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Old 02-03-2011, 10:22 PM   #1
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Default Changed injector size = no start

I swapped out my Supra injectors for brand new high ohm RX-7 550s, and now I am getting a no start.
I am using the DIYPNP startup map w/460cc injectors and I switched Req fuel to reflect the injector change.
Is there any other setting I should have to change in Tunerstudio to get it to start?
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Old 02-04-2011, 08:03 AM   #2
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Nobody? Can anyone offer any insight as to wether or not I need to adjust my priming and cranking pulse widths after changing the injector size? I have read the tuning manual on msextra, but I will be the fist to admit that I am a complete when it comes to this stuff.
My understanding is that Req fuel compensates for the larger injector. The car started with my 305cc injector, with the 550's it smells rich.
Any insight would be greatly appreciated.
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Old 02-04-2011, 09:20 AM   #3
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You have to adjust your cranking pulsewidth. There is a formula to determine how to size it. SEARCH for "cranking pulsewidth".
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Old 02-04-2011, 10:14 AM   #4
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not in MS2.

All that should have been required is to reduce the REQ_FUEL number 17%.


it was running before? Are these High Ohm injectors?
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Old 02-04-2011, 10:29 AM   #5
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it was running ok, key word running. The injectors are high ohm, I set the req fuel using 14.7 and with the Supra injectors the number was 8.50ms with the 550s it comes up with 4.90ms.
My cranking pulsewidth table is what came in the DIYautotune base map:

Coolant(f) Cranking PV
10 ............. 326
30 ............. 301
50 ............. 276
70 ............. 251

Etc.....
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Old 02-04-2011, 10:33 AM   #6
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you took out way too much fuel.

you cut the injector size nearly in half. make it 7.05 and try again.
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Old 02-04-2011, 10:36 AM   #7
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I'll try that, thanks.
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Old 02-04-2011, 03:24 PM   #8
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Yes, without a doubt that was not enough fuel. A req_fuel closer to 7 should get you back close to where you were before.

This assumes that nothing else was changed or damaged during your swap.
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Old 02-04-2011, 03:52 PM   #9
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Thanks for the answers, they helped me find my math error...or should I say data entry error, it helps if you set the number of cylinders correctly

Req fuel works much much better with good input, it came up with 7.6 instead of 4.9.

Thanks again for the help.
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Old 04-20-2012, 08:58 PM   #10
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I was about to change to 550cc my self my current setting on the 460cc for req fuel is:
6.2 and 6.2 ms, This is the base tune provided with the diypnp. So based on this thread I should change to 7.0 on both required fuel and ms. Is that right?
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