 | |  | |  | |  | |  |
Now lets take each requirement and derive a specification for detailed design
purposes.
1) System shall be capable of producing 425HP and 325 ft/lbs
This requirement dictates that the system be capable of producing a specific
amount of air flow in CFM (cubic feet/minute) at a specific rpm. The stock Honda
engine seems to like making its max hp at 7500 - 8000 rpm. This is a
function of the mechanical design of the engine and it's affect on overall VE
(volumetric efficiency) over the entire rpm range. Since were not altering any
internal engine mechanicals, its probably a good idea to build on the stock
powerband. There are many general formulas for calculating this numbers but
these are either too scientific (don't take into account pumping and frictional
losses) or too generic to be useful. A model which has shown to correlate very
accurately uses the stock engine performance as its basis. Simple arithmetic
says that at 8000 rpm and 90% VE that the NSX is consuming approximately
395 CFM to make 250 hp (3.0L). Our goal is 425hp, so well need at least
70% more air (in weight, not just CFM). That means well need a minimum of
675 CFM everything else being equal. Actual boost pressure needed to obtain
this flow is a bit tricker to calculate as air temperature enters the equation, but a
quick scaling would put it at just over 10 psi (14.7 * .7). All of the current crop
of FI options (Turbo, Centrifugal, Positive Displacement) can meet this
requirement if sized correctly.
2) System shall not alter shape of stock powerband and shall produce 90% of said
torque by 3000 rpm (290 ft/lbs).
Since torque generally dictates the overall shape of the powerband, this
requirement can be graphically represented by the stock vs GOAL dyno charts
below. Note: The stock charts were copied from the 2002 NSXPO Dyno Day file.
Again, this requirement dictates that the system be capable of producing a
specific amount of air flow in CFM (cubic feet/minute) at a specific rpm. A stock
3.0 NSX produces about 170 ft/lbs of torque at 3000 rpm. My requirement for
290 ft/lbs of torque at 3000 rpm will require some 240 CFM. This requirement
effectively eliminates the centrifugal SC as it's low speed performance is it's weak
point. On the other hand, it's relatively easy to find a turbo compressor map
that'll support both low speed and high speed flow rates. The problem is the low
speed flow rates depend on the turbine's ability to "spool up" with little heat
energy (exhaust temp and volume). A turbine that spools early typically is too
restrictive from an exhaust flow perspective and will limit the engines VE at high
speed. If you can't get the air out you can't get more air in. This puts the
Turbo option in question as 3000 rpm is below effective spool up on most
systems capable of producing the top end hp numbers needed. If geared
correctly, a PD SCer is the clear winner here as their low speed output is well
documented and easily calculated. (see FI options for more detailed analysis)
3) System shall have all air handling components within engine bay
This requirement is more of a packaging constraint than a performance
requirement. I feel that if the entire front engine world can achieve this than I
should be able to as well. Everything is visible and assessable from the top side
making repair and maintenance easier. In turbo applications, oil return and
reasonable length charge ducting (with IC) are not an issue. Both turbo and PD
systems have been successfully mounted in the engine bays so this is a toss up.
To be specific the following items will need to be in the engine bay:
Air Box, Air box to TB hose, TB, FI pump, FI pump to manifold hose, any
proposed air charge cooler.
4) System shall not require substantial re-location of any major component
Again, more of a packaging constraint, this requirement pretty much puts the
kibosh on the turbo as major re-plumbing of both exhaust and coolant hoses
would be necessary in order to run the turbo inside the engine compartment like
other cars. It's certainly possible and I have a design to accomplish just that,
but it does complicate the installation to the point where a bolt-on "kit" would
be out of the question. A major component would be as follows, Air box, Fuse
box, Overflow bottle, Alternator, Vacuum control box,
5) System shall not significantly block rear view
Another packaging constraint that will need to be address in the detailed
design phase. The requirement needs no elaboration except maybe to specify
that no more than 30% of normal vision shall be disturbed and that there
shall be no affect on rear view mirror line of sight. This constraint does
eliminate the possibility of using a large Air-to-Air intercooler against the back
glass, however.
6) System shall perform reliably with stock bottom end under typical track and
driving conditions using a mechanically sound platform (engine)
a) Track conditions
1) Road race track typical of Willow Springs
2) Ambient conditions 105 degrees F
b) Driving conditions
1) Twenty minutes at 100% (race or TT)
2) 4 hours at 80% (enduro)
These two requirements pretty much dictate that some form of charge air
cooling is employed, particularly at the expected 10 psi boost. In addition, a
piggy back or standalone engine management system will be necessary to
ensure complete freedom in tuning. This will be added insurance that
nothing "funny" will happen that could cause a failure (mechanical or otherwise)
c) Mechanically sound platform
1) Good compression (200 + & +/- 10psi/cyl)
2) Little to no oil consumption
3) Clean combustion chambers (carbon)
4) Good fuel injectors (spray & atomization)
5) Baseline dyno run within stock variability
5) Minimum blowby (as observed on dyno)
7) System shall exhibit "drivability" similar to stock while not under boost
This is a mainly a tuning issue, and therefore lends itself to a good
standalone engine management system.
8) System shall allow access to typical maintenance items
a) Air cleaner
b) Spark plugs
c) Oil filler cap
d) Fuel filter
This is a self explanatory requirement and must be constantly considered
during layout and detailed design
9) SMOG certification is not a requirement
This requirement (or lack of it) allows use of standalones and other
components necessary to meet higher level requirements for power and
reliability
Summary Of main Specifications
o 8000 rpm will need a minimum of 675 CFM
o Just over 10 psi expected
o 3000 rpm will require 240 CFM
o PD SCer is initial design choice due to low rpm torque needed
o Air Box, Air box to TB hose, TB, FI pump, FI pump to manifold hose, any
proposed air charge cooler will be in engine compartment
o Air box, Fuse box, Overflow bottle, Alternator, Vacuum control box, will not be
relocated
o No more than 30% of normal vision will be disturbed and that there
will be no affect on rear view mirror line of sight
o Charge air cooling will be employed
o A standalone engine management system will be employed
o System shall allow access to typical maintenance items
a) Air cleaner
b) Spark plugs
c) Oil filler cap
d) Fuel filter
o SMOG certification is not a concern
purposes.
1) System shall be capable of producing 425HP and 325 ft/lbs
This requirement dictates that the system be capable of producing a specific
amount of air flow in CFM (cubic feet/minute) at a specific rpm. The stock Honda
engine seems to like making its max hp at 7500 - 8000 rpm. This is a
function of the mechanical design of the engine and it's affect on overall VE
(volumetric efficiency) over the entire rpm range. Since were not altering any
internal engine mechanicals, its probably a good idea to build on the stock
powerband. There are many general formulas for calculating this numbers but
these are either too scientific (don't take into account pumping and frictional
losses) or too generic to be useful. A model which has shown to correlate very
accurately uses the stock engine performance as its basis. Simple arithmetic
says that at 8000 rpm and 90% VE that the NSX is consuming approximately
395 CFM to make 250 hp (3.0L). Our goal is 425hp, so well need at least
70% more air (in weight, not just CFM). That means well need a minimum of
675 CFM everything else being equal. Actual boost pressure needed to obtain
this flow is a bit tricker to calculate as air temperature enters the equation, but a
quick scaling would put it at just over 10 psi (14.7 * .7). All of the current crop
of FI options (Turbo, Centrifugal, Positive Displacement) can meet this
requirement if sized correctly.
2) System shall not alter shape of stock powerband and shall produce 90% of said
torque by 3000 rpm (290 ft/lbs).
Since torque generally dictates the overall shape of the powerband, this
requirement can be graphically represented by the stock vs GOAL dyno charts
below. Note: The stock charts were copied from the 2002 NSXPO Dyno Day file.
Again, this requirement dictates that the system be capable of producing a
specific amount of air flow in CFM (cubic feet/minute) at a specific rpm. A stock
3.0 NSX produces about 170 ft/lbs of torque at 3000 rpm. My requirement for
290 ft/lbs of torque at 3000 rpm will require some 240 CFM. This requirement
effectively eliminates the centrifugal SC as it's low speed performance is it's weak
point. On the other hand, it's relatively easy to find a turbo compressor map
that'll support both low speed and high speed flow rates. The problem is the low
speed flow rates depend on the turbine's ability to "spool up" with little heat
energy (exhaust temp and volume). A turbine that spools early typically is too
restrictive from an exhaust flow perspective and will limit the engines VE at high
speed. If you can't get the air out you can't get more air in. This puts the
Turbo option in question as 3000 rpm is below effective spool up on most
systems capable of producing the top end hp numbers needed. If geared
correctly, a PD SCer is the clear winner here as their low speed output is well
documented and easily calculated. (see FI options for more detailed analysis)
3) System shall have all air handling components within engine bay
This requirement is more of a packaging constraint than a performance
requirement. I feel that if the entire front engine world can achieve this than I
should be able to as well. Everything is visible and assessable from the top side
making repair and maintenance easier. In turbo applications, oil return and
reasonable length charge ducting (with IC) are not an issue. Both turbo and PD
systems have been successfully mounted in the engine bays so this is a toss up.
To be specific the following items will need to be in the engine bay:
Air Box, Air box to TB hose, TB, FI pump, FI pump to manifold hose, any
proposed air charge cooler.
4) System shall not require substantial re-location of any major component
Again, more of a packaging constraint, this requirement pretty much puts the
kibosh on the turbo as major re-plumbing of both exhaust and coolant hoses
would be necessary in order to run the turbo inside the engine compartment like
other cars. It's certainly possible and I have a design to accomplish just that,
but it does complicate the installation to the point where a bolt-on "kit" would
be out of the question. A major component would be as follows, Air box, Fuse
box, Overflow bottle, Alternator, Vacuum control box,
5) System shall not significantly block rear view
Another packaging constraint that will need to be address in the detailed
design phase. The requirement needs no elaboration except maybe to specify
that no more than 30% of normal vision shall be disturbed and that there
shall be no affect on rear view mirror line of sight. This constraint does
eliminate the possibility of using a large Air-to-Air intercooler against the back
glass, however.
6) System shall perform reliably with stock bottom end under typical track and
driving conditions using a mechanically sound platform (engine)
a) Track conditions
1) Road race track typical of Willow Springs
2) Ambient conditions 105 degrees F
b) Driving conditions
1) Twenty minutes at 100% (race or TT)
2) 4 hours at 80% (enduro)
These two requirements pretty much dictate that some form of charge air
cooling is employed, particularly at the expected 10 psi boost. In addition, a
piggy back or standalone engine management system will be necessary to
ensure complete freedom in tuning. This will be added insurance that
nothing "funny" will happen that could cause a failure (mechanical or otherwise)
c) Mechanically sound platform
1) Good compression (200 + & +/- 10psi/cyl)
2) Little to no oil consumption
3) Clean combustion chambers (carbon)
4) Good fuel injectors (spray & atomization)
5) Baseline dyno run within stock variability
5) Minimum blowby (as observed on dyno)
7) System shall exhibit "drivability" similar to stock while not under boost
This is a mainly a tuning issue, and therefore lends itself to a good
standalone engine management system.
8) System shall allow access to typical maintenance items
a) Air cleaner
b) Spark plugs
c) Oil filler cap
d) Fuel filter
This is a self explanatory requirement and must be constantly considered
during layout and detailed design
9) SMOG certification is not a requirement
This requirement (or lack of it) allows use of standalones and other
components necessary to meet higher level requirements for power and
reliability
Summary Of main Specifications
o 8000 rpm will need a minimum of 675 CFM
o Just over 10 psi expected
o 3000 rpm will require 240 CFM
o PD SCer is initial design choice due to low rpm torque needed
o Air Box, Air box to TB hose, TB, FI pump, FI pump to manifold hose, any
proposed air charge cooler will be in engine compartment
o Air box, Fuse box, Overflow bottle, Alternator, Vacuum control box, will not be
relocated
o No more than 30% of normal vision will be disturbed and that there
will be no affect on rear view mirror line of sight
o Charge air cooling will be employed
o A standalone engine management system will be employed
o System shall allow access to typical maintenance items
a) Air cleaner
b) Spark plugs
c) Oil filler cap
d) Fuel filter
o SMOG certification is not a concern
Design Specifications
