toddk911

Great info everyone!

Yea, a dual stage before and after the IC is more involved, but only adding one more hose line and nozzle really. And most pumps in the kits are more then capable to handle it.

I will have to search for the info that I read comparing single stage after the IC to dual stage (before and after) but the results were WAY better running dual injection points.

IIRC, they found exaclty what Tedesco was saying that before the IC, you get the cooling effect of the air itself, the cooling of the IC (like an IC sprayer) then the second stage was operating as the "cooling of the cooled" effect.

Laust Pedersen

The IC can at best cool the intake air to ambient temperature and WI can cool the intake air to slightly less that its dew point temperature (more than slightly less if an alcohol mix is used).

So injecting before or after the IC (with fully adequate evaporation conditions of the water in both cases) gives the same end-result, namely an intake charge temperature close to the dew point temperature. The only difference is how much water is used.
If water is injected before the IC it actually “competes” with the IC for cooling the intake air.

My recommendation would be to let the IC do its job and then reduce the residual temperature with WI. This also minimizes the water consumption.


As some of you know, I have port WI actuated at 15 PSI boost and it works quite well. Cruising at 3000 rpm shows an EGT at about 1480F and “stabbing it” to WOT, which gives me about 23 psi boost, actually drops the EGT to about 1400F, which probably will increase again at higher rpm, but I have not had time to gather data there.

The port WI has a side-effect I had not considered, namely a rough idle for about 30 seconds after water has been injected. This is because each port sucks at different time and therefore pumps water drops out of the nozzles until the water line between the nozzles is empty. The dripping was minimized by adding a solenoid valve on each side of the manifold supply line.
I should also mention that my PWI is a re-circulating system with an external IC sprayer after the manifold injection.

Laust

toddk911

hey Laust!

Didn't know you were still running your PWI system. Thought last I heard yo uahd some issues.

What was the most boost you were running/holding???

What is the highest "safe" sustained EGT's???

toddk911

"Cruising at 3000 rpm shows an EGT at about 1480F"

Wow, that is with NO boost?? I thought even on WOT, full boost 1,500F was pretty high. ???????

Laust Pedersen

Todd,

Oh yes, I am still running my PWI system and it does exactly what I had hoped (except for the temporary rough idle). The “issue” you are referring to could be one incidence where I didn’t catch a clogged water filter (actually a cheap fuel filter).

I am even running 87 octane pump gas without pinging at 23psi boost, (except for an occasion fraction of a second ping at part throttle high boost, supposedly difficult to program the chip in that region with an AFM system).

I think Chris White once posted similar high cruising EGT’s. Remember the car is running closed loop, i.e. stoichiometric while cruising. On the bright side, a high cruising EGT cuts down the turbo lag. I believe that the “rule of thumb” is, don’t exceed 1600F for extended periods and I have not seen more than 1550F.

Laust

aeronautica86

since this thread has been revived I thought I'd mention - why do the hp/tq curves cross over at ~4250?

TurboTommy

"My recommendation would be to let the IC do its job and then reduce the residual temperature with WI. This also minimizes the water consumption."

This is correct.
IC takes out a percetage of heat whereas WI takes out an absolute quantity of heat.
It is a net gain in density if you take out a percentage of a higher value of heat first (IC takes out heat directly from compressor discharge) and then take out an absolute amount of the leftover heat via WI.
However, Laust, you know my sentiments on port WI. (LOL) I don't like it at all. Not enough time for full evaporation of the water and negatively affecting the burn in the combustion chamber.

Like someone already said, comparing all this with the supposed F1 setup is not the same thing. They used air/water IC first because the cooling medium (water jacket) is alot warmer (actually hot) than ambient air, but still alot cooler than compressor discharge temps (insane boost). Even with the "warmer" cooling medium, it still did some good because of the large delta and the better heat transfer of water, percentage wise (still not nearly as good as actually evaporating water in the charge). Air/water IC also offers less pressure drop, and they could then use a less restrictive air/air IC afterwards (less cooling needed). Reducing pressure drop when working with 50 - 60 psi boost is much more important than getting every last once of heat out of the charge.

That would be the only reason I would possibly have Wi before the IC (to reduce pressure drop slightly). The relatively restrictive IC has to do less work on the pre-cooled charge.
But we're splittin' hairs, here.

Laust Pedersen

Standard question requires standard answer:
HP and TQ curves do not have identical scales on the graph.

Laust Pedersen

What’s going on here, you agree with me?

Phew, that balances things … back to normal.

With equal in-depth claim justification I’ll just say that of cause an appropriate amount of liquid water in the combustion chamber under high boost conditions is beneficial to the combustion process.

toddk911

Good to hear yo uare still running ***** out with this Laust

Wow, so on 93 octane you could be 25+

So how is the car able to handle real high a/f - EGT when off boost but when boost is introduced, even 13:1 is very lean and 1,500EGT is very high?

I mean, heat is heat, knock is knock, regardless of load/boost...right?