What is the difference between a electrical and a mechanical gauge? Also which gauges are needed besides the Boost and Water Temp gauges?

 

Electricar= required a sensor to operate other than the factory.

mechanical=need to run an actual line (ie. fuel, oil, etc) to the cockpit to work.

to me mechanical gauges are more acurate. Does are the basic gauges to use in the FD but I also use Fuel and Oil pressure to identify problems and monitor the car. and anothe is EGT just to check if your are running rich or lean.

 

Other gauges really depend on what you are going to be doing with your car. A/F gauges are useless unless you use a wideband O2. EGTs are pretty much pointless, but can be "slightly" useful. Fuel Pressure gauges can really come in handy if you start modifying the car heavily. Oil Temp gauges can be helpful if you do a lot of open track racing.

IMO, as long as you have a boost and aftermarket water temp gauge, you are pretty much set for a while.

 

Mahjik, you're a wealth of information and searching isn't helping me too much. Do you have a site or link for a water temp guage install?

 

No problem. Check this thread:

https://www.rx7club.com/forum/showth...hreadid=187766

Someone was asking about the water temp install a few days ago and the thread has a lot of good information. Apparently, the Autometer Water Temp gauge can be installed without any tapping. The only downside is that you probably won't get any readings until the themostat opens up but most people don't care about the temps until after that happens anyways.

 

Care to explain how a mechanical gauge is more accurate than an electronic gauge?

 

I pefer to use electrical gauges for anything that could come off, and pour something into my car. Example: Oil pressure, oil temp, or water temp. My boost gauge is mechanical. If that line breaks, it's just air coming in.

 

Well this is just my opinion (not to make a big thing on this I hope everyone respect my opinion), because the gague is reading directly from the source, not from a sensor that has to past current to the gauge. When current travel the current get weaker as it travel, speacialy if the cable is not straight. We know this as resistance. Yes the resistance will not change much but I think if some thing fails the mechanical gauge will let you know quicker or will alert you. The only thing I don't like the mechanical one is for the fact if one of the line brakes. Just what I think.

 

1) the gauges are designed for any signal losses through the sensor wire (very doubtful that is even measurable). Also mechanical gauges are not reading directly from the source either, as they have several feet of tubing from where ever they are reading from. Mechanical tubing can get pinched off and blocked where as electrical wire can be more durable and reliable for this purpose.

2) current travels a hell of a lot faster than oil or fuel or air, so I don't see how a mechanical gauge is going to warn you faster. Usually, electronic gauges have more features such as warning lights and peak/hold functions.

3) as you brought up, if a line breaks on a mechanical gauge, it can be very messy and/or dangerous.

I guess we'll just agree to disagree on this point.

 

Boost is the only mechanical guage that could probably operate faster than it's electrical counterpoint. It will probably be off a little bit because of the elasticity of the hosing, but it will react the fastest


As to the others...

 

Until the day their thermostat fails and the engine overheats with the temp gauge telling you the whole time everything is alright.

If you are going to install a water temp gauge put it behind the thermostat. This means in the block like the stocker or inline with the throttle body coolant which is behind the thermostat.

IMO anything in the filler neck/thermostat housing or radiator hoses is a poor choice. What's the sense in having a gauge to reassure you everything is alright if it could possibly be lying to you?

 

Like I said this is just my opinion I respect yours and I see your point but mechanical gauge makes me feel more secured. electrical floats your but cool I'm in with that. Thanx for the info

 

Is it just me, or shouldn't the coolant temp at the thermostat housing be pretty darn close to the temp of the engine? I mean maybe a slight delay until the hot coolant gets to the thermostat but are we talking about seconds here? I don't know just wondering. Anyway, just seems to me if your car is overheating then the coolant at the thermo housing should be overheating just as much as the engine, therefore you would pull over and try to find the problem.

 

Yes and No. When the thermostat is shut all the hot coolant is inside the motor and not flowing through the thermostat housing. When the thermostat is open and coolant is flowing then the reading would pretty much be the same as what is in the motor.

Not if the thermostat is stuck shut. If the thermostat is stuck then all the hot water is trapped inside the motor and the temp probe in the thermostat housing would be none the wiser. That's why Mazda puts the stock temp sensor in the block, it's the best place.

 

Cool, thanks for the info. That makes sense, if the thermostat is stuck shut you're screwed and wouldn't see the temp rise. I am going to get a temp gauge very quickly and install it. Where would you install the sensor if you wanted to keep the stock temp gauge? I just got my fd and need to get this mod done asap. Thanks for the info. I would search, but since we are already talking about it I figured I would ask.

 

they dont have a autometer oil pressure gauge that goes over 100 psi

 

well i have my DEFI in the thermo housing. i picked it cause there was more room there then anywhere else i could find, plus it was super convienent. one thing i notice is that i see no more than 100 degress F until the thermostat opens. after that it jumps fast to operating temps. what i would like to add to go against DAMONB(my opinion and i would like to hear yours on mine) is this...if i were driving more than 5 minutes and my thermostat hasnt opened(temp rising) then i would know that i have a problem. yes i know if i picked a different location i would know faster since the water is that hot already, but saying the housing is a bad spot would be controversial. please let me hear what you have to say. if its good, i just might pick a new spot and put a stop to the temp in the housing.
kris

 

please find something better than autometer. nothing against their products for a honda or something that isnt as expensive as our cars. just dont know why people get CHEAP stuff. im normally a get what you pay for type of guy but the quality just doesnt seem there to me when it comes to autometer. im sure its good stuff, but there is a lot better
kris

 

Ok well so far my two gauges which are Boost and Water Temp gauge are both Autometer but I guess those are ok to keep? As for the other gauges I should get which company would you recommand then? I"m also obviously going to go for the electrical gauges rather then the mechanical ones :p

 

well i should rephrase what i wrote. if it gets the job done so be it. i like how my defi get the job done and look great. im not really an autometer guy. autometer just happens to be the only other company aside from defi that makes their gauges in (what is the term i am looking for...miles not KM, F not C, pounds of boost not BAR). its mostly a preference thing. i just prefer to look nice. its the nicest car ive owned, and i would like to keep anything out that wouldnt kill the looks entirely.
kris

 

Autometer gauges are fine. It's purely a preference thing like whether you prefer to wear Levis or Tommy Hilfiger jeans. They both do the same function it just depends on if you want to spend more for the name or not.

 

What I don't like about using the thermostat housing (or anything in front of the thermostat) is just like you said, I would have to look at the gauge and then ask myself how long the car had been running while wondering if everything is in fact alright. The reason I feel the thermostat housing is a bad choice is because there are better ones, that automaticlly makes the housing bad using my logic. The gauge would depend on the fact that the thermostat is functioning correctly in order for it to do its job. So I would have a gauge in front of me I still have to question; I just want to look at the gauge and KNOW. I don't like the idea of giving the gauge an opportunity to lie or me having to interpret its reading.

In addition right now the only failure mode I have would be for the sending unit or its wiring to go bad. If the probe were in the thermostat housing I would have another possible failure mode, the thermostat itself. IMO opinion always eliminate all the failure possiblities you can, especially if it's something you already decided was important.

I don't want to have to involve my brain in making decisions I can avoid. That's the same reason I think the classic fan mod is goofy. Sure it works, but I have to remember to flip this switch this way and that at certain times along with having an extra switch in the interior I don't need. If you just put the Miata thermoswitch in that kicks the fans on sooner all by itself I don't have to sit there and ask myself "Is it time to flip the switch on yet? Has it been on long enough and now it's time to switch it off?" It does its job without any input from me. That's the same thing I want the temp gauge to do.

 

Does anyone have a alternative place to mount the a new temp gauge instead of the thermo housing if you want to keep the stock temp gauge too. I thought I heard of someone installing their new temp gauge sensor in the stock location and relocating the stock sensor to the thermo housing. That way you can keep the functionality of the stock temp gauge while having the new gauge giving you the correct engine temp before the thermostat opens. If anyone has the info on what adapters to use to do this let me know. Thanks.

 

You can mount the sensor inline with the throttle body coolant by splicing a "T" into the rubber hoses and screwing in the gauge probe. The throttle body coolant comes from the engine block and should read the same at all times as the stock sender in the block.

 

In this case I don't see the logic. Water and Oil temp gauges serve one purpose - to let you know how hot the engine is running and when it's time to shut down and cool off (hopefully never). As long as the gauge gives consistent readings, you're fine. It's not like anybody can actually do anything different with a gauge that reads better than ±5°.

Also I think in this case I would base the mechanical vs. electrical type on failure. Whichever one makes the most obvious symptoms when it fails (like readings of 0), and the one that is least likely to get out of calibration. The truly scary thought is a gauge that gets inaccurate without any warning signs. I haven't heard of it happening though; maybe some gauge tech experts could elaborate on that thought.