Do I need an external wastegate??
Nov 17, 2011, 02:13 PM
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Nov 17, 2011, 04:52 PM
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Hey, so do you guys have rubber gromets in the the solenoid hole where you screw in the nipples? Because I don't, and I think it logically makes sense for the boost creep up and be unstable if there are leaks there.
As sparky mentioned it's pretty much stock and don't think I need/want external unless I'm upgrading my turbo.
Nov 17, 2011, 07:03 PM
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Nov 17, 2011, 07:42 PM
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I asked which housing is on the turbo because the 9.8 will exhibit more of a propensity to creep, or spike than the 10.5 especially in that 17-19 PSI range where you are experiencing boost control issues. The 9.8 housing gives you quicker spool and better transient response, but shaft speeds will be higher with the smaller housing than with the 10.5.
The 9.8 housing has a more constricted turbine inlet area which is where the wastegate bypass ports originate. The tight 90* turn in radius from the inlet area into the bypass ports makes it more difficult for the bypass port to bleed off the exhaust gas flow before it hits the turbine blade tips especially as the flapper valve just starts to lift off its seat. The relatively high velocity exhaust flow tends to keep moving axially straight through the scroll passageways. In the 9.8 housing it is more difficult to redirect the bypass flow out through the wastegate passage.
In general, the 9.8 will produce higher shaft speeds, make it harder to slow the compressor down, and have less bypass efficiency overall than the 10.5 housing. The increased speed of the turbine wheel tends to maintain rotational momentum when you lift off the throttle. So, the boost control window as the compressor is entering its efficiency range is more limited with the 9.8 housing in comparison to the 10.5 housing.
The 9.8 housing has a more constricted turbine inlet area which is where the wastegate bypass ports originate. The tight 90* turn in radius from the inlet area into the bypass ports makes it more difficult for the bypass port to bleed off the exhaust gas flow before it hits the turbine blade tips especially as the flapper valve just starts to lift off its seat. The relatively high velocity exhaust flow tends to keep moving axially straight through the scroll passageways. In the 9.8 housing it is more difficult to redirect the bypass flow out through the wastegate passage.
In general, the 9.8 will produce higher shaft speeds, make it harder to slow the compressor down, and have less bypass efficiency overall than the 10.5 housing. The increased speed of the turbine wheel tends to maintain rotational momentum when you lift off the throttle. So, the boost control window as the compressor is entering its efficiency range is more limited with the 9.8 housing in comparison to the 10.5 housing.
Last edited by sparky; Nov 18, 2011 at 04:13 AM.
Nov 17, 2011, 09:31 PM
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See how you have to screw in the nipple? And I think there is a rubber o-ring inside the hole in the picture to keep the boost from leaking? See I don't have any o-rings on both holes so it's just metal-to-metal contact.
Last edited by stevolution84; Nov 17, 2011 at 09:35 PM. Reason: Forgot to attach the pic
Nov 17, 2011, 09:34 PM
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I asked which housing is on the turbo because the 9.8 will exhibit more of a propensity to creep, or spike than the 10.5. The 9.8 housing gives you quicker spool and better transient response, but shaft speeds will be higher with the smaller housing than with the 10.5. The 9.8 exhibits a higher propensity to spike, or creep, especially in that 18-19 PSI range.
The 9.8 housing has a more constricted turbine inlet area which is where the wastegate bypass ports originate. The turn in radius from the inlet area into the bypass ports has a tighter radius....So, it is more difficult for the bypass port to bleed off the exhaust gas flow before it hits the turbine blade tips. The high velocity exhaust flow tends to keep moving axially straight through the scroll passageways. In the 9.8 housing it is more difficult to redirect the bypass flow out through the wastegate passage.
In general, the 9.8 will produce higher shaft speeds, make it harder to slow the compressor down, and thus have less bypass efficiency overall than the 10.5 housing. The increased momentum of the turbine wheel due to the higher relative shaft speeds is more difficult to slow down. So, the boost control window as the compressor is entering its efficiency range is becomes more critical with the 9.8 housing in comparison to the 10.5 housing.
The 9.8 housing has a more constricted turbine inlet area which is where the wastegate bypass ports originate. The turn in radius from the inlet area into the bypass ports has a tighter radius....So, it is more difficult for the bypass port to bleed off the exhaust gas flow before it hits the turbine blade tips. The high velocity exhaust flow tends to keep moving axially straight through the scroll passageways. In the 9.8 housing it is more difficult to redirect the bypass flow out through the wastegate passage.
In general, the 9.8 will produce higher shaft speeds, make it harder to slow the compressor down, and thus have less bypass efficiency overall than the 10.5 housing. The increased momentum of the turbine wheel due to the higher relative shaft speeds is more difficult to slow down. So, the boost control window as the compressor is entering its efficiency range is becomes more critical with the 9.8 housing in comparison to the 10.5 housing.
Is it normal to see Evos without any/much exhaust restrictions on a stock turbo with 9.8 housing to require external wastegate?
What I've tried today was to cruise at aroun 4Krpm then suddenly boost. Spikes upto about 22psi before I quickly let the gas down.
Sigh, on the verge of blowing my engine...
Nov 18, 2011, 03:58 AM
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Hmmm. Is that Hondata solenoid an integral part of your boost control circuit along with the EBC? You are full of surprises aren't you! You have been holding out on us.
No, you do not need an external gate. You have enough gizmos and doodads on there as it is.
We are going have to start you back at square one. You don't need a fancy EBC or that boost control solenoid to control boost on your setup. Do you have rudimentary hand tools and the basic wrenching skills? Are you willing to skin your knuckles?
No, you do not need an external gate. You have enough gizmos and doodads on there as it is.
We are going have to start you back at square one. You don't need a fancy EBC or that boost control solenoid to control boost on your setup. Do you have rudimentary hand tools and the basic wrenching skills? Are you willing to skin your knuckles?
Nov 18, 2011, 04:48 AM
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Last edited by sparky; Nov 18, 2011 at 05:32 AM.
Nov 18, 2011, 04:59 AM
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This, Ratster, is the million dollar question. To find out, he is going to have to totally disconnect the EBC and the BCS, plug the open hose ends, run a single, new and dedicated 4mm hose from the compressor J-pipe nipple to the nipple on the WGA. Then he should proceed to adjust the length of the actuator rod to arrive at the base pressure setting. Then, from the base setting, he will need to incrementally increase spring pressure up to his target boost level, which I think is about 18 PSI, to verify whether or not on straight WG spring pressure he still gets creep.
If via the method outlined above, he has eliminated creep...then, end of story, it was an EBC/BCS issue all along. In which case he would be better served by switching boost control duties over to a MBC.
If, on the other hand, after performing the above test, the creep issue remains....then it would be time to either port the wastegate bypass port entrance inside the turbine housing, port the crossover hole in the O2 housing, or install an O2 dump.
If via the method outlined above, he has eliminated creep...then, end of story, it was an EBC/BCS issue all along. In which case he would be better served by switching boost control duties over to a MBC.
If, on the other hand, after performing the above test, the creep issue remains....then it would be time to either port the wastegate bypass port entrance inside the turbine housing, port the crossover hole in the O2 housing, or install an O2 dump.
Last edited by sparky; Nov 18, 2011 at 05:36 AM.
Nov 18, 2011, 12:15 PM
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The hondata pic was just to show you what I meant by the o-ring and the nipple
I was thinking without the o-rings inserted, at boost there will be leaks which will cause the internal wastegate to close = boost instability.When I had stock exhaust system with ECU controlled boost solenoid, the boost goes up to about 19 then tapers down to about 16~17 so I think that means the internal wastegate is fine?
Hm, right now it's 9.12am here. I think the differences are 19 hours.