Full-Throttle Inconsistencies
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Joined: Oct 2003
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From: Azle, TX
Full-Throttle Inconsistencies
Sorry for the long thread, but this has puzzled me for a while now. The following background may date me somewhat, but my original HotRod roots are as follows.
In the days of yesteryear, you bought a late-sixties / early seventies muscle car. Made it breathe better by opening up the intake and exhaust (carb, intake, cylinder head porting, cam, headers), added a hotter ignition and re-curved the distributor, then start working of the tranny and traction devices cause you were going to need 'um.
The same kind of logic exists today for in the world of fuel injection, computer-controls, and emmisions requirements but its much mote "hands-off" to the general shade-tree mechanic.
OK, OK, I'll get to my question. I do not understand why my truck responds the way it does during WOT. I travel a desolate farm-to-market highway home from work everyday. After one of the 4-way stops, is a decent straightaway with a right hand curve after. Just before the curve at exactly 2-tenths of a mile is a very distinct expansion joint in the road. It make a very audible "tha-tunk" sound when you hit it. I have used this stretch of road as a poor-man's gauge to determine acceleration improvements (butt dyno) by recording the MPH differences at this joint in the road. Scientific? No. Reliable? Maybe, but better than nothing.
Scenario #1: If I floor-it from a dead stop and get good traction with no wheel spin, the truck lunges forward, pulls OK into second gear shifting at about 5200 RPM. The engine seems to load-up a little but pulls OK until about 4000 RPM, then it drops-off and mainly screams to the the next shift point. The MPH readings are very consistent (+/- 2-3 MPH) with this technique, even with a small amount of wheel spin.
Scenario #2: If I avoid flooring-it and judiously apply the throttle before going to WOT, the truck pulls like a banshee all the way to the 5200 RPM shift, sometimes getting a scratch during the shift to second. The MPH readings are consisently 8 - 10 MPH higher, sometimes as much as 12 MPH, than Scenario #1. Again , the MPH readings are very consistent (+/- 2-3 MPH) with this technique, even with a small amount of wheel spin.
Any idea why this happens? I know its not my imagination. Is the computer / MicroTuner trying to accomodate for the 5000 lbs behemoth that I am launching from a dead-stop to avoid detonation? Perhaps this is a normal response under this demanding condition.
Thoughts or comments???
In the days of yesteryear, you bought a late-sixties / early seventies muscle car. Made it breathe better by opening up the intake and exhaust (carb, intake, cylinder head porting, cam, headers), added a hotter ignition and re-curved the distributor, then start working of the tranny and traction devices cause you were going to need 'um.
The same kind of logic exists today for in the world of fuel injection, computer-controls, and emmisions requirements but its much mote "hands-off" to the general shade-tree mechanic.
OK, OK, I'll get to my question. I do not understand why my truck responds the way it does during WOT. I travel a desolate farm-to-market highway home from work everyday. After one of the 4-way stops, is a decent straightaway with a right hand curve after. Just before the curve at exactly 2-tenths of a mile is a very distinct expansion joint in the road. It make a very audible "tha-tunk" sound when you hit it. I have used this stretch of road as a poor-man's gauge to determine acceleration improvements (butt dyno) by recording the MPH differences at this joint in the road. Scientific? No. Reliable? Maybe, but better than nothing.
Scenario #1: If I floor-it from a dead stop and get good traction with no wheel spin, the truck lunges forward, pulls OK into second gear shifting at about 5200 RPM. The engine seems to load-up a little but pulls OK until about 4000 RPM, then it drops-off and mainly screams to the the next shift point. The MPH readings are very consistent (+/- 2-3 MPH) with this technique, even with a small amount of wheel spin.
Scenario #2: If I avoid flooring-it and judiously apply the throttle before going to WOT, the truck pulls like a banshee all the way to the 5200 RPM shift, sometimes getting a scratch during the shift to second. The MPH readings are consisently 8 - 10 MPH higher, sometimes as much as 12 MPH, than Scenario #1. Again , the MPH readings are very consistent (+/- 2-3 MPH) with this technique, even with a small amount of wheel spin.
Any idea why this happens? I know its not my imagination. Is the computer / MicroTuner trying to accomodate for the 5000 lbs behemoth that I am launching from a dead-stop to avoid detonation? Perhaps this is a normal response under this demanding condition.
Thoughts or comments???
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Joined: Mar 1998
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From: Virginia
Well, this could very well be torque management - if you do not have one of our *custom* tunes (for example, if you're using the 1715 Superchips Max Micro Tuner instead of our Troyer Performance *custom* tuning) that's most likely what's actually going on. In our custom tunes, in what we call our "maximum performance" tunes, we usually knock that out if the vehicle's mechanical configuration is such that we feel that can be done without compromising transmission durability - so this is just one of many things we do differently in our custom tuning. Now it's also possible that even with our custom tuning, if the vehicle's mechanical configuration is such that we didn't feel that could be done without compromising tranny durability, then we'll leave that in there. But I'm guessing this may be the "culprit," so to speak, if I understand what's going on correctly.
The torque management gets more and more pervasive with each successive model year in these trucks (and many other vehicles) - it's all part of the automakers efforts to make trucks & SUV's feel "smoother" so that more female buyers will be attracted to them - literally. Then there are some configurations where TQR (torque management) is implemented not just for "smoothness", but also for purposes of transmission durability.
On the transmission durability side of things, just to give you one example of how TQR can give vastly difference performance making the same basic type of move but using different driving techniques...................... in the 2004 & up F-150's which use the 4R75-E tranny (the newer version of the 4R70W), let's say you're just cruising easy in the 45-70 mph range, so you're up in Overdrive (4th gear) - but then need to pass someone on a 2-lane road, like a truck, and you need to get around them quickly.............. - well, you'll get more power & pass quicker if you do that 4-2 downshift by first disabling Overdrive by quickly tapping the O/D cancel button, and then punch the throttle to effect an automatic 3-2 downshift at full-throttle and take off. But when you just nail the throttle to the floor & make the transmission do an automatic 4-2 downshift, in the 5.4 3V you'll lose literally 50% of your power when it downshifts from Overdrive (4th gear) down into 2nd gear that way! The PCM does this to protect the tranny, as the 4R75-E's tend to bang a 4-2 WOT downshift and more components (clutches) are involved in doing a 4-2 downshift compared to say, a 3-2 downshift. So Ford does this (reduces power by about 50% for several seconds) to protect the transmission from a full-throttle full-power 4-2 downshift, as they should.
When we do our custom tunes, in writing our documentation that we send to each of our custom tuning customers (we started writing about this aspect specifically in our supplemental docs in our custom tunes a few months ago), we specifically tell the vehicle owners about this, and how not only do you get better performance doing a 4-2 downshift for rapid acceleration by first tapping the O/D cancel button and *then* nailing the throttle, way, but also how that's better for the transmission to do passing moves that way, too.
At any rate, what's happening sounds like it may well be simply different TQR strategies for that slightly different scenario - assuming this isn't simply a calibration difference in the torque converter's lockup schedule, or something else going on. many times what you are describing can simply be how the torque management strategy is implemented in different ways in "slightly" different scenarios in the same gears.
The way to have this taken care of is to have us do a custom tune - if you'd like to call us at our number listed below with your F-150's computer code, I can take a look inside your vehicle's program & let you know if that is what's most likely going on, and whether or not that can safely be eliminated in a custom tune with your vehicle's exact configuration & transmission - or whether your tranny needs a modification to be able to do that without compromising durability, etc., etc.
Just give us a call to go over any of this.
The torque management gets more and more pervasive with each successive model year in these trucks (and many other vehicles) - it's all part of the automakers efforts to make trucks & SUV's feel "smoother" so that more female buyers will be attracted to them - literally. Then there are some configurations where TQR (torque management) is implemented not just for "smoothness", but also for purposes of transmission durability.
On the transmission durability side of things, just to give you one example of how TQR can give vastly difference performance making the same basic type of move but using different driving techniques...................... in the 2004 & up F-150's which use the 4R75-E tranny (the newer version of the 4R70W), let's say you're just cruising easy in the 45-70 mph range, so you're up in Overdrive (4th gear) - but then need to pass someone on a 2-lane road, like a truck, and you need to get around them quickly.............. - well, you'll get more power & pass quicker if you do that 4-2 downshift by first disabling Overdrive by quickly tapping the O/D cancel button, and then punch the throttle to effect an automatic 3-2 downshift at full-throttle and take off. But when you just nail the throttle to the floor & make the transmission do an automatic 4-2 downshift, in the 5.4 3V you'll lose literally 50% of your power when it downshifts from Overdrive (4th gear) down into 2nd gear that way! The PCM does this to protect the tranny, as the 4R75-E's tend to bang a 4-2 WOT downshift and more components (clutches) are involved in doing a 4-2 downshift compared to say, a 3-2 downshift. So Ford does this (reduces power by about 50% for several seconds) to protect the transmission from a full-throttle full-power 4-2 downshift, as they should.
When we do our custom tunes, in writing our documentation that we send to each of our custom tuning customers (we started writing about this aspect specifically in our supplemental docs in our custom tunes a few months ago), we specifically tell the vehicle owners about this, and how not only do you get better performance doing a 4-2 downshift for rapid acceleration by first tapping the O/D cancel button and *then* nailing the throttle, way, but also how that's better for the transmission to do passing moves that way, too.
At any rate, what's happening sounds like it may well be simply different TQR strategies for that slightly different scenario - assuming this isn't simply a calibration difference in the torque converter's lockup schedule, or something else going on. many times what you are describing can simply be how the torque management strategy is implemented in different ways in "slightly" different scenarios in the same gears.
The way to have this taken care of is to have us do a custom tune - if you'd like to call us at our number listed below with your F-150's computer code, I can take a look inside your vehicle's program & let you know if that is what's most likely going on, and whether or not that can safely be eliminated in a custom tune with your vehicle's exact configuration & transmission - or whether your tranny needs a modification to be able to do that without compromising durability, etc., etc.
Just give us a call to go over any of this.
Thread Starter
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Member
Joined: Oct 2003
Posts: 51
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From: Azle, TX
Thanks for the feedback Mike T.
I (in fact) do have the 1715 and have updated my signature accordingly.
This topic is not a big issue with me since I know how to overcome the TQR (torque management) as you are suggesting. Implementing TQR for the durability of tranny makes sense, but smoothness for the female crowd is kinda' over-the-top in my book. Its a TRUCK for Pete's sake!!!
Mike - I'll holler at you sometime this week about details of a possible custom tune.
Cheers!
JPTEX
I (in fact) do have the 1715 and have updated my signature accordingly.
This topic is not a big issue with me since I know how to overcome the TQR (torque management) as you are suggesting. Implementing TQR for the durability of tranny makes sense, but smoothness for the female crowd is kinda' over-the-top in my book. Its a TRUCK for Pete's sake!!!
Mike - I'll holler at you sometime this week about details of a possible custom tune.
Cheers!
JPTEX