C8 Corvette

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Maritimer
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Re: C8 Corvette

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Dodge, Ford, Toyota, Cummins, and Bentley all produce pushrod engines, its not only GM by any means.

Jolle
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Re: C8 Corvette

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Maritimer wrote:
Wed Jul 24, 2019 11:09 am
Dodge, Ford, Toyota, Cummins, and Bentley all produce pushrod engines, its not only GM by any means.
Ford is making one pushrod engine, a 7.3 for their heavy duty trucks, which lives outside emission regulations (because it's a heavy duty truck). All their performance cars are DOHC.

Toyota isn't making any OHV engines anymore, their last one was a sixties design that was phased out in the nineties for DOHC versions.

FiatChrysler is making the HEMI of course, for the same reason Chevy is still using the LS/LT series, for offering relative cheap bang for the buck. Any serious sports car from the company has DOHC.

Maritimer
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Re: C8 Corvette

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The last serious sportscar Chrystler made had a pushrod engine. As for Ford, the Powerstroke V8s are all pushrod and very much subject to emissions regulation. The current iteration also has four valves per cylinder and reverse flow heads.

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humble sabot
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Re: C8 Corvette

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Maritimer wrote:
Wed Jul 24, 2019 11:35 am
The last serious sportscar Chrystler made had a pushrod engine. As for Ford, the Powerstroke V8s are all pushrod and very much subject to emissions regulation. The current iteration also has four valves per cylinder and reverse flow heads.
Trucks, (no cars come with "powerstroke") because 'murica, are not subject to "real" emissions regs. Whether that has any bearing on the rest of your points is irrelevant. Body on frame vehicles are still given a handicap under the rubric that they are necessarily tools of trade and should therefore ______ (choose your own supply-side-economics lie). Meanwhile Ford Expedition: Exists, Chevrolet Suburban: Exists.
Does 'reverse flow heads' just mean hot-V?
the four immutable forces:
static balance
dynamic balance
static imbalance
dynamic imbalance

Maritimer
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Re: C8 Corvette

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humble sabot wrote:
Wed Jul 24, 2019 6:22 pm
Maritimer wrote:
Wed Jul 24, 2019 11:35 am
The last serious sportscar Chrystler made had a pushrod engine. As for Ford, the Powerstroke V8s are all pushrod and very much subject to emissions regulation. The current iteration also has four valves per cylinder and reverse flow heads.
Trucks, (no cars come with "powerstroke") because 'murica, are not subject to "real" emissions regs. Whether that has any bearing on the rest of your points is irrelevant. Body on frame vehicles are still given a handicap under the rubric that they are necessarily tools of trade and should therefore ______ (choose your own supply-side-economics lie). Meanwhile Ford Expedition: Exists, Chevrolet Suburban: Exists.
Does 'reverse flow heads' just mean hot-V?
Reverse flow heads have the intake and exhaust ports on the same side as opposed to cross flow which have opposing ports.

roon
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Re: C8 Corvette

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humble sabot wrote:
Wed Jul 24, 2019 6:22 pm
Body on frame vehicles are still given a handicap
There is no stipulation for vehicle construction method.

Jolle wrote:
Wed Jul 24, 2019 11:31 am
one pushrod engine, a 7.3 for their heavy duty trucks, which lives outside emission regulations (because it's a heavy duty truck).
That engine will go in light duty trucks beholden to EPA regulation. Light duty trucks must comply with the same ruleset as passenger vehicles.

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humble sabot
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Re: C8 Corvette

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It was commonly known that there was a kind of truck clause when emissions targets were set a few years ago that the target for a truck would be far less stringent, and in the construction of the regulation 'truck' was partially defined by being body on frame, as that applies primarily to industry vehicles at this point. Though, it still left the door open to sell passenger vehicles (Suburban and Expedition that i mentioned) to that lower target because they could be registered with the EPA as "trucks".

The rule set. is just that, a set. It's gradient primarily based on weight class. A 'compact' is expected therefore to be more efficient than a 'full size'
the four immutable forces:
static balance
dynamic balance
static imbalance
dynamic imbalance

NL_Fer
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Re: C8 Corvette

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The 3.0 turbo engines are better in CO2 emission. At least if they test with European (extreme slow & non realistic) driving cycles. WLTP is better, but still fake.

Turbo engines are very good to lower CO2 emission, when testing with those cycles.

roon
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Re: C8 Corvette

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humble sabot wrote:
Wed Jul 24, 2019 7:11 pm
...
Weight class based emissions were phased out in Tier II, 10-15 years ago.
Last edited by roon on Wed Jul 24, 2019 10:17 pm, edited 1 time in total.

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strad
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Re: C8 Corvette

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Toyota isn't making any OHV engines anymore
Seriously?? You mean they went back to flat heads?
Overhead cam (OHC) engines are overhead valve (OHV) engines. OHV means the valves are in the heads.
OHC only refers to how the valves are actuated.
To achieve anything, you must be prepared to dabble on the boundary of disaster.”
Sir Stirling Moss

Jolle
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Re: C8 Corvette

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strad wrote:
Wed Jul 24, 2019 7:52 pm
Toyota isn't making any OHV engines anymore
Seriously?? You mean they went back to flat heads?
Overhead cam (OHC) engines are overhead valve (OHV) engines. OHV means the valves are in the heads.
OHC only refers to how the valves are actuated.
ok ok, Toyota isn't making pushrod engines anymore (expect for nascar, where they are mandatory)

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strad
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Re: C8 Corvette

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I knew you knew,,, I just couldn't resist. :lol:
To achieve anything, you must be prepared to dabble on the boundary of disaster.”
Sir Stirling Moss

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humble sabot
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Re: C8 Corvette

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a little more on topic: https://www.topspeed.com/cars/here-s-wh ... 86096.html

The gallery is pretty interesting, particularly the cross section of the heads, as it happens.
the four immutable forces:
static balance
dynamic balance
static imbalance
dynamic imbalance

SmallSoldier
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Re: C8 Corvette

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humble sabot wrote:a little more on topic: https://www.topspeed.com/cars/here-s-wh ... 86096.html

The gallery is pretty interesting, particularly the cross section of the heads, as it happens.
Thanks! That was a good read


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heretolearn
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Re: C8 Corvette

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Long time lurker, first time poster. I enjoy reading these forums because I am far from being an engineer (so please go easy on me). I'd like to contribute an update and follow it with a couple questions. According to multiple articles, including the one here:
https://www.hagerty.com/articles-videos ... -plane-v-8
the racecar, which must be based on at least 300 produced street cars, will have a DOHC flatplane crank V8 of 5.5L capacity. Thus, unless there is some loophole or waiver, at least some of the new cars will have a similar powertrain. Exhaust scavenging has been commonly mentioned as a reason for the switch away from a pushrod unit. This brings me to my questions.

The benefits of the pushrod seem to be many ( 1) weight 2) low COG 3) low/midrange torque 4) efficiency 5) cost 6) durability). Why would GM move away from a technology in their race car and some of their street cars if it seems to have so many benefits? Is it a combination of the importance of exhaust scavenging combined with the 5.5L displacement limit? If so, then why couldn't GM seek a waiver to run more than 5.5L of displacement in the race car as other manufacturers have done?

My other question is far more open ended. If one were to create a modern "unlimited" series a-la Can Am, would pushrods be the motor of choice due to packaging and the fact that for every additional bit of displacement one adds to an OHC engine, the additional weight and COG would be negate the additional horsepower created via better breathing? For the moderators, I would be happy to take this topic to a different forum if it is required. Thank you in advance!