Van's Air Force
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IO 180 HP vs Carborated 180 HP
- Thread starter Ned R
- Start date
Norman CYYJ
Well Known Member
Both engines have their pros and cons. You will probably get about as many opinions about which engine to use as you would if you asked should I build a tail wheeled or nose wheel plane, or to prime or not to prime.
Both engines will do a fine job of pulling your bird through the sky. But if were you I would definitely go for a .............engine.
Both engines will do a fine job of pulling your bird through the sky. But if were you I would definitely go for a .............engine.
osxuser
Well Known Member
Carb:
Cheaper (for now)
Icing
Less balanced mixture = more fuel burned
FI
No ice
Can run LOP
Fwd facing can get a bit more HP
Bill Wightman
Well Known Member
I prefer injection...
... for several reasons:
1. Better fuel metering to each cylinder
2. Ability to operate lean of peak, if desired (with flow balanced jugs)
3. Not restricted to updraft induction
4. No induction icing problems
5. Cleaner cowl appearance (no snoot on cowl bottom)
6. More induction system design possiblities (locate the servo on front of sump, for instance)
7. System is not attitude sensitive
Drawbacks to FI
1. More expensive components - servo, fuel pump, flow divider, lines, nozzles, etc.
2. Usually harder to start when hot
Either way will yield a dependable engine, but the main advantage to FI in my opinion is the superior fuel metering.
My old RV4 had a 200HP O360 that was converted to injection. Coupled with flowed cylinders and a Light Speed ignition system that advanced the spark to about 38 degrees at 12500 MSL, I routinely saw fuel flows around 7.2 to 7.3 gph at about 50F lean of peak. The engine was totally smooth across the entire range of mixtures right up to cut-off. I don't think you could approach these numbers with a carbureted engine.
... for several reasons:
1. Better fuel metering to each cylinder
2. Ability to operate lean of peak, if desired (with flow balanced jugs)
3. Not restricted to updraft induction
4. No induction icing problems
5. Cleaner cowl appearance (no snoot on cowl bottom)
6. More induction system design possiblities (locate the servo on front of sump, for instance)
7. System is not attitude sensitive
Drawbacks to FI
1. More expensive components - servo, fuel pump, flow divider, lines, nozzles, etc.
2. Usually harder to start when hot
Either way will yield a dependable engine, but the main advantage to FI in my opinion is the superior fuel metering.
My old RV4 had a 200HP O360 that was converted to injection. Coupled with flowed cylinders and a Light Speed ignition system that advanced the spark to about 38 degrees at 12500 MSL, I routinely saw fuel flows around 7.2 to 7.3 gph at about 50F lean of peak. The engine was totally smooth across the entire range of mixtures right up to cut-off. I don't think you could approach these numbers with a carbureted engine.
All the points above are correct, but they will apply differently to each of us. I chose CARB because it was simple, this was my first build, and it was a little cheaper. It's almost bulletproof and I was not confident with the FI system. I was very reluctant to go FI based on my exisiting experience level.
After listening to all the pros and cons, I just wanted something that would always work, wasn't picky about fuel, easy to maintain, etc. That just means carb to me because I understand them.
Now after going through the build, installing and wiring the panel and engine, and many hours of list research, ... I would do the FI without question. The problem with building is that your confidence level and personal experience affects some of your choices and both change during the build. Wish I had gone FI but don't regret the carb decision.
Just a little .02 not related to the technical side.
Bill S
7a Ark
After listening to all the pros and cons, I just wanted something that would always work, wasn't picky about fuel, easy to maintain, etc. That just means carb to me because I understand them.
Now after going through the build, installing and wiring the panel and engine, and many hours of list research, ... I would do the FI without question. The problem with building is that your confidence level and personal experience affects some of your choices and both change during the build. Wish I had gone FI but don't regret the carb decision.
Just a little .02 not related to the technical side.
Bill S
7a Ark
Walt
Well Known Member
I got a carb and don't regret it a bit. The carb is simple, reliable and easily repaired if needed. I run LOP on every flight so balanced injection is not required for this. I do run dual light speed ignition but also ran LOP with just one LSI. One thing I also like about it is the low pressure fuel system, no high pressure pump in the cockpit (which I never really liked that idea but I know it works ok). And as for ice maybe if you live up north or fly IFR that may be an issue but I've never used carb heat except to check to see if it still works during my annual 
IO 180 HP vs Carborated 180 hp
Thanks gentlemen for you comments. Seems that everyone just about says the same thing. I do plan on flying IFR when I have to, IE: takeoff and landing and any clouds that get in the way going from A to B on some trips, but obviously nothing heavy. Lots of VFR flying too. I really appreciate your time and thoughts for your inputs.
Ned
RV-7A Planning Stage
Thanks gentlemen for you comments. Seems that everyone just about says the same thing. I do plan on flying IFR when I have to, IE: takeoff and landing and any clouds that get in the way going from A to B on some trips, but obviously nothing heavy. Lots of VFR flying too. I really appreciate your time and thoughts for your inputs.
Ned
RV-7A Planning Stage
Mark Castle-Smith
Member
FADEC Option
I thought I would just throw my 10p (sorry 10c!) into the mix. We went for injection for our RV7 for many of the reasons articulated above and decided on the Aerosance FADEC system. Yes it is more expensive, but not as much as people seem to think when you take away the costs of magnetos etc. I cannot believe how smooth the engine is, no mixture to worry about, always starts within a blade or two, cold or hot, automatically balances the cylinder temperatures etc etc I would recommend you think about this system amongst the many options if you decided to go FI. Whatever you go for - good luck!
Mark Castle-Smith
Finished the RV7: Starting an RV3!
I thought I would just throw my 10p (sorry 10c!) into the mix. We went for injection for our RV7 for many of the reasons articulated above and decided on the Aerosance FADEC system. Yes it is more expensive, but not as much as people seem to think when you take away the costs of magnetos etc. I cannot believe how smooth the engine is, no mixture to worry about, always starts within a blade or two, cold or hot, automatically balances the cylinder temperatures etc etc I would recommend you think about this system amongst the many options if you decided to go FI. Whatever you go for - good luck!
Mark Castle-Smith
Finished the RV7: Starting an RV3!
frankh
Well Known Member
FI hot starts
If you use the Airflow performance purge valve (and flow divider)...Which can be used with a Bendix servo I understand ...Then hot starts are a non issue.
My hot starts are the same as cold starts after a 10 second or so purge.
Some Carb'd engines can run LOP but it is unusual to have decent enough balancing to achieve this.
Frank
If you use the Airflow performance purge valve (and flow divider)...Which can be used with a Bendix servo I understand ...Then hot starts are a non issue.
My hot starts are the same as cold starts after a 10 second or so purge.
Some Carb'd engines can run LOP but it is unusual to have decent enough balancing to achieve this.
Frank
Jamie
Well Known Member
I have now flown my Superior XP-360 with Precision Airmotive Silverhawk Ex injection through a summer and never, ever even once had a hard time hot starting it -- and this is in the Georgia heat. Crack the throttle, mixture lean, engage starter, wait for it to kick, mixture full rich. Works every time. I have dual impulse coupled mags.
I know that in FI Cessnas I always had a hard time hot starting them but for my RV it's no big deal at all. I think the hot start issue is overblown with FI.
Me? Deal clincher for me was carb ice...you hear so many conflicting things I just decided to avoid the issue entirely.
Just my 2 cents.
I know that in FI Cessnas I always had a hard time hot starting them but for my RV it's no big deal at all. I think the hot start issue is overblown with FI.
Me? Deal clincher for me was carb ice...you hear so many conflicting things I just decided to avoid the issue entirely.
Just my 2 cents.
IO 180 hp vs carborated 180 hp
Mark, Frank and Jamie,
Thanks! Ah, more info to stir around with. The one thing I don't want to have to worry about is ice also if in IFR wx. I lean towards the Injected, but like the simplicity of the carborator. I was also given the impression from someone who has helped build many RV's, that the FI was more difficult to install. He implied to me that there were extra fuel tubing that had to be installed in the floorboard in front of the seats. Would this be fuel pumps and lines that are not required with the carb?
Ned
Planning RV-7A
Mark, Frank and Jamie,
Thanks! Ah, more info to stir around with. The one thing I don't want to have to worry about is ice also if in IFR wx. I lean towards the Injected, but like the simplicity of the carborator. I was also given the impression from someone who has helped build many RV's, that the FI was more difficult to install. He implied to me that there were extra fuel tubing that had to be installed in the floorboard in front of the seats. Would this be fuel pumps and lines that are not required with the carb?
Ned
Planning RV-7A
Some injected engines require fuel return line which indeed is more work and usually more expensive (especially in form of fuel valve). However not all injected engines seem to require such a line at least not back to the tank.
I guess search with "fuel return line" for the forum might reveal brands of engines which would require that feature.
I have several hours behind both types and each performed well. The only thing that may swing me to the carburated type might be the situation with 100LL. An A&P told me that it would be much easier to convert a carburated engine over to automotive fuel than an injected. I'm not sure how much more of a challenge it would be to convert the injected engines than it would the carburated.
I will research this point before purchasing my engine. I like the performance of the IO but my pocketbook prefers the O.
I will research this point before purchasing my engine. I like the performance of the IO but my pocketbook prefers the O.
frankh
Well Known Member
Untrue
I know for a fact the AFP system is completly compatible with mogas...its even compatible with 100% Ethanol of a mixture therof.
I know of several Bendix systems that are flown with mogas ( I don't know if they are compatible with Ethanol or not, but I bet they are).
But saying that FI is somehow more difficult to convert is not true...Fill it with mogas and go fly, its as hard as filling the tank.
Besides which FI is more conjucive to the savings with running LOP.
Frank
I know for a fact the AFP system is completly compatible with mogas...its even compatible with 100% Ethanol of a mixture therof.
I know of several Bendix systems that are flown with mogas ( I don't know if they are compatible with Ethanol or not, but I bet they are).
But saying that FI is somehow more difficult to convert is not true...Fill it with mogas and go fly, its as hard as filling the tank.
Besides which FI is more conjucive to the savings with running LOP.
Frank
I have a Superior IO-360 parallel valve engine with updraft PA Silverhawk injection. Superior rates my engine as suitable for auto fuel. So it's yet another "that depends" issue. When I bought the engine the price hit to go injected instead of carbureted was only a couple of hundred dollars. But then I still need to buy the much more expensive high pressure fuel pump assembly which isn't needed with a carb. The fuel pump should handle auto fuel, since the same pumps are used in automotive fuel injection systems.
Another issue if buying a new engine is the questionable availability of carburetors and the fact that they've gone up a bit in price.
On the other hand if one finds a complete used carbureted engine to overhaul, that would likely be a fair bit cheaper than what I paid, and in that case the cost hit to add fuel injection would probably make it unattractive. Which is to say I'm not making a case for or against. I wanted fuel injection, so that's what I bought
Ned:
The IO electric pump and filter are in the cockpit and are more difficult to build and service. The carb has a single fuel line that goes from the fuel selector to the facet pump on the F/W. The IO filter/pump assembly has a menagerie of tubing that reminds me of a trumpet stuck down there. Modifying the center cover and installing the filter/pump assembly may take you several extra evenings over the carb. Forward of the F/W is not that much more difficult to build. There is an extra fuel hose on the IO, 2 if you use a return line. Also you may need to add a sniffle valve and drain line.
All together, it may add a full weekend to your build time, more weight and cost and then there are the benefits......
Jekyll
IO vs carb 180 hp
It's my understanding that one could only use auto gas in a low compression engine and not a high compression engine. I'm not sure how to really tell the difference. I seem to remember that the Continental 0-470 230 hp was low compression and could get an STC for auto gas, but the Lycombing 235 hp was high compression and could not.
Ned
RV-7A Planning
It's my understanding that one could only use auto gas in a low compression engine and not a high compression engine. I'm not sure how to really tell the difference. I seem to remember that the Continental 0-470 230 hp was low compression and could get an STC for auto gas, but the Lycombing 235 hp was high compression and could not.
Ned
RV-7A Planning
IO vs Carb 180 hp
I remember seeing all that plumbing on the floor of the cockpit. I think I was also told that because it was on a 7A, that the nose strut gets in the way of some of the plumbing. But I'm not sure exactly the problem or why its a problem unless it's space.
Ned
RV-7A Planning
I remember seeing all that plumbing on the floor of the cockpit. I think I was also told that because it was on a 7A, that the nose strut gets in the way of some of the plumbing. But I'm not sure exactly the problem or why its a problem unless it's space.
Ned
RV-7A Planning
All the benefits mentioned by previous posters.
I can't tell you why Van's designed the filter/pump the way they did so I won't consult the tea leaves. I can only comment on the implications to the builder.
Compare Fire Wall Forward kit prices and engine prices on the Vans web site to determine the price delta. I don't recall if the filter/pump is part of the FWF kit or if you must buy it seperately.
Jekyll
Pump/filter is separate, at least for FI. Just shy of $600, last time I checked. For updraft fuel injection, Van's told me they recommend the O-360 carb firewall forward kit.
Mike Harris
Member
Carb versus FI
Auto gas is reliant on compression ratio. Most engine facilities will have a chart on which engine will run on auto gas. Look online. The important thing is the type of additives and the type of seals used in your injection system.
Auto gas is reliant on compression ratio. Most engine facilities will have a chart on which engine will run on auto gas. Look online. The important thing is the type of additives and the type of seals used in your injection system.
