Rally205
20-09-2005, 03:09 PM
After having read a very interesting article about Negative Boost or intake restriction I decided to measure the restriction on my own car and see just how bad the VR4's intake is.
I built my own Manometer in true Blue Peter fashion using an old pop bottle, a stick, some windscreen washer hose and some coloured water. The next decision was where to measure the pressure drop in the intake system. I decided on one at entry to the front turbo and another on the rear turbo to give an overall figure and then one in front of the air filter to measure the intake snorkel and another in the air box after the air filter to measure how restrictive the standard filter element is. I also placed one just after the 'Y' pipe to the front turbo as I thought that it may be a restriction.
All I did for the connections to the manometer was to drill a small hole at each point and glued a small plastic nipple into the hoses and airbox. I then ran the washer hose back into the car and enlisted the help of a friend to read the measurements whilst I drove and called out the revs. We measured all points in 3rd gear, full throttle and at every 1000rpm increment. After one measurement was done I stopped the car, popped the bonnet and moved the pipe to another measurment point.
The results were a little tricky to observe as at the turbo inlets the pressure drop is so much that it sucked the water right out the top of the manometer and nearly into the engine /help. It was also tricky to get a full throttle reading at 2000rpm so we started at 3000 and upto the redline.
So the results were:
Front Turbo Rear Turbo
Revs inches of water Revs inches of water
3000 15 3000 14
4000 32 4000 26
5000 40+ 5000 36
6000 no reading as off 6000 40+
scale at 40.
Before Filter After Filter
Revs inches of water Revs inches of water
3000 4 3000 4
4000 7 4000 10
5000 10 5000 15
6000 11 6000 14
7000 7 7000 10
After 'Y' Piece
Revs inches of water
3000 7
4000 11
5000 20
6000 30
7000 23
So it would appear that the standard air filter is very efficient and does not cause much restriction. The higher the number the greater the restriction.
That horrible plastic pipe going to the front turbo that looks very restrictive actually isn't much worse than the nice large round pipe going straight to the rear turbo and the worst offender is the 'Y' piece.
I will also try a measurement just after the MAF to see how restrictive that is.
Now I will use my manometer to find the stagnation point on the front of the car and see if I can get some positive pressure in the airbox /Hmmm
I built my own Manometer in true Blue Peter fashion using an old pop bottle, a stick, some windscreen washer hose and some coloured water. The next decision was where to measure the pressure drop in the intake system. I decided on one at entry to the front turbo and another on the rear turbo to give an overall figure and then one in front of the air filter to measure the intake snorkel and another in the air box after the air filter to measure how restrictive the standard filter element is. I also placed one just after the 'Y' pipe to the front turbo as I thought that it may be a restriction.
All I did for the connections to the manometer was to drill a small hole at each point and glued a small plastic nipple into the hoses and airbox. I then ran the washer hose back into the car and enlisted the help of a friend to read the measurements whilst I drove and called out the revs. We measured all points in 3rd gear, full throttle and at every 1000rpm increment. After one measurement was done I stopped the car, popped the bonnet and moved the pipe to another measurment point.
The results were a little tricky to observe as at the turbo inlets the pressure drop is so much that it sucked the water right out the top of the manometer and nearly into the engine /help. It was also tricky to get a full throttle reading at 2000rpm so we started at 3000 and upto the redline.
So the results were:
Front Turbo Rear Turbo
Revs inches of water Revs inches of water
3000 15 3000 14
4000 32 4000 26
5000 40+ 5000 36
6000 no reading as off 6000 40+
scale at 40.
Before Filter After Filter
Revs inches of water Revs inches of water
3000 4 3000 4
4000 7 4000 10
5000 10 5000 15
6000 11 6000 14
7000 7 7000 10
After 'Y' Piece
Revs inches of water
3000 7
4000 11
5000 20
6000 30
7000 23
So it would appear that the standard air filter is very efficient and does not cause much restriction. The higher the number the greater the restriction.
That horrible plastic pipe going to the front turbo that looks very restrictive actually isn't much worse than the nice large round pipe going straight to the rear turbo and the worst offender is the 'Y' piece.
I will also try a measurement just after the MAF to see how restrictive that is.
Now I will use my manometer to find the stagnation point on the front of the car and see if I can get some positive pressure in the airbox /Hmmm