Why use old technology?

[M_Power]

Alright, so I was thinking today why car companies are still using old technology when better tech is already here. I am confused that domestic companies are still making pushrod motors with only 2 valves per cylinder, when obviously a 4 valve DOHC is better. Why does the SL55 AMG use a SOHC 3 valve engine when it is a 160 000+ car?
And also why do F1 engines seem to have odd displacements, such as V8's only being like 3L and such?

[EK 2.0]

Because I am sure the MB did a lot of research and spent millions of ducats to see that for them the 3 Valve design for whatever reason works best for them man...

I mean for a "layman's" example, we all KNOW that IRS's handle better than live axles, but GM still used them for the Camaros and Firebirds, to keep costs down so...


A pushrod motor is a LOT cheaper than an overhead cam motor, so companies are doing that to keep the costs lower for buyers, so you buy their car...

[rage2]

This post is in the right section.

A 4V design is better, but has its disadvantages too. Poor low end torque, poor emissions.

2V designs restrict top end power, which works well in low revving engines. Cheaper to produce too.

Mercedes uses their 3V design strictly for emissions advantages. And they don't have a problem with power, as shown in your SL55 example .

I personally don't care what "technology" is in the engine. That's strictly for bench race arguments hehe. So what if a viper is a friggin' 8L inefficient pushrod powerplant. So what if mercedes needs superchargers to make big power. The end result is, it has a big fat wide powerband, and that's what win races, and puts that big grin on your face.

[sxtasy]

Do you think it is cheaper to make rear drums as opposed to rear disc brakes? I am surprised a lot of cars are still equipped with them

[rage2]

Originally posted by sxtasy
Do you think it is cheaper to make rear drums as opposed to rear disc brakes? I am surprised a lot of cars are still equipped with them

Yes it's cheaper. That and rear brakes are hardly used under braking... the front brakes does most of the job.

[lude_conduct]

Rear drums are a hellluva lot cheaper to put on cars, I'm not too sure why though. I think it might be because they are easier to assemble.

But going back to the main idea, pushrod's are actually a newer concept than overhead valves. But, pushrod engines do have distinct advantages. (Along with those listed above), they are smaller and their weight isn't based so high up on the engine. Take a look at a small block chevy 350 next to a Ford DOHC 4.6L V8, there's a significant size difference.

Older technology is necessarily worse. A live axle is much better for quarter mile runs than IRS. Eg, look at Supras. Sure the IRS is nice, but considering how much power they make, their times should be a helluva lot better at the track.

F1 engines are just a result of the restrictions placed upon them by the sanctioning body. Essentially, they are trying to slow the cars down by forcing them to have smaller displacements. But the engineers have figured that a short stroke V10 is the best way of making power given the rules, so you get 800+hp and 250lb-ft of torque.

[rc2002]

What about the new dodge Hemi's they're bringing back? The hemispherical head is better than the older flat head technology but is still old technology and can only handle 2 valves per cylinder...

[Gonthro]

its all about the money

[QuasarCav]

DOHC can really affect the way a car handles. With a pushrod engine alot of the rotating mass is in the centre of the engine. with a DOHC alot of weight is on the top end of the engine.

Less crap involved=easier to fix,produce.

[heavyD]

Originally posted by QuasarCav
DOHC can really affect the way a car handles. With a pushrod engine alot of the rotating mass is in the centre of the engine. with a DOHC alot of weight is on the top end of the engine.

Less crap involved=easier to fix,produce.

Ha Ha Ha! Funny.

[EK 2.0]

Originally posted by QuasarCav
DOHC can really affect the way a car handles. With a pushrod engine alot of the rotating mass is in the centre of the engine. with a DOHC alot of weight is on the top end of the engine.

Less crap involved=easier to fix,produce.

Originally posted by heavyD


Ha Ha Ha! Funny.

He is partially right you know??...one of the reasons Subies use the flat 4's and 6's

[C4S]

Originally posted by Gonthro
its all about the money

Agree ! it is all about cost to make a car !

MB decided to keep their cost low, example, on SL55, it is not a "cheap" car, still $180,000 plus, however, for it's output, 490HP, and it is a Benz, and it is a SL, for a "only" $180K car, can as quick as a $300,000 Ferrari 360 Spider .... and if MB put a very very high tech V8 or a V10 engine in a SL55.. yes, they can do it, no problem but then the car will probaby have to cost $250K ... not $180K .

One thing I really don't liek MB is .. in order to save money, they let Chysler using their left over stuff ! why do they let the silly lookign crossfire, using all the left-over from the SLK, 3.2 engine, and super charged 3.2 V6 ... and they will have the new SLK, new 5.5 L V8 engine to use ... yes, it cost a lots to develop a nice car, and it is sort of waste, if they just don't use those 3.2L engine anymore .. and I am sure, that will make the chysler's drivers feel happy .. with MB in their cars ..

But .. what does a MB owner think ! I won't be happy if I drive a Ferrari, with a nice V8, and Ford is using the same engine in their Mustang V8 !

[QuasarCav]

I think it was the jag. race cars. the drivers would sacrifice the added top end power that DOHC gives them for the handling benefits gained by SOHC.

Something to do with where the engine weight was concentrated.

That is probably why porsche and subaru use the flat engines, more even engine bay weight!

[rage2]

OMG, some of you guys have no clue WTF you're talking about .

For starters, you want a low center of gravity, so you want your weight as low as possible. So with your example, it's BETTER to have a pushrod engine.

Subaru used to use this as a marketing gimmick. The boxer engines have the pistons flat on the bottom of the engine, so it significantly lowers CG by positioning most all of the weight nice and low. However, in a street car, it's gonna make so little difference that where the weight is on an engine is pretty irrelevant. There's much more weight compromises made throughout an entire car. I mean, look at the Subaru WRX or even the STi. Sure their engine have a very low CG... but they're not known for their amazing handling.

As for a single cam vs dual cam comparison, the weight is so minimal, that again, even in race car trim, would make so little difference that someone would sacrafice a power cut for so little weight. If the Jags did use a single cam setup (I cant confirm nor deny), it would probably be for drivability and reliability reasons.

[sputnik]

i love my 2 valve carburated V8... still my daily driver after 320,000km and if the engine were to grenade... its $1000 to drop in a rebuilt long block and keep going

[CKY]

don't f1 races like all other races have restricted engine displacements?

[QuasarCav]

^^^^^^^

sorry if i'm spouting out my ass.

ever seen that victory by design show on Ch 48?

The jag drivers said the car handled completely different with the SOHC. I know it is hearsay but thought it was relevant

[rice_eater]

how does the fact that you have one or two camshafts affect handling ability? cams open valves, not turn your wheels better

[94gs_r]

I think what he is trying to say is that the location of the camshafts relocates the mass to the top of the head. This relocation changes the center of gravity of the car which in turn affects handling. Having a flat (boxer) engine this relocation would have no effect on the center of gravity.

By the way, back to the number of valves issue. More smaller valves flow more air than larger valves with the same area. Also, smaller valves mean less reciprocating mass which means higher rev limits without valve float.

And another thing OHC engines have straighter intake and exhaust ports as they don't have to be snaked around pushrod guides therefore flow better.

[Toma]

what's wrong with pushrod engines??

Give me a real example that affects US and our cars, not some theoretical mumbo jumbo....

I can see a 4 cylinder, OHC really simplifies things.... but a V8" have you seen the length of the chain, the added idlers and tensioners etc... I prefer my pushrods....

Toma