
> For
> > example, I know they use a variable compression engine in their quest
for
> > maximum efficiency.
>
> Or anyone with less then oem manufacturing analyse.


Axel (leaving for a week)




----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org