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Discussion Starter #1
Hello,

I just install RC 750cc injectors. I configure in the PFC the new size to 59% (444-750 *100) and according to the latency of the injector (0.18-077) to -0.59.
After this, the car don’t want even to start. I change the latency to +24 and looks like is working fine, but running a little lean on boost even if i put +30(afr is 12) . I needed to set 1.100 in the inj temporary correction for don’t have knock.
Does anybody know the correct latency for these injectors? Or I’m making something wrong?

The FPR is stock, and the pressure is in normal levels.
 

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it sounds like you've done everything right, however i thought the rc injectors had a sheet that had individual flow rates and latencies, might be best to check this first

are they new? maybe they need cleaning?
 

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Discussion Starter #3
They are new, and came with the flow rate. I asked the latency to RC, and received this.
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Here are the latency times for the PL4-750D:

10v 0.88ms

11 0.66

12 0.48

13 0.32

14 0.18

15 0.05
 

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have you put this information into the powerfc where it has lag vs battery voltage? if so i think you can just leave the individual injector lag times at 0 but im not sure
 

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Discussion Starter #8
Same. I change the latency directly with datalogit and car doesn’t want to start normal. If i give some gas yes, but not idle.

Nobody have these injectors???
 

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Dani
If you want your afr's to be perfect after an injector change you will have to get a retune. No injectors are the same, and the flow numbers are often measured at diffrent pressures and so on. Also it's not easy to get the power fc to correctly use the latency times for you injectors.

What I usually do, is to use the percentage values to get the correct afr's on boost, and then finetune the cruise/idle afr's with the letency column in the end. This is the easy way you can do this without doing an complete retune.
 

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They are new, and came with the flow rate. I asked the latency to RC, and received this.
----
Here are the latency times for the PL4-750D:

10v 0.88ms

11 0.66

12 0.48

13 0.32

14 0.18

15 0.05
Those dead times look out of this world to me.
Typically at 14v and 45psi fuel pressure you are looking at 1ms dead time.
Jason
 

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I use RC Racing 1000cc, I had no problems. They are disc-type injectors, so they are faster than Denso-type injectors. Latency in my case went negative - mine are happy with lag times at -0.16ms.

Elvindf's method works very well to rough-in new injectors. You do need a wideband though.
 

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Discussion Starter #12
So you mean the latency is only important at cruise/idle??? dont do anything on boost?

The problem is, they are not a little out of the theorical numbers (-59!!!). The idle is not ok until +20-24. In this case the AFR with the O2 off, is close to 14.7. Any negative number is not working. They shoul be faster, but looks like they are much more slower.

The car has a wideband, and with the size correction to 59% is going ok on boost.
 

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So you mean the latency is only important at cruise/idle??? dont do anything on boost?

The problem is, they are not a little out of the theorical numbers (-59!!!). The idle is not ok until +20-24. In this case the AFR with the O2 off, is close to 14.7. Any negative number is not working. They shoul be faster, but looks like they are much more slower.

The car has a wideband, and with the size correction to 59% is going ok on boost.
The latency/dead time/ battery compensation is very important!
Compensating for a bad map by fudging dead times puts all compensations out as the dead time is generally the last variable on the fuel calculation. Using incorrect dead time settings will result in continually altering afrs as inlet air temp,fuel temp, engine temp, barometric pressure blah blah blah arnt compensated for correctly!!!
This will result in frequent "retunes" to conditions! Exactly what efi isnt ment to be about.
Use the manufacture supplied dead times and tune to suit.
Hope this helps.
Jason.
 

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I totaly agree with Infomative that a proper retune is the only way to properly fix this, but to use the injector settings as trims to get the car driveable will do the trick as well.
At least temporary.
It's not everyone that has a dyno around the next corner.
 

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The latency/dead time/ battery compensation is very important!
Compensating for a bad map by fudging dead times puts all compensations out as the dead time is generally the last variable on the fuel calculation. Using incorrect dead time settings will result in continually altering afrs as inlet air temp,fuel temp, engine temp, barometric pressure blah blah blah arnt compensated for correctly!!!
This will result in frequent "retunes" to conditions! Exactly what efi isnt ment to be about.
Use the manufacture supplied dead times and tune to suit.
Hope this helps.
Jason.
Sounds interesting. What are your lag vs voltage table values?
 

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Whatever the injector manufacture says they are at the specified pressure /voltage/ driver setup.
What may be happening is the injectors dead time is rated with a peak and hold driver then fitting them to a vehicle with resistors is resulting in a different resultant deadtime.
This is a drawback of low resistance injectors as its easy to see all the variables leading to non linearity that arnt present with modern high impedance injectors.
A quick test to do is get the engine running at a stable fast idle, vary the system voltage (i use a carbon pile load tester) and ensure afrs remain constant. Alternatly you can disconnect alternator and monitor as the voltage dropps.
The draw back is if the normal operating voltage deadtime is wrong the error will still be present in fuel calculation.
Another variable is useing a non 1 to1 fuel pressure reg. As fuel pressure multiplies dead times change therefore you have to set up a deadtime 3d table that takes fuel pressure into account(easy to do with Link)
Check with RC on deadtimes with resistors fitted.
Jason.
 

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Dead times aren't on the flow test sheet that came with my injectors, I'll have to ring them up. I suspect mine are slightly off at high flow, I've been running richer than I'd like ever since I've been having electrical niggles cropping up.
 

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Discussion Starter #18
The lag times I write, are the ones they send me by mail.

I can understand a minimal retune after the new injectors, but in this case if I put the latency they told me, the car will not start. How can be tune? Change to very rich in the injectors table to start. And if I put the +24 to make it start, after the latency will be incorrect in the rest.

Today Ill install the OEM again. I think the RCs will go for sell.
 

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Bringing it back from the dead... I running the rc 750s and tryin to set the latency times.... I have a dataloggit and I've entered the lag times in to the batt volt vs lag time and the car still doent idle. If I leave the settings stock and just change the lag time only in the injector colum to .20 everything is good

Just wondering what everyone has done for settings
 

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I had similar issues with the my 1200cc RC injectors. Had to add a little more lag time than stated, but this could be due to a number of things. Fuel pressure, Injector location (RC injectors work for diff models), Voltage, Map ect. Remember, every car is different. Your engine will tell you what it likes, and what it likes may not match the makers specs exactly.
 
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