Question about psi and velocity
02-06-2008, 06:06 PM
#1
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Question about psi and velocity
First off, sorry for the newb question.....
Im tryin to figure out why at 10psi my 2 different turbos are at different AFR's.
At first i had t3/t4 57 trim on it tuned pretty well to an 11.8-12.0 afr. So then i picked up a holset HX35 with the 16cm housing and left everything the same as far as boost pressure. The holset is a bit laggier obivously (but not much) but once i got it on, the tune for the t3/t4 was waaay lean. And once i got the holset to an AFR of about 11.8-12.0 and at the same 10psi, the car is noticeably faster and pulls much harder. And i had to add quite a bit of fuel to the map, but kept the same ingnition numbers.
So....
Does that mean that the holset is flowing more air at the same PSI..... more velocity?
Im tryin to figure out why at 10psi my 2 different turbos are at different AFR's.
At first i had t3/t4 57 trim on it tuned pretty well to an 11.8-12.0 afr. So then i picked up a holset HX35 with the 16cm housing and left everything the same as far as boost pressure. The holset is a bit laggier obivously (but not much) but once i got it on, the tune for the t3/t4 was waaay lean. And once i got the holset to an AFR of about 11.8-12.0 and at the same 10psi, the car is noticeably faster and pulls much harder. And i had to add quite a bit of fuel to the map, but kept the same ingnition numbers.
So....
Does that mean that the holset is flowing more air at the same PSI..... more velocity?
02-06-2008, 06:19 PM
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the holset is larger in the turbine and compressor
so yes it is flowing MORE air at the same pressure ratio.
more CFM at the same psi on the large holset is the reason why your running leaner
look at a comp. map even though holset doesnt release their info you can goto bullseye turbo and find out
so yes it is flowing MORE air at the same pressure ratio.
more CFM at the same psi on the large holset is the reason why your running leaner
look at a comp. map even though holset doesnt release their info you can goto bullseye turbo and find out
02-06-2008, 07:13 PM
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Re: (tony413)
The correct question would be : Question about Psi vs CFM
PSI is a static measurement and cfm is a measure of flow
A larger turbo moves more CFM at lower PSI.
For example a 60 trim T04E flows 845 cfm at 15psi and a 76mm unit may do it at 9 psi.
PSI is a static measurement and cfm is a measure of flow
A larger turbo moves more CFM at lower PSI.
For example a 60 trim T04E flows 845 cfm at 15psi and a 76mm unit may do it at 9 psi.
02-06-2008, 07:55 PM
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Re: Question about psi and velocity (a1320honda)
What these other guys are saying has some truth, but it's mostly in the Holset having a bigger turbine and being less of a restriction to the engine's flow. The bigger the turbine/housing the more fuel an engine wants under boost.
02-06-2008, 09:27 PM
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Re: Question about psi and velocity (Joseph Davis)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Joseph Davis »</TD></TR><TR><TD CLASS="quote">What these other guys are saying has some truth, but it's mostly in the Holset having a bigger turbine and being less of a restriction to the engine's flow. The bigger the turbine/housing the more fuel an engine wants under boost.</TD></TR></TABLE>
Joseph, only half the battle. You need a compressor able to flow more air efficiently in order for power to increase. More displacement via the turbine wheel just leaves more room for air in the combustion chamber. You still need the compressor wheel to fill in the volume. Then again, if the compressor wheel couldn't do it's job, he wouldn't make 10psi but some lesser value.
Joseph, only half the battle. You need a compressor able to flow more air efficiently in order for power to increase. More displacement via the turbine wheel just leaves more room for air in the combustion chamber. You still need the compressor wheel to fill in the volume. Then again, if the compressor wheel couldn't do it's job, he wouldn't make 10psi but some lesser value.
02-06-2008, 09:44 PM
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Re: Question about psi and velocity (nowtype)
Yeah, the GT4094R thread I posted in earlier tonight debates the same concepts. Sure it's a balancing act. So is my patience at typing all this stuff out; the OP needs a dissertation but he isn't ready to read one, or else he'd be in the GT4094R thread making salient comments. It's a learning curve; he'll learn something now and be ready for the dissertation later down the road. By that time it'll take a tenth as many words to get the conceots across to him as he's halfway there already. But, I digress.
Turbine size is still the biggest factor, ie why tony1 thinks the GT4094R sucks and why it's only good for a small bump up in power over GT4088R despite having an OMG WTF BBQ GT42!!!!11 compressor. You know it's only half the battle if you don't have a compressor able to flow more air efficiently in order for power to increase, right?
Turbine size is still the biggest factor, ie why tony1 thinks the GT4094R sucks and why it's only good for a small bump up in power over GT4088R despite having an OMG WTF BBQ GT42!!!!11 compressor. You know it's only half the battle if you don't have a compressor able to flow more air efficiently in order for power to increase, right?
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02-07-2008, 09:37 AM
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Re: Question about psi and velocity (a1320honda)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by a1320honda »</TD></TR><TR><TD CLASS="quote">So....
Does that mean that the holset is flowing more air at the same PSI..... more velocity?</TD></TR></TABLE>
If hondas had MAF sensors, it'd be pretty obvious what was happening, I guess. Velocity technically would be accurate, although it's kind of a weird way of looking at it. For a given IM press, you're now moving more airmass, so yeah, I guess if the density (pressure, temp) is the same, then the velocity would be, through the same area..
I'm just curious how much power you can make with the holset though. I have an hx40, but my project car isn't ready for it yet.
Does that mean that the holset is flowing more air at the same PSI..... more velocity?</TD></TR></TABLE>
If hondas had MAF sensors, it'd be pretty obvious what was happening, I guess. Velocity technically would be accurate, although it's kind of a weird way of looking at it. For a given IM press, you're now moving more airmass, so yeah, I guess if the density (pressure, temp) is the same, then the velocity would be, through the same area..
I'm just curious how much power you can make with the holset though. I have an hx40, but my project car isn't ready for it yet.
02-07-2008, 11:27 AM
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You may want to consider pulling a little timing back as well steve or is this before the HG problem??
With the difference in flow you have effectively increased cylinder pressures.
Leaving your previous timing a little on the risky side most likely hard to verify with no load bearing dyno in the area I know but keep an eye on plugs at this point.
With the difference in flow you have effectively increased cylinder pressures.
Leaving your previous timing a little on the risky side most likely hard to verify with no load bearing dyno in the area I know but keep an eye on plugs at this point.
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