Thread: New type of BOV
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BoxxerSix BoxxerSix is offline
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Join Date: Jun 2006
Location: Ballston Spa, NY
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Anyway onto the valve "fix". After discussing this issue with the aviation guys the idea came up to attempt to vent off and control boost pressure through the DV valve. I won't get into the details of the valve itself, but it does have the ability to act as both a "wastegate" and a diverter valve/BOV simultaneously with some creative plumbing and simple electronics. It was never designed with this application in mind, it was just something we figured out along the way and managed to make it work. The patent for the valve is available online to read for more details.

As Goran stated(correctly I might add) one root effect of venting boost pressure like this is you essentially shift the operation point of the turbocharger in the compressor map towards the choke. In just about every application this is not beneficial however that was was we trying to do on this car. By "shifting" the map you could say, the operation area of the turbocharger shifted away from the surge line of the map in an hypothetical attempt to keep the compressor well within the efficient area of the map during this low-to-mid level throttle modulation under light engine load. Blah blah blah right? Anyway at this rate one could easily say the simple fix is to change out the turbocharger to a properly sized unit. This is true to some effect, however even the like of the 2871/76R's have this problem. Car equipped with 3071/76R and larger turbos seem to be immune from this(hypothetically due to the map changes), however these options completely kill low speed drivability and cost in excess of $3-4K for a kit, plus install. 90% of Evo owners don't want this option and need a simpler, cost effective solution that retains the stock turbocharger. Whatever the reason being, what I have done has effectively eliminated this problem and the car now runs fantastic.

Onto the other tidbits with tuning/dumped air/etc. At the begining of this valve idea I was well aware of the fact that the car would run rich due to the metered air being released pre-throttle with meter fuel being dumped into the engine. For once though e one must thank Mitsu for programming the stock computer as well as they did. The system is completely open source tunable, with the ability to rewrite the software in areas with different variables to suit ones application(up to a certain point that is). Needless to say, the correction and compensation for this 'air dump" has been fully tuned for and the fuel curve is as if the car was running your typical wastegate/bov setup. The car still does have the functioning turbocharger wastegate in conjunction with the "BOV wastegate" Both have their own separate boost controllers. Due to the readings from the optical RPM reader, post IC boost gauge, plenum boost gauge, pre IC charge temp gauge, and the divorced o2 housing with atmospherinc dump I know that the turbocharger is operating well within it efficiency range and that the wastegate is still operating as normal, regulating CHRA speed.

....side step here....the whole idea for operating the turbocharger at an increased boost level over what was required came from the aviation guys who have used this setup before in high altitude enviornments. Again as Goran said this would probably work on something that used an oversize turbocharger compared to engine volume. This idea was tried to see what it would yield on the car to this issue and showed no negative results aside from a 27 degree increase in charge temp over the 25psi boost level. If either way the 27 degree hike pre IC made no difference by the time it reached the stock IAT sensor after passing through the intercooler on this car. I have no intention on keeping this setup with this option, but wanted to pursue all avenues to eliminating this problem. Also as a note, in my previous post I think I posted that I had the turbocharger running at 29psi with the valve at 24. Mistype on my part as it's running 25/24psi.... turbo/valve.

Oh I'm getting lost in my own post here now I'm must say that I had no intention on raising a fuss with this little BOV thread here and never intended to insult people intellect on this subject. I'm just trying to say that whether it just be the circumstance and variables surrounding this car in particular, this setup is working, is tuned, and so far has not shown any detrimental signs. The turbocharger is still functioning in it's efficiency range and CHRA speeds. I had no intention to say that it would work in a p-car standpoint, or any other car for that matter, but to just rather point out the inginuity of the valve in general.

As another side note I think someone asked how I was able to make the valve function as both a "wastegate" and DV simultaneously and it really revolves around the internal makeup of the valve actuator and a simple system i whipped up composed of an adjustable vacuum/boost switch, check valves, and a solenoid to control where and when boost and vacuum reference signals actuate the valve. It simply dictates when the valve will see each signal, and what port(s) on the valve that will get those signals. By varying these signals to the port in different "combinations" the valve functions differently. Really sounds more complicated in text than it is in reality but wouldn't work with any other valve out there.

Ah I really don't know what else to post or say. I'm so lost in my own post here that I hope I didn't lose any of the people that were keeping tabs on this

I hope this helps clarify a few things here. I know that what Goran said was all true, I do this stuff too for a living. It's just that in this very specific application, the negatives of this setup seems to become positive and the ability to tune the car for it make it an avenue to pursue. Do I recommend you go do this on your car? Absolutely not. This is just an attempt to remedy an extremely common problem amongst the Evo community with a relatively cheap and 100% effective means of eliminating the problem for those that want to without resorting to expensive and daunting changes in turbochargers and the associated ancillaries that go with such a swap on these cars.

I'm pooped out

Please feel free to debate this. It's what we're here for. Debates are how I learn alot of my s**t as well so I like doing it. Also if there's something that needs better clarification please let me know and I'll jump in an do so ASAP.

-Best Regards,
Adam Hennessy
Old 01-28-2008, 07:52 PM
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