It's been a while since I have been on here. I am picking up on my brothers fc3s 87 TII build. the Inter cooler is mounted and the last few things needed to fire her up are finishing the IC piping, mounting the MAF, a brake line, coolant line, and a few vacuum hoses. Sounds like a lot but most of it is just bolt in.

Back ground- 60-1 turbo installed, almost all of FC3S pro mods done. FMIC installed. running Rtek 2.0 ecu

Here is where my questions come in.

Looking around this site and online, It looks like a lot of people have installed there BOV on the IC pipe headed up to the Throttle body. Would It be better to mount the intake between the Turbo and Intercooler? So that vented air hasn't already been through the Intercooler. or is it better to vent it after the IC so that the pressure doesn't have to surge through the IC again.

Second. Where are people putting there MAF? I see a lot of FC's without them. Do the other ECU run with out them?

Third. Is it a good idea or bad idea, to mount the MAF in-line between the Intercooler and the Throttle body? If the BOV is before the Intercooler and the MAF after. air would be dumped before it goes through the Intercooler( slow heat soak on the IC) and with the MAF in-line it will read the right temp and air flow from what the turbo is pushing.

please jump in with any info on this. I seem to be going to opposite way from what people are doing. Maybe a good thing may get flamed for this. Please fill me in on any info or pics to help.

Thank you all for your time.

 

Most people you see without MAF sensors are running a standalone that uses a MAP sensor instead.

 

It is best to mount the BOV in a high-pressure, low-velocity area, such as right after the compressor outlet or right before the throttle body. Either position is fine, but the main difference is that mounting it near the compressor will reduce the amount of plumbing if you are recirculating the air back to the AFM inlet in order to keep the engine in tune, while mounting it near the throttle body will reduce the amount of vacuum tubing.

As explained above by The CzAR, some people put the AFM (MAF) on Ebay and run the engine with a standalone EMS. The advantage of this is that a well-tuned standalone EMS will offer superior performance and gas mileage, while the disadvantages include higher cost, complexity of the installation and tuning, and the retuning required whenever performance parts are added/removed or when the engine starts to wear and become less efficient.

That is something better answered by contacting Rtek or posting in our Rtek forum.

 

As close to the turbo as you can get it, a BOV releaves the pressure built up in the charge piping so that said pressure does not "surge" (back spin) your turbo. So the closer it is to the turbo the less chance it has of this happening. Because when the TB butterfly closes the pressure has nowhere to go except backwards. Well thats the theroy behind it all anyhow lol.

As a fun side note, the closer it is the the turbo the louder it'll be heehee.

On the subject of running your MAF inline (also known as a blow through MAF), the only RX7 MAF that I know of that can do that is the 89-92 N/A plunger type. And if anyone is going to run it that way you have to reroute the BOV into the charge piping right before the MAF so that the backpressure does not slam the MAF closed when you let off of the throttle.

 

OK Thank you for the input. I Think ill just try and cram the MAF in-front of the turbo inlet somewhere. maybe under the Intercooler piping if it will fit.

Whats the closest you can put the MAF to the turbo. I read somewhere that there is a minimum amount of space you want between the MAF and plenum/turbo depending on the car. I know mitsu 3kgt's are a 12" minimum. We don't have the original rubber intake to base it off of.

I Think ill just weld the BOV flange right to the tubing after the turbo outlet. I know i have under hood space there. It will just look a little bunched with the turbo, MAF, SSQV BOV all right there.

Also, on a side note. Has anyone else swapped to a oil only turbo? Did you cap the coolant feed lines for the turbo or did you find a way to connect the two?

 

A BOV mounted next to the throttle body will open faster.

The 1988 10th Anniversary Bonneville world record setting RX-7 had the AFM mounted after the turbo, as did some of the Japanese tuner cars of the era before the standalone EMS was offered to the masses. The AFM spring had to be recalibrated, and many separate 80's whiz boxes (fuel computer, boost computer, ignition computer, etc.) were required to tune the engine. It was a complicated and expensive ghetto method of running the engine when compared to today's electronics, but it did work. My only question is how well the Rtek would run the engine in that configuration.

Oops, I should have written recirculating the air back to the AFM outlet. The idea is to not vent the metered air, nor to re-meter the air, but rather to feed the engine the amount of air that has been metered. Sorry about that.

 

That would be a downgrade.

 

Mitsu Karmann vortex volume airflow sensors are a different design than the flapper volume airflow sensor used in the Rx-7 and other 80s cars. It's not a direct comparison. That being said, I think the conventional wisdom is that the airflow meter should be at least level and not any kind of funny angle.

if you look at a bunch of different OEM blowoff designs, they really vary. Some are before and some are after the intercooler. Just put it wherever is convenient.

I've got one. Water cooled is definitely better, but a lot of it depends how much mileage you plan to put on the thing. It saves money and complexity to go with an oil-only turbo. You will need to install a split air blockoff plate on the LIM to blockoff the oil feed. The oil return can be capped a few ways. If you just use a big vacuum cap it may eventually split from the heat and fail. The best way to plug it is to remove the water pump housing and get it physically welded shut (it is aluminum though so you can't easily use MIG). The other option is to use JB weld with the housing off the car. But you will want a CRAPLOAD of JB weld for it to hold. So put a bunch of JB weld in, let it sink down in there and set overnight. Then do another round of JB weld and let it set.

You could also crimp the nipple shut and weld the end, or you could tap it for a bolt.

 

did you mean to block off the coolent line and not oil on the LIM? The turbo is a 60-1 oil cooled/lubed. I just want to make sure Im not backing up the coolent system there. and pulling and welding isn't an issue.

If anyone needs to do aluminum without Tig or a Mig setup. Go for the high heat torches/Oxy acetlyn and alumaloy. Its a brazing rod that fuzes to almost all types of aluminum. I fell in love with this stuff years ago.

 

be smart and mount it between the turbo and the intercooler.