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This mod will only give the MPG performance boost in moderate temperatures. Too cold and MPG suffers in all cases. And like with all hyper MPG driving it cannot make up for a heavy right foot. It will in moderate temperatures and with hyper MPG driving techniques _help_ retain up to 10MPG that would otherwise be lost to the colder weather.
Begin original post:
The radiator block and MPG improvement has been discussed many times in here. I too have used the above block but removed it early this June with the onset of summer and temps in the high 80's - low 90's. Several other type radiator blocking schemes that have been presented in here appear much more complex, difficult to install and remove.
Now that outside temps have moderated to low and mid 80's I reinstalled it. On my well worn route home today - voilà +10MPG with ECT readings approaching 203F (still safe, fans auto on @ 205F).
Simply slide the above size piece of plain cardboard long length horizontally in between the radiator and AC condenser. AC users should not use this since it also decreases air flow across the condenser, increases compressor load and reduces AC efficiency. Insighters in warmer climates should delay this until daytime temps moderate to the mid 80's or if you frequently get into heavy stop & go traffic such that the auto stop function is "used up".
I would also recommend that unless you have the means to monitor your engines temp separate from the dash gauge (e.g. a scan tool) that you carefully consider the risk.
My summertime average for my afternoon ride home without the radiator block was in the upper 70's to low 80 MPG. Today's MPG (under ideal conditions of weather and traffic) was 90!
I'd like to hear other field test reports!
[Edit 2/17/07, Summarizing the design and cautionary considerations]
1) The amount of blockage can be varied according to the outside ambient air conditions. Just remember that the maximum needed unrestricted radiator area depends on both the _load_ (e.g. hill climbing) and speed. There is an interrelationship between the blockage size, load, and outside air temp. In -20F, -30C conditions and with a light throttle a near 100% block would likely be optimum, but have a _very_ narrow tolerance for change in temperature and engine load (e.g. speed).
Should you go for a weekend drive in the mountians or be late for work and decide to run with the big dogs in the fast lane, the size that has worked perfectly in the past may now cause a severe overheat and damage :!: And don't forget $$$$
The above is why monitoring the engine temperature with something more accurate than the stock engine temperature gauge is necessary. IMO once you establish the safe operatinge range, continuous independent monitoring is
better, but redundant. Perhaps the easiest way to get this data is from a scan tool via the ECT (Engine Coolant Tempertaure sensor). There are many tools to choose from and it will also serve as a code reader for any future check engine light problems you might have. If you already have a Palm or Pocket PC then there are cables & software available for only a couple hundred dollars (google or the forum search feature is your friend). But a nice temperature gauge can probably be had for about 2/3 of that.
For your _maximum_ load (and speed) condition the cardboard block should not allow coolant temperature above 205F, 96C (the fans on point).
2) Running the Air Conditioner (AC, remember "Auto"
is AC on) in warm weather with the block is just as bad. The restriction will also reduce airflow over the condenser (the outside AC coil). This _will_ cause higher AC pressure loads and could rapidly cause AC compressor failure :!: IMO and from my calculations (there are charts for AC pressure based on temperature and humidity) with a 50% blockage (6x17"
) and "using" the AC in winter (60F, 16C and lower) as the "defogger" will be in the "safe range" and no additional compressor "wear" will result.
3) Positioning the cardboard so that the blockage is primairly horizontal is also a design consideration. The radiator cross flow tubes on the Insight are vertical. A horizontal piece of cardboard is effectively "cooling" the tubes in their normal direction of flow. Blocking a percentage of the radiator vertically will cause the entire length of a tube to be chilled, rather than the "normal" temperature drop from top to bottom across all tubes (which happens with or without the _horizontal_ cardboard). In theory _vertical_ cardboard can contribute to mineralization (internal flow blockage) in these cold tubes over the _long term_ and can ultimately require premature radiator replacement.
[end edit / addendum]
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