Jump to content

  •  

Replying to Premium Six for Caddy and Buick


Post Options

  or Cancel


Topic Summary

Posted 06 November 2010 - 08:44 AM

Speaking of smoothness...

High tech doesn't mean smooth and refined. I know a lot of people don't want to hear this, but the 3.5 Pushrod V6 in the last generation Malibu and the G6 was smoother and more refined than the 3.6 liter DOHC DI-VVT engine in the Camaro. Don't believe me? Go drive both. It's significant in enough that you don't even have to do it back to back to register the difference. Now the Lacrosse and the CTS have plenty of insulation to mute the engine, but in the Camaro it has a grainy, coarse, groan that's very annoying from 4500 rpm on up. Rougher than the 2.4 liter four IMHO. Even at 3000~4500 its worse than the Pushrod V6.

Maybe its the higher compression leading to higher combustion noise. Maybe its the plastic valve covers and intake manifold. Maybe its something else, but the engine is irrefutably coarse.

One thing GM ought to consider is a balance shaft. Even though 60 deg V6es generally don't have them because they are reasonably well balanced as is, they CAN benefit from one. A 60 deg six is NOT perfectly balanced like an I6 or a H6, its just better than a 90 deg six in this regard. In fact, if anyone remembers, the Twin Dual Cam 3.4 V6 (LQ1) from the early 90s is a 60 deg V6 with a balance shaft. The engine was built on the pushrod 60 deg block, but had belt driven DOHC heads added. It had a balance shaft where the in-block cam normally was. The motor was not without its failings in terms of reliability and especially serviceability -- the amount of dis-assembly needed to just get to the spark plugs borders on the ridiculous -- but it was one of the smoothest V6es ever.


i'll take issue with that to a point. first off, and i know this is a third party observer pointing it out, but most magazine reviews I read on the 3.5v6 whether it was in a saturn vue or a saturn aura etc. in comparison tests they did not speak favorably of the NVH of that powertrain, even in comparison tests against 4 cylinders from other makers.

my own test drives of the aura and other epsilon cars with the high feature vs. the 3.5, the 3.5 is not as refined as the high feature was. so i would disagree the first part of your post.

Posted 05 November 2010 - 07:28 PM

Speaking of smoothness...

High tech doesn't mean smooth and refined. I know a lot of people don't want to hear this, but the 3.5 Pushrod V6 in the last generation Malibu and the G6 was smoother and more refined than the 3.6 liter DOHC DI-VVT engine in the Camaro. Don't believe me? Go drive both. It's significant in enough that you don't even have to do it back to back to register the difference. Now the Lacrosse and the CTS have plenty of insulation to mute the engine, but in the Camaro it has a grainy, coarse, groan that's very annoying from 4500 rpm on up. Rougher than the 2.4 liter four IMHO. Even at 3000~4500 its worse than the Pushrod V6.

Maybe its the higher compression leading to higher combustion noise. Maybe its the plastic valve covers and intake manifold. Maybe its something else, but the engine is irrefutably coarse.

One thing GM ought to consider is a balance shaft. Even though 60 deg V6es generally don't have them because they are reasonably well balanced as is, they CAN benefit from one. A 60 deg six is NOT perfectly balanced like an I6 or a H6, its just better than a 90 deg six in this regard. In fact, if anyone remembers, the Twin Dual Cam 3.4 V6 (LQ1) from the early 90s is a 60 deg V6 with a balance shaft. The engine was built on the pushrod 60 deg block, but had belt driven DOHC heads added. It had a balance shaft where the in-block cam normally was. The motor was not without its failings in terms of reliability and especially serviceability -- the amount of dis-assembly needed to just get to the spark plugs borders on the ridiculous -- but it was one of the smoothest V6es ever.

Posted 05 November 2010 - 02:28 AM

point is, the engine needs to be agreeable in all parts of the rpm range, as the driver will use all parts of the rpm range at times.

Ding, ding, ding, ding! We've got a winner. This is especially true for a CVT, which puts you in the optimum RPM all the time.

Posted 04 November 2010 - 10:33 PM

Actually, it's most of it has to do with the fact that motorcycle engines that rev to 12,000 rpm also have pretty small cylinders, somewhat tiny pistons and, most importantly, pretty short strokes. Engine vibrations from the reciprocating mass is a function of the mass of the reciprocating mass (piston and rods) and the square of velocity (piston speed). You are building and reversing the kinetic energy of each pistons two times per revolution. Kinetic energy is 0.5MV^2. So, lighter mass helps somewhat. But, having shorter strokes help tremendously.


but that's exactly my point, a larger car engine should have no excuses at all for smoothness at little more than half the rpm of the tiny motor.

Posted 03 November 2010 - 05:56 AM

some motorcycle engines can run 12,000 or 13,000 rpm, and they are smooth at that speed. why? engineering effort and manufacturing effort and design. point is, the engine needs to be agreeable in all parts of the rpm range, as the driver will use all parts of the rpm range at times.


A motorcycle is smooth at 12,000 rpm because their pistons are 1/3rd the size and the stroke is 1/3rd as long, and you wouldn't want to drive a car with a motorcycle engine in it because you'd need all 13,000 rpm just to get to 45mph in a reasonable time.

The engine does need to be agreeable in all parts of it's designed rpm range. The problem with the 3800 was GM trying to make it do what it wasn't meant to be doing. A 6-speed auto with appropriately spaced gearing and a tall final drive would have helped the 3800 remain competitive longer.

Posted 03 November 2010 - 03:34 AM

some motorcycle engines can run 12,000 or 13,000 rpm, and they are smooth at that speed. why? engineering effort and manufacturing effort and design. point is, the engine needs to be agreeable in all parts of the rpm range, as the driver will use all parts of the rpm range at times.


Actually, it's most of it has to do with the fact that motorcycle engines that rev to 12,000 rpm also have pretty small cylinders, somewhat tiny pistons and, most importantly, pretty short strokes. Engine vibrations from the reciprocating mass is a function of the mass of the reciprocating mass (piston and rods) and the square of velocity (piston speed). You are building and reversing the kinetic energy of each pistons two times per revolution. Kinetic energy is 0.5MV^2. So, lighter mass helps somewhat. But, having shorter strokes help tremendously.

Posted 02 November 2010 - 10:55 PM

With so many less brands within GM these days why not return to unique size engines for those brands? My thought would be like the Ecoboost line at Ford but unique to each brand. Say Chevrolet uses an efficient 1.5L DI Turbo I4 and a 2.5L Di Turbo V6 to replace today's larger normally aspirated engines? While Buick does a 1.8L DI Turbo I4 and a 2.8L DI Turbo V6 and a 3.8L like V8. That would let Cadillac use a more premium 2.0L DI Turbo I4 and a like 3.0L V6 and even a 4.0L DI Turbo V8? They could keep the SB V8 advanced with DI and other tech for trucks and performance cars while using the smaller DI and Turbo engines listed above for standard and luxury car models.

Posted 02 November 2010 - 10:30 PM

Let's see here... no, no, no, no, and no.

NO #1: The need for 6,500 rpm smoothness to pass people? Two words: Racing Diesel. If the torque comes on much stronger at a lower RPM, you engineer the gearbox accordingly.
NO #2: Any engine can be smooth at 3,000rpm? Two words: Quad-Four.
NO #3: Smooth at 6,500 RPM has nothing to do with "solid" engineering. It has everything to do with the size of the reciprocating mass. With a properly configured 6-speed automatic mated to both, I'd pit even the LT-1 against a Nissan VQ any day of the week for solidness.
NO #4: Why is 6,500 rpm the cut off for smoothness requirement? Run a Honda 2.4 up to 8,500 rpm and see how smooth it runs then. Running an engine outside of design parameters will get you unpredictable operation. The 3800 was never intended to be run up that high.
NO #5: The 3800 was done in by it's lack of VVT and it's packaging requirements being a 90 degree engine. The 3900 is a lot smoother than the 3800 was simply because of the cylinder bank angle change. Where GM let both engines down was pairing it with the 4-speed automatic. If either of those engines had a 6-speed auto that was able to keep it in it's designed RPM range, there wouldn't have been so much complaining about it. Don't start an idiotic horsepower per liter argument, it's already been a long day for me.


some motorcycle engines can run 12,000 or 13,000 rpm, and they are smooth at that speed. why? engineering effort and manufacturing effort and design. point is, the engine needs to be agreeable in all parts of the rpm range, as the driver will use all parts of the rpm range at times.

Posted 02 November 2010 - 10:26 PM

its simple. drive a lacrosse and an old lesabre and its pretty effing easy to understand which engine is better. part of it is because the high feature v6 is a better design and part of that is because it runs smoother at higher rpms. it doesn't run out of breath and it doesn't sound like a vacuum cleaner.

part of the reason honda engines get accolades is because they are smooth from dead stop to redline, as people access power in all part of the rpm range in normal everyday driving.

Posted 02 November 2010 - 03:14 PM

because you need to accelerate and pass people, which requires accessing the upper reaches of the rpm band, more often than you think.

by your logic then, a 1 speed tranny is the schizzle.

any engine can be smooth at 3,000 rpm. if its smooth at 6500 rpm as well, you know the engineering is solid, not only the that, the vibration from the motor is less of an impact on the rest of the car. lastly, smoothness at high rpm only serves to underscore the quality of a product.

you can have your iron block dinosaurs like the 3800. There is a reason it was passed by by others LONG ago.


Let's see here... no, no, no, no, and no.

NO #1: The need for 6,500 rpm smoothness to pass people? Two words: Racing Diesel. If the torque comes on much stronger at a lower RPM, you engineer the gearbox accordingly.
NO #2: Any engine can be smooth at 3,000rpm? Two words: Quad-Four.
NO #3: Smooth at 6,500 RPM has nothing to do with "solid" engineering. It has everything to do with the size of the reciprocating mass. With a properly configured 6-speed automatic mated to both, I'd pit even the LT-1 against a Nissan VQ any day of the week for solidness.
NO #4: Why is 6,500 rpm the cut off for smoothness requirement? Run a Honda 2.4 up to 8,500 rpm and see how smooth it runs then. Running an engine outside of design parameters will get you unpredictable operation. The 3800 was never intended to be run up that high.
NO #5: The 3800 was done in by it's lack of VVT and it's packaging requirements being a 90 degree engine. The 3900 is a lot smoother than the 3800 was simply because of the cylinder bank angle change. Where GM let both engines down was pairing it with the 4-speed automatic. If either of those engines had a 6-speed auto that was able to keep it in it's designed RPM range, there wouldn't have been so much complaining about it. Don't start an idiotic horsepower per liter argument, it's already been a long day for me.

Review the complete topic (launches new window)