K3500 Gearing

Discussion in 'Towing' started by oldbrown, Mar 8, 2020.

  1. Pinger

    Pinger OBS Enthusiast

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    The only manufacturer I am aware of using water injection is BMW on one (or some) of their M Sport models. They source the water from the air-con condensate.
    I think one reason water injection is shunned is that it would require an anti-freeze additive in cold climates and they don't want their customers having to mix it or handle it if it is methanol. I am just guessing on that though.
    Maybe if the emission tests were conducted at high loads the fuel cooling would end but as the testing is done at very low loads, the manufacturers can do what they want outwith the test regime - and leave the end user with the fuel bill (and diluted engine oil). Rowing back on the fuel cooling could force them to lower CRs and lose economy across the board.
    Fuel cooling though is one reason why the downsized turbo engines don't always deliver the expected fuel economy gains in real life running.
     
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  2. andy396

    andy396 GMT400 Enthusiast

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    We're remapping the stock ECU, as in my case, or an upgraded '0411 ECU as in most everyone else's case. It's a parameter within the tune that can be monitored and adjusted for when and how it comes in based on other parameters and to what extent it adjusts the A/F ratio. I can also monitor it with my butt sensor ;), I have it set such that when it "kicks in" I can really feel and hear it. It's kind of like the secondaries opening up on an old quadrajet. Mine is set for a 0.5 sec delay and ramp in when the throttle is over 60%. Depending on rpm and throttle position mine goes as low as 12.5:1 AFR, which is up from the stock tune which waits for a throttle position of greater than 60% for over 60 seconds before it more slowly ramps in, and when it does ramp in it goes all the way down to 11.5:1 AFR.
     
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  3. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    There are other parameters we can play with along with PE, for example, AE (Acceleration Enhancement), like the accelerator pump on a carb, SA (Spark Advance) Launch Mode, which advances the timing based on MAP and RPMS (like vacuum and centrifical advance). Here's a snip of them from my EBL Flash2 .bin file as an example...

    upload_2020-3-25_12-39-10.png

    One thing though, if you jack thes up too much, especially AE, you'll get sh*t for MPG, LOL. Sorry for jumping in.
     
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  4. andy396

    andy396 GMT400 Enthusiast

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    I haven't messed with the OBD1 stuff at all yet. It's cool to see the potential that exists there as well. OBD1 just sits in the big ol' shadow of the '0411 and often gets overlooked. I'm still holding onto the '95 7.4L ECU and throttle body just in case a project comes along.
     
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  5. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    Yeah my 7747 ECM from 88 ran at a buad rate of 160, the EBL is 8192 (like the 7427) with extended tables for SA up to 6375 RPM, VE up to 8000 RPM, can run up to 3 bar boost as well as N2O. The only issue is it can't run electronic trans, you have to run a parallel controller. Fun stuff!
     
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  6. Pinger

    Pinger OBS Enthusiast

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    With software on a lap top via OBD port? PW TBI - is that how you do it also?

    This stuff has me a bit worried re running on LPG. As far as I know the LPG electronics richen above 4000rpm but not on load (ie TPS voltage). When you refer to ''throttle position of greater than 60%'' is that the voltage reading from the TPS eg 0.6 x 4.0V = 2.4V? (When WOT at TPS gives 4.0V). Is it 60% at all/any rpm?

    60% of WOT at 60% of Pmax rpm is pretty much full throttle as the engine sees it. 59% of WOT at 59% of Pmax rpm is pretty much the same except no PE. If say, Pmax was at 6000 then 60% of that is 3600rpm. At that rpm, around 60% of WOT is required for full torque. But I have no enrichment until 4000rpm and then it lacks the cooling effect of liquid gasoline. Just how dependent on PE (for reliability) is the L31? Or is it just a power thing?

    The only option I have while driving for enrichment is ensure rpm is above 4000 under heavy load - unless it can be reconfigured via the LPG ECU. (The LPG ECU reads TPS but only as closed or open - and really only as part of the switchover between fuels strategy).
     
  7. L31MaxExpress

    L31MaxExpress I'm Awesome

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    Problem with water cooling vs fuel cooling has to do with catalytic converters. The catalyst require a richer mixture to eliminate oxygen flow into them and snuff out the reaction which keeps them cooler at WOT. Water cooling will help keep the cylinder cool but the cats not so much.
     
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  8. L31MaxExpress

    L31MaxExpress I'm Awesome

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    Many of the propane setups I have seen enrich automatically under low intake vacuum. The older setup I messed with for TBI had a PWM vacuum solenoid in the line to the diaphram that controls the diaphram that controls the fuel orifice.
     
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  9. Pinger

    Pinger OBS Enthusiast

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    Mine is 1999 SFI but for the LPG (propane) system, there'd be no real difference.
    The LPG system I have is closed loop single point. It's a bit of everything. Uses a vacuum signal from venturi (mixer) as does a carb but fuel trim is via a stepper motor controlled valve in the LPG line between reducer/regulator and mixer which reads from Lambda sensor.
    So there's mixture control which is air flow dependent (load) and electronic control via the stepper motor which is guided by Lambda sensor readings - and a degree of pre-programmed enrichment (apparently).

    Without PE, ignoring the cats for now, will high internal engine temps show on the coolant temperature gauge? Or only after it's gone bang?
     
  10. L31MaxExpress

    L31MaxExpress I'm Awesome

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    I doubt it will go bang because propanes high octane would be very hard to detonate. That being said it could absolutely cause the rings to butt which would destroy a piston or the exhaust valves and seats to burn because of the high combustion temp. Best way to monitor what is going on would be an EGT gauge.
     
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