does anyone know how to convert? it sits at 418

 

Typically vacuum is measured in inches of Mercury (Hg) so since there are 25.4mm in an inch, your 418mmHg would be equivalent to 16.5 inches of vacuum...

 

well thank you very much. i guess thats not too bad i may still have another leak i guess. i use to only get around 370-380 fixed some small leaks i didnt knwo were there and now it's around 418 or so. i guess it's getting better

 

You should download the program Convert.exe and install it on your computer. Do a search for it. It is great and available at no charge.

418 millimeters of mercury (mHhg) = 16.457 inHg

For an unported engine, vacuum at idle with all lights, accessories and fans off should be around 17 inHg, so you are doing ok.

 

thanks

 

Anybody heard of searching google? I thought something like this was part of knowing how to operate a computer. ABCDEFG.......

 

thanks but everything has been figured out and we didnt need your .02

 

Kevin, you really need to see how cool google is. Type "418 mm in inches" in www.google.com , it's quite impressive.


-s-

 

 

... which, by the way, is what I did to get the answer ... :-)

Except I used Yahoo! search.... which, granted, isn't quite as cool as google and doesn't have the built-right-in calculator doohickey.

 

17inHg at what rpm?

 

i'm at 850rpm

 

The FSM lists 720 rpm as the spec for no-load hot idle for manual transmission cars. I'm not sure if it is the same for automatics. If your engine idles at 820, I don't think the vacuum reading would be much different.

One nice feature of Convert.exe is that once you install it (takes only about 2 seconds) you can use it off-line, unlike Google or Yahoo.

 

So hold up...you guys are telling me that you measure engine health via inHg, NOT in psi? Cuz I always thought it was 16 - 18 psi vacuum = healthy motor?? Cuz I was all paranoid that my engine was super tired and about to go because it's only making/holding 9psi vacuum @ idle... (again, I thought it should hold 16 - 18 psi vacuum). But if it's inHg, then my 89K engine is freakin SOLID, cuz 9psi = 18.32 inHg!

Someone plz clarify for me!

Thanks
~Ramy

 

^^

psi is for pressure. vacuum is measured in inHG (inches of mercury). how are you measuring 9 psi of vacuum? it is not possible.

If you see ~ 9 on your boost gauge, that is inHG...not psi. the boost reading is in psi and the vacuum reading is in inHG.

 

Why wouldn't you be able to read vacuum in psi? Both psi and inHg are measurements of pressure (or lack there of) correct? You can convert measurements between the two.

Ramy, all past posts on the subject of a health vacuum that I've reviewed reference inHg as the proper measurement for vacuum (15-16 healthy, 17-18 great). Can someone confirm this?

 

That was my point. They're both measurements of pressure, and are indeed interchangeable/convertable from one to the other.

I didn't know/notice that. I always assumed or skimmed thinking it said psi...

 

So are we measuring the volume of a glass of water as solid mass now as well?

 

 

It was a joke Ramey. Kinda like on a musical scale you have an E-flat (Eb) and technically it could be called a D# (D-sharp) but you just don't call it D# (Maybe you have musical inclination, I don't know)

BTW thanks for the advice in the PM. He is a good guy to deal with. Just got a little worried at first.

Joe

 

Ramy, what's your boost gauge say on the vacuum side? If it's mmHg or inHg and it's at 9 then, yeah it's tired, real tired...or could be a minute (mI-nute) vacuum leak/hose cracked type thing.

Tim

 

Joe, lol I gotcha. I know what you mean re: the notes etc...didn't realize you were joking initially lol. Don't mind me

Oh and no prob re: the PM. Yea he's solid. Good guy.

Tim, I'm a dork. It says inHg I just never noticed that before. And yea I've long held that my engine is very very very tired. But man she pulls hard as hell. 89K original miles, bought w/ 67K and low compression (the two rotors are close to one another, but one was at the limit at 5.5). So yea it's only a matter of time before she goes byebye. Still impressive as hell for this condition, as I've taken an RC51, Gixer, and even a 503hp Cobra in the past few months!

 

I swear. What is it with Defi gauges. THEY ALL are not accurate. I haven't seen one yet that sits on ZERO!!!

 

My defi boost gauge sits at zero... It reads a little higher than the SPI boost gauge that was on there previously (about 1 PSI) but it reads zero when the engine isn't running...

 

"psi is for pressure. vacuum is measured in inHG (inches of mercury). how are you measuring 9 psi of vacuum? it is not possible. "

TwinTurbo_SE7EN, psi, inHg, mmHg, etc., are all measurements for pressure, just in terms of distance. they're called pressure heads. to convert a pressure head of say, 20inHg, to psi, multiply it by the specific gravity of mercury (13.6) and specific weight of water (0.03611lb/in^3):

20*13.6*0.03611=9.822psi

since pressure and pressure head represent the same thing, therefore, you CAN measure vacuum in terms of pressure head (inHg) AND pressure (psi), just don't forget to place the negative sign in front of your number.

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KevinW, 1in = 25.4mm. therefore, take your 418mmHg and divide it by 25.4 will give you the 16.457inHg that everyone else had told you:

418/25.4=16.457inHg

which also means (as above):

16.457*13.6*0.03611=8.082psi in vacuum