Is there a best bonnet design?
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The best ones are
a) NACA ducts, designed during the NASA space program. Zero drag loss, maximum throughput. Used firstly on Lamborghini Espadea and Jarama's in the late 60's, then on domestic Torino's and Aussie Falcon Hardtops.,
The Fat Mustang had a more restictive version which was copied on to Falcons in Australia, and is actually one of the better compromises around.
http://www.max-boost.co.uk/max-boost/images/mustang_scoops.jpg
b) Chevy L88 Cowl Induction...focuses on high pressure area at base of windscreen, where the air is forced into the base of the hood with vey little drag loss. It does spoil the cool air circulation at the cowl, and increases engine noise.
c) Holden L34/L31/A9X Reverse scoop.
a) NACA ducts, designed during the NASA space program. Zero drag loss, maximum throughput. Used firstly on Lamborghini Espadea and Jarama's in the late 60's, then on domestic Torino's and Aussie Falcon Hardtops.,
The Fat Mustang had a more restictive version which was copied on to Falcons in Australia, and is actually one of the better compromises around.
http://www.max-boost.co.uk/max-boost/images/mustang_scoops.jpg
b) Chevy L88 Cowl Induction...focuses on high pressure area at base of windscreen, where the air is forced into the base of the hood with vey little drag loss. It does spoil the cool air circulation at the cowl, and increases engine noise.
c) Holden L34/L31/A9X Reverse scoop.
what a classic moment....
Just when you think I'm thick and can't read properly, I go and ....
totally redeam myself!
Bonnet on top of carb.
Best one is one which has
1) a flow developed chamber which allows the slowing air to bank up, increasing pressure at the carburettor mouth for added power.
2) An inertial tuned length to suit the rpm range of the engine.
3) a flared entry point at the end to a high flow air filter.
Length can only be varified by a chassi dyno or by very dilligent work with a G-analyst on an agreate of steep constant 8 to 12% road and a set-up 1/8 mile on a safe country road. You take five runs in second gear acceleration from 30 to 50 mph, take the time with a 4" ram tube and filter, then hop out, add 12 inches of pipe bend to the ram tube (making 16 iches total).
Then take another five 30 to 50 readings. Then you do 3 1/8 mile runs with the extra long 16" pipe, and finish with 3 runs with the 4" inch total length pipe.
This is called making a suite of power and torque curves so you can trade off and find the ideal ram tube length.
What happens is the long pipe increases low end torque whilr loosing power at the high end. The short pipe should gain high end power, but loose toque at the low end. The right pipe lenght is the one which yields the best gain in 30 to 50 mph acceleration, with the least loss in standing 1/8 mile time.
Most flow developed chamber s and ram tubes will loose about 3.5% of the CFM of a bare carb with no air cleaner, but yields a huge increase in mid range power with no loss in peak power. 95% of the time, mid range torque is what you need.
The engine life will increase because the engine will have better filtration, use less throttle opening for a given cruise speed or rate of acceleration, thus the fuel economy will also improve. High end power will improve compared to most other air cleaners you could use, but be behind the very best K&N fliter.
Its nothing for stock air cleaners to loose 15 to 20% of the bare flow in CFM that a carb has. So a 227 cfm Holley Weber from a Pinto, Capri or Clifford or Stovebolt may only see 195 cfm with the air cleaner on.
With a K&N filter, that may be 235 cfm. With a K&N flow chamber and remote K&N air filter, there may be less than 220 cfm, but it will make a lot of extra power.
An example? Mraley's yellow Mustang.
His 200/2V head combo produces more power than a car with a 350 cfm Holley ever should.
The other option is the bonnet Does10'S uses.
see http://fordsix.com/forum/profile.php?mo ... ile&u=1328
It is likely to do a similar job a little more cheaply, but its primarily for a turbo engine.
One thing is that it is wrong to focus on just peak air flow. To work well, the three fetures above must be present.
totally redeam myself!
Bonnet on top of carb.
Best one is one which has
1) a flow developed chamber which allows the slowing air to bank up, increasing pressure at the carburettor mouth for added power.
2) An inertial tuned length to suit the rpm range of the engine.
3) a flared entry point at the end to a high flow air filter.
Length can only be varified by a chassi dyno or by very dilligent work with a G-analyst on an agreate of steep constant 8 to 12% road and a set-up 1/8 mile on a safe country road. You take five runs in second gear acceleration from 30 to 50 mph, take the time with a 4" ram tube and filter, then hop out, add 12 inches of pipe bend to the ram tube (making 16 iches total).
Then take another five 30 to 50 readings. Then you do 3 1/8 mile runs with the extra long 16" pipe, and finish with 3 runs with the 4" inch total length pipe.
This is called making a suite of power and torque curves so you can trade off and find the ideal ram tube length.
What happens is the long pipe increases low end torque whilr loosing power at the high end. The short pipe should gain high end power, but loose toque at the low end. The right pipe lenght is the one which yields the best gain in 30 to 50 mph acceleration, with the least loss in standing 1/8 mile time.
Most flow developed chamber s and ram tubes will loose about 3.5% of the CFM of a bare carb with no air cleaner, but yields a huge increase in mid range power with no loss in peak power. 95% of the time, mid range torque is what you need.
The engine life will increase because the engine will have better filtration, use less throttle opening for a given cruise speed or rate of acceleration, thus the fuel economy will also improve. High end power will improve compared to most other air cleaners you could use, but be behind the very best K&N fliter.
Its nothing for stock air cleaners to loose 15 to 20% of the bare flow in CFM that a carb has. So a 227 cfm Holley Weber from a Pinto, Capri or Clifford or Stovebolt may only see 195 cfm with the air cleaner on.
With a K&N filter, that may be 235 cfm. With a K&N flow chamber and remote K&N air filter, there may be less than 220 cfm, but it will make a lot of extra power.
An example? Mraley's yellow Mustang.
His 200/2V head combo produces more power than a car with a 350 cfm Holley ever should.
The other option is the bonnet Does10'S uses.
see http://fordsix.com/forum/profile.php?mo ... ile&u=1328
It is likely to do a similar job a little more cheaply, but its primarily for a turbo engine.
One thing is that it is wrong to focus on just peak air flow. To work well, the three fetures above must be present.
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