rarson
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Toysrme said:
:laugh2:
That's awesome...
DOHC vs Push Rod
- Thread starter svsgt1
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The 1UZFE EGR Delete Kit is available for sale here.
:laugh2:
That's awesome...
And I've had to replace cam followers in DOHC engines many times.
Oh, and OHC makes for a physically larger, more complex, and more expensive package when new. That does make a difference.
I still LIKE DOHC engines like the 1UZ and my Fiat and my old Jags. But this fanatical, quasi-religious worship of what is merly a different way of exploding dead dinosaurs, is just silly sometimes.
A great example of this is the 4.6L modular Ford V8 compared to the 5.0L small block. HUGE difference in size, much more displacement options (though this is because Ford chose a poor bore spaceing for the 4.6), and obviously more complex.
Going old school again...Some of these older threads hold some good gems...
Alot of talk about Fords in recent posts, and yes the Saleen S7 has been overlooked some... It is a car that goes 0-60 in under 3 seconds...It's rediculous.. Very comparable to the LS7 Vette that is a very impressive ride...
I still don't understand exactly how the DOHC motor operates without pushrods?...I will try and re-read this thread and get a grip.. I grew up only working with big pushrod V8's. I never ventured into the smaller DOHC motors...Never took the time to learn about them...Are they worth while? I do understand the Dohc motors rev higher which would be better suited for the smaller motors to produce more power...
Are there any DOHC V8's?
Jibby, go outside to your car and lift the hood. You see the plastic cover on your engine that says "V8 Four Cam 32"? That means it's a DOHC V8.
If you pop one of the valve covers off, you'll see two camshafts sitting there. Because there's an intake AND an exhaust cam for each bank, it means it's a DUAL OHC engine. I also have a V12 BMW motor that is a SOHC engine, with only one cam for each bank.
The reason DOHC motors are so cool is that the cams ride on top of the lifters and operate the valves directly, so there's very little wasted motion or mechanical linkage like there is with pushrods, rocker arms, etc.
:laugh2:
That's awesome...
ChrisV
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YOu don't need a lot of valves if you don't need to go over 9000 rpm (since 2 valve street pushrod engines have been known to rev that high with regularity). You don't really need a lot of bandaids for replacing low end power like variable valve lift and timing of you start with a larger engine.
And I've had to replace cam followers in DOHC engines many times.
Oh, and OHC makes for a physically larger, more complex, and more expensive package when new. That does make a difference.
I still LIKE DOHC engines like the 1UZ and my Fiat and my old Jags. But this fanatical, quasi-religious worship of what is merly a different way of exploding dead dinosaurs, is just silly sometimes.
rarson
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ChrisV said:
A great example of this is the 4.6L modular Ford V8 compared to the 5.0L small block. HUGE difference in size, much more displacement options (though this is because Ford chose a poor bore spaceing for the 4.6), and obviously more complex.
jibbby
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Going old school again...Some of these older threads hold some good gems...
Alot of talk about Fords in recent posts, and yes the Saleen S7 has been overlooked some... It is a car that goes 0-60 in under 3 seconds...It's rediculous.. Very comparable to the LS7 Vette that is a very impressive ride...
I still don't understand exactly how the DOHC motor operates without pushrods?...I will try and re-read this thread and get a grip.. I grew up only working with big pushrod V8's. I never ventured into the smaller DOHC motors...Never took the time to learn about them...Are they worth while? I do understand the Dohc motors rev higher which would be better suited for the smaller motors to produce more power...
Are there any DOHC V8's?
(just remember this is all in good sarcastic fun) But dude, you just posted a question that is quite funny about if a DOHC V8 exists on a 1UZ forum. The lexus V8s are DOHC (or at least the ones that started this forum 1UZFE, etc) The company that builds the Radical also makes their own DOHC V8 but it is more like a custom block with Hyabusa (can't spell internals. I think they are called RPE, but not sure. But have fun researching as it is lots of fun. lol
Later,
Adam
Later,
Adam
DOHCs are worth while if you have the right displacement and cam profile. for example, the new 6.2L MB V8 makes 500 HP, same as the LS7, but with .8L less displacement. the torque is a bit less than what the LS7 makes, but that doesn't really mean anything, as it still has tons of torque. all in all, DOHC(or 4 valves in general) flow more air per mm of lift than the equivalent OHV design. the example is back the to LS7 vs. 6.2L MB V8. the MB V8 needs less lift to make the same HP, even with less displacement. i hope that makes sense to you Jibbby.
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Jibby, go outside to your car and lift the hood. You see the plastic cover on your engine that says "V8 Four Cam 32"? That means it's a DOHC V8.
If you pop one of the valve covers off, you'll see two camshafts sitting there. Because there's an intake AND an exhaust cam for each bank, it means it's a DUAL OHC engine. I also have a V12 BMW motor that is a SOHC engine, with only one cam for each bank.
The reason DOHC motors are so cool is that the cams ride on top of the lifters and operate the valves directly, so there's very little wasted motion or mechanical linkage like there is with pushrods, rocker arms, etc.
V8Datto
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I thought DOHC engines could rev harder easer due to the fact that the cam was directly above the valves. thus meaning there is no weight in the valve train.
Push rod engines need lifters rockers, ect, ect and the cam is low down in the V of the engine. This meant there is a lot more weight in the valve train and couldn't rev up into the high rpm with out valve overlap.
Push rod engines need lifters rockers, ect, ect and the cam is low down in the V of the engine. This meant there is a lot more weight in the valve train and couldn't rev up into the high rpm with out valve overlap.
there is always weight in the valve train, but i see your point. OHC engines are easier to rev than OHV engines, in general. but there are also many more variables than the valve train that makes an engine easy to rev. for example, friction on the bottom end, stroke length, rod length, piston weight etc. etc.
for both types of engines, the lighter the part, the easier you can make it spin very fast. there are a few other types of motion in an internal combustion engine that apply also, but i forgot them...
for both types of engines, the lighter the part, the easier you can make it spin very fast. there are a few other types of motion in an internal combustion engine that apply also, but i forgot them...
jibbby
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Learn something new everyday people, that is what makes life so good and refreshing...I thought that I might get roasted for asking that question and I was almost right... You guys took it easy on me on this one actually...
I now understand DOHC thanks...For some reason I was thinking there was no cams with lobes in the DOHC motors, no rods, lifters etc...Just spring load or something to open and close the valves... I just couldn't grip on how the valves would open and close with a no cam motor... I was thinking an electronic open and shut system to some effect... Now I surely I will get roasted...
I didn't think our dual overhead cam Xuz's qualified for the DOHC label...I am actually fully aware of how the Xuz-fe motors are designed and operate from top to bottom..
Are you guys sure our Xuz-fe motors are labeled as DOHC motors? That's crazy if so, and don't I feel like the jackass if that's the case....
I now understand DOHC thanks...For some reason I was thinking there was no cams with lobes in the DOHC motors, no rods, lifters etc...Just spring load or something to open and close the valves... I just couldn't grip on how the valves would open and close with a no cam motor... I was thinking an electronic open and shut system to some effect... Now I surely I will get roasted...
I didn't think our dual overhead cam Xuz's qualified for the DOHC label...I am actually fully aware of how the Xuz-fe motors are designed and operate from top to bottom..
Are you guys sure our Xuz-fe motors are labeled as DOHC motors? That's crazy if so, and don't I feel like the jackass if that's the case....
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Clipped from Toyota's tech literature
I would like to point out the MB 6.2 vs the LS7 that the LS7 actually makes quite a bit more then the 505hp it says it does. Many people have dynoed a totally stock C6 Z06 and got 485 hp at the wheels. This is about 550-570 hp at the crank which is quite a bit more then advertised. (On a side note a tune and air filter gets you 500-515 hp at the wheels) I don't know what a stock MB 6.2 gets in reality as it may get more. There is no doubt that 4 valves per cylinder is better. Another interesting point is that the BMW 5.0L V10 gets 500hp stock and the Porsche 5.7L V10 makes 605hp. But those engines are tuned a bit more hardcore then the LS7 but the power to displacement is still very impressive.
jibbby
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Well I guess that clears things up...Thanks Cribbs, the 1uz-fe motor is a DOHC motor for sure.... Man, I really thought only the smaller motors like Honda, etc..were DOHC... It all makes sense now, thanks.....
SV - The LS7 and AMG MERC motors are all boosted motors as you state... I still think you can get alot of pop out of the older cheap push rod big block Chevy and Ford motors...The GM 454, 572 crate, 460 Fords... Even carb'd they can still crank out 500bhp or so... You may need a double carb setup but they can still get it done for big old heavy iron block motors...Get those big blocks adapted with fuel injection and huge flowing injectors and you really got something going on.. It's too bad those big iron blocks would really test out mostly any front suspension to the max on just about any car swap..
Floating valves on the push rod motors is crap at higher rpm's...That's really the only big advantage DOHC has over the classic pushrod motors..I mean really how much hp do you save by not having the extra load on the cams? I don't think that much, but then again I've been wrong before...
SV - The LS7 and AMG MERC motors are all boosted motors as you state... I still think you can get alot of pop out of the older cheap push rod big block Chevy and Ford motors...The GM 454, 572 crate, 460 Fords... Even carb'd they can still crank out 500bhp or so... You may need a double carb setup but they can still get it done for big old heavy iron block motors...Get those big blocks adapted with fuel injection and huge flowing injectors and you really got something going on.. It's too bad those big iron blocks would really test out mostly any front suspension to the max on just about any car swap..
Floating valves on the push rod motors is crap at higher rpm's...That's really the only big advantage DOHC has over the classic pushrod motors..I mean really how much hp do you save by not having the extra load on the cams? I don't think that much, but then again I've been wrong before...
