For the past 7 years I've been using 2 Cadillac compressors with great success for my on board air, however since they're bolted to my 2nd gen 4runner, they're not exactly portable. With the acquisition of a 4th gen 4runner I needed another way to fill tires, float tubes, and air mattresses. As luck would have it, a
thread popped up here showing a link to a dual cylinder compressor with a great low price of $60. After doing some research it appears this compressor is the same as the Q-89 compressor which usually sells for at least twice the price and has the added bonus of not being hideously chromed out.
It comes with everything you see here:
It's not too big with an overall size of 9"L x 5.5"W x 7.5"H (with handled folded down):
The top has a handy dandy compartment to store the little accesories that comes with it:
Here's the gauge which actually seemed to read a little low with the compressor off and a little more accurate with it on.
Here's the label on the front:
Now on to the good stuff. I tested the compressor with a 33x10.5 R15 BFG Mud Terrain and a P265/65R17 Bridgestone Dueler which is the stock tire on the 4th gen.
You'll notice in the above picture I have a thermocouple at the top of one of the cylinders to measure temperature, however, I discovered this location was fairly cool compared to other places. In subsequent test runs the TC was moved to the bottom of the cylinder shown in a picture below.
Pressure testing was done from absolute flat (0 PSI) to approximately 33-35 PSI for both tire sizes. At 1 minute time intervals I would shut off the compressor and the timer, remove the connector from the valve stem and measure pressure with my more accurate pressure gauge. The gauges I use are accurate to +-2% of full range. Once pressure readings were taken, I would reconnect the compressor and resume the test. A little bit of air would leak out when disconnecting and connecting the compressor, but the amount was insignificant compared to the volume of the tires.
Pressure test results:
The results were surprisingly linear in this range but I guess this is to be expected with a compressor that can go up to 150 PSI. Since I took pressure readings throughout the test, one can calculate the amount of time it takes to fill the tires from any point along the curve to any other point along the curve.
33x10.5 R15 BFG
0 PSI to 35 PSI = 6 min
10 PSI to 35 PSI = 4 min 20 sec
10 PSI to 32 PSI = 3 min 42 sec
P265/65R17 Bridgestone
0 PSI to 35 PSI = 4 min 9 sec
10 PSI to 35 PSI = 2 min 57 sec
10 PSI to 32 PSI = 2 min 48 sec
Another test I did was the temperature of the compressor. The temperature readings for the graph were taken just below the red portion of the finned cylinder in the black area.
Interestingly this was not the hottest part of the compressor. The metal fitting at the manifold was the hottest, followed by the quick disconnect connector.
This picture shows the temperature locations:
For the 4 minute, bridgestone run, these locations got up to:
Connector = 138 deg F
Hose = 116 deg F
Manifold = 170 deg F
During 2 consecutive runs of the BFG, the connector got up to 154 deg F. The lesson here is to be careful of the hose and connector during filling.
Overall, I think this compressor is a good one and seems well made. I can't fault any of the construction quality except maybe the plastic base but that makes it lighter and it should last. The switch and fuse are a bit large and clunky but user friendly. The motor sounded strong and healthy even when starting up at 30ish PSI and didn't bog down at all. Looking at the box and manual I couldn't find any mention of a manufacturer or even the name of the compressor. There is a picture of a Prado on the box however, so that indicates it's from overseas somewhere, needless to say.
I happened to find a coupon code over at www.toyota120.com while www.overlandwarehouse.com was doing an October promotion. This brought the price down to $50 plus shipping. They're still working out some bugs with the store website and they accidentally charged me sales tax but they should clear this up shortly. Shipping was fast and email response was also fast.
The following was added 10-25-09:
Ok I repeated the tests with the engine running and here are the results. Note that the lines shown are the trendlines only, not the connected dots lines. This was done for simplicity of viewing the graph.
This graph is much more cluttered because it shows the following test conditions:
-Engine off, 33x10.5
-10 to 35 PSI = 4 min 20 sec
-Engine off, P265/65
-10 to 35 PSI = 2 min 57 sec
-3.0 Engine running, 33x10.5
-10 to 35 PSI = 3 min 33 sec
-3.0 Engine running, P265/65
-10 to 35 PSI = 2 min 54 sec
-4.0 Engine running, P265/65
-10 to 35 PSI = 2 min 43 sec
As you can see, with the engine running the fill times did reduce but it depended greatly on the tire size and which engine powered the compressor.
I was skeptical of the data for the "Engine running, 33x10.5" because it was so much faster than with the engine off, so I repeated the engine running test 3 times. Each test was nearly identical so the data must be valid. The only explanation I can think of is there are diminishing returns on smaller tires.
Here's some new temperature readings done after 3 consecutive tire fills:
Connector = 176 deg F
Hose = 125 deg F
Cylinder = 161 deg F
Manifold = 179 deg F
Keywords: MV50, MV-50, Q89, Q-89, Q Industries MF1089 MasterFlow Twin Air Compressor, superflow.
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Originally Posted by Robinhood4x4
