HPT questions

[NYer]

I have a couple simple - medium level questions about using HPT is there anyone who wouldnt mind a 15 minute phone call to talk about hpt tuning.

[Phantom]

I'm not sure if I can help but what are you trying to tune?

[NYer]

Well I have a number of questions I thought phone would be way easier

Dilema on my car - My car runs very well and my timing is a nice 18* at WOT with 0 kr not even a blip,
but 2 problems
1 is minor my mpg suck and I think that is just part of extra performance but maybe not see problem 2

2 This is where I need help right before entering PE mode mt LTFT will hit like +6.0 - 7.0 and then ofc wot and pe it locks in at these values. I think that means my situation is lean and the comp is reacting by dumpin fuel at it? (or do i Ihave it backwards)
either way it was nice today 50* so I did massive scannig and testing and I tried a few things
-I tried changing PE fueling (more and less), although since I dont have kr and the car is driving well I didnt think this would fix ltft and it didnt
- I tried playing with maf curve (up and down) this changed some of my non PE driving but more times than not I didnt like the way it affected the car and my LTFT still lock the same at PE perhaps I really have to find the part of the curve before it hits PE and play with that part in particular?
- I didnt really know what else to mess with safely and I like to learn as I go so I still have a ton of data to analyze from what I did change. What would be the easiest way to change that trim to get it a little closer to 0 as it enters PE? (Do I need to start over at VE tuning?) I didnt think I would? any advice owuld be appreciated

[danthurs]

When you go WOT your LTFT should be locking in at zero. If not your MAF curve needs work. Start out with a good VE tune to get your LTFT close, then tweak the MAF curve in the areas that are needed until you have good LTFT. Then you can work on your PE tables. If you don't get them worked in first, your just fighting.

[NYer]

Right I know these things for sure.

I tried moving the maf curve up and down and it did not affect the LTFTs locking in, MAybe Ineed to restart with VE again !!!

[danthurs]

You are correct. Get your LTFT within +5 and -5 of zero on the VE tune. Then adjust each part, idle, cruise, and WOT on the MAF curve. Do the WOT part with a stock PE table, then adjust the PE so your narrow band is about 920-940 when at WOT

[Foghorn]

Don't forget that anytime you change the fueling (such as a MAF change), you must reset the fuel trims, then go through a driving cycle to learn the trims again.

The PCM uses the last LTFT value before entering PE mode as an 'adjustment factor'. If the LTFT locks in at -5, that means the trims were rich and the PCM was leaning them out by 5%. If the LTFT were +5 then the PCM was adding fuel.

It's not a 'must' to lock the trims at 0 in PE mode, so long as the value is consistent. That said, it's more realistic if you try to acheive 0 because then if your target AFR in PE mode is 11.8 yet the LTFT is -5, you would have to change your target to 11.2 to get the expected AFR.

If your fuel economy is suffering but your have 0° KR then perhaps you're a bit rich? I always liked to see the odd bits of KR, that way you know the limits.

Cheers,

[NYer]

That makes sense because it does lock very consistent. and my narrowbands are a nice 940ish at WOT.

I was getting some kr but played the PE table a little and now I get 0 kr at all and got timing up to 18 not sure how far to push it.

Part of me says if it is at 0 kr keep going try 19 or 20*
part me says fuk that get rid of the ltft issue and start over

I just hate to start over because the car is running NICE and pulling HARD maybe i will take it to the trrack then start ve tuning all over