What is "raping pe or ve" and why cant I just change my pe to achieve my wot afr?

[SPRAYED 01]

I'm trying to understand full throttle tuning. I have my ve all set on my boosted 3bar speed density ls1 engine. I just added meth and need to pull out fuel. I cant seem to get a clear answer on how to go about it. I have seen the term "raping pe or ve." I don't understand what that means exactly.

If I want and afr of 11.0 with the meth spraying wouldn't I just simply command about 12.25 which is 14.7/1.2 in pe then see how it drops. If it goes to lets say 11.4 i just change pe again to lets say 1.18 and so on.

I have heard this is the wrong way to do it and just want to know why. Am I incorrect to say that when you change things in ve you are typing in a value that is airflow. So the smaller the number the less airflow you are telling the pcm so the less fuel is being delivered. If that is the case then aren't you lying to the pcm in the case of tuning with meth? You are not getting any more airflow to the engine you are just getting more fuel from a different source. So in the end does it even matter how you pull the fuel out? I would imagine its easier and better to just do the change in pe.

Im sure Im missing the big picture and that's why I posted, any explanation even really long would help.

Alex

[realcanuk]

You could do it with the PE, and many people do. The "proper" way is to set the PE to the AFR that you want (say 11 in your example), and then tune the VE and/or MAF to deliver what you have asked for.
Both ways will work if you don't mind being called a rapist.

[gippy87]

I may be way off on this but this is my understanding. What you're doing is correct its only raping when you're ve table hasn't already been set properly. For example lets say my commanded AFR was 14.6 but my ve table was 10% off across the map therefore giving me an actual AFR of ~13, instead of driving around and determining the proper values for the ve table to get to my commanded AFR i could just adjust my eq or pe table to comand 10% less fuel to get my desired afr of 14.6. This would be rape since now to get my desired AFR of 14.6 im commanding an AFR of 16.06. You want everything to match and for that you need a properly set VE table which it appears you already have.

[SPRAYED 01]

Realcanuk,
Does that still apply with meth injection? Would I just set my pe and be to command 11.0, then with meth on reduce the nunbers in the ve table in the areas on boost and wot?

[flame]

If you fudge the numbers in the pe table then you will see a lot of actual afr changes with temperature
So if you would rather retune daily then rape away otherwise tune the 've and maf and set the pe to command the afr you want

[SPRAYED 01]

Thanks flame, i was just looking for the reason why its not a good idea. If I'm just tuning the wot portion of ve and meth kicks in at 5psi. Can i just highlight 35kpa to max and about 3200rpm to max and reduce the while table by a percentage?

[PICNIC_GEORGE]

Realcanuk,
Does that still apply with meth injection? Would I just set my pe and be to command 11.0, then with meth on reduce the nunbers in the ve table in the areas on boost and wot?

VE is a measure of airflow, it has nothing to do with what fuel you're using. If the VE table is correct(along with the other tables), then all you need to change is commanded whichever way you do that.

[BigMike42]

It's a horrible method because using just PE has such low resolution. Meaning, you are literally only tuning the car for a handful of maf frequencies (the ones that are being hit THAT day and that day only in PE). As soon as more air comes in from a colder day, your WOT afr will be way off.

I don't see why some shops do this. It's no quicker than just using the maf. Tuning the MAF wot is just as easy as doing the PE rape method. Both are single row tables... A 4th gear WOT pull on the dyno will hit every single maf cell you need at WOT.

[jimmyblue]

Did your Mama ever say, "two wrongs don't make a right"?