RPM lags MAP by 0.4 seconds

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Jim_Blackwood
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

Apparently the total number of injections was too low. Surprised nobody caught that. Well, leave it to me to find what doesn't work.

So that's done, where is that spreadsheet you guys have been using?

Jim
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Re: RPM lags MAP by 0.4 seconds

Post by billr »

"Apparently the total number of injections was too low. "

Can you elaborate on that a bit? You had 1000 set (in screen-shot), it seems that should have been plenty.
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

I raised it to 2000 and it worked fine.

Spreadsheet?
Jim_Blackwood
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

I've been looking everywhere I can think of for this spreadsheet you guys are using to calculate injector flow, deadtime and voltage compensation. I haven't found it anywhere. Saw a post that said it was in the RTFM(!) but couldn't find it in the one in the link James gave me.

A little help here? You were all VERY insistent that this is how it has to be done. Can't do it without the tools.

Jim
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Re: RPM lags MAP by 0.4 seconds

Post by billr »

I don't have a link to that handy, but I'm sure somebody will come up with it; be patient for a bit.

You don't really need the spreadsheet, the video shows how to determine DT with just a paper graph.

How about the flow-rate, were there any surprises there? No need for the spreadsheet for that, and rate has been questioned over-and-over so we can be sure the basic "req_fuel" is finally set correct.
Jim_Blackwood
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

OK, well I don't know how to calculate that. Bit of a problem there.

Jim
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Re: RPM lags MAP by 0.4 seconds

Post by gjestico »

Jim_Blackwood wrote:
IMG_0004.JPG
Are you using clear vinyl tube at fuel injection pressures ? Is that safe ?
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Jim_Blackwood
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

Maybe I have the wrong set of injectors in the engine. I have 2 sets which are green, it looks like they could have gotten mixed up at some point. Well, it happens. To the best of my figuring, these work out to something around 30-35 lbs/hr depending on which test is used to calculate the rate. Maybe I'm doing that wrong. Actual numbers I get are between 285cc/min at 2ms and 20K pulses (191cc measured) and 372cc/min at 16ms and 2500 pulses (248cc measured) (Do those numbers sound about right to you?) I seem to recall buying a set of 35lb injectors before getting the 42lb ones.

So, I'm secure enough to admit it, I was wrong. Made a mistake and installed the wrong parts. The proper thing to do at this point is to test the other set and if they flow correctly, switch them out.

But I still need the spreadsheet.

Jim


>Are you using clear vinyl tube at fuel injection pressures ? Is that safe ?
Thanks for noticing. No I am not and yes it is unsafe. I switched to a 250psi return line to the FPR. (original setup had the FPR on the rail)
Jim_Blackwood
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

The second set are better but vary some. Around 5% at higher flow and near 10% at 2ms. Not ideal but it'll have to do until I can get a better set. At 40psi and 12.5v I'm calculating 38.5lb/hr in the 16ms test.
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Re: RPM lags MAP by 0.4 seconds

Post by billr »

To measure rate, just set the PW greater than the Output Interval; the injector will stay powered (open) during the whole test. You can use a stop-watch to check total time of flow, or just multiply the Output Interval by the Number of Injections; really simple to use and accurate.
Jim_Blackwood
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

Thanks Bill, that was something I didn't understand because at different pulse rates I was getting a lot of variations in calculated injector capacity and couldn't make much sense of it except to blame it on dead time. What you suggest is how I flow tested the injectors before. So I have that last test to do tomorrow before buttoning up the engine. Seems like it should match my earlier results but who knows? Murphy is alive and well.

I'm still missing something in calculating the voltage offset but have good numbers to work from, and I'm not looking forward to trying to create a graph to get the dead time, but at this point it looks like it will be so much easier than finding a spreadsheet simple enough to do it without spending hours figuring out how to use it so I'll just have to get on with it. I do remember seeing instructions for calculating voltage offset in a video so at least there's that.

Jim
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Re: RPM lags MAP by 0.4 seconds

Post by jsmcortina »

Attached is the spreadsheet I used in one of my videos.

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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

Thanks James, that helps immensely and is easy to use.
Injector spreadsheet James Cortina 38.5.xls
I extrapolated the 6ms value but otherwise it is entirely from the test values.

Question: Do you use the calculated injector full flow value, or do you do a saturated flow test and use that value?

Edit: It does make a difference. My calculated value is 38.5, my tested value is 37.7

Jim
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Re: RPM lags MAP by 0.4 seconds

Post by jsmcortina »

Jim_Blackwood wrote:I extrapolated the 6ms value but otherwise it is entirely from the test values.
Don't extrapolate, measure.

James
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

I know, I know. I just wanted to eliminate that point without hosing the spreadsheet. I already had 4 points. It's all good, did you look at it? everything is in a straight line and DT is 0.9-1.0ms just like in the manual. (exactly where depends on how close you read the graph) I just put the 6ms point in line so I could get the DT.

So again: Do I use the calculated flow rate from the spreadsheet of 38.5lb/hr (extrapolated), or the actual numbers from testing of 37.7lb/hr? Just doing my best to follow your lead here. I know it isn't perfect but it'll get redone later anyway with new injectors. When that happens I'll make it a point to get exhaustive data. But it helps me to learn how you guys do things because not everyone does it the same way you do.

Now on that voltage compensation, I'm a little fuzzy on how that is calculated and haven't come out with usable numbers yet. Got a formula please?

Jim
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Re: RPM lags MAP by 0.4 seconds

Post by jsmcortina »

I agree on the 1.0ms deadtime from your numbers. Go with your measured flow. It is within a few percent of the spreadsheet number.

James
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

OK thanks. And what about the voltage compensation? I'm having troubles figuring out how to calculate that. I have the raw data. A 0.7vdc variance but where I'm having trouble is converting the difference in my recorded flows to the cc/mv figure needed. I'm not coming out anywhere near 200 so I must be using the wrong formula.(likely since I'm making it up as I go.)

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Re: RPM lags MAP by 0.4 seconds

Post by jsmcortina »

It is ms/mv. i.e. change to deadtime, not flow.

James
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Re: RPM lags MAP by 0.4 seconds

Post by Jim_Blackwood »

So... graph the line to get DT for both voltages and subtract to get the difference then scale?
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Re: RPM lags MAP by 0.4 seconds

Post by Blown88GT »

jsmcortina wrote:I agree on the 1.0ms deadtime from your numbers. Go with your measured flow. It is within a few percent of the spreadsheet number...
All that work to confirm that the default DT of 1.0 is an acceptable value?
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