V8 vs Inline four???

[wheelman]

Vegeta,

 

You keep saying that an OHC either single or double will have fewer moving parts and less friction. Lets stop a second and think about this.

 

The friction points will be at followers/lifters, rockers (cam/pivot/pushrod/valve stem), cam journals, valve stems, valve springs and timing chain/belt. The valve stem and spring loads are the same with 2 valve heads but double with 4. Assume the cams have the same number of journals, we'll say 5 for the sake of argument.

 

An "old style" push rod V8 has 1 cam, 16 lifters (some with rollers), 16 push-rods, 16 rockers (possibly rollers) and 1 timing chain. The friction points are the cam journals (5), the lifters (16), the rockers (32, push-rod and valve) and the timing chain (2). Total 55

 

SOHC: 2 valves per cylinder

2 cams, 16 rockers, 2 timing belts/chains

Cams (10), rockers (32 cam contact and valve), chains/belts (4) Total 46

 

SOHC: 4 valves per cylinder

2 cams, 16 rockers, 2 timing belts/chains

Cams (10), rockers (48 cam contact and valve), chains/belts (4) Total 62

 

DOHC: 4 valves per cylinder

4 cams, 32 cam followers, 2 timing belts/chains

Cams (20), Followers (32), chains/belts (4) Total 56

 

The SOHC setup has the fewest contact points but the long timing chains/belts with the required tensioners and momentum at high RPMS creates a failure point and contributes to timing drift. Unless some type of hydraulic "lifter" setup is used it also requires periodic vavle train adjustment and there is no way to use VVT. If the hydraulic lifters are used then the pump-up problem appears. Add 4 valves per cylinder and it gets even worse with the complicated rocker assembly. Ever tried to work on one of these?

 

The DOHC setup has almost the same number of contact points as the push-rod and the added advantage of no rocker assembly. This setup is the optimal from a simplicity stand-point, direct actuation of the valve by the cam. But it has the dis-advantage of the long timing chain/belt and in most cases causes the head to be larger. This setup doesn't necessarily imply 4-valves, Fiat made a DOHC with 1 cam for intake an 1 for exhaust with 2 valves/cylinder, but all newer engines with DOHC have 4. The big dis-advantage I run into with these is again maintenance. You have to use shims to adjust follower to cam clearance which requires the cams be removed, not difficult but still can be a PITA.

 

Anyway, as we've all been discussing each setup has advantages and dis-advantages and to say that the OHC designs have fewer moving parts simply because the push-rods aren't there is not completely true. I will agree that the push-rod system can have more timing drift at high rpm due to rod flex and lifter pump-up but the long chain/belt of the OHC design has the same problem because the chain or belt stretches due to it's length and weight at higher rpms. In my opinion thw worst setup is the SOHC, it has the longer chain issue and the complexity of all the rockers.

 

Just my $.02 worth. If I made any mistakes in my simplified analysis please point them out.

 

Wheelman

[Savage42]

Once again' date=' I'm not really arguing the original point of this post, but....

 

Savage42,

And just to set the record straight: I DO BOW DOWN TO THE WISDOM OF THE HYBRIDZ GURUS.

 

Responding to what you said, though, $30,000 gets you way more than a grocerie getter....

And anyone who spent 10,000 bucks in performance parts on their honda that isn't getting at least high 11's in the quarter mile is obviously doing something wrong.[/quote']

 

OK, you can't be all that bad.

 

I guess I should have made it clear that I was speaking about a broad generalization of what 90% of the "ricers" out there are doing. Yes, there are guys that build cool cars and build them right, those are the ones that cover Sport Compact Car (in which I've had 2 cars in) and other tuners mags. It's the majority of these guys that don't have a clue, many a Honda owner, that bolt on some "pretty stuff", some stickers, CAI, big tip & think they are racers that give a bad name to the few that do get it. It's about the same for just about every car club, so I'm not trying to target any specific person, make or model of car. Fast is good, just a ton of different ways to do it.

 

BTW, I spanked 2000 Mallet Corvette that runs the Silver State Classic in the 185 MPH & over Unlimited class by over 5 seconds on a 2 minute run at a hillclimb here in Oregon in my little turbo V6 "econo-box" Datsun 510. Moral Victory!! 8) Of course, my cars & experience have to due with road racing, autocross, & hillclimbs, which is a minority compared to all the "straight-liners" around here. (not that I don't appreciate those guys, too) Later.

[Phantom]

I ran a hillclimb many years ago. It was the old Winchester grade in northern Idaho. Had a '70 340 Cuda. Bone Stock. Won my class and came in third overall behind a Porsche 911 and a GT500 shelby Mustang. That was back when I was young and indestructible. Scared the crap out of everyone but me the way I was drifting the corners - that had no barriers except the rocks 300' below. Had to partially shut down part way through the run - lost oil pressure as it was all up in the sides of the pan away from the pump pick-up.

Still avery fond memory - brought back by a recent romp thorugh a national forest between Rogers, AR & Branson, MO. This time, though, it was about 90 miles instead of 4.5.

[pparaska]

"quite mistaken"? No, I don't agree.

 

vegeta, those DOHC heads for the SBC are basically an unknown. Grumpyvette tried to get real info on them, and it didn't happen. And their claim of:

"Torque

The dyno also reveals a broad, flat torque curve with a peak of 437 lb./ft @ 4500 RPM. In fact, 85% of the torque occurs all the way from 3000-6000 RPM!"

 

That's a torque curve with 85% or better of max torque over 3000 rpm. That's about typical for a well configured 2 valve per cylinder engine.

 

Compare that to Phantom's LS1's "90%+ of the maximum torque from 1500 to 5400 rpm"

 

That's 90%+ (not 85%) of max torque or better over 3900rpm.

 

Which would you say was "broader" or more "flat"?

 

Everything I read on that page about the DOHC heads sounds like a Madison Avenue story to get your $5K. Sure, with an 10:1 LT1 with those expensive heads versus brand X 2 valve OHV heads, they make 159 more peak HP. But at that price, I'd expect more!

 

A new Z06 vette makes 405 hp at 6000 rpm, 400 lbft at 4800 rpm. I hardly think that 474 hp is a sh!tload more. Tweak the Z06, and that power is there, while still keeping within emissions.

 

DOHC: Valve curtain area is a great thing. But without the valves opening/closing with alot of acceleration, the extra flow near overlap will hurt low end torque.

 

And I agree with wheelman - SOHC isn't really much if any simpler. Now you have:

 

1 (or 2) long chain(s)

1 (or 2) tensioner(s)

various chain guides

2 cam sprockets

2 cams

2 cam bearing sets

 

versus

1 SHORT chain (fewer links, less chance of failure, less friction?)

0 tensioners

0 chain guides

1 cam sprocket

1 cam

1 cam bearing set,

16 simple lifters (which can be solid or hyd, BTW - solid can be lighter, getting away from the rpm issue somewhat)

16 pushrods.

(Oh, and the lifters would be roller, not a cam wiping across a rocker arm.)

 

I bet the friction difference is not very large, and may even benefit the Cam-in-block OHV design.

 

Remember, if the engine is designed with a 4000-wide rpm power band, and 6000 is near redline, PUSHROD/OHV CAN HANDLE THE PROBLEM. No SOHC fanciness/cost/etc. needed.

 

Just because Ford puts SOHC 4.6L engines in many different vehicles that cost less than a Vette (WAY cheaper?) doesn't prove anything. And the design parameters are different. ALso, alot of Mustang guys like the old pushrod 5.0L engine, since it made more power and more torque down low. BTW, the LS1 is sold in more than just the Vette.

 

I have a challenge for you - try looking at this WITHOUT the hard bias against simple engineering solutions (i.e., pushrods). Your arguments sound like they come from someone that's an engine-technology snob. Go back and read what you wrote again, wiith the viewpoint of someone that can appreciate a Keep It Simple Stupid (KISS) design philosophy, and see if I'm not the slightest bit right.

 

Like johnc said, the LS1 bridge is a less sophisticated bridge than is that typically designed in Germany and Japan, but that doesn't mean it's an inferior engineering solution to the problem of "what to put in the new vette?" Extra technology is just that - extra. Not needed to get teh job done.

 

Like fl327 pointed out, the Europeans and Japanese had reasons to go after smaller engines - fuel prices and/or taxes on displacement. So they improved the SOHC and DOHC engine designs that have been around for 100+ years, with small displacement, to make THEIR designs match the design parameters. Nothing wrong with that! It's just that for NA engines, what you give up in engine displacement, you give up in low rpm torque. VVT/VTEC/etc. was developed to get around that, and it's a wonderful thing. But for larger displacement engines, it's not needed, but it'd be a nice EXTRA!

 

Oh yeah, wheelman, if pushrods flex, it's all over. They compress, but if they flex, they WILL bend - and stay that way. A pushrod is just a 1-force member - it goes under compression alone (neglecting the miniscule moments put on the ends of the pushrod by the lifters or rockers). So it acts like a column, which won't bend, until it buckles, and then its all over. This won't happen if good parts of sufficient stiffness, etc. are used - an old engineering problem that was worked out a long time ago.

[Phantom]

I love you guys! This is so fun. Let's go have a beer. Oops - I forgot - I don't drink. Oh well - so much for that low tech solution.

[Savage42]

Dang, I'm exhausted. Can't quite figure out how I feel right now......like I just had a good workout and need a Gatorade, or that I'm wiped out and need a cigarette.

[johnc]

And after this big workout, not a single mind has been changed or a single opinion altered. Its basically just a big circle jerk.

[wheelman]

OK Pete, I'm suitably humbled.

Your correct about the push-rods not flexing, when I wrote that I was thinking about something else and didn't catch the mistake. I think what I was after may have been rocker flex but that doesn't make sense either when I think about it, or maybe rocker stud flex. Anyway the idea was that there isn't much room in the OHV push-rod design for valve timing drift issues like you can get the long timing chain and all it's momentum especially if you use solid lifters.

 

Wheelman

[Guest vegeta]

Hey guys

All great points

 

I gotta say, though, that the japanese manufacturers are NOT taxed on the engines over 2.0 liters that they sell HERE in the U.S., and they still remain smaller, yet more efficient. Also, when the foreigners up the displacement, they retain the sophisticated design, so in a sense its bigger AND better (aka, the 5.6L nissan titan, etc.)

 

Also, the LT5 engines made the same power in 1993/95 as the LS6 (in the Z06 vette) makes today (405 hp) and the LT5 made it at a lower RPM (5800 vs 6000). Plus those engines only got one slight redesign and then they were discontinued, whereas if they had been kept till today, Chevy would have gotten a hell of a lot more power out of them. Just check out that link I posted earlier. Those custom 4 valve heads made 474 hp at 6000 RPM from a mild cammed 350 chevy, and I gotta say that getting those numbers with the basic 2 valve heads would be like trying to squeeze water out of a diamond.

 

The Honda S2000 really IS peaky as hell (compared to most 240 hp engines) because it is only 2.0 liters!! But if you compare the dyno chart for an S2000 with most other 2.0 liter cars, you'll see that, yes, it makes big power up top, but it still has a more torquey bottom end than a lower reving 2.0 L (like one from a toyota celica).

 

Hey, you're right, a good turbo Z WOULD smoke an EVO on a dry day, no doubt

And I think adding a turbo to a smaller displacement, yet sophisticated engine, in order to make economical horsepower is a great idea, because you end up with a cleaner, more fuel efficient car. And I think its a better move by the manufacturers. Just look at what Dodge did to the Neon, it was once considered crappy, but slap on a turbo and the new SRT4 (a thinly disguised turbo Neon) cracks into the 13's and only costs around $20k.

 

Last time I checked, the number one selling car in America was the Toyota Camry, and the Honda Accord wasn't far down. This spot was once occupied by the Taurus, but times change, as well as tastes.

 

And I'll easily compare that ONE time you raced against an STI, to the numerous proffessional tests of that car, which match its performance with a C5. Check out Motor Trend, Car and Driver, etc. (13.3 seconds in the 1/4, over 70mph on the slalom, etc).

 

But, yeah, you're TOTALLY right about having a second car for confortable people-hauling. I'm in my 20's and still in college, so I don't really need one yet (my Z does me just fine), but I'm sure that the time will come when I'll want a sedan or a wagon or something like that. Maybe by then I can afford an EVO

 

Yeah, Johnc,

I know what you mean. And I'm sort of saying the same thing in a way. Like the analogy I used of the WRX or EVO being as fast as a C5 (not the Z06), and still costing less than the C5. The engineers at Mitsubishi and Suburu accomplished the same performance goals as the vette, with less budget, and ended up with a car you can take 3 friends to Tahoe in and still get decent MPG.

 

Wheelman,

Great point, man.

But the hydraulic lifter trade off in SOHC is one that is already inherent with OHV designs, and since there are less "friction points" in the SOHC engine, as opposed to the OHV, there are less frictional losses, like I said. Double roller timing chains don't have many stretching issues, either.

And I'd like to point out that the OHV v8 engine actually has more than 55 friction points: 16 where the lifter meets the cam, 16 where the lifter meets the pushrod, 16 where the pushrod meets the rocker arm, 16 on the rocker arm's fulcrum (could be a bolt or a shaft, depends), 16 where the rocker arm meets the valve, one timing chain, and 5 on the cam journals. Thats actually 86 friction points. A SOHC, 2 valve v8 has: 16 where the rocker meets the cam, 16 on the rocker fulcrum, 16 where the rocker meets the valve, two timing chains, and 10 on the cam journals. Thats 60 points. Much simpler. And DOHC is: 20 on cam journals, 32 where the cam meets the followers, 32 where the followers meet the valve, and 2 timing chains. Thats 86, actually the same as OHV, but with the advantage of 32 valves, and notice how the cam directly contacts the valves, so there is MUCH smoother, more stable operation, which results in less wear, and higher rpm capability, as well as being more reliable.

 

I had a Prelude with the SOHC, 3 valves per cylinder 1.8L four. It wasn't meant as a sports car, it was for commuting to and from school, and it got 30 mpg. It was relatively gutless with only 110 hp, but that was enough for the 2275 lb car to get around easily. I didn't do anything to the car, because it looked like sh!t, and at the time it was just transportation while I saved for a Z (good choice, eh? ), but I did adjust the cam a few times for better response, and the adjustment was a piece of cake. Damn reliable for over 200,000+ miles, too. But yeah, DOHC engines with the shim type setup can suck when it comes time to adjust them. My dad had a few Alfa Romeo GTV's and Spider's with the DOHC shim type latyout, and they were a pain to work on. But maybe that's only because they were Italian?

 

And Savage42,

I totally know what you mean. Even the guys in the import scene hate those big-wing-with-no-horsepower guys.

 

I have a favorite hill-climb/road-race section of Highway 1 here in the Bay Area, where recently I spanked a newer M3 BMW and a Mustang GT in my pretty much stock 280Z.

Imagine the surprise on that guy's face --->

He He

 

Later

[Guest vegeta]

Woah!

I was writing mine when a bunch more posts came on.

 

Damn, my hands are sore from this great work out!!!

[Guest vegeta]

I think what Wheelman was trying to do was respond to what I had said about "flex" in the pushrods, which was obviously the wrong choice of wording. I was talking about the effect of absorbing the "ramp" of a cam lobe that a pushrod design is known for, and this is noticed when applying the same cam specs that you had in your OHV engine to an OHC engine in which the valve will respond more quickly to the cam profile. Remember we're talking fractions of a second here with any engine speed.

[Guest vegeta]

Pparaska,

I don't know why you think I'm biased, or whatever, because I've been saying the whole time I enjoy old-school hotrodding. I get-off on all types of cars, and have friends who are into all different motor-head scenes. I started out as a chevy fan, and did plenty of work to the SBC in both my camaros as well as helping my dad with his vettes. And it was fun. But not a good enough solution for a modern car. I just would never call it high tech, and I don't think keeping the "just meet the status quo" philosophy in Detroit's engineering department is good, either.

[Guest vegeta]

Also,

The 4 valve heads on that link I posted were not DOHC.

I even said that in my post. They use special shaft-type rocker arms pushed by the standard pushrods, to actuate the valves.

And this is not a new thing. I remember reading an article in HotRod or Popular Hotrodding (I'll have to find the article) In which they talked about a guy who made custom heads just like those, years ago. The magazine had a set of these 4 valve heads, and had dyno tested them on a SBC, back-to-back with equivelent 2 valve head SBC's to demonstrate the power gains. They reported a 15% increase in power throughout the rpm range. This was just an ordinary tech article like HotRod always has, not some advertising scam. I'll try to find the magazine to post it, or if anyone knows what I'm talking about please chime in now.

[Guest vegeta]

Also,

All in good spirits, of course:

I would say almost 70 extra hp (474 vs 405) from the same N/A displacement, and same RPM, DEFINITELY is a sh!tload more, considering it was CARBED and the LS6 has a DIRECT PORT EFI system. Like I already said before, if this engine had the LS1 EFI it would be even more powerful.

And please tell me how you would plan on getting 70 more hp from an LS6, at the same RPM, while still passing emissions, without nitrous/turbo/supercharging? 13.0:1.0 compression with a .550" lift cam will not fix this problem.

I do know that the Mosler MT9000 (something like that) supercar uses a breathed-on LS6, and it only makes 435 hp (and at a higher RPM).

 

I know the LS1/LS2/LS6 is in other cars (new Cadillac CTS-V, Pontiac GTO, now-dead Camaros/Firebirds, etc). This is another reason why it would not cost Chevy much to do the upgrade, because global-parts-bin style engineering like that lowers production costs by mass producing the desired parts. And like I said, its not the cheapest way to meet the engineering requirements, because the new wave of imports are doing it more cost effectively (once again a good example is the EVO or STI).

 

And hey, this is all in fun. The reason I love Hybridz is because there are lots of people who are into all different types of hotrodding, like myself, and we can all share and discuss info and oppinions in a friendly environment. THREE CHEERS FOR HYBRIDZ.ORG

 

Later

[wheelman]

Vegeta,

I have to take exception to calling the interface between the lifters and push-rods a friction point. I also wouldn't classify the cam follower to valve stem interface a friction point either, unless you count the rotation of the follower, if they rotate.

 

I agree with you whole heartedly about loving HybridZ, this place is the best for getting good technical help and participating in discussions like this without it degenerating into name calling.

 

I recently worked on a Nissan GA16DE engine for friends and the head is very complicated. It has a special timing chain for the 2 cams that is separate from but driven by the main timing chain driven by the crank. It also uses shim type adjustments which require removal of both timing chains to get the cams out to replace the shims. Both chains have their own tensioners and can contribute to valve timing drift. I like the idea of the cam directly actuating the valves but it gets complicated.

 

I also have to say that I like the "Coolness" factor of the multi-cam 4 valve heads and know thay have the potential to make gobs of power but my checkbook shudders at the thought of putting them on a SBC. After reading this thread I gave serious thought to scrapping the LT1 project and using a Toyota 1UZ-FE 4 liter 32 valve V8. These engines are relatively cheap and make good HP stock but it turns out there aren't many after market parts and the replacement parts are expensive when repairs are required. Anyway it comes down to cost vs HP and it's impossible to beat a SBC for that!!!

 

Wheelman

[Guest vegeta]

No doubt about it, SBC is the best v8 bang for the buck.

 

And I can see what you mean about the afforementioned friction points. I was just trying to be very accurate, maybe too much so.

 

I feel that I've said pretty much all I need to about the whole valvetrain design issue. In the end, I guess it boils down to "different strokes for different folks". If someone likes the KISS design philosophy, that's their oppinion and they have a right to it, after all this is America. And I'll respect that oppinion, even though I disagree. Oh well, I guess JohnC was right, this is just one big circle-jerk!

 

later

[Guest JAMIE T]

I can't believe this thread is 7 pages long... I feel dumb for reading all of these posts. I think the answer to the guys question was answered on the first page. Whoever started the American vs. Japanese engineering blab should be dragged through the streets tied to a horse. There is no replacement for displacement. Why do even the Japanese DOHC guys build strokers if it was ALL about engineering? 'Cause cubic inches(or CC's or L's or whatever you want to call it) RULES. A friend of mine is building a 2.2L SR20. For what? I know that all the L6 guys would rather have a 2.8L or better yet a 3.0+L than the old 2.4L. Why does the Triton Truck have a 5.6L DOHC V8 rather than a 3L DOHC V8? This thread is dead...

[Guest vegeta]

read the last couple pages again.

for strictly performance/hotrodding you can do what you please.

you're right, the original question was answered.

the other disagreement was over modern cars' overall abilities/shortcomings.

 

i dont think "dragging someone through the street" is the kind of thing that maintains a positive atmosphere on this site.

you need to chill out.

[BillZ260]

Is this post STILL going?

[Guest JAMIE T]

LOL, a little harsh? OK, why not. It was about 1am when I posted that and I promise I wasn't drinking.... Much. Try and understand my view though. I build many engines. Not to factory specs mind you. Inside, they are ALL fine pieces of engineering. They all accomplish the same task. Some do it with less parts. Horse Power, It's really all about cylinder head airflow. I'll include cam action in that catagory becuase the cam needs to have enough lift to allow the head to flow the required CFM for the given task.

 

A good example of this is the NHRA Comp Eliminator class. It is weight/CID limited. If you want to run a very light car, you must run a small CID engine. My machinist has a late 80's Trans Am comp elim car. It is a chromoly tube chassis car with pretty much all fiberglass body except the quarters and the roof. It is very light weight and runs a 267 CID small block chevy V8. It has GM 14 degree heads and two carbs (660 holley center squirters if you care) and makes about 800 hp on the engine dyno. He spins the motor past 10K. It's got a clutchless 5spd. 267 cid is just over 4.3L. You know what? He uses de-stroked OEM 283 chevy cranks. You do realize they haven't made 283's since about '67. It doesn't take high tech to make power. It takes RPM and airflow.

 

When you build a bigger cid engine, you can make the same power... Easier. A 632 CID big block chevy can make 800 hp and be driven everyday on pump gas. And, make that power at under 7000 rpm's.

 

Honda makes a good motor. They do have flaws(a bit of piston slap on cold start-ups). Variable valve timing isn't new either. Alfa Romeo had VVT in the late 70's. Variable ratio rockers have been around for a long time also, they just never caught on.

 

The S2000 might make 240hp and have a 9K redline, but the vast majority of S2000's don't see the high side of 5K on a day to day basis.

 

My LT1 makes more torque under 3K than an '01 BMW M3 makes period. I've got the dyno graphs to prove it. The dyno operator/shop owner happens to be a very good friend of mine and it was his M3.

 

Speaking of V8's and pushrods. The elitist OHC guys can get some C5R Corvette action if they want to try. Yes the Le Mans winning Vettes are pushrod V8's.