Why is this engine so great?
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SamNavy
New member
DOHC means Dual Overhead Camshafts.
Camshafts are turned off the crankshaft via a belt or chain. The camshafts actuate the valves that let air in and out of the cylinders.
The benefits to dual camshafts on a single cylinder bank are numerous, but basically boil down to better airflow in and out of the engine. Disadvantages are a more complicated system with more rotating parts vs. a SOHC (single overhead camshaft) engine. But if you don't know how a piston internal combustion engine works in general theory, then "better airflow" is a good enough explanation.
DOHC also makes it easier to run a Variable Valve Timing system, where the camshafts are adjusted to that they open the valves earlier/later based on rpm, which has huge benefits to making torque.
Learn how an typical car engine works here:
Internal combustion engine - Wikipedia, the free encyclopedia
The moving diagram on the right side about halfway down is actually of a DOHC engine. Notice that on the top of the engine, there are 2 rotating cams, one actuates the "intake valves" and the other actuates the "exhaust valves".
Compare that with this example:
HowStuffWorks "Internal Combustion"
You can see at the top that there is one camshaft actuating both sets of valves, making it a SOHC engine.
Camshafts are turned off the crankshaft via a belt or chain. The camshafts actuate the valves that let air in and out of the cylinders.
The benefits to dual camshafts on a single cylinder bank are numerous, but basically boil down to better airflow in and out of the engine. Disadvantages are a more complicated system with more rotating parts vs. a SOHC (single overhead camshaft) engine. But if you don't know how a piston internal combustion engine works in general theory, then "better airflow" is a good enough explanation.
DOHC also makes it easier to run a Variable Valve Timing system, where the camshafts are adjusted to that they open the valves earlier/later based on rpm, which has huge benefits to making torque.
Learn how an typical car engine works here:
Internal combustion engine - Wikipedia, the free encyclopedia
The moving diagram on the right side about halfway down is actually of a DOHC engine. Notice that on the top of the engine, there are 2 rotating cams, one actuates the "intake valves" and the other actuates the "exhaust valves".
Compare that with this example:
HowStuffWorks "Internal Combustion"
You can see at the top that there is one camshaft actuating both sets of valves, making it a SOHC engine.
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Carl_G
Member
Yes. I have a 2003 V8. I have driven a LOT of cars professionally and personally and have not experienced anything like this I-Force V8 with the 5 speed automatic. It's basically luxurious. I read a lot about it for a year while I was researching vehicles now I have one! Almost got a V6 but glad I got the V8.
Cars I've driven since I got my licence: 1977 Chev Impala V8, 1986 Chevrolet Firenza, 1989 Oldsmobile Cutlass, 1983 Chev Camaro
Z28 V8, Pontiac Firefly, Chevrolet Sprint, Geo Metro, 1997 Ford Taurus, 1996 Ford Windstar, 2003 Toyota 4Runner!
At work: Subaru WRX, Toyota Sienna, Nissan Altima, Ford Crown Vic, Chevrolet Lumina, Chevrolet Caprice, Ford Explorer, Chevrolet Tahoe, Volkswagen Jetta (car and station wagon) Toyota Camry, Nissan Maxima, Ford Exploreer Sport-Trac, Mazda MP-V, Mazda 6, Toyota Matrix, Dodge Caravan, Hyundai Santa Fe, Sonata, and the Hyundai minivan.
Cars I've driven since I got my licence: 1977 Chev Impala V8, 1986 Chevrolet Firenza, 1989 Oldsmobile Cutlass, 1983 Chev Camaro
Z28 V8, Pontiac Firefly, Chevrolet Sprint, Geo Metro, 1997 Ford Taurus, 1996 Ford Windstar, 2003 Toyota 4Runner!
At work: Subaru WRX, Toyota Sienna, Nissan Altima, Ford Crown Vic, Chevrolet Lumina, Chevrolet Caprice, Ford Explorer, Chevrolet Tahoe, Volkswagen Jetta (car and station wagon) Toyota Camry, Nissan Maxima, Ford Exploreer Sport-Trac, Mazda MP-V, Mazda 6, Toyota Matrix, Dodge Caravan, Hyundai Santa Fe, Sonata, and the Hyundai minivan.
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eskimochaos
Banned
Because its the same engine that went into a 75k Lexus
Its BEYOND over engineered as it was designed for the 100 series.
300k W/O issue is not uncommon with only regular oil changes.
It is far different than the variant found in the Sequoia + Tundra as its 100% Japanese with internals that are forged rather than cast.
Furthermore, V6 owners advocated that their's has a timing chain - yea thats great except a belt will keep the engine quieter + keep timing absolutely spot on for the lift of the belt. belts dont stretch, chains do.
I frequently drive around with the windows down when around town just to hear it. It may not rumble or snarl like some skyjacked F150's but when you feather the gas, and romp on it for that matter, you can tell there is something unique lurking underneath the hood.
Its BEYOND over engineered as it was designed for the 100 series.
300k W/O issue is not uncommon with only regular oil changes.
It is far different than the variant found in the Sequoia + Tundra as its 100% Japanese with internals that are forged rather than cast.
Furthermore, V6 owners advocated that their's has a timing chain - yea thats great except a belt will keep the engine quieter + keep timing absolutely spot on for the lift of the belt. belts dont stretch, chains do.
I frequently drive around with the windows down when around town just to hear it. It may not rumble or snarl like some skyjacked F150's but when you feather the gas, and romp on it for that matter, you can tell there is something unique lurking underneath the hood.
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Clean the sucker up while you're gawking :thumb3:
jpless
New member
I like my v6! Sometimes I wish I went with the v8 but whatcha gonna do. Wheres the v6 love? It may be louder but I rarely pay attention to it. Plus, if I throw my gibson muffler in there you won't even notice!
I don't know too much about the v6 vs v8 topic and frankly haven't looked into it much because it's not like I can swap out now! I'd be interested to know a bit more about the v6 and how long the aluminum will hold up. My 98 was great until 145k when first gear started slipping while towing. Found a v6 with everything I was looking for and couldn't pass it up.
I don't know too much about the v6 vs v8 topic and frankly haven't looked into it much because it's not like I can swap out now! I'd be interested to know a bit more about the v6 and how long the aluminum will hold up. My 98 was great until 145k when first gear started slipping while towing. Found a v6 with everything I was looking for and couldn't pass it up.
peter78
Super Moderator
Not sure which engine you are talking about, both the V6 and V8 have DOHC. I remember my first DOHC engine, a 1959 Jaguar. Back then DOHC was something special, now most of the engines have DOHC.
Jaguar XK6 engine - Wikipedia, the free encyclopedia
Jaguar XK6 engine - Wikipedia, the free encyclopedia
Carl_G
Member
V6 excellent
The v6 is excellent. It doesn't have that cool v8 sound but it gets slightly better mileage. I like the fact you can switch to 2 wheel drive. The oil filter is in a great location. It has a timing chain! No need for a $1000 timing belt at 90000 miles. My gf has a 2003 v6 and so far nothing but oil changes necessary.
The v6 is excellent. It doesn't have that cool v8 sound but it gets slightly better mileage. I like the fact you can switch to 2 wheel drive. The oil filter is in a great location. It has a timing chain! No need for a $1000 timing belt at 90000 miles. My gf has a 2003 v6 and so far nothing but oil changes necessary.
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SkylineGTRracer
New member
Get the APR X1 you'll smoke the V-8!:hungry:
Hey at least you picked the right truck. There's no better or worse engine
eskimochaos
Banned
From a technical engineering POV, the V8 is better.
Hey, thanks for the replies. I do have a V6 4L, not a V8. I test drove a V8, and it was great, could feel a bit of difference. But not too much for me any way. I love it. It is really quiet; my last car was a V6 Mustang and this engine is quite a bit smoother and more powerful. Think it was a 3.2L or something -- smaller. The DOHC explanation is interesting.
titaniumsport
New member
your mustang had 3.8L pushrod V6. i've had one and it is a great reliable engine.
i know what you mean about the smoothness difference between the 4Runner and mustang. the mustang's pushrod V6 is an old design going back to the late 70's/early 80's, not really a technological piece of engineering
i have a newer 2007 4.0 SOHC mustang as well and it is such a "harsh" feeling engine. very tractor-like.
I'm re-reading the links you put in about the OHV vs. OHC & DOHC trying to understand the engine, think I get it a little better. I ran across another animated comparison that's pretty good...
http://www.samarins.com/glossary/dohc.html
I like the thing about shooting a potato 500 feet.
Interesting about pushrod engines... that describes the Mustang, it was very solid -- never once stalled -- but not exciting to drive. The 4R is much more fun to drive. I find myself looking for errands to run.
http://www.samarins.com/glossary/dohc.html
I like the thing about shooting a potato 500 feet.
Interesting about pushrod engines... that describes the Mustang, it was very solid -- never once stalled -- but not exciting to drive. The 4R is much more fun to drive. I find myself looking for errands to run.
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