MPG/Fuel injection question

[frankendat]

The over all goal for my KA24ET is efficiency. I want to find the horsepower/fuel ratio that provides the most power with the least fuel. I understand this might not be the most power possible for the engine or even the most power possible with my setup, but if it is the most efficient, then I will accept less zip (to a point).

With the addition of the turbo and the introduction of more air, more fuel is necessary to avoid leaning out the engine and explosion. The stock injectors on the KA24E (no T) are 260cc. According to the internets the next available size with correct impedance and top rail configuration is a Toyota 315cc injector. 

Using a turbo, for fuel efficiency rather than power, according to the internets, will increase fuel efficiency 10% for a 20% gain in horsepower. Additionally, for best life and operational ability injectors should be sized to operate at 80% of max. I am unable to determine if the advertised specifications for injectors, list the absolute max or the maximum operational (80% of max operational for best life and function) As I am cynical, I assume that manufacturers care little about product longevity and advertise absolute max. 

The 315cc is very close, given my parameters. Two questions: 1. Is my thinking and internets knowledge correct? 2. If so, are there difficulties adapting Toyota injectors to Nissan that I should be aware?

Thank you  

[datzenmike]

1 hour ago, frankendat said:

Using a turbo, for fuel efficiency rather than power, according to the internets, will increase fuel efficiency 10% for a 20% gain in horsepower.

 

 

.... yes,.... but not at the same time. Turbos make power under boost conditions. This is not the way to save gas.

 

Anyone can increase their mileage 10% by changing how they drive. Run high compression high octane. The increase in thermal efficiency will off set the extra cost.

[frankendat]

4 hours ago, datzenmike said:

 

.... yes,.... but not at the same time. Turbos make power under boost conditions. This is not the way to save gas.

 

Anyone can increase their mileage 10% by changing how they drive. Run high compression high octane. The increase in thermal efficiency will off set the extra cost.

https://www.autospeed.com/cms/a_109931/article

 

I like/prefer low rpm power. There are other turbo can increase mpg articles  on the internet and some turbo will decrease mpg articles on the internet. To sum the ones I read up: A low boost turbo on a higher compression engine can increase efficiency and thereby make more power with (proportionally) less fuel. So long as the engine or your foot is regulated to only use a little boost, a turbo can provide a little bottom end zip and a few extra MPG's (maybe only a couple) 

[datzenmike]

Higher compression = higher efficiency but there are problems to overcome. A turbo can help push air into the engine lowering the pumping losses but you need something that makes boost at low RPMs and low throttle levels.  

[frankendat]

On 5/7/2024 at 10:40 PM, datzenmike said:

Higher compression = higher efficiency but there are problems to overcome. A turbo can help push air into the engine lowering the pumping losses but you need something that makes boost at low RPMs and low throttle levels.  

I ran into those hurtles. The BEST solution is to use an electric turbo from a new Audi. They are designed to run in pairs on a V8 but a single would be fine for a four banger Nissan. Either they are too new, or other back yard hacks have reached the same conclusion, because the Audi electric turbos are still over 1k used and they are only one piece of the awesome Audi system. A 72v battery pack charged from regenerative braking and/or a generator off the turbo shaft making the battery pack mostly "free" energy. Audi uses an advanced ECU to balance boost and efficiency. I would simplify it (out of necessity, I have no clue how to reprogram an Audi ECU) and use the Audi turbo only at low rpm, like a launch assist. I would like to use it more but =simple steps. 

While the above works out on paper, it is more complicated than I want to make my truck and my next project (the LJ20) already has the foundations for a hydraulic launch assist, I continue to hold hydraulic over electric for energy storage applications, until batteries become so fantastic, other methods/modes of storage are no longer practical.  

Many years ago, I picked up a hydraulic fan motor and considered creating a "hydraulic turbo" for low rpm operation, run off a high pressure accumulator, charged by a pump attached to an axle or wheel hub and powered by regenerative braking. However, it appears to be a more efficient use of regenerative braking energy to re purpose it directly into powering the wheels for launch assist and not directing it to a turbo, to more efficiently operate an engine, to power a hydraulic pump, to fill an accumulator, to operated a hydraulic motor, which powers the wheels at low rpm creating "launch assist".

[Rustbin]

Have you ever seen a Paxton super charger? It's like a turbo run off the a crankshaft pulley. Probably not as efficient as you would like but I wonder if it could be rigged with an electric assist. Just a uninformed thought.

[frankendat]

On 5/7/2024 at 10:40 PM, datzenmike said:

Higher compression = higher efficiency but there are problems to overcome. A turbo can help push air into the engine lowering the pumping losses but you need something that makes boost at low RPMs and low throttle levels.  

My Audi mindwalk is fun, but I am curious about the questions I posed to start this thread. I am running Aeromotive components (aside from injectors) and asked them similar questions last week, without response. According to the internets a well tuned turbo on a high compression engine should be able to increase engine Torque 20% and increase mpg 3 to 4. I believe this is in addition to any power bump achieved by raising the compression.

From the engine specs, raising the compression of a KA24E 1-1.5 points and adding a turbo (max boost 5-7psi) will yield the increase in torque and the increase in mpg.

 

But, what to do about injectors? Higher pressure through stock injectors to create more flow? The pump will do it without problem, will subjecting the stock injector to higher pressure/higher flow ruin reliability, efficiency and/or performance?

 

Or regular pressure through stock injectors, the low boost turbo leans it out and run more efficient i.e. better mpg

 

Or regular pressure to bigger injectors, no worry of overtaxing injector, extra fuel is on tap if you want to put the right foot down. Is this a recipe for low mpg or will the turbo burn the extra fuel more efficiently and a little more power could be realized, with better mpg. BUT you must be disciplined with the heavy foot. 

 

Thank you

Edited May 11 by frankendat

[frankendat]

2 minutes ago, Rustbin said:

Have you ever seen a Paxton super charger? It's like a turbo run off the a crankshaft pulley. Probably not as efficient as you would like but I wonder if it could be rigged with an electric assist. Just a uninformed thought.

I have. There are small superchargers on Junkyard Thunderbirds which are tempting. An electric turbo and an electric supercharger have some differences, but are basically the same. The same battery/regen/motor concept could be used. Blazing trail on that sort of project is more time, money and energy than I have.