4.6 3v will not add fuel at WOT

Hi there, tuning a boosted 4.6 3v and cannot get it to add fuel at WOT/Open loop. I have two logs for your perusal, one showing 20lb/min MAF and 18% injector duty and 8ms pulsewidth (and lean misfiring), and another with the MAF scaled up to 28lb/min at the same RPM and load and still showing 18% injector duty and 8ms pulsewidth (and lean misfiring). Injectors are stock 03 cobra injectors which are 42lb/min at 43.5psi but running 60psi base pressure on this car to get more out of the relatively small injectors. Data is scaled accordingly in flow rate low and flow rate high. No fuel pressure issues, have twin walbros and a -8AN feed and pressure is rock solid during this issue.
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your probably being limited by the maf failed load tables

Made some changes for you. Should take care of your problem and some more you possibly haven't noticed yet.

Thanks fellas, I didn't think I had to touch those when going from NA to boost. (Freshly installed KB kit)

Not sure I agree with raising "Max Aircharge Load". I think that moves the maximum trapped air charge line, you don't want to move it, you want to extrapolate it into boosted MAP values (ie. the engine can still only flow so much air at any given MAP vs RPM, we just have more MAP now with boost).

The manifold volume was changed to reflect the blower? Does that data come from KB?

I raised your max inferred MAP and rescaled your torque and inverse using quadratic curve fitting (not sure how accurate it will be at the top end since there seems to be a 200% load limit). Driver Demand changes will probably be necessary if you choose to use them.

There is also some important parameters missing on this one. I adjusted some of them with UDP (raised MAP delta above BP, may cause funky throttle operation until you got WOT), but there are others I would typically use to tune part throttle drivability.


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Intake manifold size doesn't really reflect the size of the manifold on the car, its a response rate tuning tool. Decipha can explain that part better. My car likes a 3 for this value.

Driver demand can be tuned separately once you have it running decently. Use this:Attachment 117248

Yeah, I was more questioning the meaning and method of adjustment that @GHuggins made to volume, if it was sourced from somewhere. I could see this affecting transient response (MAF delay, basically), but there are also transient gain tables for that. With a blower you've changed manifold volume and probably the distance of the MAF. Curious if the OEM data matches the volume of the OEM manifolds, and if that includes runner volume (probably). OP looks like airflow is being capped, not a lean transient.

I'm not sure of the relationship between ETC error and Driver Demand, DD is just the input, unless the goal is to reflect the bypass closing?

DD isn't just the driver input. Its the prediction of what the engine will be doing at a certain set of conditions. The computer thinks the engine should be doing something at a certain throttle angle, you need to give it the right numbers. Nothing to do with the bypass, that is a dynamic function.

Transient tables don't work like you would expect either. The transient fueling is governed more by your torque model.

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Originally Posted by B E N

DD isn't just the driver input. Its the prediction of what the engine will be doing at a certain set of conditions. The computer thinks the engine should be doing something at a certain throttle angle, you need to give it the right numbers. Nothing to do with the bypass, that is a dynamic function.

Transient tables don't work like you would expect either. The transient fueling is governed more by your torque model.

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Sorry, just trying to inform my understanding here. Driver Demand is the relationship between accelerator position, RPM, and requested torque. I don't understand how that's related to throttle angle until you convert torque to load (inverse table), load to air flow (speed density and MAF), air flow to effective throttle area, and effective area to predicted throttle angle. I agree that the torque values in DD should somewhat reflect the output of the engine in that if you've requested some amount of torque and hold the pedal steady, you'd probably want to follow the torque curve of the engine throughout the RPM range at that relative load range. If you're holding steady at 200ft/lbs and suddenly pull the value down to 40, the throttle will slam shut to give you what you asked for. I'm not sure if that means that DD is still any more than an input. If you ask for 200ft/lbs and get more than you asked for, then the computer made an error converting torque/load/airflow/effective area, somewhere along the way. Raising or lowering DD values would move the car away from the area that has a mismatch. That's at least how I understand it, and thought it was supported by this writeup:

https://forum.hptuners.com/showthrea...rol-ETC-System

Torque and inverse tables are just quadratic curve fits, I'm almost certain of that. Whether or not they're based on physics or a regression of "real world" data, I'm not sure. But the stock data fits way too perfectly to make me want to stray from curve fitting. On any OEM inverse I've looked at, load values are just slightly (2-5%) below the true inverse of the torque table. I've not gotten a positive result out of "tuning" the torque model aside from extrapolating for boost. My guess is this is to provide head room for the IPC, but if it's good enough for Ford it's good enough for me. Pretty sure the inverse calculator and effective area calculator do this too, which is why extreme values get smoothed out into the curve.

Transients, in my mind, have always been a product of MAF and speed density, and is pretty much the reason that inferred speed density exists and needs to be raised on boosted applications. I could see changes to the torque model affecting it if you're steering the computer away from a problem area in the airflow model, kind of like how I could swing a MAF curve with new injectors instead of changing the data.

Again, sorry, I don't mean to come off as argumentative if I am. I don't often get to flesh this stuff out and if I've got something wrong I want to correct it.

Give it a try. You aren't going to hurt anything in the tune by messing with either. I have spent a lot of time tuning my 3v, the DD tuning histogram I posted works just fine.

Again, transient tables don't work like you would expect. Transient tables as far as this operating system are concerned are nothing to do with operator input, it is an expression of how much fuel is stuck to the manifold and runner walls.