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Sedans Chevrolet Impala Chevrolet Impala 2006
3460 messages, Last post on Sep 05, 2009 at 6:21 AM
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| Correction on post #117....it should read Chevrolet has never made an DOHC engine... | |
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What about the DOHC 3.4 based on the Chevy 2.8/3.1? Believe this engine was in the W-Body Cutlass and Lumina Z34 in the early to mid-nineties. I agree you can't really count the ZR-1, due to it being a Lotus-design and the engines were built in-house (were built by a marine (boat) shop, correct?) And frasierdogg, you forgot to mention that you have to REV those DOHC to the high heavens to get that high-torque number, along with the horsepower. Whereas the ohv make torque at low-mid rpm, mostly building right off idle. I will agree that there are a few DOHCs that start making decent pulling power near-right off idle and have o.k. mid-range torque, but they are few and very far between. And who wants to buzz their engine to the high side 5-grand to reach that pulling power? You're points are o.k, but not really true in terms of NVH, smoothness, lighter (which I don't really see given the add weight of chains/belts, extra cams, gears, bigger heads...). Just because it's OHC doesn't automatically make an engine smooth and a NVH champ. And I won't mention the cost when you have to replace cams, possible stretching of the changes/belts, cost of changing the timing belts, damage if the belt/chain goes. It's almost like saying OHC is new, it MUST be better, when in fact it's as old as OHV, heck older than what's considered the "modern" OHV!! Just because it's cheap doesn't mean it's not as good as OHC. 3800 series II, gen III and IV small-blocks aren't bad.:> If the OHC is sooo good, how come it took Ford over ten years to boost the hp from 210 to 300 for the 4.6? 
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Replying to: jae5 (Jan 13, 2005 11:25 am) That is a really old stereotype. Yes, it may have been this way in the first days of DOHC, but in today's world, its more than 'few and far between' that DOHC engines have good low and midrange torque. Witness the Camry 3.3L: PEAK of 240lbs  3600 RPM. The Malibu 3.5 peaks but 400 Revs lower, and with 20 fewer pounds. Or, we can use a Honda as an example. The Acura TL 3.2L produces 90% of its torque peak of 238 foot pounds by 2500 RPM. That means 214 pounds are on tap at that point. Is that not good low-end grunt? ~alpha
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Replying to: frasierdog (Jan 13, 2005 8:23 am) First of all OHV engines are lighter than DOHC engines of comparable sizes. On top of that they have lower center of gravity, no timing chains and modern OHV engines are just as good on emissions. As old as OHVs are supposed to be I find it amazing that they can still get the same, or better, mileage as modern DOHC engines and also qualify as low emissions vehicles. When I first started coming to Edmunds people were saying that GM had to phase out OHV engines because they coundnt meet the upcoming emissions standards. That was about six years ago. Ford's new engine will not be out until calendar year 2006. By that time GM's 3.6 will in the Saturn Aura, Lacrosse and most likely the replacement for the Lesabre. |
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Replying to: alpha01 (Jan 13, 2005 12:13 pm) The response was to fraiserdog in that even though there are upsides to OHC layouts are there are downsides as well. And second, just because it's an OHC design, it doesn't make it automatically BETTER than OHV.
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Replying to: jae5 (Jan 14, 2005 5:35 am) Going with the same size displacement, the Nissan 3.5L and Toyota 3.5L also post impressive torque figures. Since the Nissan 3.5L is sold in the U.S. alone in over 500,000 cars and SUVs annually, thats not "few and far between". With regard to the Toyota, the peak of 260 is fairly high- at 4700 RPM, but the curve is said to be fairly even, so Id have a hard time thinking that that engine is not making the same 220 foot pounds at 3200 RPM as is the pushrod GM engine of the same displacement. And the DOHC engine won't be completely winded by 5000 RPM. Since we're talking about examples, can you cite an OHC design that posts low torque for its size? ~alpha
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Hey, anyone know the details on the 3500 VVT? According to the Chicago press release this engine has a 99x76 mm bore x stroke, so it's NOT the same as the non-VVT engine in the Malibu, which is 94x84 mm. The 3900-VVT is a bored version (99x84 mm) of the Malibu 3500, and it seems like they "de-stroked" the 3900 for the 3500-VVT. The Impala press releases suggests looking at the "powertrain" press release for more details - does anyone know where this is? Sorry if this has already been posted, but I don't have the fortitude to read through any more of those "OHV sucks" threads... |
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Replying to: stormdavy (Jan 12, 2005 2:59 pm) |
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| Quick, take a look at the ad banner on top of this page. That is a nice looking car. Why can't those boneheads from GM design something that looks great?!! | |
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Replying to: alpha01 (Jan 14, 2005 9:17 am) "Since the Nissan 3.5L is sold in the U.S. alone in over 500,000 cars and SUVs annually, thats not "few and far between"." Its over 300K, I believe. Sorry! |
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