Isnt a side effect of this location a possible boost spike/overboost? By the time location B sees 12 psi, there may be 16psi at point A on its way allready. (making up numbers here)... That was my rationalization for going with the compressor outlet location... I wanted to play it safe on the street so I opted for a slight performance loss in favor of more safety and simplicity.

I agree location B is probably best, just thought I'd mention this^

 

It makes all the sense in the world and excellent write up...!!

However boost spikes are really a possibility... Also the size of the IC is critical... it would be like the size of the straw, get a 2" hose and blow as hard as you can, and you will not feel resistance... Unless you are really good at blowing hahahahaha

I recently installed mine at the turbo nipple, and have seen steady boost, but I admit not going all the way to redline yet... Will do a run, as soon as I can, and will share!

miatex

 

The reason the straw was use is because we have to downsize our example since our mouths, even though we're all Miata driving gays, are not as powerful as even the smallest of turbos.

My only issue with this idea is that I use the amount of boost drop off as an indicator as to how much my bolts have stretched, and therefore how much exhaust is leaking out between my turbo/manifold. The flanges need to be resurfaced, so it always sounds like there's a bit of a leak.

 

I understand, yet the I dea I was trying to portray was the fact that the IC flow capacity will play a major factor... High flow IC, and you may not notice such droop... tiny IC and the setup is absolutely necessary...

I will see how my setup resist the current 13psi target... thanks for the clarification tho.

miatex

 

I don't see any evidence of my boost dropping at high rpm's. Admittedly, I tuned the gain on my Profec to maintain 12 psi to redline. In this scenario, is there any benefit to moving the signal source on the cold side of the IC?

C

 

If point C is such a bad thing, why does the MSM take its source at point C?
I believe the folks from FM also advice to use point C.

 

Fantastic write up Joe, my crusty ebay MBC actually recomends making a point b.

 

The article makes a lot of sense to me - but I'm a musician, what the heck do I know? I wonder what comments Corky might have since his systems (and mine) seem to use point A?

 

What happens when your wastegate and MBC does this:

 

You make moar power?

 

well played sir.

 

^Very true this was the setup that came on my old 323 gtx engine that was from '93. How is it that Mazda went to poorer designed systems on the newer cars? Less rallying and more Ford influence?

 

Def an excellent post by Joe, as usual, but I feel like it should also address boost/power loss do to inadequate spring pressure on the Internal/External wastegate. From my exp and reading its generally not recommended to run boost pressures more than 1.5x your WG spring, regardless of boost control method. It will not cause your boost to drop off as much as it will cause you to spool much slower than you could if you have a more adequate spring for the boost you are running.

Further, I would say that 1.5x might even be too much when running an IWG with a small/crappy internal diaphragm. Say you are running 15psi. I would put my money down that you would see an increase in spool running a 15psi IWG vs a 10psi IWG. EWG can get away with more because they have much larger diaphragms and often run dual springs.

 

Great information.

 

Any pictures of how to actually run the lines for this and labeled components? Seeing it would really help me, at least.

 

Excellent exposition, Joe

Thanx a lot.
Ben.

 

The MSM, takes it from point B. It has a port on the side of the tube that attaches to the throttle body, from that port it goes to the boost control solenoid on the valve cover and onto then to the WG.

 

I have always used the port on the backside of my IM. It is the 1/4" port that the automatic transmission refrences the vacuum. That port is perfect. No boost spike. Smooth to 12# all day long no matter the rpm on my 1.8

 

that port is turbulent as hell when your MAP sensor is sourced off it.

 

Yes it would be rock steady, but what is your turbo doing at engine loaded part-throttle cruise (uphill at 70mph on the highway)? To make 12psi in the manifold behind a partially closed throttle plate you might be making 30+psi at the compressor and huge amounts of excess heat for your intercooler to fight with. Plus you are restricting the airflow by forcing the turbine to fight the excess pressure that the compressor is seeing. I bet the turbine gets pretty hot at a cruise compared to one referenced at "point B". You should try switching it for a tankful and see if your mileage improves.