MP 90 FWD Project Updates

[AleroB888]

Those headers were made by "The Other Guys," (TOG), a company which is now out of business. I got a second set of TOG's in fair-to-good condition on ebay for under $500.00 a couple years ago.

[AleroB888]

painted the steel mount hardware (except half-round tubes, which are an extra set; ones in use now are stainless)





test setup w/ new type stock MAF sensor, BOV/bypass pipe in place.

[AleroB888]

BOV/Bypass, throttle side

[AleroB888]

Almost ready to see if we can generate a little safe boost with a crude prototype

[AleroB888]

Completed 2 test drives..... after shortening the cable linkage it finally got 2-3 psi boost. That's almost what was expected for using a rain cap as a valve..... no attempt was made to improve the seal at the mating surfaces. Plus the boost pressure has some leverage to force it open.
But nothing terrible happened on the tests, so now I'll try to come up with a non-leaky valve

Ha, just remembered I forgot to reflash the PCM for the stock MAF

[Guest]

Why wouldn't you just use an of the shelf blow off valve?

[AleroB888]

Why wouldn't you just use an of the shelf blow off valve?

I need it to flow more air and activate more quickly than those I've seen on the market. Something like a wastegate that operates only to dissipate virtually all the boost at the instant the throttle closes. And it must only be possible for it to fail in open position, or the result could be disasterous. There are a lot of design problems and theories to play around with here.

[Guest]

I think if 2000+ HP supercharged v8 cars can use off the shelf blow off valves, your less than 500 HP (don't know what your target power is) can use an off the shelf blow off valve just fine, with far less head ache and much higher reliability.

Don't get me wrong, I'm all for building new versions of things, when it makes sense, making a BOV that will likely not work as well as an off the shelf unit does not make sense to me.

[AleroB888]

I think if 2000+ HP supercharged v8 cars can use off the shelf blow off valves, your less than 500 HP (don't know what your target power is) can use an off the shelf blow off valve just fine, with far less head ache and much higher reliability.

Don't get me wrong, I'm all for building new versions of things, when it makes sense, making a BOV that will likely not work as well as an off the shelf unit does not make sense to me.

Which V8 blow-through application do you mean? Centrifugal type? Those allow some backflow. If it uses a Roots or twin screw blower I'd like to see it.

[Guest]

Are you really suggesting that a large off the shelf BOV (or two) will not function as designed and somehow not work as well as what ever you're making here? I really don't see how that flapper you have is going to open quicker or flow more or seal any better than any off the shelf BOV designed for a similar or same application.

The type of blower will not make a difference here, and no, centrifugal blowers (nor turbos) really allow for any "backflow" as you suggest. It is a reversed pressure wave that damages the compressor wheels on the centrifugal blowers and turbo compressors.

Do what you want, but I can guarantee you that an off the shelf BOV that is sized appropriately for the application will work just fine.

[AleroB888]

Are you really suggesting that a large off the shelf BOV (or two) will not function as designed and somehow not work as well as what ever you're making here? I really don't see how that flapper you have is going to open quicker or flow more or seal any better than any off the shelf BOV designed for a similar or same application.

The type of blower will not make a difference here, and no, centrifugal blowers (nor turbos) really allow for any "backflow" as you suggest. It is a reversed pressure wave that damages the compressor wheels on the centrifugal blowers and turbo compressors.

Do what you want, but I can guarantee you that an off the shelf BOV that is sized appropriately for the application will work just fine.

First of all, what I am using here now is a preliminary test setup. It's not even a valve, it's a rain cap, not designed to seal. I may try to modify it to seal better, but I want to design a valve with a more compact activator mechanism.

Yes, it does open quicker than a vacuum operated BOV would. I have considered modifying an off-the-shelf BOV or even a wastegate to operate with a mechanical linkage. I already have a throttle body butterfly valve that I may also test. But the first step was getting the actuator linkage to work, and it appears to. Actually, it needs to be anchored to the charge piping, not the chassis, because engine movement affects it.

As I stated before, this is only a crude prototype.

[AleroB888]

Test 2

I used a throttle body as the BOV (or bypass, or recirculating valve). This one is only 58mm, not 65mm like I think it needs. And it should be mounted closer to the charge tubing.

Got in 3 test runs, blew out 3 different silicone couplers. lol
Made it to 10 psi on the last one. Acceleration from standing start was good, so the method seems to have potential. But abrupt deceleration has yet to be tested.

[AleroB888]

I tightened up the connections and made another test run, and the device appears to work. Floored it from 25 mph, spun the tires and it pulled nicely up to about 60 mph. The charge pipes shifted around some, and then I had to trim the actuator lever on the "BOV."

The throttle response is different than the standard non-intercooled setup was. Sort of like a mechanical secondary on a 4-barrel carb. Since the two throttle plates tip in at different rates, It required a progressive linkage where the primary TB opens about 15 degrees before the secondary TB (BOV) starts to close. That's an adjustment that mainly affects part throttle response. But BOV opens instantly when you lift your foot, with the help of a return spring.

I have to admit, this is the scared-est I've been to drive this thing.

[AleroB888]

Test setup 3

Took a 10-mile cruise and peaked at 12 psi, which is pretty good considering the restrictive warm-air intake tract. But I did have some debris from the blower make it through the intercooler to the MAF screen, and a trace of PCV vapor oil in the intercooler pipes.....(I'll deal with the PCV later, right now it is fed to the blower inlet.)

I put a screen in the pipe from blower to intercooler, and revised the BOV actuator as a self-contained unit.



Then, to make sure outside air is not pulled back thru the BOV under vacuum conditions, I cut up half-inch squares of paper, put them in the BOV outlet, and a screen over that to keep them in. I drove around the block at low rpm, and the paper stayed on the screen, indicating a constant outward airflow.

I haven't had much time for test driving, but it's not fun in this heat anyway. On the WOT runs that I did make, the temp. increase post-intercooler stayed below 20 degrees, even with no water lines hooked up on the intercooler yet. Normally, I'd see a 50-70 degree increase during 0-60 mph runs in this heat.

The blower noise, though, is going to be a huge challenge. It's loud, obnoxious, and almost constant.

[Xnke]

I run a similar setup on my Datsun...And Raven, NO a standard blowoff valve will NOT work with a positive displacement supercharger. They really can't move enough air. I had mine taco the throttle plate a few times trying to use one.

The current setup on my Z is a Q45 throttle body on the inlet of the M90 super, A/A intercooler across the front of the core support, Ford 65mm Crown Vic throttle on the inlet to the intake manifold, and into the engine. I had to make a custom throttle roller that had two different diameter pulleys on it to synchronize the throttle openings. This solved my throttle damage and blowoff issues, along with adding quite a lot of drivability to the system.

Using just the throttle on the inlet of the supercharger, I had idle problems due to the very large throttled volume. Using a throttle on the intake manifold and trying to blow through it, I damaged throttle plates on a regular basis, even with two 1" blowoff valves, then again, with two 1.6" blowoff valves, then with the two 1.6" valves plus the internal bypass valve in the supercharger.

Using both throttle plates also cuts down a LOT on the highway cruise noise.

The best solution I have arrived at so far is the following:

Ford Airbox->Ford 70mm MAF->Q45 throttle->M90 supercharger->Big Frontmount intercooler->Ford 65mm throttle->Intake plenum

Of course, I'm running a 2.8L inline six and Megasquirt, the MAF is for flow monitoring only and has no engine control. With supercharger and head porting and some serious supercharger case reconfiguration, I am seeing 520CFM inlet flow at only 5.5lbs of boost. IAT's are about 110F at full boost in 80* heat. It scoots.