Air/Fuel Controller Installed

[89Vette]

We have a Rodeo ECU (Rodeo here is a pickup, not a wagon) that we are going to try. Rodeo 3.5s dont have knock sensing, EGR or variable intake runners but they do have the highest quoted factory torque/power of all the 6VE1's sold here so weez thinking maybe the Hitachi ECU has better mapping than the Delphi, plus its a completely sealed unit.

BTW...Are you certain the cam's are the same? Even within SBC's their can be cam differences which would account for rating's differences.

I'd be surprised if Isuzu left any timing on the table. OTOH, raising PE from 25% to 50-60% could be worth 1-2mpgs.

I'd bet a good 2wd/4wd switching system (or even gear box) would make as much or more difference. (maybe combine the two?) FWIW, any Jeep I've ever seen rated (and/or owned) did much better in 2WD vs 4WD mode. I could feel a difference in power as well. Just seems to be way less drivetrain loss.

Look at the difference in the 2wd vs 4wd Ford Escape's MPGs. Fairly significant in my book. (I wonder if there's any other changes in gearing, etc between these.)

[Robbomaz]

BTW...Are you certain the cam's are the same? Even within SBC's their can be cam differences which would account for rating's differences.

I'd be surprised if Isuzu left any timing on the table. OTOH, raising PE from 25% to 50-60% could be worth 1-2mpgs.

Agree. For our job#1 truck to go from 3.2 SOHC N/A to 3.5 DOHC supercharged, gain a rooftop tent windsock and STILL return nearly 3 litres/100 better economy says that the 'power under the curve' of the SC is a major factor.
Cams here are very mild. I have heard that the cams in the Axiom are better, but only hearsay nothing conclusive. We never got Axioms here anyway

I'd be a good 2wd/4wd switching system (or even gear box) would make as much or more difference. (maybe combine the two?) FWIW, any Jeep I've ever seen rated (and/or owned) did much better in 2WD vs 4WD mode. I could feel a difference in power as well. Just seems to be way less drivetrain loss.

Look at the difference in the 2wd vs 4wd Ford Escape's MPGs. Fairly significant in my book. (I wonder if there's any other changes in gearing, etc between these.)

None of ours are TOD, so are always 2WD unless selected. For fuel range calcs off-road I always use 25l/100 (10 mpg) - long way between fuel pumps in Outback Australia!

[89Vette]

I forgot to mention that knock sensors were employed largely to allow for more aggressive timing. By installing them, you give the ECU a means to monitor and back out timing when fuel is insufficient to run w/o knock (pinging). Moreover, you allow for a more aggressive timing curve since the knock sensors provide that safety net. It seems hard to believe an ECM w/o knock sensors is more aggressive than a system with them!

You sound like you'd know that.

That's why I have to wonder why cam, gearing, exhaust or some other physical configuration would account for the difference in dyno numbers.

[Robbomaz]

I forgot to mention that knock sensors were employed largely to allow for more aggressive timing. By installing them, you give the ECU a means to monitor and back out timing when fuel is insufficient to run w/o knock (pinging). Moreover, you allow for a more aggressive timing curve since the knock sensors provide that safety net. It seems hard to believe an ECM w/o knock sensors is more aggressive than a system with them!

You sound like you'd know that.

That's why I have to wonder why cam, gearing, exhaust or some other physical configuration would account for the difference in dyno numbers.

Most of the late model knock-sensed cars we have had on our dyno run right on the knock threshold stock - we have a gadget that lets the operator listen to the knock sensor in headphones during a run - there is a lot of activity from the sensor and micro adjustments going on all the time. Tapping a bolt on the head lightly with a hammer sees the advance drop and return almost instantly.

The only conclusion we can make is that the knock sensor in our Jacks is not so it can run on the raggedy edge of detonation (the ign adv behavior proves that) it is so it can 'see' crap fuel.
Rodeo is considered a tradesmans ute and would spend its life in metropolitan areas and Jackaroos are intended to go into BFN - the Rodeo lives where good fuel is the norm and the Jack could be somewhere where there is only crappy fuel. Your VX's may be programmed similarly to our Rodeos, using the knock sensor in the more 'normal' way
Recovery of a broken-down 4WD costing upwards of $10K are not unheard of here - it is possible to get a looooooooooooooong way from anything at all

[89Vette]

I'm not sure I follow. Tapping should cause retard. Without continuous knocking, it also should recover almost instantly.

What you described sounds like normal KS behavior. How are you concluding there's more room for advance (vs it already having timing table with "max" timing)?

Is their any way (with a coil pack, distributor-less system) to mechanically advance global electronic timing a couple of degrees?