Stock TB and bov vs TB on mp62.
 

results, in photo (mustang dyno, add 20% minimum for real hp/ftlb)

on top of more power the throttle response is 100% better

Attachment 188248

What size bov did you end up using? Recirced? Have a video of how loud it is now?

Just for power number comparison, I work at a shop that has a mustang dyno. We had a customer with a 94 rotrex setup (he may choose to chime in here). He made 196 on our dyno, and 226 across town on a dynojet.

Also, why did you choose to run the throttle body setup this way? Even when it is the norm to never ever run a pre-TB roots blower. I'm not criticizing, just always heard to never do it this way. Supposedly to prevent compressor surge which can destroy the rotors.

no recirc all open air as the blower pushes enough air to never have intake air coming from the bov. Bov is a loner but is the Mitsubishi that comes with the begi kits.

Can't afford a dynojet run so running off predicted hp. With original tb set up there was a log of throttle lag because of the delay from pressurizing the fmic, piping and intake. With the blower running with the bypass valve open there is still enough air being pushed out the blower to keep the fmic precharged and all the extra air is pushed out the bov tell it closed with throttle. then when off power the bov works the same at a turbo set up and keeps the equivalent to compressor charge from happening. with this set up it's like having a 300hp ITB set up with the uber torque of a twin screw.

Hmm.. good to know. I was just giving you the numbers comparison for general info. Your setup is impressive regardless of the specific dyno.

That is pretty cool, I had long wondered about running a rootsish blower like that, and the m.net crowd wont have anything but coldsides and dual tb set ups. So I am glad my idea that other people had done a million times before probably would work on a miata. I don't think you would have to worry about the air surging back to the rotor blades because of the blowoff. Super neat, and makes perfect sense.

https://www.miataturbo.net/attachmen...ine=1311098324


the bypass does close stopping more air from coming in but it does not closed enough, you could adjust the bypass to close more but then you would have the throttle lag and rev bog you are trying to get rid of by running a stock tb and bov.

and even after that when you bypass closes there is still positive presser in the cooler and tubing that would back flow past the screws.


on a side note i still doubt a double tb works as well as the m.net noobs think.

Oh, no doubt. I knew that, the son of a bitch stays spinning all the time. I guess the i was thinking of it is that it kind of deadens the blow. You would never completely eliminate the surge. Besides, if the throttle body stayed closed, there would be vacuum, then the boost built would still activate the valve, and still vent some pressure.

I think the real reason for the bov is so that your not boosting at idle or closing the tb under boost and having all the air slamming the butterfly. Yes you could run it with no bov and just the bypass and i did for a hour of testing but with high boost i think it would start braking stuff.


I also think that with no tb on the blower that the bypass does not work the same. It's on the list for me to test. If i could find a cut away or design image of a mp62 i would be very happy.

I agree. I think the BOV makes it last longer. One of my local buddies has an M45 hotside because he said he didn't want to tweak it. We are now making 170 whp and looking at something like this. If we could see equivalent gains I am sure that a shitty bov I have laying around would make a world of difference.

Jeff - I am joining the conversation late, and there are questions I am sure have been answered in a prior thread, so forgive me for any redundancy.

What exactly is your arrangement? I am surmising you have a positive displacement compressor blowing through a throttle body in the stock location and using a vacuum actuated valve to control/vent excess pressure on the high side when not in boost.

Is this correct?

Just for info, the Rotrex [centrifugal] setup all operate that way; with a vacuum operated by-pass valve to relieve the high side excess pressure back to the low side when not in boost.

I am on a quest to understand why I can not configure a positive displacement setup the same way.

What you call a "real dyno" is something I call a "cheap heap of shit" dyno. Mustang is the "real" dyno.

https://www.miataturbo.net/showpost....53&postcount=9

To bad the world doesn't run on mustang dyno numbers but i agree

Isn't there additional noise when running the TB in the stock location?

The only reason Eaton designed there twin screws they way they did was to cut the noise way down for oem usage.

So after you made your modifications, did you see the boost go up slightly? (on the red dyno curve, indicating an improvement in supercharger VE)

Did you by chance, run a datalog while at the dyno? It would be interesting to see a view showing boost, and fuel pulse width during the run. Before and after, would be even better...

Same 180 kpa (10.8psi) and graphs are almost the same curves. It all has to do with air flow efficient. You can't show the differences in throttle response which was the biggest gain.

I brought that idea up few years ago, i got my head chopped off.. The entire thing basically was whats the flow of the blower at 7k while decelerating.

No one could give me any info or help, a lot of no wont work and bs. I said fuck it i'm going it.

As i said the flow isnt a big deal. Hell even toss 2 tials if its such a big deal.. nope no one wanted to hear it.