Intake insulation experiment, FJZ80


Heretic Car Camper
Rather than a snorkle, which tends to be not reverseable, what about simply ducting the inlet to the grill area or other more ambient air source?
I'm thinking a more temporary thing, not something that is intended to deal with water crossings etc.


island Explorer
you should see an increase in fuel mileage over time right? there was a fella that did a bunch of testing on a late '80s ford truck with insulating the intake ducting etc. and saw huge improvements in mileage


It's hard to say, but if its true that you can get 1.8% change in h.p. for every 10% change in air temp, I suppose there might be a corrosponding change in fuel mileage.

Whether that change is up or down, depends on what the median testing temps was for the engine and its rating.

But if for example, there was a 20 degree decrease in temps from before, that could be a 3.6% increase in h.p. and mileage from before. With mileage being an average of maybe 12 and a maximum of about 15, that's only an increase of about 1/2 mile to the gallon, so may not be as noticable. Even with a 50 degree change, you'd be hard pressed to see a 1 mpg difference.

I could also be completely wrong that there is any corrolation between the mpg and h.p. change with air could more, who knows.

Interesting thought, though.

I am thinking about pulling off the fender to get a better look at things and look at some options for ducting cooler air without a snorkle. Maybe remove the inner fender liner.


Heretic Car Camper
Properly done all engine or chassis dyno test results are corrected to STP. So HP (actually Torque, but I digress... ) at one temp/pressure is mathematically correctable to HP (Torque) at another temp/pressure.

Cooler, denser air makes more power, but with EFI it is reasonable to say that the AFR is pretty consistant for a given set of operating conditions. If the AFR stays consistant then there can't be a change in BSFC. So the question really is, is the additional power made by the cooler air (better cyl filling, i.e. better V.E.) more than enough to offset the additional fuel needed to maintain the AFR?
Put another way, it takes X HP to travel some stretch of road or trail. You'll use as much throttle as needed to traverse this stretch at an acceptable rate. So which is a more efficient power producer, nearly closed throttle (cold air) or nearly wide open throttle (hot air)?

IMOE the more tuned the engine's power output, the more sensitive it will be to this sort of change. My 1960 VW bug barely knew the difference btwn driving next to the beach on a hot day and driving on a road thru the citrus groves at night (the driver did though!!!). Conversely my 2.0l EAO really ran hard in the groves at night, but was not nearly so enthusiastic on hot days.
With zero personal experience in one, but with various things written about them in mind I'll forecast that an FZJ80 is more like the VW than the 2.0l EAO.