The V8 Owners Forum -

Interesting thread, I've been directed to it by another member on this forum who knows we've build a bench ourselves incase hlp could be offered. For starters to aid you you may wish to have a look here http://www.tractorsport.com/cgi-bin/for ... nboard.cgi

What I'm trying to figure out is whether you are building a pitot style bench or an orifice bench. As you seem to be mixing and matching. However to get an orifice style bench to work correctly you need large settling chambers to stabilise the pressure differential. Otherwise your figures are going to be jumping all over the place.
Likewise you will find that 4 motors is not going to be sufficient. I'm running 8 x 1200watt motors in our inhouse homemade unit. Running digital manometers fully callibrated to superflow spec and struggling to pull over 252cfm @ 28" pressure drop on intake and when flowing on the exhaust we can hit 264cfm @28" (blowing instead of sucking). As the callibration orifice must be razor edge for maximum accuracy however it is always going to flow better in one direction over the other due to flow characteristics.
On 4 motors we struggle to make a 100cfm @ 10" which most standard vw/audi heads outflow (specialise in VAG) in standard form.

If however you are using a pitot style bench you want to be changing the design of your tubes and use pitots instead of an orifice. in which case you now have to have different diameters of tubing for different flow ranges.

I'd advise you have a good read on the forum before you continue and work out which route you are taking if you wish to be succesfull.

HTH JP

Hi there, thanks for the advice. I have been looking at that site and some others online with interest. Many of the designs I have got from the net include multiple orifice plates and in some cases valve plate arrangements where sliding panels can be moved to change the direction of flow etc. Most of these designs are based around a cabinet design of one sort or another. My own design is much more basic and should allow me more room for "adjustment" if not immediately successful. I am building an orifice bench, not the pitot style bench. My design is only capable of pulling air through the head - to test the exhaust the head must be re-mounted accordingly. I had planned to use use a section of 250mm gas pipe to make a settling chamber, the same diameter I used to construct the oriface chamber. Interestling enough I have recieved conflicting advice regarding settling chambers. Someone I know has suggested that the pipe will not be large enough for this purpose and another person whose opinion I respect believes I will not need one at all with my design. I have therefore decided to press ahead without the settling chamber to start with knowing I can add this later if needed. With regard to the motors, no I won't be pulling 250cfm @ 28 inches with 4 x 1400w. I have built the pump with the capacity to take an extra 2 motors if needed but I have to be sensible with my power supply. I think it'll be fine if I don't fire up all the motors simultaniously but I still wouldn't feel too comfortable running 8 motors as you do. Are you using the FP1 electronic manometer? I had planned to use this unit and run traditional manometers as well for comparison. I thought it would be interesting to do so but have decided to ditch the old style manometers completely and just run the FP1, it'll be less grief for me in the long run. Please feel free to drop me a pm or an email, all advice is gratefully recieved! If it's not too inconvenient for you perhaps I could drop by and take a look at your bench?

Ok I see what you are getting at. The larger a settling chamber is the less turbulant the flow around the sensors giving a more stable reading. However you will benefit from placing baffles in line with the orifice plate to allow even pressure distribution through the settling chamber othewise the air will go straight through the orifice plate and give false readings.
As for my 8 motors they are each wired individually into an 8 way switch panel each to its own individual breaker in the main circuit.
Originally I was going with traditional manometers but decided to opt for the FP1 with the extra velocity sensor. It comes with a callibration plate to allow you to set your bench up. I've verified my results with someone I know who has a superflow 110 and the difference in readings is neglible 1to2cfm on average which you can get of doing different pulls at different temperatures in the workshop. So I've decided it is as accurate as. The other benefit is you make 1 orifice plate and you are done for the whole range as the digital is much more accurate in the 10-50% range over a traditional manometer which you have to aim to stick in the 60-100% range of the orifice.
If you couple the FP1 up with Larry's FPExcel spreadheet then your laughing as a lot of the maths involved is degree level so it get's you to grips a lot quicker with the concept of some of the formulaes if you didn't go past A-Level. If you didn't do A level maths then start learning
All I say is been doing heads many a year and a flow bench taught me a couple very important factors the main one which is that it's the little things that matter not the big things.
One more thing to remember is that different heads will require different adapters to the bench and also require different methods of lifting the valves at 50thou increments. Try doing a 1.8T 20v where you have 3 intake valves at 2 different angles that all need lifting simultaneously at 50 thou increments

Hows the progress going?

I have also joined the flowbench forums and will probably get a set of Bruces plans in the next week or so and I am collecting some motors and MDF at moment.

The FP1 certainly seems an easy way to go with regard to data logging and with the US exchange at the moment quite appealing.

Far too much to read up on at the moment getting completely crossed up with it all.

Cheers

Andrew

Hi Andrew, yeah it's moving along slowly. I've been having enormous fun getting to know my welder recently and that has been taking up much of my time. I have installed some baffles in the oriface chamber as advised above and found a good pc (1800mhz + XP included) for £59 and got a mint 17" crt monitor for £2.50!!! (no-one wants these anymore ). That's well up to running all the software i'll need in the workshop and i'm tempted to stick 10gig or so of music on there too! I have also bought some piping and bends that I needed (£11.50). I must say that the more time I spend on the flow performance website the closer I get to not only ordering up the FP1 but going the whole hog and getting one of their kits that includes the pitot tube and the clever air valve that can also be controlled by the FP1 to reach desired pressure easily. Total spend now £213. I had hoped to keep this budget under £500 including FP1, but if I ditch my oriface chamber and go with their full kit we could be looking at a fair bit more. Still only a fraction of the cost of buying a bench of course.

My initial costs came in at around £1800 incl all the necessary adapters for the different heads.

I am about to rip the bench apart tonight though as I've managed to firstly outflow the capacity of the orifice plate (272cfm)and in the process have burned out 3 motors. So I figured I'd swap the whole lot in one hit.

One lesson I have learned is that you'll want a start up capacitor on each motor as this is where I went wrong. When you got 3 to 4 motors pulling vacuum when yuo come to switching more on the initial curent is not enough to kick start the motor this means it stalls and burns itself out. So an important lesson learned that I thought I'd pass onto you.

Just ordered a set of PTS bench plans and picking up some motors in the week to get the project on the way.

Given myself until March to get it complete and up and running.

I will take on board the tip regarding the capacitors for the motors and see if the electronics wizz at work can knock up a circuit for me.

Cheers

Andrew

Very simple just need some 250v .022micro farad caps wired inbetween the live and neutral. Also use independant 1.5mm2 3 core flex not multi core as all my wiring had fused together from the heat. Likewise the inside of the MDF was scorched from the heat so try and run some heat sinks of the metal casings of the fans.
Lastly but not least pop rivet the vacuum motor ends into place as these had all come of as the plastic of the motors had distorted. The saving grace was that they where all clamped tightly into place. I'm happy I pulled the bench apart when I did though as much longer use could have resulted in some serious fire hazard from the molten wiring.

Are you runnig all 8 motors off a single phase supply? What is your supply rated at? I've got a 10mm line on a 32amp breaker that is designated for the bench. Surely this should be ok if fused properly and caps used as described? I may step up to 6 motors but not 8 at the moment.

My workshop has a 100a rated domestic supply fuse box of which I've dedicated 8 breakers (B10's) individually to the each motor to basically prevent the whole bench becoming inoperative in a case like mentioned above. Sort of belts and braces concept really. If running upto 4 motors so long individually switched you can easily take them of the sockets as the main ring should be 32amps and the draw is about 5amps on each motor.
I personally decided to wire up all heavy equipment like pillar drill, laithe (3 phase converter), compressor etc on their individual circuits to avoid the whole place cutting out if something goes wrong. Nothing worse then burning a motor out on something causing your computer to switch of

So whats the latest update on the bench? - Must have been a bit of time spent tinkering in between the Mince Pies and Sherry

My plans arrived today

Cheers

Andrew

Cool! which plans you got? I've sort of put this on hold for a sec while while xmas consumed all my spare cash for the last month or so, although I have moved on a bit since my last pics, will try to get some updates posted this weekend although i'm due to work sat & be hungover sun so we'll see! I have also I must admit been very tempted to change the design somewhat. It was allways my intention to use the FP1 but I am more tempted to go with one of their full kits that include the air valve and pitot tube. The main reason for this is that I really want the air valve now so might as well go the whole hog. The other good reason is that the arrangement would take up half the space. Two slight problems here are 1) this approach dosen't sit comfortably with my original intention of doing this on a sensible budget and 2) I am not In a position at the mo where I can just throw some extra cash at it to make life easier anyway!

I bought the PTS flowbench plans - which are designed around the FP1 and the air valve system - but I may well start off with a couple of manometers until the finances allow purchase of the black box set up - Although I suspect that an electronics boffin is working in the back ground to produce a DIY kit for the electronics as well.
I picked up 5 new motors for £40 and looks like the bench MDF will come in at about £80 - electrics etc. I am budgeting on about £50 orifice plates I will machine up at work for free as will most of the manometer equipment. rumour has it that there is nice incline manometer in the warehouse somewhere....
My Dad is a retired carpenter so he is building the cabinet and a good friend owns an irrigation company so I am hoping to get some cheap check valves and any other valves I need.
I have a stepper motor drive butterfly valve that I may try for the air valve when I start playing.

The PTS bench has great support on the forum and now they are being built there are plenty of in build photo's and advice.

Cheers

Andrew

Any news on the bench?

Andrew

Not a lot has happened lately re the flow bench. I've been pricing up a couple more motors to add to the four I got already. It seems I picked up a real bargain @ £16ea on the first four, best price I can find now is around 35-40 quid for genuine units. I'm waiting on a tax rebate that I hope will pay for my FP1! I have however found a very interesting product called "Vinamold" that is used for taking molds. It comes in 1kg blocks that you melt down in a pan. I'm looking forward to having some fun with this stuff. I also found a great supplier of burrs in the states. He's got 3mm shank burrs for the small grinders in a handy 80mm length. They work out at about £1.25 each and although some are used they are still in vgc. I can pass on the guys details if anyone is interested.