Kian

Where have you put you valves on n/a cars that you have boosted?

Iowa999

iTrader: (1)

If that was to me, I have never added forced induction to any car. But if I were to do so, I would probably keep the original layout. Since almost all modern cars are MAF-based to start with, I'd stick with a suck-through layout and, therefore, recirculate after the MAF. The only thing you have to watch out for when you do it this way is something called "MAF overrun." All MAFs have a maximum measurable airflow. If you exceed this, the value produced by the MAF starts being wildly inaccurate and almost always too low. This will make you run lean at WOT and bye-bye engine.

The main alternative is to switch to speed-density, instead of a MAF. Ever see a drag car with an open curvy-funnel-like horn on the turbo inlet and no blow-through MAF at any point later? Well, it's 99% definite that the car is running speed-density, instead. You need an accurate measure of MAP and a good understanding of the volumetric efficiency of the motor to take this route. With this information, plus RPM etc, of course, you can calculate how much air is being ingested and set the injector pulse-widths accordingly. The huge advantages to speed-density are (a) it is based on what is happening right now, as opposed to what is happening several feet back up the intake path, and (b) it doesn't require a MAF, which is an intake restriction in most cases. But you really have to know what you're doing to run speed-density. Not for the faint of heart of those just messing around.

dastallion951

try it vta with the blow off valve how you have it, if the driveability becomes too compromised, fabricate a metal intake pipe with a bung off it that you can hook up a hose to it post maf sensor, and recirc the bov. Now since its a turbod silverado your saying, im assuming its on a full standalone correct?? if so then depending on brand you can fine tune it with the standalone to where vta might not even become an issue.

MrDgaf

No BOV should be placed "inline" before the MAF. NEVER.

dastallion951

mr dgaf nobody posted it should be done before the maf...

Kian

i was asking if it was better before the maf. this is because a know-it-all was telling me that that route was better.

the silverado uses a reflash similar to ecuflash, but much more powerful. gms take tunes very well. for those unfamiliar with gm tuning, its pretty cool. at any rate....its a turbo 5.3. we put the bov after the IC in front of the throttle body. Mr chevy himself comes around explaining that this setup will make much more power with the bov before the maf. i disagreed, but i wasnt sure due to my experience being mostly with recirc valves (evo,scoob,bmw,audi...etc) the truck isnt speed density tuned yet, its a mail order flash.

in a newly boosted system, wheres the best spot and why has been the question ive posted like five times. also recirc is out of the question in this application, so im not being rude, but stop bringing it up.

Iowa999

iTrader: (1)

To be blunt, I think that we've established that said "know-it-all" is a pinhead.


That's cool. You can keep the MAF, vent to atmosphere, and deal with the moment of richness, or you can use a speed-density (stand-alone) and have some real options. I can't handle speed-density myself - I'd say I stop at the level of DSMLink - so I'll bow out now. Good luck.

Kian

http://performancetrucks.net/forums/....php?p=4711937

the blue truck is the one in question

http://www.dsmtalk.com/forums/showthread.php?t=207821

the question that it isnt a good location has been answered, im trying to get the why.

Kian

actually, the more i read. the more im seeing pre maf bovs. this is on mostly american cars, but ford uses an 8 cyl dohc setup similar to a 4 cyl dohc setup. still no explanations though other than its not wise to purge metered air.

iowa, dont bow out yet

Iowa999

iTrader: (1)

Oh, I'm still lurking.

That makes no sense at all. Yes, of course you don't want to dump air that has already been measured, but if you put it back in before the MAF, then it will be measured twice. Can you post a link or two for us to look at?

Edit: at least one of those links above is to a car with a blow-thru MAF. In that case, you do want to dump the air before the MAF since you don't want to measure air that won't end up in the engine. Maybe this is the key to the confusion. You have to be clear as to whether we're talking about a pre-turbo, suck-through MAF (as on an Evo, DSM, etc) or a blown-through, post-turbo (or supercharger) MAF.

Kian

yup, thats the key. ol' boys a moron. so most fuel injected cars are suck, right? i cant even think of a car ive seen thats blow.

Iowa999

iTrader: (1)

Cars that came as forced-induction almost always have suck-through MAFs, but some kits for adding a turbo or supercharger to a NA car switch it being a blow-through. In the case of an after-market, blow-through set-up, you have a real, honest-to-goodness blow-off value right before the MAF or a recirculation value that returns to right before the turbo to aid with re-spool-up. In either of the cases, because it's a blow-through, any and all valves on the intake are before the MAF. The MAF is the last thing before the throttle body. I believe that it's done this way in order to do the metering as close to the intake as possible, so you are measuring what's being ingested right now, which makes sense (see some previous post).

Kian

im good. thanks for the help.

Iowa999

iTrader: (1)

You're very welcome. I enjoyed the discussion and thanks for letting me rant about the proper labels for the various valves on the intake. It's an old pet peeve that I've not gotten over; I literally cringe when I see "BOV" on a DSM- or Evo-related forum. cheers