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z-ya

Injector Opening Times Spread Sheet

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Hear is a start on the injector opening times for various injectors. I also included two columns for MS PWM limit % and PMW time threshold. Thanks to Clifton for sending me the two RX7 injectors. I will continue to update this as I get more injectors

 

open-times.jpg

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Thanks so much, that is wonderful information that take so much guess work out. I am curious oof the testing methods used, did track the current on the scope ?? Was it fairly apparent when the numbers were reached, or was it subtle and you had to look for it closely??

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Thanks so much, that is wonderful information that take so much guess work out. I am curious oof the testing methods used, did track the current on the scope ?? Was it fairly apparent when the numbers were reached, or was it subtle and you had to look for it closely??

 

Read these threads on how I do the measurements:

 

http://forums.hybridz.org/showthread.php?t=121206

http://forums.hybridz.org/showthread.php?t=121361

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I will be sending a CFI injector for you to test. The big blue 440cc. I think I have a grey one around too. Suppose to be a 503cc.

 

I can't measure flow rate, only opening time. I can then optimize the PWM settings for that injector. I may build a flow rate test bench in the future, but I don't have one now.

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Tune it the same as the MS-I. Set your PWM current limit % and time threshold per this table. Set injector opening time to 1ms. Set battery compensation to default (0.2ms/V). Set the injector PWM period to 50us. This is equivalent to 20kHz in frequency. This is what MS-I uses.

 

If you look at the measurement I made, the period of the ripple on the hold current is what the PWM period controls. If you look closely, you can fit about 10 of those cycles into one grid on the scope display. The timebase is 500us, so 500/10 = 50us.

 

pwm-time-thresh-just-right1.jpg

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Great effort on your part Pete, keep up the good work!! I really like the background info on things, and how they work. It looks like the 50us give a nice clean swing back and forth. I think I am going to reread all the old posts, there is so much info !!

 

Cheers, C

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I see you've got the Bosch "402" CFI injector info. I am going to run Bosch "400" CFIs. Do you think they'd have the same opening times? They all read 2.6-2.7 ohms.

 

Yes, chances are they have very close to the same opening time. I can measure it if you want to send one to me. PM me if you are interested.

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Thanks for the great info. Quick question... I'm using the 280zxt injectors and they are listed with a 1.5 ms PWM threshold. The MS Tuning guide says to start with 1.0 ms and that 1.5 ms and above is risky for burning injectors out. Should I use 1.5 ms as the value in the Constants? I was assuming so, but the Megasquirt info is vague.

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I think the manual is talking about injector opening time, not PWM threshold. You should keep the injector opening time set to 1.0ms.

 

Thanks for the response, z-ya. I'll stick with 1.0 ms as the opening time. I'm still confused though. The MS tuning manual does say to adjust the PWM Threshold Time, not the opening time:

 

1. Start with:

      • PWM Time Threshold = 1.0 millisecond, and

4. Move on to adjusting the time threshold. Lower the time threshold by 0.1 milliseconds at a time until the idle quality deteriorates.

5. Then increase it 0.3 ms.

6. Now, repeat these steps (starting at #2). Adjust the duty cycle and time threshold alternately to get the optimum values for your set-up. You will converge on a set of numbers that work well for your set-up.

 

Use PWM time threshold values greater than about 1.5 to 1.7 milliseconds only with great caution – it is possible to burn out your injectors!

 

Should I set the PWM Threshold to 1.5 ms in the Constants? I've seen a few Contants pages (that have been posted with 280zxt injectors) that are set to 1.0 ms... so, I'm not exactly sure. Thanks for your help.

 

zercs

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You can set it to 1.0ms if you like, and you will most likely be OK. I optimized the settings for the injectors in the spread sheet. The MS manual was probably written just using Megatune and a running engine, without a current probe and scope.

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Has anyone gotten this info for their car with Supra 440cc injectors? I've got MS1 v3.57 stock motor with these injectors.

As long as you have a similar brand of injector to get some times off of, you should be close enough. It doesn't really make a lot of difference unless you had an existing map with another injector and wanted to minimize the retuning when you change injectors.

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