Alfa (SOHC) vs Everyone Else (DOHC)

"K-Roll-PorscheTamer" (k-roll390) 03/15/2018 at 21:56 • Filed to: Alfa Romeo, Engine Talk

1

37

So I just found out that the 2.0L 276hp/300tq in the mid-range Giulia uses SOHC?? I’m pretty sure FCA is the only major company still using it, but why?? It’s four valves per cylinder, but what advantage could SOHC have over DOHC to retain it?

E90M3 > K-Roll-PorscheTamer 03/15/2018 at 22:08

13

FCA: if it’s broke, don’t fix it.

Spanfeller is a twat > K-Roll-PorscheTamer 03/15/2018 at 22:12

1

I mean, the LS only use two valves so it’s not unheardof...

Maybe it’s the new multiair2 vvt system; maybe it doesn’t fit with 4 valves, or it’s so good that 4 valves are not needed.

Highlander-Datsuns are Forever > K-Roll-PorscheTamer 03/15/2018 at 22:13

1

How does that even work? I think subaru engines are SOHC too, and they are also 4v heads.

Jordan and the Slowrunner, Boomer Intensifies > K-Roll-PorscheTamer 03/15/2018 at 22:14

6

If it’s Multiair, it’s fairly high tech actually. IIRC, the intake valves are hydraulically actuated.

Spanfeller is a twat > Jordan and the Slowrunner, Boomer Intensifies 03/15/2018 at 22:17

1

it is multiair, alike the ingenium system JAAAAAAGGGGG uses

Jordan and the Slowrunner, Boomer Intensifies > Spanfeller is a twat 03/15/2018 at 22:17

0

Which they got from Fiat.

Spanfeller is a twat > Jordan and the Slowrunner, Boomer Intensifies 03/15/2018 at 22:18

1

The patent is not Fiat’s as far as I know it’s an independent company that license the tech to both...

K-Roll-PorscheTamer > Highlander-Datsuns are Forever 03/15/2018 at 22:19

0

I wanna know how it works too. The current FA Subaru engines are DOHC.

Jordan and the Slowrunner, Boomer Intensifies > Spanfeller is a twat 03/15/2018 at 22:20

0

Ah

MrDakka > K-Roll-PorscheTamer 03/15/2018 at 22:21

6

Instead of breaking down every 1000 miles with DOHC, they now beak down every 2000 miles with SOHC?

Textured Soy Protein > K-Roll-PorscheTamer 03/15/2018 at 22:22

3

Most Honda V6s are SOHC.

Spanfeller is a twat > Jordan and the Slowrunner, Boomer Intensifies 03/15/2018 at 22:23

0

Its neither! It’s a German company called Schaeffler

Textured Soy Protein > Highlander-Datsuns are Forever 03/15/2018 at 22:24

2

Honda SOHC 4v head with the valve cover off:

Highlander-Datsuns are Forever > K-Roll-PorscheTamer 03/15/2018 at 22:25

2

They use a forked rocker arm that can operate two valves at the same time, the valves are not being directly actuated by the cam lobes.

Highlander-Datsuns are Forever > Textured Soy Protein 03/15/2018 at 22:28

0

I see, just use a crap ton of rocker arms.

nFamousCJ - Keeper of Stringbean, Gengars and a Deezul > Spanfeller is a twat 03/15/2018 at 22:31

0

Same group that developed for Jag. Schaeffler Group as per Wikipedia.

I always thought the multiair was closely related to, or patented by Sir Koenigsegg himself. But his camless engine is different /unrelated.  

K-Roll-PorscheTamer > MrDakka 03/15/2018 at 22:34

1

The math checks out.

K-Roll-PorscheTamer > Spanfeller is a twat 03/15/2018 at 22:35

0

Is the Ingenium SOHC as well?

AestheticsInMotion > E90M3 03/15/2018 at 22:36

2

If it ain’t broke, fix it ‘till it is!

Textured Soy Protein > Highlander-Datsuns are Forever 03/15/2018 at 22:37

1

Well it’s the same number of rockers as a DOHC head, just they’re all actuated by 1 cam. This is a SOHC VTEC cam:

Spanfeller is a twat > nFamousCJ - Keeper of Stringbean, Gengars and a Deezul 03/15/2018 at 22:38

0

I’ve seen the patent, it’s a beautiful arrangement of pneumatic lines which I hope never fail... :/

BlueMazda2 - Blesses the rains down in Africa, Purveyor of BMW Individual Arctic Metallic, Merci Twingo > E90M3 03/15/2018 at 22:38

0

Can I call tomorrow’s COTD yet?

This is my nomination.

Spanfeller is a twat > K-Roll-PorscheTamer 03/15/2018 at 22:40

0

Wikipedia says it’s a DOHC driven by CHAINS.

It’s kinda asthmatic though, two turbos in and vvt for intake and exhaust just renders their engine at 250hp! with that tech and turbo grunt I bet they could have it go to 300 or more!

Highlander-Datsuns are Forever > Textured Soy Protein 03/15/2018 at 22:50

0

My knowledge of head design is limited, I’m used to seeing direct actuating cam shafts like the L24 on nissan’s. This is also the only engine I’ve ever disassembled and reassembled in my life.

JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t > K-Roll-PorscheTamer 03/15/2018 at 23:00

0

Alfa never does anything the easy way. Remember the Busso V6, a hemispheric combustion chamber engine with central mounted spark plug and an over-square geometry was SOHC. How you ask? The cam actuated the intake valves directly and lateral push rods ran across the head to rockers that actuated the exhaust valves.

Why they did this? Fuck if I know, but it wasn’t until the final years of production that the Busso got DOHC. I do believe the 2.0 in the Giulia uses Multi-Air, which has a valid reason for being SOHC, but is no less bizarre for it.

Textured Soy Protein > Highlander-Datsuns are Forever 03/15/2018 at 23:00

0

This is the old-school VTEC (not i-VTEC) in the D-, B- and H-series motors:

D-series is SOHC and B- and H-series are DOHC.

The D-series VTEC cams have 5 lobes and rocker arms per cylinder, where there’s the high RPM lobes for the intake side only.

The B- and H-series cams have 6 lobes and rocker arms per cylinder, with each cylinder getting 3 lobes and arms per cam.

The non-VTEC engines in these series of motors have 1 rocker arm per valve, regardless of number of cams.

I assume most other similar 4v engines both DOHC and SOHC have at least 1 rocker arm per valve unless they’re doing something funky like VTEC.

Cé hé sin > Spanfeller is a twat 03/16/2018 at 05:58

0

Nobody’s ever heard of Schaeffler but they’ve got parts in just about every car around.

Long-Voyager > K-Roll-PorscheTamer 03/16/2018 at 07:32

0

276hp/ 300tq

This is why they stay SOHC. SOHC engines generally make more torque than DOHC engines of the same power level. More torque makes a car quicker, easier to drive, and generally more fuel efficient.

404 - User No Longer Available > K-Roll-PorscheTamer 03/16/2018 at 07:35

0

Honda R engine in 1.6 and 1.8 forms still use SOHC, in the current gen Civic.

Simplicity and cost, I suppose.

404 - User No Longer Available > Spanfeller is a twat 03/16/2018 at 07:38

0

Not just alike, but the same system indirectly licensed.

From Wikipedia:

“Multiairwas licensed to the Schaeffler Group in 2001, which also markets the system as Uniair [3] — who in turn began supplying Uniair systems in 2017 to Jaguar Land Rover , branded as Ingenium technology”

You can tell a Finn but you can't tell him much > K-Roll-PorscheTamer 03/16/2018 at 09:47

0

SOHC actually has a lot of advantages over DOHC. It is marginally lighter, has slightly less friction, only one cam to mistime, is easier to assemble, and much cheaper to design and manufacture than DOHC.

nFamousCJ - Keeper of Stringbean, Gengars and a Deezul > Spanfeller is a twat 03/16/2018 at 14:40

0

Well that’s disappointing. Though I’m not sure how well electric actuators would be able to handle the heat. Unless maybe an electric actuator : pushrod setup.

Spanfeller is a twat > nFamousCJ - Keeper of Stringbean, Gengars and a Deezul 03/16/2018 at 14:59

0

Well... Also air density might be an issue... Here in Mexico City, compressing air is a bit harder....

Variance > 404 - User No Longer Available 03/16/2018 at 21:35

0

This man has it correct, the Multiair system was originally developed by Fiat and first used in the TwinAir and FIRE engines. The technology was later licensed to Schaeffler, who currently supplies the multiair units used in the Tigershark and Hurricane (the engine used in the Giulia).

Multiair engines have a single camshaft on the exhaust side of the cylinder head, and each cylinder has a 3rd lobe that drives the intake valves through the multiair unit.

404 - User No Longer Available > Variance 03/16/2018 at 21:54

0

I didn’t have it correct, Wikipedia did, lol.

Matt > Highlander-Datsuns are Forever 07/22/2020 at 18:27

0

Indeed, like a Truimph Dolomite

Matt > E90M3 07/22/2020 at 18:28

0

The thing is, Alfas have been DOHC for years. The mid-90s was the last time they had a SOHC engine, in the 12V versions of the V6.