A few motor questions (UPDATE TO OP, mod plz sticky)

[Famine]

I don't know what that means, precisely. From what I can tell, you could opt for the Nissan's DOHC engine and have the best city fuel economy and tie for greenhouse gas emissions, or you could opt for GM's "antiquated" V8 which does everything as well or better (save city fuel economy) than the fancy-schmancy DOHC-job, including over 100 more ponies to play with.

Spearman's Rank says that the GM V8 doesn't, in fact, do everything "as well or better". Spearman's Rank says that the Nissan 350Z does everything "as well or better".

It helps, when you post statistics, that you can interpret them correctly.

So, which cars did this mythical 4.0L OHV V8 appear in? (emphasis on the sixes above )

I'm sorry? Who said anything about a 4.0 OHV V8? I mentioned that the Australians take OHV V8s from their parent companies and develop them into OHC V8s. I ALSO pointed out that, contrary to your claim of:

(there hasn't been a single Ford or GM engine reworked from OHV to OHC by their respective Australian subsidiaries)

The Typhoon/Falcon use a reworked OHC 4.0 6 based on the Ford parent company's OHV 4.0 6. So in fact there HAS been at least one Ford or GM engine reworked from OHV to OHC by their respective Australian subsidiaries.

The ones I've talked to agree that specific output is advertising fluff for the most part. I've also consulted myself on the subject. Coincidentally, I agreed with myself. Although I'm still a mechanical engineering student who probably doesn't know as much about mechanical engineering as someone with a B.Sc. and M.Sc. in molecular biology and genetics and human genetics and disease, respectively.

Hey! You can name my degrees! Good on you! What relevance does this have?

Student = someone who studies.

Now, who is talking about "specific output" on its own? My statement is:

"Pushrod <- SOHC <- DOHC. DOHC can produce more power and more torque per unit displacement more efficiently and more reliably."

If you disagree with that you are, frankly, wrong. All that the random examples you picked out of the air show is that some pushrods produce more power than some DOHCs and some pushrods have a better fuel economy than DOHCs - showing a remarkable lack of understanding, for a mechanical engineering student, of the word "efficiency".

All power output is, to use your phrase, "advertising fluff". Why would Chevrolet post "400" horsepower if not to use that nice, big, round number. But you're just NOT getting it. DOHC CAN produce more power and more torque per unit displacement more efficiently and more reliably than OHV. Some manufacturers choose not to take advantage of the "more power" or "more torque", but instead take advantage of "more efficiently" and "more reliably". Some manufacturers choose to do it the other way round. Some manufacturers choose to use OHVs instead - although rarely in Europe. None of this alters the basic fact that the DOHC is more capable of producing more stuff better.


Out of interest, seeing as you're a mechanical engineering student, what is the throttle response like on a typical OHC compared to OHV? Just out of curiousity (not fishing) since I don't actually know.

 

[Slicks]

Hmm... I find it interesting how a Corvette (actually 2 Corvettes, an '04 Z06 and an 05) with a pushrod engine is lighter than all of the cars on the list, save for one Ferrari.

One point that none of you have brought up is engine longevity. Many pushrod engines (large V8's in particular) are relatively understressed engines. A low-stress engine (Say, a 405hp 5.7L V8) will far outlast a 3-4L, 400hp high-stress Ferrari engine under similar conditions. Or a Ford 4.6. Or a Nissan VQ-series engine.

There are many pushrod engines (Chevy 5.7 and 3.8 in particular, because of their widespread use) that have many, many miles on them. There is one documented 5.7 with over 1,000,000 KM on it featured on Motoring 2004 (Canadian TV show). And there are probably more that are undocumented.

Pushrod engines are simpler, and thus easier to fix. There are generally a wider variety of parts available to the pushrod engine (350, etc) at cheaper prices. They also have far more tuning potential. There are many more 600+HP smallblock Chevys running around than anything else.

Furthermore, guess what engine configuration is used in the vast majority of professional drag racing cars? Pushrod. I do not know of a single _OHC engine producing the 8,000HP of a top fuel dragster. They are all pushrod.
In fact, I challenge anyone here to find a NON-OHV engine (excluding aeromotive applications such as turbine) producing over 2,000 hp.

 

[Jay]

Why dont we all buy rotory engined cars and call it a day

 

[inferno]

what is the throttle response like on a typical OHC compared to OHV?

No much difference really. I've at least had the privalage of driving a variety of engines if not owning any. From the 4.0 liter OHV V6 in my dads ranger, to the 2.2 liter SOHC I4 in my moms accord. Also a jeep wrangler with it's 4.0 liter inline 6, OHV I belive, A nice 3.1 liter OHV V6 in a no longer possesed, Buic Regal and my little cuarberated, SOHC 2 valve pulsar. the one thing I can say is that both the Ranger and wranglers OHV engines dont like to rev. You get alot of vibration if you wind either of them past 4000 rpm. As for throtle response? no diference from the accord to me. Their is alot of extra oscelating weight and friction their with the pushrods, rocker arms and whatnot, but most SOHC 4 valve engines use rocker arms too and after you go adding in the extra valve springs, and stuf for twice the number of valves, power losses to the valvetrain would probably be very similar. Unfortunately the pulsar was carburated so natuarly it's throttle response sucked, and i cant do an unbiased comparison of OHV 2 valve versus SOHC 2 valve. the one stand out from the group however is the 3.1 liter OHV in the regal. that thing was down right snappy. Excelent throttle response, better than all the others and it didnt mind revving either. Plus the muffler was gone so it sounded sweet. God I wanted that engine in something with 2 doors. But back on topic. I attribute the dislike of revving more to the size of the big ford V and jeep inline sixes rather than the valvetrain. That being said their was never a need to go past 3K rpm with either of them. sorry for the essay.

 

[Slicks]

The throttle response of an engine would depend more on the intake system than on the valvetrain. A carbuerated engine with a poorly tuned carb will likely result in poor engine response. A properly tuned carb will give fast response, and fuel injection the fastest.

I doubt that a difference in valvetrains (between OHV, OHC) would make a difference in response. However, a OHV engine with rollerised valvetrain would likely be faster to respond than one with a non-rollerised valvetrain.

 

[Azuremen]

Its interesting as well when you look at power for displacement. I have an MR2. With a 1.6L 5 Valve per cylinder DOHC engine. With a Variable Valve Timing system.

It makes 190 HP. The Corvette makes, what, 400 HP? Outa of what? 5.7 liters? Damn. If I had that big of an engine developed with similar techinques as my Toyota's engine, I'd at LEAST have 600 HP. Mind you, I haven't done anything to the engine itself.

Hey Famine, can Pushrod engines support a Variable Valve Timing system of any sort? Cause I know that helps quite a bit on efficency as well.

Pushrod engines are still used because they are mechcanical less complex than a DOHC engine. And its the "American" thing to have. Or some crap.

 

[Famine]

One point that none of you have brought up is engine longevity. Many pushrod engines (large V8's in particular) are relatively understressed engines. A low-stress engine (Say, a 405hp 5.7L V8) will far outlast a 3-4L, 400hp high-stress Ferrari engine under similar conditions. Or a Ford 4.6. Or a Nissan VQ-series engine.

Mazda's K-series V6 has been benchtested to 340,000 miles with only oil changes at manufacturer intervals with no breakdowns. Original factory machining was still in evidence when the engine was examined.

The most reliable "brands" available on the UK market are all OHC-based - Subaru, Toyota/Lexus, Honda, Mazda. The least reliable are all OHV-based - Land Rover, TVR (although TVR are often excluded since they're low volume). The exceptions are FIAT/Alfa, but due to the comical approach of Italian manufacturers to electronics.

Pushrod engines are simpler, and thus easier to fix. There are generally a wider variety of parts available to the pushrod engine (350, etc) at cheaper prices. They also have far more tuning potential. There are many more 600+HP smallblock Chevys running around than anything else.

Furthermore, guess what engine configuration is used in the vast majority of professional drag racing cars? Pushrod. I do not know of a single _OHC engine producing the 8,000HP of a top fuel dragster. They are all pushrod.
In fact, I challenge anyone here to find a NON-OHV engine (excluding aeromotive applications such as turbine) producing over 2,000 hp.

Granted, if you want MASSIVE power you want something that will be easy to fix when it - and it will - blows. But where's the driveability? What's the highest-power street OHV? The highest-power street OHC I can think of is a 1280hp Skyline.

Out of curiousity, what's used in F1 - where power/weight and power/litre matters most? Although their reliability is measured in hundreds of miles (if that), but they're running at rpms pushrods can only dream of.


As I said earlier on however you want to get power out of a car, or wherever you want to build it - I don't care if it's a good car. But, on mechanical principles, OHC can produce more power and torque per unit displacement more reliably and more efficiently than OHV can.


Azureman - No idea. Firebird may know though.

 

[TheCracker]

One point that none of you have brought up is engine longevity. Many pushrod engines (large V8's in particular) are relatively understressed engines. A low-stress engine (Say, a 405hp 5.7L V8) will far outlast a 3-4L, 400hp high-stress Ferrari engine under similar conditions. Or a Ford 4.6. Or a Nissan VQ-series engine.

Do you think Ferrari or Ferrari owners are bothered about getting high-milage on their engines?

I bet most Ferraris do less than 8000 miles a year. i doubt many ferraris have 100,000 on the clock if any. Those engines are just not designed for high milage so comparison is mute.

Furthermore, guess what engine configuration is used in the vast majority of professional drag racing cars? Pushrod. I do not know of a single _OHC engine producing the 8,000HP of a top fuel dragster. They are all pushrod.
In fact, I challenge anyone here to find a NON-OHV engine (excluding aeromotive applications such as turbine) producing over 2,000 hp.

Top fuel dragsters are a crap comparison because guess what? - they run on 'top fuel' ie Nitromethane not pump fuel.

Dragsters that run in the 'pump fuel' classes have outputs of no more than 1350bhp - from 8.2ltrs

A Formula 1 engine has an output of around 950bhp (a conservative guess) from 3ltrs
Theoretically a 8.2ltr F1 engine would output 2600bhp on pump fuel. Thats without Turbos or Superchargers.

They just don't bother producing huge capacity OHC engines because they can get the same power from a lower capacity.

 

[Nasadus]

I have a motoring related question myself and i don't want to make a new thread just for one question so i'll ask it here.

If a vehicle with a 500BHP engine were to race (in a straight line) against the same type of vehicle wich has 2 250BHP engines,wich one would win?Or wich one would reach a higher top speed?

I know it sounds silly but i have to know.

 

[TheCracker]

I have a motoring related question myself and i don't want to make a new thread just for one question so i'll ask it here.

If a vehicle with a 500BHP engine were to race (in a straight line) against the same type of vehicle wich has 2 250BHP engines,wich one would win?Or wich one would reach a higher top speed?

I know it sounds silly but i have to know.

Theres too many variables like:

weight,
aerodynamics,
traction (i presume the twin engined car is awd)
actual power at the wheels (a twin engined car has 2 sets of transmissions/drive trains to sap power)
gearing...

To give a straight answer.

If you were to say that both cars weighed the same, had the same amount of aerodrag, transmitted the same amount of power on to the road & both were AWD and geared the same then theoretically they would reach the same top speed at the same time.

 

[///M-Spec]

Before this thread degenerates into a pushrod vs. OHC war, let's all step back and gather the facts.

Pushrod (OHV) Pros: compact, relative simplicity

Pushrod (OHV) Cons: comparatively poor high RPM performance, is variable timing even an option?

(D)OHC Pros: good high RPM performance due to more valves and better positioning of the valves, variable valve timing easy to implement

(D)OHC Cons: packaging, complexity

Feel free to point out anything if you disagree with this list.


Despite my personal perference to own cars with DOHC engines (I like the high end power delivery and mechanical noises that comes with it), I don't think anyone in his right mind would critisize the LS2 V8 for being a bad design. Despite the 6.0 liter displacement, it is a light, compact and simple engine that makes a lot of power.

If you compare the LS2 to the S54 in the BMW M3, you'll notice while the LS2 is wider, it is shorter in height and length. You will also notice the LS weighs almost the same as the M3 motor (they are less than 50 lbs apart), yet makes a great deal more power (400 vs. 333). These are in comparatively priced cars.

(If anyone has weight and size info on a Nissan VQ 3.5, I'm very interested in seeing it.)

I don't you know about you, but "power per liter" doesn't have any consequence to me in a performance car. It doesn't DO anything. I don't drive "power per liter".

To me, the ONLY things that matter is power output (specificly, the shape of the torque curve), how much the engine weighs and how it room it takes up; fuel efficiency and reliablity being secondary concerns. Well it needs to sound good too, but I digress.

That being said, I fully acknowledge that in many countries, cars are taxed based on displacement. Therefore while specific power is fairly meaningless to me, it may be very meaningful to someone in another country.

Perhaps that is why the Japanese and Europeans seem to have "a thing" for specific power.

The second thing I wanted to say was that the Ferrari F430 vs. GM Gen IV V8 comparison is not very useful. No one is taking price into consideration; you can buy almost 4 C6 Vettes for the same price as an F430. Price independant, sure the Ferrari's motor may be superior, but when was the last time you bought ANYTHING price-no-object??

Now that I've made it clear my admiration of the GM Gen IV V8... I'm hoping someone can explain to me why the 3800, OTOH, is such a weak turd.

Also Famine, you mentioned that OHC designs were more reliable. How so?


M

 

[Nasadus]

Theres too many variables like:

weight,
aerodynamics,
traction (i presume the twin engined car is awd)
actual power at the wheels (a twin engined car has 2 sets of transmissions/drive trains to sap power)
gearing...

To give a straight answer.

If you were to say that both cars weighed the same, had the same amount of aerodrag, transmitted the same amount of power on to the road & both were AWD and geared the same then theoretically they would reach the same top speed at the same time.

Hmm,maybe i'm approaching this in the wrong way.I look at it this way.
A 250BHP engine can reach a certain top speed,why would another engine with the same capabillity increase that top speed.For example both engines can reach a top speed of 250km/h.When put together they will still only be able to reach 250 km/h.The only thing that will be different is that they will reach their top speed faster.

Is this correct?
Discard all factors.The only thing that is different between the two cars is that one has two engines and the other has one engine,everything else is the same.

 

[Famine]

Also Famine, you mentioned that OHC designs were more reliable. How so?

The most reliable "brands" available on the UK market are all OHC-based - Subaru, Toyota/Lexus, Honda, Mazda. The least reliable are all OHV-based - Land Rover, TVR (although TVR are often excluded since they're low volume). The exceptions are FIAT/Alfa, but due to the comical approach of Italian manufacturers to electronics.

In all UK reliability surveys (conducted on 2-3 year old cars) in the last 10 years I cannot recall one occasion where an OHV car placed in the top half. The only things keeping OHVs from flat last are Italian electronics and French build quality.

And Rover.

There is only one mass-produced OHV car left - the Ford Ka, using a 1.3 pushrod with origins in the 1963 Ford Anglia. This also happens to be one of the cheapest cars on the market and is often praised for its handling, but criticised for the lacklustre engine.

In addition to my Mazda example, Honda have never had a VTEC - OHC - engine failure on an engine within normal service schedule. Ever.


GTChamp2003 - No. A car isn't limited to "x" speed by its engine power. It's limited by its wheel power (along with frontal area and coefficient of drag - but we're assuming them to be identical). The wheel power from two 250hp engines would be the same as the wheel power from one 500hp engine, assuming, as you said, transmission losses are identical and allow identical wheel power.

 

[daan]

Guys, having a "discussion" with Famine is like

It feels ok to start with but you're eventually going to have a sore head.

 

[Nasadus]

GTChamp2003 - No. A car isn't limited to "x" speed by its engine power. It's limited by its wheel power (along with frontal area and coefficient of drag - but we're assuming them to be identical). The wheel power from two 250hp engines would be the same as the wheel power from one 500hp engine, assuming, as you said, transmission losses are identical and allow identical wheel power.

I see.
Would the same apply to boats or rather speedboats.This one is rather interesting cause a propeller spins at lets say 4000rpm,2 props won't make a difference cause both are spinning at the same rate.So no speed advantage is gained.Wich would then be faster.One boat who has a 600HP engine or a boat who has 2 300HP?

The one with 600HP will be able to spin the propeller faster than the one with 2 300HP engines.

This is the last question i have.

 

[Famine]

It's the same as the cars.

Two engines churning out a total of "x" "effort" are equal to one engine also churning out a total of "x" "effort", all other things being equal.

 

[xcsti]

Pushrod engines are simpler, and thus easier to fix. There are generally a wider variety of parts available to the pushrod engine (350, etc) at cheaper prices. They also have far more tuning potential. There are many more 600+HP smallblock Chevys running around than anything else.

In NA yes there are many more small blocks, but else where it is much different. Small blocks have been developed over the past what 50 yearsand have beenin how many cars? One should expect them to perform well given the amount of time in developement. Overall I'd agree with famine that there are an incredible amount of high powered skylines or similar ohc turbo cars running on the streets.

I bet most Ferraris do less than 8000 miles a year. i doubt many ferraris have 100,000 on the clock if any. Those engines are just not designed for high milage so comparison is mute.

"Moot" but your point is solid.

Ultimatly any type of valve train can get the job done. American manufacturors are balancing the advatages and disadvantages of ohc engines. They have years of experience in ohv engines so most of their offerings are ohv but to become competitive in the compact market they have needed to start developing small ohc engines. Eventually I'll bet the us switches over to ohc but for now it is much cheaper to produce ohv engines (they alreay have the infrastructure set up well).

 

[High-Test]

A Formula 1 engine has an output of around 950bhp (a conservative guess) from 3ltrs

That's True. A good point. But because those engines are manufactured purely for more power and rpm's, they probably get 4-5 (please correct me if I'm wrong) miles per gallon. Don't they too run on special super high octane race fuel? I'd like to see what happens to a Cosworth DFV when you run 87 octane through it. It'd prolly run until the gas tank's empty or cut off, because of the high compression, and probably wreak hell on the innner workings.

On the Other hand, an OHV V8 can run on pump gas, and still get crazy power and torque. (I'm not saying that an F1 engine doesn't) I guess my point is that One running a smallblock V8 in their racecar wouldn't have to have so many little things they'd have to do with their motor, because the OHV is alot simpler, and therefore, less stuff to break/fix/take care of.

One point that none of you have brought up is engine longevity. Many pushrod engines (large V8's in particular) are relatively understressed engines. A low-stress engine (Say, a 405hp 5.7L V8) will far outlast a 3-4L, 400hp high-stress Ferrari engine under similar conditions. Or a Ford 4.6. Or a Nissan VQ-series engine.

I believe Lexus used an OHC V8 in the '93 LS400, so If i'm wrong my whole argumenmt is shot.

Ok, My friend's '93 Suburban has almost 400,000 miles on it. He bought it practically new. he only did scheduled maintenance, and has never had a problem. In fact, the only reason his suburban has ever been off the road is because the transmission broke. not the motor.

My stepdad's '93 LS 400 had the fancy lexus V8. he babied that car. mobil 1 synthetic oil, sticking to maintenance chart religiously, and the whole thing failed on him at 283,000 miles. still, a long haul for a car driven by a salesman. the alternator failed, the fuel pump broke, injectors were messed up somehow, valve belts were screwing up, it was a mess. and It would have cost more than the car was worth to fix it. And he didn't even get his estimate at the dealer.

I guess my point is that OHV engines run almost forever. I'd say look at the flathead ford, but it had the valves in the block.

Guys, having a "discussion" with Famine is like

A Cosworth DFV, and a Big block V8 with a lot of freaking power.

I know! my brain is going on strike trying to understand some of his posts!

 

[Famine]

F1 cars run on "pump" petrol. It's not exactly the same as you can buy at Shell, but it's not a million miles away.

 

[Firebird]

I had written a long response to most of the issues raised in the last dozen or so posts, but Internet Explorer decided it was going to go back a page when I pressed CTRL+V while I was pasting some text.

I retyped most of it again, and IE went back a page, again.

Serves me right for not copy-pasting my post into something a less temperamental, I suppose.

I'm not going to fully re-write it for a second time in order to preserve what little sanity I have left.

Here's the gist of it in point form:


- I'd like to see Famine's statistical analysis of my hasty rankings out of curiosity (not fishing).
- Ford Australia's 4.0L I6 has never been used outside of Australia. The parent company has never used a 4.0L OHV I6.
- Ford Australia's 5.4L OHC V8 is sourced from Ford North America's F-series pcikup trucks. It has always been OHC.
- Holden's Alloytech V6 has always been OHC as well, sourced from the Cadillac CTS.
- The fact that DOHC heads allow an engine of a given displacement to produce more power than an engine with OHV at that same displacement is not in question, but a smaller displacement engine with DOHC and larger one with OHV are simply different means to the same end.
- The reliability of the OHV layout cannot be based upon the overall reliability of Land Rover and TVR. Their reliability has more to do with being English. ()
- Throttle response is not (noticeably) dependent on valvetrain layout. North American OHV engines, none of which have less than six cylinders as of today, are tuned to take advantage of their displacement and the limitations of the OHV layout at lower revolutions, resulting in more power and torque at throttle tip-in.
- OHV engines can support variable valve timing systems (as well as more than two-valves-per-cylinder).

 

[Emohawk]

Somebody mentioned 8000hp OHV dragsters. Don't the NHRA rules say that the engines have to be OHV?

menglan:
-This hypothetical OHV V8 making it's power on pump gas wouldn't happen to be more then twice the size of the hypothetical F1 engine you're comparing it to, would it?
-Nope, the UZ series (Lexus V8) is DOHC.

Firebird:
-There's no reason OHV engines wouldn't be able to support VVT, but do any production OHV engines actually have it?

Famine:
-Are TVR still using OHV engines? I thought they were using their own 4l (DOHC) I6 exclusivly now.

 

[Firebird]

Firebird:
-There's no reason OHV engines wouldn't be able to support VVT, but do any production OHV engines actually have it?

As of today, no.

However, the Pontiac G6 will add a GTP model later this year or early next year with a 3.9L OHV V6 with VVT.

 

[Duke]

All I've got to say is that the 38-year-old OHV pushrod V8 in my garage had 195,000 miles on it before I even had to take the valve covers off, and it's had about 75,000 miles on it since then, and it will start right now if I walk out and turn the key despite the fact that I haven't driven it in the last 9 months.

So 'unreliability' ain't an issue for me.

 

[High-Test]

Somebody mentioned 8000hp OHV dragsters. Don't the NHRA rules say that the engines have to be OHV?

menglan:
-This hypothetical OHV V8 making it's power on pump gas wouldn't happen to be more then twice the size of the hypothetical F1 engine you're comparing it to, would it?
-Nope, the UZ series (Lexus V8) is DOHC.

If I said it was OHV, I meant to say it had Overhead Cams.

@Duke: I wish the I6 in my Biscayne would start up when I wanted it to, It takes a couple tries to get it up&going, and then it has to warm up. Oh well,nothing a Good 'ol 305 Cubic inch OHV V8 won't fix...

 

[///M-Spec]

In all UK reliability surveys (conducted on 2-3 year old cars) in the last 10 years I cannot recall one occasion where an OHV car placed in the top half. The only things keeping OHVs from flat last are Italian electronics and French build quality.

And Rover.

There is only one mass-produced OHV car left - the Ford Ka, using a 1.3 pushrod with origins in the 1963 Ford Anglia. This also happens to be one of the cheapest cars on the market and is often praised for its handling, but criticised for the lacklustre engine.

I see. But are these reliability surveys for the entire car or just for the drivetrain? Surely with the lack of OHV cars for your market the sample selection is very limited.

And what about all the OHV engines running around in cars and trucks over here in the land of no displacement tax and cheap gas?

@Firebird: Will the VVT setup in the G6 GTP use a system like Honda's where the cam has separate profiles for economy and power and just switch between them? Or a system where the cam has one set of lobes and some kind of helical gearset shifts it around like BMW's?

Re: the 2 250 hp engines vs. 1 500 hp engine comparo; everything CANNOT be equal in this case. The two engines making 250 hp will still weigh more put together than the single 500 hp engine, assuming same type of design and construction. Therefore, your twin engined car will probably end up weighing more than your single engined car, slightly tipping the balance in favor of the single engined car.


M

 

[Famine]

I see. But are these reliability surveys for the entire car or just for the drivetrain? Surely with the lack of OHV cars for your market the sample selection is very limited.

And what about all the OHV engines running around in cars and trucks over here in the land of no displacement tax and cheap gas?

Yes and no.

The surveys place the cars overall according to the reliability - or customer satisfaction in the case of JD Power - but the stats can be broken down.

Right now the sample size is very small indeed. Or "one" as it's known. 10 years ago there was a much larger selection, but the manufacturers - including Ford - have, one-by-one, dropped OHVs from their line-up. In fact, 10 years ago, Ford's reliability was nearly rock-bottom. Today the Focus is the most reliable car sold in Germany and their reputation is through the roof. Yes, other things have changed too other than JUST the switch to OHC, but it is interesting, at the very least, that Ford's European reputation has increased as they've gradually phased OHV out and that no OHV car in the last decade has placed in the top half for reliability OR customer satisfaction.


I would be interested in seeing an American market reliability survey for 2004 in relation to engine type, if you have one.

 

[retsmah]

I really doubt any reliability issues have to do with the valvetrain. Again looking at Honda's motorcycle motors from the late 70s, the OHV engines were easily as reliable as the SOHC engines.

But even then that's not really proof one way or the other, as the OHV bike was the higher tech one, featuring among other things liquid cooling. You can't compair two completely different engines and then attribute all of the differences in them to the valvetrains.

 

[///M-Spec]

Yes, other things have changed too other than JUST the switch to OHC, but it is interesting, at the very least, that Ford's European reputation has increased as they've gradually phased OHV out and that no OHV car in the last decade has placed in the top half for reliability OR customer satisfaction.

That's a lot of factors to consider, really. I was hoping you had a mechanical rationale for the reliablity argument.

I would be interested in seeing an American market reliability survey for 2004 in relation to engine type, if you have one.

I don't, but Dougie boy probably does. If he doesn't chime in, maybe I'll take the time to look it up later.

I'm not having ANY luck finding the weight and dimensions on the Nissan VQ. But I admit I'm not looking very hard.


M

 

[Firebird]

Will the VVT setup in the G6 GTP use a system like Honda's where the cam has separate profiles for economy and power and just switch between them? Or a system where the cam has one set of lobes and some kind of helical gearset shifts it around like BMW's?

It has a cam phaser much like VANOS'. Here's a small picture of the engine:

In front of the camshaft timing sprocket.

I would be interested in seeing an American market reliability survey for 2004 in relation to engine type, if you have one.

OHVs on the list:

Oldsmobile Alero (Entry Midsize Car)
Chevrolet Malibu (Entry Midsize Car)
Buick Century (Premium Midsize Car)
Chevrolet Monte Carlo (Premium Midsize Car)
Buick LeSabre (Full-size Car)
Ford Explorer Sport-Trac (Compact Pickup)
Ford Ranger (Compact Pickup)
Cadillac Escalade EXT (Light-Duty Full-Size Pickup)
Ford F-150 Heritage/Lightning (Light-Duty Full-Size Pickup)
Dodge Ram (Heavy-Duty Full-Size Pickup)
GMC Sierra (Heavy-Duty Full-Size Pickup)
Chevrolet Silverado (Heavy-Duty Full-Size Pickup)
Chevrolet Suburban (Full-Size SUV)
Chevrolet Tahoe (Full-Size SUV)
Cadillac Escalade/Escalade ESV (Premium Luxury SUV)
Dodge Caravan/Grand Caravan (Compact Van)

16/57 have OHV

15/56 on J.D. Power's 2005 list have OHV.

 

[Famine]

You only had 57 models available for sale in the US market in 2004?