I think I have uneven airflow....

[DanH]

Originally Posted by rv6ejguy

Just looking at the transducer signal in the runner and the 3 "shadow" pulses from the other 3 cylinders for a difference in waveform and amplitude.

Got it. Good stuff and certainly valuable, but doesn't address the concept I was trying to communicate.

Here's an expanded example. Assume three intake tubes, one with a 90 degree bend, one with a 45 degree bend, and one straight. Attach a pressure tap to each (like where one might place an injector), here just above the bends in the first two. Run the same air velocity and density through all three, and consider the flow at the bends. Think you'll get the same pressure reading for each, or three different local pressures at the tap points?

Originally Posted by rcpaisley

There are two reasons why we point the injectors the way we do.
It prevents fuel rail vapor bubbles from getting trapped at the injector valves after shutdown and it provides more energy to the fuel spray during operation.

Robert, could you please expand on "provides more energy to the fuel spray"?

You have to keep in mind that these are 1/2hp per cu in engines. Air flow velocities are low.

Hmm. Runner velocity is not a function of HP. For Clark's 370 at 2700 RPM, velocity would be about 221 feet per second (150 mph) assuming a 2" diameter intake runner and 100% VE. It would be about 394 FPS (268 mph) for a 1.5" diameter runner.

[brad walton]

Perhaps more shear by facing the injector into the airflow? More shear might better atomize.

[BillL]

Originally Posted by brad walton

Perhaps more shear by facing the injector into the airflow? More shear might better atomize.

Nope, atomization is effected by the velocity/pressure of the streams departing the orifices in the injector. Evaporation of the droplets takes place as they hurtle through the airstream, looking like little comets with streaming vapor behind them.

It might provide improved evaporation in the greater upstream volume of the intake tube during the period of the closed intake valve, but may impact the tube wall at that angle. Only a lot of money and time on multiphase CFD modeling or a bunch of test work (and luck) can tell what works best.

[jclark]

Originally Posted by rv6ejguy

Interesting data. I'd usually expect the EGT spread to be less with the same engine/manifold using fuel injection of any sort since you are flowing dry air and not wet charge.

My take on this is that some combinations are better than others and that heads and manifolds together may create imbalances in mixture distribution. The Titan heads may be more closely matched in flow than Lycoming ones as we often see much larger spreads on other updraft examples- 170-200F with carbs and with EFI, still pretty large spreads where we're pretty sure injector flow rates are near equal since we've swapped injectors over to the other bank with little change.

The combination you are testing clearly works pretty well.

I welcome more test data and especially from anyone using a Sky Dynamics intake. I hope on a future project we may be involved with to get some dyno numbers on that combination. Always interesting...

Just another bit of info.

This is my plane/engine.

I worked with ECI using a variety of mods to the "standard" experimental carb for the 340 and a Van's O-320 airbox setup. The WORST CASE scenario had an EGT spread of almost 300 degrees!

ECI worked with me on various mods (using the constraint that it all had to fit in the O320 space with NO CHANGE to the older O-320 cowl that doesn't have enough space for an O-360 carb and airbox). We (ECI and I) decided to shift the effort to finding a fuel injected solution.

Since I know Don and he is nearby, I wanted to work with him on the answer (with ECI's support in finding a solution).

Over the last several weeks, Don and his team has been evolving the new design. I hope to visit again this week to do some more test flying followed by the testing of a further improved design.

It has been great working with them and I am looking forward to a much improved system (soon!). We will report the "improvements" here.

The 340 PULLS STRONG!!!!!

James

[RVbySDI]

Originally Posted by jclark

The 340 PULLS STRONG!!!!!

YES, IT DOES!!!!

[carrollcw]

So, the numbers are in. I replaced my ECI updraft sump with the superior updraft sump. Unfortunately the numbers did not improve as much as I hoped. Here are the numbers from my test flight climbing to 8500':

ROP CLIMB

EGT's - 1220,1080,1215,1070
CHT's - 386,372,365,359

LOP CRUISE

EGT's - 1195,1260,1190,1280
CHT's - 352,397,334,384
GAMI - 1.2

So, the numbers are a little tighter and GAMI went down a little, but not enough to justify the money I spent on the new sump. Oh well. So, I need to look elsewhere to figure out the uneven airflow.

[Weasel]

Thanks for taking the time to up date us on this!!!!!!

[rv6ejguy]

Originally Posted by carrollcw

So, the numbers are in. I replaced my ECI updraft sump with the superior updraft sump. Unfortunately the numbers did not improve as much as I hoped. Here are the numbers from my test flight climbing to 8500':

ROP CLIMB

EGT's - 1220,1080,1215,1070
CHT's - 386,372,365,359

LOP CRUISE

EGT's - 1195,1260,1190,1280
CHT's - 352,397,334,384
GAMI - 1.2

So, the numbers are a little tighter and GAMI went down a little, but not enough to justify the money I spent on the new sump. Oh well. So, I need to look elsewhere to figure out the uneven airflow.

Do you have photos of the two sumps internally or any idea in the differences in plenum volume where the tubes all merge to?

[lr172]

Originally Posted by DanH

That's pretty much it.

It's a pulse width modulated constant flow system, not a sequential injection system. All injectors open and close at the same time, and they are all supplied at the same fuel pressure, so all cylinders get the same fuel delivery, or better said, the same within the flow tolerance of the injectors. There is no way to modify fuel flow to any particular cylinder, so an owner is left with trying to modify the air delivery, or living with a huge GAMI spread.



A year and a half of heavily promoted Titan partnership, and nobody saw this on the dyno?

Most non-sequential systems have two "banks" and each bank is triggered from a differnt circuit. Most systems use a common open time for both banks, but I suspect some may allow variability in the open time for each bank. While difficult to set up, you could split the fuel feed into two circuits with independent regulators and use different pressures in each. With a common open time, it is not difficult to regulate total flow via fuel pressure. Set them them both at the designed pressure and slowly increase pressure in the lean bank until it evens out. Varying FP used to be a typical method of increasing fuel flow based upon vacuum in the early FI systems

Larry

[carrollcw]

Originally Posted by rv6ejguy

Do you have photos of the two sumps internally or any idea in the differences in plenum volume where the tubes all merge to?

The superior sump's plenum appears to be more smoothed and polished than the ECI one, but besides that, hard to tell any difference.