formula79

The 3.4L DOHC V6 was actually a good motor...Iit was poorly packaged however in the W-bodies. GM originally intended to have 280 hp in the engines and they were making more than that on dynos. GM's tranmission guys couldn't make the 4T65 take more than the 220 reliably. That transmission is still hurting GM as they had to cut the 04 Grand Prix's horsepower by 20 because it couldn't take it. The 3.4L was even slated for the GM80 FWD F-body and being lighter and with 280 HP it probaly could have made it close in a race witha 4th Gen LT1. One of my friends had a 3.4L and maintained it good and never had a problem...it ran pretty strong too. basically I don't think it's a bad motor....especially since the Northstar is based off similar architecture.

redzed

The whole point on my criticism is without firing occuring in deactivated cylinders, you don't have counteracting forces that make for a balanced engine.

Another point of criticism is that cylinder deactivation is an engineering cop-out. If you want to save fuel, there are better, and more elegant, ways of accomplishing that goal. Ever hear of gasoline direct injection. The injectors meter out the fuel, not the throttle. The result is an engine which can easily employ lean burn combustion. Of course the only problem is that there is actually too little uncombusted fuel for the catalytic converter to function normally.

Personally, I see cylinder deactivation as offering too small a benefit for the complexity and risk. It wasn't a good idea in 1982, and even if it's practical now, it still isn't worth the additional costs.

If GM wants to improve fuel economy, they should decrease vehicle weights and lower drag coefficients. Better yet, they should increase compression ratios. I've always thought that designing vehicles to run on 87 octane fuel is a foolish economy, meant to placate foolish consumers. There is no reason why every modern car shouldn't run at a 10.5-11.5: 1 compression ratio - except that cheapskate buyers see "regular" grade fill-ups as a necessity. That sort of skinflint mentality is a false economy. If 91-minimum octane fuel remains available, every GM car should require it. How about putting sound engineering before uneducated consumer ignorance?

(As an aside, higher octane fuels did alot for the Allied victory in Europe in WWII. American fighter plains had superior fuel economy and superior flight performance as compared to German fighters. Higher grade fuel was the reason why a P-51 Mustang had the range to escort B-17 bombers all the way to Germany, and still outperform the lighter Axis fighters. Smart Yanks, stupid *****.)

stars1010

Almost ironic how Germany now builds the "superior" cars, huh? Damn *****!

redzed

Any way you slice it, the 3.4L DOHC V6 was a failed engine program. In its waterdown form the 7000rpm redline was a bad joke - the power peak fell at 5200rpms. I can't really blame the 4T65, because it was always meant to be a light duty FWD transmission. No the whole concept behind the 3400 "Dual Twin Cam" was flawed. It was a coarse, unreliable motor. If it had met the original horsepower goals, the power peak would have been to high too function with any torque converter. (I suggest you research all of the unconventional transmission engineering Ferrari had to go through with the high-revving 456 GTA. Incidentally, that RWD car's automatic is based on 4T80E components - wierd!)

The GM80 program was a real train wreck as well. It was over budget, overweight and far too off schedule in develpment. Worse yet, the state of GM FWD chassis engineering in the late 1980s would have made these cars unacceptable from the standpoint of torque steer.

Of course, GM-10 did little better. Singlehandedly, the GM-10 coupes killed the midsized "personal luxury coupe" market from 1988 onward. Worse yet, the mainstream sedan derivatives were late to market and too expensive to manufacture. This is why the sad Olds Ciera survived into near perpetuity. The lousy GM-10 cars played a major part in the long-term demise of Oldsmobile as a volume division.

The 3400 DOHC was just the centerpiece of a disasterous Roger Smith drama. Every product that came out of that era was crap, but GM straightened up, right? With the progress in technology, its surprising that they didn't. The 3.5 liter "Premium V6," was even more inexcusable as a product. GM though that a long stroke design was a good substitue for higher compression and/or variable valve timing. The result was a jerky drivetrain that had far worse drivability than the ancient Buick V6.

The GM of 2003 is far different than the GM of the recent past. Does that mean I'd blindly buy their technological "innovation?" There's no such thing as blind faith when it come to the General.

Z28Wilson

Ok so the additional cost of DOD isn't worth it but you want GM to require people to use premium gas in all of their cars? Good luck getting people to go for that! Besides, with the sophisticated knock sensors engines have today, there have been studies that suggest premium fuel isn't necessary in just about any engine in production right now. In your performance motors you may see a very slight performance difference, but premium gas is not as necessary as it used to be. The LS1 will run on midgrade flawlessly.

Darth Xed

What does the DOHC 3.4 from 10 years ago have at all to do with D.O.D.?

Even less that the old Cadillac 8-6-4.



Everything I've ever read on D.O.D. says it is completely transparent.

91_z28_4me

I beg to differ about the LQ1. As the current owner of the car I feel compelled to tell you that you are WRONG! The motor is great. Yeah I had to put a few bucks into it when I bought it with a little over 50K miles. But it was a lease car that had probably not been given the best life. Now you think the motor is weak. Why don't you cruise on over the Fierl.nl and look up a guy named DOKV or something like that. He is building a BAD A$$ LQ1 and putting it into his Fiero rebody. Also maybe you should tell us about your experience with this motor.

A lot of GM engines have gotten bad wraps. For instance the original LQ4 was the 2.5 liter 4 cyl. Yes in 84 there was quite a few engine fires due to weak connecting rods. But now that little motor is called the IRON Duke because of its lasting power. Maybe you should check your facts about the LQ1 because with proper maintainence they will last just as long as any other GM motor.

[/rant mode]

rdbowtie

i would just like to correct one thing in this post the lq1 was not matted up to a 4t65,,, however it did get a 4t65E , there is a differance in the transmission's also i happen to own a 87 camaro rs with a 305 (i put in from the 2.8) and my 95 monte z34 will outrun and out last that 305 any day of the week now if you asked about the 91 ta i have that i am currently putting a 350 with a few "extra parts" not stoping at nitro i have a feeling this is going to be a fast *** car.


sure the lq1 has problems ill give you that but its a great car to drive i have surprised alot of people in the f-body club around here with it

PacerX

"The whole point on my criticism is without firing occuring in deactivated cylinders, you don't have counteracting forces that make for a balanced engine."

Balance issues are not due to firing. Actually, most of the engine balance issues are centered around the reciprocating mass - ever notice that firing is never part of dynamically balancing an engine??? Firing order is part of the consideration, but a secondary issue as the force put on the piston at varying levels of combustion cannot be accurately simulated across the entire range. Go ask a machine shop to simulate dynamically balancing a engine including firing sometime, then have them write here and tell us how much time they spent laughing at you.

Finally, cylinders can also be deactivated sequentially, meaning that a 4 stroke in effect turns into an 8 stroke motor. This is exactly how the Northstar "limp-home" mode works - which was, BTW, the genesis of the idea.



"Another point of criticism is that cylinder deactivation is an engineering cop-out. If you want to save fuel, there are better, and more elegant, ways of accomplishing that goal."

I beg to differ. First, any discussion of "elegance" that doesn't involve cost is stupid. The FW-190 was an "elegant" solution in some respects, but the P-47D was capable of attacking it with impunity (get height, make a pass, dive out... if you kill the FW-190 that's great, if not, come back around for another pass at your leisure as he'll never catch you in a dive - either way, you live to fight another day).

"Engineering snobs" sometimes forget that the sledgehammer is occasionally the most elegant tool for the job.



"Ever hear of gasoline direct injection. The injectors meter out the fuel, not the throttle."

ALL sequential multi-port fuel injected engines meter fuel independant of the throttle. In GM powertrains a MAF (mass air-flow meter) determines the amount of air that is passing into the intake manifold, the PCM takes information from a number of other sensors (intake air temperature, oxygen sensors, knock sensors, etc...) and then compares it to a table supplied in the PCM. Decisions are made based on that table as to injector pulsing. The TPS (throttle position sensor) is merely one of the variables in the information table. The throttle at 90% open with a low MAF flow rate creates different conditions than a throttle at 90% open at 5600 rpm and a high MAF flow rate.

Newsflash: GM cylinder deactivation is less expensive than gasoline direct injection right now.



"Of course the only problem is that there is actually too little uncombusted fuel for the catalytic converter to function normally."

Oxygen sensors are part of the closed loop operation of the system, they determine whether the mixture is too rich or lean. That's why there are 4 of them on an LS1 - a before and after cat measurement of residual oxygen is taken.

Uncombusted fuel is universally a bad thing in exhaust. It destroys catalytic converters and is the contributor of the worst of the noxious emissions. Less uncombusted fuel is ALWAYS better.

Any start-up issues with lack of residual heat to "light-off" the converters can be approached a number of ways (pup cats, cat heaters, etc...).



"Personally, I see cylinder deactivation as offering too small a benefit for the complexity and risk."

Ummmm.... a whole bunch of folks at GM Powertrain disagree with you. I'll stick with their expertise, thanks.



"It wasn't a good idea in 1982, and even if it's practical now, it still isn't worth the additional costs."

Reference the above statement concerning GM Powertrain.



"If GM wants to improve fuel economy, they should decrease vehicle weights and lower drag coefficients."

Oh, this is pure genius. No screaming eagle ****. Guess that's why the GM v8's WEIGH LESS and are PHYSICALLY SMALLER THAN the competition's.

K, Einstein, show me a powertrain that makes more power than an LS1, gets better fuel economy and weighs less.

BMW M3? Nope.
Honda S2000? Nope.
ANYTHING from Mercedes? Nope.
Ford? Nope.
Nissan? Nope.

I'm waiting.....

Did you know that LS1 Camaros weigh less than Mustang GT's? Did you know that Corvettes weigh less than Porsche 911 turbos?



"Better yet, they should increase compression ratios. I've always thought that designing vehicles to run on 87 octane fuel is a foolish economy, meant to placate foolish consumers."

Oh yeah, folks who buy Impalas and Malibus REALLY want to spend 20 cents more a gallon for premium. This is silly beyond words. 20 cents a gallon adds up REAL quick, and that is a direct cost of ownership - and we're supposed to take this as the "more elegant" solution????

I think a much stronger case for "elegant" engineering can be made for a powertrain that out-powers and torques the BMW M3, gets better fuel economy, is smaller, has less parts, and weighs less.... and can swallow up mid-grade all day long.



"There is no reason why every modern car shouldn't run at a 10.5-11.5: 1 compression ratio - except that cheapskate buyers see "regular" grade fill-ups as a necessity."

I'll pay 20 cents more a gallon for gas in a car that'll rip off a 12-second quarter mile. In the wife's grocery-getter, I won't. See, that's the part about "elegance" you simply can't comprehend - "elegance" is never cost-independant, and a solid case can be made that cost is the #1 driver for any automotive engineering solution. If you're an engineer, I suggest you burn your diploma... whatever school gave you your degree failed miserably in teaching you fundamental engineering principles.

Remember:
"Any moron can engineer a Rolex, the real engineers work for Timex."



"That sort of skinflint mentality is a false economy."

K, let's see you justify an extra $800 to the bottom line of the cost of owning the car just for gas (100,000 miles, divided by 25 miles to a gallon, times .20 per gallon...), PLUS added expense for more durable powertrain components (more compression = a bigger "boom" = more stress).

This kind of reminds me of my tractor. I have a Farmall Cub that only makes about 8hp from a low-compression gas motor. 8hp isn't much, but it makes a BOATLOAD of torque and would tear the rear axle right out of my +400hp Camaro in a pulling contest. My LAWNMOWER makes twice as much power as my tractor... but guess which one can pull a car out of a ditch? The issue is always having the right tool for the job.



"How about putting sound engineering before uneducated consumer ignorance?"

How about figuring out what sound engineering is?

Darth Xed

PacerX =

guionM

I had to sit out this one.... it's a bit over my head.
(I do know when to shut up when I don't know what I'm talking about )

Z28Wilson

Thanks for chiming in PacerX. I'm no "injuneer", for a variety of reasons, but I always found the way things work pretty fascinating. I too figured out long ago that the biggest consideration in engineering is not how to get it done, because any engineer can do that, it's how to get it done with the lowest bottom line. Simply asking everyone to buy premium may be more cost-effective on the engineering side but when you aren't selling any cars because no one is willing to use expensive gas, how much are you saving?

I must say my only concern with DOD is idle and cruising sound. I don't think it'd be right to listen to a beautiful C6 Corvette with a noticeable 4 cylinder buzzing at a stoplight. I wonder how much consideration "traditional" sound was given when developing this technology. Maybe you could speak about that?

redzed

Any modern engine with a knock sensor will run on lower grade fuel, but only at a sacrifice in power and fuel economy. Running an LS-1 on 87 or 89 octane fuel retards the timing, meaning that you're burning more gas. Trust me, it isn't a savings.

I run premium octane fuel in all of my vehicles, even the older ones with relatively low factory compression ratios. Over time, carbon build-up insures that the compression ratio is effectively "raised." The higher octane removes compression knock worries. Right now, I'm getting better fuel economy out of 100K+ vehicles than when there under waranty.

If anyone out there is stuck with a low compression, early emissions control era small-block, the single greatest performance enhancement I can suggest is substituing a thiner head gasket. For the mere cost of 93 octane premium fuel, you can get an appreciable increase in performance and even fuel economy. It's more effective than pulling a constrictive, old-school catalytic converter.

Even if the buyers are to cheap to buy premium gas, raised compression ratios would still increase GM's CAFE averages. As I see it, a cheap, risk-free engineering solution is always better than reviving the failed and costly DOD concept.

formula79

What are you becoming the 5th Gen forum's anti christ?

PacerX

Guys, thanks for the compliments.

First, I would like to point out that just like any other profession, engineering is not populated 100% with people who are actually good at their job. Sometimes, "laymen" (I hate this term... it's kind of arrogant) come up with the best solutions simply because they have common sense and are smart. Henry Ford didn't have a doctorate in engineering... Anybody can figure all of this stuff out, and can do a great job at it. Some of the best engineers I have ever met were actually designers (draftsmen) with lots of experience and ZERO college. Watching these guys run circles around GMI/MIT graduates was a favorite pastime of mine.

There is a saying that is a decent rule of thumb in many cases:

"In product engineering, your usefulness is inversely proportional to your level of education."

The sad part about it is that the educational system has done a wonderful job of cramming facts down the throats of young people, but still can't figure out how to get them to THINK.



"I don't think it'd be right to listen to a beautiful C6 Corvette with a noticeable 4 cylinder buzzing at a stoplight. I wonder how much consideration "traditional" sound was given when developing this technology."

There are whole groups of folks at GM whose only purpose for living is to make sure the exhaust system sounds "right" for a given vehicle. As an example, Corvettes are generally quieter than Z28 Camaros because the Corvette buyer EXPECTS a more refined sound and Camaro buyers like their car louder. This isn't a mistake.

Nifty things can be done with exhaust note. If you throw enough money at the problem, you can actually make a 4 cylinder do a pretty good impersonation of a V8. But remember, that at idle and part throttle, much of the mission of the exhaust system is to make a little noise as possible.

Let's hope they don't screw this one up. I've got pretty good faith in them.... most of the time...



Now, just to prove that GM doesn't always get it right, take a look at the intake system in an LS1 Camaro. The resonator and lid had ALL KINDS of money thrown at them to quiet down the intake noise.

In my mind this borders on criminally dumb.

Z28/SS/WS6/TA buyers LIKE intake noise. We think it's pretty cool. Heck, some of us used to reverse our air cleaner lids just to get that "giant sucking sound" when our 4-bbl carburators opened up. Give me an extra 5-10hp along with the intake noise and I might just have an orgasm.


But remember, this is a MARKETING FAILURE, not an ENGINEERING FAILURE. Marketing screwed up and specifed all kinds of nonsense to quiet down our cars and engineering went to town making it happen like the good little soldiers they are.


The problem came when the engineer who figured out all the money it was going to take didn't call the guy in marketing and say:

"Hey knucklehead, this is a Camaro. Did the idea that our target market LIKES intake noise ever occur to you??? Furthermore, I can wring out another 10hp AND give you better fuel economy."