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Old 11-18-2018, 10:11 PM   #51
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Starting to notice that these injectors work better at 2.7 Bar fuel pressure. Engine idles rough until it warms up at 3 Bar fuel pressure. Duty cycle is nearly the same at either fuel pressure. Idle: 60% compared to 58%. Engine off : 82% compared to 79%. So I take it that the fuel pressure difference has little effect on the duty cycle. So go with the fuel pressure that works best for the injectors?

Info that I found on Mustang Cobra site about running injectors that are too big:
* Lower fuel pressure and increase injector openings.
* Run richer at idle.
* Run a less aggressive injector if ECU allows it.
* Raise the idle speed.
* A combination of a few above...
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Old 11-19-2018, 01:04 PM   #52
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Swapped to a second BMW 2.5 Bar FPR because car was hard to start this morning (35* F) with the Buick 3.0 Bar FPR. Now to wait for it to warm up a bit outside to do a pressure test with this other BMW FPR.

Looking through my FPR's to see if I have a good OE Volvo type FPR.
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Old 11-22-2018, 02:54 PM   #53
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Today I found a different dwell to duty cycle conversion chart. I retested with the dwell meter on a warm engine and got 36 degrees on 6 cyl scale. According to this chart 36 degrees on 6 cylinder scale = 40% duty cycle. 40% duty cycle at idle in closed loop makes much more sense.

Ground controlled circuit @ 36 degrees on 6 cylinder scale = 40% duty cycle
Feed controlled circuit @ 36 degrees on 6 cylinder scale = 60% duty cycle

Not sure about the voltage reading that I was getting. With dwell meter at voltmeter connected at same time between test point and battery positive showed 5.95 VDC. 5.80 VDC corresponds to 60% duty cycle on same chart.

Last edited by lummert; 11-22-2018 at 04:10 PM..
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Old 12-18-2018, 02:59 PM   #54
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Found specs for 36 lbs/hr injectors when running at 39.15 psi (2.7 Bars).

34.0 lbs/hr @ 39.15 psi
357.3 cc/min @ 2.7 Bars
257 grams/min @ 2.7 Bars

35.84 lbs/hr @ 43.5 psi
376.7 cc/min @ 3 Bars
.52 BSFC - Estimated HP @ duty cycle
52.3 @ 80%
62.1 @ 95%
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Old 12-18-2018, 03:28 PM   #55
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Duty cycle is calculated by comparing the injector pulsewidth to the time it takes to complete an engine cycle.

For example, an engine idling at 800 rpm takes 150ms to complete one full engine cycle of 720 degrees crank rotation.

If your idle injector pulsewidth is 3ms then your injector duty cycle is 2%. Simple as that.

You’re trying to look far to into this.
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Old 12-18-2018, 03:33 PM   #56
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Quote:
Originally Posted by gross polluter View Post
Duty cycle is calculated by comparing the injector pulsewidth to the time it takes to complete an engine cycle.

For example, an engine idling at 800 rpm takes 150ms to complete one full engine cycle of 720 degrees crank rotation.

If your idle injector pulsewidth is 3ms then your injector duty cycle is 2%. Simple as that.

You’re trying to look far to into this.
One thing I know for sure is that these injectors (Bosch 0 280 155 811) work best at 39.15 psi (2.7 Bars), same as when running these on a Ford Mustang.
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Old 12-18-2018, 06:36 PM   #57
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When you’re trying to patch it into a different application such as this, maybe. When properly controlled they’ll operate just fine with any other common fuel pressure.
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Old 12-21-2018, 11:48 AM   #58
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Quote:
Originally Posted by gross polluter View Post
When you’re trying to patch it into a different application such as this, maybe. When properly controlled they’ll operate just fine with any other common fuel pressure.
I figure they would work just fine a 3 bar with a larger AMM.
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Old 12-31-2018, 05:42 PM   #59
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Running these 0 280 155 811 injectors at 2.5 Bar resulted in an average of 14 MPG with my 1988 B230FT on LH 2.2. Yesterday I dug out another Bosch 0 280 160 237 3 Bar Fuel Pressure Regulator that was in my stash and installed it. This FPR fits 1989 Pontiac TTA (Turbo Trans Am), as well as other 87-92 GM cars with 3.8 L V6.

The specs are:

37-43 PSI with vacuum connected
40-47 PSI with vacuum disconnected and plugged
Buick has it rated at 45 psi.

I installed this fuel pressure regulator without any adjustment to the AMM POT screw. Waiting for the rain to let up long enough to check the baseline fuel mixture adjustment. The engine has a decent idle and good power. The warm starts seem to indicate that the fuel mixture is slightly rich. I also need to hook up the pressure tester and check against the FPR specifications.

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Old 01-01-2019, 05:17 PM   #60
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Increasing the fuel pressure from 39 psi to 44 psi increased my MPG's from 14 to 19.8.
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Old 01-03-2019, 09:48 AM   #61
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After taking time to set the baseline fuel mixture the MPG's are up to 20.94.
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Old 08-01-2019, 08:49 PM   #62
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Been running these injectors for awhile now. Buick 3.0 Bar FPR, BMW white connector ECT, Open breather filter on valve cover. Toyota Supra Twin Turbo PCV valve mounted between block mounted oil separator and intake manifold vacuum port using 3/8 inch nipple (with vacuum pump intake filter fitted in the middle). Nipple on turbo inlet hose plugged. Been messing with adjusting the baseline fuel mixture. I have been enriching the mixture about a quarter turn using the AMM pot screw at the last 3 tank fillups. Every time I turn the screw another quarter turn clockwise i get .2 more miles per gallon, so far up to 24 mpg average on the last tank. I figure to keep enriching the mixture until the mpg's start to drop.
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Old 08-07-2019, 08:58 PM   #63
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While replacing my 30k mile Autolite XP63 spark plugs with a new set I had on hand I found that number 4 plug had lots of white ash deposits. So I pulled the fuel rail to swap in a spare injector to replace number 4. Engine idles better, vacuum test gauge shows a steady 20 inches of vacuum at idle. Next I needed to reset the baseline fuel mixture. Managed to start with a baseline setting of 385 ohms at the AMM pot screw. Figure I'll end up with a baseline setting near 300 ohms (calculations show 298.67 ohms needed).
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Old 08-10-2019, 12:13 AM   #64
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A day later and i had the top o-ring rip on number 4 injector and spray fuel when trying to start engine. Engine started but I smelled raw fuel, looked out drivers window and saw fuel running out from under car. Shut off engine, went to work fixing the problem. Had to pull injector rail in nursing home parking area before I could leave. Had 0-rings with me. Figured out that to be safe these injectors need one o-ring on the top and 2 o-rings on the bottom of each injector. So removed the o-ring spacer which is half as thick as 0-ring and installed to bottom 0-rings.

Everything seems to be secure at this time.

As far a baseline fuel mixture my calculations may have been incorrect. I was using 385 ohms as baseline starting point then remembered that when i had removed the plug from the AMM the baseline setting was 269 ohms. So 21% [300.6/363.1] more fuel should result in 269x.79=212.51 ohms
baseline setting.
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