move maf next to TB?

[tyrannix]

i heard something interesting from somebody... he used to run alot of hondas... but is currently working on an rb26 project

moving the mafs ... to right before the throttle body ...

now, for my perticular application, i am using an apexi PowerFC .., so the stock computer is out

he said it works better becuase its a truer (is that a word) reading, the air is the temp and density that it enters the cylinder at.... instead of pre-compressor

it sounds feasable to me... anyone try this before (or seen it done?)

[iliketocrash]

i'm pretty sure that won't work. something about putting the maf directly before the throttle body f's up the readings. too much turbulance due to air bouncing around inside the intake mani when the intake valves shut and such. i'im sure there is someone here who can elaborate a little better if not just tell me i'm wrong. but generally if you don't like the maf setup then you cross over to standalone and usually you move to using a map sensor and such. lol, i know i'm being a little vague and general but i'm trying to be helpful... really...

[tyrannix]

ive heard that you dont need a map sensor swap until you get stupid high power, like an 800whp supra

but i am using a standalone (uses normal sensors tho... by definition, is a powerfc a standalone? boost_boy says no ), so at what point in the flow scheme does the map sensor go ?

and its not that i dont like mafs... i just want to find a new trick if possible.. if something simple, like moving a sensor will get more power, or make any kind of improvment... why not do it? (if it works, of course)

edit> and by 'next to the TB' that could mean anywhere on the cold pipe .. between the IC and the TB.. .... so there will be less turbulence farther away from the TB.. theoretically it will give a better reading? maybe? im just throwing out ideas here waiting for somone to shoot them down, and say no.. that wont work because of XYZ.. or hey, yeah, that works because ABC

turbo theory... is this stuff covered in any of those turbo theory books anyone has? if so which book?

[btustison]

It is fairly common to install the MAFS in the cold pipe, it is just a pain to plumb, and the plastic ones (Z32, RB,etc) tend to crack with extended high boost abuse.

[Pumaking]

rule of thumb is the MAF has to be 12" before the TB b/c the fluctuation of the TB will cause strange readings

[float_6969]

rule of thumb is the MAF has to be 12" before the TB b/c the fluctuation of the TB will cause strange readings

You beat me to it. There are pro's and con's regarding a blow through setup.

Pro's-accurate reading's of the air entering the motor-any leaks before the MAFS won't cause the motor to run poorly

Con's-PCV system can cause oil buildup on the wire films and cause faulty readings-must be 12" from the TB or you will have problems with the reading fluctuating-harder to plumb in

[tyrannix]

so if you have a metal mafs (is the Q45 one metal?) and you plumb it below the battery box location on teh cold pipe, then it will all be gravy?

i really like the idea of more accurate air measurements

oil buildup shouldnt be a problem with it that far from teh TB, should it?

and since the air isnt metered yet, shouldnt that fix the temporary rich problem when the BOV releases pressure? (no more backfiring on shift)

edit> or if you were to coat the plastic mafs with epoxy or jb weld or something, that sould ease the stress, eh?

[iliketocrash]

the reinforcement idea with the epoxy or jb weld doesn't sound like that great of and idea to me but who knows. as for oil buildup, yes it is still a problem especially if you still of the pcv valve recirculated into the intake tract before the mafs. other than that there shouldn't be a problem with oil buildup unless your turbo leaks or something.

edit: and yes. this will allow you to vent your bov as long is it is before the mafs. and as for a metal mafs, i've never seen one. but then again there are a lot of cars i haven't seen under the hood as well.

[tyrannix]

maybe this gets into engine plumbing now (couldnt find anything in the FSM)

but the valve covers, the intake one is piped into the plenum, and the exhaust side one is piped to the pcv coming from the block?

if thats the case, how does the oil get cycled back to the cams? (i always thought the hoses going going to the valve covers were sending oil into the head)

it would be great to find some plumbing (vaccuum, ventilation, oil, coolant) diagrams

i think the coolant just (from the pump) hits that T pipe then splits to the back of the block, and the raditor... then the return from teh radiator... hmm.. i dont remember where that one goes bottom of the front of the block?

(im trying to go from memory when i stripped the engines to get them back to the US)

[float_6969]

1st, they make MAFS's specifically for a blow through setup that are made of metal for Mustangs. I don't know how you'd go about setting up an ECU to run one though.

PCV stands for Positive Crankcase Ventilation. What it does is remove excess pressure from inside the motor. As the motor runs, pressure passes by the rings, creating a positive pressure inside crankcase (and head). This isn't a big problem by itself. The problem is in what the gasses that are pressurizing the crankcase are composed of. They consist of a mix of water and corrosive chemicals left over from the combustion process. If they aren't vented out, they can break down the oil and cause rusting and corrosion inside the block. This is generally remedied by simply installing a one-way or check valve (called a PCV valve) in th intake manifold that allows these gasses and the pressure associated with them to be relieved and burned in the combustion chamber. The problem with that is that misted oil is often removed and collects in the intake manifold. This can be reduced by using a catch can. The problem is that the pressures are greater an it becomes much more complicated to use one when you start using forced induction.

You can still use a catch can with a forced induction car, but you have 2 choices as to how to make it work. The simplest is to use 2 catch cans. One between the intake valve cover and the PCV valve on the intake manifold, and then another between the exhaust valve cover and the suction pipe on the turbo.

The other way will require the use of a couple of "T"'s and another PCV/check valve. I made a writeup on how to do it somewhere in the archives. I'm at work right now, so I can't post the picture right now.

[tyrannix]

so, under normal conditions, the intake valve cover is venter into the plenum and teh exhaust cover is vented to right before or after the compressor with a pcv valve so it will let out the corrosive mix, but not when the boost is on?

does the block need any ventilation?

it would be great if a printed document *FSM :\* covered all of this... these are all things to know for engine reassembly

well, i have 1 catch can, so i should be good if i use a T fitting and vent both valve covers into the catch can, then into the plenum?

so , except for the oil, which the catch tank should take care of, i am liking the blow by setup

i should be good as far as oil residue goes if i mount the mafs on the FMIC output? shouldnt be any oil there anyway, should there? and it will have the colder, denser, more accurate reading and wont be affected by the BOV (right after the compressor, as normal)

[knightrider]

the exhaust side goes in the suction pipe before the turbo, you dont need any type of valve.

the block does need ventilation, thats what the pcv system is for.

the fsm does cover things like hose routing and such, it also covers how to diagnose problems in the systems.

the catch can doesnt account for oil leaking in the turbo if you have any, which is what most of the oil if any is in you intake system, imo a blow through system is not worth all of the headaches associated because your gain will probably only be minimal. imo its also better to recirc your bov for obvious reasons, along with helping the response of the engine while under vacume, helping build boost faster.