skank

Listening to Autoline the other night it was mentioned that Cosworth has now set up in Michigan. Apparently they are making the heads to a 4.2 and 5.5 TT V8's. This is going on the List.

https://www.forbes.com/sites/samabue.../#136f129b3d8d

JerriVette

skank

Possible electronically actuated manual transmission for mid engine Zora. See new article below. This goes on the list.
https://jalopnik.com/gm-s-new-patent...1829177464/amp

Racer X

Could someone explain the physics? Seems to me limiting factors are material strengths and maximum piston speed at RPM limit. Piston speed gets limited by RPM and stroke lengths. Rod , crank, bearing materials limit the mass of piston at a given RPM. So make the bores big and the pistons lightweight.

Could someone explain the fascination with high rpm for a street car that does not have rule limited displacement? Higher rpm means higher stresses, and lower fuel economy. When you can get the same power at lower rpm and get better mileage, and the engine lasts longer, why the cry for unnecessarily high RPM? I get it for racing where rules limit displacement. Yes, sometimes they sound cooler. However, having competed in a open exhaust RX-7 where the noise was piercing even with ear plugs and a helmet, sometimes it is not enjoyable.

skank

Potential Hybrid Drivetrain technology as indicated in this article by Road & Track magazine on GM patent. Thread by Darion.

https://www.roadandtrack.com/new-car...o-c8-corvette/

Shaka

How many track days can you have in a F458 or a 488 before the explosion? A flat crank in a V8 is for lots of HP from a small displacement engine. 5 liters is past the limit. It is designed for high RPM. It has an over square bore/stroke ratio and vibrates like hell. It will have lower crank stress due to the lower peak piston acceleration for the same engine speed and will have has better pumping efficiency because of bigger valve/bores ratio at high RPM. Defeated by a turbo charger. Increased piston and head surface area and high bore/stroke ratios cause increase in heat loss and poor thermal efficiency. (Gas guzzler tax)
The large size/width of the combustion chamber at ignition can cause increased inhomogeneity in the air/fuel mixture during combustion, resulting in higher emissions. Because these characteristics favor higher engine speeds, oversquare engines are tuned to develop peak torque at a relatively high speed, which again contradict turbo duties.
The reduced stroke length allows for a shorter cylinder and a shorter connecting rod, generally making oversquare engines less tall but wider than undersquare engines. The F488 is a magnificent car but it ain't cheap and you gotta stop for gas often which is bad for track days for that reason. Placing turbos on a engine layout designed for high RPMs is really stupid. High manifold pressure and Low RPMs in a a flat crank V8 causes high piston side loads. Add a turbo charger and you asking for self destruction.
There are some here who call for it in the C8. Chevy LS engines are lighter with low Cg and two valves, one cam and a very short timing chain. You don't need high RPM with two valves and you don't need 4 valves with a super/turbo charger. The LS engine costs $600 less to make than the Caddy DOHC engine. The Caddy engine is much heavier and uses more material. Actually, DOHC means direct overhead cam and not dual. That means the the tappet is in between the cam and the valve.
I want a pushrod, port injected, N/A Chevy V8 in my C8 with a manual 6 speed Xaxle. Either that or I keep my C6Z for another 10 years

MitchAlsup

Pistons go up and down, this causes the wrist pin in the con rod to pull on the piston at TDC when the intake and exhaust valves are open. As only as the con rod can support this inertia, and the crankshaft can support the con rod forces, and the main bearings can support the load, the engine will not come apart.

A cross plane crank always has one piston going down, one piston coming up, and 2 pistons at mid stroke per bank, and both banks are the same. THis is the most balanced in a mechanical sense of things. In each bank there is always some piston causing the opposite set of forces to any given piston.

A flat plane crank is essentially two 4-cylinder engines sharing a common crank shaft, and has very similar vibration characteristics. There are either 2 pistons coming up and 2 pistons going down or 4 pistons in mid stroke per bank. One can balance the FPC for the coming up and going down part, or one can balance the FPC for the mid-stroke part, but you cannot balance the thing for both (like one can with a cross plane crank).

The vibrational forces in a FPC tend to make the crankshaft into a bit of a helix shape, and when supported by the bearings, the block must be able to absorb these rapid high force events thousands of time per minute. The vibrations basically shake the block to bits, and any casting imperfection will eventually become a failure point. Aluminum castings will have imperfections, and white metals do not have a safe limit for these kinds of repetitive forces being applied.

High RPM engines simply sound fabulous. Go listen to a 1 litre BMW HP4 motorcycle engine, 999cc 215 HP @ 14,500 RPMs.
High RPM engines with flat plane cranks have a sound akin to a V12 purr rather than off kiltered lub dub sound from a cross plane crank.

Now one can fit 180º headers to a CPC and get most of the sound of a FPC at some cost in high RPM power due to the length of the shortest pipes which cross from bank to bank. Hot-V gas flow helps a lot in enabling 180º headers. Routing 180º headers out of the engine bay of a FE car is a nightmare.

One cannot get the intake purr from a cross plane crank that one can get from the FPC, and generally all 8 cylinders draw from the same air box, whereas the FPC engines will have an air box for each bank.

Whether any of this is "of value" to the customer depends on the customer.

Racer X

Thanks, Shaka and Mitch. You have confirmed I had a pretty good understanding of the issues. You have both been quite elegant. I am not a fan of high RPM for street use where displacement is constricted by regulation (like racing, or laws). I get the sound factor and have heard Formula 1 cars at 18,000 rpm scream. I am not a fan of superchargers, except in drag racing. There they reign supreme due to no lag. Since they only make about 600 rotations going down the track, even a few rotations of lag can do you in. For the street I think turbos are better due to far less loss of HP to drive the compression. There is some loss due to exhaust restriction but it pales by comparison to a supercharger. Sure there is some lag but on a road course it can usually be compensated for. I raced in amateur classes a suck through carbureted turbo small block The lag was significant and the surge was pronounce, but I got to where I could predict it.

Street cars should be about the most power, with the best economy, and least wear in combination with cost control. In short a very high bang for the buck.

I see the flat plane high RPM more of a bragging rights thing. My preference is a results for the money thing. Corvettes have excelled at that. The different levels of models (Coupe, Z06, ZR1) just do that at different price points. I think they should maintain that. I would like to see less weight rather than more power. Say 20% less weight rather than 20% more power.

MitchAlsup

I have 5,000 track miles on my F355 motor and there has been no explosion or massive wear,...(along with 69,000 total miles.) Probably 45+/- track days.
Most of the track miles were spent going within 2 seconds of the class lap record at TWS, MSR-Bonney, MSR-Cresson. Class = (400 HP or less, street tires, 3200 pounds or more). Much of the time the summer temps were in the 103ºF range.

skank

Since GM has trademarked the ZORA name worldwide it"s logical that we will have both left and right hand drive. It's going on the list.

https://www.corvetteblogger.com/2018...cluding-china/

Shaka

Interesting. I love Ferraris. Italian cars are actually becoming reliable. See JD Power on Maseratis? Throughout the years, there have been one or two very dependable Italian cars. The Dino V6s are very strong engines especially with the American cams and gears and 50 thousand mile belts. Remember the Stratos? If the C8 is only 80% of what a 458 is, it will be a wonderful car. A C7 feel is a far cry from any ME V8 Ferrari. You never get that tight feel in a Vette. A 550 or 575 feels so much better than a C7 and they are old cars. Unless you drive a ME V8 Ferrari, even a 308, you won't know what I'm talking about. I'm a chassis guy. I spent over $30gs on my C6Z to make it feel Italian. A roll cage was the most help. It is the first thing you become aware of in a ME Ferrari is the soundness and integrity of the chassis in the B cars. It is really something to behold. Every Italian car is a blast to drive and you can't help singing one of Verdi's arias while driving them. 1000cc and 350 hp more in the 458 over the 355 changes dependability not to mention how much fuel it uses when driven hard. I would say that the 458 is the finest sports car ever made strictly as a driver's car. I don't play golf. The 488, 4.9 cc, takes sports cars to the stratosphere. The numbers are one thing, but how they are achieved is quite another. The C8 chassis may make the new car feel like a Ferrari but I seriously doubt it. Having said that, I would never be without a Vette.

skank

There is a viable potential of all wheel drive on the higher level models of the ME ZORA since GM has trademarked Sport Control AWD. Recently Bob Lutz as well as prior Corvette Chief Engineer Dave McClellan indicated that potential as well. This is going on the list.

Shaka

Very informative video and so was lutz's on Autoline. Watch them again.

sunsalem

Flat plane crank anyone?

skank

Elegant has given us a interesting article on the new ZF Electronic "Brake By Wire" system. It's going on the List Thread.
http://gmauthority.com/blog/2018/10/...#ixzz5UmiV1IWR

skank

I think the Vent material and color palette on the ZORA will be Matte black, Carbon Flash, Dark Grey, or body colored like the current vent ordering options of the C7 line up. We will also most likely have a higher quality Carbon Fiber option all the way up to specific right side or left side directional lay up and centerline book matched lay up where components are in the center position of the car. It only makes sense to have the same flexibility in material types and vent colors that we have now. The current ZR1 initiated the centerline book matched lay up option and it will be enhanced on the ZORA. This is going on the List.

bebezote

fantastic....very well describe... thank you!!

bebezote

headlines like this

New Tesla Roadster First Look: Zero to 60 in 1.9 Seconds, 250-MPH Top Speed, 620-Mile Range

The claimed quarter-mile time of 8.8 seconds

If this is 200-250k ... and can corner.. makes it very difficult to think about a corvette..

blipit_

Unless you plan on doing track days and your Telsa needs a full battery charge after only 1-2 session.

ojm

Who the hell will be able to service this pie in the sky technology? Certainly not the average car dealers or mechanic. A toy for the idle rich.