COULD you?

[LAMPSguy]

Sure you could, but why...there, I said it for those who inevitably will.

In looking at the various engines, it seems like this:

for a given displacement, lower compression for lower Octane costs 10 HP
Injected over Carb gives you 10 HP

Extra displacement (360 to 375 or IO390 vs IO360) seems to net you 10 HP.

With the possibility of 180 HP limit/medical thing going, what do you think about the viability of this:

Higher displacement injected engine with lower compression for 180 HP on lower octane (maybe auto fuel)? Might be more $ than it's worth, just wondering what the brain trust thinks?

[Walt]

Increase cubic inches and/or compression = increased HP

FI vs Carb = No HP gain

FI does increase efficiency as a result of better fuel distribution (ability to lean further).

IO375 gives more HP due to more CI with the same compression ratio (you can still run "mogas").

[smokyray]

Nick,
I just entered my 23rd year of RV-8ing and most of those running MoGas. partly with an 0-320 and carb, other with IO-540 and injection (Rocket) I currently purchase non-ethanol MoGas by researching www.pure-gas.org and add Marvel Mystery oil and CD3 on occasion. The following link shas alot of good info on the subject.

For me, keeping costs low and getting the best return is primary. My airboat engine builder friend has alot of field testing with Lycomings and fuel. His customers run 91 octane MoGas up to 9.0:1. Higher comp and they visit the airport for liquid gold. Airflow performance and Silverhawk both claim MoGas is OK. If 100LL does morph into something else or disappear, there are options...

http://www.chadandbrittne.com/Engines.htm
http://www.eci.aero/exp/IOX340_pr.aspx

V/R
Smokey

[frankh]

Thats exactly what we got now. The IO360 with standard 8.5:1 compression will run quite happily on premium mogas. Rocket Bob runs 87 octane regular..I haven't got to running regular yet.

I run 10% ethanol laced premium with a twin electric fuel pump system, but the engine runs perfectly.

Frank

[LAMPSguy]

What is the issue with ethanol?

It seems from what I have read for auto engines when it came online that it was mostly a seal issue as some are not as resistant to ethanol and will not last as long. If that is the case, are there seals/chemicals/etc available for the entire airplane fuel system that are ethanol safe?

Additionally, I wonder if there is an altitude/pressure component to the combustion process with ethanol fuel as compared to high octane non-ethanol fuel?

I know these are issues that many are dealing with, and this is a bit of creep from my initial question, sorry about that...just trying to add to my knowledge.

[frankh]

Thats exactly it. You need to understand the ethanol reistability of every component from tank up to where the goes into the engine.

The other (bigger) issue is vapour lock prevention with Mogas.

I took the approach to avoid both issues by building a twin electric fuel pump system, Airflow Performance FI system, teflon fuel hoses.

This dealt with 99% of all the compatibility issues and because the pumps are not heated by the engine and are not sucking on the fuel at any point it eliminates the VL question.

I Had to change out the fuel tank drain orings to flourosilicone ones for a grand cost of about 50cents.

There are those who claim the mechanical fuel pump is ethanol tolerant. I honestly don't know if that is true or not.

I have run my engine with ethanol laced mogas up to 18,000ft, run LOP, hot days and any operating condition you can think of.

There is some evidence of ethanol absorbing water (potentially more an issue on a carb where the surface tension ofwater can in theory prevent the fuel passing into the engine, with FI this is a non issue) but in the 400 hours or so I have not had even a hint of any issues.

I purposely avoid 100LL from both a cost and environmental impact point of view.