Why is redline the same on ZR1 - no AFM?
05-06-2018, 08:06 PM
#21
Le Mans Master
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GM probably has thousands of hours of dyno testing on these engines, and may have determined that the 6500 redline gives the best combination of power, reliability and engine life, with the parts used.
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kenownr (05-08-2018)
05-06-2018, 08:22 PM
#23
I will say that even if it made slightly less power an extra 500 RPM would be nice for those situations where you run out of gear and would rather not upshift. With the C7 Z06 you are just shy of RPM in 4th on the front straight at VIR and could use a little more RPM instead of the early upshift to 5th. It's a similar situation at Summit Point in the the run from 2-3 and 3-4 in 3rd gear.
That said, maybe after all the complaints about valvetrain issues with the LS7 GM decided it wasn't worth the hassle to have the valvetrain designed for the extra RPM.
That said, maybe after all the complaints about valvetrain issues with the LS7 GM decided it wasn't worth the hassle to have the valvetrain designed for the extra RPM.
05-06-2018, 08:24 PM
#24
Team Owner
Some people seem to bring the C6 into every C7 conversation. 500 more RPM isn't really something to brag about. There comes a time where you have to stop living in the past.
Plus, you went on to say that the C6 ZR1 also had titanium rods and titanium intake valves(as did the LS7) and it still had a 6,500 RPM rev limiter. You contradicted your entire point of bringing the C6 into the conversation.
Plus, you went on to say that the C6 ZR1 also had titanium rods and titanium intake valves(as did the LS7) and it still had a 6,500 RPM rev limiter. You contradicted your entire point of bringing the C6 into the conversation.
Lighter rods and lighter cast pistons make the LS7 easier to spin to 7,000 RPM, vs lighter rods and heavier forged pistons in the LS9, and easier to spin to 7,000 RPM than with the LT4 or LT5 with heavier PM rods and heavier forged pistons.
Last edited by JoesC5; 05-06-2018 at 08:40 PM.
05-06-2018, 08:45 PM
#25
Le Mans Master
Experienced wearing valve guides!?
I will say that even if it made slightly less power an extra 500 RPM would be nice for those situations where you run out of gear and would rather not upshift. With the C7 Z06 you are just shy of RPM in 4th on the front straight at VIR and could use a little more RPM instead of the early upshift to 5th. It's a similar situation at Summit Point in the the run from 2-3 and 3-4 in 3rd gear.
That said, maybe after all the complaints about valvetrain issues with the LS7 GM decided it wasn't worth the hassle to have the valvetrain designed for the extra RPM.
That said, maybe after all the complaints about valvetrain issues with the LS7 GM decided it wasn't worth the hassle to have the valvetrain designed for the extra RPM.
In most engines it is not the reciprocating assembly that has a problem. the crank, pistons, and con rods are usually not the limiting factor. The limit is usually the valve train. Valves not closing fast enough because the lifter floats off the cam or because the valve spring is not strong enough, or even because the valve bounced off the seat. Then the valve hits the piston, and things break. Like connecting rods out the side of the block. Those are nice.
I own a 99 dodge with a v-10. Original RPM limit was 4250 RPM. Yes, that low. stainless competition valves and triple valve springs ( one spring inside the other, all 3 pulling on one valve ) made it possable to hit 6500 RPM where my limiter is currently set. Stainless is stronger and lighter, which makes it easier to return to rest once the valve is open.
https://forums.anandtech.com/threads/what-factors-limit-the-max-rpms-on-an-engine.905497/
It makes sense money and minimum design requirements are the limiting factors. No sense spending a bundle on a reciprocating assembly if the valve train is going limit you anyway.
Good point though!
05-07-2018, 08:33 AM
#26
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Lavender (05-07-2018)
05-07-2018, 08:39 AM
#27
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One question that I don't know the answer to is:
What speed can the supercharger be spun to, safely? Can it deal with ~7100RPMs (7000 redline + ~100 for cut-off)? At what point does that become too risky for the existing belts, mechanisms, etc? I'm betting that's what plays into the decision to an extent.
Also, you might be surprised to know that bumping the RPM range up will have an adverse effect on emissions. I seem to recall the Powertrain guys at GM were somewhat limited with the LT1 in the base car due to emissions. They could have easily kicked the redline and limiter up a few hundred RPMs to make more HP. But the results would have been a hit to the overall emissions, so they had to back off.
What speed can the supercharger be spun to, safely? Can it deal with ~7100RPMs (7000 redline + ~100 for cut-off)? At what point does that become too risky for the existing belts, mechanisms, etc? I'm betting that's what plays into the decision to an extent.
Also, you might be surprised to know that bumping the RPM range up will have an adverse effect on emissions. I seem to recall the Powertrain guys at GM were somewhat limited with the LT1 in the base car due to emissions. They could have easily kicked the redline and limiter up a few hundred RPMs to make more HP. But the results would have been a hit to the overall emissions, so they had to back off.
05-07-2018, 09:42 AM
#29
Also we should NOT settle for GM's parts bin mentality? What do you think your Grand Sport is?
Newsflash!!! Your Grand Sport is the definition of GM's parts bin mentality!
Trolls.... You gotta love 'em right?
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CorvettoBrando (05-07-2018)
05-07-2018, 09:53 AM
#30
Team Owner
All you attempted to do was to try and discredit me, by making it personal, of which you failed. Why didn't you make an attempt to answer the OP's question, instead of attacking me?
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VetterFlyer (05-12-2018)
05-07-2018, 10:01 AM
#31
Melting Slicks
Thread Starter
So you came here to tell us that a ZR1 just got crushed by a 520hp glorified "VW bug with a 6 cylinder" and that you love your 460hp Grand Sport?
Also we should NOT settle for GM's parts bin mentality? What do you think your Grand Sport is?
Newsflash!!! Your Grand Sport is the definition of GM's parts bin mentality!
Trolls.... You gotta love 'em right?
Also we should NOT settle for GM's parts bin mentality? What do you think your Grand Sport is?
Newsflash!!! Your Grand Sport is the definition of GM's parts bin mentality!
Trolls.... You gotta love 'em right?
I’ll probably buy a ZR1 in December. The high 1st gear annoys me, but the power is there without issues.
I just wish Chevy would quit compromising. Us accepting their Vettes like sheeple will just enable them. This car and company could be so much better.
05-07-2018, 10:03 AM
#32
Le Mans Master
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Also, you might be surprised to know that bumping the RPM range up will have an adverse effect on emissions. I seem to recall the Powertrain guys at GM were somewhat limited with the LT1 in the base car due to emissions. They could have easily kicked the redline and limiter up a few hundred RPMs to make more HP. But the results would have been a hit to the overall emissions, so they had to back off.
05-07-2018, 10:05 AM
#33
Team Owner
One question that I don't know the answer to is:
What speed can the supercharger be spun to, safely? Can it deal with ~7100RPMs (7000 redline + ~100 for cut-off)? At what point does that become too risky for the existing belts, mechanisms, etc? I'm betting that's what plays into the decision to an extent.
Also, you might be surprised to know that bumping the RPM range up will have an adverse effect on emissions. I seem to recall the Powertrain guys at GM were somewhat limited with the LT1 in the base car due to emissions. They could have easily kicked the redline and limiter up a few hundred RPMs to make more HP. But the results would have been a hit to the overall emissions, so they had to back off.
What speed can the supercharger be spun to, safely? Can it deal with ~7100RPMs (7000 redline + ~100 for cut-off)? At what point does that become too risky for the existing belts, mechanisms, etc? I'm betting that's what plays into the decision to an extent.
Also, you might be surprised to know that bumping the RPM range up will have an adverse effect on emissions. I seem to recall the Powertrain guys at GM were somewhat limited with the LT1 in the base car due to emissions. They could have easily kicked the redline and limiter up a few hundred RPMs to make more HP. But the results would have been a hit to the overall emissions, so they had to back off.
It's the other changes(ie: cam design, etc) to raise the horsepower at a higher RPM, that affects emissions.
I bet that the Porsche N/A six cylinder that runs to 9,000 RPM and produces more horsepower than the LT1, meets all applicable emission regulations.
Last edited by JoesC5; 05-07-2018 at 10:12 AM.
05-07-2018, 10:16 AM
#35
Team Owner
05-07-2018, 10:34 AM
#36
Le Mans Master
It's the average HP that makes those RPM's worth it. ;)
And like Poorsha said add those shifting options with His Stick Shifting!
Last edited by johnglenntwo; 05-07-2018 at 02:41 PM.
05-07-2018, 02:18 PM
#37
Melting Slicks
While it meets the required standards, it still puts out more emissions than the LT1. GM is going to be much more concerned about emissions with the LT1 than Porsche is going to be with the 4.0L in the RS because of shear volume of engines produced. The EPA has fleet emission requirements for manufactures. For all the LT1s sold GM has to sell much lower emissions vehicles to bring the fleet average down. The volume of LT1s is huge compared to the 4.0L RS engine which would make emissions much more of a concern to GM.
05-07-2018, 05:57 PM
#38
Le Mans Master
DOHC, and over squared stroke screams it up$ ;)
http://www.superchevy.com/how-to/vem...oke-of-genius/
DOHC would help the emissions, and it really works too!
;Bad ***
https://youtu.be/Pd_chxOouYY
The GT350R!?
DOHC would help the emissions, and it really works too!
https://youtu.be/Pd_chxOouYY
The GT350R!?
Last edited by johnglenntwo; 05-08-2018 at 06:49 AM.
05-07-2018, 09:39 PM
#39
Team Owner
My GS is without a doubt a parts bin special, I agree. It’s the right parts for me at the time. When I bought it - I actually bought 2 GS last year - I thought it was the best Corvette to buy. No pulling timing with high intake temps like the Z06, and much more enjoyable gear ratios.
I’ll probably buy a ZR1 in December. The high 1st gear annoys me, but the power is there without issues.
I just wish Chevy would quit compromising. Us accepting their Vettes like sheeple will just enable them. This car and company could be so much better.
The Z06 is best bang and is no compromising at the price!
05-08-2018, 06:09 AM
#40
Le Mans Master
with the new crank stronger and a more agressive cam more revs will be possible and provide much more boost as this blower is loafing
the issue will be the ability to tune for higher rpms and free up the exhaust side.
so since the tune is currently made out of unobtanium, what would you like to do today? you may have to settle for the general cooked up in the meantime and if the 755 doesn't do it for you maybe the ZR-1 isn't the right choice just yet.