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Discussion Starter #1
Hi guys. Steve @ IMS just uploaded some late night pics for me. They're for my mandrel bent intercooler hard pipe kit for the Mk2 Supra. I also posted on the turbo section. Sorry for the soliciting! The link is http://www.rabidchimp.com/aaron/ Catch you all later.
-Aaron
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Discussion Starter #4
Hi Andrew. Yes, thats the Greddy Type S blow off valve, which is included in my turbo kit.
-Aaron
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Aaron,
Is it loud? I want everyone to know I have boost.. 8)

-Andrew
 

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Discussion Starter #6
The blow off valve is loud, but is recirculated back into the intake tract. This way, when you let off boost and are coming to a stop in neutral, etc, the car won't die. Air flow meter cars don't like blow off valves that vent to atmosphere.
-Aaron
 

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How about with the AFM to MAF conversion? Would it be possible to vent to the atmosphere?

-Andrew
 

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Both afm and maf measure air as it comes through the meter, so both will need the bov routed back into the pipe behind it. Only map systems should be vented into atmo.

Christian
 

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Racefiend said:
Both afm and maf measure air as it comes through the meter, so both will need the bov routed back into the pipe behind it. Only map systems should be vented into atmo.

Christian
Umm.. I'm not exactly sure that that is correct. Being as the ECU is not able to understand that the intake trac is under positive pressure instead of vaccuum, the ecu doesn't expect the extra air to be there... which if thats true, should mean that venting to the atmosphere will be ok...

...or at least, thats what I am hoping :)
 

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Actually, think of a system without bov. when the throttle plate is closed, the compressor stops, therefore no air is being sucked in through the afm/maf. No(very little) air is going into the engine, so fuel is close to what it should be.

Now put a BOV on. the bov vents the air out from behind turbo, so the compressor wheel is still spinning, still sucking in air from in front of the turbo. If the bov is not routed in front of the turbo, that air will have to come through afm/maf. The afm/maf will register air flow (therfore the ecu thinks there's air) and put in fuel, but the engine is not sucking much air in. There is your overly rich mixture. A BOV routed before the turbo essentially acts as a closed recirculation system, where the outlet of the turbo is going back into the inlet, independent of the TB and afm/maf (to an extent). Not much air into engine, not much air going through afm/maf. Close to correct fueling.

HTH

Christian
 

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You can also think of it this way; the ecu expects to utilize whatever volume of air passes that maf . The fact that it's squished further down the line to fit within the cylinder makes little difference, and if that metered air is lost w/o some way of telling the ecu it's gone, you briefly run really rich.

It's like a sudden temporary vacuum leak.
 

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Discussion Starter #12
Moorman wrote
"You can also think of it this way; the ecu expects to utilize whatever volume of air passes that maf . The fact that it's squished further down the line to fit within the cylinderr makes little difference, and if that metered air is lost w/o some way of telling the ecu it's gone, you briefly run really rich.

It's like a sudden temporary vacuum leak"
While not in boost, a vacuum leak would cause a lean condition. In vacuum, the engine "therotetically is "pulling" air in. A vac leak, would bring unmetered air into system.

On the other hand, a boost leak, would result in the ECU seeing X amount of air in the system, for which is would supply X amount of fuel. If this metered air never makes it into the combustion chamber, there would be too much fuel in the mixture.
Cya!
-Aaron
 
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