1
GT Power Simulation of the Influence of Exhaust Manifold Design on Sound Quality
Ivan Arbuckle
Emcon Technologies
GT Power User Conference – Detroit 2009
2
� Objective
• Study the exhaust manifold design factors that influence noise− Asymmetry
− Restriction
− Cylinder-Cylinder Interference
• Characterize the Engine Noise Source Characteristics − Ps and Zs from the MultiLoad Template
3
EVO EVC
Why is there noise in the Exhaust?
EVO EVC
EVO EVC
•The noise is caused by the unsteady mass flow rate from the engine. This leads to oscillations in the exhaust pipe which are emitted at the outlet as tail pipe noise.
•If the flow from the engine was a steady (non oscillating) flow there would be no order noise.
4
-1.5
-1
-0.5
0
0.5
1
1.5
0 180 360 540 720
0.5 EO Cylinder 1
Why is 0.5 OE suppressed in a 2 cylinder engine ?
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 180 360 540 720
0.5 EO SummationTotal Cancellation-∞ dB re 1 Cylinder
+ =
-1.5
-1
-0.5
0
0.5
1
1.5
0 180 360 540 720
All orders are ‘shifted’ 360°CA for the second cylinder since it fires 1 revolution later.
0.5 EO Cylinder 2
5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 180 360 540 720
-1.5
-1
-0.5
0
0.5
1
1.5
0 180 360 540 720
-1.5
-1
-0.5
0
0.5
1
1.5
0 180 360 540 720
1.0 EO Cylinder 1
1.0 EO Cylinder 2
1.0 EO Summation(Doubled, or +6dB)
Why is 1 EO not suppressed in a 2 cylinder engine ?
6
-1.5
-1
-0.5
0
0.5
1
1.5
0 180 360 540 720
0.5 EO Cylinder 1
-1.5
-1
-0.5
0
0.5
1
1.5
0 180 360 540 720
0.5 EO Cylinder 2Phase Shift 45°
What if firing is not 360 °°°° separated for a twin cylinder ?
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 180 360 540 720
Total 0.5 EOOnly Partial Cancellation
-6dB re 1 Cylinder
7
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 180 360 540 720
-1.5
-1
-0.5
0
0.5
1
1.5
0 180 360 540 720
-1.5
-1
-0.5
0
0.5
1
1.5
0 180 360 540 720
0.5 EO Cylinder 1
0.5 EO Cylinder 2Lower Amplitude
Total 0.5 EOOnly Partial Cancellation
-6dB re 1 Cylinder
An amplitude shift can be caused by;
•incomplete combustion in 1 cylinder
•inconsistent cylinder-to-cylinder Veff
•or imbalanced restriction in exhaust manifolds.
What else can cause incomplete 0.5 EO Cancellation ?
8
Singles & Twins
45°V Twin Common
Crank Throw
(405°-315°)Single Cylinder
(4 Stroke)
Horizontally Opposed Twin (360°Firing)
9
Singles & Twins: Source Level (Ps)Engine Source Strength, Ps
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re
20µP
a
Single
360° H-O Twin
45° V Twin
0.5 EO Engine Source Strength, Ps
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re
20µP
a
Single
360° H-O Twin
45° V Twin
1 EO
Engine Source Strength, Ps
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re
20µP
a
Single
360° H-O Twin
45° V Twin
1.5 EO Engine Source Strength, Ps
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re
20µP
a
Single
360° H-O Twin
45° V Twin
2 EO
10
4 Cylinder (Firing 1-2-4-3)
4-2-1 Manifold
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re
20µP
a
0.5 EO 1 EO1.5 EO 2 EO
4-2-1 with equal length primary &
secondary
I4 with Log Manifold
Log Manifold
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
0.5 EO 1 EO1.5 EO 2 EO
1
2
3
4
Boxer 4
12
34
Boxer 4
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
0.5 EO 1 EO1.5 EO 2 EO
11
V6(Firing 1-4-2-5-3-6 = R-L-R-L-R-L)
1
2
3
4
5
6
6-2-1 Manifold
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
0.5 EO 1 EO1.5 EO 3 EO Log Manifold
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
0.5 EO 1 EO1.5 EO 3 EO
1
2
3
4
5
6
90°V6Firing 90°-150°-90°-150°-90°-150°
Odd Fire V66-2-1
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpmP
s, d
B(li
n) re
20µ
Pa
0.5 EO 1 EO1.5 EO 3 EO
6-2-1 SymmetricalAsymmetric
Log
13
Cross Plane V8(Firing 1-3-7-2-6-5-4-8 = R-R-L-R-L-L-R-L)
-0.05
0
0.05
0.1
0.15
0.2
0.25
0 90 180 270 360 450 540 630 720
Crank Angle °
Exh
Val
ve M
ass
Flo
w
(kg/
sec)
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4 Cylinder 5Cylinder 6 Cylinder 7 Cylinder 8 Summation
Symmetrical 8-1 Manifold
Summation
Uneven bank-to-bank firing on a cross-plane crank V8 causes variation from cylinder to cylinder. A 8-1 manifold can overcome this
(as can a flat plane crank).
8-2-X-2
-0.05
0
0.05
0.1
0.15
0.2
0.25
0 90 180 270 360 450 540 630 720
Crank Angle °
Exh
Val
ve M
ass
Flo
w
(kg/
sec)
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4 Cylinder 5Cylinder 6 Cylinder 7 Cylinder 8 Summation
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V8 (Firing 1-3-7-2-6-5-4-8)
Dual V8 – No Bank-to-Bank
mixing.
H-Pipe V8 with equal length
primary
X-Pipe V8 with equal length
primary
5
6
7
8
1
2
3
4
8 to 2 Manifold
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
2.5 EO 1.5 EO2 EO 4 EO
H-Pipe
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
2.5 EO 1.5 EO2 EO 4 EO
X-Pipe
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
2.5 EO 1.5 EO2 EO 4 EO
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V8 (Firing 1-3-7-2-6-5-4-8)
8-into-1 V8 with equal
length primary
Y-Pipe V8 with equal length
primary
Y-Pipe V8 with equal primary, Unequal Secondary
8 to 1 Manifold
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
2.5 EO 1.5 EO2 EO 4 EO
Asymetric Y-Pipe
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
2.5 EO 1.5 EO2 EO 4 EO8-2-1 Y Manifold
100
110
120
130
140
150
160
170
180
190
200
1000 2000 3000 4000 5000 6000
rpm
Ps,
dB
(lin)
re 2
0µP
a
2.5 EO 1.5 EO2 EO 4 EO
16
H-Pipe ‘Tuning’ on a V8 Application
60
70
80
90
100
110
120
1000 2000 3000 4000 5000 6000 7000
rpm
Tai
l Pip
e N
oise
- d
B(A
)
None
1.75"
2.5"
X
1.5EO
60
70
80
90
100
110
120
1000 2000 3000 4000 5000 6000 7000
rpm
Tai
l Pip
e N
oise
- d
B(A
)
2.5EO
60
70
80
90
100
110
120
1000 2000 3000 4000 5000 6000 7000
rpm
Tai
l Pip
e N
oise
- d
B(A
)
4EO
60
70
80
90
100
110
120
1000 2000 3000 4000 5000 6000 7000
rpm
Tai
l Pip
e N
oise
- d
B(A
)
8EO
Varying the H-pipe diameter can have a large affect on half order levels.
This is used as another tuning parameter to achieve the best sound quality.
Small
Large
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modeFrontier Optimization V6 →→→→V8 : Targets
100
110
120
130
140
150
160
170
180
190
0 50 100 150 200 250 300
Frequency (Hz)
Sou
rce
Pre
ssur
e Le
vel (
dB)
at 2
000
rpm
6-2-1 Baseline V8 with H-pipe
Ps at 2000 rpm
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Conclusions
Multi-Cylinder Engines have the potential to significantly suppress half orders
But there are many design features which can re-introduce half order content;
Engine Factors�Odd-Fire Engine�Even Fire engine with Odd-Fire on each bank
Manifold Factors�Length Differences - introduces phase errors�Restriction Differences - introduces amplitude errors�Inadequate Bank-to-Bank Mixing
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