NewbVetteGuy wrote: ↑Tue Apr 23, 2019 1:56 pm
The way I see it, you have roughly 3 options with suboptions under each or you can choose a combination of these options:
Each alternative option has different up-front vs recurring costs and power and MPG trade-offs that need to be considered.
1. Reduce Cylinder Pressure
2. Boost Octane / Detonation Resistance
3. Mitigate Detonation with Electronics
1. Reduce Cylinder Pressure
1a. Reduce "Dynamic" compression: Lower Static CR OR alter cam timing or combination of both (reduces power and MPG some, but less at higher compression ratios); up-front cost and labor required for both, no recurring costs. Retarding the cam timing works here without initial cost. I think altering ignition timing makes for less cylinder pressure before combustion so I'd technically lump it here, but mostly because I'm lazy and I don't have a better" bucket" for it.
1b. Reduce Airflow / VE intentionally: "Hobble" engine with intentionally restricted induction (seems like a horrible idea, IMHO; documenting only for completeness)
2. Boost Octane / Detonation Resistance
2a. "Chemical Octane Boost": Use higher octane fuel, fuel blends, or octane boosters that change the measured RON/MON rating of the fuel burned. NO up-front costs (assuming your fuel system can deal with your fuel choice; big assumption, I know), largest recurring costs. Combining this option with other options reduces the recurring costs by allowing cheaper, lower octane fuels or less high octane fuel in the blend.
2b. "Kinetic "Octane" Boost": Improve the engine's quench & squish -only helps so much and involves up-front costs, but no recurring costs; maintain power levels, even extremely slight power gains possible. Yes, I'm using the term "octane" loosely here to refer to detonation resistance vs. actual fuel RON / MON ratings.
2c. "Thermal "Octane" Boost": Reduce combustion TEMPERATURE to increase detonation resistance. Per Vizard, every 8 degree drop in IATs = a 1 point RON/MON equivalent increase in fuel octane. Cold air intake and intake thermal coatings are useful. I have no idea how much coolant and oil temps will help, should be "some". One-time, up-front costs, limited effectiveness, effectiveness dependant upon weather / air conditions, but NO RECURRING costs and actually INCREASES power, slightly decreases MPG (colder air slightly decreases power; other thermal management can slightly improve it). Fattening your AFR goes here as the extra fuel resists detonation via cooling; MPG cost, obviously. -I think EGR goes here...
2d. Water injection, IMO, falls under "2c" as a thermal solution focused on reducing IATs, but Meth injection is particularly interesting as it both drops IATs (2c) AND acts as a 2a. Chemical Octane Booster boosting the actual measured RON/MON values of the fuel in the combustion chamber.
3. Mitigate Detonation with Electronics
These solutions are all roughly the same and AFAIK include EFI + Electronic Ignition Control conversions or modern electronic-controlled Water/Water+Meth Injection systems. Big $$$$ up-front, but maintain / improve power, less expensive to continue to operate than higher octane fuel and provide plenty of other benefits. Holley Sniper has brought the price of EFI + electronic ignition control down to about $1,500 so less initial outlay than in years past, but still a significant investment.
Other options involve selecting a "static" set of trade-offs: you make your decision, then you live with that decision for a long time. Electronic solutions allow you to change your mind and can balance maximum power and MPG with minimum recurring costs by ensuring that timing is always appropriate for the fuel, weather, and driving conditions. The electronic solutions involve the maximum "Dynamic Range" of cost, performance, and detonation resistance. With a fuel octane sensor and electronic control, you can change your mind on what trade-offs you want at any time (money gets tight, run on junk gas with junk timing and fat AFRs; want to play round with high octane fuel or has the weather gotten cold? -Get max perf.)
-I'm really curious if there are any electronic ignition controllers that can integrate a knock sensor and adjustable timing controls WITHOUT a full-fledged EFI system. Holley has some great products on the ignition control side of things, but AFAIK, the only option to control them is a full-fledged EFI system.
Adam