Quote:
Originally Posted by Libor
Peter, there is something I wondered about.
Lately, I've been going through the many recent papers about development of various piston engines with port injected gasoline as base fuel and ethanol/methanol as mean of charge coolant. They tested 3 methods of charge coolant delivery: port injected, direct injected during intake stroke and after intake stroke. Last method allowed highest levels of boost pressure and power without detonation due to highest cooling effect I.e. lowest in-cylinder temperature. Difference was really huge, 1.05 bar for PFI, 2.4 bar for second method and 4 bar for last. Note: very low engine speeds and overall Lambda 1.
So my question basically is, do you use pre-turbo system mainly due to simplicity and reliability? I can see the benefit in cooling of inlet air which can dramatically increase mass flow for any given shaft speed. But with the above in mind, would direct port injection I.e. very close to engine block, be superior for detonation suppression @ given flow rate?
Many people talk about time factor for atomization, and surely, water can absorb huge amount of heat even by the time its in the engine so the heat of compression in the turbo is really not a problem, but isn't it a bit of waste? We want maximum cooling effect in the engine, not in the manifold 
I would be happy for your input  |
I do my system for simplicity and performance.
A few years ago now I had two special Aquamist systems made for me by Richard (bespoke twin pump set up's) with all kinds of stuff available (pre turbo special rings with center discharge) + individual injectors to place in the ports.
My test was simple:
I ran pre turbo
I ran post IC
I ran pre IC
I ran port injection
The one location that gave me most power was pre turbo, the ones that gave least performance increase were post IC and port injection. I ran a fixed volume of liquid and just changed the location of delivery.
I deduced from my tests that if the pre compressor gave the best acceleration and power that then I could simply use my very own basic RRWEP140 system without much of the complexity and fine orifice injection components that are prone to blockage and failure. That is why I stuck with my own system and its location.
Of interest is the location changes:
You could move the nozzels from pre turbo and to then to the throttle body and have absolutely no increase in acceleration. All other parameters being held equal.
For that test you list above, I'd love to try something like that one day. I'd need to modify some rotor housings and figure out a whole heap of ancillaries to make it a reality, if it works there it should work for rotaries, its just complex to make a reality 
Makes sense to me that most of the cooling is happening where it is needed most (during the compression phase), as you say though I wonder what the effects are at Lambda 0.65. It is beyond my realm of experience really. In my own case I just went with a system that is basic and works at conventional setting ranges and gives a measurable performance benefit.