anyone experience this effect of injecting on intake stroke ?

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Belgian1979
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Re: anyone experience this effect of injecting on intake stroke ?

Post by Belgian1979 » Mon Apr 23, 2018 2:05 am

Thanks.

Meanwhile I've studied it some further. The number of degrees specified in the injection timing table are 'end of injection event' numbers. So in this particular case, my injection ended right on TDC on the intake stroke, which is exactly where overlap is occuring. I would then think that some fuel hasn't fully vaporized and got sucked out through the exhaust valve as some already mentioned.

I currently have my end of injection event set at 408 ° allowing for a 48 ° extra timing, which seems to work rather well.

This also made me think about some of the high rpm exhaust backfiring I have always experienced. Untill now I increased the injection timing with rpm but that seems to be counter productive as well.

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Re: anyone experience this effect of injecting on intake stroke ?

Post by In-Tech » Mon Apr 23, 2018 4:15 am

Truly the "end of injection" needs many tables. The generic is timing vs rpm to correct for transport delay which it sounds as if this is what you are doing. The higher the rpm, the sooner it all needs to "happen" and visa versa. MAP, MAF g/cyl, ECT, IAT and Intake valve temp are critical factors as well. It does get less critical with rpm just because "time" runs out.

Lord, what did we do before sequential and then direct injection? What did a batch fire do? How the fack does a carburetor even work? :mrgreen: :mrgreen: :mrgreen:

Cometic gaskets, aluminum oxide vapor trails and NOX emissions killed the world. :lol: No, wait, it was that dirty R12 that they had to reinvent because the patent ran out, r134 patent is running out, watch what it costs for the new "green" stuff for AC and all the older stuff is outlawed. I digress #-o
Heat is energy, energy is horsepower...but you gotta control the heat.
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Re: anyone experience this effect of injecting on intake stroke ?

Post by digger » Mon Apr 23, 2018 4:30 am

One method I've heard to get injection timing with minimal fuel out the exhaust is to vary the timing for richest mixture then lean it back to suitable mixture

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Re: anyone experience this effect of injecting on intake stroke ?

Post by Belgian1979 » Mon Apr 23, 2018 6:17 am

In-Tech wrote:
Mon Apr 23, 2018 4:15 am
Truly the "end of injection" needs many tables. The generic is timing vs rpm to correct for transport delay which it sounds as if this is what you are doing. The higher the rpm, the sooner it all needs to "happen" and visa versa. MAP, MAF g/cyl, ECT, IAT and Intake valve temp are critical factors as well. It does get less critical with rpm just because "time" runs out.

Lord, what did we do before sequential and then direct injection? What did a batch fire do? How the fack does a carburetor even work? :mrgreen: :mrgreen: :mrgreen:

Cometic gaskets, aluminum oxide vapor trails and NOX emissions killed the world. :lol: No, wait, it was that dirty R12 that they had to reinvent because the patent ran out, r134 patent is running out, watch what it costs for the new "green" stuff for AC and all the older stuff is outlawed. I digress #-o
yes, it makes you wonder. However, when I had it on batch fire I remember that the way the engine was indeed 'rougher'

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Re: anyone experience this effect of injecting on intake stroke ?

Post by Belgian1979 » Mon Apr 23, 2018 6:18 am

digger wrote:
Mon Apr 23, 2018 4:30 am
One method I've heard to get injection timing with minimal fuel out the exhaust is to vary the timing for richest mixture then lean it back to suitable mixture
I've heard that too, but I think in practice this is not as easily performed as it sounds.

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Re: anyone experience this effect of injecting on intake stroke ?

Post by In-Tech » Mon Apr 23, 2018 6:36 am

Belgian1979 wrote:
Mon Apr 23, 2018 6:17 am
yes, it makes you wonder. However, when I had it on batch fire I remember that the way the engine was indeed 'rougher'
Yes, and that truly is what is neat about better control. You're on a tough road and I do like your persistence, it's quite refreshing. The last local electronics shop owner in town, who is closing at end of month, and I were talking about similar things the other day. Very rare to find anyone that builds or repairs anymore...throw it away and buy another. :cry:
Heat is energy, energy is horsepower...but you gotta control the heat.
-Carl

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Re: anyone experience this effect of injecting on intake stroke ?

Post by joe 90 » Mon Apr 23, 2018 6:45 am

In-Tech wrote:
Mon Apr 23, 2018 6:36 am
The last local electronics shop owner in town, who is closing at end of month, and I were talking about similar things the other day. Very rare to find anyone that builds or repairs anymore...throw it away and buy another. :cry:

It's because the experienced people are all retiring and the new wave of fixers get the info off the net, they've got no idea 'cos the net is usually wrong.
But that's a bit of a side track. There's no money in fixing much these days unless it's reprogramming software or maybe recycling essential things like washing machines.

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Re: anyone experience this effect of injecting on intake stroke ?

Post by TBART1970 » Mon Apr 23, 2018 7:21 am

https://forums.holley.com/showthread.ph ... ctor+angle

I have been messing with this for a while, still trying to wrap my head around it.

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Re: anyone experience this effect of injecting on intake stroke ?

Post by joe 90 » Mon Apr 23, 2018 7:46 am

From your link........

HIGH IMPEDANCE INJECTORS — Most injectors can be divided
into two major categories: high impedance 12 to 16 Ohms and
low impedance 1.2 to 4.0 Ohms. The high impedance injectors
are used with ECUs that are designed with saturation drivers.
The advantage of using saturation drivers is that the currents
running through the ECU circuits and the injectors are relatively
low thus generating less heat. The disadvantage of saturation
drivers is that the driver has a slower response time, which could
affect the full utilization of such a system at very high engine RPM.

LOW IMPEDANCE INJECTORS — The low impedance injectors
are designed to be run with an ECU that employs peak & hold
drivers (also called current sensing or current limiting drivers).
The current ratio (peak to hold) is generally 4:1, and the most
common drivers available are 4A peak/1A hold or 2A peak/0.5A hold.
The peak current is generated to overcome the inertia of the closed
valve and once the valve is open the driver cuts down to 1/4 of the
peak current to hold the injector open until the end of the metering
event. Low impedance injector designs are mostly used in high flow
applications.


Which just goes to show that my above post is 100% correct because this cut and paste" is from the net and it's incorrect.

For a start injectors don't have impedance (for car mechanics and parts changers they do though) but they have resistance.
To have impedance you need AC and you need a frequency.
Impedance changes with frequency.
If you bring the frequency down to zero, you've got DC and therefore only resistance.


So as far as resistance goes.......it's resistance.


As far as driving them goes, there's more than 2 ways to do it.
Either full voltage , on or off.
Or full voltage on and off with a ballast resistor added if the resistance is low (the very simplest of peak and hold driver circuits) or more correctly (in electrical engineering terms) operate and hold.
OR some sort of electronic current control in the case of low resistance injectors without a ballast.


But peak and hold injectors and peak and hold driver circuits are 2 completely different things.

Always confused.

But the best part.....







May God's grace bless you in the Lord Jesus Christ.


But that wasn't the original question and it wasn't me that went off at that tangent either.

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Re: anyone experience this effect of injecting on intake stroke ?

Post by hoffman900 » Mon Apr 23, 2018 8:16 am

joe 90 wrote:
Mon Apr 23, 2018 6:45 am
In-Tech wrote:
Mon Apr 23, 2018 6:36 am
The last local electronics shop owner in town, who is closing at end of month, and I were talking about similar things the other day. Very rare to find anyone that builds or repairs anymore...throw it away and buy another. :cry:

It's because the experienced people are all retiring and the new wave of fixers get the info off the net, they've got no idea 'cos the net is usually wrong.
But that's a bit of a side track. There's no money in fixing much these days unless it's reprogramming software or maybe recycling essential things like washing machines.
Not really. It’s because labor rates end until being way more than the cost of just of buying new. Thank you world trade and automation...
-Bob

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Re: anyone experience this effect of injecting on intake stroke ?

Post by Belgian1979 » Mon Apr 23, 2018 9:55 am

TBART1970 wrote:
Mon Apr 23, 2018 7:21 am
https://forums.holley.com/showthread.ph ... ctor+angle

I have been messing with this for a while, still trying to wrap my head around it.
Well, I have now set it so that my injection ends at a point 8ms before the intake valve starts to open. This means in practice 452° BTDC on the power stroke. I always had it set on 408° which place the EOI point just at the point where the valve started to open.

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Re: anyone experience this effect of injecting on intake stroke ?

Post by joe 90 » Tue Apr 24, 2018 3:07 am

Belgian1979 wrote:
Mon Apr 23, 2018 9:55 am

Well, I have now set it so that my injection ends at a point 8ms before the intake valve starts to open. This means in practice 452° BTDC on the power stroke.
No it doesn't.


It's going to vary with RPM because as RPM increases you've got less time between firing events.
At 6000RPM you've got 20 msec in total, at 1000RPM you've got 120 msec.

You're still confused.

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Re: anyone experience this effect of injecting on intake stroke ?

Post by digger » Tue Apr 24, 2018 4:39 am

The fuel must travel from the injector to the valve this takes time.

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Re: anyone experience this effect of injecting on intake stroke ?

Post by In-Tech » Tue Apr 24, 2018 2:36 pm

digger wrote:
Tue Apr 24, 2018 4:39 am
The fuel must travel from the injector to the valve this takes time.
Transport delay. It's not a constant either.
Heat is energy, energy is horsepower...but you gotta control the heat.
-Carl

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Re: anyone experience this effect of injecting on intake stroke ?

Post by RednGold86Z » Thu Apr 26, 2018 4:45 am

In-Tech wrote:
Tue Apr 24, 2018 2:36 pm
digger wrote:
Tue Apr 24, 2018 4:39 am
The fuel must travel from the injector to the valve this takes time.
Transport delay. It's not a constant either.
But it's not far from a constant amount of time. It's coming out of the injector with the same fuel pressure, into, give-or-take, the same air speed, but just some varying density. The air resistance and speed and short distance isn't going to affect the time much. The software should consider whether you want the end to finish with enough time for the last bits to reach the valve, or whether you're interested in the first bits of fuel.

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