Fuel prices get me down...

Post by **Spike** » Wed Jul 18, 2007 4:45 pm

I have a close friend that has an O-320 on an 8A and its a fantastic combination. Great speed with a small fuel burn. Its a good way to go.

RV7Factory · Post by **RV7Factory** » Wed Jul 18, 2007 6:28 pm

All this talk about the price of fuel... I feel I must confess my sins.

Recently, I've had unpure thoughts. I've actually been thinking of scraping the RV-7 project in favor of the new Rans S-19. There, I said it, and it feels so much better to come clean.

Seriously... I know it won't do 200MPH, but 5gal/hr sure sounds good to me. If I started it right now, I would probably still fly at the same date on the calendar... no joke.

Am I still welcome at the RB Dinner? Guys? Anyone? Hello???

cjensen · Post by **cjensen** » Wed Jul 18, 2007 6:32 pm

Brad, Brad, Brad...you may not be welcome in my, er, your tent next week!

It's still put together with rivets...but you don't bang 'em. Hmmm, not sure I like that idea.

It does look pretty sweet though! Maybe have a sit in it next week???

RV7Factory · Post by **RV7Factory** » Wed Jul 18, 2007 7:15 pm

cjensen wrote:Brad, Brad, Brad...you may not be welcome in my, er, your tent next week!

Chad, I think the tent is big enough that we won't have to see each other anyway.

JohnR · Post by **JohnR** » Wed Jul 18, 2007 7:52 pm

Alright, you guys keep talking about fuel prices. In my friends 8 the last time we went to breakfast he was showing a fuel burn of right around 6 gph and we were still cliping right along. I'm sure if you went the same speed as the Rans S-19 you culd get close to the 5 gph. The difference is when you want to cross the country you can go up to altitude and cruise along at close to 200 mph and get 25+ mpg. Can't do that in the Rans.

I do like the Rans and will probably try it on for size myself. My next one, if there is one, will probably be a Cub type though. Something to just hop around in the local area and go check out the farm and see what the neighbors are doing.

I better finish this one first though.

rv8or · Post by **rv8or** » Wed Jul 18, 2007 9:31 pm

" I've actually been thinking of scraping the RV-7 project in favor of the new Rans S-19."

BLASPHEMY!!!!!!

I've been looking at the Xenos motor glider with longing eyes lately...I should be spending the time building

You guys have fun next week. Pop a few for me! (insert cool Chad Beer smiley here). Oh wait, I found it

Joe

RV7Factory · Post by **RV7Factory** » Wed Jul 18, 2007 10:56 pm

RV8or wrote:BLASPHEMY!!!!!!

Mea culpa!

Remember I got college and a wedding to save for now.

Too bad Joe. I say this with sincerity -- I was really hoping you would be there.

Next year maybe.

RV7Factory · Post by **RV7Factory** » Wed Jul 18, 2007 11:02 pm

JohnR wrote:The difference is when you want to cross the country you can go up to altitude and cruise along at close to 200 mph and get 25+ mpg. Can't do that in the Rans.

I hear you John, and I completely agree. My original mission profile was to go fast and have fun, but with recent lifestyle changes, at this point I would simply settle for getting airborne.

(no compliants intended, I wouldn't change a thing)

cnpeters · Post by **cnpeters** » Wed Jul 18, 2007 11:09 pm

An 0-320 and a throttled back 0-360 so both were going the same speed would have very close to the same fuel burn. As someone mentioned, throttling an RV back to the same cruise as the Ran's may be close. The question is whether you would have the discipline to throttle back with the larger engine.
An EFIS with fuel flow monitoring, LOP operations (some folks even doing in carbed engines), and knowing your plane's performance to the detail seen in the CAFE reports will go a long way to stretching your dollar. I truly believe we are peaking globally with oil supply (even more conservative energy economists give it a few years), and will see fuel prices forever worsen. We WILL be at our European flyers' current prices in the not so distant future. Budget your flights, set your speeds accordingly. Even if I can't afford this after 20 years, I can look back with the joy and sense of accomplishment it gave making this and flying it in the meantime. We are doing things most folks on this planet don't even dream about.
To the poster who mentioned Mattituck and not being able to use avgas with EI on one side even on a relatively low compression engine - could someone explain why this is so? What about dual EI?
Thanks

captain_john · Post by **captain_john** » Thu Jul 19, 2007 12:03 am

Hmmmm, engine group buys, huh?

Mahlon and I are on good terms!

I have eaten lunch there at least a couple of times!

Mebbe a possibility!!!

CJ

Post by **Spike** » Thu Jul 19, 2007 7:56 am

captain_john wrote:Hmmmm, engine group buys, huh?

That might get my attention.

cjensen · Post by **cjensen** » Thu Jul 19, 2007 8:45 am

cnpeters wrote:To the poster who mentioned Mattituck and not being able to use avgas with EI on one side even on a relatively low compression engine - could someone explain why this is so? What about dual EI?
Thanks

First, I'm assuming you meant auto fuel and EI...

I think it was Tom that mentioned this, and I've had similar conversations with Mahlon about this. Mattituck, nor any other engine shop/builder, won't recommend Mogas with EI because it advances the timing, and has a STRONG potential for detonation, and destroying an engine. People may be doing it, but they risk failure.

So, even with low compressions, if you use EI and Mogas, it will probably void your warranty if work is needed as a result.

Kinda sucks since EI typically improves flows and power, but Avgas is pretty much required. Buy EI for cheaper flying, and you still have to buy the gold gas.

hngrflyr · Post by **hngrflyr** » Thu Jul 19, 2007 10:15 am

Speaking of fuel burn in 0-320s and 0-360s, A friend of mine has a T-18 with a 0-360. I have a RV-6 with a 0-320. When going cross country together, our speeds are very near the same, and our fuel burns are identical. For my money, the 0-360 is a better choice. The power is there if you want it, but you don't have to use it if you don't want to. Another friend has a RV-6 with a 0-360 and a constant speed prop. He cruises around at 145 kts or so and uses just over 7 gph. My 0-320 has never achieved the fuel economy others report. I don't have a fuel flow meter. I just go by the clock and how much gas I've used at the end of the day. The price of fuel is seriously cutting into the amount of flying I do anymore. I'm retired and on fixed income. For local flying, I've been using premium auto fuel with good results. I try to keep about half 100LL in the tanks to get the benefit of the lead. I got detonation one time from regular auto fuel. I won't use it again. A reduction of manifold pressure stopped the detonation.

Bob Severns
RV-6
Eugene, Oregon

cjensen · Post by **cjensen** » Thu Jul 19, 2007 11:26 am

What are your fuel burns like Bob? What ignition do you have?

hngrflyr · Post by **hngrflyr** » Thu Jul 19, 2007 6:35 pm

My 0-320 averages 9.2 gph at what seems to be about 70%. I have a pair of Slick Mags firing the plugs. The timing is dead on the money.

Bob Severns
RV-6
Eugene, Oregon

captain_john · Post by **captain_john** » Thu Jul 19, 2007 9:03 pm

HOLY COW, Bob!

I didn't know a 320 could drink that much!

Are you using tach time or Hobbs?

CJ

cnpeters · Post by **cnpeters** » Thu Jul 19, 2007 9:15 pm

cjensen wrote: First, I'm assuming you meant auto fuel and EI... I think it was Tom that mentioned this, and I've had similar conversations with Mahlon about this. Mattituck, nor any other engine shop/builder, won't recommend Mogas with EI because it advances the timing, and has a STRONG potential for detonation, and destroying an engine. People may be doing it, but they risk failure.

Thanks for the clarification. And oops, I did mean mogas. But is it possible to not advance the ignition so one could use mogas, or does this rob some of the efficiency of the EI (yeah, yeah - newbie EI questions, as I haven't begun to research this yet

)? From an economics point of view, the dollars go further with mogas at a 20% reduction in cost/gallon vs avgas contrasting the 3% or so efficiency in fuel burn I have seen quoted for EI vs mags.
Here is a quote from Mattituck's website:

Can the TMX Series of engines be operated on automotive fuel?

Yes, all of the TMX experimental series of engines, that use compression ratios below and including 8.5:1, can be operated on fresh automotive fuel that meets spec ASTM D-4814 and has a minimum 91 octane rating. The use of automotive fuel that is blended with ethanol or alcohol is not permitted. Engines that have been modified to use higher than standard compression ratio pistons or that are using electronic ignition that advances the ignition timing past standard specifications are not recommended to use mogas. Although the use of 91 octane automotive fuel will work in these engines, that practice should be limited and isn't endorsed.

There is a hint that there may be EI's that don't advance timing, or are some adjustable? Frankly, I'll probably stick with my plans for EI one side, use avgas, and probably fuel injection to gain from LOP operation. I'm not sure I've seen mogas at a single airport, and to cart 40 gallons of mogas to the airport is not appealing either (and probably not legal without some expensive tank, plus likely frowned on to store extra in a rented hangar).

Thanks.

hngrflyr · Post by **hngrflyr** » Thu Jul 19, 2007 10:50 pm

I start the clock at the beginning of the take off run and end it at shut down. I just had the manifold pressure guage rebuilt. The engine turns a two blade Catto Propeller. Going cross country, I use 23" . It turns 2450 to 2500 RPM. It gives me 153 KTS, TAS. At WOT, the airplane will go 165 KTS TAS, Just what Vans says it should do. There are a few things I could do to clean the airplane up a little. Maybe this winter. Little things make a difference. One time, I lost the wire that holds the bottom of the cowl streamline with the fuselage. It cost me 3 KTS at cruise.

I purchased my RV-6 about 3 1/2 years ago. It first flew in 1995.

Bob Severns
RV-6
Eugene, Oregon

N258RE · Post by **N258RE** » Fri Jul 20, 2007 4:50 am

cnpeters wrote:
Can the TMX Series of engines be operated on automotive fuel?

Yes, all of the TMX experimental series of engines, that use compression ratios below and including 8.5:1, can be operated on fresh automotive fuel that meets spec ASTM D-4814 and has a minimum 91 octane rating. The use of automotive fuel that is blended with ethanol or alcohol is not permitted. Engines that have been modified to use higher than standard compression ratio pistons or that are using electronic ignition that advances the ignition timing past standard specifications are not recommended to use mogas. Although the use of 91 octane automotive fuel will work in these engines, that practice should be limited and isn't endorsed.

hmmm 91 octane with no ethanol,that would mean premium unleaded,

that actually cost MORE a gallon than avgas here

smithhb · Post by **smithhb** » Fri Jul 20, 2007 7:00 am

N258RE wrote:hmmm 91 octane with no ethanol,that would mean premium unleaded, that actually cost MORE a gallon than avgas here

If so, you are seeing an anomaly. Avweb tracks the median pricing of avgas nationwide and it is floating around $4.50. In my area (N. Georgia) I see it from 3.99 to as high as $5.59.

Mogas is 3.09-3.15 (this week)...