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Meat Popsicle
91 CRX Si
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2,936 Posts
Discussion Starter #1
I switched from DSM 450s to 600cc Bosch EV14s and I had to increase my fuel map by about 6-8% at idle to get back to 14.7:1.

I’m confused by this. I thought that I’d be running super rich but I was drifting up into the 16:1 range at idle with the 450cc map.

I’m guessing this has something to do with the difference between peak and hold and saturated injectors but I just wanted to double check.

Any thoughts? I don’t want to keep adding fuel to cover up a potential problem if this isn’t expected behavior
 

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Registered
97 honda coupe
Joined
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7,611 Posts
I switched from DSM 450s to 600cc Bosch EV14s and I had to increase my fuel map by about 6-8% at idle to get back to 14.7:1.

I’m confused by this. I thought that I’d be running super rich but I was drifting up into the 16:1 range at idle with the 450cc map.

I’m guessing this has something to do with the difference between peak and hold and saturated injectors but I just wanted to double check.

Any thoughts? I don’t want to keep adding fuel to cover up a potential problem if this isn’t expected behavior
might have to do with the actual fuel being injected with the larger injectors, large injectors do funny things when actuated slowly on the low end. Ive dealt with this quite a bit on my turbo ls1 with 80lb/hr injectors. the difference between 1.2ms and 1.3 is a cavernous uncanny valley of wtf is going on.

that being said, 600's arent extreme i would expect them to be a little more consistent on the low end, especially if they are bosch brand name. Perhaps they have an odd low pulsewidth curve, or your going below the minimum pulsewidth causing them to not open fully and give you lean results. If your going from saturated to peak and hold you might want to check your resistor pack to make sure they are getting the correct amperage/voltage as this can cause the injectors to not fully open if the voltage is sagging.
 

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Meat Popsicle
91 CRX Si
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2,936 Posts
Discussion Starter #3
Yeah, it was weird. At idle the AFRs would start at 14.7ish then slowly creep up to 16-16.5:1 before I shut it off. Added like 6% at idle and it stabilized at around 14.2:1.

I figured it was something related to latency or pulse width but I couldn’t work it out in my head.

It’s richer everywhere else so I’m guessing it’s just the behavior of the higher impedance saturated injectors.

Thanks
 

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Registered
97 honda coupe
Joined
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7,611 Posts
Yeah, it was weird. At idle the AFRs would start at 14.7ish then slowly creep up to 16-16.5:1 before I shut it off. Added like 6% at idle and it stabilized at around 14.2:1.

I figured it was something related to latency or pulse width but I couldn’t work it out in my head.

It’s richer everywhere else so I’m guessing it’s just the behavior of the higher impedance saturated injectors.

Thanks
Yeah as long as its consistent i wouldnt be too worried about it. Do you happen to have a data sheet on them?
 

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B-series Destroyer
4g 4d civic
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913 Posts
When I switched to my 880cc injectors my car was so lean it wouldn't even idle. When I ran dsm's the car was a little lean on first startup, however it started and ran.
 

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Meat Popsicle
91 CRX Si
Joined
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2,936 Posts
Discussion Starter #7
Yeah, I think the low impedance DSMs just responded faster and did better at low pulse widths. I needed to clean up the fuel map anyway so this forced me to do it
 
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