A little progress...
06-13-07, 07:53 AM
#135
Newb Photog
Join Date: Jul 2001
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HA HA, WOW!!!
Trying to get back on subject, I see here there appears to be enough room for between the carb style intake and the motor to do what you wanted Jim, but will it hit any of the accessories or piping?:
Trying to get back on subject, I see here there appears to be enough room for between the carb style intake and the motor to do what you wanted Jim, but will it hit any of the accessories or piping?:
06-13-07, 08:12 AM
#136
Pretty, yes. But it's a roots, and as we all know, roots blowers suck. 
Perhaps suck isn't the right term, but they aren't very good at blowing, at least not efficiently. They're the cheap ***** version of blowers, if you want blown properly, you have to spend a little more.
Barban,
Anyone with a brain knows that Jim's car will run eventually, he just needs some 30 weight ritalin, since he seems to have a touch of drivetrain ADD.
Jim,
That intake should be great all finished up. Are you extending the runners into the plenum box at all, or just foregoing concern on that, since you're blowing on it anyway?
Perhaps suck isn't the right term, but they aren't very good at blowing, at least not efficiently. They're the cheap ***** version of blowers, if you want blown properly, you have to spend a little more. Barban,
Anyone with a brain knows that Jim's car will run eventually, he just needs some 30 weight ritalin, since he seems to have a touch of drivetrain ADD.
Jim,
That intake should be great all finished up. Are you extending the runners into the plenum box at all, or just foregoing concern on that, since you're blowing on it anyway?
06-13-07, 12:30 PM
#137
Super Snuggles
Thread Starter
06-14-07, 12:57 PM
#139
Super Snuggles
Thread Starter
That's a negative Ghost Rider, and it still made over 400 lb-ft. of torque at 2,000 rpm.
Interestingly enough, I did a quick head flow comparison of the L92 heads as-cast (~$800) to my AFR 215RRs (~$4,500 if you exclude my Ti valves). Keep in mind that the AFRs are 23-degree heads while the L92s are 15-degree heads, so the L92s should have exceptional stock flow numbers, but wow. Look at the low lift numbers on the L92s, not to mention what a value they are.
Bold blue indicates the higher value, both were measured at 28.0" of H2O.
Interestingly enough, I did a quick head flow comparison of the L92 heads as-cast (~$800) to my AFR 215RRs (~$4,500 if you exclude my Ti valves). Keep in mind that the AFRs are 23-degree heads while the L92s are 15-degree heads, so the L92s should have exceptional stock flow numbers, but wow. Look at the low lift numbers on the L92s, not to mention what a value they are.
Bold blue indicates the higher value, both were measured at 28.0" of H2O.
06-14-07, 02:31 PM
#141
Super Snuggles
Thread Starter
It should be. It only saw a few dyno pulls.
From what I understand, GM didn't leave a lot on the table with the L92s. People who have ported them haven't gained much, and I don't plan to touch mine, beyond possibly replacing the springs. They truly are an exceptional out-of-the-box head for the money, but they don't have a lot of upward potential (not that they really need it).
If you want a head that can be ported to exceed 360 cfm (on the intake), then you can start with LS7 castings, but at $930 ea. bare (PN 12578450), you're going to pay to reach that level, and it would really only benefit maximum effort naturally aspirated and/or larger displacement motors. You can shove plenty of air through the L92s as-cast with forced induction and make more than enough power for a street car.
Most of the benefit of porting the heads would be in the high lift area anyway. Low lift numbers would almost certainly suffer to some degree (look at my AFRs in the 0.2-0.4" range), and since the valve passes through the low lift range twice on each cycle, low lift is very important for a street engine. An easy way to compare the "streetability" of two different heads is to "flow index" them using the formula below which is weighted towards low lift values and produces an average value for comparison. A higher value is better.
Flow index = ((cfm @ 0.3" lift * 4) + (cfm @ 0.4" lift * 2) + (cfm @ 0.5" lift)) / 7
L92 = ((225.3 * 4) + (274.6 * 2) + (308.8) / 7)) = 251.3
AFR = ((193.1 * 4) + (256.5 * 2) + (297.5) / 7)) = 226.1
For naturally aspirated engines, you can also estimate maximum potential power by using this formula...
Potential power = max. intake flow * 0.257 * # cylinders
L92 = 328.7 * 0.257 * 8 = 675.8
AFR = 332.0 * 0.257 * 8 = 682.6
Not much difference, which shows you just how far cylinder head technology has advanced in just the last 5 years.
Will you lose anything if you port the L92 heads (lower end)?
If you want a head that can be ported to exceed 360 cfm (on the intake), then you can start with LS7 castings, but at $930 ea. bare (PN 12578450), you're going to pay to reach that level, and it would really only benefit maximum effort naturally aspirated and/or larger displacement motors. You can shove plenty of air through the L92s as-cast with forced induction and make more than enough power for a street car.
Most of the benefit of porting the heads would be in the high lift area anyway. Low lift numbers would almost certainly suffer to some degree (look at my AFRs in the 0.2-0.4" range), and since the valve passes through the low lift range twice on each cycle, low lift is very important for a street engine. An easy way to compare the "streetability" of two different heads is to "flow index" them using the formula below which is weighted towards low lift values and produces an average value for comparison. A higher value is better.
Flow index = ((cfm @ 0.3" lift * 4) + (cfm @ 0.4" lift * 2) + (cfm @ 0.5" lift)) / 7
L92 = ((225.3 * 4) + (274.6 * 2) + (308.8) / 7)) = 251.3
AFR = ((193.1 * 4) + (256.5 * 2) + (297.5) / 7)) = 226.1
For naturally aspirated engines, you can also estimate maximum potential power by using this formula...
Potential power = max. intake flow * 0.257 * # cylinders
L92 = 328.7 * 0.257 * 8 = 675.8
AFR = 332.0 * 0.257 * 8 = 682.6
Not much difference, which shows you just how far cylinder head technology has advanced in just the last 5 years.
06-14-07, 02:57 PM
#142
HAHAHAHAH, i nearly pissed my pants when I read this. There was some gophering going on at the Cube Farm trying to figure out why I was laughing.
anywho, great to see you're back working on the FD. I agree that you need some driveline ritalin (sp?), but i love how you're not going to "just get it running to get it running," you're making it how you want it.
Do you think this is going to be your last driveline combination? Any plans to set a goal to get it back on the road?
06-14-07, 05:16 PM
#143
Super Snuggles
Thread Starter
For this car? I hope so.
Not really. I'm just trying to get things moving along for other people at the moment, since I'm holding up their projects too. 
Any plans to set a goal to get it back on the road?
06-14-07, 07:22 PM
#146
Displacement > Boost
Join Date: Oct 2002
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Pretty, yes. But it's a roots, and as we all know, roots blowers suck. Perhaps suck isn't the right term, but they aren't very good at blowing, at least not efficiently. They're the cheap ***** version of blowers, if you want blown properly, you have to spend a little more.
Perhaps suck isn't the right term, but they aren't very good at blowing, at least not efficiently. They're the cheap ***** version of blowers, if you want blown properly, you have to spend a little more.
06-14-07, 08:04 PM
#148
Super Snuggles
Thread Starter
06-14-07, 08:23 PM
#149
Super Snuggles
Thread Starter
Well, to be accurate, the Eaton/Magnuson blower isn't exactly a Roots blower, but it is a Roots-style blower. The difference is that each rotor has been twisted 60 degrees to form a helix, so these are often referred to as "twin-screw" or "hybrid-Roots" blowers (the Lysholm blower also falls into this category).
Twin-screw blowers compress air between the rotors whereas a Roots blower does not; the compression actually takes place in the manifold. Because the compression is done inside the supercharger, twin-screw blowers produce less heat than a Roots supercharger. In fact, they are almost as thermally efficient as a centrifugal design. Also, because the tolerances between the rotating screws are very tight, they have the ability to create boost at low rpms... unlike a Roots blower. And finally, the rotors do not touch in a twin-screw blower, unlik a Roots blower, so there is virtually no wear involved and they are much more reliable.
However, one disadvantage of the twin screw design is that because it has an internal compression ratio, the twin screw is compressing air even when it is not sending boost to the engine (i.e. while cruising or under deceleration). An internal bypass valve releases the pressurized air, but because it takes work to pressurize the air in the first place, the twin screw supercharger draws more power from the engine than a Roots blower while not under boost.
And while we're on the subject, Magnuson has this great "blueprint", which shows the height and belt spacing of their low-profile Gen III and Gen IV blower... which proves that it won't fit under a stock FD hood.
http://www.magnusonproducts.com/imag...-CAMARO-TR.jpg
Twin-screw blowers compress air between the rotors whereas a Roots blower does not; the compression actually takes place in the manifold. Because the compression is done inside the supercharger, twin-screw blowers produce less heat than a Roots supercharger. In fact, they are almost as thermally efficient as a centrifugal design. Also, because the tolerances between the rotating screws are very tight, they have the ability to create boost at low rpms... unlike a Roots blower. And finally, the rotors do not touch in a twin-screw blower, unlik a Roots blower, so there is virtually no wear involved and they are much more reliable.
However, one disadvantage of the twin screw design is that because it has an internal compression ratio, the twin screw is compressing air even when it is not sending boost to the engine (i.e. while cruising or under deceleration). An internal bypass valve releases the pressurized air, but because it takes work to pressurize the air in the first place, the twin screw supercharger draws more power from the engine than a Roots blower while not under boost.
And while we're on the subject, Magnuson has this great "blueprint", which shows the height and belt spacing of their low-profile Gen III and Gen IV blower... which proves that it won't fit under a stock FD hood.
http://www.magnusonproducts.com/imag...-CAMARO-TR.jpg