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Exhaust Manifold Pressures

**RB2530**

By **RB2530**,
in Engines & Forced Induction

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**RB2530** Proficient

**RB2530**

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So - how can you measure the Pressure in your exhaust? - Simply tap into the collector or turbo area a flared fitting with 3-4mm copper tubing and run it into a boost gauge. I recommend winding a spring like coil of around 5 loops about 10-20cm away from the fitting to shed the heat from the exhaust gases that feed in the boost gauge.

That would work but the trouble with copper is it is a good conductor of heat (thats why they use it bases of saucepans etc)...One of the worst conductors of heat is stainless steel. So using the principle of the coil would work better with stainless tube...Or instead of the coil you could run the tube through a heat sink...I am thinking for more of a permanent installation..Another problem to overcome is if you mount the sensor or WT tank on the fire wall you will always have flexing in the coiled tube which would cause fatigue...

Anyway I am straying away from using EG pressure as an energy source to pump the water...Not because I dont think it is a good idea but because there would be lot of trial and error in getting it to work right. And there appears to be a huge variance in the ratios between EGP and Inlet pressures...So for some setups it would work well and some wouldn't work at all...

I am considering the following two options.

1. Using a pump such as the Shurflo but setting it up in a return to tank set up.ie the pump outlet goes to a T-peice and then returns to tank. Off the T you have the nozzle or nozzles. After the T you have a device** that acts like a rising rate pressure regulator. This is feed by a pressure signal from the plenum...So as boost increases there is more pressure fed to the nozzle...**Dont know what this be yet..It may be a custom job or it may be an off the shelf pneumatic item...

2. Not using a pump at all...Using a pressure multiplier..This is a setup similar to a brake booster and master cylinder..You have a large diameter piston connected to a small diameter piston..The larger piston is fed by boost pressure. The smaller piston pumps the water into the plenum...The big problem with this setup is that it is obviously not continuous..

The amount of water delivered in any one cycle will be the volume of the small cylinder..The system will reset on gear changes or when throttle is backed off. Vacuum will draw the large cylinder back also pulling the small cylinder back drawing in another charge of water...Depending on what you are doing though it may be problem. If you have 15seconds of water in one stroke and you were doing 1/4 miles you wouldn't have a problem..(you would hope not anyway). If you were doing circuit though you may have any issue on the straights..This problem could over come by using a tandem setup that switches or a double acting piston pump. This gets very complicated and expensive and the economics then don't work..

Both options have the ability to deliver water proportional to boost but I think option 1. is the most feasible...

  • 4 weeks later...
psi Experienced

psi

Posted
Posted

on my dirty old VL, I used to run a small bottle that was pressurised by boost with a one way valve, and I ran a windscreen pump(discovery washer by memory) to a very small agg spray nozzle. the nozzle made a tiny jet of water that swirled/spiraled. When the jet hit something, the stream exploded into mist.

I fitted this set up with a pressure switch and ran mostly water/meth through it. It sprayed onto the wall of the pre-turbo piping.

1: very crude, but worked a treat (until water ran out!)

2: never noticed real damaged compressor wheel.

3: water pressure wasnt high enough, sometimes got water droplets on the side of the pipework.

4: needed a much higher pressure pump to make a better mist.

5: The added boost pressure made a HUGE difference in the queality of the mist..

6: The next owner pulled it down to port the head and said that every thing inside the whole engine was SPOTLESS! He said the valves looked like they had just been installed and the pistons looked brand new! hahaha, not bad for an engine with 310 000km on it!

Yep, I'm a fan of water injection, from the power increase ability of it, and also at keeping everything so clean..

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