New Whipple 2.9L compressor, 175AX
10-22-2008, 05:09 AM
#42
One more thing before I run off for the evening, meant to mention...
BELT SLIPPAGE
Do you find belt dust stuck to the front of the supercharger? I used to run a 2.5" pulley on the smallblock with at least 30 degrees more of belt wrap around the pulley than the 8100 kit gets and had belt-slippage problems from hell most of the time.
Slipping belt goes a long way to explain less-than-expected boost levels.
BELT SLIPPAGE
Do you find belt dust stuck to the front of the supercharger? I used to run a 2.5" pulley on the smallblock with at least 30 degrees more of belt wrap around the pulley than the 8100 kit gets and had belt-slippage problems from hell most of the time.
Slipping belt goes a long way to explain less-than-expected boost levels.
10-22-2008, 05:21 AM
#43
Looks like the 8100's most efficient RPM is at about 3800. We'll use 4000 at 100kPa since that has the highest peak VE. (Sea-level air pressure is actually a little over 101kPa) That can be rounded to 89% efficient.
8100cc devided by 2 since a 4-stroke is 4050cc per rotation at 100% VE, so multiplied by 89 = about 3600cc per rev of air going in assuming 1 atmosphere in the manifold. (Actual kPa in the manifold during WOT you'll find will be less, between 90-95, but forget about that for now.)
Now go back to the other data we know and can presume. We know the pulley setup is spinning the blower 3.16 times faster, so about 12500 is close enough for blower input RPM @ 4000 engine RPM. We know the manifold was seeing 7psi boost at best. (100kPa = 14.5psi) 7 psi of boost is about 150kPa, or 1.5 bar. There's no VE number for that value but plotting a curve using existing numbers we can presume it's about the 91%. (If the VE table continued on based on real flow data you'd see it almost levels off rising less and less with each subsequent column of kPa.) Multiply the 4050cc at 100kPa conveniently by 1.50 for 7psi (50kPa) boost, multiply by 91% and 5500cc of air pumped per revolution at 4000RPM with 7psi boost. Multiply that by itself.
5500cc x 4000RPM = 22,000,000 cubic centimeters (22 cubic meters) per minute.
Now go to the chart for the 2300 compressor. (Keep in mind that is a Lysholm map and not a Whipple map which is why I'm rounding everything anyway here for clarity. The Whipple designed compressor is more efficient slightly.)
Look up 22 m3/min. Chart says the needed blower RPM should only be between 10,000 and 10,500RPM, (depending on backpressure) in other words about a 2.7/8" pulley. Because air volume is measured at the inlet, pressure is constant regardless of the outlet pressure.
10,500 suggested RPM versus 12,600RPM. Why the 20% difference? 5% error factors in data and 15% RESRICTION!
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You want to know how big of a blower and what pulley for the boost you need.
How about 10psi. It's a big block with intercooler. 10psi would be fun. We'll say 170kPa. To find maximum requirements use the maximum engine RPM. I will use 4800RPM since I know an 8.1L stock can't do more than that.
VE is less at 4800 then at 4000 by about 4 points, so I will use 87% VE. 4050 x 87% x 1.70 (kPa divided by 100) = 5990cc x 4800RPM = 28.75 cubic meters per minute. Call it 29 just for good measure. At a 1.8x pressure differential a 2.3L supercharger at 4800 engine RPM with absolutely no inlet restrictions would need to be turning 14000RPM and need about a 2.5" pulley. Factor in the restrictions int he real world and you're off that chart just like that. Note how far to the right of the blower's sweet spot that is. The 2.3L compressor most efficiently turns torque into boost around 8000 RPM, according to Lysholm's chart.
Now check out a 1.8x pressure differential at 29 cubic meters per minute with the 3.3L compressor. Only 9500 RPM! (at 100% no restriction) Factor in the 20% error and restriction and you're still only at 11,400RPM for the blower at 4800 Engine RPM, and that's about a 3.1/8" pulley. Remember I said a 3" 6-rib is about minimum pulley size for a 3300cc compressor?
How's that
Tired... will fix typos tomorrow
8100cc devided by 2 since a 4-stroke is 4050cc per rotation at 100% VE, so multiplied by 89 = about 3600cc per rev of air going in assuming 1 atmosphere in the manifold. (Actual kPa in the manifold during WOT you'll find will be less, between 90-95, but forget about that for now.)
Now go back to the other data we know and can presume. We know the pulley setup is spinning the blower 3.16 times faster, so about 12500 is close enough for blower input RPM @ 4000 engine RPM. We know the manifold was seeing 7psi boost at best. (100kPa = 14.5psi) 7 psi of boost is about 150kPa, or 1.5 bar. There's no VE number for that value but plotting a curve using existing numbers we can presume it's about the 91%. (If the VE table continued on based on real flow data you'd see it almost levels off rising less and less with each subsequent column of kPa.) Multiply the 4050cc at 100kPa conveniently by 1.50 for 7psi (50kPa) boost, multiply by 91% and 5500cc of air pumped per revolution at 4000RPM with 7psi boost. Multiply that by itself.
5500cc x 4000RPM = 22,000,000 cubic centimeters (22 cubic meters) per minute.
Now go to the chart for the 2300 compressor. (Keep in mind that is a Lysholm map and not a Whipple map which is why I'm rounding everything anyway here for clarity. The Whipple designed compressor is more efficient slightly.)
Look up 22 m3/min. Chart says the needed blower RPM should only be between 10,000 and 10,500RPM, (depending on backpressure) in other words about a 2.7/8" pulley. Because air volume is measured at the inlet, pressure is constant regardless of the outlet pressure.
10,500 suggested RPM versus 12,600RPM. Why the 20% difference? 5% error factors in data and 15% RESRICTION!
----------------
You want to know how big of a blower and what pulley for the boost you need.
How about 10psi. It's a big block with intercooler. 10psi would be fun. We'll say 170kPa. To find maximum requirements use the maximum engine RPM. I will use 4800RPM since I know an 8.1L stock can't do more than that.
VE is less at 4800 then at 4000 by about 4 points, so I will use 87% VE. 4050 x 87% x 1.70 (kPa divided by 100) = 5990cc x 4800RPM = 28.75 cubic meters per minute. Call it 29 just for good measure. At a 1.8x pressure differential a 2.3L supercharger at 4800 engine RPM with absolutely no inlet restrictions would need to be turning 14000RPM and need about a 2.5" pulley. Factor in the restrictions int he real world and you're off that chart just like that. Note how far to the right of the blower's sweet spot that is. The 2.3L compressor most efficiently turns torque into boost around 8000 RPM, according to Lysholm's chart.
Now check out a 1.8x pressure differential at 29 cubic meters per minute with the 3.3L compressor. Only 9500 RPM! (at 100% no restriction) Factor in the 20% error and restriction and you're still only at 11,400RPM for the blower at 4800 Engine RPM, and that's about a 3.1/8" pulley. Remember I said a 3" 6-rib is about minimum pulley size for a 3300cc compressor?
How's that
Tired... will fix typos tomorrow
Okay, I am following you for the most part i think. SO in a perfect world, i could assume that at a pressure ratio of 1.7 x 22m3/m....i should be seeing about 1.5 bar or 7psi above atmospheric? Correct?
I understand the 5% error aspect...but a 15% restriction? Where is that 15%? Is it a combination of intercooler and intake?
10-23-2008, 11:32 AM
#46
Jeff from Whipple finally got back to me.....i just dont think we are on the same page. Here is a C&P of the Email
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From: Me
To: michael@whipplesuperchargers.com
Cc: jeff@whipplesuperchargers.com
Sent: Saturday, October 18, 2008 7:13 PM
Subject: New 2.9L compressor questions
Hey Mike, this is Jimmie W. I bought the 8.1L intercooler Kit from you a year or so ago and bought the 8.1L supercharger kit from Chris Garcia before you worked there. I am still enjoying the blower setup but have ran into one minor problem.......I cant seem to get anymore than 6.5lbs of boost out of this combo. I am currently running the 2-3/8" pulley, but have found that the 2-3/8, 2.5", and 2-5/8" pulley's all give me the same amount of boost....right around 6.5lbs or 145kPa. I think the 2.3L compressor is just not large enough to supply this 8.1L with enough air to boost it beyond that point.
Unless you or Jeff can think of anything that might be going on, I was wondering if either of you could tell me if there is a way to make the new 175AX or 200AX compressor work on my setup? It looks like the 175AX is a little longer and the bottom mounting plate is a little different but other than that they look like the same casing. I would love to get a little bigger compressor behind this engine but need some help or suggestions in doing so. I know you guys do a lot of work for the 496 MAG boat engines and this is essentially the same motor, so I figured you might have a few ideas up your sleeves. Can either of you guys help me out...PLEASE!!
From: michael@whipplesuperchargers.com
To: gable74@hotmail.com
CC: jeff@whipplesuperchargers.com
Subject: Re: New 2.9L compressor questions
Date: Mon, 20 Oct 2008 08:43:07 -0700
The W175AX (2.9L) is not available as of yet. We use the same W140AX on the 496 MAG marine kits as well. The 2.9 will not fit as it is too long and will run into the firewall. This may not be a compressor issue though. Jeff will talk to you more about that.
From: Me
To: michael@whipplesuperchargers.com
CC: jeff@whipplesuperchargers.com
Subject: RE: New 2.9L compressor questions
Date: Mon, 20 Oct 2008 11:53:42 -0400
Really? Doing the math it seems like the potential of the W140AX is maxed out even on the 454 let alone the 496. To even get 6lbs of boost out of the intercooled 8.1L setup it requires a 2-5/8" pulley which im sure you know is WAY small and prone to belt slip especially with a 6 rib belt. I would still love to try to get the 3.3L to work though if i could get availability to a blown up unit or empty case to use for a mock-up test fit before actually buying the compressor. I am very interested in hearing what Jeff has to say about it though.....if he can find a solution that doesnt require an upgrade that would be great!
From:Jeff Tiller (jeff@whipplesuperchargers.com)
Sent:Wed 10/22/08 4:22 PMTo: ME
Have you called about this problem before if so did we make a case number ?
We have customers with built up ford cobras making 650 hp with this compressor I really doubt its too small for a stock 8.1
unless you have a modified engine or your at a high elevation it should be able to make 7-8 lb with the regular pulley
No other compressor we have will bolt right on the chev 8.1 kit the 2.9 is longer and there is barely enough room behind the 2.3
as it is. The extra length would have to go forward which would require a totally different belt system
the blower would need to have its own belt crank pulley and tensioner system in front of the existing stock belt loop
Its really strange that with different pullies its always the reaching the same boost
boost should increase and decrease proportionally to the rpm you turn the blower
it sounds almost like something is slipping
I did have a guy once with a slipping belt that was not able to go over a certain amount of boost
I also had one that had a leaking air hose that leaked boost out above a certain pressure one of the clamps had broken on the intercooler
but it was still in place and looked ok
I wonder if the pulley hub could slip ?
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From: Me
To: michael@whipplesuperchargers.com
Cc: jeff@whipplesuperchargers.com
Sent: Saturday, October 18, 2008 7:13 PM
Subject: New 2.9L compressor questions
Hey Mike, this is Jimmie W. I bought the 8.1L intercooler Kit from you a year or so ago and bought the 8.1L supercharger kit from Chris Garcia before you worked there. I am still enjoying the blower setup but have ran into one minor problem.......I cant seem to get anymore than 6.5lbs of boost out of this combo. I am currently running the 2-3/8" pulley, but have found that the 2-3/8, 2.5", and 2-5/8" pulley's all give me the same amount of boost....right around 6.5lbs or 145kPa. I think the 2.3L compressor is just not large enough to supply this 8.1L with enough air to boost it beyond that point.
Unless you or Jeff can think of anything that might be going on, I was wondering if either of you could tell me if there is a way to make the new 175AX or 200AX compressor work on my setup? It looks like the 175AX is a little longer and the bottom mounting plate is a little different but other than that they look like the same casing. I would love to get a little bigger compressor behind this engine but need some help or suggestions in doing so. I know you guys do a lot of work for the 496 MAG boat engines and this is essentially the same motor, so I figured you might have a few ideas up your sleeves. Can either of you guys help me out...PLEASE!!
From: michael@whipplesuperchargers.com
To: gable74@hotmail.com
CC: jeff@whipplesuperchargers.com
Subject: Re: New 2.9L compressor questions
Date: Mon, 20 Oct 2008 08:43:07 -0700
The W175AX (2.9L) is not available as of yet. We use the same W140AX on the 496 MAG marine kits as well. The 2.9 will not fit as it is too long and will run into the firewall. This may not be a compressor issue though. Jeff will talk to you more about that.
From: Me
To: michael@whipplesuperchargers.com
CC: jeff@whipplesuperchargers.com
Subject: RE: New 2.9L compressor questions
Date: Mon, 20 Oct 2008 11:53:42 -0400
Really? Doing the math it seems like the potential of the W140AX is maxed out even on the 454 let alone the 496. To even get 6lbs of boost out of the intercooled 8.1L setup it requires a 2-5/8" pulley which im sure you know is WAY small and prone to belt slip especially with a 6 rib belt. I would still love to try to get the 3.3L to work though if i could get availability to a blown up unit or empty case to use for a mock-up test fit before actually buying the compressor. I am very interested in hearing what Jeff has to say about it though.....if he can find a solution that doesnt require an upgrade that would be great!
From:Jeff Tiller (jeff@whipplesuperchargers.com)
Sent:Wed 10/22/08 4:22 PMTo: ME
Have you called about this problem before if so did we make a case number ?
We have customers with built up ford cobras making 650 hp with this compressor I really doubt its too small for a stock 8.1
unless you have a modified engine or your at a high elevation it should be able to make 7-8 lb with the regular pulley
No other compressor we have will bolt right on the chev 8.1 kit the 2.9 is longer and there is barely enough room behind the 2.3
as it is. The extra length would have to go forward which would require a totally different belt system
the blower would need to have its own belt crank pulley and tensioner system in front of the existing stock belt loop
Its really strange that with different pullies its always the reaching the same boost
boost should increase and decrease proportionally to the rpm you turn the blower
it sounds almost like something is slipping
I did have a guy once with a slipping belt that was not able to go over a certain amount of boost
I also had one that had a leaking air hose that leaked boost out above a certain pressure one of the clamps had broken on the intercooler
but it was still in place and looked ok
I wonder if the pulley hub could slip ?
10-23-2008, 01:08 PM
#47
I know Michael. He's helpful and usually quick to reply to email.
I see some discussion here about belt re-routing. The only way I see to do that would be to piggy-back another crank pulley on in front of the existing one. I cannot recommend doing that. A belt under that much torque that far out from the end of the crank snout is going to put a lot of fatigue load on the crank. Even though BBC cranks are massive compared to everything else, I think that would result in a broken crank snout for a daily driver.
I see some discussion here about belt re-routing. The only way I see to do that would be to piggy-back another crank pulley on in front of the existing one. I cannot recommend doing that. A belt under that much torque that far out from the end of the crank snout is going to put a lot of fatigue load on the crank. Even though BBC cranks are massive compared to everything else, I think that would result in a broken crank snout for a daily driver.
10-24-2008, 01:21 AM
#50
Had another thought on your situation today.
All this time we've been talking about rear-inlet compressors. Whipple makes a version of the 3.3L with a top inlet with a carburetor bolt pattern - the "200R". The easy bolt pattern will make it a lot easier to custom-make an inlet elbow for your application. Since you're MAF-less anyway it might be possible to run an inlet forward and mount the TB on the driver side with an open element filter. (Intercooler and pulley size can make up for the underhood heat as long as the radiator up front is large enough to do the job.) Even though the top inlet is not as efficient as the back inlet, I think that this would solve the rear clearance problem easily. The 3.3L compressor is 2" longer than the 2.3L compressor. There are a few companies making intake elbows for the aftermarket carb-flanged Gen-III/IV smallblock manifolds, there might be a low-profile one available that can be made to work. Whatever the design it does appear that it will need to be very low to fit under the hood.
http://www.whipplesuperchargers.com/...dimensions.pdf
All this time we've been talking about rear-inlet compressors. Whipple makes a version of the 3.3L with a top inlet with a carburetor bolt pattern - the "200R". The easy bolt pattern will make it a lot easier to custom-make an inlet elbow for your application. Since you're MAF-less anyway it might be possible to run an inlet forward and mount the TB on the driver side with an open element filter. (Intercooler and pulley size can make up for the underhood heat as long as the radiator up front is large enough to do the job.) Even though the top inlet is not as efficient as the back inlet, I think that this would solve the rear clearance problem easily. The 3.3L compressor is 2" longer than the 2.3L compressor. There are a few companies making intake elbows for the aftermarket carb-flanged Gen-III/IV smallblock manifolds, there might be a low-profile one available that can be made to work. Whatever the design it does appear that it will need to be very low to fit under the hood.
http://www.whipplesuperchargers.com/...dimensions.pdf