I am running a custom tune, but the headers etc weren't installed yet. Do you think I should get an update?Welcome to the forum. I just installed headers as well but I installed extra O2 bungs for a wideband as I am running a supercharger, which will come in handy when I get the tune modified. You are not going to see the full gains of LT headers with the factory PCM tune and you run the risk of running lean at WOT. A custom tune will also ensure you will not get the CEL due to the high flow cats.
If the exhaust changes result in better flow through the engine -- which may be questionable without a corresponding change to the intake system -- the engine controller should "adapt" to the higher air flow and add more fuel. This is done by simply leaving the injector on longer.I recently installed long tube headers and hi flow cats, the manufacturer stated there might be an issue with the air/fuel ratio. If my car isn't showing the dreaded check engine light, is everything cool?
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The amount of fuel added is based on the amount of air the engine flows. This is measured by the MAF. Additional fueling precision is obtained using the O2 sensors.The size of the stock injectors can provide plenty of fuel, it's the waveform that dictates how much fuel is delivered...hence the need for a tune.
Umm, the 5.7 and 6.4 use a MAP sensor...no MAF. Not sure why this is turning into a big discussion, if you add headers a tune is needed.The amount of fuel added is based on the amount of air the engine flows. This is measured by the MAF. Additional fueling precision is obtained using the O2 sensors.
Within reason the engine controller can adapt/adjust to a change in air flow by increasing the width of the injector pulse. While there is a considerable range of adjustment if the adjustment range gets close to +/- 10% off the the base line the engine controller may throw an error code.
Under WOT throttle -- and even close to it -- the engine controller can go open loop mode and rely on fuel maps to fuel the engine. However, these fuel maps may not be optimum for a modified engine, one that has an exhaust that can flow better. In this case the engine can run lean.
Thus a tune may be needed -- a tune based on info gleaned from dyno testing with exhaust gas analysis -- to provide for a more optimum fueling based on the engine mod's. The base line may need to be adjusted so the engine controller can add more fuel without exceeding its limits and for WOT (or at least open loop) operation the fuel maps can be made richer to ensure the engine receives the proper amount of fuel.
Back in the day, cars were rich from the factory and headers were just bolt on and go. In the 70's they leaned out the A/F and when I put headers on my '75 I bought a carter street/strip kit and rejetted and changed the metering rods to get it right. Now days, you need to change the tune to affect how long the injectors spray, I guess. Too bad they don't just sell bigger injectors.
EDIT: this one first makes more senseI was told long tube headers it WILL run lean and before you can get a custom tune just add 5% fuel.
Even without a CEL it could still run lean in some spots?
Correct they do, but you can't just swap those, at least I don't think you can just swap those when you put headers on instead of tuning...
I talked to the company, (Hemifever)that did my original tune and they gave me an updated version.I can't say anything about Mopar tuning, but when I first put my headers on my old C5 Vette (LS1 motor), I didn't tune it and it threw no codes, knock or anything strange.
After getting my tuning software, WB02 and stuff and before I put the blower on her, I did some logging and actually found that the header made it fat (rich). I thought this was strange, but the facts don't lie.
As far injectors, tuning a GM required me to change the IFR (Injector Flow Rate) to the specific sized injectors that I installed after installing a blower. There was other data that needed changing too (scaling and such), but this isn't a GM so I won't bore you with that.
Just changing the injectors would allow it to supply more fuel, but it would be like going from a garden hose to a fire hose. The flow is higher but it's not metered. I'd think that this would throw your AFR all over the place and make your computer crazy.
My suggestion would be if you already had paid for a tune and updates were included (or relatively cheap), then you'd be smart to get it updated. If not, then I believe that it would be safe to wait until you modded your Challenger more and get it done then.
Just my thoughts. :cheers: