pgfpro wrote:From my dyno experience I have always seen an increase in power with a race fuel with a very high octane verses a lower octane fuel with WI or even the same high race octane fuel with WI. Plus I can run a leaner A/F ratio when running race fuel without WI. Now this is done by increasing boost and not the CR. So maybe you could see gains with WI and race fuel by running a higher CR??? IDK
Absolutely with high octane race fuel vs lower octane and WI you will see more advantage with the race fuel by being able to run leaner and get high temps. However, if you could increase compression/boost to or over the detonation threshold of the high octane race fuel you were using, then by using WI you can effectively raise the detonation threshold over that maximum for fuel alone, increasing the VE of the engine accordingly to a higher level than without WI.
I have only ever built one very high CR naturally aspirated V8 engine where we tried this. CR of 15.5:1 and VP C16 race fuel. Without WI we had detonation, with it we could run improved ignition timing and limited detonation. As a result we saw higher engine and chassis dyno power figures. Problem was the ECU was picking up intermittent detonation and retarding timing or throttling the engine back once the engine was at max operating temp. We surmised heat induced detonation likely from valves or plug tips even with the coldest plug. So we machined the pistons back to 15.0:1 and ran again and found that we right at or just over the edge of what we could get from the fuel so the WI increased power slightly from reduced intake charge heat and more advantageous ignition timing.
pgfpro wrote:The packaging issue intercooler verses WI I think would be a wash. Just some quick calculations I come up with around 5.5 gallons for the low side and up to 8 gallons of water for the high side that would be needed for a one hour race. This is based on the 15% to 25% of fuel flow WI rule.
From a weight view your probably right, it would be close to a wash, until late in the race where the weight of the water would be reduced through usage. But from a purely size/space perspective, I woudl tend to think the intercoolers and pipe work would likely be a considerable compromise as to packaging. Also the WI would allow a shorter intake path helping throttle response and providing less opportunity for extra heat to soak back into the system through compact (read cramped) packaging constraints.
pgfpro wrote:The other thing I don't like about WI being used in the new F1 turbo engine is that induction system will be built around running air mainly with a small amount of fuel, based on the DI that will be used. With the rule... "Over 80% of the maximum permitted fuel flow rate, at least 75% of the fuel flow must be injected directly into the cylinders." So 25% will have some type of endothermic reaction based on fuel.
This may result in two sets of injectors, one DI and another set external to the DI system like those currently seen spraying into the top of the runners. This would provide the evaporative cooling effect of the fuel tumbling down the intake path as well as interaction with the valve stems and heads for cooling etc.