Dual wastegates = better boost control on high boost set-up's?
03-03-2008, 07:54 PM
#1
Honda-Tech Member
Thread Starter
Join Date: Nov 2004
Location: Spinning, FL, USA
Posts: 2,460
Likes: 0
Received 0 Likes
on
0 Posts
Dual wastegates = better boost control on high boost set-up's?
My friend has a 4g63 with a twin scroll manifold and a single gate, the lowest boost he runs is 19psi. That is fine because it is a race car. Another guy is telling us that twin gates are better for high boost control. We dont have a problem with the single gate at 40-45psi though?
Someone told me this:
"too much backpressure creates more turbine speed which causes inefficiency by over spinning the turbo.. This is why alot of guys are going to those turbine wheel rpm gauges and also why they measure backpressure to make sure the housing, head, turbo are all working correctly and flowing close to an optimal 1:1.."""
Now, it seems to me that a turbo works at its best efficiency with no back pressure at all to stop it spinning up. Some manufacturers warn of over spin but in all intensive purposes you would only ever achieve this scenario in running with no exhaust. Backpressure wouldnt cause the turbo to overspin, Not enough backpressure would.
Am i on the right track? Or completely off?
Someone told me this:
"too much backpressure creates more turbine speed which causes inefficiency by over spinning the turbo.. This is why alot of guys are going to those turbine wheel rpm gauges and also why they measure backpressure to make sure the housing, head, turbo are all working correctly and flowing close to an optimal 1:1.."""
Now, it seems to me that a turbo works at its best efficiency with no back pressure at all to stop it spinning up. Some manufacturers warn of over spin but in all intensive purposes you would only ever achieve this scenario in running with no exhaust. Backpressure wouldnt cause the turbo to overspin, Not enough backpressure would.
Am i on the right track? Or completely off?
03-03-2008, 08:31 PM
#2
Junior Member
Join Date: Dec 2005
Location: somewere, tx, usa
Posts: 774
Likes: 0
Received 0 Likes
on
0 Posts
Re: Dual wastegates = better boost control on high boost set-up's? (OMG B16)
If the turbo is balanced then you don't need to worry about how fast it spins. running Two waste gates is ok if you really just want bling for the set up your running. if your not creeping or spiking then don't worry about it. If you are then go with a 44mm. i have seen supra's that run twin 44mm gates but that's b/c they are pushing 1600hp.
03-04-2008, 10:42 AM
#4
Honda-Tech Member
Thread Starter
Join Date: Nov 2004
Location: Spinning, FL, USA
Posts: 2,460
Likes: 0
Received 0 Likes
on
0 Posts
Re: Dual wastegates = better boost control on high boost set-up's? (moores55)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by moores55 »</TD></TR><TR><TD CLASS="quote">If the turbo is balanced then you don't need to worry about how fast it spins. running Two waste gates is ok if you really just want bling for the set up your running. if your not creeping or spiking then don't worry about it. If you are then go with a 44mm. i have seen supra's that run twin 44mm gates but that's b/c they are pushing 1600hp.</TD></TR></TABLE>
Kinda what i figured. This car was on a GT4202 (45psi) with a 180shot. Automatic transmission. Now its on a S400 with the 180shot. Going for the worlds fastest automatic dsm record.
I was asking because the new manifold is almost done, just needs the wastegate side of it done. Hes gonna stick with one 44mm and see how it does.
Thanks for the reply.
Kinda what i figured. This car was on a GT4202 (45psi) with a 180shot. Automatic transmission. Now its on a S400 with the 180shot. Going for the worlds fastest automatic dsm record.
I was asking because the new manifold is almost done, just needs the wastegate side of it done. Hes gonna stick with one 44mm and see how it does.
Thanks for the reply.
03-04-2008, 04:16 PM
#5
Honda-Tech Member
Join Date: Dec 2003
Location: bumfuck egypt, SD, US
Posts: 920
Likes: 0
Received 0 Likes
on
0 Posts
Re: Dual wastegates = better boost control on high boost set-up's? (OMG B16)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by OMG B16 »</TD></TR><TR><TD CLASS="quote">
Now, it seems to me that a turbo works at its best efficiency with no back pressure at all to stop it spinning up. Some manufacturers warn of over spin but in all intensive purposes you would only ever achieve this scenario in running with no exhaust. Backpressure wouldnt cause the turbo to overspin, Not enough backpressure would.
Am i on the right track? Or completely off?</TD></TR></TABLE>
It always throws me off when people talk about backpress with a turbo. I always think they're referring to pressure in the exhaust manifold, which is what they Should be talking about, since you shouldn't have any backpress in the exhaust system with a turbo..or ever, actually. But then backpress after the turbo is always what they're talking about.
Backpress isn't something you should try to factor in for boost control. Backpress in the exhaust after the turbo should be eliminated, to maximize the pressure differential across the turbine with the lowest pressure in the manifold. A reduction in backpress after the turbo can cause boost creep, since by increasing the pressure differential across the turbine, the wastegate has to bypass more to drop that manifold press to get that back in line, and if it can't, there you go, boost creep.
I don't know exactly what you mean by overspin, do you mean overboost or just spinning the turbo out of its efficiency range? Either way, this can be achieved regardless of exhaust backpress..
As far as the twin gate thing, you need more wastegate capacity the lower you boost, for a given setup, not the other way around. What drops the boost, the wastegate opening, so if you boost high, you can get away with a smaller gate.
Now, it seems to me that a turbo works at its best efficiency with no back pressure at all to stop it spinning up. Some manufacturers warn of over spin but in all intensive purposes you would only ever achieve this scenario in running with no exhaust. Backpressure wouldnt cause the turbo to overspin, Not enough backpressure would.
Am i on the right track? Or completely off?</TD></TR></TABLE>
It always throws me off when people talk about backpress with a turbo. I always think they're referring to pressure in the exhaust manifold, which is what they Should be talking about, since you shouldn't have any backpress in the exhaust system with a turbo..or ever, actually. But then backpress after the turbo is always what they're talking about.
Backpress isn't something you should try to factor in for boost control. Backpress in the exhaust after the turbo should be eliminated, to maximize the pressure differential across the turbine with the lowest pressure in the manifold. A reduction in backpress after the turbo can cause boost creep, since by increasing the pressure differential across the turbine, the wastegate has to bypass more to drop that manifold press to get that back in line, and if it can't, there you go, boost creep.
I don't know exactly what you mean by overspin, do you mean overboost or just spinning the turbo out of its efficiency range? Either way, this can be achieved regardless of exhaust backpress..
As far as the twin gate thing, you need more wastegate capacity the lower you boost, for a given setup, not the other way around. What drops the boost, the wastegate opening, so if you boost high, you can get away with a smaller gate.
Thread
Thread Starter
Forum
Replies
Last Post
alteredautosports
Drag Racing
20
01-11-2006 06:08 PM
SOHC_MShue
Forced Induction
16
06-15-2004 09:52 PM
boost, connection, control, creep, dual, gt4202, high, hp, installation, list, setup, supra, turbocharger, wastegate, wastegates
