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Mechanical vs electronic fuel injection data

j-cub

I'm New Here
I know there's a lot of info out there on this topic, but for the life of me I can't find any dyno comparisons between any of the common fuel injection kits. The closest I got was a email from Robert claiming 195hp on a System32. Does the data just not exist? Or is it hiding somewhere? In particular I'm trying to see if the electronic systems have any substantial performance benefits over the mechanical systems.
 
Fuel injection

To get power out of an engine it need as much air as possible.
Then you can supply the fuel at the right mixture to get the power.
There would be no difference in power between mecanichal or electronic fuel injection other than fuel consumption or emmisions I think.
I have an IO-360 with mecanical fuel injection, no electronics or data update to worry about.

Good luck
 
Agreed. The engine makes power by turning fuel into heat. Assuming each cylinder is seeing the optimum mixture, there is no "substantial" gains to be had with the method of fuel delivery. The rub, however, is the assumption that each cylinder is seeing the correct mixture. This is where mechanical FI is generally superior to a carb. The mechanical FI often takes some tuning (via swapping out nozzle restrictors) to get to the optimum balance, but once there, its pretty good. The down side of mechanical injection is that the tuning is often laborious, and really only optimizes the cruise condition. SDS EFI brought us the ability to trim each injector in flight, and because the injectors do not rely on port airflow to optimize the flow pattern of the injector, their performance is stable across the board from 100% power to idle.

EFI gets you stable operation across the board and very simple trimming of individual cylinders. That optimization is likely to buy most people a little bit of power compared to the legacy setups, but beware of someone selling "substantial" gains.
 
EFI gets you stable operation across the board and very simple trimming of individual cylinders. That optimization is likely to buy most people a little bit of power compared to the legacy setups, but beware of someone selling "substantial" gains.

+1

EFII is unlikely to deliver ANY measurable performance gains over a well optimized mech FI and with well optimized EI. I agree there are other benefits to EFII, but an additional 15 HP is not one of them. If the seller is saying that the simple addition of his EFII will do 180 -> 195, you should question his ethics.
 
Optimal fuel droplet size has been shown to make a few more hp with both carbs and EFI. The most I've seen came from dyno tests from a friend who has built multiple SCCA championship winning Nissans. He saw just over 2% by going to different injectors and higher fuel pressure. Too small on droplet size and you lose hp, too large also. I might expect lower gains on a slow revving engine like a Lycoming but don't know that for sure. The droplet size affects combustion speed and how heat is released. You'll see many SAE papers on this, mainly to do with emissions.

On 540 engines with vertical induction the EFI throttle bodies have lower pressure drop than the carb or RSA-5 servos, this allows more airflow, hence more power.

The RSA-5 servo doesn't present much restriction to a 360 though so gains are lower there. There appears to be no drop in MAP on 360s with our std 60mm TB. You can see what you have now for MAP, fly to sea level and go to WOT. You may have some extra pressure from prop inflow but if you only get 29 inches, that would be about 3% loss. The carb will usually show somewhat higher loss than this due to the venturi restriction.

On 540s with horizontal induction and the RSA-10 servo, pressure drop is minimal so I'd expect to see even less hp gain there with EFI. We use an 80mm TB on this application. Anything past about 2/3rd to 3/4 throttle shows no gain in MAP.

Realistically on a 360, I'd expect to see no more than about 6hp gain with EFI over a good RSA-5 or AFP setup with matched nozzles.

If someone can produce a back to back dyno test on the same engine with mechanical injection and then EFI, those would be interesting results.

I'm doubtful you'd see 15 hp on a 360 but welcome to be proved wrong.

When testing engines or many others things, you should use the scientific method- change only one variable, repeat and observe. Too many people will build a new engine, port the heads, change the exhaust, raise the compression, change the manifold and add EFI, then attribute all the power increases to the EFI. Not realistic conclusions.

Of interest, when we ran a Rotax 912 on our test stand with a club (known power absorption curve), we saw a 3-5 hp gain with the EFI. This was using the original Bing carbs as throttle bodies for expediency but it also removed any variable using different throttle bodies. The 912 is known to have unequal fuel distribution with the carbs. The EFI, even without individual fuel trim in that era, showed a much closer EGT grouping at WOT compared to the carbs. We had a wideband on the engine and tried to bracket the EFI AFRs where the carbs had been running.
 
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Well, I know of one direct comparison, same engine, same dyno, same day...but back when I wrote it, the bitchin' from some quarters would have you thinking I had pissed on the flag ;)

https://www.danhorton.net/Articles/Fuel and Fire.pdf

As you concluded in the end, the effect of recirculated fuel into the pump inlet was unknown. That's something we never recommend.

But I wouldn't expect any big gains compared to the RSA-10 hardware even when everything is right.
 
We (gearheads, in general) have become so accustomed to the magazine articles where a subject engine is thrashed on the dyno with all kinds of same day changes -carbs, cams, intake, exhaust, etc- that we just expect the same in THIS industry. We could really use it, but most of the times these changes are accompanied with many others, so its hard to nail down the true reason for the performance change.

I'm in the same boat - I had a factory new 260 HP 540 rebuilt by LyCon and run across their dyno. The only changes made were ported heads and the SDS EFI. On that dyno, the resulting engine made 330+ HP. Even if we accept the porting work at the claimed 5 HP per cylinder, that still attributes 40+ HP to the EFI (compared to the nominal 260 data plate number). That just does not pass the sniff test, but the new engine is stronger than it was before in side by side flight test with other buddies. But not 70 HP.

Would be nice if there was a true dyno mule engine and test stand to work all this stuff out.
 
I'm in the same boat - I had a factory new 260 HP 540 rebuilt by LyCon and run across their dyno. The only changes made were ported heads and the SDS EFI. On that dyno, the resulting engine made 330+ HP. Even if we accept the porting work at the claimed 5 HP per cylinder, that still attributes 40+ HP to the EFI (compared to the nominal 260 data plate number). That just does not pass the sniff test, but the new engine is stronger than it was before in side by side flight test with other buddies. But not 70 HP.

This is why dyno numbers should be used like EGTs. Absolute numbers don't mean anything. You really can't compare shop 1 dyno to shop 2 dyno unless both have been installed, calibrated and corrected for identically, and I bet most dynos shops don't have them recalibrated every year. You can do before/after comparisons on the same dyno to see the increase/decrease of changes, but I would never believe a number that high without knowing what the motor made on it in stock form.
 
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Load cell, reaction type dynos are really easy to calibrate. You hang a test weight on the reaction arm and you know if it's accurate or not. You could do it with every new engine if you found the need.

2 foot reaction arm, hang a 100 pound weight on it and it should read 200 lb./ft.
 
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