I'm still not talking about racing. I don't care about the other guy.

Me, the car, the road. That's it. I don't even turn the radio on when driving "for fun".
To me, racing is not driving - it's a competition. Bring more to the show or capitalize on the other guy's mistakes.

My view:
The car is a package. Racing two that are identical tests driver skill or reaction time. Racing two that are different is pointless. Sure, it's fun to go to the track and see what it will do, but to obsess over it, or be disappointed because some ricer killed you at a stoplight drag? One is quicker - so what? Might as well compare jock size and be done with it.

Whatever makes you happy - that's the better motor. For you.

quote Originally posted by Gary W: The masses are not pounding on the doors of GM, demanding a small displacement, multi-cam engine.

Nope, because they can go right next door to Honda, Nissan, Toyota, Mazda, and Subaru to buy one. Look at the sales numbers.

quote Originally posted by Gary W: I still don't understand the appeal of quarter mile racing - especially in a platform with so much more potential when *not* going in a straight line. But that's just me. I'd much rather power out of a curve on a country back road than worry about the guy next to me being .01 quicker.

Yep.

Doug

[edited for grammar]

[This message has been edited by Doug Chase (edited 01-03-2004).]

quote Originally posted by Toddster: No one seems to be talking about weight. There is a rule of thumb that in order to wove twice the weight you need four times the horsepower. Today's lightweight engines AND cars are smaller and made of much more alloys, plastics, and composite materials. Did you know that an average Big Block engine NEEDS 70 more horsepower than a small block just to move its own additional weight?! Most of these old engines were designed when cars weighed 4500 lbs and just needed power to cruise. Times have changed.

FINALLY...........after reading this thread someone brought in the other variable this was the other 50% of my focus when I built my car. Why is it speculated to be insane fast ??? Not so much because of the mods, but because it went on a serious diet
For instance Don Krause is running a very similar set-up as mine and his will run a 11.6.............why is it some say it will be so much quicker ???? cause I'm 700lbs LIGHTER!!!. That rebody tip's the scales at over 3,400lbs

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man.. you can't bring 2 variables into a discussion.. I'm never doing an experiment with you people..

Ya know, I realize the pushrods have more torque, but the DOHCs are not lame ducks. I was just driving my dads 92 Grand Am around today and it has the 16v HO Quad 4 and that sucker moves for a four door four banger, and its a DOHC engine. Now, you say that the difference in power between the pushrod 3.4 and the DOHC is the problem with the head flow. I'm curious, with a better head design, what would its #s be? I mean, the DOHC is 210hp and 250ft-lbs stock while the pushrod is 160hp and **I think** 180 ft-lbs (correct me) stock. With a new head design for improved flow, are you telling me that the 3.4 could post more torque than the DOHC?

Oh wait, crud, I just had a realization. Its all about where the torque band is. Pushrod is low end torque while DOHC is high end torque, right? Hmm. So is there a compromise? Whats easier to accomplish and more economical: Redesigning the heads and some other tweaks to the pushrod to post higher numbers, or making some kind of modification to the DOHC to widen its power band and get better torque?

My thought, quite simply, is that pushrod technology is 40+ years old. In the automotive world, thats antiquated. Overhead cam technology, while not being new, is considerably newer. Only 12+ years old right? Now, I realize that newer doesn't necessarily mean better, but DOHC technology has had time to mature now. American companies seemed to be obsessed with pushrods, maybe because they've been doing it for so long and they're afraid to step out of their comfort zone, or maybe because America wants that kick in the pants without running the engine hard at high rpms, whether its built to do that or not. But they must take notice sooner or later that the rest of the world has embraced OHC technology and is making a killing in thier markets and ours. I think sooner or later we're going to have to get on the band wagon.

One other question: Which gets better gas milage, the pushrod 3.4 or the DOHC 3.4? Cause America wants power and fuel economy and they want it as cheap as they can get it.

The main factor is pumping loss. A DOHC engine will have to move all of that air through 4 valves per cylinder. More total valve area - Good at high revs, when the engine needs more air. Bad at low revs, because the engine has to do more work to pull air thru 2 holes (valves) than thru 1.

For the same reason, pushrod engines do better at low RPM, because they are a more efficient pump. At high revs, they just can't move enough air thru the valves fast enough. Also, at those higher revs, you begin to experience valve float - the valves don't close before the next cycle starts.

Also, due to their design, Multi-valve heads tend to end up with short intake runners - again bad for low-end. Longer runners on a 2-valve head allow for better low-end response, but suffer at high RPM.

Manufacturers are combatting these problems by introducing variable valve timing and variable length intakes. Detroit is just plain lazy, but I think that's apparent in their entire design philosophy, not just powertrains.

In short, you can modify either engine, but one design works inherently better at low RPM, the other high. The DOHC engine will probably get better mileage at the same displacement.

[This message has been edited by Gary W (edited 01-03-2004).]

But either way, both 3.4s will have much more punch than my 2.8 right? Just in case someone doin 5 under the limit happens upon a passing zone and I'm sick of being behind them, or they're doin 35 gettin the freeway and I need to get movin. Thats all the thread hijacking for me now.

quote Originally posted by Fierobsessed: In theory Lets just say there are two cars, same weight same horsepower. One is a rather large OHV, the other a smaller displacment DOHC. These cars have a "Constantly variable transmission" that holds the engine at the RPM at witch the most horsepower is produced. These two cars will run the exact same way down the quarter. Side by side to the end. Why? Because horsepower is actually a measurement of acceleration of a mass. 1 Horsepower can accelerate 550 lbs 1 foot in 1 second, per second. Meaning that a horsepower accelerates a weight at one, and only one rate. FYI, 1 Horsepower is equal to 743 watts. Witch is also a measurement of power as well. So, as long as you use the horsepower efficiently with minimal loss. You will always have the same result. However, there really isn't a good transmission available that can put a high reving engine at its peak and keep it there. You have poor launches, car falls on it's face. The shifts bring the engine out of its power range, once again falling on its face. The whole trick to getting a DOHC engine to work for racing is all in the gearing.

I agree on what´s stated above. A slight correction though: 1 HP = 736 Watts.

I wouldnt ever underestimate a small motor with forced induction...

Stock my Laser pushed 210hp and 215ft/lbs.

$5,000 later

The car pushes about 360hp and 380ft/lbs. (Wheel Horse Power)
Full boost (21 lbs) comes on just before 3,000 rpm and tachs out at 7,500

2 Litre, 16 Valve DOHC

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"Raced That, Wrecked Better" ~In Memory Of Jesse Cesek~ 1980-2000
US Armored Cavalry - Fox 2/81 - Death By 120 - 1 Shot 1 Kill

[This message has been edited by The Fieromaster (edited 01-04-2004).]

Just a thought. How the valves are actuated is not directly related to power output or torque curves. The combustion chamber only sees the valve opening, not the valvetrain, so it doesn't really care how the valves get opened.

That being said, having the cam(s) in the head(s) does offer some advantages and some disadvantages. The biggest advantage is eliminating the reciprocating mass of the pushrods and large lifters. In fact, if you run with the design where the "rocker" arm ends are on the valve stem and hydraulic lash adjuster, with the cam pushing down on the middle, you eliminate the weight of the lifter entirely. This means you can spin the engine faster with less worry of breaking something in the valve train. Most engine designers take advantage of the higher RPM by changing the cam and intake design around to produce more power at higher RPM. This usually has a negative effect at lower RPM, witness the S2000. However, there is absolutely no reason whatsoever that the designer can't use the same valve timing as with a pushrod engine. He would get the same power as the pushrod engine, and the same torque curve.
Another advantage of cams in the heads is that it give the designer more freedom to add more valves. This could be done with pushrods, but would be fairly difficult and expensive.

The big disadvantage of overhead cams is is the cam drive technology. You have to use complicated systems to drive the cams, especially on V engines. Belts are cheaper than chains and run quieter, which is why so many OHC cars use them. As a result, owners are required to spend relatively large amounts of money on preventative maintenance to replace these belts, else they suffer extreme engine damage when the belt breaks. Compare that to, say, our stock Fiero cam drive systems which routinely last the life of the engine without problems.
Ultimately what I want to see is hydraulic actuators driven by electronic valves, or even better, direct valve actuation with electronically controlled solenoids. This would completely eliminate the valvetrain and all that wasted friction and wear, and using an ECM to control valve timing would give you the ability change your engine from a high-overlap horsepower monster to a low-lift, low overlap fuel mizer, all with the flip of a switch.

JazzMan

If you're talking SOHC, I agree. But with 4 or 5 valves per head, you're up against pumping loss again. Especially at smaller displacement. The motor is working so hard pumping air, there's not much to spare for the car. (Generalization, I know)

What they really need to come up with is variable displacement or variable stroke. Then the best of both worlds are possible. Maybe linear actuators on each valve as you suggested, eliminating the cam entirely. I knew somebody at GM who was doing lab work on that once, but it was years ago. They were playing with variable lift and timing, all computer controlled. Had a b!tch of a time keeping all of those actuators firing.

quote Whuffo:In almost all cases, the torque peak comes at or nearly at redline; ...

Should you have stated instead
"In almost all cases, the torque peak comes before redline."

[This message has been edited by 30+mpg (edited 01-04-2004).]

Mercedes has solenoid activated valves in testing and should reach prduction very soon i hope No cam shafts im a gine the rpms you can run as long as the computer can keep up lol.

[This message has been edited by red85gt (edited 01-04-2004).]

I want one of those solves everybodies problem miracle engines JazzMan was talking about!

quote Originally posted by Fastback 86: I want one of those solves everybodies problem miracle engines JazzMan was talking about!

That's why they make the SC3800

The only replacement for displacement - Forced Induction.

quote Originally posted by Gary W: The only replacement for displacement - Forced Induction.

AMEN

quote Originally posted by Gary W: Head Flow. The iron heads suck.

OK, how about comparing the 3400 to the 3.4 DOHC.
Same displacment, and they both have alum. heads.

Awnser: A DOHC doesn't waste power like a pushrod does, AND there are 2wice as many valves. Even though the valves are smaller, they allow a LOT more air through/out. An engine "can" be thought of as an air pump. More air in/out..it's making more power.

Now, for the original question..... Will is absolutley right, there are way too many broad statements made. Gearing, traction, ect.... BUT, looking at the original question.... If you take the original pushrod, and turn it into a DOHC makeing twice the power, why doesn't it cut the 1/4 time in half???

Well it's the difference between making a car that shoots down the 1/4 in 14 sec, and trying to get it down into the 13 or even 12 sec range. Just that 1 or 2 sec difference means you may have to double the original engines power. Now that is a broad statement too, but the point is that just cause you have or can double engine power, it may not yeild you anything unless applied correctly. I would tend to think of hp as a side effect of the production of torque. If you think of it that way, and do the rest of the math,(cars weight, tranny...ect) you see that the limitations for the Fiero isn't really the motor, but a lack of attention to the tranny. A DOHC built to the gills,(or any engine for that matter)is usless if your tranny explodes......

quote Originally posted by Toddster: No one seems to be talking about weight. There is a rule of thumb that in order to wove twice the weight you need four times the horsepower. Today's lightweight engines AND cars are smaller and made of much more alloys, plastics, and composite materials. Did you know that an average Big Block engine NEEDS 70 more horsepower than a small block just to move its own additional weight?! Most of these old engines were designed when cars weighed 4500 lbs and just needed power to cruise. Times have changed.

You might be thinking of speed where it takes 4 times the HP to go twice as fast. (Air resistance, anyway.) Acceleration is based on straight power to weight ratio. 1HP will accelerate 10lb at the same rate as 10HP will accelerate 100lb.

70 more HP to accelerate AT WHAT RATE?

Fieros weigh almost as much as Novas, and you could get them with a 375HP 396. I know the 375 would be different if rated as todays engines are. But if you look at the HP potential of BB heads, it's worth the extra 100lb over a smallblock.

Most BB cars will cruise at VERY little throttle.

GL

Out of curiousity, which engines are used in the different racing circuits, NHRA, Nascar, Formula One etc. And of those using both, which seems to dominate most?

[This message has been edited by Mastermind (edited 01-05-2004).]

quote Originally posted by Gary W: The only replacement for displacement - Forced Induction.

RPM man, RPM... So basically, there are numerous replacements for displacement..

quote Originally posted by Mastermind: Out of curiousity, which engines are used in the different racing circuits, NHRA, Nascar, Formula One etc. And of those using both, which seems to dominate most?

There are virtually no crossovers between the fields. F1 engines are too expensive for anyone else, drag motors don't fit in other classes, and Nascar motors have to last for 500 miles. Different requirements, different solutions.

(Added in edit)
Oh, you mean pushrod vs. OHC! F1 engines are OHC, the others are pushrod, Nascar to (riight!) keep the cost down, and pushrod engines seem to work best for drag racers.

GL

[This message has been edited by Tugboat (edited 01-05-2004).]

Quite possibly If they are not, I stand corrected. However, I believe you mean WWII fighters, as I'm fairly certain WWI fighters did not have OHC technology.

Let me see, there was the Hispano-Suiza V8, used in the S.E.5 & Sopwith Dolphin.

Mercedes had an OHC6 designed in 1911 that later went into Albatross D.III and Fokker D.VII fighters.

(I think those were WWI)

GL

[This message has been edited by Tugboat (edited 01-05-2004).]

Well then I may stand corrected on that as well. Now I'm gonna have to go look that up, cause until 2 mins ago I fancied myself a bit of a war history buff.

Too much to say....no place to start.....head spinning

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'84 Fiero Sport Quad 4 coming soon
'87 Blue GT
http://www.lasvegasfieroclub.com/

So.... the conclusion is that there are too many variables? Does anyone else think we need a better way of rating cars that by horsepower and torque? It's just too easy to fudge the numbers.

I mean, I know someone with an isuzu Trooper that (per the dealer)is supposed to have like 220hp and 260 lbs torque at about 4000-5000 rpms(kind of guessing by what I remember. both were in the 200s). Meanwhile my Cheesy 93 Nissan with it's big 115hp and 110 Torque @ about 5500 RPMS can leave that thing a 1/4 mile back by the time I get to 3rd gear.

I was under the interpretation that it was because it was geared for towing... but based on the numbers.. I should have been te one left behind. Sure weight is a variable... but it shouldn't be THAT much of one.

quote Originally posted by Pyric: So.... the conclusion is that there are too many variables? Does anyone else think we need a better way of rating cars that by horsepower and torque? It's just too easy to fudge the numbers. I mean, I know someone with an isuzu Trooper that (per the dealer)is supposed to have like 220hp and 260 lbs torque at about 4000-5000 rpms(kind of guessing by what I remember. both were in the 200s). Meanwhile my Cheesy 93 Nissan with it's big 115hp and 110 Torque @ about 5500 RPMS can leave that thing a 1/4 mile back by the time I get to 3rd gear. I was under the interpretation that it was because it was geared for towing... but based on the numbers.. I should have been te one left behind. Sure weight is a variable... but it shouldn't be THAT much of one.

Yes there are a LOT of varibles. But I believe that there is also a fair way to judge and compaire. There is a way to look at the most important variables.

Cars weight
HP
Torque
Tracktion (tire size)
Tranny ratio
Max RPM

What else? can anyone add anything?

When I was shopping around for cars in 1995, I test-drove the Big 3 econoboxes: Ford Escort, Chevy Cavalier, and Dodge Neon.

What I found is that the Escort satisfied my "ass-o-meter" better than the other two did. It felt faster, and seemed to have more power, than the other two.

The Neon had 132 HP; the Cav had at least 100. The Escort had 88.

When I told the Dodge guy that I was leaning towards the Escort because it felt faster, he told me that the Neon had that 132 horsepower.

I bought the Escort.

Years later it occurred to me to check out the torque ratings of the vehicles, and I discovered that the Escort made its torque very low. I don't remember the exact figures; only that the Escort made more torque, and at a lower RPM, than the Neon did. Sure, the Neon made more horsepower...but it made it 'way up on the tach, over 5 grand IIRC--a place where I have never driven any car I've ever owned.

The Escort makes its peak torque on the high side of the RPM range that I typically drive at, which is why it felt faster to me. Since I don't normally rev the engine higher than 3500, the Escort was best suited to me. The Neon, IIRC, made its peak torque about 1000 rpm higher than the Escort did, and it was a lower figure (not much lower--one or two lb-ft).

It would take some digging for me to verify these figures--I still have the sales brochures. All these figures are as I recall, and may be wrong. I do remember vividly that the Escort's torque peak is lower than the Neon's, though.

In the end, I guess it really all comes down to what you want to use the car for. I'm not a racer; I want a car with passing power that doesn't require me to downshift 2 or 3 gears. I don't expect to be revving the engine 'way up, either, so a low-revving torque-monster suits my driving style.

The 1.9L Escort produces a lot of torque down low for its size. In slippery conditions it's very hard to get the car moving....

Ed

The other thing to this is that peak #s don't mean that much unless the engine spends all it's time at that peak. A peaky engine may make big #s but it's hard or impossible to keep at peak power. With a wider power range and lower #s you might be faster because you spend less time shifting. Again, it depends on the application. Generally, motors that make power at higher RPM are peakier, but variable cam timing and some other things are helping with that.

GL

I'll put in my 2 cents now. i've driven a 4 spd fiero, and a 5 spd DOHC saturn. these are my observations. when you do the math, the fiero should weigh in around 2650 LBs, the saturn weighs 2350 LBs, so the saturn already has the weight advantage. the fiero however has 140 HP @4400 RPM to the saturns 124 HP @5600 RPM, and the fiero has 170 FT LBs @3500RPM to the saturns 122 FT LBs @4800 RPM so the fiero has 16 more HP and almost 50 more ft lbs. my fiero has a 3.32 final, where as my saturn has a 4.06 final... guess which one is noticable faster???

think about this to, i would shift my fiero around 2-2.5K rpm to be easy on it. and it would move around just fine at the RPM's, the saturn, i shift between 2.5-3K when i'm babying it. and it moves around just fine.
moral of the story, even though it has a LOT less power, and peaks out much higher, it's still got enough low end to get moving. i'll also say this, DOHC's love standards they run much better with them.

well that was my 2 pennies.

-Fish

Another reason why ricers suck. Their engines.

Running an engine at high rpms means less MPG. A reason why the mustang gets better fuel mileage then the WRX.

Low end torque means the engineers can create the best gearing to run at low rpms to be able to run a car without lugging the engine.

be back later.

quote Originally posted by Fastback 86: My thought, quite simply, is that pushrod technology is 40+ years old. In the automotive world, thats antiquated. Overhead cam technology, while not being new, is considerably newer. Only 12+ years old right? Now, I realize that newer doesn't necessarily mean better, but DOHC technology has had time to mature now. American companies seemed to be obsessed with pushrods, maybe because they've been doing it for so long and they're afraid to step out of their comfort zone, or maybe because America wants that kick in the pants without running the engine hard at high rpms, whether its built to do that or not. But they must take notice sooner or later that the rest of the world has embraced OHC technology and is making a killing in thier markets and ours. I think sooner or later we're going to have to get on the band wagon.

http://www.mcnews.com.au/ClassicsCustoms/OHC/camgoingtooverheadhistoricalpiece.htm

Thanks bushroot! Very informative.

I hereby recind all statements made in this thread with regards to pushrods being antiquated and overhead valve technology being newer and superior, on the grounds that I obviously didn't know what I was talking about.

I wasn't saying by any means that OHC isn't superior. I was simply showing you how old the OHC engine really is. I prefer an engine that I can rev the piss out of.

I agree with the comment that Detroit is just lazy. look at the lt series GM V8s. that block casting was designed and the factory tooled to make it in the 1950's. more that 50 years ago. in order to go to OHC they would have had to re-tool and design a new block.

cars today are not the 5k pound monsters that they used to be, so low end isn't as necessary unless you are drag racing. also, if you want the low end, put DOHC on a monster V8 and see what happens. take the N* for instance. anyway...that's my 2 cents