toddk911

"There is no way a k26/6 will make 20psi at 2500rpm. Why not put a water nozzle at the throttle body? Would seem easier"

Yes, MUCH easier, but would not yeild as much in terms of results as direct port water injection.

NZ951

Here is a question, how do you know how much pressure and water volume to put through!!!

roadrunner

Ummm...

High boost and then evaporating liquid water droplets during the compression stroke -- wouldn't that push the dynamic compression a bit overboard? Even with massive cooling of the intake charge, it seems the peak cylinder pressures would be dangerous even if the bmep shows okay...

Duke

1 bar above atmospheric. This was however sligtly uphill.

But my point was that without mention what gear the test was done in, the data is almost useless. The load in fifth is probably enough to spool up most of the turbos out there above 1 bar at very low revs.

So although I get 1 bar at around 2000 rpm in fifth I need at least 4000 rpm to get the same boost in second.

blitz951

I have been in this car making many runs and I dont know at what RPM the car hits 20 PSI but I will say that there is no lag that I can feel. In fact the times I did look at the boost gauge it pegged 20 PSI instantly. The car doesnt feel like a turbo. I feel like the power came on like in my other friends 69 Camaro with a 427. It is easily the fastest 951 I have been in and if you look at the dyno you can see that it just keeps pulling like hell.
Shane, the car owner, always told me that the key to a cars performance is in the head/cam and he proved it. This car simply has no weakness in any part of the powerband and the mods done made a huge difference in the car and I know as I have been in the car before and after. I am interested in Danno and shane doing something with a better turbo but what is interesting is that the k27/8 doesn't seem to be running out like they usually do on other dyno sheets and with much less power.
After having a Powerhaus head which gave me nothing all I can say is thanks for the import and domestic tech. and experience for making the 951 come alive.

Laust Pedersen

“Olli Snellman
your water injection looks interesting. What kind of injectors are you using ?”

I took inspiration for the water injection system from here http://www.turbomirage.com/water3.html including the injectors (nozzles), which I machined for this particular set-up.


“rage2
What turbo are you using? I vague remember my car with the stock turbo (K26/6), but I'm fairly sure it never made 20psi of boost at 2500rpm.
With my current turbo (good for around 480rwhp), I need at least 4500rpm to see 20psi of boost.”

I am using the standard 26/6 and a wastegate that doesn’t leak due to exhaust pressure. The water may be helping in making boost


“Duke
A note.. why is it that nobody mention which gear when talking about boost @ rpm?
In fifth gear for example I get 1 bar @ 2000 rpm with a K27/8....”

There are two parameters of interest here, one is how much boost can be generated at a given rpm and another is how long time it takes to get there. The numbers quotes are in 5th gear. It is interesting to note that the spool-up is progressively faster as the boost increases.
Danno wants to make a video of my instruments while on a test drive so you can get a first hand impression of the boost rpm and gear selection relationship.


“NZ951
Here is a question, how do you know how much pressure and water volume to put through!!!”

I am relying on other peoples experience on this. Too much water and it will not work. Too little and there is no cooling advantage. However there is wide acceptable range. The flow control in my case is a very simple on/off pressure switch (set at 13psi) and it is fully adequate for now. To control it as precisely as fuel injectors with a fuel pressure regulator is a gross (financial) overkill, but a progressive control could be justified.


“roadrunner
High boost and then evaporating liquid water droplets during the compression stroke -- wouldn't that push the dynamic compression a bit overboard? Even with massive cooling of the intake charge, it seems the peak cylinder pressures would be dangerous even if the bmep shows okay...”


The following graphs are borrowed from Aquamist’s web-site (http://www.aquamist.co.uk/). They have an excellent explanation of the advantages of water injection.

Here is a graph of the relative combustion pressure vs. crank angle showing normal combustion (green), slight knock (yellow) obtained by advancing the timing 3 degrees, intense knock (red) by advancing the timing maybe 10 degrees and the result of water injection (blue) with a 6 degree timing advance. Typically the maximum instantaneous torque is obtained at 30 deg ATDC, so it is particularly interesting to note that the area under the blue curve in that region is quite a bit larger than any of the others, meaning that more torque is generated without increasing the peak pressure.

http://www.aquamist.co.uk/dc/technic/chart.GIF

Here is a graph of exit temperatures (in centigrade) vs. boost pressure for various compressor efficiencies.

http://www.aquamist.co.uk/rescr/faq...s/adiabatic.GIF

And finally a graph of the temperature drop as a function of the water injection flow rate (for a 2L engine @ 6000 rpm and 1 bar). It is interesting to note that temperature can drop below ambient, equivalent to a hypothetical intercooler with more than 100% efficiency. The absolute temperatures are only relevant if water is injected early in the air stream, but the relative drop is also relevant for port injection.

http://www.aquamist.co.uk/rescr/faq...ss/intercol.GIF

The typical water consumption is about 1/10 of the fuel consumption when the system is on, so in reality a 1 gallon water tank should last 1 to 3 gas tanks.

Laust

toddk911

And what I still don't get is that Corkey Bell is completely AGAINST water injection. It has been around since the 40's and has proven to be one of the biggest "bang for the buck" improvements to performance, especially for forced induction applications.

Danno

From reading the book, it didn't sound like he had much experience with it. The other turbo book by McInnes has more details on water injection. Very neat chart in that book showing air-fuel ratio+water-injection requirements in relation to boost levels.

toddk911

Ok, I'll have to check that one out.

Danno, I sent you an email also.

BoostGuy951

It seemed to me that Corky Bell was against it as a band aid for bad tuning. I don't think he was necessarily against it in terms of it allowing you to run more boost than your octane will normally allow.

Mark-87-951

Danno,

How does that Guru head work compare to what Lindsey is offering with their flow numbers and talk of exhaust velocity?

Mark

TonyG

I'm interested in hearing about the head as well...

TonyG

J Chen

Hi Laust,
How about spraying a fine mist of
water at the inlet of the compressor
as well ? If we can control the heat
build up within the compressor housing,
would'nt it allow the compressor wheel
to work more efficiently ?

LukeSportsman

Couldn't we run into the same problem with water as the guys used to have with draw through carb'd turbos? The drop lets hitting the compressor at such speed pitting the blades like a boats cavitation issues? Or is this just old wise tales? I know that many have used pull through with centrifugal blowers, but that is much less rpm and less sustained rpm. I could be just in left field, but that would be a concern of mine.

Luke

Sam Lin

It's been done on turbo cars without any compressor damage, but the couple cases I know the water was very carefully directed at the turbine center so it didn't impact the blades directly.

Sam