Ok Ill reread it again have read a few times ... Is the spray distance pretty much the same ? using deatschwerks 42 lb an fast 92 have correct injector data in tune .Originally Posted by GHuggins
The above ^^^ is what this spreadsheet originated from
Unless you radically change the intake layout or the cylinder head design the time to combustion chamber should be close enough... You would need some pretty serious instruments to correctly calculate this because anything ranging from fuel pressure and injector location to port velocity will change it...
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
Ok thank you for the help didn't want to miss putting something in , I played with this year or so ago tried Bigmike42 an Eds suggestions then on old cam of moving the ect around up an down and monitoring the afr for rich lean changes at idle but didn't seem to get anywhere so put back to stock think I need to change it with this cam .
Greg -
He is refering to the user input cell; K14 (spray speed). I have been reviewing this thread trying to figure out what this value should be, or where I get it. There does not appear to be a definition or notes for this input. The most recent spreadsheet version, #19 for example, the owner has 24.5 m/s input to this cell. Where did he get that value?
When arguing with an idiot, make sure he isn't doing the same thing....
Page 6 / Post 105... I think the 25ms setting is just there because idle and lower rpms is where this is going to make the most difference?
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
Unless I'm interpreting the graph wrong, the 25 value would be degrees of rotation, not M/S. Milliseconds are at the bottom of the graph. Cells inside the graph are a rotational degree, no??
When arguing with an idiot, make sure he isn't doing the same thing....
Unless I'm also interpreting this wrong - your right... I should have looked at it closer the first time around... Looks like we need to be using something more around 2ms instead of 25ms?
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
I was actually thinking it would be a user input, or possibly a fixed input for each rpm cell. Assuming I am correctly interpreting the graph.
Is it m/s for meters a second? In other words, the rate of flow and not duration of time? If that's true, then we can assume it takes X number of crank degrees for fuel mixture in Y area at a rate of 24 meters a second to go Z distance injector to combustion chamber. That's how I understood it... but I never really fell in love with the FRC deal anyway. I'm looking at it as additional information rather than a variable of incredible importance.
When it comes down to it, none of us seem to be operating in an engineering lab environment. We're sometimes splitting hairs that have been previously split based on assumptions, moon phases, and the price of a pound of organically grown bananas from Mexico.
Well it does make a pretty significant impact moving it from 24 to 3. Moves mine about 40 crank degrees at 4096 rpm. So I'd say it's a pretty important variable.
When arguing with an idiot, make sure he isn't doing the same thing....
jsllc from Bozeman seems to suggest that the fuel mixture moves at a fairly constant speed. However, the movement itself, measured in crankshaft degrees, varies with engine rpm.
In other words, if the air/fuel mixture moves at X velocity through an opening with a given area no matter what, the piston will move more crankshaft degrees at higher rpms so that you still get the cylinder filled.
If is true, lowering it from 24 to anything violates the theory (the theory being that a mixture travels through an area of a specific size at a relatively constant speed when filling a cylinder). And if it is true, it seems the biggest factor affecting this variable (all other things considered) would be the distance from the fuel injector tip to the combustion chamber. If you move the injector closer to the plenum, for example, the FRC value goes up. If you move the injector closer to the intake valve centerline, the FRC value goes down.
That makes sense to me.
Maybe jsllc could clarify for us sometime.
I'm not disputing that. I'm disputing the value of 24.5 ms that somebody, sometime during these discussions, suggested it was the fuel speed value to be used. Greg suggests that value was detirmined from the graph that he posted a pic of, post #5. I will re-attach it. This graph, if you would take a look at it, shows milliseconds at the very bottem, and they the values range from 4.64 ms @ 512 rpm - to - 0.96 ms @ 8192 rpm. All the values in the Y/X axis of the graph, appear to me, to be crank degrees - not time. So therefor, the 24.5 value that someone suggested is not correct.
The end result after plugging all the values into the spreadsheet do not vary much at all if you plug a 0.9 into the fuel speed box, or a 5. But it does make a big difference going from 24.5 to 0.9.
FuelTT.jpg
When arguing with an idiot, make sure he isn't doing the same thing....
It is not milliseconds (ms) but meters per second (m/s) or if you prefer millimeters per millisecond as 1 meter per second equals 1 millimeter per millisecond. There is know way to be 100% accurate here as boost, runner length, density, ambient atmospheric pressure, temperature and other factors play into air velocity. Hence the input for the tool. if you know what it should be change it. It is a tool. I will argue that .9 means your engine is not running. You are right though just like every other input on this sheet they should be changed for what you believe to be correct. The main point was to show that it is more complex than just cam duration and engine rotational speed. For those that believe it is just a few numbers you might want to read this http://www.enginelabs.com/engine-tec...em-really-new/
There is a standard industry formula for calculating the peak intake port velocity on NA cars:
Bore area / Port cross sectional area x mean piston speed.
Mean piston speed = 2 x stroke x rpm
Make sure all units are the same (Convert Mean piston speed to M/sec)
Some engine guys use the mean port area by measuring port volume and dividing by port length. Many calculate it at the minimum cross sectional area of the port. For street engines, 100 M/S is a common target value at the rated power rpm. For racing engines, with very efficient ports, this can be pushed up to about 115 M/S.
You can use this same formula for the intake runners, for each cylinder substituting the runner area for the port area.
Hence the quote "There is no replacement for displacement!"
I will most likely modify the sheet to add engine speed to the air velocity when I get time and maybe some math for boost.
Last edited by jsllc; 05-22-2017 at 11:32 AM.
Oh..... Now it makes sense! That's why I originally asked for clarification......
When arguing with an idiot, make sure he isn't doing the same thing....
I talked with Jslic on the phone about this - basically it's just what he said - bigger numbers = faster port velocity / faster to cylinder speed - on the other side of the coin - lower numbers = slower port velocity = more time for fuel to reach cylinder...
He can clarify this more, but the 24 meters per second is roughly engine idle speed...
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
I like it when my assumptions (meters per second) are correct. Thanks jsllc.
I hope you weren't insulted when I wrote that I haven't fallen in love with the FRC stuff. I'm looking at it as additional information right now. I haven't played with it too much since I don't yet understand the factors influencing the variable. I wasn't suggesting it was meaningless.
I will say that for most of us, the distance from the injector to the chamber will never change. Most of aren't modifying manifold or building custom billet intake manifolds, and most of us aren't making drastic head modifications. I don't think we'll see values like .9 or 999 either. I'll bet that for most street/strip naturally aspirated LS engines, the values will fall into a range. It won't be a range of .9 to 999, it'll be a range of something like 10 to 50. I'm just not smart enough to know the specifics.
I'll read the article you mention. Thank you for clarifying.
thanks man. really groovy. love it!
I don't think you'll ever see a value of "much" less than 24 in there - not unless it's NA with very large intake ports and a god awful overlap cam - it will actually increase with rpms and I did check to verify that as the number increases that it actually advances injection timing in the graphs...
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
Michael, as I explained in this post, one part is the speed of the air flow and the other is the speed of the fuel spray. These two speeds (if it helps, you can think them as vectors) must be summed up to get the total speed at which the fuel spray will be traveling.
The formula originated from me and I calculated the 24,5 m/s based on a white paper given the typical pressure difference over the fuel injector in NA GM application and the discharge coefficient established in that same white paper.
Last edited by barum; 05-23-2017 at 03:10 PM.
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