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Old 07-29-2021, 07:50 AM   #1
Triebwerk
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Default Injector change to bigger doesīt work

Hi,

increased my injectors from 380ccm to 450ccm and the car runs extremly rich (0,65).

As I will switch to a bigger turbo, I will need these injectors. With the actual setup and the 380ccm it works perfect. 0,8-0,82 under full load. Itīs a tuning software for 400ccm injectors and the 3" air flow meter.
Injectors are both Bosch, EV 6 style. The actual injectors have a resistance of 14,5ohm, the bigger ones 12.
I thought by switching the injectors the car will run a little bit richer and will adapt itself by driving a couple of miles.

What can be the problem?
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Old 07-29-2021, 08:26 AM   #2
740atl
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How are you tuning for the larger injectors? Is this lh2.4? Have you given it enough time to “learn” ? I usually had to drive it a bit for it to adjust… ymmv
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Old 07-29-2021, 08:41 AM   #3
Janspeed
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The big injectors are the problem...
a bit more serious: the LH fuel computer can only adapt AFR to a certain degree.
It delivers fuel based on:
A. base mapping which accounts for the majority of fuel delivery, (lets say 75%?)
B. calculated long term fuel trim which accounts for the adaptability (needed for allevation/airpressure changes, (seasonal) air temp changes) (lets say 20%?)
C. calculated short term fuel trim which does the fine tuning based on lambda sensor input. (needed for precise emissions control) (lets say 5%?)
The actual amount of fuel that is being injected would be A+B+C (100%) needed for a given airmass and engine load.
(don't pin me down on the details, things could be different but generally speaking it's the basic way common rail efi works.)

with those big injectors you increased A. to such a degree that B. and C. can no longer adapt and lean out AFR far enough.

You could try to run those injectors with an adjustable fuel pressure regulator. That way you could adjust fuel pressure down to get the A.-part back down.
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Old 07-29-2021, 09:06 AM   #4
Triebwerk
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Okay. I thought that LH 2.4 has no problem with the additional 20% fuel and will adjust itself.
Reducing fuel pressure will not help as I need the additional juice for the bigger turbo...
Letīs see how much boost I can run with the 380īs until AFR starts to get lean.
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Old 07-29-2021, 09:40 AM   #5
Fa182
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Quote:
Originally Posted by Triebwerk View Post
Letīs see how much boost I can run with the 380īs until AFR starts to get lean.
I ran up to 1 bar with stock 804 injectors (337cc) and stock 016 AFM without leaning out and set it at a comfortable 0,85 bar ever since with my 16T.
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Old 07-30-2021, 02:49 AM   #6
K9 240
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Hi
I have 440ccm injectors on my B200 wth LH2.4 & 960 MAF. AFR's were at 14.7 with a couple of days driving.
Are you running rich throughout the rev range or just when you try to accelerate at higher revs?
Do you know what the spray pattern of the injectors is?
I have used 630ccm injectors on the same set up. AFR's were 14.7 on idle but went rich quickly under hard acceleration. At about 4500 revs it would start to bog down from being too rich.
You can put a potentiometer between one of the wires from the LH2.4 box to lower the MAF signal, but that did not work for me.
Tim
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