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Typical Hesitation After Shift.. what can be done?

Discussion in 'Tuning À la carte' started by Rossim22, Feb 6, 2012.

  1. Rossim22

    Rossim22 New Member Established Member

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    During wot runs on my 03 cobra, when I shift and continue to floor the pedal, the car falls on it's face. Most do the pprv delete but many say it depends on the tuner. My tuner has great customer service and has been trying to take care of the issue for a little while now. What can be done to the tune to avoid this issue? I believe he's using quarterhorse and EEC editor?
     
  2. 01yellercobra

    01yellercobra AKA slo984now Established Member

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    I know for SCT there's a table for the fuel pressure. It has to be clipped because the stock values are way too high. I can't remember which table it is off hand. But your tuner should be able to figure it out.

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  3. xenodragon

    xenodragon New Member Established Member

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    Theres two things you can do

    1. Get the tune fixed
    2. go return sytle fuel system

    I had this problem and went to 3 different tuners, and none of them could fix it. I said screw it and went return. 100000x happier with the setup. Eliminates so much crap from the cars fuel system and allows for high horsepower applications. I would honestly suggest for everyone to go this route. However, be warned your MPG will be drop alot.
     
    Last edited: Feb 6, 2012
  4. 01yellercobra

    01yellercobra AKA slo984now Established Member

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    I had the shift hesitation, but clipping the fuel pressure fixed it.

    Going return style shouldn't affect your mpg. You're using the same amount of fuel. It's just a slightly different delivery style.

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  5. flamedstang95

    flamedstang95 Gettin' Dirty Established Member

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    He's just having so much fun with it now, that's why his MPG's have dropped...LOL
     
  6. 01yellercobra

    01yellercobra AKA slo984now Established Member

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    Lol. I didn't think of that.

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  7. Black*Death

    Black*Death Sleeping Established Member

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    What do you mean by "clipping" the fuel pressure? I haven't heard that term before.
     
  8. 01yellercobra

    01yellercobra AKA slo984now Established Member

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    Bit of a read, but it's what I followed with mine:



    Pretty scary, huh? The military figured out the electronics were reacting too quickly to the pilot inputs. Pilots were used to slow acting hydraulics and cable controls. The control systems were working too good!! The solution….. deaden inputs to the electronic control system. Once the electronics were slowed down enough to act like mechanical controls the system worked fine. That’s oversimplification of the whole problem but that’s it in laymen terms. Now, the way I see it is the pcm is overreacting to an unusual event in the fuel system. It’s been explained many times here so I won’t get long winded. Essentially there is a huge spike induced because the injectors are suddenly shut down because the driver jumps off the pedal. The fuel system is doing it’s job. Supplying huge volumes of fuel and high psi. The pcm shuts down the pumps because of way way too much pressure seen by the frpt.(albeit very high and for a very short time) Meanwhile driver grabs next gear and slams the pedal down making the injectors/engine want a lot of fuel. Uh oh the processor shut the pumps down. Now the fuel system has to regroup and start supplying enormous amounts of fuel. Fuel pumps have to spool up and the pressure needs to build again. All this takes time. The root of the problem is the pcm overreacting to the initial pressure spike. In a way the same as the fly by wire on the F8-C. So how do you deaden this input? We use a combination of things. Some have already been tried but not all of these together that I know of. In reality we are putting a muzzle on the fuel control system so it does not over react to the initial spike. First ( and probably most importantly) we clip the pressure sensor transfer function. (this is the pid we had to have Diablosport add). When you think about it if a car makes 17 lbs boost and you want 39 psi delta you never really need more than 56 psi absolute rail pressure. So in that case we would clip the pressure transfer function at about 60 psi. If you make more boost make the clip a little higher. ( say 22 lbs boost…. 22 boost + 39 delta = 61 absolute rail pressure….. I’d clip it at about 63 or 64 to give it a little room) The program has it clipped at 78, that’s 15 psi too much even for 22 lbs boost. This way even when this huge spike happens the pcm never sees it. That’s the biggest part of the battle. That’s why removal of the pprv helps. The pcm sees the spike and reacts but the extra fuel is stuck in the line for that split second and by the time the pcm does it’s thing the pumps are back on and everything is cool again. (This really is a very very small window that is causing this to happen.) That’s why, depending on driving style, some experience it worse than others. It depends on the speed of your go pedal foot. I’m not a fan of pprv removal. (flame away I’m speaking from MY experience) The pprv really helps if you don’t allow the fuel control to overreact. The initial spike is there but not as long. Plus cold start is better (no big deal really) The second way we muzzle the fuel control is with the PID control. I put the proportional at zero. (yes I said zero) then we cut down the integral to some where around .1074 . Leave the derivative at zero. We have datalogged this and the fuel system is stable. We have big fuel supplies in these vehicles to make that kind of power. You don’t need to micromanage (remember the F8-C). Make sure your MAP sensor max counts are set to 1023, adjust your load with failed maf table up (this is one of the things the pcm looks at during sudden transitional changes) I have attached an excel file to give a good starting point for most higher boost cars. The main thing is your loads are going to be higher so make them closer to reality. ( they really don’t have to be perfect) and lastly ( in my opinion the least critical since it’s adaptive) tweak your fuel pump voltage table. On some cars I don’t even mess with it. That’s it in a nutshell. Clip the pressure transfer function, lightened the PID control, get your load with failed maf close to reality, max out the map ad counts, and fiddle with the voltage table. What I feel we are doing is basically putting a muzzle on the fuel system so it doesn’t over react. This has worked on many of our customers Cobras. We have not had any problems with it. If you need any help with this shoot me a pm or email me …. [email protected] We can custom tune your car or even send a mailorder tune with the fixes in it. Hope this helps and sorry to cause such a stir. (some of you take things way too serious, you should get a hobby J/K)
    Have a great weekend.
    Attached FilesTerminator failed maf table.xls (13.5 KB, 54 views)
    Heres oringal thread link>>>>

    Mustang Forums and Ford Performance Forums at ModularFords


    Also from eric brooks>>>>>


    This procedure assumes that you have a decent fuel pump voltage table that is pretty close to what is really needed.

    You need the engine at a moderate load, somewhere around a load of .4 and around 2000 RPM is a good place.

    Set all the PID gains to zero.

    Slowly raise the proportional gain until you see fuel pressure going up and down in a sine wave format. What you need to do is take data over about 30 seconds of fuel pressure. Then you need to take the data and calculate the RMS error (Root Mean Squared). If you want to know what RMS is go to this link http://www.easycalculation.com/stati...ean-square.php, if you just want to calculate the RMS value, you can go to this site, http://www.easycalculation.com/stati...ean-square.php. This site just allows you to plug in the numbers seperated by a comma and it will calculate it for you.

    You want to keep increasing the Proportional gain until you get an RMS value of 1.5 PSI. This does NOT mean it's a 1.5 PSI peak to peak, this means an RMS value of 1.5.

    Once you are satisfied you have a Proportional gain that results in a RMS value of 1.5 you need to calculate the period of the oscillation. The Oscillation period is the time in seconds it takes for the pressure to complete one wave. This means the pressure goes up, then goes down and then goes back up to where it started. This time should be about .15 to .25 seconds.

    For the Proportional Gain you want to multiply the value that resulted in the RMS value of 1.5 by .3. So if you came up with a value of .4, you would then multiply it by .3 to get a proportional gain of .12.

    For the integral gain you use this equation (proportional gain/(.5*period)). So if you had a period of .2 and a proportional gain of .12, the integral gain is .12/(.5*.2) or 1.2.

    The derivative gain is equal to (.125*period)*integral gain. In the example so far we would get the following (.125*.2)*.12 or .003.

    So, for the above example you would have a proportional gain of .12, an integral gain of 1.2 and a derivative gain of .003.

    There is a lot of math and theory behind the above equations but I'll spare you that. If you are interested in knowing the theory it's based off of the Ziegler-Nichols Method. You can find the theory behind this method in Control and Dynamic Systems, Addison-Wesley Publishing Co. 1972.

    This should clear things right up.
     
  9. Swervedriver

    Swervedriver Member Established Member

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    I like to keep the car open loop above 4k rpm and blend the throttle position to be less at each rpm increment below that.
     

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