Fit a Boost Gauge to a 165

Why do I want to fit a boost gauge?

To see what sort of pressure the turbo is making. To accurately see the pressure within the intake manifold.

What if I don't want to fit a boost gauge?

If you are going to modify your car and aren't going to get a boost gauge I would call you a fool. Get a boost gauge.

Isn't the stock gauge good enough?

No. Where are the graduations? Is it calibrated? What's the scale? In a nutshell the stock gauge is very poor for tuning purposes. The stock gauge just shows you that you have "some" pressure being produced by the turbo, and what the TPS is sending to the ECU.

Where can I get a boost gauge from?

Try the shops section from the links.

I see the shops sell 2 kinds. What are they?

• Electrical. Works in a similar fashion to the stock gauge. A transducer, or sensor, converts the pressure in the manifold into an electrical signal which either swings a needle on a dial round, or feeds into a digital display.
• Mechanical. An air line is taken from the manifold to the gauge to read the pressure. Here the pressure is felt directly at the gauge and converted to swing a needle around. I prefer this sort as there can be no funny business i.e. no interference with electrical signals, shorting of signal lines, no drilling and tapping the manifold etc. I prefer to have a boost gauge that is physically reacting to the pressure in the manifold.

The choice is yours, but I recommend a mechanical gauge.

How do I connect this up?

The mechanical gauge relies on a pipe which is attached to the manifold and run into the cabin area to the back of the gauge. This is connected to the manifold either with a length of semi rigid pipe or vacuum hose. I prefer semi rigid pipe as this is less likely to suffer from kinks or twists which may stop the pressure being transmitted up to the gauge.

The electrical gauge needs a transducer bolting into the manifold and then a wire run to the back of the gauge mounted in the cockpit.

All boost gauges should be fitted after the throttle body.

Anything else I should consider?

• I would recommend purchasing a psi gauge rather than a bar gauge. I find that reading a psi gauge is more accurate than a bar gauge i.e. my boost pressure is 17psi rather than "1 point...er...2...ish bar".
• A bar gauge is clearer to read as it is less cluttered than a psi gauge, and often comes with coloured segments on the dial for easy and quick reading.
• Make the pipe/wire run as short as possible to avoid any losses and improve reaction times. Watch out for any sharp corners or burrs. Try and keep the cable/pipe neat and tidy, cable tie in position if necessary. Keep out of the way of the pedals and steering.
• Do not kink or twist your pipe work if you are installing the mechanical type boost gauge. The gauge will either be slow to react to boost pressure changes or will not react at all!
• If you cannot find a spare connection onto the manifold you can always insert a T-piece into one of the pressure lines. However, avoid using the FPR connection as this may interfere with the fuelling! Why do I mention avoid using the FPR line? The fuel pressure rises with increasing boost pressure. If the line falls off the FPR regulator then you run a high risk of supplying insufficient fuel - this can lead to detonation and a new engine.

Okay, got the background info. How do I fit a mechanical gauge?

Follow this boost gauge, (BG), installation procedure. Note this was fitted to a UK car and utilised the semi rigid pipe...

	Find either a hose you can cut and put a T-piece into, or connect up to the blanked unused connection on the left hand side of the manifold. The arrow points to two manifold connections. One is for the FPR and the other was originally an unused and blanked off connection. Note this is shown with a red hose attached
	A better picture of the two connections on the manifold
	Find a position in the cabin to mount the bg - I suggest on the right hand side by the air vent. Alternatively, you maybe able to purchase a tailor made pillar mount gauge holder from Hyper Sports. At present they manufacture these for the 185 and 205, but they may be able to provide a 165 mounting arrangement...
	Run the solid bg pipe from the back of the bg down the right hand side of the drivers side door shut - you can sneak the pipe under the panel to snugly fit the pipe out of sight.
	Run the pipe across the underneath of the dash, taking care not to foul any steering component and then forwards to the firewall, staying clear of the pedals and up to the left where there are two rubber grommets. Cable tie the pipe in place to prevent any fouling of the steering or pedals.
	Inside the engine bay the two rubber grommets are located behind the intake manifold. These have little in them and make idea spots to break through into the cabin area.. It is easier to locate these grommets by pushing through a piece of wire from the engine bay into the cabin. You'll find them easily that way. The 2 grommets are arrowed in the picture.
	Pull the pipe through the grommet and connect a length of silicon vacuum hose between the solid pipe and the manifold connector. Ensure this will not come off or you will have an air leak and the car will idle badly. The solid pipe is black and is arrowed as it passes through the grommet.
	Double check your connections, ensuring that the boost gauge pipe connector is tight, the pipe work is clear of the pedals and is securely attached to the manifold
	That's it! All that remains is to test the gauge works. Start it up and you'll notice that there will be a vacuum indicated - normal. Take it for a run and watch the gauge as the turbo spins up, you will notice the gauge rises into positive pressure take a note of you maximum pressure
	If you haven't done the TVSV mod yet, you will notice how the ECU raises the boost in 3rd gear. Disabling the TVSV will run the same reduced pressure in all gears...but this requires to be disabled if you increase the overall pressure with e.g. an RV

Any questions or comments then please feel free to e-mail me

Other jobs to do at the same time?

• Disconnect the TVSV to achieve the same boost in all gears - you'll require a Relief Valve or similar to fully take advantage of the removal of the TVSV. Note - the TVSV when activated (in 3rd+ gears for 165 and 185, 2nd+ for the 205), allows for extra boost pressure to be run ~2psi. Simply disabling the TVSV with no other method of controlling the boost will cause your car to be slower i.e. to never run the "little bit extra" boost pressure in 3rd+ gears(165 and 185) or 2nd+ gears (205).

Any other points of interest?

Watch how slowly the dash pressure gauge rises in comparison to your lovely new boost gauge.

Top of page