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Thread: Tuning for towing?

  1. #1
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    Tuning for towing?

    The title is a bit misleading, granted, but it seems we have a few number of people who tow here, andmaybe I'll get some input I hadn't considered.

    My Dad's truck is a 454/manual trans w/OD, 4.10 gears. He tows a 24' travel trailer very occasionally. I believe its around 3000lbs.

    We converted it to TBI not too long ago ('747/$42) and I've done a bit of tuning on it, enough to get him to 128's during normal closed loop operation.

    The whole towing thing bugs me a bit though. Due to location/constraints, hooking up the trailer and datalogging isn't likely, which I'm not entirely comfortable with. I believe he towed with it in stock tune (ouch) but didn't notice any adverse affects. I'm guessing much of that was probably based on a conservative tune from GM.

    Am I overthinking this, and making an issue where there isn't one? Without a knock sensor, I'd hate for him to hit some of the grades around here, and have it start pinging on him.

    When I tuned VE, I increased the entire table proportionally, which seemed to bring VE inline pretty quickly/easily (although I had to make more increases than I expected with the only physical motor changes being an intake, cam, and headers over the stock 454) so I am *thinking* the VE changes will cover the heavier loading that will undoubtedly occur when towing and climbing steep grades. Am I right, or way off base?

    I did search, didn't see much specifically about towing, and any related pecularities with tuning for it, if any.
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

  2. #2
    EFI GearHead ! EagleMark's Avatar
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    If all you did was get the VE in line with BLM numbers it will be fine! Now if you did something drastic with spark and no knock you may have something to worry about.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  3. #3
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    Quote Originally Posted by EagleMark View Post
    If all you did was get the VE in line with BLM numbers it will be fine! Now if you did something drastic with spark and no knock you may have something to worry about.
    Actually didn't even touch spark, other than one spot where there was a "sag" in the factory timing map. I have a feeling with some time there is some efficiency to be gained there, but without a knock sensor I don't feel comfortable making changes on a vehicle I don't have time to adequately test.
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

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    well.... you could invest in something like the G3 adapter(and the EX switch) from Moates.... then if he experiences any pinging, he can switch to a different tune on the fly with one that has less advance to combat the detonation.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    True, but I'd just prefer to have the tune be an "all in one deal". He's not the type of guy to want to deal with that sort of stuff if he doesn't have to.

    If the timing is conservative enough as is, I don't think he'll have any issues. It must not be a huge issue, I didn't see any posts where people had said "when I tow my truck runs like garbage" in relation to the tune.

    He's already got an adapter/ZIF, so on his past "trips" I've just given him a spare chip with a stock bin on it in case the bin I burned has a problem we didn't notice.
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

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    EFI GearHead ! EagleMark's Avatar
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    If you didn't do anything drastic to spark he'll be fine. I'm sure you have distrbutor and initial timing set correctly? You could post the bin for a look but really think he's fine. Can he hear ping? If his hearing is good and he here's ping then fill up with higher octane till he gets home.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Where was it that I saw a cheap and small recorder to connect to the ALDL? Maybe it was so long ago that they don't make it any more. But it would work. Send Dad out for a drive with trailer and check the recording when he gets back.

  8. #8
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    Huh. Never heard of such a thing. Interesting idea, certainly simple. I've got an autoxray but pretty hard to drive and look at that thing. :)
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

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    So if I did this right, I've attached the bin he's running now.

    Only difference I saw in spark timing was a couple of degrees added around idle, but that was mainly just playing around to see what difference I could get with closed loop at idle.

    As I understand it the timing map should be relatively smooth, but I compared this against the stock ATPZ and the idle timing is all I changed.
    Attached Files Attached Files
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

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    HAHA!!!! I found one of the old GM ones we used to use. This works, although it's almost old school enough to have been on Apollo 11. The only problem is that you will have to "play" the entire recording into the laptop before you can quickly scan through data to look for problems.
    http://www.ebay.com/itm/GM-1150-OLD-...item53e85201f9

    I've spent many hours with a Tech 1 and this tool looking for problems. But other than that it looks like the only thing available now is for OBDII stuff. There is a guy building a neat recorder that saves data on a CF card but it doesn't look like they're for sale yet:
    http://www.delcohacking.net/forums/v...c2267&start=80

  11. #11
    EFI GearHead ! EagleMark's Avatar
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    That's a very good towing bin file, reason I say this is PE is set kind of rich at 12.0 to 1 and no spark added, so when power is needed you get it, not all of it but it can be sustained for very long periods without building heat, like towing a load up a long mountain pass. The other thing that stands out that this is a heavy truck bin file is PE - Enable vs. TPS % is a flat 50%. Unlike smaller trucks which have a varied table. Simple yet effective, anything under half throttle is not in PE and getting better fuel mileage, anything above half throttle is putting out power to move load down the road. This type of bin was designed to run higher engine duty cycles for extended periods.

    So to answer your question I think you can sleep at night with no worries. One thing I would suggest on this 5 speed is driving habits while towing. 5th gear is fine on flat lands or small short slopes, but when hitting a big long hill drop down to 4th which should be 1 to 1 ratio to pull hill. It will make it easier on motor and not build up heat in trans.

    I'm not a fan of the bin switching as I can make a bin do it all. But in this case, even if it were my truck I would consider a bin switch. One for what you have while towing and one for driving with no load. You could easily pick up 50 HP at WOT with some PE work and add 10% to MPG with Highway Lean Cruise in the end a much better responsive and enjoyable ride.

    Spark tables should be fairly smooth, actually all tables should be fairly smooth because the cell the ECM is reading is interpolated with the four surrounding cells to come up with amount used. Fuel is usually fairly smooth in these old ECM but spark is horrible up till newer ECMs, like look at an LT1 spark table. No wonder guys use it as a starting point for performance builds. I'm guessing the old spark tables that are horribly un-smooth are restricted to what the old slow ECM with a small bin file size could do while meeting EPA emissions, ie... it's OK here and EPA rule says it has to be here now.

    The only issue I see with your bin is you added overall 19.54% fuel to VE. Now you said this helped overall and probably did with mods in certain areas. But $42 has an issue from factory which you just made worse. $42 has a main VE and a VE 2 adder. If you add some of the cells together you get over 100% stock! It will be truncated to 100% but it real world tuning should not exceed 95 with a better goal of 90. That said I have tuned these and saw results, but looking back it was probably do to PE adjustments. Dave W talked me into adding VE2 to VE1 and using only one table and it has had better results. But really the only way to add fuel is increasing fuel pressure. Dave is a great tuner and he increases BPW when running out of fuel and then adjusting VE tables so I believe this can be done to an extent as BPW is a calculated process including fuel pressure.

    Someone had raised BPW very high with same pressure and was not having much luck getting VE in order so I went out and did some testing on my factory equipped, stock 7747 Suburban. First I checked and my VE with recording BLMs and was in order. SO I increased BPW same amount as other guy. He added like 25 to stock 135, so up to 160. My results were horrible. As expected it went pig rich at idle and as RPM increased it got better then it started leaning out to 140s. So there is a fine line of how much BPW can be added without throwing everthing out of wack... I did not test smaller changes like maybe 5 which may be doable... HTH!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  12. #12
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    That's a load of info. :)

    I may try going back in there and using Tunerpros smoothing tool on the timing table. Dad hasn't expressed any issues anywhere, but I'm sure he hasn't been in all cell's. So far just around town/cruising on fairly flat freeways. Also doesn't help that I was using TP4, and had no idea what cell he was in. Next time up it will be TP5, I think that will help substantially to see where he is sitting at unloaded cruise, etc.

    If I understand correctly (not looking at the bin now) increasing BPW is *somewhat* along the lines of changing the fuel injector lb/hr rating in a port injection setup, to under what the injectors actually flow? Again, not having the bin open, can I change the injector size in the TBI bin to say, 65lb/hr, thus "tricking" the ECM into dumping more fuel? I don't recall seeing that in there though, although I wasn't looking, since I knew the injector size should be correct.

    On the highway cruise portion...I would *think* that unloaded vs. trailering the load on the engine is so different that perhaps lean cruise could be invoked under the narrow parameters of say 50-70MPH, and very light throttle to keep from needing two bins. Basically keep it out of highway mode when trailering. Does that sound do-able? This is where the datalog showing TPS empty and trailering on the same stretch of road at the same speed would be quite enlightening.

    I appreciate you taking the time to look at that bin. I may need an actual walkthrough of the highway cruise patch application. I had no luck when I tried it last time, although I was a bit hurried.
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

  13. #13
    EFI GearHead ! EagleMark's Avatar
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    Highway lean cruise.
    http://www.gearhead-efi.com/Fuel-Inj...on-1227747-ECM

    If you really want to see where you are while data logging or playing back a log use Data Tracing, I already did most tables in $42.
    http://www.gearhead-efi.com/Fuel-Inj...unerPro-How-To

    BPW and BPC are about the same thing. No injector size parameter in $42

    Although I still don't like the idea of lean cruise while towing I could be persuaded? I think a longer time to enter, using the MAP KPA parameter to kick out under load and conservative AFR values in lean cruise MAP KPA for load just in case it could be done safely... Your idea of TPS value on same stretch of road loaded and unloaded along with MAP KPA could give you the guidelines! Same day, same weather, same driver and same MPH would be good data.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  14. #14
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    From the first thread you made, it looks like min MPH could be set to 55 (an example) to limit highway mode only to bona fide highway travel. Once loaded (towing) KPa was known, set the Max MAP for highway mode a fair bit under what loaded KPA is. I have to believe that the 3000lb weight plus aero drag is going to increase the load so much that there will be a comfortable gap between max highway mode MAP and what the MAP is when pulling the trailer. Since the datalogs I already have (unloaded) are only showing MAP voltage, I could use this chart http://injector-rehab.com/shop/mapsensor.html to determine what KPa is for a given MPH, and could use that to decide what KPa for max, correct? I don't expect the truck even unloaded to stay in highway mode under any sort of load, such as even a small hill, which is why I think this *might* work on one bin. I envision the MAP range of where highway mode is "allowed" to be a narrow window, as narrow as possible. Luckily we've got a flat highway stretch nearby, so MAP at 70MPH could be determined and used as the MAP max for highway mode.

    I think I understand the problem with trying to do this, which is if the loaded and unloaded MAP ranges overlap somewhere. So I'd need to know the loaded MAP at just over the enable MPH (in both 4th and 5th gears I suppose, the ones he can maintain that speed in) to compare against unloaded.

    He'll be making a pit stop at my place in a few days, if I get the patch applied to his bin, I could at least make a conservative effort at highway mode on one chip that he can try on his run home, and give him a non-highway chip as backup. Any pointers on how much of a change to make initially? No EGT or oil temp gauge, and I know you've got to be very careful going down this route. +3-5 tenths of a volt for AFR, a couple of degrees of timing and 30 seconds of enable?
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

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