Blow Off Valve Modification

[Ford_Power]

MS700, you said that your tuner told u that changing the BOV will only result in "a little puff black smoke after gear changes or when the manifold is in vacuum, because the computer thinks that there is still x amount of air in the intake and will inject the correct amount of fuel mixture. But all the air wont be there (because it was exhausted by the bov) so it will richen up."

What I think you are missing here is that there is a basic problem. The engine computer thinks there is X amount of air going into the engine as the MAP/MAF sensor reports a certain value (lets say 5), yet the HEGO will be seeing a rich mixture that would moreso be indicative of a value of 7. Thus the computer is going to be seeing two non-concurring signals. The result? A computer controlled detune and ultimately less power.

Oh yeh, you were right in saying that the A/F ratio will remain unchanged under cruise and accel.

l8r

Ross

[Guest IMTRBO]

I agree with you guys but on a different matter any1 know where would be the best place to insert a psi sensor so it can activate my 15 dollar window washer kit that will be mount infront of the cooler with some gardina mist nozels

[ms700]

ford power u are correct in that sense. all of my experience in tuning cars (including my own xc) with haltech and ems etc didnt include the use of a hego sensor in the exhaust permanently. I kinda forgot about that sensor reading what would be exiting the manifold. the computer would continuously trying to alter the mixtures, one minute it is spot on, then a gearchange or lift off the accel, and its all over the place, and next minute is it spot on. back to the books for me.

lets get 1 thing straight. if ondole wants to run his bov to the atmo, or another aftermarket bov, let him do it. its all about being individual and stepping outside the square. if nobody thought differently, we would have a very boring world!!!!

look at street tuner for example. being different, being adventurous, and bam! 300kw!

[ms700]

correct me if im wrong (and I know youse will), but if the xr6t runs a map sensor (manifold absolute pressure), it shouldn't make a difference, because the car only reads the amount of air in the manifold itself (after the throttle body). as opposed to maf (mass air flow) sensor which reads all the air entering the motor from the airbox onwards (before the throttle body).

does anybody know what the xr6t uses? maybe the xr6t uses both sensors? I cant see any sort of maf sensor. but I am pretty sure I have seen map sensors on previous falcons.

can anyone shed some light?

[Ford_Power]

Irrespective of whether a MAP or MAF is being used, the computer has discrete maps in it for references to fuelling and timing with relation to air density or air mass. As I stated in my earlier post there will be conflicting signals from the MAP/MAF and HEGO.

Now I cant be sure on this, but one would expect the computer to register a fault code when the sensors report a set of sequential values that are "impossible" to acheive (given the maps) with the stock engine/BOV configuration.

eg. one second stoich, next EXCESSIVELY rich, next stoich, etc etc.

Ross

[NT TURBO]

I'm no turbo mechanic, buuut if you've revved it and are backing off, (hence BOV opreration) releasing some of this pressure between turbo and throttle body keeps the turbo spinning (the whole idea to save lag) if it vents to atmosphere it will draw in more air(cause we've kept it spinning) which will compensate somewhat for what is missing from not having the return. Either way for the BOV to operate means there is excess pressure when the throttle is closed anyway, I believe manifold vacuum will remain fairly similar regardless of atmo venting or returning

[Turbo6man]

ms700> I don't remember you saying you were going to do the mod either - who ever suggested you were? I'm sure there is no cause for your sorrow.

I agree wholeheartedly with the sentiments you express regarding sharing of information in the forums and the purpose of the forums.

In this regard it would help sometimes if people would read the posts correctly and in their entirity before offering up an opinion that is incorrectly supposed.

PS ... Again, I'm not suggesting that YOU are in that category so don't lose any sleep over it OK?

[ms700]

I never "lose" any sleep, im up all night driving my cars and working on em!!!!

Question time peoples.

if any car with a ecu (aftermarket or oem), doesn't have a maf, how does the ecu know how much air is in the intake pipes (including the turbo/supercharger)? and how much air is in the intake system before the throttle body?

if my stupid theory is correct (probably not!), making a bov vent to the atmo on cars without maf's shouldnt affect tuning drastically, because the ecu hasnt accounted for the air in the intake system before the throttle body. the ecu simply doesnt know how much air is in there. unless there is another sensor somewhere?

venting all my bovs to the atmosphere didnt affect my tuning 1 iota. but I deal mainly with centrifugal superchargers. maybe turbo's are different because blowers are always boosting?

someone shed light pls!!!!

[ZLAKLR]

so does the XR6T run MAF or MAP sensor? if it runs a MAP only then a/f ratios on throttle lift off wont be effected at all. In all my experience with imports, the ones that run a MAP sensor dont have isses with idle etc with atmo venting BOVs, those that run a MAF do have issues.

With MAP, the air as mentioned above is only measured once its in the plenum, if its not measured befor its vented, then tere wont be a problem.

So, what does the 6T use?

I am curretly looking for an XR6T (just missed out on a Manual black one today with 19s) and this will be something I do while we are fitting a larger front mount IC.

[Ralph Wiggum]

dont forget that the design of the ford bov means that when ever the car isnt on boost the bov acts as a bypass valve to improve fuel economy at cruise due to reduced exhaust back pressure(because the turbine can spin more freely),and to allow reduced spool up time by bypassing area around the compressor during spool up.. that this also means the the "atmo" side of the bov is open to atomsphere on cruise and able to suck contaminants into the eng. if you what to do it for sound buy a smaller k and n (or similar) breather filter and put that on there....