dwightlooi

Cadillac RTS - beat the Three

26 posts in this topic

The formula for beating the BMW 3-series may be real simple. Here goes:-

(1) RWD- Alpha platform (~108" wheelbase, ~3300 lbs, 5 seats, 4-doors, styled like the Torana; sized between the 3-series and the IS)

(2) Finish the Interior to the same standard as the CTS - not quite Audi, but good enough to combat BMW interiors

(3) Keep it 4-cylinders only -- a 300hp / 270 lb-ft version of the 2.0 liter LNF engine.

(4) Give it the excellent 6L50 tranny.

(5) Keep it around $32,000 to start.

That's it. You have just stuffed the 328 and matched the 335 in performance and beat them both in terms of not just price but also fuel economy with an EPA rating estimated to be around 22/28.

As far as the engine is concerned, the technology and techniques to make a 300hp 2-liter engine silky, civilized and quiet is already here. 40 hp more from the LNF seems like a lot considering the already overachieving nature of the 260hp 2 liter turbo. But it really isn't. Here's how...

The LNF currently makes 260 hp and 260 lb-ft. It is practically lag free and it is in many ways more civilized than the 3.6 V6. The turbo spools fast and early, but starts to run out of steam after about 5250 rpm when hp peaks. If we simply extended the 260 lb-ft torque plateau from 5250 rpm to 5850 rpm we get 289 hp. Bring it up to 270 lb-ft and you get 300hp. This is exactly the estimated net output at the SAME boost level if we substituted the KKK K04 turbo's compressor and turbine maps with that of a Garrett GT2560 turbo's. Yes, the wheels are bigger and inertial may be higher. But the ball bearing cartridge and the retention of the dual scroll housing will counteract the loss of responsiveness. About 270 lb-ft of torque should arrive at around 2000~2200 rpm regardless. If you really want to make this the best 4-potter turbo engine bar none (snuffing the Lancer Evo, Mazdaspeed and WRX STi's powerplants), the path is also paved and ready to tread. It's simple, you drastically reduce the pressurized volume which is just as responsible for turbo lag as the sizing of the turbo. The turbo has to bring the long hoses and the big front mounted intercooler to 18 psi before the engine sees 18 psi. That takes a little time. Get rid of it all and response becomes lightning sharp. GM already has the experience with air-water intercoolers -- having used them in the LSA and LS9 engines. With an air-water system you simply route the turbo's output through a short solid pipe to the intake side to feed an intake manifold with a small, integrated, air-to-water intercooler brick ala LSA. This minimizes the pressurized volume and maximizes engine response. The water lines and the size of the IC-radiator will not hamper engine response because they are not part of the pressurized air volume..

Edited by dwightlooi
0

Share this post


Link to post
Share on other sites
The formula for beating the BMW 3-series may be real simple. Here goes:-

(1) RWD- Alpha platform (~108" wheelbase, ~3300 lbs, 5 seats, 4-doors, styled like the Torana; sized between the 3-series and the IS)

(2) Finish the Interior to the same standard as the CTS - not quite Audi, but good enough to combat BMW interiors

(3) Keep it 4-cylinders only -- a 300hp / 270 lb-ft version of the 2.0 liter LNF engine.

(4) Give it the excellent 6L50 tranny.

(5) Keep it around $32,000 to start.

That's it. You have just stuffed the 328 and matched the 335 in performance and beat them both in terms of not just price but also fuel economy with an EPA rating estimated to be around 22/28.

As far as the engine is concerned, the technology and techniques to make a 300hp 2-liter engine silky, civilized and quiet is already here. 40 hp more from the LNF seems like a lot considering the already overachieving nature of the 260hp 2 liter turbo. But it really isn't. Here's how...

The LNF currently makes 260 hp and 260 lb-ft. It is practically lag free and it is in many ways more civilized than the 3.6 V6. The turbo spools fast and early, but starts to run out of steam after about 5250 rpm when hp peaks. If we simply extended the 260 lb-ft torque plateau from 5250 rpm to 5850 rpm we get 289 hp. Bring it up to 270 lb-ft and you get 300hp. This is exactly the estimated net output at the SAME boost level if we substituted the KKK K04 turbo's compressor and turbine maps with that of a Garrett GT2560 turbo's. Yes, the wheels are bigger and inertial may be higher. But the ball bearing cartridge and the retention of the dual scroll housing will counteract the loss of responsiveness. About 270 lb-ft of torque should arrive at around 2000~2200 rpm regardless. If you really want to make this the best 4-potter turbo engine bar none (snuffing the Lancer Evo, Mazdaspeed and WRX STi's powerplants), the path is also paved and ready to tread. It's simple, you drastically reduce the pressurized volume which is just as responsible for turbo lag as the sizing of the turbo. The turbo has to bring the long hoses and the big front mounted intercooler to 18 psi before the engine sees 18 psi. That takes a little time. Get rid of it all and response becomes lightning sharp. GM already has the experience with air-water intercoolers -- having used them in the LSA and LS9 engines. With an air-water system you simply route the turbo's output through a short solid pipe to the intake side to feed an intake manifold with a small, integrated, air-to-water intercooler brick ala LSA. This minimizes the pressurized volume and maximizes engine response. The water lines and the size of the IC-radiator will not hamper engine response because they are not part of the pressurized air volume..

What about other engines? Any diesel prospective? Given current constraints with the heads LNF can go upto 300 odd hp. More bolstered heads can have the engine breathing to about 400+ as is evident from the modified solstices and skies doing the tire burning on drag strips.

I think the weight should be no more than 3300 lb for a fully loaded version like the old E46 car. As for the V version the 3.6 DI turbo can do the job producing about 400-420 hp.

0

Share this post


Link to post
Share on other sites
What about other engines? Any diesel prospective? Given current constraints with the heads LNF can go upto 300 odd hp. More bolstered heads can have the engine breathing to about 400+ as is evident from the modified solstices and skies doing the tire burning on drag strips.

I think the weight should be no more than 3300 lb for a fully loaded version like the old E46 car. As for the V version the 3.6 DI turbo can do the job producing about 400-420 hp.

(1) A 2 liter DI turbodiesel with around 170hp can be used for the European fuel misers. But the idea is to build the car around one engine not 5 different ones.

(2) The idea is not to make as much power as possible from the 2.0 liter engine. The idea is to make the maximum amount of virtually lag free and immaculately civil horsepower -- a car competing in the luxury compact segment needs that more than it needs to shave 0.5 seconds off its quarter mile time. They have already done this at 260hp, now do the same at 300.

(3) ~3300 pounds is doable for a car this size with today's crash safety, chassis rigidity and interior furnishing expectations.

(4) For a RTS-V you can indeed stuff a 3.6 DI V6 Turbo in there. But 400~420hp is a bit modest. With two GT2259 class turbos and a relatively conservative 14.7 psi the output should be pegged at the limit of the 6L80 transmission say around 468hp @ 5850 / 423 lb-ft @ 1800-5800. We are talking about the same amount of specific power output as the current 260 hp LNF with less specific torque output. Again, using an air-to-water IC we can eliminate the large amounts of pressurized volume in the typical dual intercoolers and their associated plumbing.

0

Share this post


Link to post
Share on other sites

As much as people make fun of Tata they did one great engineering. I.e. when they got their first small car Indica, they based it on one block a 4-cyl 1.4L which had same bores and strokes for diesel as well as gas. The advantage was the block got designed for higher strengths and more stress conditions, they did not spend too much on engineering the engines.

I think the 2.0L can definitely use the same technique to give a NA, Turbo and a Diesel (like the one they showed in Chevy Orlando). But given the necessity of people's wants the car may need more engines.

I agree the 3.6 will be close to 460 hp if plunked to its full capacity. I personally do not think this car needs a V-8.

0

Share this post


Link to post
Share on other sites

We definitely would need a V version of the RTS. That would be awesome.

0

Share this post


Link to post
Share on other sites

This is an excellent concept, the sooner GM can bring something like this into production the sooner competition butt-kicking can commence... :)

0

Share this post


Link to post
Share on other sites

RTS? When did this name come up?

Also, won't it be strange that all variants of the CTS (save for the V) can run on regular, but the RTS will be premium-recommended?

Otherwise, it's cool with me.

I agree the 3.6 will be close to 460 hp if plunked to its full capacity. I personally do not think this car needs a V-8.

Force-fed 6 making 460 horses. Now we're getting into Porsche territory. :)

0

Share this post


Link to post
Share on other sites
The formula for beating the BMW 3-series may be real simple. Here goes:-

(1) RWD- Alpha platform (~108" wheelbase, ~3300 lbs, 5 seats, 4-doors, styled like the Torana; sized between the 3-series and the IS)

(2) Finish the Interior to the same standard as the CTS - not quite Audi, but good enough to combat BMW interiors

(3) Keep it 4-cylinders only -- a 300hp / 270 lb-ft version of the 2.0 liter LNF engine.

(4) Give it the excellent 6L50 tranny.

(5) Keep it around $32,000 to start.

1. Can GM make a car platform that is only 3300 pounds? Most of their stuff is heavier than class average

2. They have to compete against the A4 also, they better make the interior better than Audi and better than BMW

3. The 3-series has 6 cylinders (perhaps the best 6-cylinder on the planet) and a V8, Cadillac better have the same

4. Agreed, but they need a heavy duty version for the V-series

5. Agreed, and wouldn't mind seeing it start at $34,000

And there will be an all new 3-series when this car comes out, so Cadillac better not just build something as good as the current A4 or 3-series, they better do better. The 3-series has been king for 25 years, for Cadillac to beat it on the first try is a near impossible task, unfortunately, it is what they have to do if they want to stay in business.

0

Share this post


Link to post
Share on other sites
I agree the 3.6 will be close to 460 hp if plunked to its full capacity. I personally do not think this car needs a V-8.

M3 has a V8

C63 has a V8

RS4 has a V8

IS-F has a V8

Why does this car not need a V8? The V-series needs at least a 7-speed transmission, the IS-F has 8-speed. And they already sell that, Cadillac is bringing out a similar car in 2012, that is 4-5 years behind the curve.

0

Share this post


Link to post
Share on other sites
M3 has a V8

C63 has a V8

RS4 has a V8

IS-F has a V8

Why does this car not need a V8? The V-series needs at least a 7-speed transmission, the IS-F has 8-speed. And they already sell that, Cadillac is bringing out a similar car in 2012, that is 4-5 years behind the curve.

First you say that they need to make the car lighter than 3300, then you say that they need a V8. Keep in mind that EVERY car that you listed up there is 3600+ lbs.

Hard to contradict yourself that much, but you find a way every time, it seems...

How about you complain that, out of all the high-powered enthusiast-oriented small luxury sedans, the IS-F and C63 don't offer a manual? Or the C63 driver's seat only moves 6 ways? Or that the RS4 is (was) on a FWD platform? Or the M3 has iDrive... nuff said?

Just about every post you make is out to point out the deficiencies of a GM product (and this one doesn't even exist yet!) while you make it seem like Audi, BMW, MB, and Lexus have rose-smelling flatulence. And you wonder why so very few people take your opinions seriously...

0

Share this post


Link to post
Share on other sites

I didn't say it had to be 3300 pounds, especially not in V8 form, that isn't happening. I just questioned if even the base 4-cylinder turbo would weigh around 3300 pounds, because GM cars are often heavier than class average, and 3300 pounds would put it on the light side of the class.

Of course all those cars have flaws, especially the non-sporty Lexus and the cheap interior Mercedes, although they still have good reputations. The new Audis seem pretty good. I don't like iDrive and am not a fan of BMW styling, but their brakes, steering and suspension are excellent and can make you forget how dumb iDrive is rather quickly.

0

Share this post


Link to post
Share on other sites

Like this...

2011 Cadilac RTS

Vehicle Type: Compact Sedan / Coupe

Base Price: $32,000 (Base); $45,000 (RTS-V)

Standard: Power Windows, seats, locks; remote locking, cruise control, tilting/telescoping steering wheel, auto-dimming side and rear view mirrors, Piano Black trim, leather upholstery, BOSE 9-speaker sound system, HID headlights, On-Star, tire pressure sensors, variable assist power steering

Options: Navigation, Bluetooth phone interface, Rear Parking sensors and camera, Rain sensing wipers (Luxury Collection); Sapele Wood Trim, Panoramic Moonroof (Elegance Collection); Suede Leather inserts, 18” Forged Aluminum wheels, Cross-Drilled brake rotors, FV5 sports suspension package, Helical Limited Slip Differential (Performance Collection); 3.6 liter twin-turbo engine, 19” forged alloy wheels, 6-piston Brembo front calipers, 4-piston Brembo rear calipers (RTS-V Edition); 6-speed manual transmission (Manual Edition)

Curb Weight: 3335 lbs (Base); 3595 lbs (RTS-V)

Wt. Distribution: Front:51%; Rear: 49% (base); Front: 53%; Rear: 47% (RTS-V)

Wheel base: 108”

Engine: Turbocharged and intercooled 2.0 liter Inline-4, aluminum block and heads (Base)

Turbocharger(s): 1 x Honeywell-Garrett GT2560RSD, ball-bearing/dual scroll

Bore x Stroke: 86 x 86 mm

Displacement: 1998 cc

Compression ratio: 9.2:1

Power (SAE net): 300 bhp @ 6000 rpm

Torque (SAE net): 270 lb-ft @ 2200~5800 rpm

Redline / Rev limiter: 6000 rpm / 6400 rpm

Fuel Type: Premium Unleaded (91 octane)

Turbocharged and intercooled 3.6 liter V-4, aluminum block and heads (RTS-V)

Turbocharger(s): 2 x Honeywell-Garrett GT2252R, ball-bearing/single scroll

Bore x Stroke: 94 x 85.6 mm

Displacement: 3564 cc

Compression ratio: 9.7:1

Power (SAE net): 468 bhp @ 5850 rpm

Torque (SAE net): 423 lb-ft @ 2000~5800 rpm

Redline / Rev limiter: 6000 rpm / 6400 rpm

Fuel Type: Premium Unleaded (91 octane)

Transmission: Hydramatic 6L50 6-speed automatic (Base)

1st 4.06 2nd 2.37 3rd 1.55 4th 1.16 5th 0.85 6th 0.67 Rev -3.20

Ratio Spread: 6.06

Maximum engine hp rating: 315 bhp

Maximum Input Torque rating: 335 lb-ft

Maximum shift speed rating: 7000 rpm

Aisin AY6 6-speed manual (Base)

1st 4.155 2nd 2.513 3rd 1.691 4th 1.271 5th 1.000 6th 0.752 Rev -3.672

Ratio Spread: 5.525

Maximum engine hp rating: N/A

Maximum Input Torque rating: 273 lb-ft

Maximum shift speed rating: N/A

Hydramatic 6L80 6-speed automatic (RTS-V)

1st 4.03 2nd 2.36 3rd 1.53 4th 1.15 5th 0.85 6th 0.67 Rev -3.06

Ratio Spread: 6.01

Maximum engine hp rating: 469 bhp

Maximum Input Torque rating: 439 lb-ft

Maximum shift speed rating: 6500 rpm

Tremec TR6060 6-speed manual (RTS-V/Manual Edition)

1st 2.664 2nd 1.783 3rd 1.302 4th 1.000 5th 0.741 6th 0.502 Rev -2.903

Ratio Spread: 5.307

Maximum engine hp rating: N/A

Maximum Input Torque rating: 470 lb-ft

Maximum shift speed rating: N/A

Wheels & Tires: Front: 17 x 7.5” cast alloy; Rear 17 x 9” cast alloy (Base)

Front: 225/45 ZR17 Goodyear Eagle GT

Rear: 255/40 ZR17 Goodyear Eagle GT

Front: 18 x 8” cast alloy; Rear 18 x 9.5” cast alloy (Performance/Optional)

Front: 225/40 ZR18 Goodyear Eagle F1 Asymmetric

Rear: 265/35 ZR18 Goodyear Eagle F1 Asymmetric

Front: 19 x 8.5” forged alloy; Rear 19 x 10.5” forged alloy (RTS-V)

Front: 245/35 ZR19 Michelin Pilot Sport PS2

Rear: 295/30 ZR19 Michelin Pilot Sport PS2

Brakes: Front: 12.4 x 1.2” vented disc w/4-piston Brembo Fixed Calipers (Base)

Rear: 11.3 x 1.1” vented disc w/2-piston Fixed Calipers

Front: 14.6 x 1.3” slotted & vented disc w/6-piston Brembo Calipers (RTS-V)

Rear: 14.4 x 1.1” slotted & vented disc w/4-piston Brembo Calipers

Performance: 0-60 mph: 4.8 secs (Base/Automatic)

0-60 mph: 3.9 secs (RTS-V)

lnxgraphbd7.jpg

llxgraphhq3.jpg

Edited by dwightlooi
0

Share this post


Link to post
Share on other sites

You had me until the "four cylinder only" part.

Otherwise :yes:

0

Share this post


Link to post
Share on other sites

Dwight, this is impressive. Did you come up with this, or do you know a guy?

0

Share this post


Link to post
Share on other sites
You had me until the "four cylinder only" part.

Otherwise :yes:

The whole idea IS the four cylinder part. Everyone else has a six which comes with six cylinder mass, six cylinder economy and six cylinder commodifications. Instead, you drop in a turbo 4 that has just as much torque and power as a DI 3.6 V6, better economy and less weight up front. Traditionally, a turbo 4 making 300 horses (especially if its from 2 liters of swept volume) will be a frenetic, peaky, laggy and edgy powerplant. But we already know how to make it super civil and responsive, so we should capitalize on that and deliver a positive market differentiation.

Dwight, this is impressive. Did you come up with this, or do you know a guy?

It's all fictional, but fully plausible. Let's leave it at that.

0

Share this post


Link to post
Share on other sites
The whole idea IS the four cylinder part. Everyone else has a six which comes with six cylinder mass, six cylinder economy and six cylinder commodifications. Instead, you drop in a turbo 4 that has just as much torque and power as a DI 3.6 V6, better economy and less weight up front. Traditionally, a turbo 4 making 300 horses (especially if its from 2 liters of swept volume) will be a frenetic, peaky, laggy and edgy powerplant. But we already know how to make it super civil and responsive, so we should capitalize on that and deliver a positive market differentiation.

Sounds like Audi's plan... which doesn't seem half bad. On their entry/smaller cars, the base engine has always been a turbo-4.

They're using a turbo-4 for the TTS that makes the same power as the 3.2... with less weight. And I remember reading that the upcoming S4 will be using a blown 6 instead of the customary V8... a little less power but significantly less weight.

Really, I would even be cool if the entry Caddy's engine didn't make 300 HP... why not have two engine output levels? 250 and 300... and if they wanted to, premium-tune the NA HF3.6 for maybe 340 HP. Sort of an intermediate between the highest RTS and the RTS-V, which is something I feel the CTS could use in the future as well.

It's all fictional, but fully plausible. Let's leave it at that.

As you wish. :)

0

Share this post


Link to post
Share on other sites
You had me until the "four cylinder only" part.

Otherwise :yes:

68 if you want GM to survive then you have to accept the reality. I think what dwight is saying makes perfect sense. I had started a topic about how the future G6 should; be other than price, RTS (or whatever GM decides to name it) is the car GM needs but at a lesser money than what dwight is predicting to bring enthusiasts base. To go a step further it needs to be in coupe, convertible, wagon form too. Although I would not mind having a hatchback for other markets.

The whole idea IS the four cylinder part. Everyone else has a six which comes with six cylinder mass, six cylinder economy and six cylinder commodifications. Instead, you drop in a turbo 4 that has just as much torque and power as a DI 3.6 V6, better economy and less weight up front. Traditionally, a turbo 4 making 300 horses (especially if its from 2 liters of swept volume) will be a frenetic, peaky, laggy and edgy powerplant. But we already know how to make it super civil and responsive, so we should capitalize on that and deliver a positive market differentiation.

It's all fictional, but fully plausible. Let's leave it at that.

Just a question, how do you make those power-torque curves?

0

Share this post


Link to post
Share on other sites
Just a question, how do you make those power-torque curves?

(1) I drew them.

(2) They were drawn this way...

  • Determine the torque curve*
  • Plot the power curve based on the torque curve**

turbomapsuv2.jpg

k04-0025.jpg

KKK K04-0025 compressor map (LNF's current turbo)

* If you look at the torque curve of a modern turbocharged engine, they have a steep ramp up on the left, a plateau and a somewhat steep fall off on the right. Estimating the slope and the position of the left and right slope is possible if you have the compressor and turbine maps of the turbo. Basically, the surge front --the left hand boundary -- of the compressor map and to a lesser extent the efficiency of the turbine will tell you roughly how quickly the turbo will spool. The right hand boundary of the compressor map will tell you roughly how much air you can move before the compressor becomes so inefficient that you are heating the air up as much as you are compressing it -- which is when more boost does not yield more power, just an equal or more amount of heat. If you simply plot the torque curve based on the maps, you'll get a curve that looks like the fin of a shark. This is the torque curve you'll make by letting the turbo make as much boost as it can make at all points, assuming that your fuel is knock proof and the volumetric efficiency is 100%. That's rubbish of course. So, you temper the curve down by the estimated volumetric efficiency of the engine at each rpm point (the original 260hp curve of the LNF tells us a lot about the VE of the engine at all points up to 260hp flow rates really). You also then decide on how much torque you want to limit the engine to -- in the LNX's case it's 270 lb-ft. You chop the top of the curve off based on that and you have your plateau. You then go back and see if everything makes sense. The forward slope in this case is a little to the right and a little less steep -- OK, typical of a turbo with slightly larger wheels and more inertial. Maximum torque arrives about 200 rpms later, peaking a very modest 10 lb-ft higher. The reverse slope however shows the advantages of modern aerodynamics and frictional benefits of the ball bearing cartridge of a turbocharger like the GT25R -- you don't fall off the map for another 700 rpms! Stretching the plateau out to 5900 rpm vs 5200 gets you the horsepower increase.

** The power curve is plotted simply as hp = torque x rpm x 5252. Not much to explain here, it's the definition of "horsepower".

Edited by dwightlooi
0

Share this post


Link to post
Share on other sites
You had me until the "four cylinder only" part.

Otherwise :yes:

+1

yes a 4-cylinder only Cadillac would suck butt

0

Share this post


Link to post
Share on other sites
+1

yes a 4-cylinder only Cadillac would suck butt

Care to share "why"?

Why does a 4-cylinder 300 hp engine that is smoother, lighter, more economical and has more torque down low than a 3.6 liter six suck? In fact, that is a 2.0 liter 4-pot mill with torque peaking at a lowly 2200 rpm, but which makes more power than the average Northstar V8. If you drive the 3.6 DOHC V6 in the Malibu and the 2.0 DI Turbo in the Solstice, the later comes off as smoother, torqueier, more "alive" and in general a tad more refined.

Is it image? Well, the Audi A4 2.0T and the TT hasn't hurt the Audi image. So, again... why do you think it'll suck butt?

0

Share this post


Link to post
Share on other sites

4 cylinders aren't more refined than 6, my mom has an A4 with the award winning TFSI whatever it is engine, and I don't know how it won a Ward's 10 Best Engine award because it is unrefined as can be, the same held true with her Saab. There is great punch from the turbos and they deliver torque, but not the refinement end of it. A base model turbo 4 is fine, but there has to be a V6 option (or better yet inline 6) and DOHC V8 for the V-series.

Of course none of this speculation matters though because GM is too broke to build the car and just cut $1.5 billion in development spending, so the budget for a new Cadillac is probably out the window and the STS and DTS will linger on until 2013 and Cadillac's image will be dragged through the gutter again like it was in the mid 80s and late 90s.

0

Share this post


Link to post
Share on other sites
4 cylinders aren't more refined than 6, my mom has an A4 with the award winning TFSI whatever it is engine, and I don't know how it won a Ward's 10 Best Engine award because it is unrefined as can be, the same held true with her Saab. There is great punch from the turbos and they deliver torque, but not the refinement end of it. A base model turbo 4 is fine, but there has to be a V6 option (or better yet inline 6) and DOHC V8 for the V-series.

Of course none of this speculation matters though because GM is too broke to build the car and just cut $1.5 billion in development spending, so the budget for a new Cadillac is probably out the window and the STS and DTS will linger on until 2013 and Cadillac's image will be dragged through the gutter again like it was in the mid 80s and late 90s.

That is not my impression when I drove the 2.0 LNF and the 3.6 LY7. The LNF is smooth and silky from idle to the redline (~6200). The 3.6 starts making mid frequency groans at about 5000 rpm and didn't sound like fine machinery for the last 1000 rpm of its rev range. At the low and mid rev ranges there is no difference in refinement, but the 2.0 LNF is more responsive and more alive when prodded. There are many instances where V6es are uninspiringly whereas 4-potters are superbly refined. The Mitsubishi 4G63 in the older Evos and the Eclipses of yore is wonderfully refined. The LNF is wonderfully refined. The VW/AUdi 2.0T is fantastic too. The Ford Duratec 2.5 and 3.0s, the recent GM 3.5 V6 and the Mitsubishi 3.8 V6 are all pretty rough and gritty. Worse than all of the aforementioned fours and jeez worse than even the big displacement fours like the Ford/Mazda 2.3, the GM 2.4, Honda 2.4 and the Toyota 2.4. Of course, there are horrible fours as well... the 2.4 SR24DE in the old 240SXes and Altimas come to mind as well as the 2.5 Iron Duke I4 in the Fiero and other GMs of the 80s.

There are three factors which contribute to refinement of an engine (or the lack thereof).

(1) Natural Vibrations

(2) Power pulse density

(3) Block stiffness

An I4 is 1st order balanced, with up/down second order vibrations. These can be mostly canceled out by a pair of counter rotating balance shafts turning at twice the crank speed. The I4 has 2/3 the power pulse density of an 6-cylinder engine; the density at 3000 rpm is similar to that of a V6 at 2000 rpm for instance. Power pulse density related coarseness tends to be noticeable only at very low rpms, at even cruise speeds it disappears. Block stiffness limits the amount of flex in the engine block during operation. A stiff engine emits pleasing high frequency resonances (like a Ferrari or Porsche engine), a flexy block emits a low frequency sounds like a 90s 3800 V6.

A V6 in the 60 degree configuration as mild 1st order vibrations. They are typically left alone because its deemed acceptable and there is no room in the Vee for a balancer. A 90 degree config as significantly worse 1st order vibs, and most 90 degree sixes have a single balancer turning at crank speed. An I6 is naturally balanced. The six cylinder engine has an advantage in pulse density at low rpms. A stiff block however can be tougher to achieve in a V6 and especially an I6 than in an I4.

0

Share this post


Link to post
Share on other sites

One thing I love about this place is dwight's posts. I don't how he does it, but he explains everything so well that even a total r-tard like me can feel smrt. :breakdance:

I don't understand the animosity towards four-cylinders. As mentioned before, Audi's four's are just fine for what they are. Especially when fuel-economy is on a lot of people's minds, it'd be a no-brainer to not offer a four-banger in a Cadillac Alpha. If you can opt up to a six, then I don't see a problem at all.

0

Share this post


Link to post
Share on other sites
One thing I love about this place is dwight's posts. I don't how he does it, but he explains everything so well that even a total r-tard like me can feel smrt. :breakdance:

I don't understand the animosity towards four-cylinders. As mentioned before, Audi's four's are just fine for what they are. Especially when fuel-economy is on a lot of people's minds, it'd be a no-brainer to not offer a four-banger in a Cadillac Alpha. If you can opt up to a six, then I don't see a problem at all.

I agree.

Remember when, just a few years ago, in North America there were fours in the 3-Series and C-Class?

I think this is a good move by Cadillac (if it indeed gets done) to find a medium between good power and respectable fuel economy. Forget what the cylinder snobs say... like you said, it's not like there's going to be just one engine option.

(BTW, I'm waiting for smk's response to Dwight... if he can formulate one.)

0

Share this post


Link to post
Share on other sites
One thing I love about this place is dwight's posts. I don't how he does it, but he explains everything so well that even a total r-tard like me can feel smrt. :breakdance:

I don't understand the animosity towards four-cylinders. As mentioned before, Audi's four's are just fine for what they are. Especially when fuel-economy is on a lot of people's minds, it'd be a no-brainer to not offer a four-banger in a Cadillac Alpha. If you can opt up to a six, then I don't see a problem at all.

People who really know about cars aren't afraid of 4 cylinders, but many people remember the hoary 4s of the '80s - how gutless they were and unreliable, which makes them naturally wary of buying a new car, especially a luxury car, with a 4.

I think it is unfortunate that over the past decade or so technology has gotten sidelined into a new displacement war because otherwise the R&D money could have been spent on 2.0 engines that get 40 mpg and 200+ horsepower with torque numbers that can move a 3,500 lb car with fun and reliability. This is the new reality and now car makers are going to have to play catch up to erase the last 10-15 years.

0

Share this post


Link to post
Share on other sites

Your content will need to be approved by a moderator

Guest
You are commenting as a guest. If you have an account, please sign in.
Reply to this topic...

×   You have pasted content with formatting.   Remove formatting

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor