Am I a dummy or what

"traderQAMobileTestAutomationMobileBoostOn" (el-peasant) 01/26/2017 at 17:56 • Filed to: None

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Infiniti’s variable compression engine goes between 8.0:1 for power and 14:1 for economy. But doesn’t an increase in CR increase both ?

EDIT: Got it. I thought it was NA but the 8:1 with a turbo allows for no detonation while giving power; the 14:1 is for low-load, off-boost. 8:1 doesn’t make more power on its own, it allows for more with the turbo.

Decay buys too many beaters > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 18:00

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(i know nothing)

Is it turbo?

Arch Duke Maxyenko, Shit Talk Extraordinaire > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 18:00

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It’s also turbocharged and Turbos don’t get along with high compression in gas engines

BvdV - The Dutch Engineer > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 18:00

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I suspect it might have something to do with knock at higher engine speeds/loads(and thus higher powers) by lowering the CR in those regions the risk of knock reduces. (might be wrong though)

garagemonkee > Arch Duke Maxyenko, Shit Talk Extraordinaire 01/26/2017 at 18:01

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Which is why every car should be diesel.

traderQAMobileTestAutomationMobileBoostOn > Decay buys too many beaters 01/26/2017 at 18:03

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It is. That might explain something though I’m not entirely clear. If it has a turbo and doesn’t knock at 14:1 then why not run it all the time

Knock at higher loads probably? So the CR is reduced with an increase in power, I always thought it was NA. High CR for off-boost, low-load.

Arch Duke Maxyenko, Shit Talk Extraordinaire > garagemonkee 01/26/2017 at 18:04

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No, diesels blow ass

Decay buys too many beaters > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 18:04

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Its probably set up to decrease CR and run more boost, but I agree you should be able to run a much higher static CR with modern direct injection

Also you are correct that high CR increases both efficiency and power.

Future next gen S2000 owner > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 18:05

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Turbo + US pump gas(which is garbage) + high compression = detonation

They are bleeding off the boost when utilizing the higher compression. The high compression is better for light load applications when the turbo isn’t needed. It won’t make as much power at the high compression but you will get higher mpg.

Textured Soy Protein > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 18:05

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If I were to guess it probably runs high compression off boost and progressively lowers compression as boost rises, in order to be able to run more boost with less detonation. But I haven’t actually read anything about it so I don’t know for sure.

So...I googled it and hey, looks like my guess was right . Also it uses the variable compression gizmo to run in the Atkinson cycle in certain situations to maximize fuel economy.

HammerheadFistpunch > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 18:05

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it ALLOWS for power at 8:1, high compression ratio and high pressures/load = explosions where you don’t want them. i.e. it goes to low compression to allow for boost, and when off boost it goes to high compression for efficiency.

VajazzleMcDildertits - read carefully, respond politely > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 18:05

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Lowering the compression ratio does reduce the risk of pre-detonation quite a bit. It won’t be efficient if the gas lights mid-cycle, and additional fuel and air can be compressed at lower ratios more easily.

VajazzleMcDildertits - read carefully, respond politely > garagemonkee 01/26/2017 at 18:06

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If they could make the diesel blocks the same amount of mass as a regular gas engine block but retain the structure of the diesel blocks I am for that, although it stands to reason they’d just wind up doing HCCI Otto instead.

https://en.wikipedia.org/wiki/Homogeneous_charge_compression_ignition

For Sweden > Arch Duke Maxyenko, Shit Talk Extraordinaire 01/26/2017 at 18:07

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No they inject oil don’t you know anything about Diesels

garagemonkee > Arch Duke Maxyenko, Shit Talk Extraordinaire 01/26/2017 at 18:08

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VajazzleMcDildertits - read carefully, respond politely > HammerheadFistpunch 01/26/2017 at 18:22

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Yeah, that’s why the EJ25 on the STI did what it did for that long. Cause the ratio is 8.2:1. hellooo 19 mpg!

Tristan > traderQAMobileTestAutomationMobileBoostOn 01/26/2017 at 19:07

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Who wants to bet the VC-T will be saddled with some truly miserable Nissan CVT?