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So guys the probem still persists. Finally a nice day to take the car to work. Logged my boost runs and peak boost is 144kpa. This is with the WG referenced to the manifold via my boost block (brake booster port at the back of the intake). So I had no pressure drop at 6psi. I looked at my boost gauge during one of the pulls and saw it spike to 7psi for a sec but was in 6psi most of the time so the MAP seems to be pretty accurate.
My guess is I need more spring? Should I crank down preload or should I just install my MBC and go from there? The car is quick at 6psi so If I could get to 10-12psi I would prob be happy. If the MBC will max boost at 2X spring pressure that would put me at 12psi which is golden.
I guess the 76/65 is just that restrictive on the exhaust side to cause excessive backpressure to open the 12psi spring at 1/2 its rating. I can hear the WG open but its not really all that loud (not like POP POP POP) its more like a louder rumbling exhaust leak. Maybe its because is a massive 60mm? Thoughts?
3bar OS and 3 bar MAP. Reads 100.5kpa KOEO. Vacuum gauge confirms MAP readings. For the boost side I’m running a innovate PSB1 electronic boost/vac and AFR gauge. Which matches my mechanical vacuum gauge etc.
so so before I left work I cranked down on the preload spring. All the way. Logs before showed 144kpa max, max out the preload and my log shows 154.3kpa max or about 8psi. My innovate boost gauge has a max boost recal and it showed 10psi as my max boost. My guess is that this could have been a spike that wasn’t caught on my log. Looking at the gauge I remember seeing 8psi mostly. The car is a complete animal to drive now. The tires break loose on medium/heavy throttle in 1 & 2 gears and on the shift to 3rd. I’m into boost by 3k and it just hangs out.
Logs also show at 8psi or 154.3kpa that I’m at about 72% duty cycle on the 60lb bosch injectors so she’s making power. Not sure if it’s worth increasing the boost too much since tire spin is now a problem.
BB, I'm talking to you on another thread about the filter breathers. I also have a cx kit on my truck with a 4.8. I referenced the top of my waste gate to my intake through the evap solenoid. I put a check valve in that line because I noticed when I had the switch on to allow air through that reference line it took longer to pass the boost threshold. The intake sucking on the WG from the top and the turbo pushing it from the side made it "fight" itself. After the check valve all was well. I hooked up a switch from the evap solenoid so that it only references the top when I flip the switch. It's a ridiculously cheap and easy way to double your boost.
CX says my spring is a 12 psi spring, which is absolute horseshit. they said the actual, identical waste gate I have on my truck put out 12psi on a bone stock motor. I have no idea how they got it to do that. When I put mine on I only made 8 psi. I'd say if you already have a MBC then just run that and be done with it. It's a helluva lot easier than respringing (because I know exactly what you're talking about having to compress it to change the spring).
BB, I'm talking to you on another thread about the filter breathers. I also have a cx kit on my truck with a 4.8. I referenced the top of my waste gate to my intake through the evap solenoid. I put a check valve in that line because I noticed when I had the switch on to allow air through that reference line it took longer to pass the boost threshold. The intake sucking on the WG from the top and the turbo pushing it from the side made it "fight" itself. After the check valve all was well. I hooked up a switch from the evap solenoid so that it only references the top when I flip the switch. It's a ridiculously cheap and easy way to double your boost.
CX says my spring is a 12 psi spring, which is absolute horseshit. they said the actual, identical waste gate I have on my truck put out 12psi on a bone stock motor. I have no idea how they got it to do that. When I put mine on I only made 8 psi. I'd say if you already have a MBC then just run that and be done with it. It's a helluva lot easier than respringing (because I know exactly what you're talking about having to compress it to change the spring).
thanks 07V. What thread was that?
I thought about just disconnecting the WG line but read that it would be wayyy high on boost bc it would be the exhaust only trying to push the valve open. So connecting to the side of the WG allows boost to help push on the spring to open the valve. The top is vented to atmosphere so the spring and boost are the only forces affecting the valve opening. By adding boost to the top with your solenoid or a MBC it just pushes back down on the spring and valve as the boost and spring are pushing it up. The top port doesn’t see FULL boost as pressure is bled off and thus it acts like a heavier spring. You can also bleed off boost to the side port only thus decreasing how much boost pushes the valve open and thus increase boost.
I opted to go with teeing into the side port to feed the MBC and have the MBC feed the top of the WG. It says to test the base lowest setting as it will add boost even when fully backed out over just normal operating boost.
So today I set everything back to original. Same spring and released all the preload on the single large spring. I disconnected the BOV and WG fed from the manifold and just have the BOV off manifold now. The WG is now referenced again to the compressor. The line from the compressor to the WG side port has been teed off and goes to the bottom of the voodoo MBC. The side port of the MBC goes to the top of the WG. I set it to the lowest pressure, the MBC is a spring and ball type with a Teflon ball (not
metal). This same setup before got me 6psi or 142Kpa on just the spring and hooked to the compressor. Now we will
see what the MBC can do. I like running the low psi spring so if something happens it will fall back to the 6psi base setting. I think I would be happy with 10psi since 8 was a noticable jump
from 6.
I thought about just disconnecting the WG line but read that it would be wayyy high on boost bc it would be the exhaust only trying to push the valve open. So connecting to the side of the WG allows boost to help push on the spring to open the valve. The top is vented to atmosphere so the spring and boost are the only forces affecting the valve opening. By adding boost to the top with your solenoid or a MBC it just pushes back down on the spring and valve as the boost and spring are pushing it up. The top port doesn’t see FULL boost as pressure is bled off and thus it acts like a heavier spring. You can also bleed off boost to the side port only thus decreasing how much boost pushes the valve open and thus increase boost.
I opted to go with teeing into the side port to feed the MBC and have the MBC feed the top of the WG. It says to test the base lowest setting as it will add boost even when fully backed out over just normal operating boost.
So today I set everything back to original. Same spring and released all the preload on the single large spring. I disconnected the BOV and WG fed from the manifold and just have the BOV off manifold now. The WG is now referenced again to the compressor. The line from the compressor to the WG side port has been teed off and goes to the bottom of the voodoo MBC. The side port of the MBC goes to the top of the WG. I set it to the lowest pressure, the MBC is a spring and ball type with a Teflon ball (not
metal). This same setup before got me 6psi or 142Kpa on just the spring and hooked to the compressor. Now we will
see what the MBC can do. I like running the low psi spring so if something happens it will fall back to the 6psi base setting. I think I would be happy with 10psi since 8 was a noticable jump
from 6.
you sound like you’re doing exactly what I did but with a **** instead of a switch! I think originally I was getting around 6 psi when I discovered a bunch of tiny boost leaks. Mainly in those god awful cold side clamps they give us. I bought legit ones and replaced all of them and saw a noticeable difference.
I had a issue with the muffler that I was using that drove the backpressure up so high I could only make 6 lbs. I opened the exhaust to straight and went straight to 14 lbs just like I was setup for. Just a idea for you to look at.
you sound like you’re doing exactly what I did but with a **** instead of a switch! I think originally I was getting around 6 psi when I discovered a bunch of tiny boost leaks. Mainly in those god awful cold side clamps they give us. I bought legit ones and replaced all of them and saw a noticeable difference.
lol I didnt even get the cold side. I already had a cold side from the supercharger but I to used real USA made clampco SS clamps as I had like 6 of the cheap chinese ones with the tubing kit rip and snap. I know the cold side has been up to 9-12psi with no leaks and I remember pressure testing it to like 20psi.
I had a issue with the muffler that I was using that drove the backpressure up so high I could only make 6 lbs. I opened the exhaust to straight and went straight to 14 lbs just like I was setup for. Just a idea for you to look at.
What muffler was that? I thought about that as well. I run 2 mufflers. A 13: straight through perforated core muffler where the cat would be and then out back is a dynomax ultra flow SS which is essentially a straight through perforated core design as well. I dont think my mufflers are that much of a restriction but the thought did cross my mind. They can't be more of a restriction than a 65mm exhaust wheel lol.
The thing is that adding preload to the spring upped the PSI about 2psi, so I feel like its capable of more boost but that single large spring just isnt enough force. Tightening down the preload was almost effortless so thats my guess.
Well guys Its making more boost. With the WG referenced to the compressor and the MBC sending boost signal to the top of the WG (on the lowest setting of the MBC) It managed 161.8kpa on the logs. Thats about 8.5psi converted to boost. Originally the same setup without the MBC was about 6psi so that means the MBC added 2.5psi at its lowest setting. I was looking at my boost gauge and saw it peak around 10psi again (prob a spike) as its an electronic gauge.
Prob going to crank it up a 1/2 turn at a time till I get to around 10psi.
Does anyone have the formula to calculate HP based on injector duty cycle? I'm at 77.7% injector duty cycle with 60lb at the 8.5psi.
I backward engineered online injector duty cycle calculators (figured it was worth a shot) to figure out estimated crank HP. I set my injector flow, and .065 BSFC (turbo) and set max duty cycle to 77.7%. Says 574hp (crank) is what it would support... any idea if this could be accurate? My AFR was 11.75:1 at that 161.8kpa, 60lb at 43.5psi (rail pressure) on a 1:1 aeromotive regulator. Intersted to see how the duty% increases as boost increases since I saw almost 20% duty% increase going from 6 - 8.5psi.
I agree, Its just an estimate really which is fine for me. I'm not about eeking out all the power which is why my timing is low for safety even with 93 pump, FMIC and 50/50 meth.
I actually just found out that my meth wasn't working. Apparently it was receiving power but it was throwing a "open circuit" code on my AEM progressive controller. Apparently the fuse popped (LED illuminated) and even tho it was still receiving enough power to turn on but not activate the pump. Flow gauge is showing about 550cc/min flow on the AEM meth flow gauge.
whether or not you take this on board is entirely up to you.
65mm turbine wheel in a .81 housing is quite restrictive even for 5.3.
single turbo LS require big turbine wheel and housings to flow the exhaust gas and make easy power. this is why the Borg Warner range work so well. they have relatively large turbine wheels and housing flow for the attached compressor wheel.
choke the exhaust side in single turbo LS they come on hard, but then roll over early as the cant flow the gas out.
your set up has gate spring and boost reference to bottom of gate to overcome the spring and open it. your signal line isn't the only force trying to open the gate. the exhaust manifold pressure is also trying to push the gate open. force is a pressure over area equation. with a 60mm gate the same exhaust manifold pressure is going to apply a lot more force than it would on a 38 or 44mm gate.
once your turbo is on song and the engine gets up in RPM your manifold back pressure is building and pushing the gate open causing the gate to open at a lesser "boost" pressure than your installed spring.
by adding boost signal to the top of the gate you're effectively trying to hold the gate shut by assisting the spring pressure applied to the diaphragm. boost is only a restriction to flow. by clamping the gate shut you're choking the engine even harder. I have personally seen 3x single turbo LS with small turbine wheels break ring lands from excessive exhaust manifold back pressure created by far too much gate spring to achieve the desired boost.
you either need to cap your boost level low, limit RPM or put a suitable turbo on. when everything flows you will find that your gate spring pressure how you originally had yours set up is damn near your boost pressure.
next time you take a **** clamp down on your dick and reduce your flow by 3/4 and see how it makes you feel. that is exactly what you're doing to your engine holding the gate shut.
dump pipe, crossover tube and manifold size/design also contribute to the problem, however in your case it is turbine wheel and housing.
While i I would agree with almost everything your saying I feel like the turbo is NOT too small. Reason being that the Engine has been to 5500 and power is not falling off, boost isn’t dropping and it’s not hitting a brick wall rpm wise. Cybergrey on here was running the same system and turbo on a larger 5.7 and the turbo wasn’t holding him back. Remember I’m running a 5.3 so the smaller cubes helps with the turbo being small, a larger .96ar would have helped flow but at the cost of slower spool. I do have a vs racing 78/75 on the shelf but I don’t want to put it on unless I know this turbo is all done. I do like the spool on this one, it’s very fun to drive on the street. Also denmah did one on a Fairmont with a 5.3 and the 76/65 and he loved it on the street, wasn’t done till about 600rwhp.
I do agree that the turbo is on the small size exhaust wise but it serves my purpose which is low rpm boost for street driving. Very rarely do I get to 5500 unless I’m going for gold to get on the highway. Positive pressure starts at 3k which is a good rpm for the street.
Heres something i havent mentioned. My WG seems to open rather early or feels early so like it’s already open by 4K as it’s regulating 6-8psi boost. It almost sounds feels like a medium “hum” not as loud as some people say open dump pipes are. I really don’t get to hear any turbo spool which kinda of sucks. I’m not looking for a ton of boost, 10psi would be good for the street.
Thats a good point about the 60mm valve causing more pressure on the spring, didn’t really think of that. It was pointed out by someone here that the 60mm valve only has to open slightly to bleed enough exhaust and thus boost. Maybe that’s why it’s not as loud as I thought it would be.
I have a few WG springs from other gates that I have purchased/used on other projected. I have tested them
by hand and I have (red which is 8psi, Black which is 6psi) and when I pulled the WG apart and checked the spring that netted me 6psi and it felt stiffer than the 6psi but weaker than the 8psi, so I would guesstimate it’s a 7psi spring. I put it in with the medium sized spring that came with the gate and that opened at like 25-27psi. The 6-7psi spring cracks open at 12-13psi. So I grabbed another spring I would guess was around 4psi and threw that in with it. I tested them together and it cracks open around 20psi. I’m going to see what that gets me boost wise. I was reading on line that the cracking pressure is higher than boost pressure as the spring manufacture/designer takes into account WG backpressure to achieve the correct boost. Of course a tiny turbo housing can create more backpressure than they accounted for and thus affect the boost pressure. But I also read that a 2:1 ratio is common, so 2x exhaust pressure to boost pressure.
Last edited by customblackbird; 04-28-2018 at 11:48 PM.
While i I would agree with almost everything your saying I feel like the turbo is NOT too small. Reason being that the Engine has been to 5500 and power is not falling off, boost isn’t dropping and it’s not hitting a brick wall rpm wise.
I do agree that the turbo is on the small size exhaust wise but it serves my purpose which is low rpm boost for street driving. Very rarely do I get to 5500 unless I’m going for gold to get on the highway. Positive pressure starts at 3k which is a good rpm for the street.
Heres something i havent mentioned. My WG seems to open rather early or feels early so like it’s already open by 4K as it’s regulating 6-8psi boost. It almost sounds feels like a medium “hum” not as loud as some people say open dump pipes are. I really don’t get to hear any turbo spool which kinda of sucks. I’m not looking for a ton of boost, 10psi would be good for the street.
Thats a good point about the 60mm valve causing more pressure on the spring, didn’t really think of that. It was pointed out by someone here that the 60mm valve only has to open slightly to bleed enough exhaust and thus boost. Maybe that’s why it’s not as loud as I thought it would be.
I have a few WG springs from other gates that I have purchased/used on other projected. I have tested them
by hand and I have (red which is 8psi, Black which is 6psi) and when I pulled the WG apart and checked the spring that netted me 6psi and it felt stiffer than the 6psi but weaker than the 8psi, so I would guesstimate it’s a 7psi spring. I put it in with the medium sized spring that came with the gate and that opened at like 25-27psi. The 6-7psi spring cracks open at 12-13psi. So I grabbed another spring I would guess was around 4psi and threw that in with it. I tested them together and it cracks open around 20psi. I’m going to see what that gets me boost wise. I was reading on line that the cracking pressure is higher than boost pressure as the spring manufacture/designer takes into account WG backpressure to achieve the correct boost. Of course a tiny turbo housing can create more backpressure than they accounted for and thus affect the boost pressure. But I also read that a 2:1 ratio is common, so 2x exhaust pressure to boost pressure.
horses for courses. The smaller the turbine side the sooner they come on boost. Everyone’s goals are different and if early spool is your thing and you don’t swing it to 7000rpm everyday then that is the perfect choice for you.
if it were feasible and practical I would have a pressure gauge at the turbo flange in every set of manifolds. Would take all the guess work out of everything and paint a clear picture.
i have found that with no boost controller the gate cracks early. And it comes on more linear and less aggressive. As soon as it makes pressure it’s sending signal to the gate. With a boost controller you can ensure no signal goes to the gate until you ask for it. They come on heaps harder.
I am by no means full bottle on turbo design or application. I only go off what I see and learn first hand.
from what I’ve seen single LS with large exhaust wheels seem to work well. Example of comp vs turbine
BW s475 75mm/88mm
S480 80mm/88mm
S400 67mm/83mm
gtx4202 75mm/83mm
precision 75mm/76mm
gt4718. 88mm/93mm
ive seen all of those used on 6.0 to 400 cubes as single turbo. The turbos with close comp and turbine wheel sizes all choke and restrict power up in rpm with decent boost.
however for smaller cubes they work well. Or In case of 400 cubes set up as twins
most jap cars use a close wheel size as they don’t have to move the volume of gas in most cases. I have a twin cam 4.0ltr 6 cylinder and use a gtx4202 and it works well. But I know when I jam 6.0ltrs through the same turbo after 15psi I can see the back pressure in the manifolds with every psi I add on the dyno. The power rolls over ever so slightly earlier and the cylinder combustion becomes much more prone to detonation after the power rolls.
but yes, bigger the turbine wheeel and housings the more lags. Generally we just set up a quality converter with an appropriate stall speed to suit the combos lag.
04-24-2018, 10:53 AM
