Plumb back BOV

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Plumb back BOV

Postby JDMGT4 » Sun Aug 15, 2004 12:01 am

Hi everyone,

I am planning to install a HKS SSQV BOV onto my 1990 ST185. But I was told that I shold install a "plumb back BOV" instead (this releases the excess pressure back into the intake, instead of into the atmosphere). Is there any difference in performance between the two types of BOVs. Are there any consequences I should prepare for if I install a BOV on a stock ST185?

Thanks for any information!
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Postby Gary » Sun Aug 15, 2004 2:03 am

If you reroute it back to the intake, you shouldn't have any problem.
If you vent it to atmosphere, you might be running rich (or even stall) everytime you hear that pshhhh...
BTW, BOV is more of a preventive mod than a performance mod.
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Postby RIalltrac » Sun Aug 15, 2004 2:04 am

I dont think the SSQV can be recirculated, I could be wrong though, I'm assuming thats what your refering to. Regardless... by venting to atmosphere you may run rich, which would cause your engine to stumble a bit. Some people have the problems, others dont, I guess you just have to find that sweet spot when your setting up the bov.
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Postby Gary » Sun Aug 15, 2004 2:08 am

Yup, they have a recirculation kit for the SSQV
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Postby toayoztan » Sun Aug 15, 2004 3:09 am

Okay, i was wondering why exactly it does make your car run richer? I mean, is it the AFM sensing the air released from the BOV from inside the Engine bay? Is there anyway to like um..."block/cover" the sensor or make a wall or whatever so the air being released by the BOV doesn't come into any contact with the sensor?

Thanks!
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Postby Gary » Sun Aug 15, 2004 3:18 am

AFM doesn't sense the air released from the BOV.

What happen is AFM measures amount of air entering the engine. It sends signal to the ECU. Then, the ECU feed the engine with the correspondence amount of fuel. If you vent the air out, you will have too much fuel (running rich) due to missing amount of air.

Unless you reroute the air back to the intake, you cannot correct the fuel amount. This is because you cannot measure amount of vented air.

There are 2 methods to fix this:
1) Reroute the air back to the system.
2) Convert to speed-density system (like the 3rd gen 3sgte from ST205)
HKS VPC, stand alone EMS, and ST205 ECU with rewiring would be your solution.
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Postby toayoztan » Sun Aug 15, 2004 9:17 am

ahh, okay, gotcha! So i'm guessing the umm..harder the bov is set, the less likely (not saying it will get rid of it) our cars will "run richer" or "stall"? I've got the mr2 bpv in my hands right now, i've just been lazy to put it on. I'm contemplating on the ssqv though. My cousin can grab me one for really cheap.

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Postby JDMGT4 » Sun Aug 15, 2004 12:33 pm

Thanks guys for your input....very informative. I'm not sure if I wanna install the BOV now because of that "running rich" issue I may run into.
Would running rich harm/damage the engine in the long run?

Gary how hard and expensive would it be for me to convert to speed-density system (do I have to change all 3 items you mentioned)?
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Postby mototebok » Sun Aug 15, 2004 2:17 pm

Only one of those 3 items would allow you to convert to MAP-temp based metering.

The running rich condition will wear out your spark plugs faster, and it may cause your cats and turbo to run alot hotter (unburned fuel igniting when hitting them) which will attribute to shorter life.

Just reroute it back into the intake, doing this will also reduce the turbo lag between shifts a little.
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Postby Gary » Sun Aug 15, 2004 2:57 pm

^^^^
What he said. :)
HKS VPC is probably the cheapest and easiest.
The used one costs around $300-$400
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Postby toayoztan » Sun Aug 15, 2004 10:28 pm

sorry to go off subject...so i may as well just stick with the mr2 bpv i have rather than gettin the ssqv and rerouting, huh? Well, guess i just need a T-hose now heh.

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Postby alltrac.net » Mon Aug 16, 2004 1:35 am

The SSQV can be re-circulated, but you need custom work on the intake piping. It's not fun but it can be done on the stock rubber piping. I re-circulated a Greddy Type S on my ST185 for smog purposes.

However, the SSQV is one of the few valves that works great without re-circulating. It typically closes very fast and does not cause stall issues in most cases.

You will still be rich between shifts and backfire at times if you have no cat.
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Postby OlyST185 » Mon Aug 16, 2004 4:57 am

yesss speed density with HKS VPC, get rid of that f*cking AFM :smokes:
:shoots: AFM
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Postby InitialD93 » Mon Aug 16, 2004 6:08 am

i know all about that... mine backfires regularly because i have stright through exhaust with the HKS not recirculated. actually blew out the midpipe exhaust flange gasket so i have a leak there not that i need to get fixed. but its always nice to have a car that smells like it has a 454 with a leaky carb :smokes:
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