my mods, what tune, sct tweecer or pms

Discussion in 'Fox 5.0 Mustang Tech' started by kickin_camaros, Mar 21, 2007.

  1. I have a 1989 gt, as far as mods go i have moroso in fender, 70mm maf, 70mm tb, perfromer upper/lower, e-303 cam, bbk full length headers, off road h-pipe, no cats/smog, spintec mufflers, spec racing clutch, 4:10s, and a 100 wet shot of nitrous. I plan on getting either 24 or 30lb injectors, a 255lph pump, and a fpr, and well i feel that a good tune would help bring alot of these mods together and was wondering what you guys think would work best on my car, is anybody using sct's chip, do you like it? also i live in denver and my track is ay 7000 ft. altitude if that makes a huge difference between which chip, any help would be greatly appreciated
  2. I am not too familiar with the SCT tunes, but you would need to hit a dyno, correct?

    The big concern I would have with your combo is the N2O. The rest of your setup shouldn't 'require' a tune (but some have reported drivability issues with the E303 cam).

    Any of the tuning systems you mentioned will get the job done. If you have time to learn how the Ford ecu was programmed (and the patience) then the TwEECer RT is a cost effective choice.
    If you just want to plug in the tuner and start making changes, then the PMS may be a better option. (you will still have to do some reading, but not as much as with the tweecer)
    If you don't have the patience/time to tune the car yourself, then hit the local dyno tuner and let the Pro's do it.

    Notice there was no mention of your *current* tuning knowledge. You can learn what you need to know if you dig through the internet...

    Hope that helps,
  3. for the tweecer you need a laptop correct? where can i find more info and prices on the pms, also my car is it 14 degrees of timing and the tps senser is at .93 volts. the sct is a chip that is installed in your computer relkatively easily and they custom burn it for you based on your mods and you can get as many tunes as you want and switch from tune to tune with a small dial and the chip runs around 330 all saide and done with 3 tunes
  4. If the SCT tune is done on a dyno, then I would say go for it.
    If they create a tune then mail the chip to you, then it may not work very well, it's hard to say.

    You will need a laptop for the RT, if you want to datalog.
    Check Anderson Ford for the PMS info.

    Setting the tps to a specific value is a myth. As long as the tps is between .6 and 1.2v, the computer won't care what the actual setting is.

    With any of these tuning systems you will be setting the dist back to 10* of advance, and then make timing changes in via the tuner.
    This is a much improved way of setting timing.

  5. I know this is old, but I just wanted to say that actually this has a huge effect on the throttle response.
  6. 87pony I agree completely on the setting of the TPS. it should be between .92 and .99 as the computer needs to understand where the throttle position is at start-up. Additionally, the computer reads part throttle at 1.1 or 1.0 volts or something every close to that, so if your TPS is reading .6v then you need to open the throttle to 1.x volts before the computer will understand that the throttle is open, thus changing from CL idle to CL pt (part throttle) and using the appropriate tables or values.

    As for the tuners, if you want to do it yourself, get the moates Quarter Horse. Don't bother with the tweecer as that's over priced. For the same amount of money as the tweecer RT you can get the Quarter Horse and wide band gauge. I sold my tweecer for the QH and the logging is the most impressive part along with the update capability of the chip.
  7. Have any proof to support that???
    Or just some seat of the pants 'data'?

    I will provide the logic that the Mustang ecu's utilize regarding the TPS and how the signal is used later today...

    What the TPS value is at idle is trivial, as the ecu 'resets' what it calls the baseline/idle value.

    Base idle value is called RATCH in the programming. RATCH is constantly looking for a new lower TPS value to call the baseline/idle setting.
    It doesn't matter what the actual value is at startup....

    Part Throttle is triggered by a change in RATCH, not by an absolute TPS value.
    I think it was .1v above RATCH, but that is from memory which is kinda hazy these days...

    If you guys want to read up on it, search here for the 'GUFB' document.
    I'm pretty sure I've linked to it before...
  8. I have the document and have read it for many different things. you are correct as ratch is a variable that is determined by the computer.

    Part throttle is a variable of .0400 volts for a breakpoint above the current CT TPS value which must be between .5 and 1.25. Ratch is used for setting a variety of items including; dashpot, tip-in and a few other items.

    So setting the TPS lower in theory to .55 then you have a larger usable range of throttle as the computer will read to 5v for the TPS as opposed to setting the TPS to 1.25v. you can then change this with chips like the tweecer and QH to modify it. But the ratch is something that can't be set other than by the computer, but usually the value for throttle items like idle and so on are a combination of ratch, TPS and other items.

    So i suppose it doesn't matter what the TPS value is (so long as it's between the values listed above), but .95ish is in the middle of the range so that is perhaps the reason for setting it to that value, not sure.
  9. You've read the GUFB on the TPS....

    So, why do you think it matters what the 'usable range' is when WOT is triggered based on a change from RATCH?
    (this works the same way part throttle does)
    2.7v above RATCH triggers WOT... It makes NO difference what the actual value is.

    Exactly my point.
    Setting the TPS to a precise value doesn't matter. :nice:

    However, you say that and then continue to recommend a SPECIFIC value.:eek:

    Here is a question for you...
    What is the range of RATCH values that the ecu will accept as 'normal'?
    In other words, what range of RATCH values won't trigger diagnostic codes?
    Because reality of it is.... if there aren't any TPS codes, then the ecu doesn't care what it is set to.
  10. This is the RATCH algorithm that is used or the RATCHET algorithm:

    The lowest filtered EGR position EOFF is controlled by the following logic:

    EGRBAR < EOFF ------------- |
    CRKFLG = 0 ---------------- | AND ---| SET EOFF = EGRBAR
    (RUN or UNDERSPEED mode) |
    APT = -1 ------------------ |
    (closed throttle mode)

    As for the actual values that will trip a code I can't seem to find that.

    Also, the idea of setting the TPS value to .92 was only because it's close to the middle of the range between .5 and 1.25v. Which as stated before that the computer values will be tripped if higher than 1.25v and lower than .50v. Then according the document this range value for the TPS are set to prevent issues with the fluctuation of vehicles during production runs, which is also the reason for the implementation of the RATCHET algorithm.

    So yes in reality it doesn't matter what the TPS is set to so long as it's between .5 and 1.25v according the stock A9L GUFB strat. I just suggested that to be something in the middle of the range. Throttle response has nothing to do with the TPS setting and I was incorrect with stating that as PT is set for the TPS moving .04v. So what ever the TPS/Ratch is defined as, once the TB blade moves enough to trip .04volts PT will be activated from CT.

    I'm sorry if I started an argument as I didn't mean to.
  11. My apologies if I came across as 'arguing'...
    That was not my intent, but I know I can come across that way.

    Discussions like what we just had help more than just you and I, as there will be others reading along, and learning from it.

    It looks like logic you posted above is for the EGR RATCH?