acura nsx twin turbocharger

ACURA
NSX
TWIN TURBOCHARGER
The ACURA NSXTWINTURBOSYSTEM
from the Bell Engineering Group, Inc. (BEGI) brings to the NSX
performance enthusiast a whole new dimension of engineering, sophistication and value,
The perceptive/demanding
buyer will be asking questions about the depth of engineering,
experience and quality of design prior to deciding if the system meets his/her needs. This
document is an overview of those questions and the engineering involved.
If one is not an expert in the facets of turbocharging and other performance systems, a guide
to what aspects of these systems to look for and their respective significance is a handy tool.
For example, a water injector is a disastrous part and fuel controls are crucial. This paper can
offer some degree of guidance on those matters.
Any given performance system has several areas that need inspection before a judgement can
be rendered as to the quality of its design. These individual areas are: power, safety, response,
quality, fun, economy, durability, and price. These items are discussed in the following pages.
There are key features that create power safely. These features are critical to the long term
reliability of a turbo/supercharger
system and more importantly, its host engine. It isessential that
the prospective buyer examine these features of any performance system before determining
that a particular system meets his/her long term requirements.
The three features that must be under absolute control at all times are:
1. Temperature of the air entering the engine. "The
charge temperature"
2. Correct air fuel ratio under all operational
conditions.
3. Margin of safety on knock (ping, detonation).
WHY THETURBO
Turbo machinery science has advanced to a performance and durability level approximately
30 years ahead of any form of supercharging. This is reflected in many areas; there are 96 turbo
engine vehicles in production today, there are only three supercharged vehicles. The slowest
ten turbo vehicles average faster than all the supercharged
vehicles. No major road race
anywhere in the world has been won by a supercharged
vehicle in the past 38 years.
Turbocharged vehicles have won perhaps 5000 races in that period of time.
CHARGE COOLING
Heat makes detonation and detonation leads to engine damage.
is one of the most urgent requirements of a successful system.
Therefore, charge
An example of requirement number one can best be illustrated by comparing
with the Paxton and Vortech based supercharger systems.
BELL
ENGINEERING
GROUP,
cooling
our turbosystem
INC.
Legal for sale or use in California only on racing vehicles whi::h may never be used upon a highway
ECONOMY
.,
Although perhaps of lesser'importance, any turbosystem will effect economy less than any
supercharger system. The supercharger system suffers the power loss of always driving the
blower, even when boost is not wanted. Thislossis called a parasitic loss.The new turbo in the
Bell Engineering system has the interesting characteristic of far lessback pressure in the exhaust
than any other turbo. The Bell Engineering system will thus have the least effect on economy.
LAG
Lag isthe time delay between applying throttle and achieving useful boost. Representative lag
rates can be depicted by the following chart:
RPM
Paxton style
Classic turbo
Bell Engr turbo
MAX BOOSTAT
THATRPM
TIMETO MAX BOOST
3000
3000
2.5
5.0
1.0 Sec
1.0 Sec
2200
5.0
.25 Sec
POWER
Fun isfurther a function of power. The power output of our twin turbo is390 bhp. It can generally
be accepted that the most powerful unit has one element of fun in excess of the others.
To acquire a further feel for the actual performance of a vehicle without driving it, it is often
helpful to compare the acceleration rates with other known vehicles with similar pound per
horsepower ratings. Our twin turbo system will produce equal or faster 0 to 60 acceleration rates
than some other interesting well known automobiles. Road & Track magazine publishes a road
test summary in each issue offering excellent comparison data.
Fun isa also a function of smooth driveability. Our system does not change the stock driveability
quality of the NSX.
LOW ENDAND MID-RANGETORQUE
The BEGIturbo will make more boost at just 2000 rpm than the Paxton/Vortech style can at 7000
rpm, and more than the classic turbo can at 3000 rpm. It is a relatively simple calculation to
show that the BEGI system can accelerate as hard in 4th gear at 3000 rpm as the
Paxton/Vortech based unit can in 3rd gear at any rpm. It is reasonable to suggest that the low
end and mid-range torque superiority of the Bell Engineering system isnot just somewhat better,
rather, it is orders of magnitude better.
Conclusion: The Bell Engineering turbosystem will oner a greater degree of fun than any other
form or brand of power improvement system.
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TX
210-349-6515
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2&0
BHP
200
150
100
50
POWER, BHP
_
STOCK
EZ2:l
PAXTON
EBB
BELL ENG. GROU
~
CARTECH
~
ROOTS
c=J
BBR TURBO
Although often stated in writing that the Paxton and Vortech style superchargers produce less
intake charge heat than a turbo, the claim iscompletely false. Simple temperature probes can
prove it in minutes, The Paxton style blower will raise the charge temperature at 5 psi boost by
approximately 70 degrees f. No intercooler is present in any Paxton or Vortech based system
to reduce those 70+ degrees, The turbosystem we offer will raise the charge temperature only
55 degrees at the same boost, Our system, however, utilizestwo intercoolers that remove 90%
of the heat put in by the turbos, Thusthe air charge entering the engine isup approximately 10
degrees over ambient with the BEGIsystem, whereas the Paxton and Vortech style systemswill
receive the full 70+ dose. Clearly, these systemscreate heat levels over sixtimes greater than
our twin turbosystem. It isinteresting that the designers of the lessthermally efficient supercharger
systems choose not to use charge cooling yet they clearly need it the most.
The extreme ne~d for high quality charge cooling has been met by BEG!.No others have tried,
AIR FUELRATIOS
Supplying fuel in proper proportion to the air when operating under boost has proven to be the
singular most difficult facet of turbo/supercharging, We have solved this problem by driving the
fuel pressure up as the boost rises,
The BEGIsystem will keep the air/fuel ratios correct under all operational conditions.
With respect to emissions,economy, reliability and driveability, it isour opinion that the engine
management electronics should not be altered in any way,
MARGIN OF SAFETY
Clearly a system that will deliver performance as aovertised must have a margin of safety. This
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margin refers to the boost pressure point at which detonation will occur relative to the
advertised boost setting. If a given system runs 7 psi boost and will not encounter detonation
until 9 psi, it can be called 0. margin of 2 psi.If it does not have a margin it cannot be operated
as advertised. The margin is created by the heat and fuel controls designed into the system,
versusthe boost at which it operates.
The BEGINSXSYSTEM
will offer an adequate and proper margin of safety.
FUN
There existsa group of features and parameters that combine to create a truly fun car to drive.
Obviously power and smooth driveability are two of these. When specifically discussing
driveability of a turbo/supercharged engine the desirability of an early onset of boost is
commonly viewed as critical. Low speed boost capability is also an indication of the speed at
which the system can respond in the normal driving rpm ranges. It isvery interesting to note the
extreme fallacy of the lore stating that superchargers such as the Paxton produce more low end
boost than turbochargers. Thisisexactly the opposite of correct. The following graph represents
the boost rise rate of all known systems.
BOOST PSI
IS
3
:2
1
o
1
a
3
••.
7
5
a
RPM X 1000
-
BEOI
-+-
VORTECH'PAXTON
~
CLASSIC
TURBO
The rate of boost rise depicted by this graph is correct. Obviously the rate of boost rise of the
classic turbo isfar faster than the Paxton/Vortech style supercharger. The rate of riseisyet faster
for the new technology of the BEGIsystem.The reason turbos gain boost faster than Paxton style
blowers isthe simple fact that they can change speeds relative to the crankshaft. A turbo can
change speed from 5,000 rpm to 75,000 rpm without changing engine speed. At a constant
engine speed, a supercharger cannot change 1 rpm.
BELL
ENGINEERING
Legal for sale or use in California
GROUP,
INC.
only on racing vehicles whi:;h may never be used upon a highway
We feel it is fair to suggest that more automotive fun than a Bell Engineering Twin Turbo
equipped NSXwill be near.~mpossibleto find.
PERFORMANCE
On road performance as measured by the vari-corn VC-200 yielded the following data:
BEGITWINTURBO
Power; bhp
Torque; Ib-ft
o to 60; sec
1/4 Mile: time
Velocity
STOCK
390
270
305
4.4/4,8
225
12.8
14,4
113
99,0
5,9
These performance numbers were recorded with a stock engine, One of the BEGI design
objectives was to provide substantial performance with an unmodified engine, Although our
objective was clearly achieved, we were mindful of 1he adventurer that may want performance
in excess of that available from the stock engine. Thus, the design we have created is
expandable in the performance envelope to provide virtually any power rating consistent with
engine preparation.
INSTALlATION
The ease of installation should only be a seriousconcern if the buyer does not do hisown work,
Sublet expenses can add up to significant numbers, but hobby/fun time for the diy'er should not
be of concern, if kept within reasonable bounds, BEGIstrongly urges the buyer with modest
mechanical ability to tackle the job himself, save the install labor costs, and learn the system
while assembling it. There isno rocket science here, and no specific turbo experience required.
Thisisa simple systemto install,It isestimated that th,~firsttime inexperienced installercan install
the BEGIsystem in as few as twelve hours.
Twenty years of experience has clearly shown that the pride of ownership will make the diy'er
a generally better installer than the time clock conscious professional technician, Pride and
success are in the details and the owner tends to do details well.
QUALITY
The essence of quality isthe ability to function well and maintain an attractive appearance for
many years, The details of quality run from material selection, craftsmanship, choice of
turbo/super charger, surface coatings, to fits and finishes,
The BEGIsystem feature stainlesssteel construction on all hot components and all intake side
items are powder coated.
No body work modifications are required.
Quality extends to instructional material and service after the sale, as well.
BELL
ENGINEERING
Legal for sale or use in California
GROUP,
INC.
only on racing vehicles which may never be used upon a highway
We would be delighted to have any quality aspect of our system compared in detail with that
of any other system.
SUMMARY
It should be obvious that we feel our systemscompare favorably with all aspects of all others.
We invite discussion,debate, argument if necessary, third party review, an all competitors runoff, or any other means of comparison.
Bell Engineering Group, Inc. represents twenty years of applied turbosystem design and
engineering. We are confident we offer the highest science available today in performance
systemsfor your ACURA NSX.
Installations available at our shop for $700. Please call for an appointment.
Bell Engineering offers a pickup and delivery service nation wide for the cost of airfare and fuel
only.
California air resources board exemption order application pending.
System price: $7,850
11723
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Legal for sale or use in California
SAN
ANTONIO
TX
210-349-6515
only on racing vehicles whi,:::h may never be used upon a highway
MA~AZINE
COMMENTARY
Over the past twenty-two years Bell Engineering Group Inc, formerly
known as Cartech Inc. has enjoyed more than eighty magazine feature
articles. Collected here are just a few of the comments.
Motor Trend
Rick Titus re Cartech Supra Turbo: "Quality exceeds
that of OEM." "A Toyota Supra Turbo that goes ballistic." IIClean,
well planned installations." "Sets new standards for aftermarket
engineering. II
Automobile Magazine Barry Winfield, re Cartech Miata Turbo:
"It streaks down the road with a vehemence that is totally
unexpected from one of these friendly little sports cars."
Autoweek Bill Lovell, on Cartech' s RX-7 Turbo: "It looks more
factory than the factory." "Two seconds faster than the factory
turbo." --- "Peace brother."
Car Craft
C. Van Tune about our Mustang 5:0 turbo: "The
engineering magic behind this potent pony comes from Cartech of San
Antonio."
Road &
former
into a
177mph
Track
Andrew Bornhop re the Mustang turbo: "Founded by
racer Corky Bell, San Antonio based Cartech has blossomed
leading aftermarket turbo technology firm." "Think about
for a moment,. fairly quick is an understatement."
Turbo & High Tech Performance Jeff Hartman on the Twin Turbo NSX:
"The boost gauge swings instantly toward five psi and the outside
world begins to blur. The NSX now has the horsepower to play hard
ball in the big leagues."
Rotary Rocket Magazine Dick Turner about the Cartech Turbocharged
RX-7: "Corky,·Bell is a brilliant engineer who is dedicated to
getting the job done without a lot of fuss or bother." "To set the
record straight, I've probably driven 500 RX-7's with every type of
go fast gadget you can imagine. I can promise you this, the Cartech
RX-7 is the fastest car of its type I have ever driven."
Road & Track Ted West on the Honda CRX Turbo: "No other way to put
it, pretty wonderful. II"Corky Bell, be proud."
Automobile Magazine
William Jeanes, on the Cartech Supra:
"Turbocharging is Cartech' s specialty, they do it carefully and
well."
Turbo & High Tech
"With the pedal to
five psi boost at
larger engine than
Jeff Hartman, on the AerodynejCartech Miata:
the metal, the Aerocharger instantly made over
1000 rpm." "You might think it had simply a
stock, since there is no detectable turbo lag."
HORSEPOWER, ACCELLERATION, AND POWER TO WEIGHT RATIOS
REVISED 4-1-91
PERFORMANCE COMPARISON CHART - DATA GATHERED FROM
CARTECH T~STING AND MAGAZINE ROAD TESTS
VEHICLE
BHP
Acura Legend 4dr-1988
151
Alfa Romeo GTV-6-1988
154
Alfa Twin turbo GTV-6
230
Aston Martin V-8 Vantage
300
Audi 5000CS Turbo 4X4-1988
158
BMW 320i
108
BMW 320i CARTECH TURBO
210
BMW 318i
101
BMW 318i CARTECH TURBO
195
BMW 325es
121
BMW 325es CARTECH TURBO
228
BMW 325is
167
BMW 325i CARTECH TURBO
283
BMW 535i
182
BMW 535i CARTECH TURBO
341
BMW 635csi
182
BMW 635csi CARTECH TURBO
360
BMW 735i
182
3MW 735i CARTECH TURBO
341
3uick Grand National
245
3uick GN CARTECH UPGRADE
293
~amaro IROC Z28 5.7L
240
~orvette
240
:orvette "Callaway Turbo"
345
:hrysler Omni GLH Turbo
146
:hrysler "Shelby GLH"
175
)atsun 280ZX Factory Turbo
180
~80ZX Turbo CARTECH UPGRADE
274
)atsun 280Z
155
:80Z CARTECH TURBO EFI
265
:80Z CARTECH TURBO (w/carbs) 290
80Z CARTECH MAX (w/carbs)
400+
OOZX Stock turbo
200
OOZX Turbo CARTECH MAX EFT. 384
OOZX Twin Turbo
300
OOZX TWIN TURBO MAX EFFORT
475
eTomaso Pantera GTS
350
errarl F40
478
errari Testarossa
380
ord Mustang LX 5.0L
225
USTANG,CARTECH LEVEL I
325
USTANG,CARTECH LEVEL II
425
ARTECH TWIN TURBO (modified) ord T-Bird Turbo W/IC
190
ARTECH T-Bird Max Effort
330
Jnda CRXsi 16V
108
Jnda CRXsi CARTECH TURBO
175
~guar V-12 XJS
262
WEIGHT
0-60
3077
2875
3030
4110
3351
2710
2745
2450
2500
2723
2778
2805
2855
3230
3265
3380
3445
3540
3605
3349
3365
3295
3216
3280
2237
2483
3160
3200
2965
3010
3005
3005
3265
3300
3450
3450
3250
2425
3500
3140
3190
3220
8.1
3380
3410
2115
2160
4040
8.5
6.2
6.8
8.3
9.0
6.2
11. 6
6.2
9.0
5.9
8.2
5.7
7.9
5.3
8.5
5.3
9.1
6.5
6.0
5.3
6.7
5.8
5.0
1/4 MILE
16.4
16.4
14.5
15.3
16.4
16.8
14.1
18.3
14.3
16.7
14.0
16.0
13.7
16.1
13.6
16.3
13.0
16.7
14.6
14.5
13.8
15.2
14.4
13.7
16.3
15.3
LBS/BHP
20.4
18.3
13.2
13.7
21.2
25.1
13.0
24.3
12.8
22.5
12.2
16.8
10.1
17.7
9.7
18.5
9.6
19.4
10.6
13.7
11. 5
13.7
13.4
9.5
15.8
15.3
14.2
19.2
6.1
14.1
11.7
8.1
5.9
16.1
19.1
14.0
13.7
12.9
15.7
13.2
11. 4
8.1
6.7
7.8
5.4
4.9
7.4
4.9
6.7
4.6
5.5
15.0
12.8
14.0
3.9
5.3
6.0
5.0
3.3
11. 5
8.5
5.5
16.4
8.9
6.3
8.8
10.4
7.5
16.3
8.5
N/A
N/A
9.3
N/A
13.4
9.2
15.0
12.9
13.9
10.0
11. 6
7.6
13.7
17.1
14.6
16.7
17.8
10.3
19.6
12.3
15.4
HORSEPOWER, ACCELLERATION, AND POWER TO WEIGHT RATIOS
REVISED 4-1-91
~amborghini Countach 5000S
455*
3280
4.2
7.2
13.7
(*note; inconsistant power vs acceleration )
~otus Esprit Turbo SE
. 264
2975
4.7
13.3
NjA
1aserati Bi-Turbo E
205
2910
6.3
14.2
15.0
1azda Miata
116
2205
9.7
19.0
17.4
:artech Miata Turbo
185
2240
6.3
14.7
12.1
1azda RX-7 GSL (79-85 12A)
101
2350
9.9
23.3
17.4
~X-7 CARTECH TURBO 12A
235
2400
5.5
13.7
10.2
~X-7 CARTECH TURBO 13Bported 340
2400
4.5
7.1
12.8
1azda RX-7 GSL-SE (84-85)
135
2550
8.5
18.5
16.4
~X-7 GSL-SE CARTECH TURBO
263
2600
5.7
9.9
13.9
1azda RX-7 Sport (86-87)
146
19.2
2805
8.5
16.5
~X-7 86-88 CARTECH TURBO
270
10.6
2855
5.1
13.4
1azda RX-7 Turbo II
182
2850
6.6
15.7
15.2
~X7 TurboII CARTECH LEVEL I 258
11.1
2865
5.4
13.8
~X7 TurboII CARTECH LEVEL II 315
9.1
2870
5.1
13.3
1azda 626 Turbo
120
22.0
2640
7.8
16.0
)26 Turbo CARTECH UPGRADE
150
17.7
2655
6.9
15.1
1ercedes 2.3-16
167
18.0
3010
7.8
16.2
16.3
1ercedes 560 SEC
238
3890
7.0
15.5
17.2
1erkur XR4Ti
175
2920
7.9
16.0
12.4
(R4Ti CARTECH UPGRADE
237
14.6
2935
6.2
17.5
1itsubishi Starion
ESI-R
176
16.2
3087
8.3
16.4
)ontiac Trans-Am (5.7. TPI)
210
3435
7.9
16.1
12.9
)orsche 911
214
14.3
2756
5.7
11.2
)orsche 928S
316
3549
6.3
14.7
10.5
13.4
)orsche 911 Turbo
282
2976
5.0
7.9
2905
4.7
13.3
)orschejRuff 930 Turbo
369
18.9
16.1
)orsche 944
147
2780
8.2
13.8
14.6
)orsche 944 Turbo
217
2992
6.0
18.2
16.5
2910
8.6
;aab Turbo 16V
160
21.8
16.8
3045
8.7
'oyota Supra 82-86 2.81iter 161
11. 3
14.8
3045
6.1
;upra 2.8 CARTECH TURBO
270
17.3
16.2
3460
8.3
'oyota Supra 86.5up 3.01iter 200
11.1
13.8
3495
5.3
;upra 3.0 CARTECH TURBO
315
15.3
15.0
3522
6.8
;upra Factory Turbo 3.01iter 230
10.6
14.3
3517
5.8
;upra CARTECH UPGRD.LEVEL I 333
9.7
13.9
3520
5.3
;upra CARTECH UPGRD LEVEL II 362
9.0
13.6
3530
5.0
;upra CARTECH UPGRD LEV. III 392
****NOTE: ALL TIMES ARE TRACTION DEPENDENT****