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EFII - the jury is coming in

Tom Martin said:
...But what I do get with that loss of speed, is 5% MORE engine tach hours because I am in the air longer.
That is 5% more of more wear and tear on the engine. If one gets 2000 hours on an engine, then running LOP will meant that you get there 100 hours sooner then if you were running at best power...!
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Do they have mandatory TBO limits up in the GWN? Because if they don't then your example has a significant flaw... There is very little wear taking place in an engine operated in thermally stable cruise condition. Compared to throttle (thermal) transients, and engine starts, cruise operation is as close to eternal life as a piston engine gets. Start any Lycoming, run it at maximum continouus power while feeding it clean oil and ample cooling air, and it will likely run past published TBO several times over.
 
Been looking around the 'net a bit for what's out there regarding proper Lycoming intake manifolds after recently looking at the stock induction layouts and inside the stock sumps which are very poorly designed in my view. No wonder people are seeing huge EGT spreads on many of these engines. They look like something off a farm tractor.

Anyway, a few choices out there but I like these the best as they follow automotive practice closer- large plenum, near equal length tubes which are tapered and the tubes don't enter the plenum at crazy angles: http://www.skydynamics.com/index.php/products/sump/intake

These would go a long way towards solving the "four 1 cylinder engines flying in close formation" syndrome and would be a boon to EFI users.
 
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Another choice is from Barrett Precision Engines. It appears to be a similar design as some of the others.


UOTE=rv6ejguy;992649]Been looking around the 'net a bit for what's out there regarding proper Lycoming intake manifolds after recently looking at the stock induction layouts and inside the stock sumps which are very poorly designed in my view. No wonder people are seeing huge EGT spreads on many of these engines. They look like something off a farm tractor.

Anyway, a few choices out there but I like these the best as they follow automotive practice closer- large plenum, near equal length tubes which are tapered and the tubes don't enter the plenum at crazy angles: http://www.skydynamics.com/index.php/products/sump/intake

These would go a long way towards solving the "four 1 cylinder engines flying in close formation" syndrome and would be a boon to EFI users.[/QUOTE]
 
Let's remember that aftermarket manifolds are typically used with conventional constant flow injection, and the owners still do the usual nozzle tuning if they want to run lean (the WOT guys don't care). There's no evidence that nozzle tuning is eliminated with the addition of an aftermarket manifold.

The only way to determine equal air delivery would be to set up a cylinder on a flow bench, and measure flow through each tube in turn. Even that method has issues.

In any case, it's a huge assumption to claim failure to reach peak EGT in concert is a manifold fault. Look at all the other factors. For example, how much variation is typical if we flow bench a dozen cylinders in turn?

Here's an interesting comparison. Most of us would agree that the under-the-head log manifold on older big bore Continentals is pretty awful. Data here....

http://www.nar-associates.com/technical-flying/Vibration/Vibnet_wide_screen.pdf

...says the peak EGT spread measured about 1.5 GPH for a stock IO-520 at 2300 RPM...about the same spread than Jesse reported here.

Do you really think any horizontal intake manifold for a Lycoming (stock IO-360/390 below) could be as bad as an early Continental log manifold? If so, which one?



Now, returning to a previous question..

Thank you Chris. Could you (or Jesse) tell us which engine model and intake manifold system is installed on this airplane?
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The 4 cylinder O-200 is known to be terrible as we've done numerous EFI systems on them, most having had a new manifold constructed to replace the OEM one. On these, people reported 20%+ lower FF for the same TAS!

The O-320 one I looked at was truly terrible.

On the Conti 550/EFI, stock intake (decent design IMO) we saw pretty narrow EGT and FF spreads at peak. Flow benched cylinders here too.

As I said previously, a proper intake, combined with flow matched heads and injectors should narrow cylinder to cylinder AFR differences considerably thus removing most of the problem. This is how the automotive world works, should be no different here.

I'd bet a beer that the Sky Dynamics setup works a LOT better than the OEM Lycoming stuff I was looking at last week.
 
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rv6ejguy said:
The 4 cylinder O-200 is known to be terrible as we've done numerous EFI systems on them, most having had a new manifold constructed to replace the OEM one. On these, people reported 20%+ lower FF for the same TAS!

The O-320 one I looked at was truly terrible.
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Foul ball ;) Those are updraft manifolds with carburetors. Even the worst port fuel injection would be vastly superior to the carb, because it moves the introduction of fuel to the port and reduces the mixture distribution problem.

Air distribution should be better with any of the available horizontal manifolds, just because the updraft sump Lycoming carb manifold appears to be such a mess in the plenum area. That's why I keep asking about the 540 manifold in the previous posts...updraft or horizontal, stock Lyc or aftermarket?

As I said previously, a proper intake, (decent design IMO) combined with flow matched heads and injectors should narrow cylinder to cylinder AFR differences considerably thus removing most of the problem. This is how the automotive world works, should be no different here.
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Agreed.
 
DanH said:
Foul ball ;) Those are updraft manifolds with carburetors. Even the worst port fuel injection would be vastly superior to the carb, because it moves the introduction of fuel to the port and reduces the mixture distribution problem.

Air distribution should be better with any of the available horizontal manifolds, just because the updraft sump Lycoming carb manifold appears to be such a mess in the plenum area. That's why I keep asking about the 540 manifold in the previous posts...updraft or horizontal, stock Lyc or aftermarket?

Agreed.
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Yes, the port EFI helps mixture distribution usually even with a bad manifold design because only dry air flows around the corners with EFI, avoiding some of the inertia effects of wet mixture.

The port EFI alone got O-200 folks about 15% lower FFs at same TAS, redoing the manifold gave them up to 10% more. Yes, 25% better than the carb. That's how bad these are. We see FFs drop about 25-30% on the Jabiru 3300s with EFI and no manifold changes. These have a dog's breakfast for an intake design as well. It's not uncommon to see EGT spreads of 180F+ on these with the carb. One fellow saw 230F. With the EFI they can run LOP and still make the same power as the carb running well ROP.

Even the Rotax 912 with twin carbs has one cylinder quite different from the rest. Using EFI and the stock intake casting attached to a new single plenum/ single butterfly, totally clears up the problem resulting in more power, lower FF and better smoothness.
 
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