|
SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Vacumn Gage or Tach ? /cgi-bin/YaBB.pl?num=1268836143 Message started by Routy on 03/17/10 at 07:29:03 |
|
Title: Vacumn Gage or Tach ? Post by Routy on 03/17/10 at 07:29:03 My complaint,.....not being able to tell which gear I'm in at higher speeds. I was going to Tach-o-meter it, but coming from the petcock thread,..I'm now wondering if a vacumn gage wouldn't give the same info,...and maybe much more valuable info. To me its a matter of knowing how hard the engine is working as to what gear I want to be in while cruising. Judgeing from the value of a vacumn gage on my motor home when driving in the mountains, I really think this mite be the way to go. If I start seeing less than 5 inches of vacumn, its time to grab another gear....period ! If I see 12-15 on the gage, there is no reason not to take her up a gear. Ever wonder why most pipes turn blue ? Jetting, maybe, but do ya think driving to a vacumn gage would lessen the "blue pipe syndrome" ? Any comments....ok. |
|
Title: Re: Vacumn Gage or Tach ? Post by skatnbnc on 03/17/10 at 12:18:41 I agree with the issue, because I cannot hear when to change gears once I am on the highway. Vac guage sounds interesting. |
|
Title: Re: Vacumn Gage or Tach ? Post by Boule’tard on 03/17/10 at 12:55:34 Some guy on here rigged up his neutral light to come on when the bike is in 5th gear. I usually just go by sound.. if it's a loud enough BrraaAAAP! :D time to shift. |
|
Title: Re: Vacumn Gage or Tach ? Post by Oldnewguy on 03/17/10 at 12:57:13 Not much difference between 4th and 5th, about 300 rpm, but the idea sounds interesting. I had a vacuum gauge on my car back in the 50's. It was also supposed to help you drive so that you got better gas mileage. Post it up if you find out more. :) |
|
Title: Re: Vacumn Gage or Tach ? Post by Moofed on 03/17/10 at 13:42:55 Seems pretty helpful for diagnostics: http://www.secondchancegarage.com/public/186.cfm Lots of other good info on that site too. My question is would our thumper engine make the needle jump around alot? I mean, a 4+ cylinder engine has a cylinder doing the intake stroke at any given time, right? We do not. I guess another way to ask is, does the petcock diaphragm hold open steadily or does it oscillate open and shut? |
|
Title: Re: Vacumn Gage or Tach ? Post by Charon on 03/17/10 at 15:30:49 I have used vacuum gauges on several cars over the years. Last was on a pickup with a 318 V-8. The vacuum gauge needle will jump around even on a V-8, unless you put a "restrictor" in the tube between the manifold and the gauge. The restrictor can be an old carb jet, if you can find a suitable one. I used a small clamp to pinch the tube, and adjusted it until it seemed to work. A large hole makes the gauge jumpy; a hole too small makes it respond too slowly to be useful. Another option might be several feet of small-bore tube, perhaps coiled under the gas tank. The vacuum gauge works nicely for adjusting the idle mixture - adjust for maximum vacuum (minimum manifold pressure). As far as using it to save gas, I'm not so sure. Keeping vacuum high very simply means not opening the throttle as far - which reduces power. If you drive at highway speed in third gear, the engine will spin quite fast but the throttle will not be far open and the vacuum will be high. Trouble is, maximum engine efficiency happens with a wide-open throttle where intake pumping losses are least. That's why overdrives work - they hold engine speed lower and require larger throttle openings. |
|
Title: Re: Vacumn Gage or Tach ? Post by Oldnewguy on 03/17/10 at 15:44:10 If I remember right the gauge was used to tell you if you had your foot in it a little too much. The needle would red line. If you accelerated slower it would stay in the green. I am going back 50 years, so I may be "all wet" ::) |
|
Title: Re: Vacumn Gage or Tach ? Post by Serowbot on 03/17/10 at 16:17:31 08232A3924254B0 wrote:
not sure about that last part.... :-/ I used to use vacuum gauges in all my cars,... very useful for getting the best gas mileage,,... not so good for a gear indicator... It would require identical conditions every time to give a repeatable reading. That includes, headwinds, air density, etc.,... I try for sixth gear all the time,.... it keeps me humble... :-? My Geo Metro has a "time to shift" indicator" light... don't know what makes that thing work... I guess it might be vacuum, but it's only good for achieving maximum gas mileage... that's why I haven't installed a vac gauge in this car... |
|
Title: Re: Vacumn Gage or Tach ? Post by Routy on 03/17/10 at 16:26:06 Quote: My question is would our thumper engine make the needle jump around alot? --------------------------------------- Thats a good question,....I sure never thought about that. But its too late now,...as I thought it was such a great idea, I ran down to Napa, and of course they had every gage imaginable except a simple vacuum gage. But they'll have one at 7am. And I already fabed the mount from 12ga ss and have it mounted on the bike. I even had a "T" to fit in the vacuum line,.....unless the gage line isn't the same size, then I'll need a reducer "T". If it works like I hope it will, it saves me buyin a tach, I'll be tickled. I only want to know how hard the motor is working at speed, and that is what a vacuum gage does best. If it is too irratic to be usable, then I blew 30 bucks. I'll keep posted here,..... maybe even a pic if I'm impressed w/ it ;D |
|
Title: Re: Vacumn Gage or Tach ? Post by Serowbot on 03/17/10 at 16:27:41 Quote:
I'm guessing a super big yup at low RPM's, steadily decreasing as you increase speed... a reducer jet, like what Charon was talking about would help with that... Charon Quote:
Useful info, even if it don't work as a shift indicator... Good luck... ;) |
|
Title: Re: Vacumn Gage or Tach ? Post by bill67 on 03/17/10 at 17:13:22 My first car 1949 Chevy had one.You had to have your windshield wipers going to use it,.JOKE if your windshield wipers were going and you step on the gas to much they who stop were ever they were. They were vacuum powered from you engine.Some old timers here will remember that. |
|
Title: Re: Vacumn Gage or Tach ? Post by Routy on 03/17/10 at 20:10:38 Hey Bill, I'm not near as old as you, but my first car....55 Ford was superiour to your Chev, in that it had a "double action" fuel/Vacuum pump to keep the wipers going when the pedal was to the medal ! But then, I know you knew that ;D |
|
Title: Re: Vacumn Gage or Tach ? Post by Charon on 03/17/10 at 20:29:08 My '52 Chevy had vacuum wipers, too. Later on I had a '66 Ford Bronco with vacuum wipers, one on each side. It also had the double diaphragm fuel pump. When you stepped on the throttle the engine vacuum went away, and the wipers would move one "pulse" at a time as the fuel pump diaphragm pulled vacuum. But when you went down a hill, the vacuum wipers really worked well. I used to tell people it had enough power to move the vehicle, or run the wipers, but not both at the same time. My pickup with the 318 also had an after-market cruise control. Like many cruise controls it used vacuum to open the throttle servo. I found that it needed three inches of vacuum. If I went up a mountain grade, I could watch the cruise "work." It would open the throttle and the vacuum would drop. When the vacuum got down to three inches, the cruise couldn't pull the throttle any harder, and the truck would start to lose speed. I could step on the throttle and maintain speed, depending on how steep the hill was, but the cruise only worked down to three inches. |
|
Title: Re: Vacumn Gage or Tach ? Post by Routy on 03/17/10 at 20:30:23 567D74677A7B150 wrote:
I have used more than a couple Vacuum gauges in past years, and they were all restricted w/ just a little bitty hole in them, and none have ever pulsated on a v-8. I'm only hoping it won't be much more on this thumper. I'm not sure you fully understand how an overdrive can...but doesn't always give better mileage. A WOT w/ low manifold Vacuum doesn't give better mileage. Lower rpm's while still holding a reasonable manifold vacuum does. |
|
Title: Re: Vacumn Gage or Tach ? Post by jabman on 03/18/10 at 05:14:13 i just fitted one to my vac hose it flicks from nothing to full so fast the needle is a blur more work is needed here it looks |
|
Title: Re: Vacumn Gage or Tach ? Post by Routy on 03/18/10 at 06:19:18 If its a tune up gauge like I have, it doesn't have restriction in it. I'll find out about the "SunPro" in a few hrs. I'm sure w/ restriction it will stabilize at higher Rs. 42494A454946280 wrote:
|
|
Title: Re: Vacumn Gage or Tach ? Post by Routy on 03/18/10 at 20:12:59 Got it done. Sure looks nice, but I don't think it will make a good shift indicator. I didn't get a chance to really try it out at speed. More later. http://p1.bikepics.com/pics/2010/03/18/bikepics-1929943-full.jpg |
|
Title: Re: Vacumn Gage or Tach ? Post by Routy on 03/19/10 at 05:23:00 Shown....10" Vacuum at dead idle. At 1500 R's it dropped to 7-8" That seems low, but I've never put a vac gauge on a single cyl either. The reading was quite irratic at idle,.....0-15 and stabilized some at 1500 R's, ...like 8-12. The restrictor in the gauge was .030, so I added a .020 in the hose, and now it is perfectly normal w/ reaction time still ok. I'll try it at speed when the weather warms a little. But if it fails to serve the purpose, I have another place for the gauge, and my custom made ss mount will hold a tach just fine. http://p1.bikepics.com/pics/2010/03/18/bikepics-1929944-800.jpg |
|
Title: Re: Vacumn Gage or Tach ? Post by jabman on 03/19/10 at 05:35:39 hey my vac gauge goes from 0-30 like that one what did yer do to make it work? does it need blocking of with a 0.5mm hole in the middle? |
|
Title: Re: Vacumn Gage or Tach ? Post by Charon on 03/19/10 at 06:01:31 I am going to make a guess, here. I am guessing your vacuum gauge is "averaging" or "integrating" the vacuum in the manifold. During the intake stroke, about 180 degrees, there is a pressure reduction or vacuum in the manifold. During the other strokes, about 540 degrees, the pressure is near atmospheric. So vacuum is present only about 25% of the time. The restrictor in the vacuum hose (or in the gauge) "damps" the gauge response so the needle responds more slowly, and you see the average vacuum instead of the instantaneous vacuum. I expect this phenomenon would exist in the manifold of almost any multi-cylinder engine with individual carburetors and manifolds, and no balance plumbing. I have to wonder whether this very pulsatile flow and vacuum makes setting carburetors more difficult. I wonder whether the throttle slide on CV carburetors is constantly jittering in response to it. |
|
Title: Re: Vacumn Gage or Tach ? Post by Routy on 03/19/10 at 16:01:51 Your guess about average may be correct. Like said I have never done this on a single cyl. But I'm convinced there is nothing wrong w/ the bike,.....as to the low vacuum. I still hqave to road test it yet. 062D24372A2B450 wrote:
|
|
Title: Re: Vacumn Gage or Tach ? Post by Routy on 03/19/10 at 16:11:43 I machined a round pc of plastic 3/8 " long to the same diameter as the "T". Then I drilled it w/ a number drill at .020 then I used the T to push it into the hose. And It is 100% stable at all speeds. 2823202F232C420 wrote:
|
|
Title: Re: Vacumn Gage or Tach ? Post by miker on 03/20/10 at 07:10:29 If you need a restrictor, find a friend in the commercial Air Conditioning business. A restrictor costs about $0.30, and is available in many sizes, and you can get restrictor tee fittings as well. |
|
Title: Re: Vacumn Gage or Tach ? Post by T Mack 1 - FSO on 03/20/10 at 07:21:31 A nice ananlog (dial) tach from Drag Specialties, Around $80 with the mounts. Then you have something to check the idle RPM to keep it above 1000 rpms. Heck, after a while I started to use the tach as a Speedo since it was higher and easier to look at. |
|
SuzukiSavage.com » Powered by YaBB 2.2! YaBB © 2000-2007. All Rights Reserved. |