So what are you supposed to do?

So I found this while looking for CHT gauges. Are you supposed to rely on hopes and wishes?? Obtain engine ESP?

GeneBerg.com said: WHY WE DON'T SELL GAUGES: I hear daily of engines being destroyed by people relying on gauges. I have run hundreds of accuracy tests on practically every inexpensive aftermarket gauge under $125 offered. Practically all read low in the 212 to 260 degree range by 40 to 50 degrees on oil temperature and head temperature gauges in the 250 to 550 degree reading range, again being low by as much as 250 or more degrees. I tested about twenty each of most brands such as VDO, Smith, Stewart Warner, Hawk, etc., and found none without these problems. Oil temperature gauge readings would be 212 to 220 degrees on the gauge when the true test temperature was 240 to 260 degrees. Head temperature gauges read 385 degrees with a true test temperature of 550 plus degrees. When head test temperatures were upped to 700 degrees, the reading of the gauge went up to 390 to 395 degrees. The price range of such gauges was from $60 to $125. I swapped gauges with senders and got different readings. I found nothing in that price range I would wish on my worst enemy. Not one I tested could ever be properly calibrated or relied on in any way for any valid information or even as a comparison from day to day on the air cooled VW. Yes, even the oil pressure gauges were just as bad. I found good accurate gauges range from about $250 to $350 and few people would buy them. What was needed was a device that gave the information required and was reasonably priced. That was the reason for the GB 227 in the first place. It is specifically made and calibrated to provide an accurate reading in the ranges of the VW air cooled engine. Originated by Hal Brown in 1972. Made in the USA. Note: If you must install an oil pressure gauge use GB 264-1/8 tee fitting and GB 265-1/8 pipe nipple to install the factory (Bosch VWA021-919-081B) light sending unit and the gauge together as the factory sender and light are over 100 times as fast to tell you if you run out of oil. Never use any sender that has the pressure and a light combination as they are extremely slow and you lose the rapid action that the factory light sender provides. Warning: If you want gauges as a decoration fine, but never rely on them. After all, if they provided reliable information I would be selling them to make a profit just like our competition.

I just have a hard time believing that so many brands of aftermarket gauges are all inaccurate across so many different types of gauges.

I just have a hard time believing that so many brands of aftermarket gauges are all inaccurate across so many different types of gauges.

I don't. But so what? As long as you learn to interpret what your gauge means as installed on your application, its is all good. Any instrument that you are going to rely on requires periodic calibration verification.

I also find it hard to believe that such massive inaccuracy is so widespread, maybe a problem with his test setup?

What I like to do is check gauge readings against external readings and adjust my expectations to suit. For example on my Samurai, full operating temperature (~180F) is sitting near the bottom of the scale on the gauge. If the gauge ever goes into the half-way position where full operating temperature is supposed to be, the engine has already gone gooey.

NOHOME wrote:

I just have a hard time believing that so many brands of aftermarket gauges are all inaccurate across so many different types of gauges.

I don't. But so what? As long as you learn to interpret what your gauge means as installed on your application, its is all good. Any instrument that you are going to rely on requires periodic calibration verification.

Well that's not what I'm pointing out. He says he tested 20 companies of one each of type of gauge and got bad results across the board.

Now I have a hard time believing that every single gauge was as innacurate as he says. I think Gameboy is right, his test set up was flawed in some way.

His last comment kills me about "If you need gauges as a decoration"

Well I did put three temp guages on my race car before I got one to agree with a thermometer. And my wanderlodge reads 20 degrees low.

Also air pressure guages. I tested five of them, all good quality guages and threw out three because they didn't agree with the other two. I don't know it the remaining two are right. Could have been an inaccurate coincidence.

If he is getting a similar deviation on all the gadges tested he has probably only proved that his test rig is faulty. I have done some basic testing on Porsche gadges (vdo) and Porsche sending units and found all of them to be quite good.

(rant...)

Gene Berg....

Gene Berg was a real pioneer back in the day. He was also a grouchy, opinionated old fellow. I have spent quite a bit of money on his parts over the years, but I don't drink all of the Kool-Aid that he preached. He was known in the Volkswagen scene as being a bit of a dinosaur who wouldn't listen to reason or any opinion that differed from his own. After a couple of decades of the hobby I moved away from the ACVW scene. My last bug, I spent a pretty good pile of money building a big stroker engine with all the trimmings. Cost was no object. In the end, my wife's moderately modified 5.0L Mustang coupe would absolutely walk away from it in a straightline race. It just didn't seem worth it anymore with the cost and difficulty in sourcing decent ACVW engine components when other vehicles offered similar or greater performance for much less effort and financial outlay.

(end rant...)

In reply to Cousin_Eddie:

At some point you have to like the driving experience and not the comparative performance. It is why I like my 924s.

I'd like to know where he's testing the temps on the engine itself. Certain engines have localized hot spots.

In reply to Cousin_Eddie:

That's quite interesting and answers why the commentary is so brash.

If you want dead-accurate sensors, get an AIM MyChron for karting. Their temperature sensors read 32 F dunked in ice water and 212 F dunked in boiling water.

That's the thing about temp, it's only viable to compare a gauge if you're measuring the same spot under the same conditions. Particularly oil temperature gauges. Temp in the sump is a hell of a lot different than temp in the galleries, which is again different from temp at a sender, and is that before or after the oil cooler? There are HUGE differences in oil temperatures depending on where you're reading it.

With air cooled VW's and head temps you don't have cooling jackets that can transfer heat around. You're going to again have wildly different readings between the head, the tops of the fins, the bases of the fins, etc.... Then throw in how the add-on gauges are usually installed, with that ring around the spark plug. You're going to have air flow hitting the sender, which is going to directly cool it. Huge variable there that of course is going to cause a gauge to read lower than actual.

It's not that you can't trust gauges, it's that you have to understand what they're telling you, how they're getting their info, and also what that reading actually means.

Now that is interesting, I have used inexpensive gauges on my older bronco (sunpro?) and it seemed to be fairly accurate with the limited testing I did. Now can the same be said about other types of gauges? like boost, vacuum, EGT, and so on?

In reply to tjbell:

I've tested three different boost gauges on my car and on the bench (T'ed all three together.) Two matched and the third was less than .5 psi low when tested at 20 psi.

If all of your gauges are 20-40 off, they're more than likely all accurate +/-10. Though from what I've read of air cooled VW stuff if your cooling system is unmolested (all the tins and flaps are there) and the ignition timing correct you're going to really struggle to overheat it in a car to begin with unless it's a pretty far from stock motor, at which point an oil temp gauge is probably a good idea.