DOHC vs Push Rod

[ChrisV]

What about reliability? In both stock forms of each engine family wouldn't the xUZ's be a lot more reliable?

We'll have to see. Right now, GM is putting the all aluminum LS* series engines into sports and performance cars, not the kinds of cars that regularly see 400-500k miles ANYHOW, as they are not long distance, comfy cruisers.

But, pushrod Chevy engines have been happily powering cars for 50 years, and there are cars out there that old still on their original engine. So what they may not have proven in number of miles driven, they do in number of YEARS driven.

And we don't have any real stats on how 400+hp *UZ engines are going to last.

But also the aim for Lexus was to be a nice powered motor to complement the CAR. I think in the camero's and whatenot the car just complemented the ENGINE, in other words.... GM went for all motor no doubt, as lexus did not....

Well, you have to remember that the basic idea behind the domestic V8 was useabilkity in all SORTS of cars, from sports cars to sedans to trucks. And since few of the cars that were originally intended to use teh engine were exotic luxury cars, then it did compliment the nature of the cars it was in. And do you remember the '60s and '70s Lincolns and cadillacs? Pushrod engines of immense, effortless power that were totally silent and smooth. (in '70, the Cadillac 500 cid engine made 550lb ft of torque and almost 500 hp, with very little sound and perfectly smooth running, and that was with a carb and points-type dizzy)

Immagine if lexus/toyota made a 5.7 liter motor?

They do in teh trucks, ad it isnt' as powerful as teh Chevy. Remember what I said about hp/liter decreasinas displacement went up? That's what the Honda TYPE R 1.8 liter doesn't make the same hp/liter as their own 600cc street engines. If Toyota/Lexus made a 5.7 liter engine, it probably wouldn't make much more power than the LS* series, nor would it rev higher.

 

[svsgt1]

Well this discussion has of course sidelined into the chevy vs lexus thread, but that was expected. At least no one has started an arguing match. But there is no doubt that the lexus engine is built better then the Chevy engines, which is why they are more reliable. But I honestly don’t think that has anything (not much anyway) to do with the overhead cam vs the pushrod design of each engine. I think that really comes down to the tolerances of the components and assembly of the engine at the factory.



I’m glad to hear that others at least agree (in a sensible way) that push rods aren’t that bad and just American crap. I think that for street purposes there is probably little difference. Maybe in race conditions the overhead cams really make a difference. Obviously with F1 they need the 19,000 rpm limit so they use overhead cams. I’m sure if an F1 team choose to do so they could develop a pushrod engine that would be 16-17,000 rpm, but why do so when you could get that extra edge needed in racing. Anyway, I really wanted to see if there was a big limitation or whether it was purely preference. It seems to me that it is preference. I like the 1UZ in my car as it sounds awesome and is different, but unfortunately there is no aftermarket parts for it like there is for the Chevy’s. I guess I really want to be able to make a 500hp 1UZ and that is not really a possibility without forced induction or tons of money. I can’t even really go and buy one already built. As with the chevy engines you can go buy a 600-700hp monster for like $6000-7000, or build one yourself for much less. That is my two cents anyway. I would say both are great engines and both are very close in terms of actual use. Thanks for all the input. I’m sure this thread will continue to grow until people get tired of reading all of the arguments that will break out when the little kids get a hold of this one. Ha ha ha

 

[ChrisV]

Man, I hope the kiddies stay out of it, as it's anice, friendly discussion with no insults right now.

The comparisons between the *UZ and the Chevy arrive because they are an easy frame of reference. We could as easily use the Nissan, Porsche, or Mercedes OHC V8s in comparison to the Chevy and Ford ones, but it's just as easy to use what's in front of us.

And using those others we see that the Chevy compares pretty favorably. To go back the cheap fuel argument, yes, the 5.7 liter Camaro didn't get good fuel mileage at 345 hp vs a Honda I4, but it compares VERY nicely with a 5 liter DOHC Porsche V8, getting a bit more power and much better fuel mileage from a pushrod engine that has a bit more displacement but is physically much smaller and cheaper.

A similar comparison could be made with the BMW V8 and the Mercedes v8. How much "better" for their cost and complexity are they in terms of fuel mileage per hp? or power per dollar? Or any other method of comparison.

All these different engines we are discussing have their place. They are all merely different ways of getting the job done, and the fact that we HAVE the choice is what's important.

 

[Peewee]

I'm not sure about the local US cars, but our Aussie cars get their economy from rediculously low cruising revs.

The seem to sit on 1500-1700rpm @ 65mph.
The 1UZ is closer to 2300-2500rpm @ 65mph.

I'd love to see its economy with lower revs.
Maybe it would be worse? who knows.


And about motors getting bigger and hp/L getting smaller, the McLaren F1 road car does 103hp/L @ 6.1L
I do realise its not exactly comparing apples with apples comparing Chev to McLaren, but I'm just showing it can be done, and reliably at that. How long a McLaren motor will last for I have no idea.


One thing that hasn't been mentioned yet, is the benefit of DOHC that pushrods will never see.
This is VVTi.
VVTi can greatly increase the low down torque and power band, while not affecting the upper end in any way, shape or form.
It gives the benefit of having 2 different cams in the one motor.
This increases drivability greatly.



After I get my cams later this year, I'll take my car for a spin, then swap cars with a mate. He has a 450hp LS1, so we'll have about the same power.
I'll come back and comment on the driveability between the two.
Will be an interesting comparison me thinks.

 

[rarson]

hp/liter almost ALWAYS goes down as the displacement goes up.

But it seems as though this is a tradeoff with mpg. I mean, the 6.0L LS2 getting 20-some mpg, that's pretty awesome.

I don't think the issue with bottom-end on DOHC is due to cams or displacement, I think it is due to the 4-valves per cylinder. If there was a cam that would only open 1 of 2 intake valves per port at the low-end, I think we'd see stronger numbers. VTEC sort of does the same thing, but instead opens both valves with a smaller amount of lift. I think though, that only using 1 valve would produce better results. Just a wild guess.

 

[Trvln Nalzmn]

A 4.0L LS2 would get more than 20mpg. A 4.0L LS2 that had the same power as the 6.0L LS2 would not have pushrods. How much would it cost GM to make the 4.0L like that? Far too much.

When you think that GM try and save $1 per car because it works out to millions of dollars at the end of the day, until there is a real incentive for change nothing will happen.

 

[Zuffen]

Can you balance a coin on edge on an LSI or simillar from idle to max revs without it falling over or simply jumping off the engine?

Peewee sent a vid in of just that with his 1UZ.

It doesn't all come down to horsepower , torque or longevity. Smoothness has a lot to do with why quality auto makers use SOHC and DOHC engines.

Sophistication and smoothness don't go hand in hand with pushrods unless they are in your suspension.

Of interest Mercedes has moved to SOHC from DOHC as they can get what they want with 1 cam not 2. I run 2 Benz's in our houshold and they don't lack performance. We have 5 cars and 14 cams in our houshold. Not a pushrod to be seen.

 

[Murphy]

If there was a cam that would only open 1 of 2 intake valves per port at the low-end, I think we'd see stronger numbers. VTEC sort of does the same thing, but instead opens both valves with a smaller amount of lift. I think though, that only using 1 valve would produce better results. Just a wild guess.

The motorcycle version of VTEC (on the 800 Interceptor) does exactly what you describe.

 

[JBrady]

There is VVT (variable valve timing) which alters the opening and closing events of the valve. There is also VVA (variable valve actuation) which alters both timing and valve LIFT.

With VVA you can actually throttle the engine with valve actuation. BMW is doing this in an extremely complex way on their valvetronic engines.

This has tremendous potential as an engine can be run extremely smoothly at very low rpms, deliver a very good torque curve and have a great high RPM flow rate all with the same cam lobe!

A simple and IMO elegant approach is found here:

http://www.pattakon.com/vvar/index.html

I want to adapt this to an LSx engine. It would be trickier but not impossible on a xUZFE. Why this VERY creative individual does not have more attention is beyond me.

 

[JBrady]

Can you balance a coin on edge on an LSI or simillar from idle to max revs without it falling over or simply jumping off the engine?

Peewee sent a vid in of just that with his 1UZ.

It doesn't all come down to horsepower , torque or longevity. Smoothness has a lot to do with why quality auto makers use SOHC and DOHC engines.

Sophistication and smoothness don't go hand in hand with pushrods unless they are in your suspension.

Of interest Mercedes has moved to SOHC from DOHC as they can get what they want with 1 cam not 2. I run 2 Benz's in our houshold and they don't lack performance. We have 5 cars and 14 cams in our houshold. Not a pushrod to be seen.

Haven't seen that done on an LSx (or other pushrod engine) but it may be possible. NVH (noise vibration harshness) are easier to control in with a DOHC arrangement.

I will say that my 1996 LS400 engine was definitely smoother at idle than my 1999 LS400 with VVTi. The electronic throttle response on the 99 is also lacking in response and low speed smoothness. My buddies 1999 C5 Corvette also has an electronic throttle but the response is actually superior in many ranges. These are a couple of my very few gripes about my car.

Rod, as usual you bring up valid points. As you noted 4 valve per cylinder OHC engines have much less valve spring tension than 2 v/cyl OHV engines do to control the higher reciprocal weight. Reciprocal weight, deflection, requisite spring rate all create noise, harmonics and vibrations. But with VVA you reduce the lift at low RPMs dramatically. At idle the valves barely open. This would dramatically reduce the effect of the above.

With VVA it would be interesting to compare the idle smoothness and NVH of the 2v/cyl OHV that is only using .050" to .060" of lift at idle to the 4v/cyl OHC engine running .350". It would also be interesting to see the peak output of the same 2 engines with the OHV running 240 degrees duration and .600" lift vs. the OHC running 190 degrees duration and .350" lift. (both duration measurements at .050" lift)

 

[ChrisV]

And about motors getting bigger and hp/L getting smaller, the McLaren F1 road car does 103hp/L @ 6.1L
I do realise its not exactly comparing apples with apples comparing Chev to McLaren, but I'm just showing it can be done, and reliably at that. How long a McLaren motor will last for I have no idea.

You're definitely right about not comparing apples to apples, there, as the Mclaren't BMW sourced engine was a cost no object lesson in ultimate engineering, and part of why the car sold for a million bucks each! There's a reason it took a million dollar car to get a larger engine to put out a little less than the specific output of a bog standard street bike, and a QUARTER the hp/liter of a $100 R/C gas car engine.

It's really the exception that proves the rule.

One thing that hasn't been mentioned yet, is the benefit of DOHC that pushrods will never see.
This is VVTi.
VVTi can greatly increase the low down torque and power band, while not affecting the upper end in any way, shape or form.
It gives the benefit of having 2 different cams in the one motor.
This increases drivability greatly.

And it's one of the reasons I defend VTEC to guys on forums promoting American cars and saying it's nothing special. Even for those of us building Chevy and Fod (and Mopar) V8s, we had to compromise when choosing a cam profile, depending on whart we were primarily going to do with it. A high lift drag race cam made good upper end power, but made nothing below 3000 rpm. An RV grind made good low end power but fell off rapidly above 4000. A dual purpose cam lost some bottom end and didn't make all the top end. It would have been GREAT to have had a system that let you drive around on the stock cam at normal rpms and just about whan that cam fell on it's face, to automatically swap in a Comp Cams 292H for upper end power, then automatically swap teh stocker back in when we slow back down!

But, it's a misnomer to say that VTEC and VVTi increases low end torque. What it does is, unlike using just a power cam that makes upper end power and LOSES low end power, it allows teh engine builder to retain the low end power the engine would have been designed around having normally.

After I get my cams later this year, I'll take my car for a spin, then swap cars with a mate. He has a 450hp LS1, so we'll have about the same power.
I'll come back and comment on the driveability between the two.
Will be an interesting comparison me thinks.

Remember, many of us with 1UZs don't have VVTi, either, and for most of the decades of DOHC, that sort of tech wasn't available. What you do with VVTi won't have any bearing on what my DOHC 4 valve engine will do.

And you have to remember to compare gear ratios and car weight, too...

 

[ChrisV]

Can you balance a coin on edge on an LSI or simillar from idle to max revs without it falling over or simply jumping off the engine?

Peewee sent a vid in of just that with his 1UZ.

It doesn't all come down to horsepower , torque or longevity. Smoothness has a lot to do with why quality auto makers use SOHC and DOHC engines.

Sophistication and smoothness don't go hand in hand with pushrods unless they are in your suspension.

Of interest Mercedes has moved to SOHC from DOHC as they can get what they want with 1 cam not 2. I run 2 Benz's in our houshold and they don't lack performance. We have 5 cars and 14 cams in our houshold. Not a pushrod to be seen.

Do you even rememebr teh '70s Caddys and Lincolns with pushrod engines that made huge torque figures and you couldnt' hear or feel them running?

Sorry, there's more to it than that, too.

 

[JBrady]

It would have been GREAT to have had a system that let you drive around on the stock cam at normal rpms and just about whan that cam fell on it's face, to automatically swap in a Comp Cams 292H for upper end power, then automatically swap teh stocker back in when we slow back down!

Chris, check this out, a quote from the site
"That is why the VVA can combine idling at less than 300 rpm, with maximum power well above 10.000 rpm."

http://www.pattakon.com/vva/SideCam.htm

http://www.pattakon.com/

 

[Peewee]

After I get my cams later this year, I'll take my car for a spin, then swap cars with a mate. He has a 450hp LS1, so we'll have about the same power.
I'll come back and comment on the driveability between the two.
Will be an interesting comparison me thinks.

Remember, many of us with 1UZs don't have VVTi, either, and for most of the decades of DOHC, that sort of tech wasn't available. What you do with VVTi won't have any bearing on what my DOHC 4 valve engine will do.

And you have to remember to compare gear ratios and car weight, too...

I don't have VVTi on my 1UZ either.
It will just be a 1990 1UZ, with mild cams, extractors, twintake, tuning and manual.
The LS1 will be about a 2003ish, with the same mods (but stock intake manifold I believe)

Yes, I realise weight, gears all have there affect, but in the big picture, they have very little to do with driveability.

Mine will be a 5speed with 3.73 diff, and I believe his is a 6speed with 3.9ish diff.
He will have a weight disadvantage of about 300kg at a guess, but a torque advantage of 50% extra, and gearing advantage.

 

[JBrady]

I can't believe there are NO comments on the Pattakon VVA system.

With a little effort we could have TRUE infinitely variable valve actuation.

Honestly, I am not that impressed with my VVTi. With cams in the no overlap mode the intake closes WAY late and exhaust opens WAY early. With maximum overlap the opposite occurs, the intake closes too early and exhaust opens too late for high RPM power optimization. All the system does is change the phase between the two cams.

I would entertain replacing my system with this one. The trick on our engines is finding room between the lobe and valve for the VVA assembly. My thought would be a single lobe cam with the lobe between the valves.

Come on guys, think outside of the box here. Read the link.

 

[ChrisV]

Yes, I realise weight, gears all have there affect, but in the big picture, they have very little to do with driveability.

Well, it actually does, as lower toruqe figures would make an equal weight car have worse driveability, but if you weigh less, then that cancels out.

Anyhow, you have to remember that even though I defend pushrod engines as not being dinosaurs, I am replacing a fully functional american pushrod V8 with the Lexus DOHC engine... hehehehehe

 

[WDoherty]

JBrady, that site you found is quite interesting and i will have to read it through and through sometime. Are there any engines out there right now that don't use cams at all, and rather valve actuation via solenoid or hydrolic pressure? Anyway, back to the topic, i'm glad to see the most mature pushrod vs. dohc discussion ever, and the truth is modern counterparts of each design have their merits and are highly useful. I purchased my sc400 based on my history with toyota and the attractiveness of a 4 cam aluminum v-8. Truth be told the engine is smooth and somewhat powerful, but i drive my friend's lt-1 powered 6 speed camaro, and lust after that acceleration and power. I have been a toyota fan for a long time, especially the supra, but pushrod engines nowadays are very competitave with ohc engines. I drove an 01' chevy half ton truck the other day and i couldn't beleive the smoothness and power. It idled at around 500rpm and was just as smooth as my lexus. It definately had more throttle response, and that truck got about 20mpg, while my sc400 gets about 22mpg on premium. I believe that engine code is the LS4, which is 5.3L, 327 cubic inches, another member of the chevy GEN III family. I do like power, but that's not all i care about. In that case i would have bought an ls1 camaro, except the bodystyle and interior weren't what i wanted, and i generally don't like the kind of people that drive camaro's, sorry i shouldn't make an overgenerallized stereotype. Final point, i wish there was more aftermarket for the lexus, and yes it is sad that my yellow and cream 1977 chevy 1 ton van (400ci small block), could probably out accellerate from my quad cam v-8 coupe from 0-40mph.

 

[SpannersWatson]

Na ur al rong rotary is da best get a reel car GO ROTORZ lolol!!!111one!!!eleventyone1shift!2

 

[Kiwi.in.aus]

Purchase price ??

Hi all , I'm a new memeber on here so won't get into the technical stuff , but over here in Aus I can go down to my japanese importer and buy a Celsior/Crown front cut with a 1uzfe in it and worlds best auto with everything needed to make it run for $2500.00 , that give's me a relatively economical engine that has a forged steel crank cross drilled and webbed case's , forged rods and pistons making about 300 HP that will easily last 500,000 K's !!
And who cares if it only lasts 5 years as I can get a bare motor for $1200.00
Try and build a small block Chev motor for that !!
Ask a small block Chev owner what his steel crank cost him and thats just for an engine , add in the cost of an auto and fuel injection !!
Just down the road is the worlds best GT40 kit car builder and a second hand ford 4.6 quad cam motor is $8000.00 with limited supply !!
I won't get into if the Ford is better than the 1uzfe but it certainly won't be any better , plus factor into the equasion buying a system to run the injection and a front cut for $2500.00 is looking awfully good , that leaves about 6 grand to spend on the 1uzfe to come up to what the 4.6 Ford engine would cost .
There's a lot of dyed in the wool hot-rodders over here fitting 1uzfe engines in their early fords and chev's , a lot of it being cost and the other bit is they will pass emission tests .
And most of them are also using the auto's and those that really want a manuel are fitting manuel aftermarket valve bodys .
Some of them a running twin turbo's with up to around 800 HP plus with out touching the bottom end !!
It's pretty hard to beat the word's best production v8 in a front cut for $2500.00 , even if it is "only" a 4 liter .

 

[svsgt1]

Kiwi,

Here is the US it is the exact opposite as you describe. We can get small block chevy's for extremely cheap. (We can buy 1UZ's for cheap too but the Chevy's are even cheaper.) You can build a monster Chevy for much cheaper then you can a 1UZ here is the USA. I guess that is because we have so many small block Chevy's that have been made over the years.