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Old 12-05-2008, 03:06 PM   #1 (permalink)
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10-minute Accord vacuum gauge "install"

I had 10 spare minutes last night and access to a warm warehouse, so I drove my Accord up the ramp and inside to do a quick jury-rigged install of my vacuum gauge. I used the Auto Gage 2 1/16" gauge. I prefer the full-sweep motion, and I never plan to turbocharge the car, so a boost side is wasted on me. I also like this gauge because it's 100% mechanical, so I didn't need to do any wiring to start using it right away. The red/yellow/green zones also give me an easy indication of how I'm doing, allowing my eyes to spend more time looking at the road ahead.

Tools needed: zip ties and a "grommet pen":



This is one of those chintzy "executive desk" pens, which I found laying around, already starting to rust. The vacuum line included in the kit slips snugly onto the pointy end (left), and the writing end (right) was used to poke through one of the main wiring boots:



Sorry about the poor picture quality. I don't have a "real" camera, so this is done with a cell phone camera. Here you can see one of the main wiring harnesses, right above the new master cylinder, and the Warm Air Retention System.. er, buildup of leaves. The pen slid through the boot easily, and the vacuum line stayed on the stabby end. Once the pen was through, I could pull the rest of the line through.

Next step was to cut into a vacuum line and install the included 'T':



I chose the line that came directly off the throttle body. One thing I can say about the PGM-FI engines--there's a lot of easily accessible vacuum to go around.

Finally, the interior side:



There was just enough line included to reach from the throttle body (middle-right of the engine compartment) through the boot (above the master cylinder) and up to the steering wheel. I zip-tied the gauge to the cover through its mounting holes. Since I plan on putting in a gauge pod (along with a 'real' temperature gauge), I didn't want to drill any holes.

This picture shows my warm idle--about 21.5 in. 62 mph on the flat runs about 15 in., which makes things easy: if the needle is to the left of pointing straight up, I'm using more throttle than 62 mph flat, and to the right means I'm using less.

I'm amazed at how quickly the gauge moves. I didn't realize just how little foot movement it takes to go from the middle of the green zone into the yellow zone. I can also easily tell when there's a headwind, as maintaining 55 mph through a flat windy area brought the gauge down to about 10 in.

Some other notes:

1. My cold-start idle (38 degrees) was at about 15 inches instead of the normal 21 inches. This coincided with the higher idle, and didn't completely go back to 21 inches for many miles. Maybe a block heater is in order for the winter months.

2. The A/C brings the vacuum down about 2 inches at idle, or about 1 inch while cruising. Seems like a significant difference.

3. If I'm coasting downhill, turning off the engine increases the vacuum somewhat (from 22 to 26 inches, for instance.) I think this means that I don't have DFCO on this car (it's a '90), so a kill switch might make a big difference.

4. I'm trying to work out the best way to climb the hill home. It's about 15 miles, with a 4,000 foot gain. I do about 42 mph for most of it, and the gauge reads 3 in. in 4th gear, and about 10 in. in third gear. Anybody with more experience who can tell me which is better for FE? This is the biggest killer of mileage in all my cars.

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Old 12-05-2008, 06:26 PM   #2 (permalink)
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Higher gear lower vacuum and lower rpm seems to work better for me. This should be best as long as you're not lugging the engine.
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Old 12-05-2008, 06:43 PM   #3 (permalink)
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Quote:
Originally Posted by Ford Man View Post
Higher gear lower vacuum and lower rpm seems to work better for me. This should be best as long as you're not lugging the engine.
Cool. I can do fifth for part of the trip, but then there's a lot of upshifting and downshifting. Fourth seems to be the sweet spot as far as RPM vs. power, but I didn't know if third would be better in that regard.
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Old 12-22-2008, 02:59 PM   #4 (permalink)
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I have some hills in my commute, too.

All things being equal (like mph) I think I get a little better FE in the tallest gear (5th gear in my case) and near wide open throttle (WOT) rather than drop down into 4th gear at half throttle. I just got my tee and more vacuum line this weekend, the hooking up is cake, but I need <want> to make a clean looking mount for the dash.
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Old 01-10-2009, 09:18 PM   #5 (permalink)
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what about dropping it to 14 where it is now 15, and just acknowledge the rest. I would assume backing off the thottle as more air gets in to drop it to 14 would require a bigger air inlet. That reading is very high, the 21.
I have a 1781cc carbed that does not go that high, injection has delyed cams for the computer to compute. I almost want to install a guage for the heck of it.
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Old 08-24-2010, 12:09 AM   #6 (permalink)
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anyone know of a cheap gauge from harbor freight?
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Old 08-24-2010, 06:34 AM   #7 (permalink)
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3 inches in 4th gear is close to best BFSC. That's also a good reading for your pulse, but 2 would be slightly better.

DFCO can be easily detected, just let her slow down in 3rd gear (clutch out if manual, foot off the gas) and watch the gauge. If you feel a surge at around 1000 RPM and the car stops slowing down as quickly then you have just experienced the effects of DFCO, which ended when you felt the surge. Your vacuum will drop significantly when you feel the surge, which is fuel delivery.

You will find that 2 inches for acceleration is an excellent way to maximise your mileage, and yes, that reading can be achieved sometimes without a lot of throttle application.

regards
Mech
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Old 09-10-2010, 03:53 AM   #8 (permalink)
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I forgot all about vac gauges, where did you get yours?

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