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Misfiring when cold

Posted: Sun Jul 28, 2019 2:53 am
by D33@+H-Kn1gH+
I have a fully forged turbocharged FN2 and mainly during the warm up phase I'm experiencing misfires if I depress the throttle pedal more than slightly. When the car is warm the issue stops.

As I am using Injector Dynamics ID1700x , I had to lower the target AFR because the car would misfire a lot in the warm up phase and less when it was up to temp. Now as Injector Dynamics advised since my injectors are big I am forced to keep the AFR around 13ish in order to avoid misfires. (Anything above 14.0 AFR causes misfires in general). I must also mention that I am using these injectors on Unleaded 100 gasoline thus the reason for a lower AFR.

I've noticed that the more I step on the throttle pedal the leaner the AFR ( 14.0 - 14.4 ) goes for 1-2 seconds causing the misfires during the warm up. I am also experiencing similar AFR behavior when I step on the throttle pedal and the car is already up to temp but I don't get misfires because the AFR stays below 14.0 . I am using a Honda J37 throttle body and my tuner already altered the throttle flow VS opening for that.

Could this be a throttle tip problem? If yes which table shall I alter "Tip in fuel ECT" or "Tip in fuel throttle compensation" ?

Re: Misfiring when cold

Posted: Mon Jul 29, 2019 9:42 am
by Spunkster
Have you discussed this issue with your tuner?

Re: Misfiring when cold

Posted: Mon Jul 29, 2019 12:05 pm
by D33@+H-Kn1gH+
Spunkster wrote:
Mon Jul 29, 2019 9:42 am
Have you discussed this issue with your tuner?
He said that the fuel injectors are just too big for my engine and Unleaded 100 fuel makes it even worst on these injectors.
It could also be that because they're big it takes more time for them to respond to sudden throttle changes. I honestly don't know..

I am currently breaking in the engine so I'm using a break in map at the moment (3.5 bar static fuel pressure through a regulator, low cam only no vtec, 7000rpm redline)

I really don't wanna spend more money to get the ID1300x if they won't cure the problem. I have also spoken to Injector Dynamics about the ID1300x and they said that I might be a little rich on them too since my engine is a 2.0L but definitely better than ID1700x and the only injectors that are perfect for regular Unleaded fuel are the ID1050x though they're not enough for my build I presume

Re: Misfiring when cold

Posted: Mon Oct 28, 2019 6:50 am
by typer86
In your tune more fuel must be injected in relation on the water coolant temperature... (fuel compensation)

It's totally wrong answer fro your tuner regarding the size of Injectors... If the engine need more fuel if cold then this must be added! The K20 use the water temperature to add or reduce fuel until normal working condition.

In my supercharged version I must add 14% fuel until my engine heads up til 30C° or so. In natural aspirated Version this will drop to 9% so if I I did not Compensate it the engine will start missfire - no power jumping - going crazy...

Re: Misfiring when cold

Posted: Mon Oct 28, 2019 9:56 am
by D33@+H-Kn1gH+
I already bought the ID 1300x, will install them soon. The ID1700x have multiple problems running on Unleaded fuel.The idle AFR is never near where you set it. If the car idles at 13.3AFR next time you cold start it when its fully warmed the AFR drops to 12.5. Anything near 14AFR is causing rough idle and misfires. Spark plugs get fooled all the time it's a never ending story..

If you road use your vehicle and you are using Unleaded fuel never buy ID1700x as a primary injector set. Best bet would be to use 8 injectors and use something like ID1050x for cruising.