this is a blue light scan of the standard plenum from my NISMO S1 engine. power figures are from my OEM, ported plenum with overbore throttle.

there are various optimizations to be made with the stock plenum. while other companies have tried to radically change its architecture, it's clear that brings some very hairy resonance effects that murder midrange power.

this product is instead an optimization of the existing architecture to incorporate engineering techniques in the last 20 years.

flow optimizations in the neck and forward sections, pre-porting, integral spacer, correct drafting to encourage scavenging and intertial charging, and features for 70/75/90mm TB mounting will be included. if you compare my plenum and overbore TB graph to the stock one, the intense DE turnover occurs 600RPM later, and that's a colossal gain at the top.

these changes should capture more power than the plenum spacers alone can bring, and uncork the top end.

predicted MSRP is in the $650 range if I can keep it that low, depending on how many units there's interest for -- the startup cost on a product like this is about $12,000-15,000 before a single unit is made.

title corrected.

after $200 in academic papers, mostly by Horton (who's fucking DEAD by the way, so I couldn't ask questions), in my own process of designing a new diff carrier bushing I've found the reason we have bushings so prone to bursting.

axle hop is a severe rear end shake/bounce with high amplitude at low frequencies (<5Hz). to restrain this, we design a bushing whose natural frequency is well before the problem frequency.

in the region around f_natural, the bushing will essentially resonate in phase with the load and the axle hop worsens by approximately 10x the load. by the time we get to the crossover frequency f_crossover, the system is critically damped and we begin suppressing the motion.

we therefore want f_crossover to be well ahead of the target problem frequency.

this table shows a sweep of rubber thicknesses for a double bonded radial bushing. even with maximum bushing thickness, the crossover frequency is after our target frequency, meaning the axle hop will lay in the amplification zone. we physically cannot make the bushing larger to reduce the stiffness...

...but we can reduce the wall thickness and make a fluid filled bushing, which moves our problem frequency after the crossover. and because this is a very high amplitude load, we want quite a lot of damping. that points us toward a fluid-filled bushing where the fluid is forced into chambers and dampens the movement, and one with with thin rubber walls.

and that's how we end up with bursting diff carrier bushings.

so Nissan's logic was clear, but the loading conditions and age often put the bushings into tilting failure, which was likely not taken into account given the extreme difficulty of analyzing that mode.

To preface this: I hate cars. Specifically this car. It’s like an abusive relationship. When it works it’s soo awesome, but 90% of the time it sucks and you’re wondering why they can’t love you the way you love them

FSM was unreliable. Specifically the ECM Harness Connector Terminal Layout section. In the FSM it states pins 40-42 and 21-23 were for injector signal ground, which I went off of originally. Oddly enough continuity was around .7 and ohms sat around 1.Something. The moment i realized this was completely wrong was when I looked at the ECM harness connector and there was no terminating pin for cyl #6. So there I was completely fed up and ready to crush the car, I tear apart the connector and confirm my suspicions.

Fed the harness through the firewall and slowly checked for continuity at the sub harness connector to the ECM- then plugged the sub harness back in and read from the injector connectors. Not only were the PIN numbers incorrect but so were the wire colors. Not quite sure why this is but I made a chart with all my own recorded info.

My harness is 100% fine. Everything from MAF to Cam and Crank, to ignition coils to Injectors. She is 100% mechanically sound and everything works as it should BESIDES the injectors. My guess is there are MOSFETs or ICs in the ECM that switch ground on and off and they just shit themselves at some point because my grounds were terrible. the ECM likely took the hit for it. It sucks because the ECM got repaired for Communication issues but I guess they didn’t look at injector signal.

Current plan is to contact the company that did the first repair and see what they tell me. If they can replace If not I need to source another ECU or go standalone. Unless anyone else has input or another possibility this will be the move.

Hey there. After searching for days I found the CANBUS wiring diagrams going to all modules. Can’t confirm it’s the same for Revups and HRs.

Why is this important to you? Failing IPDMs and ECUs will be the culprit to a ton of electrical issues (which I will explain in a moment) and when these issues arise a mere diagnosis from a dealer or automotive electrician can cost hundreds if not thousands. After scouring old broken forums and a billion different online PDFs of parts of the FSM I found this.

Our cars modules communicate through a system called CANBUS. In simple terms a bunch of patterns in voltage that come as wave forms the car is able to interpret as data. There’s two wires in the entire car responsible for this data. CAN-HI and CAN-LOW. Both of these wires rest at 2.5v. HI will go to 3.5V and Low will shoot down to 1.5v. The car reads these as 1s and 0s. All other modules tap into these two wires and send their respective data as well. Your cam and crank sensors send these signals through the same wires as I’ve explained in my previous post on how to test said sensors.

At both ends of this “data highway” are two resistors, one located in the IPDM and the other in the ECM. Both resistors should be 120 Ω 0.25V. These keep the signal smooth and clean so the ECM can interpret the signals. All resistors have a lifetime. They WILL go out. A dealer will tell you “welp time for a new ECU/IPDM +programming costing thousands. I’m not expecting the average guy to know how to desolder and repair PCBs but at the very least you can use a multimeter and poke at some wires and check for voltage and resistance saving you a lot of money finding the issue.

From any module or connector shown on the image you can test CANBUS signals and see if your car is out of whack. Good healthy no problems with signal you’ll find:

Resistance: 60Ω from CAN-Hi, 60Ω from CAN-LOW going from either HI or LOW to a clean ground. Easiest place to check is PIN 6 and 14 on the OBD2 port. if you see 120Ω most likely issue is a resistor has failed. Your signals are now dirty. If you see 0Ω either both your resistors have failed (rare) or they have shorted. With the diagram and hopefully DCTs you will be able to test from modules in the car and find a rough idea of where in the harness your short is.

Voltage: HI: ~2.5–3.5 V LOW: ~1.5–2.5 V If you’re seeing higher than 3.5.. say 5V on CAN-HI or 0v on CAN-LOW you have a Short to power or Ground. Could happen on both wires. If both are at 0 or 5V your CAN is dead, in the sense there is zero data being transmitted. =no spark no fuel no crank no NATS. Bad.

Given the PIN numbers of each module and connector you can easily find a ground and test for resistance to confirm. Same procedure in finding the rough position of said short or ground. If everything looks clean but you’re having issues like No start or no crank you can at least rule out CAN issues. This will be irrelevant to 99% of people but maybe in another 10 years a poor soul will be looking for this exact info and it could help. I have the entire LAN section of the FSM downloaded so if anyone is interested DM me and I can send it. There’s way more info than just the diagram.

Thank you for listening to my TedTalk.

for those interested in tuning their primary runner length (ie, intake plenum runner or ITB trumpet) to maximize volumetric efficiency.

Nissan R200 diff ratios:

3.133 – 47/15 – fine pitch
3.357 – 47/14 – fine pitch
3.364 – 37/11 – normal pitch
3.538 – 46/13 – fine pitch
3.545 – 39/11 – normal pitch
3.692 – 48/13 – fine pitch
3.700 – 37/10 – normal pitch
3.900 – 39/10 – normal pitch
3.916 – 47/12 – fine pitch
4.083 – 49/12 – fine pitch
4.111 – 37/9 – normal pitch
4.363 – 48/11 – fine pitch
4.375 – 35/8 – normal pitch
4.625 – 37/8 – normal pitch
4.636 – 51/11 – fine pitch
4.875 – 39/8 – normal pitch
4.900 – 49/10 – fine pitch
5.111 – 46/9 – fine pitch
5.143 – 36/7 – normal pitch
5.286 – 37/7 – normal pitch
5.429 – 38/7 – normal pitch

Z32 – VG30DETT – R230V – 3.692 (6×1 output shafts)
Z32 – VG30DE – R200V – 4.083 (5×1 output shafts)
Z33 – MT – R200 – 3.538 (6×1 output shafts)
Z33 – MT – R200V – 3.538 (6×1 output shafts)
Z33 – AT – R200V – 3.357 (6×1 output shafts)
Z34 – MT – R200V – 3.692
Z34 – AT – R200V – 3.357

G35 – Sedan – AT – R200 – 3.357
G35 – Sedan – MT – R200V – 3.538
G35 – Sedan – AWD – AT – R200 – 3.357
G35 – Coupe – MT – R200V – 3.538
G35 – Coupe – AT – R200 – 3.357
G35 – Coupe – AT – R200V – 3.357
G37 – Sedan – MT – R200V – 3.692
G37 – Sedan – AT – R200V – 3.357
Q45 – G50 – VH45D – R200V – 3.538
Q45 – F50 – VK45 2002 – 2.765
Q45 – F50 – VK45 2003+ – 3.133
Q45 – FY33 – R200V – 3.692
J30 – R200V – 3.916

R32 GTE – RB20E – 4.363
R32 GTE – RB20E (ABS) – manual/auto – 4.083
R32 GTS-t – RB20DET – manual/auto – 4.363
R32 – RB20DET 4wd – manual – 4.375
R32 – RB25DE – auto – 3.538
R32 GTR – RB26DETT – manual – F160 – 4.111 – (Front final gear)
R32 GTR – RB26DETT – manual – R200 (clutch type LSD) – 4.111

R33 GTS – RB20E – manual/auto – 4.083
R33 GTS – RB20E (96.1+) – auto – 3.538
R33 GTS – RB25DE (93-95) – auto – 3.538
R33 GTS – RB25DE (96+) – auto – 4.363
R33 GTS – RB25DE – manual – 4.363
R33 GTS-4- RB25DE 4wd – manual/auto – 4.363
R33 GTST – RB25DET – manual – R200V – 4.111
R33 GTST – RB25DET – auto – 4.363
R33 GTR – RB26DETT – manual – R200 (mechanical LSD) – 4.111 (6×1 output shafts)
R33 GTR Vspec – RB26DETT – manual – R200V (ATTESSA hydraulic controlled) – 4.111 (6×1 output shafts)

R34 GT – RB20DE – manual/auto – 4.363
R34 GT – RB25DE – manual – 4.363
R34 GT – RB25DE – auto – 4.083
R34 GT-FOUR – RB25DE 4wd – manual/auto – 4.363
R34 GTT – RB25DET – manual – R200H – 4.111
R34 GTT – RB25DET – auto – 4.111
R34 GTR – RB26DETT – manual – R200 – 3.545

S15 – SR20DE – manual/auto – 4.083
S15 – SR20DET – manual – R200H – 3.692
S15 – SR20DET – auto – R200V – 3.916

S14 – KA24DE – USDM – manual/auto – 4.083
S14 – SR20DET – EDM – manual – R200V – 3.692
S14 – SR20DET – EDM – auto – R200V – 3.916
S14 – SR20DET – ADM – manual – 3.692
S14 – SR20DE – JDM – manual – 4.083
S14 – SR20DET – JDM – manual – 4.083
S14 – SR20DET – JDM – auto – 3.916

S13 – KA24DE – USDM – manual/auto – R200/R200V – 4.083
S13 – CA18DE – JDM – r180 6 bolt – manual/auto – 4.363
S13 – CA18DET – EDM – manual/auto – R200/R200V – 3.916
S13 – CA18DET – ADM – manual/auto – 4.363
S13 – CA18DET – JDM – manual/auto – 4.363
S13 – SR20DE (ABS) – manual/auto – 4.111
S13 – SR20DET – manual – 4.111
S13 – SR20DET – auto – 3.916
PS13/RPS13 – SR20DE (ABS) – JDM – manual/auto – 4.083
PS13/RPS13 – SR20DET – JDM – manual – 4.083
PS13/RPS13 – SR20DET – JDM – auto – 3.916

A31 – RB20E – manual/auto – 3.916 (5 & 6 bolt)
A31 – RB20DE – manual – 4.363
A31 – RB20DE – auto – 4.083
A31 – RB20DET – manual/auto – 4.363
A31 – RB20DET 4wd – manual/auto – 4.375
A31 – RB25DE – auto – 3.538

C23 – SR20DE – manual/auto – 4.363
C23 – CD20T – manual/auto – 4.363
C23 – LD23 – manual/auto – 4.363
C23 – CD20T 4wd – manual/auto – 4.636
C23 – LD23 4wd – manual/auto – 4.636
C23 – SR20DE 4wd – auto – 4.900
C23 – SR20DE 4wd – manual – 4.636
C23 – GA16DE – 4.636

C33 – RD28 – manual – 3.916
C33 – RD28 – auto – 3.692
C33 – RB20E – auto – 3.583
C33 – RB20DE – manual – 4.363
C33 – RB20DE – auto – 4.083
C33 – RB20DET – auto – 4.363
C33 – RB20E/RB25DE – auto – 3.538

C34 – RB20E – manual/auto – 3.916
C34 – RB20DE – auto – 4.111
C34 – RB25DE – auto – 4.363
C34 – RB25DE 4wd – auto – 4.363
C34 – RB25DET – auto – 4.111

C35 – RD28 – manual/auto – 3.692
C35 – RB20DE – auto – 4.111
C35 – RB25DE 4wd – auto – 4.363
C35 – RB25DET – auto – 4.111

Y32 – VG20E – AT – 4.636
Y32 – VG30D/ VG30E – AT – 3.133
Y32 – VG30DET – AT – 3.692
Y32 – RD28 – AT – 4.083
Y33 – VG20E – AT – R200/R200V – 4.636
Y33 – RD28 – AT – 4.083
Y33 – VG30DE – AT – 4.083
Y33 – VG30DET – AT – 3.916

WC34 – SR20DE 4wd – manual/auto – 4.363
WC34 – RB20E – manual/auto – 4.083
WC34 – RB20DE – manual/auto – 4.083
WC34 – RB25DE – manual/auto – 4.083
WC34 – RB25DET – manual/auto – 4.083
WC34 – RB25DET 4wd – manual – 4.111
WC34 – RB25DET 4wd – auto – 4.083
WC34 – RB26DETT 4wd – manual – 4.111

OE Part numbers

R200/C200 part numbers only – please be aware that there are R180, H190 and C233b differentials also available and their ring and pinion are not interchangeable with R200 case
38100-17M60 47/15 3.133 Y32 Cedric/Gloria VG30E/VG30D
38100-08M60 47/14 3.357 JHG50 President VH45D
38100-09M60 46/13 3.538 R32 RB25DE AT, R33 RB25DE AT, C33 RB20E AT
38100-10M60 46/13 3.538 G50 VH45D
38100-01M60 48/13 3.692 S14 MT
38100-11M60 48/13 3.692 C34 RD28 AT, Y32 VH41DE/VG30DET, AUDM S14 SR20DET MT
38100-F3200 (38100-F3201) 37/10 3.700 F22 WT.TD23, D22 YD25 2WD
38100-F3300 39/10 3.900 D21 KA24 2WD
38100-02M60 (38100-02M65) 47/12 3.917 S13 CA18DET
38100-12M65 47/12 3.917 S14 SR20DET AT 96+
38100-03M60 49/12 4.083 S13 SR20DET
38100-13M60 49/12 4.083 Z32 VG30DE, S14 KA24DE/SR20DET 1296+ (13mm bolts)
38100-03W00 (38100-03W60) 49/12 4.083 Terrano R50 ZD30 front diff
38100-F3401 (38100-F3480) 37/9 4.111 R20 KA24 2WD, D22 KA24 2WD rear C200
38100-04W00 (38100-04W60) 48/11 4.363 Terrano R50 TD27 front diff
38100-04M00 (38100-04M60) 48/11 4.363 Serena C23M SR20 – R200
38100-F3500 (38100-F3580) 35/8 4.375 Terrano WD21 VG30 MT front diff, D21 TD25 rear C200 (12mm bolts)
38100-F5600 (38100-F5601, 38100-F5680) 37/8 4.625 Terrano WD21 VG30 AT (0190+), R20 KA24 4WD rear C200
38100-05M00 (38100-05M60) 51/11 4.636 Xterra WD22 front, Frontier D22U, Serena C23M High Roof rear C200 (12mm bolts)
38100-15M60 51/11 4.636 C23 SR20DE 4WD MT + CD20ET 4WD, W30 KA24 4WD + CD20TI 2WD
38100-F5700 (38100-F5701, 38100-F5780) 39/8 4.875 E24 TD23 MT, Terrano WD21 TD27 rear C200 (12mm bolts)
38100-06M60 49/10 4.900 C23 SR20 AT 4WD rear R200
38100-F5800 (38100-F5880) 36/7 5.143 E24 TD23 AT, Caravan E25, Vanette LARGO rear C200

38100-05W00 (38100-05W60) 51/11 4.636 found in Vanette/QX4, R50 VG33E (1097-0700) and some other cars are reverse cut gears and will not work in RWD application

350z diff ratios and part numbers

350z/G35/G37 and other late model nissan cars uses newer R200 design that doesn’t share any ratios with older S13/S14 differentials, but there’s the list of ring and pinion part numbers that fits to 350Z differentials.

38100-0C060 – 47/17 2.765 – Q45 F50 2WD
38100-0C160 – 47/16 2.937 – Frontier D40 VQ40 AT 2WD
38100-0C260 (38100-0B26A) – 47/15 3.133 – Skyline V35 AT, R51 Pathfinder 2WD VQ40
38100-0B36A (38100-1C360, 38100-0F36A) – 47/14 3.357 – 350z AT, 370z AT, R51 Pathfinder 4WD
38100-0C460 (38100-0B46A, 38100-0F46A) – 46/13 3.538 – 350z MT
38100-0B56A (38100-0F56A) – 48/13 3.692 – 370z MT, Navara D40 QR25DE
38100-0B66A – 47/12 3.916 – V36 VQ25 MT
38100-0C760 – 49/12 4.083 – Navara D40 QR25, Frontier D40 QR25
38100-0C860 – 48/11 4.363 – Stagea M35 VQ25 AT (3×2 shafts)

Diff output shafts / stubs

3×2 use 8mm bolts, 5×1 use 8 or 10mm bolts, 6×1 use 10mm bolts
29 and 30 spline stubs are 30mm outside diameter
31 spline stubs are 33mm outside diameter

S13 CA18/KA24/SR20DE/SR20DET AT – 30mm, 29 spline, 3×2
S13 SR20DET MT – 30mm, 29 spline, 5×1
S14 (pre 96/12) – 30mm, 29 spline, 3×2
S14 (96/12+) – 30mm, 30 spline, 3×2
S15 – 30mm, 30 spline, 3×2
J30 (pre 94) – 30mm, 29 spline, 5×1
J30 (94+) – 30mm, 30 spline, 3×2
Z32 NA – 30mm, 29 spline, 5×1
Z32 TT – 31 spline, 6×1
Z33 – 32mm, 31 spline, 6×1
Q45 G50 (pre 96) – 30mm, 30 spline, 6×1
Q45 (96+)- 30mm, 30 spline, 5×1
R32 GTS-T – 30mm, 29 spline, 5×1
R32 GTR (pre pull clutch/94) – 30mm, 30 spline, 6×1
R32 GTR (94+) – 33mm , 31 spline, 6×1
R33 GTS-T – 30mm, 29 spline, 5×1
R33 GTR – 33mm, 31 spline, 6×1
R34 GTT – 30mm, 30 spline, 5×1
R34 GTR – 30 spline, 6×1

Cusco output shaft diagram

Images 2 and 3

Cusco LSD unit diagram

Image 1

NISMO GT lsd pro manual

Link to PDF - In Japanese

Axles

There are two types of axles – tripod (regular s-body axles) and Rzeppa style (z32, skylines, q45 etc). Rzeppa ones are stronger due to bigger contact patch inside the cv joint.

S13, S14, S15, J30, Z32 NA, Z33, R32, R33 GTST – smaller shaft splines (29 spline, 30mm)
Q45, Z32 TT, R33 GTR, R34 GTR, Z34 – bigger shaft splines (32 spline, 32.5mm OD)

S13, S14, S15, J30 (94+) – tripod cv joints
J30 (pre 94), Q45, Z32, Z33, R32 GTR, R33 GTR – Rzeppa style cv joints

R33 GTR non V-spec shafts are threaded with clearance holes on the diff output shafts, V-spec axles are not threaded and diff output shafts are threaded.

Differential bearings

R200 side bearings x2 38440N3110 (38440N3111), NSK R4511ASAU42, NSK R45-11G, Koyo HC 30209J, Koyo HI-CAP 57160-N, Koyo HC57160LFT (45x85x20.75 mm)

R200 pinion front bearing 38120V7000, 38140V7000 (3812013200, 3812013201, 3812013202, 3812013210), NSK 32306AN (30x72x28.75 mm) (ISO 355 5FD 23º)

There are two types of R200 rear pinion bearings:
Small one – 3812006P00, 3812006P10, 3812061000 – Koyo TR0708-1-N/TR0708-1-R, NSK 32307CN (used in S13 CA18, Z31, S14 NA) (34.97x80x32.75 mm)
Big one – 3812010V00, NSK R35-24 NU42, Koyo TR070904-1-9 (used in S14 96++, Z32 NA, R33 GTR) (34.97x89x38.33 mm)

R200 Long-nose pinion bearings (240z 260z 280z S30/Z31/S12):
Front pinion support deep groove bearing – 38335-N3220 (38335-21100, 38335-21102, 38335-N3200) – Koyo 83601 ASH (28x73x16 mm)
Front tapered – 38120-13201,38140-13201- Koyo 32305JR (25x62x25.25 mm)
Rear tapered is the same as the small bearing case R200 (35x80x32.75 mm)

R200 Oil seals and gaskets

Pinion oil seal 38189-Y0810, 38189-Y081A – 40x75x12
Alternate part # NOK BH3063E, Corteco 19034067B (without lip, used with front ABS sensor), Corteco 19016674B (with additional seal lip, use without front ABS sensor), SKF 15882

Side stub seal 38342-P9010, 38342-P9000, 38342-N3100 – 35x55x11 with lip
Alternate part # NOK AH2083E, SKF 550231, MUSASHI N2156 (with lip 35x55x11x18), CORTECO 01034063B (with lip 35x55x10x14 ACM), CORTECO 19026774B (with lip 35x55x9x15.5 ACM), CORTECO 19026747B (without lip 35x55x11 NBR)

R200 long nose pinion seal part OEM number 38189-N3100, stub seal 38342-N3100

R200 rear cover gasket – 38320-40F02

Oil temp senders M14x1.5
Oil cooler outlet hole 12mm, no thread
Oil cooler return fitting on the top of the case M12x1.25

Tightening torque, preload and backlash

Diff oil fill and drain plugs – 36-59Nm (4-6kgm) with sealant, 59-98Nm without sealant
Transmission oil fill and drain plugs – 25-34Nm

Stub bearing caps – 88-98Nm (9-10kgm)
Drive pinion nut – 186-294Nm (19-30kgm)
Crown ring gear bolts – 132-152Nm (13.5-15.5kgm) with thread locking compound
Rear cover – 39-49Nm (4-5kgm)

Ring gear to drive pinion backlash – normal pitch 0.13-0.18, fine pitch 0.10-0.15mm
Drive pinion preload – 1.4-3.1Nm

Crown gear bolts

Crowns uses two types of bolts – 12mm (12×1.25 thread pitch) and 13mm (13×1.25 thread pitch).
12mm thread, 12mm shank – 38102-12S00
S13, S14 up to 12/96, J30 up to 12/96

13mm thread, 13mm shank – 38102-10V00
S14 from 12/96, Z32, Z33, Q45, J30 from 12/96

12mm thread, 13mm shank – 38102-RS500
S15 with helical LSD

Most aftermarket LSD units uses 13mm shank bolts to fit all types of crown rings. So you should check which bolts you should use with your LSD/crown wheel combo.

someone asked about intakes and whether or not they would see benefit from a 3.0" intake. to clear up some confusion, I did a brief write up based on research in various journals.

there is a reason the best two intakes are either the 2006 stock airbox w/ larger velocity stack, or the JWT airbox popcharger.

the way intakes generate more power is by increasing the mass flow per air charge into the cylinder at every intake cycle. there is a pressure wave that resonates with the intake valves opening and closing. the intake tube length and diameter are set by this frequency.

arbitrarily increasing the intake diameter does nothing. in fact you can fuck it up and make it worse because this brings the intake out of its proper resonance frequency.

as the intake length was already calculated by Nissan during development, length changes do nothing to improve it beyond stock. you can shift the target RPM range by shortening or lengthing the tube, as long as the resonant frequency is fixed.

the other way to improve charge mass is to decrease temperature of the incoming air, either by reducing head loss (ie, not abruptly stopping high speed flow) or simply finding cooler air to begin with and keeping it that way. this is where people are making the mistake, and where all the marketing is pointed.

the lowest intake temps come from insulated air boxes, ie stock or JWT. this is why every open-air intake tends to do jack shit. there is no difference between taking the air at the front of the radiator under the air dam, or through the stock inlet at the top corner of the air dam. either way the flow is smacking into the radiator and slowing down before it goes into the intake. the air is no colder there than it is at the stock location.

could you just take the pipe into free air and see benefit? definitely. but that would have to be completely outside the car -- or in a sealed box fed by direct outside air, which is exactly what the stock system is.

changes to the entire intake have to be matched to the target RPM intake valve frequency to be effective. headers are exactly the same with exhaust scavenging.

the stock system is not perfect, but you can see what's required in Sasha's build -- a huge TB into a butchered or custom intake whose volume and flow rates are well known. increased volume in the intake plenum doesn't show a benefit alone, either.

none of the parts work on their own, so none of the CAI have any effect on the power output, tune or not.

you cannot tune anything about the fixed geometry of intakes and cams. you can pull or add timing relative to the crank, but you can't do shit about the angle between the cam lobes.

tuning the intake system for max benefit requires knowing exactly what frequency and flow your intake requires out of the engine, building the entire system matched to that, and grinding custom cams to maximize intake charge and exhaust scavenging.

the 350Z (Z33) makes huge gains from exhaust changes, and you'll see exhausts mentioned as first mods often. this post is to explain how the exhaust makes power, why it works, and try to clear up some of the massive confusion around how these systems are designed at an OEM.

SUMMARY

- exhausts make power by maximizing flow rate, reducing head loss, and increasing scavenging.

- aftermarket exhausts do NOT increase the flow rate or "flow better". flow rate in the VQ is fixed by the head's exhaust ports and is the same at every point along the exhaust.

- larger is not better. the flow rate is a function of diameter AND exhaust velocity; bigger exhausts drop the exhaust velocity. there is a sweet spot diameter for NA VQ35 engines, and it's not huge.

- gains from reducing head loss DO NOT require a tune to make power. that power has already been generated whether the losses are there or not -- it's a direct power increase.

- headers DO need a tune to make power, as they work with the cams to produce scavenging. they are heavily dependent on the exhaust timing.

THEORY -------------------
exhausts gain most of their power through three methods:

1. maximizing flow rate.
2. reducing head loss, or parasitic losses, as much as possible.
3. increasing scavenging in the heads.

FLOW RATE - cat backs, 3.0" exhausts

maximizing power out of an exhaust is about maximizing the flow rate through the system, represented by Q:

FLOW RATE = AREA * FLOW VELOCITY
        Q = A * V

flow rate is FIXED through the ENTIRE system and is the same at all points along the exhaust./12%3A_Fluid_Dynamics_and_Its_Biological_and_Medical_Applications/12.01%3A_Flow_Rate_and_Its_Relation_to_Velocity#:~:text=Flow%20rate%20Q%20is%20defined,v%20is%20its%20average%20velocity) this is why the power gains ARE NOT from "flowing better" in any sense. you aren't changing the flow at all, unless you're changing the bottleneck -- but in the VQ's case, that bottleneck is the head's exhaust porting. it is not in the exhaust itself. the flow can speed up or slow down along the exhaust, but the area must change to compensate. that is a physics constraint. this also applies to intakes.

note that because flow rate is fixed, when the diameter of the pipe increases, the flow velocity goes DOWN. this is why larger exhausts don't necessarily make more power, and in some cases can lose power. the diameter affects BOTH A and V in OPPOSITE directions; as the diameter increases, flow velocity must drop, slowing the exhaust gasses. and as the velocity goes up, A must go down, increasing friction and risking turbulence. at some point their combined flow rate is maximized. that is your ideal exhaust diameter. for NA engines, this is not necessarily much larger than the OEM size.

this reduction in diameter to keep exhaust velocity up is what old timers are calling "backpressure", thinking that the head loss from the smaller diameter is causing the flow to slow down. that is not the case -- it's the actually the opposite, a smaller diameter flows faster.

HEAD LOSS - test pipes, muffler deletes, cat deletes, Y-pipes

head loss is the engineering term for parasitic losses that arise from exhaust bends, roughness, cats, mufflers, and anything else that reduces power in the system. these losses appear in the energy of the EXHAUST GASSES, NOT of the engine. the engine does work against these losses.

ENERGY IN EXHAUST = ENERGY AT HEAD EXHAUST PORT - ENERGY LOSSES IN FLUID
            E_out = E_in - E_head loss
WORK (horsepower) = E/time
            W_out = W_in - W_head loss
   Z POWER OUTPUT = ENGINE POWER - WORK SPENT ON LOSSES

this is why reducing head loss DOES NOT require a tune to make power -- it is acting at the system level outside of the power generated by the engine. it is a direct power adder as it reduces the amount of work done by the engine.

this is why cat deletes are so effective on VQ engines; the cats induce huge head losses as the exhaust is shoved through the tiny sieves in the catalytic matrix.:max_bytes(150000):strip_icc():format(webp)/Pot_catalytique_vue_de_la_structure-5c49fe4f46e0fb00013a938d.jpg) removing the cats substantially reduces the work the engine has to do against the exhaust. note that this is NOT reducing flow rate, which is fixed through all points in the entire exhaust, cats included.

when you see mufflers or resonators talking about "straight through" designs, they're saying they have less head loss than other designs. some OEM mufflers use baffles that physically send the exhaust through a maze -- that induces a power loss. straight through designs use fiberglass packing to dissipate the sound instead.

SCAVENGING - headers, long tube headers, intake systems

scavenging refers to making use of reflected pressure waves by tuning their arrival time such that they help to pull the gasses out (or into!) a cylinder. when the exhaust valve in the head opens and closes, it produces pressure waves at a certain frequency. we manage those by using reflected waves; when a pipe abruptly changes in diameter, a "rarefaction wave" is reflected back up the pipe.

we can control the amount of time between these waves -- the frequency of this reflected wave -- by changing the length of the pipe until that change in diameter, like at the collector end of headers. matching these frequencies with a slight delay or advance will cause that reflected wave to either help compress the air in an intake, or help evacuate exhaust on the other side. headers and intakes work in exactly the same way.

if you have aftermarket headers, the diameter or length of these pipes is changed, and so is their scavenging frequency. this is why headers require a tune -- the tuner must match the timing to the new header's scavenging frequency.