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Extra C900 Gauges

I've gotten so many questions on my guages that I decided to create a small webpage about them!
So Here they are...

All the gauges are 2-1/16" in size. The top 3 are VDO and the bottom 3 are AutoMeter Phantom style. All of the gauges require 12 volt switched power, a ground wire and a wire from the interior light circuit. I tied into the light wire above the cigarette lighter. It is nice to use this wire as the gauges will be able to dimm with the rest of the interior lights.

You can buy the VDO gauges and senders from www.sasab.com. You can buy the Auto Meter gauges and senders from either www.summitracing.com or www.carparts.com.

Voltmeter Gauge:

The first gauge I got was the Voltmeter gauge. It's easy to hook up and tells alot about your electric system. I took the 12 Volt source from the cigarette lighter. It usually hangs around at 13-14 volts, but when everything is on and I'm sitting in traffic, it goes down to 12 volts.

There are 2 things to watch for on this gauge. If your voltage regulator is going bad you may see irradic behavior. My was going from 12 volts to 16 volts every 10 seconds. This is not good for the electrical system!

If it reads below 12 volts then either your alternator/voltage regulator is messed up or you're drawing more current than the alternator can put out. Some times the ground wire on the alternator comes loose and it stops charging, also causing this condition.

Engine Oil Temperature Gauge:

This gauge is really more for information than anything really useful. When you need an oil change you may notice the oil temp going up because you're oil is thinning out.

It installs pretty easy. You get a new drainplug that is also the sender. Attach the wire and away you go.
One thing to remember is that the oil is directly affected by the tranny heat. If your oil is 200 degrees, you can bet that your tranny oil is also at least 200 degrees!

In the winter time, this gauge runs around 120-180.
In the summer time it runs about 180-210.
On the racetrack I hit 230.

Oil Pressure Gauge:

This is one of the most important gauges to have. Losing oil pressure will destroy your engine very quickly. This gauge can also help determine how worn your engine is. As the engine bearings wear down, it takes more oil to fill the gaps. This in turn drops the oil pressure. If your car runs below 35 psi at 3,000 rpm, you probably need an engine rebuild.

It installs by getting a special oil pressure sender and taking out the old one. The oil pressure sender is located above the oil filter. You can buy this from www.sasab.com or from a supplier that stocks VDO guages.

There are 2 connections, 1 for the stock light, and 1 for the gauge.


This gauge will read 75 psi when the car is first started. As the engine oil temperature rises, the pressure will drop. At idle, when the oil is at 180 degrees, it runs about 7-10 psi. At 3,000 rpm is runs about 50-60 psi.

Air/Fuel Mixture Gauge:

This gauge is more for tuning the engine than anything else. The gauge will cycle back and forth while cruising. This is the ECU going into a "closed loop" mode. It enrichens and leans the engine trying to stay at 14.7:1 air/fuel. This is normal behavior. If it isn't cycling, then your O2 sensor may need changing or your Air Mass Meter needs to be adjusted.
During high boost, the gauge should read rich. At least 2-3 bars in the green.

The main limitation with the narrow band air/fuel gauge is that it starts to read wrong when the air/fuel mixture goes outside of the normal scope. When you start modifying your car, it is possible to get a super rich mixture and the gauge may tell you it's running lean. For those looking for really accurate air/fuel gauges, you should buy a wide-band O2 sensor and gauge.
To install the gauge you simply tie into the stock O2 sensor gauge.

Boost/Vacuum Gauge:

This gauge well worth the money. This gauge can tell you exactly how much boost you are running. It's also pretty neat to watch the gauge to see it go from vacuum to boost!

It installs really easy too. Just put a T in the vacuum line going to the stock gauge and run it to your new gauge. Now, both gauges still work and you can see exactly what boost your pushing.

Fuel Pressure Gauge:

This gauge is really neat. It rises and falls just as much as your boost/vacuum gauge.

After adding the Rising Rate Fuel Pressure Regulator and bigger injectors, I had no idea where to set the baseline of the regulator. This gauge tells you everything. If you know what fuel pressure you have, then you can calculate how much fuel the engine is getting.
You can also use the Air/Fuel gauge to help you set the regulator. If you notice you are running rich you may either need to adjust your baseline regulator setting, or adjust your AMM.

The install of this gauge is the most complicated. First, it requires a special sender. I decided to build my own fuel line to use the sender. I bought some -6AN stainless steel hose from Summit Racing. I then ordered some fancy host connectors and a T for the sender. Lastly, I bought a new fuel line from Saab and tore it apart to use the fittings to tie it all together. I used Earl's Performance Parts for everything.

The gauge comes with a small box to convert the sender signal and send it to the gauge. All of the wires go into the box and then some wires from the box go into the gauge. The box also requires 12 volts and ground. You hook up the wires from the sender and you're in business!

Fuel Regulator  Fuel Regulator

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