Does the CX-7 run a MAF?

[Steiner]

Like the title says, does the CX-7 ECU use a mass air flow sensor? If so I'm wondering how the hec and why the hec people are even considering a VTA blow off valve.

[spike blue]

good question!!!

[terbow]

Maf

[1Sleepy93]

Yes it runs a MAF. I don't plan on running VTA ever.

[Steiner]

Thanks for the info guys. There goes my wife's dreams of pshhhhhh pshhhhh pshhhhhhh. LOL.

[CX7TT]

it runs on MAF, but I am VTA my HKS BOV, no problem, its been closed to a month now!

[xavier]

it runs on MAF, but I am VTA my HKS BOV, no problem, its been closed to a month now!
Do you have any other mods? or do you just have a cold air and blow off? also, does the cold air intake relocate the MAF?

[hectik1]

CX7 has a MAF.

VTA can work with the HKS or the Greddy BOV. These don't leak vacuum due to their design.

Other BOVs may not work. Leaking vacuum will cause hesistation due to increased rich conditions.

For Steiner, if your wife wants that sound either A. remove the silencer in the airbox or B. get an intake.

[9Hooker]

VTA is a BAD idea in MAF systems.

The air goes by the MAF, thus metering the amount of fuel to add to that gives air. When the BOV activates, it releases air that has already been metered and fuel is dumped in with the system thinking that air is still in the intake tract somewhere. Even though it will run EXTREMELY rich for a very small amount of time it's still not good.

[Unit 91]

VTA is a BAD idea in MAF systems.

The air goes by the MAF, thus metering the amount of fuel to add to that gives air. When the BOV activates, it releases air that has already been metered and fuel is dumped in with the system thinking that air is still in the intake tract somewhere. Even though it will run EXTREMELY rich for a very small amount of time it's still not good.

Total facts. You can do it, but it's not the right way.

[Silver Ecstasy]

What's VTA? Sorry for the ignorance. I'm trying to absorb as much info as possible.

[terbow]

VTA is an acronym for vent to atmosphere (ie. instead of recirculating the air back into the intake, it vents it off)

[Silver Ecstasy]

So it's not a good idea to run aftermarket BOV's?

[1Sleepy93]

No one said it wasn't a good idea, just not the best to run them VTA. If you run them in recirc it's all good.

[9Hooker]

exactly. with MAF (mass airflow) systems, since the air is metered, it has to go in the motor at some time because the computer has scheduled fuel to go with that particular body of air. you can run an aftermarket blow off valve, only the "blow off" has to be piped back into the system SOMEWHERE after the MAF sensor and BEFORE the motor :)

hope that helps.

[Silver Ecstasy]

Eh, my newbness is coming out again.

A BOV is to release excess boost on off-throttle situations. The one that comes on the car OEM doesn't release excess pressure, it recirculates it?

The more info the better guys, again I apologize for not understanding.

Alls i'm understanding is, you wouldn't get the "whoosh" sound.

[9Hooker]

Eh, my newbness is coming out again.

A BOV is to release excess boost on off-throttle situations. The one that comes on the car OEM doesn't release excess pressure, it recirculates it?

The more info the better guys, again I apologize for not understanding.

Alls i'm understanding is, you wouldn't get the "whoosh" sound.

here's a rambling...

The BOV releases pressure at a point (yes, at abrupt off throttle excursions to prevent damage to the impeller by the resulting shock wave and keep the turbo spooled up for the same reason) AFTER it has been compressed, and in cars with a MAF, it recirculates it to a part of the intake that has yet to be compressed by the turbo.

so yes, in a MAF system, it has to be recirculated, in a MAP (manifold absolute pressure) system, it can be vented overboard, used to heat the coffee mug in the cabin, blown into your hair, whatever. It doesn't matter since fuel is metered by pressure in the manifold just before being shoved int he motor and not volume at some other point in the system. This is also the reason that fuel tuning a MAF car can yield nice results in an otherwise stock application. The stock computer doesn't take temperature or pressure (density) into account when metering fuel. It the air gets colder and more dense the MAF system doesn't compensate. It throws the same amount of fuel in @ 200 degrees manifold temperature that it does @ 100 degrees. Following PV=nRT and changing the temperature only, you are changing the amount of air molecules being shoved in the motor (the "n" in the equation). The MAF system is oblivious to this. It IS however the cheapest system to design and make fuel maps for. That being said... if you tune your car using some sort of fuel corrections in Tijuana @ 120 degrees ambient and you take the car to Montana where it's 27 degrees ambient you will run extremely lean. Reverse it and you will run rich. So in a MAF system, TUNE to your climate. If it changes, retune!


/rant

[Silver Ecstasy]

Meh, well Michigan weather changes everyday so I won't even bother with a daily driver.

But I guess my question lies, how do you recirculate the air off of the BOV? Like for example, someone installed the HKS BOV. It looked like it was out in the open, releasing pressure. How was that recirculating in the air system?

[9Hooker]

The discharge port of the BOV, where the blue ring is in the pic should have a rubber hose over it that attaches to the intake piping somewhere from the MAF sensor to the compressor wheel of the turbo.

http://us.st11.yimg.com/us.st.yimg.com/I/yhst-73960398774210_1914_285728

[Silver Ecstasy]

Hmm, I could be wrong, but I didn't see anything. I just seen the BOV attached to a flange of some sort and that was it..no re-routing of any hose to the intake. And where would you even install that on the intake?

(Also, has anyone tried installing a boost gauge on a CX yet, to see what exact boost numbers its getting?)

[9Hooker]

install it the same place the factory BOV goes...

look closely at the shiny end...rubber hose coming out....

(from a mazda 6)

http://www.cp-e.com/imgs/bov1_lg.jpg

[9Hooker]

http://en.wikipedia.org/wiki/Blowoff_valve

found this!

[Silver Ecstasy]

Ahh I see! I'm sorry if i've like totally pissed ya off tryin to help my ignorance. I still don't think that one guy with the CP-E intake and HKS bov has that setup. So where does that hose connect to? Do you have to custom make everything? Or is it all supplied in the purchase of a BOV?


I'm reading too that since the turbine is moved by exhaust flow, it adds as a little restriction to the engine exhaust flow. Is that why most turbo'd cars have huge 3"+ exhaust piping? Wouldn't doing that to the CX help out atleast? Or would it cause a richer setting in the ECU and mess things up.

[9Hooker]

I don't think anyone is pissed... I'm certainly not.

Normally you have to find your own tubing, lowes, home despot, auto zone can help there...

you can connect it anywhere you want really. just as long as it's before the turbocharger and after the MAF sensor. So what, like anywhere in that 9" of piping.

The worry is not in the restriction from the cylinder head to the compressor wheel. There is supposed to be pressure buildup and therefore a restriction in that area. That's where the turbine wheel is gaining energy to give to the impeller wheel.

Take for instance a jet engine. It's pretty much just a big turbo charger. ~75% of the entire energy package produced by combustion is used by turbine wheels to sustain the compression of incoming air. That's a LOT of energy used.

In a car there will be energy loss (therefore a restriction) at the turbine wheel. It happens, nothing you can do about it. I don't even think people measure this amount... What can be done is make sure the energy loss is at the face of the turbine wheel and not in the manifold... get it extrude honed!

(http://www.extrudehone.com/auto-oem.html)

After the turbo though, ideally, there should be no restriction. So to answer the question, yes, a 6+" exhaust will make more power, but at what point does the god awful droning become more of a nuisance than the 4 hp it creates over a 3" exhaust?

Personally I would look for ways to be more efficient just after the turbo and before the exhaust system. To me that means a nice downpipe that bolts to the factory exhaust.

I'd wager a guess that a good downpipe (from the turbo housing to the exhaust system) will make more power and keep noise under wraps better than the stock downpipe and 2324" exhaust piping.


/rant

[1Sleepy93]

A downpipe and exhaust should do wonders for our motors. It's tuned really rich when in boost, I've seen as low as 9:1 on dyno graphs for the DISI, so adding that in will help to lean it out a bit.

[Silver Ecstasy]

Cool okay I think i'm starting to come around a little better.

I read all those links and studied the way it works and went to howstuffworks.com and even studied that. I had no idea that that is how a turbo works. Didn't know all that was involved. It seems like such a complicated process as opposed to a supercharger.

Had no idea that a wastegate was different from a BOV and this and that. Goodness, thats alot to learn. Plus the different settings and stuff like that. I'd love to get my hands dirty and install a turbo setup though one time. I guess thats why they heat-wrap alot of turbo applications on the "hot" side of the system, that thing will generate so much heat from the exhaust gas. And this explains why the EGT's can be so important too. Monitoring that heat, I assume, can judge whether or not you're running rich or lean, and if its at a safe level.

I think what we need to do is get a Boost gauge installed in someone's CX-7 first, or see who has a laptop application.

For the record, I don't even have the car yet, and i'm already so psyched about being able to step into a whole new realm of car. I've been missing this type of feeling. Plus, I finally seen another CX on the road! Actually it was parked in the lot at the mall. Looked gorgeous! It was a GT black with chrome accent.

[9Hooker]

A downpipe and exhaust should do wonders for our motors. It's tuned really rich when in boost, I've seen as low as 9:1 on dyno graphs for the DISI, so adding that in will help to lean it out a bit.

No kidding... all motor I was running in the 13.6:1 area, and in mild turbo applications on non-forged stock internals would run ~12.9:1, 9:1 is retarded. Like couldn't get into the Special Olympics retarded. Safe for the lay-person that could very well put 87 octane in regularly (not a function of A/F ratio I know, but that TYPE of person), but ugh...



As for the heat wrap, that's also to keep the energy IN the system heat = energy = good in the turbine side. heat is a killer on the other end. EGT is a good simple gauge of A/F ratio if you don't want to spend the UBER $$ on a wideband O2 system (so simple that even civilian aircraft use EGT to tune the fuel mixture at cruising altitudes)

If EGT rises rises rises as you pull fuel then starts to go down when you continue to pull more fuel you have just found the optimal A/F ratio. Then just add 50 degrees or so on the rich side and VIOLA, safe AND efficient.

[Silver Ecstasy]

Theres like no where to neatly put gauges on the CX..hmm..Unless you did digital gauges, or did a CarPC with gauges running.

[1Sleepy93]

Glove box or under the radio console.