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mike01s4's Audi fitment Diverter Valve Testing:
by Mike Shimon (VAST Performance)

All tests were done off the vehicle.

Diverter Valves tested: Some purposes of test: Some test equipment: To obtain the data for displacement(piston travel) versus vacuum pressure, I applied a vacuum in a slow fashion in ~0.5 in. Hg steps. The vacuum pressure was increased until the piston would not travel any further. I also noted whether or not the valves stuck, or had an inconsistent pull, or leaked. I took two to three trials for each valve, and the measurements were quite repeatable. I obviously could not simulate the ON-vehicle pressure fluctuations and measure displacement.

The forge valve needs the most amount of volume displaced in order for the piston displacement to achieve a full open state. This is a point where the Bosch bellows style diaphragm design is superior. I am making an educated guess that the Bosch will respond quicker to opening due to this fact, albeit, it will probably be only milliseconds faster. Also, it looks as if the 110/710N will take a longer time to open, but, just because it comes open a few in. of Hg later, the typical vacuum pressure developed can be ten times this difference. So there should be no worries with a slow response time with any of these Bosch valves.

One thing that I could not check, is the reaction time for the valve to close after a full open state. But, since the spring rates are now apparent for each valve, all other things equal with the Bosch's, you can see that the 110 and 710N will close the fastest. The forge's closure rate will not only depend on the spring rate, but also the grease used and temperature. With insight from this plot, the forge will close the slowest, then the stock 108 is a bit faster, then the 110 and 710N are the fastest.
Between the 110 and the 710N, you can see that they are exactly alike. Unless Bosch changed the materials used in fabrication for the diaphragm, these valves are totally equal. I did not destroy the valves to inspect the differences since I was using other people's parts and it would cost around ~$50 to do so.

I also checked the ability to open under a cold test of 20 degrees Fahrenheit. The Bosch valves would stick, but only occured once, and only once, on an initial applied vacuum. So, cold runs in the vehicle should never even be a problem. The forge did not stick. I did not know what the relative humidity was when I did this.

As far as diaphragm or piston leakages are concerned. None of the Bosch valves leaked. How they perform after many cycles in an engine's environment, I could not say, but they will not leak unless the diaphragm tears or if the housing cracks. It is very easy to check leakage. All that is needed is an applied vacuum and a little time spent on looking to see if the vacuum drops with time.
On the other hand, the forge will leak if not sealed properly or contaminated by debris. From the opened valve picture, you can see where the Forge can leak. All that is needed is a cleaning and a slight medium to heavy weight grease to seal this. With the Forge, I noticed anything from a near perfect seal, to a low of ~1 psi loss per every 5 seconds and then much worse as a small particle contaminated this seal.
On to the flow rate tests, I found that the bosch and the forges still have the same flow rates while testing with a complete inner fill of water flow. With the valves completely opened, each valve could fill 20 fl. oz in approximately 8 seconds. Of course, even as I put restrictions on each valve, maintaining the same inlet pressure, each valve still achieved the 8 second value, obviously with a greater exit speed.

http://www.s4biturbo.com/files/DV_piston_plot.jpg


Summary

FORGE:
Pros: can maintain it at any time
can replace spring with a higher rate
virtually a lifetime part
smooth/open air flow path when compared to bosch, BUT, still has the same flow rate up to a typical working pressure
comes with viton O-rings which have superior temperature and wear characteristics

Cons: price
fitment, due to larger size, is not as good as bosch(the passenger side vacuum hose can easily kink if not installed carefully)
slower response time
can have an inconsistent piston travel if not lubed properly or not maintained
possible sealing issues if not kept clean

http://www.s4biturbo.com/files/forge_open.jpg

http://www.s4biturbo.com/files/forge_side.jpg


BOSCH 108:
Pros: price
slightly higher spring rate than forge
quick response time for opening
no fitment issues
no warranty issues

Cons: cannot inspect or service valve completely
possible problems noted with many users for diaphragm tears
max piston travel, for its design, is not as large as the 110/710N
air flow path not as smooth as forge, but still has the same flow rate up to typical working pressures

http://www.s4biturbo.com/files/bosch_side.jpg


BOSCH 110/710N:
Pros: price
larger piston travel compared to stock
with a small bellows volume: quick response time for piston pull
with a higher spring rate: quick response time for piston closure
possibly more durable than stock
no fitment issues
no warranty issues

Cons: cannot inspect or service valve completely
air flow path not as smooth as forge, but still has the same flow rate up to typical working pressures
2/25/02

Update: 03/05/2002

This new graph includes the piston travel for different spring rates with the forge DV. there are 3 springs: green(comes standard) = softest, yellow = medium, and blue = stiffest. for all practical purposes, you can see with the yellow spring that it performs like the stock 108, and with the blue spring, it performs like the 110 or (114)710N valve. Basically, the downside with the stiffer springs in the forges as compared to the bosch is that you are slightly reducing the response time of the valve even further. This is due to the fact that the bosch valve needs a smaller volume of air displaced to pull its piston open or force it closed.

http://www.s4biturbo.com/files/dv_piston_plot_2.jpg




mike01s4's Audi fitment Diverter Valve Testing Part 2:
by Mike Shimon (VAST Performance)


Did some more BPV checks....some interesting/conclusive info... thanks KENT L & LOSGATOSS4!!!!!!! for sending the samples for my destruction :) last time I posted about all the different valves (bailey excluded) and the only thing we couldn't talk about was the internals of the bosch valves. So the point of this is to compare three Bosch DV's and note their constructional and material differences and similarities and qualities.
So here it goes,
Valves checked: I sawed off the top (piston chamber side) of each of the above valves.
From my previous post, all signs indicated that the 110 and 114(710N) were the same exact valve due to the exact same spring rate, max displacement and piston seating, etc. Now, I also noticed that the diaphragm was made of the same exact polymer material with the same exact thickness and the same construction with the same brass stopper. So, even though there are two different part #'s, they are totally the same.
I cut away sections of the diaphragm and mic'd them up. The diaphragm thickness for the 110 and 114(710N) is as follows: 0.0200" - 0.0205"

http://www.s4biturbo.com/files/bosch...nstruction.jpg

I then took apart the stock 108(710A) valve and analysed it in the same manner. The brass piston stop is taller, (hence, the lower displacement value as noted in my first tests). Also, the diaphragm material is thicker: 0.0240" - 0.0245". This is substantially thicker than the valves that we are all upgrading too, and it mislead me for a moment. But, as I pulled away sections of the diapragm for testing, I noticed that the stock material tore very freely, while the 110 & 114(710N) was more elastic and resisted tearing even along an initial cut. I then applied the same force to the piston hats for each valve and noticed that the stock valve diaphragm just gave way very easily and I was able to rip it right off while I was struggling to tear the 110 & 114(710N).
Also, with the upgraded valves, Bosch cut some costs with reducing the thickness of the brass stopper and most likely reduced costs with using a thinner, but stronger diaphragm material. The last difference is, of course, the higher spring rate and larger piston displacement with the 110 & 114(710N).
(shorter brass piston stop for the 110 & 114/710N allows ~0.050" more travel)

http://www.s4biturbo.com/files/brass...er_compare.jpg

(thicker, but weaker stock material on top compared to the 110 & 114/710N thinner/stronger material on the bottom)

http://www.s4biturbo.com/files/108_1...gm_compare.jpg

(valves disassembled. note how i was able to rip the diaphragms right off with the stock valves)

http://www.s4biturbo.com/files/dvs_open.jpg

So that's it folks, you don't have to guess anymore, when buying these valves, I hope!

05/13/02

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