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Thread: STI injectors @ 4 bar fuel pressure. Anyone have any knowledge??

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Posts: 21-25 of 25
2015-04-05 12:25:59
Changing the injector size (flow rate) has no effect on the latency, which must be tuned separately.
2015-04-05 13:35:04
Originally Posted by Boostlee
Originally Posted by JKTUNING
What injector latency are you using?

You will absolutely need to increase the latency as fuel pressure rises. If you are trying to use the OEM latency values at 4 bar and the modified injector, that is likely your issue.

John, I am using whatever latency values are scaled after inputting 940cc injectors (what they flow at 4 bar).

Current setup is 0.85 from 10.0 Volts to 16.4 Volts

Send me over your tune file and I can see if I can get it sorted out for you.

Latency will never be a flat line.
2015-04-06 12:37:26
Thank guys for the comments!

@JKTUNING, I did find a set of baseline latency values over at NASOIC. I am going to give those a shot and if it comes to it, I will send it over (or email you) if I have any issues.
2015-04-08 00:54:28

So after figuring what latency for the 800cc injectors, I inputted them into Nismotronic and alas, the car still wouldn't idle. So with this, I sent John my file and low and behold, I was very very close to what latency John was using for these specific injectors! During the 15 mins of messing with it, I found this out below

1) If the latency is set too high to attain a stable A/F ratio, the idle is consistently several hundred RPMS more than what they are set at. Also, the RPMS hang after the throttle has been pressed quickly (A/F staying rich). The car smells pig rich as well
2) If the latency is lowered, but the injectors are scaled lower, the same happens as above (and the car stay rich after a throttle blip)
3) If I leave the latency and Injector scaling and just simply adjust the idle columns, the same as above happens again

Anyways, since it was late I decided to call it a night.

Fast forward to today and I popped the bonnet and BOOM! One of the vacuum port caps had popped itself off of the newly installed IM! I caped it, loaded up a base map with the latency I had for the 800cc injectors, scaled the injectors to 800cc, lowered FP to 3 bar and reset my basemap fuel table numbers and BOOM! Steady idle with -20 in of vacuum! The fix turned out to be free and these big boy STI injector may very well just work out!

Thanks @JKTUNING, @BenFenner and @OnTheChip for the help! Glad to see people are out there willing to help
Last edited by Boostlee on 2015-04-08 at 00-58-04.
2015-04-09 13:08:03

Here are the injector offset values for anyone interested (and for future reference)

Injector latency for Modified (by Witch Hunter) 2004-2006 Yellow Top (510-520cc/min) sidefeed Injectors modified for 800cc (811-816 from the flow sheet)

Voltage(V): 6.00 9.00 12.00 14.00 16.00
Latency (ms): 5.4 1.89 0.97 0.74 0.53

Also, if you like, the latency values for ID1000 @ 3 bar (43psi) can be a baseline as well as they are seemingly not very far off (and I have a hunch I will settle on similar numbers with @ 4 bar for these 800cc injectors).

I will be grabbing a E85 flex fuel sensor, cranking it up to 4 bar (~940cc) and retuning shortly

Last edited by Boostlee on 2015-04-09 at 13-10-10.
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