germeezy1

GM actually admitted they dropped the ball with the 3.4 DOHC..you should do some reading on its development. The motor design was a very solid engineering idea that was let down by lack of a suitable transmission. They had development 3.4's that had no problem revving to 7,500 rpm and making about 260-270 hp at the flywheel.

Thats one of the problems with OHC engines is the same things done to them to give them more low end torque and a more tractable powerband to work with an automatic especially a 4A also compromise the power that could be had at higher rpm.

People keep acting like there are no trade offs to high rpm, smaller displacement DOHC engines. Thats why alot of small cars that are exciting with a stick are dog slow with an automatic.

Look at the Ford 4.6 and 5.4 3V if you want a good idea of why it is a bad idea to try to make a OHC motor behave like a pushrod engine.

black_knight

iTrader: (1)

Hard to say. Did he say it out loud first? Are we, colloquially speaking, "speaking," here? (LOL)

The old, distinct use where slander meant specifically spoken slurs is falling out of use. I don't know how I feel about that. Maybe I should lament and resist it as degeneration of the language.

black_knight

iTrader: (1)

And as I said, Ford actually admitted they dropped the ball with the 4.6. That doesn't stop the nutriders here, though.

DanO

LOL

engineermike

The 4.6 '03-'04 Cobra is pretty well-known for making 800+ rwhp with a twin turbo conversion using a completely stock long-block.

You're right, it's a whole other discussion. But consider 3 things: 1) Crude oil is a finite resource that will one day run out, 2) We've already used 1/3 of the known crude oil, and 3) Demand is rising, especially in China. Draw your own conclusions.

Mmmk. . .

engineermike

It's funny that every LS1 guys just knows that Ford totally "dropped the ball" and "missed the boat" with the mod motor. Apparently, Ward's has some clout:

http://en.wikipedia.org/wiki/Ward's_10_Best_Engines

Granted, they're taking into account more than just hp/lb (though none of them are turds), but Ford must have not totally dropped the ball since the mod motor made the list 8 times in the last decade and the LSx only made it twice. Also, there are an awful lot of OHC and DOHC engines on that list. . .

engineermike

Okay, I'm having trouble coming to terms with you not believing that the manufacturers have the ability to altar gear ratios independent of one another.

Example:

Gear__Ratio__Final Drive (w/ 2.73 rear)
1st:__3.00___8.19
2nd:__1.73___4.72
3rd:__1.00___2.73
4th:__.700___1.91

Soooo. . . you change the motor to a smaller one that makes more hp, but less peak torque. You change the rear gear to get the same torque at the rear wheels, then modify 4th gear to get cruise back down. You end up with:

Gear__Ratio__Final Drive (w/ 3.42 rear)
1st:__3.00___10.26
2nd:__1.73___5.92
3rd:__1.00___3.42
4th:__.560___1.91

Now, you have the same torque to the rear wheels in 1st, 2nd, and 3rd gear, more hp, and get greater gas mileage. If you don't think this is possible, please explain to me why it can't physically happen.

It's been proven that, in the same vehicle, with the same gearing, and same configuration engine, the smaller displacement motors get better mileage than the larger ones. It's also been proven that a motor fitted with 4v heads gets the same mpg as the same motor with 2v heads, but makes 50+ hp more. Furthermore, it's been shown that the smaller motor with 4v heads makes more power than the larger motor with 2v heads (again, with the same engine configuration).

Therefore, there is most certainly an economy advantage to reducing displacement, increasing cylinder head flow by using a 4v arrangement, re-gearing appropriately, and you don't even have to give up full-throttle performance.

engineermike

http://www.fastcoolcars.com/2000-cobra-r.htm

engineermike

(about the Hayabusa v-8) How is it that "there isn't anything even remotely like it out there", when the engine is simply 2 stock Hayabusa 4-cylinder engines spliced together at the crankshaft? Every Hayabusa sold has an engine just like it!

FieroZ34

iTrader: (1)

It was not. It was a stock Cobra, with a pulley (You know what those are right?), a tune, headers, and cut outs (Under $1000).

And I raced them in the highest output LS1 F-body that you could order (345hp SLP Blackwing/CME/Auburn Diff M6), and got my *** handed to me.
It applies to both the factory cars (Lumina Z34 and Grand Prix GTP), anf the Fiero, of which both classes have similar weights, one being a heavy FWD, the other being a light RWD. 5-speed vs 5-speed, same results every time. For the automatics, the 3800 will take a 3.4 off the line, but by 30mph the DOHC will have stopped the pull. However the 3.4 was available with a 5-speed, and once it got one, it can take a GTP from the line without a problem. So a half liter and a bigass blower, and it still doesn't make enough torque to beat my 7,000rpm DOHC off the line.

Without a doubt the 2.8 has low displacement for its size, the 3900 is essentially the same 60* block! The point was, black_knight was sure DOHC makes your engines stick through the hood, when that's completely wrong. The engine is significantly wider, adding about 3", but he said height, not width. And even though it is wider, it still fits pretty easily, as it did in every car it came in. And the maintenance is still easier than the 2.8 (Including spark plugs).

It seems your quite educated on a subject you know jack **** about. Let me correct your ignorance. GM did not drop the ball whatsoever. When your Lumina can hold the bumper, and in the 5-speed's case walk away from, your IROC Camaro, you didn't drop the ball. And they do.

The engine was not "very solid engineering," I don't know where the f*ck you got that from. The oiling system isn't capable of the 7,000rpm it turns, the fuel injectors won't let the car idle, the intake manifolds are worse than many I've seen, the cam carriers are big, heavy, and don't allow higher lift cams, the timing belt breaks with half the miles of the "Suggested service time," and God knows what else. Lack of a suitable transmission? What crack are you smoking, because Dallas could use dealers like you. The Getrag 284 was and is the strongest FWD, manual transmission GM has ever put in a production car. I push over 450hp and 7,200rpm through one on a daily basis. The automatic 4T60e is plenty capable of the power. HP doesn't kill transmissions, torque and RPM do. The 3.4l DOHC is no torque monster. And the automatics shift out at 6200rpm. And GM has billions and billions of dollars in R/D, if you don't think they can build a transmission to handle 225hp and 6200rpm, again, Dallas needs some good crack.

It's very easy to get a 3.4 to rev that high, even higher, but the tradeoff is 25wtq from 3500rpm to 3500rpm. And in case you're a retard and hadn't noticed, the factory doesn't need a 8,000rpm screamer in a 3400lb grocery getter with a slushbox 4-speed. So they gave it long intake runners, a small throttle body, and tame cams. Perfect, more low end and midrange torque than the competitor, and more than their 3400 OHV engine, and yet it still opens up at 3500rpm, pulling strong to 6500.

This "Problem of your's" is just as bad, if not worse, than the pushrods. The 3.4 DOHC makes more low end torque, more midrange torque, and more high end horsepower than the same displacement OHV engine. It's better from idle to redline. At it gets better mileage, fits the same vehicles, uses the same transmissions without issues, weighs just slightly more (I think 10-15lbs), and has plenty of potential (Over 60whp can be added for under $500). It doesn't behave like a pushrod engine at all, things actually happen when you mash the gas pedal.

FieroZ34

iTrader: (1)

Here is how to make an otherwise stock 3.4 DOHC a real screamer. Remove the intake manifold, bolt on a big aluminum box with a big throttle body. Retime the stock cams, and tune the car. Go drive, and be really pissed as you hit 3500rpm and it falls on its face. Then 5,000rpm rolls around. Woah....

Krom

No one has answered my 218 hp/l with 0 valves and 0 cams, with the only moving parts being crank, rods, and pistons.

That dyno chart may have a nice peak, and be ok for racing (assuming you can get the proper gears in a trans axle) but would suck for day to day driving, a yugo would be quicker in traffic, and off the lights

FieroZ34

iTrader: (1)

Exactly, that's why GM tuned it down. To be honest, with a 5-speed and in the Fiero it was a blast, literally perfect. But once in a 600+ lb heavier Lumina, with a slushbox, it'd suck. But even tuned down the engine was still quite potent. And GM tuned it down for a very simple reason. A 260hp Lumina would have walked their Corvette. And that can't happen. So it got tuned down so it ran right with the competitor, a SHO Taurus.

mzoomora

iTrader: (36)

First, most 4 cylinder engines (or smaller displacement) are not going to make real good low end, so cruising at real low rpm's is not going to be easy. With the gearing you are talking about and a low torque engine it would not be a good driver. Even some V8's would not like that final drive below say 1800 rpm, just look at how many guys say that 6th gear is way more usable with a shorter gear.
Also, your city driving gas mileage will suffer. Up until you reach 4th gear you will be turning approx. 25% more rpm's, and that tall of a 4th gear will be hard to use in most city driving. So increased wear on the engine.

engineermike

I never said otherwise. That IS the tradeoff. A smaller motor with more power, but geared for mileage will be a slug in top-gear roll-on.

I'm not 100% sure on this one, but I think the shorter low gears will make the vehicle accelerate from a stop with less throttle, so it shouldn't affect city mileage.

Mike

engineermike

The 250 dirt bike 2 strokes are making about 220 hp/liter stock. 125's are around 280.

The moto GP 500 cc 2-strokes had up to 380 hp/liter and reportedly had more available but they limited them due to traction. The highest I've ever heard of is the GP 125's, which were making 56 hp, for almost 450 hp/liter.

If you don't like the power delivery of a DOHC motor, then you SURE won't like a 450 hp/liter 2-stroke!

Unfortunately, I see the market moving away from 2-strokes. MotoGP 2 strokes are dead and they are phasing them out in the dirtbike market also.

Mike

B T

Originally Posted by engineermike
Okay, I'm having trouble coming to terms with you not believing that the manufacturers have the ability to altar gear ratios independent of one another.

Example:

Gear__Ratio__Final Drive (w/ 2.73 rear)
1st:__3.00___8.19
2nd:__1.73___4.72
3rd:__1.00___2.73
4th:__.700___1.91

Soooo. . . you change the motor to a smaller one that makes more hp, but less peak torque. You change the rear gear to get the same torque at the rear wheels, then modify 4th gear to get cruise back down. You end up with:

Gear__Ratio__Final Drive (w/ 3.42 rear)
1st:__3.00___10.26
2nd:__1.73___5.92
3rd:__1.00___3.42
4th:__.560___1.91

Now, you have the same torque to the rear wheels in 1st, 2nd, and 3rd gear, more hp, and get greater gas mileage. If you don't think this is possible, please explain to me why it can't physically happen.


>>>
You "still have the same tq" going to the rear wheels and less MPH being generated per gear, which should give better acceleration?

I thought gear reduction is a tq multiplier at the rear wheels...which would be after the enigne...

Am I totaly lost now?



and less MPH being generated per gear.<--- this was a typo.


This keyboard is so fired!

B T

Gear__Ratio__Final Drive (w/ 3.42 rear)
1st:__3.00___10.26
2nd:__1.73___5.92
3rd:__1.00___3.42
4th:__.560___1.91


>>>
I'm not sure, but I just might like that combo of gear sets in my car.

Not really sold on the 3rd gear 100mph+ trap though...would love to test drive it for sure.

germeezy1

You Fiero boy are a moron, you also fell for my trap. Maybe I should have mentioned that I was recruited and groomed to be a GM tech and never decided to. I also got to see and talk to alot of GM R&D guys(my uncle being one of them) when I lived in Detroit.

Read Below and you will see that I know even more about the engine in your car than you do.

The 3.4L DOHC motor was designed with a CHEVY name, and was slated to go into the W-10 body cars, namely the Lumina, Grand Prix, and Cutlass. Buick opted to go with their 3800 Series I V6. Target date was 91 model year, as Lumina Z34's, Grand Prix GTP's, and Cutlass Supreme Internationals. In that order. A funny thing happened on the way to the assembly line....When it was orginally concepted , the little Quad was pushing almost 200hp on 4 Jugs. So the V6 needed to have some more power. Now GM at that time was not know for a good FWD Transmission. Even the rocket 180 HP quads in N-body cars came with 5spds only. No auto was offered as HI-PERF, quite frankly because they wouldnt live behind the motor (remember we have to warranty the car if it breaks). Well, the GM engine gurus went to their counterparts at GM Hydramatic, with a challenge. Build a FWD auto trans, that will take 275 HP. You have 2 years to be in production. In a car. Warranty and all. Hydramatic said, "no problem". Meanwhile, the 2.8L V6 had grown to a 3.1L and was currently in use in the W-10 cars. The 3.1L was redesigned as an overstroke version using a cast iron block. To this went the best that GM had to offer, remember we're building a 275HP FWD muscle car. Forged crankshaft, forged rods, forged pistons, balanced lower end. Revamped oiling system with high volume pump. An oil cooler. On top, a pair of computer designed 4 valve per chamber aluminum heads, with hemispherical combustion chambers. Cross-Flow intake and exhaust ports, designed for maximum flow at high RPM. Next, add FOUR, count 'em FOUR camshafts, each controlling 6 sodium-filled lightweight valves. Dual dampner springs rest under a "bucket"type cam lifters, for instant and precise valve timing. The cams were supported by 4 journals each, providing durability along with the least amount of valvetrain mass. The cams were driven by a cogged belt, further reducing mechanical drag of the motor. The exhaust was cast iron manifolds, large by any standards, with a single high flow catalytic converter using 3inch downpipes. All 3.4L cars used a dual muffler system, which not by coincidence, is mathematically perferct in diameter and distance for performance applications. The intake was a tuned tunnel ram, with the early builds using NO mass air flow sensor, and 94 and later ones using one. Add to this combination Fuel injection, digital EGR, and it was by far, the BEST motor that GM engineers could build for its application. Emission certification verifed an honest 281HP on the sheets. Emission 7000RPM screamer. This was in early 1990, January I believe. Transmission? Anyone? Hydramatic had its own challenges to conquer. The THM125 3 speed was being redesigned every year, to combat the next weakest link in the unit. The THM 440T-4 four speed auto debuted a few years earlier, but was prone to valve body and erratic shifting problems. The 440T-4 also had this quirk of self-destructing if the owner happend to get stuck in snow. Not much to build from...Hydramatic had its hands full on this job. An all new FWD O/D trans was needed. Many prototypes were tested at GM proving grounds, in believe it or not, a V8 FWD Camaro. Each version had uncovered problems, aka "The next weakest link". Time was fast running out. When it came clear that the all-new trans wouldn't be ready for production by mid-1990, there was only one thing to do. Redesign the 440-T4 as best as they could. Hydramatic went to the market with their finished product just days before the deadline. Will it take 275HP? NO! Will it take 250HP? NO! How bout 225Hp? Maybe. GM engine ground was peeved! All this effort, just to be cut down at the flywheel....225HP? I want 275! Well, the rest is corporate decision making at its worst. Cut the horsepower of the 3.4L to 200 with an automatic. You can have 210 on a stick. Makes a guy want to cry, don't it? Well, warranty concerns led the list of "why" and there's no way around it. The redesigned THM 440-T4 was designated the THM 4T60E, with an early RPO code of MXO. Internals were beefed up, a heavier drive chai, a better pump, and best of all, Electronic shifting! Now, instead of finicky hydraulic valve body, all shifts and timing ere controlled by the ECM. The same one used by the motor. Big, beefy driveshafts were installed into the W cars to take the power. (on a side note, I have never heard of one breaking) By this time, tooling up was underway for the '91 model year. While there were a supply of motors, the trans were still being built a few at a time. Delco electrionics solved the horsepower problem by cutting the fuel delivery and spark advance curves of the motor. This weakened it to a 6250 shift point, and 6500 rev limiter. Free-reving was limited at 3000RPM. The first 3.4L DOHC engines were spoken for by CHEVY. After all, it was their project. Stick models didnt get orders, as most dealers preferred the auto trans models because of sales. Add to the problem, af HEFTY price tag on the motor combination, adn they were a tough sell as lot inventory at the dealers. The trans shortage had eased by Feb. of '91, and finally some units were released to Pontiac for production. These facts conclude that '91 models are scarce, some Z-34's, a lot less GP's, and virtually no Cutlass. 1992 was a carryover year for the 3.4L option. Pontiac changed wheel cap centes. This was the only visual change from the '91 cars, save the VIN of cours.

Alvin

iTrader: (2)

Good thing, the emmissions are terrible!