Georgia Fiero Club Forum
All Things Fiero => Tech Tips, Tech Questions => Topic started by: Fierofool on March 27, 2021, 07:04:45 pm
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How much does impedence affect fuel injectors? What would be the effect of going from 14.3 ohms to 15.9 ohms do with all other perameters being the same?
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Heat? There would be a marginal increase in temperature.
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Does it change the pulse width or flow rate?
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It does not seem so, but it opens more quickly. Maybe slightly.
There are low-impedence injectors (2-3 Ohms).
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Thinking about this, fuel pressure is still the same, the injector nozzle is still the same, and the open/close points are the same, so the flow rate should not change. There may be a marginal change in pulse width, but the computer may well compensate.
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How much does impedence affect fuel injectors? What would be the effect of going from 14.3 ohms to 15.9 ohms do with all other perameters being the same?
By my way of thinking, none. None at all. They are both considered "high impedance" injectors.
As GTRS alluded to, 2-3 ohm are considered "low impedance" injectors. Which (as near as I've been able to observe) just so happens to coincide with ridiculously high flow rates. 40-50 lbs/hr., etc.
As long as they're in the teens, I wouldn't worry about it. At all.
Edit - To further muddy the waters, there is a difference between "impedance" and "DC resistance". (This is particularly important when discussing hi-fi speakers. Perhaps not so critical, when discussing injectors.) But some engineer, somewhere, might take issue, so... there's my caveat. :p
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That begs the question: Are you trying to change the pulse width or flow rate by increasing impedance, or are you troubleshooting a rich condition?
Would you believe there are 70-Ohm injectors?
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In the past I've seen precautions given on PFF that one should be sure the replacement injectors are of the same impedance as the old ones.
Just by changing out injectors, I now have a bad stumble at normal acceleration. Also, at idle, the engine will drop to 5-600 rpm and then kick back up to about 2000, slowly getting back to 1100 for a while before near-stalling again. Sometimes it will stall.
Sandman07 had the same problem and he had to reset the TPS. Though we changed nor touched anything else, this issue surfaced immediately after startup. These injectors flow a little more than the old ones and seem to work well out on the highway.
GTRS, I changed to the upgraded injectors for the 3.4. The old injectors were 14.3. The new ones are 15.9.
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70 ohm? What is the application?
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Charlie... have you got a link / part number to your injectors?
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In the past I've seen precautions given on PFF that one should be sure the replacement injectors are of the same impedance as the old ones.
Just by changing out injectors, I now have a bad stumble at normal acceleration. Also, at idle, the engine will drop to 5-600 rpm and then kick back up to about 2000, slowly getting back to 1100 for a while before near-stalling again. Sometimes it will stall.
Sandman07 had the same problem and he had to reset the TPS. Though we changed nor touched anything else, this issue surfaced immediately after startup. These injectors flow a little more than the old ones and seem to work well out on the highway.
GTRS, I changed to the upgraded injectors for the 3.4. The old injectors were 14.3. The new ones are 15.9.
That sounds like a vacuum leak.
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70 ohm? What is the application?
Dunno. I saw that when looking for something else. Seems like a waste.
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That sounds like a vacuum leak.
I'm thinking it also sounds like what happens when you plug disk type injectors into a Fiero ECM.
But I'll withhold comment until I see what the injectors are.
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Bosch 280 150 941 @ 14.3 ohms, old injectors flowing 14.1 or 14.4 # /hr, depending upon which Bosch chart you consult. 43.5 psi
Bosch 280 150 415 @ 15.9 ohms, new injectors flowing 16.6 #/hr @ 43.5 psi. These are Bosch EV1 injectors. 4 pintle.
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Heh... I found your post on the injectorplanet website. And indeed, they should work. All I can think of is that they might be a bit rich at idle.
Did Sandman's TPS reset fix the problem? if not, it might still be a bit "fat" at idle.
Does it get any better (or worse?) after it's good and warmed up? I ran 19s in my 3.4, and it idled okay with a stock tune. (Made my eyes water, though, until it warmed up and went into closed loop. Never did any of the hunting around stuff, though.)
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It's a little rich in open loop. Smells fine in closed loop when it's warmed up.
Sandman tweaked the TPS stop a little and it fixed the problem.
Car doesn't seem to have the power and acceleration it did before, but if I put it to the floor, it will accelerate just fine. Any gear.
Thanks for clearing up the impedance question. I think first thing I'll do is try the TPS adjustment. That's easiest. Then maybe another new o2 sensor. The one that's in isn't more than a year old.
For now, the car's back under wraps until the weather clears up.
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The acceleration characteristics may indeed be different. I'm not surprised.
It'll probably take the ECM time to adapt to how those injectors work, and it will probably take some time for your "butt dyno" to get recalibrated, too. (You think I'm joking, but perception IS reality. Give it a bit.)
Once you've had them in there for a bit, we can scan it, and see what the fueling is doing.
Edit - Are you still running the stock chip?
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I have about 100 miles on it so far. Maybe you can make the meeting this month?
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I have about 100 miles on it so far. Maybe you can make the meeting this month?
Not sure. I'm going to wing it. My second shot is on the 15th.
If I come. I'll bring my scanner.
We can talk, before then.
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That sounds like a vacuum leak.
I'm thinking it also sounds like what happens when you plug disk type injectors into a Fiero ECM.
But I'll withhold comment until I see what the injectors are.
Bosch 280 150 941 @ 14.3 ohms, old injectors flowing 14.1 or 14.4 # /hr, depending upon which Bosch chart you consult. 43.5 psi
Bosch 280 150 415 @ 15.9 ohms, new injectors flowing 16.6 #/hr @ 43.5 psi. These are Bosch EV1 injectors. 4 pintle.
I think that 4-pintle injectors may be a problem. Someone else tried those, and the ECU was not very happy.
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I only know of tnkgnr in Virginia that's having a chockingly rich burn. I've worked with 3 or 4 others on the 3.4 conversion and all are getting good results.
Raydar, the meeting is the 10th. And isn't tnkgnr Ramon's son? Seems that's the name that contacted me years ago asking us to help put Ramon's car back together as a birthday present, or something.
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I have about 100 miles on it so far. Maybe you can make the meeting this month?
Not sure. I'm going to wing it. My second shot is on the 15th.
If I come. I'll bring my scanner.
We can talk, before then.
My first shot is usually effective. ;)
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I only know of tnkgnr in Virginia that's having a chockingly rich burn. I've worked with 3 or 4 others on the 3.4 conversion and all are getting good results.
Raydar, the meeting is the 10th. And isn't tnkgnr Ramon's son? Seems that's the name that contacted me years ago asking us to help put Ramon's car back together as a birthday present, or something.
Which ECU did they use? My stock ECU was able to handle some things that an '86 ECU could not.
My '7730 did not like the Accel injectors.
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I have about 100 miles on it so far. Maybe you can make the meeting this month?
The ECU should have adjusted, by now, if you had a 30zmile run in there.
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Sandman07 had the same problem and he had to reset the TPS. Though we changed nor touched anything else, this issue surfaced immediately after startup. These injectors flow a little more than the old ones and seem to work well out on the highway.
I suspect he basically just increased the idle, thus masking the problem.
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I only know of tnkgnr in Virginia that's having a chockingly rich burn. I've worked with 3 or 4 others on the 3.4 conversion and all are getting good results.
I read that thread. His issues sounds like the same issues you have. Only difference is, he doesn't have a good set of injectors to which to return.
BTW, Rodney's lines work fine on my Fiero, including the line from the MAP to the FPR, so likely not the issue.
Why noy get another set of the injectors that were supposed to be used for your 3.4 swap?
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As far as I know, all are using their stock Fiero ECU.
When Sandman adjusted the TPS stop, the stumbling and stalling went away and the idle is smooth at 1100 rpm, so it really didn't mask the problem.
I already have over $200 into the rebuilt 3.1 injectors and their replacements, plus what I paid for these. I don't really have the money to spend. I'd rather try to solve the problem before buying more expensive parts. If I can't find the cause, I'll go back to what I just pulled out. After all, other than showing they were lean at wide open throttle, they have given me a dependable 50k miles.
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Maybe I'm missing something, but my understanding is that opening the throttle a bit stops the idle surge, the stumbling, and the stalling. It would seem that adjusting the TPS stop would slightly open the throttle.
Reading up on this, it seems that some people fixed this by making an adjustment to the ECU.
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I should mention that several of my vacuum line elbows ended up with small leaks, and had to be replaced. The main leak was the line from the PCV to the throttle body, at the throttle body end.
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We checked fit on all fittings. The only one that was loose was the elbow at the EGR valve. It got some Ultra Black RTV on the tube, let it harden just a bit, then slipped the elbow onto the line. No EGR codes.
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My elbow fit, but had small cracks. I did not find the cracks for 3 years.
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I went out this afternoon and readjusted the TPS paddle. Car idled about 2000 while warming up and on several occasions eased down to 1100. Occasionally it would drop to 600 then kick back to 2000. Once it got fully warmed, it dropped down to 1100 and held steady.
Tomorrow, I plan to take it on a little extended drive up I-85. The trunk area will be sporting a new TPS just in case. I'll have to fill up before the trip. 121 miles on the new injectors, so I want to know what the mileage difference is on surface roads and interstate.
Anyone between Braselton and the SC state line want to meet up for lunch?
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https://www.throttlebodys.com/FieroTBs.htm
Not sure but this might help some. Worth thinking about. It’s only $150.
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That would give it a little more power, but the real choker is the neck on the upper intake. To obtain maximum advantage of the bored out throttle body, the neck needs to be enlarged. It does little good to have a big mouth if the food won't go down the gullet.
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I went out for a test drive on a full tank. Before filling up, I checked MPG and it was 22. The first 3 miles on the interstate took 30 minutes so I got off I-85 and went over to I-985. At Road Atlanta, I stopped and swapped out TPS's. The car began to run better.
At about the point where I began to make my loop back down US 441 to I-85, it started to stumble a bit and the CES light came on and I could smell a very rich exhaust, especially when I stopped. When I got off the interstate near home, I filled up again. Checked the mileage and it was only 15 MPG.
When I got home I checked codes and I had a 21, TPS, a 34, MAP, a 44 and 45, Lean and Rich, respectively. So, I cleared the codes and restarted the engine. It soon set a 21, TPS, again. Still running very rich.
I went online to order a new TPS and compared Autozone Duralast at $81, NAPA at $69 plus shipping from Virginia, and Rock Auto at $69 delivered. Looking at the images, NAPA is listed as Echln while RockAuto is listed as Standard. The images shown are identical, right down to the specks of dust on them. I sprung for the RockAuto sensor, so we'll see on Friday if it fixes it. If not, I'll swap out the MAP for another, then final cure will be to go back to the old injectors.
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It would not seem that a TPS would suddenly fail, just because the injectors were changed.
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I agree. The intake was carefully set aside on a work table. Nothing was done to it or the MAP sensor. Sandman07 had a similar experience with the TPS. Only tnkgnr and I are having his rich condition.
There was something strange that Scott and I encountered, and it had to be done by someone familiar with opening the deck lid without a key. I have replaced the plug wires, distributor cap and rotor within the last year. When we removed the distributor cap to gain some clearance, we found a wad of aluminum foil stuck on the pointer of the rotor button. I don't know who I've made an enemy of but your sabotage effort failed because the car ran well.
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"Did you get the memo about the TPS reports?"
With the MPG you were getting, with the old injectors it wouldn't seem that you were running rich.
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No, the old injectors were lean at Wide Open Throttle.
Maybe my current problem is because I removed the aluminum foil. Maybe I should put it back and see what happens.
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Aluminum foil?
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https://www.throttlebodys.com/FieroTBs.htm
Not sure but this might help some. Worth thinking about. It’s only $150.
My throttle body is bored out. It did not seem to change anything on the butt dyno.