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Your tests are quite interesting...Actually similar with what I found as well but the practical result of the use of the Dawes Style MBC is quite different and yields a better result than your(and my) benchmark tests.
What model Norgren valve did you test?
Here's some background info on the norgren valves...
Talked with Bob Buck at Norgen at length about their valves in general. A 0-5 psi spring will regulate pressure from 0-16, 0-10psi spring will actually regulate pressure from 0-22psi. A 0-25psi internal spring will regulate pressure from 0-46psi. A diaphragm style pressure relief valve will actually release gradually as well. It will regulate better than a ball and spring style relief valve but it will open ealier but relieve less. It is interesing that 2 major MBC manufacturers (HKS and Turbonetics) use norgren valves as their MBC. The HKS uses the v07-100-NNAA which is a pressure relief valve with 1/8" porting, non-relieving valve. The Turbonetics is a R07-100-RNTA which is an air pressure regulator with 1/8' porting with a 0-25psi rating that is relieving. This valve, which makes no sense as to why they chose that one to use. High range, and relieving.
I have had 2 people who bought these MBC's(and paid a lot of money for them) switch to the Dawes Style MBC and totally love the difference that the Dawes MBC stating that the Dawes helps the turbo spool up faster and doesn't have the overshoots that the HKS and Turbonetics had. Both of them switched to the MBC+A setup and thought it was well worth the switch. Interesting being that they paid nearly twice as much for just their old MBC.
What would be an interesting test would be to take some pressure readings with your gauge if possible, pre-MBC off the low pressure side of the turbo. You would be focusing on the pressure build through the rpm range. I theorize that the pressure would be low until the tubo gets moving, then it would come on strong and open the MBC quickly. But the split second it takes for the MBc to stay closed long enough to reach the cracking point would be less than the gradual release of a diaphragm style relief valve or an APR.
I have tested a number of other ball and spring style MBC's as well in this fashion and found that they tended to have a stiffer sping which meant that it could withstand a high psi but it would be less sensitve to the cracking pressure and open too late. Some use an adjustable bleed port, whcih again don't help with the nasty overshoots and works differently than what the company claims it is supposed to be used for. The dawes style MBC was very curious to me on firts inspection in that the spring was so much softer than that of the other MBC's I looked at. But it compenstates with a smaller inlet and outlet barbs. If you were to put a 1/4 ID barbed fitting, the dawes style MBC's peak pressure would be less. If you open up the outlet port to 1/4 in, the WG gets pressure earlier and opens sooner(too soon). The optimal ID barb size for the Mahon/Dawes Valve is exactly what it used. A smaller than 1/4" barb on the inlet and the stock outlet on the sinde of the valve. I have found a way to preserve the stock outlet while increasing the outlet barb to batter match the saab stock hoses which doesn't effect the outlepressure at all but this took many attempts and many valves ended up in the trash bin before I found the best combination.
The Norgren stuff is decent low cost stuff and their testing seems pretty good as well. It is amazing that the big turbo companys(HKS and Turbnetics) use a Norgren Valve as thier MBC. HKS at least had the right idea using a pressure relief valve but Turbonetics??? Can't understand their philosophy. Then there is the issue of the bleed port for thier units which allows the WGA to snap shut when you get off the throttle. One uses a one way check valce to make it happen, the other relies on the reliving nature of the valve which is a bad idea.
Anyway, try the test above and let me know what you find. In the meantime, the Dawes is still the most sensitive, most reliable, and quickest reacting MBC I have tried to date. Doesn't mean their isn't a better one out there, but it doesn a great job for the low end. Up high at 19psi, it would probably not do as well. But there are options for increasing the internal spring rate without jeopardizing the sensitivity of the spring.
posted by 208.235.174...
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