1 Bad Mirada

they dont just make the parts and HOPE that they fit...they have to rely on either the companies ability to purchase a vehicle for testing, or in the case of some companies, they rely on regular people who want to get a free part for letting the company in question thrash the car for a while.

either way, would you buy a part, or even consider it, from a company who has guaranteed NO R&D on the vehicle? i sure wouldnt, who knows if it will fit, or if its better than the OEM setup. id bet that they have that listed just so that people will visit their site, as search engines hunt for things like that, and having it now will put them above other companies once the car is released.

Blackflag

Welcome to aftermarket parts.

davecpa

Since mine is going to be a daily driver the 6.1L is more than sufficient. I dont live close enough to a gas station to have anything bigger. [sm=gears.gif]

1 Bad Mirada

what do you mean welcome to aftermarket parts? i dont own a single vehicle that doesnt have aftermarket parts, and i dont buy parts that obviously have no R&D behind performance claims or fitment...especially exhaust...then again, i bent most of my systems myself.

RLSH700

Blackflag, 4 valves per cylinder does not automatically equal better fuel mileage. GM's most fuel efficient V8 engines are the pushrod line instead of their overhead cam models (and I'm not taking into account the AFM versions). I'll give you a few real life examples. GM took their 60 degree V6 engine and added a 4 valve DOHC head to their engine and increased the displacement to 3.4 liters and the fuel mileage dropped from 29 mpg with the 3.1 liter to 26 mpg. Granted the displacement grew and they gave it a slightly shorter 3.43 over the standard 3.33 in the models it was equipped with but later a OHV version of this engine line was offered in the 2000-2005 Impala and it was rated at 32 mpg with gearing in the 3.07-3.05 range.

When they offered the "Shortstar" (V6 Northstar 4 valve DOHC) as an "upgrade" from the 3800 series II in the Intrigue, the fuel mileage dropped from 30mpg to around 27-28 while offering similar gearing; meanwhile, the supercharged Grand Prix GTP offered shorter gearing with their supercharged 3800 pushrod and got equal to 1 mpg better on the highway.

Most recently, the 3.5L "High Value" (2 valve OHV) powered Pontiac G6 only featured a 4-speed automatic and got between 30-32 miles per gallon, then they offered the 3.6L "High Feature" (4 valve DOHC) version in the GTP and now the GXP with a six speed and despite similar gearing the best the combo could muster is 28 mpg.

The same thing is true with Chrysler, the best fuel mileage the 3.5L (4 valve SOHC) received in the LH cars was 26-27; meanwhile, the 3.3L normally got 28 (2 valve OHV).

Therefore, there are no guarantees that it will improve the mileage. I would tend to believe that it would do the opposite.

Jeremiah 29:11

To insinuate that aftermarket parts do not have any R&D is a little callow.

1 Bad Mirada

ive dealt with AEM on MANY occassions to help them find people in certain areas willing to lend their vehicle for fitment and performance testing, and in return the person gets a free 300+ dollar part...also, some people ive set up have gotten much more expensive exhaust systems, turbo setups, etc.

Blackflag

Well, you can't compare across vehicle lines because there' are too many variables. And you can't fairly compare two different engine families, because there are too many differences between the two. (For example, your Chrysler comparison compares a 3.3l to a 3.5l, which accounts for the fuel economy difference in itself.)

But on a single engine family, multiple valves will generally give better fuel economy because of the more efficient cylinder filling. Volumetric efficiency increases over two valves, which virtually dictates better fuel economy. However, nothing is absolute. (You may put on 4-valve heads with a cam that is far less fuel efficient and lose the benefit.) But it's pretty well understood that four valves = better FE. A good compromise between performance, FE, and emissions is the three valve arrangement, which MB and Ford have kind of settled on. Two valve is a little dated/cheap in my opinion.

lear4406

I think that the 4 valve and 3 valve are for performance. I draw my conclusion from the fact that I have a Stealth 3.0 4 valve engine and my son has a 3.0 2 valve Stealth. I make more power but he gets better gas mileage. Same block, different heads. More air fuel with the 4 valves. I mean it just breaths. But I'm no engineer, just a self owned driveway technition. But I do have 30 years expierence. And I did stay at a Holiday Inn Express one time.

RLSH700

Okay now I think we have found the route to your problem with the Hemi. You don't like it because its a 2 valve per cylinder pushrod engine. Funny how when you first joined the site, you were bashing the Hemi saying it wasn't a true Hemi, then you want to make it even less like a Hemi by going 4 valves per cylinder. Amusing but not quite as amusing as your response.

A little background info for you Blackflag. The 3.5L is based off of the 3.3L. They are from the same block. Essentially, you have just argued that the Chrysler 3.5L is from a completely different family than the 3.3L and that explains why it gets lower fuel mileage, so then if a 7.0L Hemi would be produced with 4 valves per cylinder and OHC with the 5.7L/6.1L/6.4L block, would it be become a whole new family? No, its called they switched the engine from a pushrod design to an overhead cam 4 valve head which is all that happened to the 3.3L base when they made the 3.5L. The 3.5L had the same axle-ratio (3.66), same transmission (A606/42LE), same platform (LH), same vehicles, higher compression ratio (depending on the year 10.4-9.4 vs. 8.9 to 1) which improves fuel economy mind you, etc. as the 3.3L, so explain all the other mystery variable that have not been included. If your argument was sound, it would at least be able to maintain the same fuel mileage despite all of this.

Also the same thing is true about the 3.4L DOHC engine, it was based off of the GM 2.8L/3.1L/3.4L block, they just made an OHC out of a pushrod is all that happened, and that is exactly what would happen here if they made a 4 valve DOHC Hemi. Same procedure

How about more examples about how your argument is wrong? The early Saturns had the 1.9L engine in either 2 valve SOHC or 4 valve DOHC. A SC1 2 valve SOHC model would get 40 mpg when equipped with the 5-speed manual with an axle-ratio of 4.06; meanwhile, when it offered the 4 valve DOHC which according to your argument should improve fuel economy only got 37 mpg when equipped again with the 5-speed manual transmission and the same axle-ratio of 4.06. How about more examples, the GM 2.3L Quad-Four when 2 valve SOHC 5-speed manual 2.84 axle ratio equipped got around 33 mpg in the earily 90s Grand Am; however, the 4 valve DOHC version only got 30 mpg with the 5-speed manual and 2.84 axle ratio combo. Two examples of a three mpg drop with the same sized engine, both originally OHC designs, same gearing, same transmissions, same car. etc. The problem is there so far no proof of the opposite happening anywhere.

Each of the other examples demonstrated in my previous post showed how even though the 4 valve DOHC engine had the gearing advantage, new technology, same platforms, etc. each time it got lower fuel mileage. It appears your theory is no longer a theory because it has been proven to be incorrect over and over again.

Out of all of the different car companies in the world, the last two I would ever use as a benchmarker or one t