Boost Gauge

Last updated: June 27, 1999


I bought the Autometer 2401 and the A-pillar mount from Mazdatrix (also available from several other sources). The Autometer 2401 looks very close to the stock gauges, with the exception that the chrome ring is a little larger than the ones surrounding the stock gauges. It is black with an orange needle, and is lit from behind with a reddish light. (It also comes a green cover for the lightbulb.) --Steve


Date: Thu, 26 Feb 1998 18:17:26 -0800
From: "Brian L. Goble"

I went with the 52mm HKS guages. The white numbers on a black face with red needles match the stock guages really well (even the look and mounting of the needles are almost perfect). I was told by HKS that the backlighting was amber, but it turned out to be white. I have been thinking about trying to replace the light with an amber bulb, just to make it perfect. Well, I guess I'd have to add a chrome ring to make it 100% perfect.


Date: Sun, 30 Nov 1997 14:23:30 -0800
From: "Jim LaBreck (ECA)"

Greddy Gauge:

Plus: Too cool. Peak hold is a must in a setup that will see high boost and tends to spike or creep. Comes with a small "wrench" to adjust the over-boost setting on the gauge, and the ground output allows you to hook up a buzzer (which I'll probably do) or larger light to get your attention if the small winking red light on the gauge face doesn't. Easy installation, cheap insurance. BIG gauge, easy to read and very accurate.

Minus: Required extensive modification of my gauge cup, since this gauge is a full 60mm. Then again, I got a great fit by taking my time. Price is $286 through Peter, as high as $350 at local shops. Green illumination, no apparent fix. Does not dim with dash lighting, no apparent fix. Instructions in full- blown Japanese, see wiring chart below. Boost measurements are in Bar, memorize a conversion table. (Ed.'s note: I think you can get these in PSI as well. --Steve)


Red wire        -       12V+, ignition switched
Black           -       12V-, ground
Orange          -       12V+, constant
White           -       12V+, illumination
Yellow          -       12V-, output for over-boost warning

Installation was a breeze, cutting the vaccum hose that previously went to my AutoMeter gauge and attaching it to the sending unit that comes with the GReddy gauge. The wiring harness for the gauge itself ran down the gap at the driver's edge of the dash, and then it and the wiring for the sending unit were run along the underside of the dash to the radio area. I tapped 12V+ switched, the illumination circuit (which the AutoMeter was wired to in parallel, allowing it to dim... this gauge doesn't dim and I don't see a simple solution), 12V+ constant, and moved the ground from the illumination circuit to stereo ground. Plugged everything into the control box and it worked... 0.5 Bar max, which equates to my waste gate opening at 7 p.s.i.

Sharp Precision Instruments

Date: Fri, 17 Mar 2000 10:32:51 -0800
From: "James King" (

Sharp Precision Instruments, Part #27100-1AR (I think), should be 2 1/16" 0-20PSI mechanical boost gauge, white lettering on black face, red needle, amber/orange backlighting. Matches stock gauges nearly perfectly. They make the gauges sold by PFS and Stillen, maybe others, but do sell directly. MSRP is around $125.

I think Alamo Motorsports is a discount distributor for them. Cyberspace Auto used to carry their gauges also, but I heard they don't any longer.

Phone: (718) 894-5105

Note: Get an AutoMeter A-pillar mount. DONT get the A-pillar mount that SPI carries, they are inferior in fit & quality. I have an SPI boost and SPI water temp gauge in a dual A-pillar mount from AutoMeter. Looks/works great.


Date: Thu, 26 Feb 1998 16:37:21 +0000
From: "David Lane"

Bret dePedro at Rotary Performance in Manassas, VA sells one by Sharp Precision Instruments which MAY be the same one PFS sells. The price (in the box) is similar at about $120.00.

It is available in several color options. Mine is white on black, with switchable red or green lighting. With the red lighting it is an excellent match for the stock gauges.

This is a very high quality gauge, and makes my old VDO look pretty cheesy.


Date: Wed, 16 Jun 1999 15:42:31 -0700
From: "James S. King" (

Stillen's gauges are made by Sharp Precision Instruments in NY (718) 894-5105. You can get a 0-20PSI gauge that is as close to the stock instruments as I've seen (white lettering on black face, amber backlighting, red pointer), but you have to order one of their "modular gauges". With the modular gauges, you specify exactly what face color, backlighting color and pointer color you want.

The one I described above is part #97100-1AR. (1AR = black face, _A_mber backlight, _R_ed pointer) List price is $125. You can order direct through them or go through one of their discount distributors. The one I've used is Alamo Motorsports in Louisianna (504) 755-6177. Their price was about $110. The downside to ordering like this is that it takes 3-4 weeks to get your gauge. Like Jack-in-the-Box, "they won't make till you order it..."

The gauges made for Stillen read 0 - 25 PSI, which is ok for 300ZXes and Supras, but how many RX-7s need a gauge that reads beyond 20 PSI? A 20 PSI scale gives you better resolution.

SPI does sell an A-pillar mounting pod. It is NOT a good fit. Get the AutoMeter / GaugeWorks one if you want to go with an A-pillar mount.


Westach sells gauges, senders, etc.

Gauge Accuracy

Date: Mon, 18 May 1998 00:08:39 -0400
From: "Houseman, Carl W. x1323"

Here's the results... I've learned one thing in the past week, however. An idle vacuum reading is not cast in concrete. Last week my (corrected for error) Autometer 2401 was reading 14.5", today it's reading 16.5".

Without further ado, the results: Name, miles, reading, etc. "Cal" = calibration confidence, "OK" means the writer said it was good without further justification. Compression readings in PSI or BAR - minimum acceptable is 100 PSI or 7.0 BAR.

Some statistics & comments at the end.

Emory Chang (echang@UCSD.Edu)
16.5, cal OK
Negligible oil consumption

Rick (
18 to 20, cal OK
2000 miles/quart

Dana Bourgeois (
19, unknown problems may lower reading to 16, cal verified by other

Steve Wynveen (
14 to 14.5, cal verified on boost side
115 - 123 PSI @ 282 rpm
Negligible oil consumption

Chris (
19 to 20, cal verified on boost side
6000 miles/quart (extrapolated)

Chuck (
15, cal ???
2000 miles/quart

Chuck (
16, cal ???

Gene Kan (genehkan@scam.XCF.Berkeley.EDU)
18 to 20, cal OK
4000 miles/quart (extrapolated)

Jason Elmore (
12 to 15 (wide variance, cause unknown), gauge reads 1 PSI w/engine off
95-100 PSI @ ??? rpm
Negligible oil consumption

Spencer Hutchings (
19 to 20, cal verified by another gauge
2500 miles/quart

Dave Roberts (
7000 (3mm apex seal, ported Pettit rebuild)
15.5, Autometer 2401 zeroes OK
8.7-9.3 bar front, 8.0-8.2 rear
5000 miles/quart

Dave Roberts (
???? miles
13 to 14, Autometer 2401 zeroes OK
7.0 bar
Engine failure a few months later
8000 miles/quart

Jake Watkins (
16 to 19, VDO, no other cal info

Andy Goerdel (
20, cal OK (reading unchanged for last 20,000 miles)
6000 miles/quart

Adam Wojciechowski (
18 to 20, Autometer zeroes OK
3000 miles/quart
16, Autometer 2401 zeroes OK

Steve Cirian (
5500 (original engine)
16, Autometer 2401 zeroes OK
Negligible oil consumption

Mike ( a.k.a. Smeagol)
3000 (replacement engine)
18, Autometer 2401 zeroes OK

MIke (
85000 miles (original engine - Mike wasn't this an O-ring failure?)
18, Autometer 2401 zeroes OK

Carl Houseman (
27000 (original vehicle)
16 to 17, Autometer 2401 corrected by 1" based on +.5 PSI zero reading
Negligible oil consumption

Carl Houseman (
45000 (replacement vehicle)
14.5 - 16, Auto 2401 calibrated by another gauge


I'd have to say "almost none". We've got high and low mileage engines with high and low readings. We've even got low vacuum readings with decent compression. If there was any conclusion I might reach - from a survey response of ONE - it's that a reading less than 14 probably means compression is low, which may indicate impending engine failure. Too bad we don't have compression gauges in our cars.

33% have readings above 18" on average
38% have readings 16-18"
29% have readings below 16"

Of those reporting oil consumption and having > 18" readings, 4 out of 6 had oil consumption of 4000 miles/quart or less. Correlation? Maybe but on so few samples it's a stretch (you have to want to believe).

Of those reporting oil consumption and having < 18" readings, 7 out of 8 had oil consumption of MORE than 4000 miles/quart. Another wishful correlation?

All we know for sure is what we knew before... you want your car to have high vacuum, high compression, and you want to burn a measurable amount of oil. I still think many of these cars don't meter enough oil and will be looking into adding 2-cycle oil to the tank as a preventative measure.


Date: Mon, 18 May 1998 14:28:15 PDT
From: "Mike Putnam"

I think one obvious conclusion is, inexpensive gauges are not very accurate. At my work we do a lot of mechanical gauge calibration from $2,000 Heise gauges (ANSI Grade 4A, accurate to plus or minus 0.1% of full scale) down to $100 mass produced gauges(ANSI Grade B or ungraded).

One thing I've seen is the ANSI Grade B gauges, after being in service for a while, fall from an "out of the box" accuracy of plus or minus 3% to plus or minus 10% of full scale. As most of you know, the vibration, shock and heat that automobile gages are subjected to is not kind to gauge accuracy.

What this means is most of the gauges we're all using will be accurate to within plus or minus 3inHg after subtracting any 0 offset they've acquired. So, assuming an average actual vacuum reading of 18inHg for a third gen a random sampling of our gauges will read from 15inHg to 21inHg, throw in the car to car variation and it's easy to understand Carl's results.

Gauge Mounts

I would recommend buying the Pettit mount that replaces the plastic piece that surrounds the steering wheel and houses the indicator stalk, etc. I found that the A-pillar mount puts the gauge in your line of vision if you mount it at the top of the pillar, and blocks your view of the front fender if you mount it at the bottom of the pillar. I used a Dremel tool and cut out a section so it sits lower on the pillar. You could maybe also cut some out of the top to mount it higher on the pillar.

Also, the double-sided tape that holds the A-pillar mount to the pillar tends not to stick very well. I have heard from several people that had similar problems, and ended up with their gauges dangling by the vacuum hose / wires. The fix for this is to either get new tape or screw the A-pillar mount to the A-pillar. I won't put holes in the interior of my car, so that's out. I bought some 3M double-sided tape that has seemed to hold a lot better than the tape that came on the mount.

The downside to the Pettit mount is that it does not have the screw holes like the standard top of the pod has, so you have to glue it in place. (At least on the one I saw.)

Also, Pettit does not sell this unbundled from the gauge, so if you don't like the one they sell, tough luck. Several people said that Rotorsport and maybe Tri-Point sell this separately. I have not called them.

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