Obverboost after new BOV??

[lovemym]

I just read all of 25 posts about over boosting, but ofcourse ever case is a little different, so here goes. I got a new blitz BOV (that i recirculated) and the hard pipe for it that goes to the intercooler. Soon as I took if for a test drive and it was wickedly fast. So I ordered the new MSD Lazer boost gauge hooked it up and it said I was running 20 PSI?! I actually passed some one on the way home and it went to 25PSI and hit fuel cut. I came home and checked all hoses, it is still running the stock BCS with the restrictor removed. It pulls real hard spikes at 20 or more then walks back down to around 15 if I stay on it. The only other aftermarket parts I have installed are the Thermal Cat back, and aftermarket intake. Everything else is stock. Its a 97 GST. I did go out and move the actuator by hand on the waste gate to so its not stuck. Its just crazy that I did that one mod and this happend please help.

 

[rocafellafw]

Do you have a boost controller ?

 

[JusMX141]

Do you have a boost controller ?

Ummm....

it is still running the stock BCS with the restrictor removed.

What size is your downpipe; is it still stock? It almost sounds like you're suffering from boost creep.

 

[lovemym]

No its still using the factory BCS. O and if I rev it up while looking at the wastgate I can see it opening also. So that seems to be working fine.

 

[rush2252]

It sounds like maybe your gauge maybe a little off? 25psi before fuel cut? dont the 2gs cut fuel at 16psi

 

[clean96GST]

It sounds like maybe your gauge maybe a little off? 25psi before fuel cut? dont the 2gs cut fuel at 16psi

Idk about 16, but I doubt it would get anywhere near 25.

 

[lovemym]

Yeah the down pipe is still stock. I hooked up the gauge to the fuel pressure solonoid. Most of the time when I get on to it, it would be 20-22 psi, and it didnt cut out but one time I went into 3rd to go around some one and it boosted then cut out like I hit a brick wall, then it just picked right up again because I never lifted. So then I looked at my gauge and it said I had just hit 25!! But then I decided to get on it one more time and look at the factory gauge and it went almost to the + line but not quite. I was thinking if I would boost that much it would be off the factory gauges scale? Boost creep would mean it would creep up right? Well it spikes soon as I hit the gas, then goes down a few psi.

 

[kenamond]

Get a piece of vaccuum line and run it from the T25 compressor outlet nipple straight to the WGA nipple. While you're at that, use a pressure tester to see what pressure causes the WGA to open (put the pressure tester on the WGA nipple). With the stock BCS bypassed, you should run ~9psi boost. If that doesn't happen, either your gauge is really off, your WGA isn't properly opening the wastegate, or you're creeping (I can't think of anything else).

Oh, make sure your boost gauge is in psi and not in-Hg for positive (boost) pressure. I doubt it's that (25in-Hg is only about 13psi), but it's easy to check. If it is in in-Hg, then you probably have a boost leak to be hitting fuel cut at 13psi.

I'm all out of ideas now.

 

[lovemym]

Well I was really hoping you were right about the HG thing I remembered seeing HG on the gauge but its only for Vacuum. It measures vacuum in HG and boost in PSIG. So just to make sure im taking my laptop out to the car and see if there is a setting in it I can change.

 

[rush2252]

i believe its metric system measurement for mass.. Hilogram? correct me if im wrong..

 

[lovemym]

Well no settings to change from HG to PSI so I guess it just does PSI. It says PSI on the face so I guess it only reads in PSI. The only changes it would let me do were for brightness and stupid stuff like that. The only thing I can think of is the fact that this gauge actually reads the current atmospheric pressure every time I start the car, and then calibrates itself. So is it going to be that different than a regular old gauge?

 

[lovemym]

well im getting ready to go see if I can get a pressure tester. how many pounds of pressure should it take? Just so I know right then if its working correctly. Like I said above I can watch it move just from reving the car up and watching it, and according to the boost gauge it peaks around 5psi when just blipping the throttle like that.

 

[snowborder714]

Oh, make sure your boost gauge is in psi and not in-Hg for positive (boost) pressure. I doubt it's that (25in-Hg is only about 13psi), but it's easy to check. If it is in in-Hg, then you probably have a boost leak to be hitting fuel cut at 13psi.

Do you happen to mean BAR? I've never seen inHg associated with boost - only with vacuum.

well im getting ready to go see if I can get a pressure tester. how many pounds of pressure should it take? Just so I know right then if its working correctly.

I would do your boost leak test up to 20psi. Typically I pressure test to 5psi or so more than I plan to run, just so I know if it creeps a bit for some reason it'll hold. It should take a while to bleed off. While you're doing it, spray your engine down with soapy water so you can "see" your boost leaks by the bubbles it'll produce.

Well no settings to change from HG to PSI so I guess it just does PSI. It says PSI on the face so I guess it only reads in PSI. The only changes it would let me do were for brightness and stupid stuff like that. The only thing I can think of is the fact that this gauge actually reads the current atmospheric pressure every time I start the car, and then calibrates itself. So is it going to be that different than a regular old gauge?

My guess is your boost gauge is only for PSI. You'll want one that reads vacuum (inHg) as well.

Is it an electronic gauge (wires running to it) or manual (vacuum line running to it)?

 

[lovemym]

Ok I just called a friend that has built countless Eclipses and has been in the business of doing so for 15 years and he told me to just leave it alone. Soon as I told him what I did as far as putting on the blow off valve he finished my sentence and said it boosts to 20 something and bleeds back off right? I said yes and he said it will not cause any problem on a T25. He said that its just because the head flows so much and the turbo is to small to get rid of the extra pressure caused by the new BOV. He just told me to stay off of it if its real hot outside. I went ahead and did the U with the vacuum line and it went down to peaking at 17 PSI so ill probably just leave it like that. If anyone that really really knows what they are talking about knows anything different than please let me know. He said one of his customers has been running his car like that for years and is still on the stock t25.

 

[JusMX141]

Well I was really hoping you were right about the HG thing I remembered seeing HG on the gauge but its only for Vacuum. It measures vacuum in HG and boost in PSIG.

i believe its metric system measurement for mass.. Hilogram? correct me if im wrong..

HILOGRAM?



You guys.....

C'mon now- I might've failed 11th Grade Chemistry but I knew my Periodic Table like nobody's business. inHg = Inches Of Mercury, the same type of barometric pressure measurement used by Meteorologists....although barometric pressure reads positive in terms of our atmosphere and negative in terms of our intake manifolds.

Ok I just called a friend that has built countless Eclipses and has been in the business of doing so for 15 years and he told me to just leave it alone. Soon as I told him what I did as far as putting on the blow off valve he finished my sentence and said it boosts to 20 something and bleeds back off right? I said yes and he said it will not cause any problem on a T25. He said that its just because the head flows so much and the turbo is to small to get rid of the extra pressure caused by the new BOV. He just told me to stay off of it if its real hot outside. I went ahead and did the U with the vacuum line and it went down to peaking at 17 PSI so ill probably just leave it like that. If anyone that really really knows what they are talking about knows anything different than please let me know. He said one of his customers has been running his car like that for years and is still on the stock t25.

Fifteen years, eh?

I suppose this fellow and myself could have some awesome conversations. I tend to absorb knowledge like a sponge yet repel bullshit like oil to water.

 

[xsboost]

Hilogram!! That's classic!! You learn something new everyday huh?

 

[lovemym]

Yeah we met back when we were teens, now we are in our mid 30's. He's had 6 or so 1st gens. Now with his company doing so well he still has 1 Eclipse but he also has a 05 BMW 745i, and older 5 series wagon and a big lifted F350 and all of them are modded very nicely. Speed Styles | HOME | The Art of Import Performance, Charlotte, NC if ya wanna see. So does anyone disagree with what he said that knows what they are talking about? I mean I trust Marcus a whole lot he has had a few of his eclipses into the 9's and thats fwd, so I know he knows his crap. I just ask to be on the safe side I would really like another opinion.

 

[kenamond]

I don't mean to diss your friend, but boosting a T25 to 20psi on stock fuel with a stock sidemount intercooler is a horribly bad idea. The T25 is on its way out of its efficiency range at 13psi and will be blowing very hot air at 20psi.

Also, the only reason a BOV would help you with boost is if you were overboosting on the stock BOV but it was opening at 13psi (that's when it can't hold any more boost) and recirculating all of that hot air. In other words, you may have had this overboosting problem before the BOV, but since it can't hold high boost, it was saving your ass. A BOV is not supposed to have anything to do with boost control. It's job is to open and relieve boost pressure when you let off the gas and the throttle closes and there's no where for that boost to go. If you didn't have the BOV, the air would back up in the intake and cause the compressor wheel to stall (surge), and the increased pressure on the wheel would put thrust on the bearings that the turbo wasn't designed to tolerate.

The bottom line is that if your boost is uncontrolled, you're probably knocking badly and maybe leaning out, too. The stock fuel system can't support more than about 15psi. Also, the stock sidemount can't cool all of that hot air, and too hot means knock.

So fix the problem. Do the test I recommended to see if you can get your boost under control. Do a boost leak test and fix all leaks so that you can hold 20psi of test pressure and leak down about 1psi every 3-5 seconds. Check the vaccuum lines that connect between your turbo compressor nipple WGA nipple, and BCS nipple to make sure it's not cracked or disconnected. There is a problem if you're truly boosting to 20psi on stock boost control, and it might cost you your turbo, motor, or both even if the car feels great to drive.

As far as in-Hg, that was a wild guess. I've seen boost in psi and bar, but never in-Hg, but it was worth a shot. By the way, 1 bar is about the same as 15psi, so if he was hitting 20bar, that'd be SICK (300psi boost).

 

[4pistons]

He said that its just because the head flows so much and the turbo is to small to get rid of the extra pressure caused by the new BOV.

A Compressor Bypass Valve (or BOV as it's incorrectly called) does not 'cause' any pressure at all. Quite the opposite... it "Blows Off' pressure, so I don't know how it could affect your boost level. Unless your old one leaked and this new one is now holding that pressure.

if you were overboosting on the stock BOV but it was opening at 13psi (that's when it can't hold any more boost)

The stock BOV is known to leak due to design flaws but can 'hold' (meaning stay shut) at any boost level. It's not really a Blow Off Valve or a Pop Off Valve, it's a pressure differential valve. It opens when pressure on the front side is greater than the pressure on the back side plus the spring pressure.

The small vacuum hose that's connected to the backside of the 'BOV' is allowing just as much pressure on the back of the diaphram as the boost pressure in the intake is exerting on the front. At WOT the pressures are always equal.

When the throttle is closed the intake piping is still pressurized while the engine (everything behind the throttle plate) is suddenly in vacuum, including that small hose to the backside of the 'BOV', which now opens due to the difference in pressure on the front and back of the diaphram.

Its purpose isn't to control boost, the wastegate does that, it is designed to keep the pressure wave from bouncing off the closed throttle plate and back into the compressor blades of the turbo, which can cause major damage. Hence the name Compressor Bypass Valve.

Rick - '91 GSX

 

[rush2252]

Hilogram!! That's classic!! You learn something new everyday huh?

yeh i got a good laugh after rereading. I knew it was involved with the metric system though ha!

 

[lovemym]

Well I did further investigation on the gauge and decided to call MSD. In the instruction to hooking it up it says it needs power from switched 12volts so I hooked it up to the cig lighter power. I called and asked him how it said it needs 12 volts from switched because it needs to read the barometric pressure everytime so its accurate, and that it actually cuts off while being started and then comes back on. So he said It needs to stay constant while the car is being started so I tapped the power into the fuel pressure solenoid and presto it works! Now the car peaks at 17Psi and then stays around 15 or lower. So I guess im in the clear after all. Thanks for all the help guys I really do appreciate it.

 

[thilaksharma]

i have my own experience on "higher boost after BOV change"
my case was , I was using the STOCK pbv/bov before changing to a Blitz
on the stock bov i was running close to 12-14psi , when i switched to blitz
it went up to 22psi , that was weird ? i did drive off boost for a month or two
and switched to a external wastegate setup , it was back on the stock wastegate boost
tht was when i realised , the actuator was in a bad shape, that was the reason it boosted up high
with the stock pbv/bov it boosted low cos it was just leaking out the boost