since i dont know i am asking.
and also can it be manipulated, like lets say a car that comes stock makes peak power at 5500 rpm, can i somehow move this up to 6000 or lower to 5000?
What mechanicaly/physicaly makes a peak power point?
what determines where peak power is attained?
weight of the internals, internal friction, amount of air and fuel that you can stuff in (higher you go the more difficult it gets), strength of internals.
if you could make all the internals of the engine lighter you could make the engine rev higher because there will be less tensile and compressive stress on the parts due to momentum. otherwise they will just rip themselfs apart, im sure youve seen horror stories/pictures of car that overrevved and something snapped and basically BOOM. making a certain part stronger would prevent this but remember the heavier something is the harder the engine must work to get it moving, basically defeating what your trying to do. if you can make it lighter and stronger... then your golden :icesangel.
also air and fuel can only be fed in so fast... once you get past a certain point the engine cannot feed itself efficiently enough and power will taper off the faster you go (will be getting less and less air+fuel). turbo, better valve surface + design, higher flowing injectors, and less restrictive intake solves this.
as the engine revs faster parts are rubbing against each other faster which equals more friction to overcome.
there is probably more things that other people can explain better than me
if you could make all the internals of the engine lighter you could make the engine rev higher because there will be less tensile and compressive stress on the parts due to momentum. otherwise they will just rip themselfs apart, im sure youve seen horror stories/pictures of car that overrevved and something snapped and basically BOOM. making a certain part stronger would prevent this but remember the heavier something is the harder the engine must work to get it moving, basically defeating what your trying to do. if you can make it lighter and stronger... then your golden :icesangel.
also air and fuel can only be fed in so fast... once you get past a certain point the engine cannot feed itself efficiently enough and power will taper off the faster you go (will be getting less and less air+fuel). turbo, better valve surface + design, higher flowing injectors, and less restrictive intake solves this.
as the engine revs faster parts are rubbing against each other faster which equals more friction to overcome.
there is probably more things that other people can explain better than me
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Q45tech
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Generally the peak horsepower occurs 1500-2500 rpm above what ever the torque peak rpm is.The torque peak rpm is found where ever the volumetric efficiency is highest [the rpm where the most air charge is ingested and maintained for compression].
If you had to say what one thing was most important in setting the torque peak rpm that would probably be the cam duration and cam maximum lift. The duration sets the mid point of the seesaw.The higher the torque peak rpm the lower the torque will be at low rpms.
The critical aspect is having enough torque at 1500-2000 rpm for the weight of the vehicle to maintain speed on inclines without down shifting.
The problem with street engines is they must work from idle to cruise rpm.
With conventional mass produced pistons and rods, the stroke length sets the maximum SAFE piston speed.......on a Q 3.256" stroke equates to approximately 7300 rpm. However for safety and longevity the facory uses a 6900 rpm redline [where ecu cuts the fuel].With a 4,000 rpm torque peak and the multi- tuned plenum a Q actually has TWO horsepower peak rpms: 5,500 and 6,000 rpm with a slight dip in power between the two peaks [the exact rpm of all three events will vary depending on the ambient temperature, as the tuning [filling wavespeed varies with temperature].The two peaks are a type of supercharging [plenum runner tuning] where the length of the runners from the midpoint [lift] of the intake valves to the plenum and the inside diameter of the runner and the piston speed all come together in unison and add something like 5-6% more air than at lower or higher rpms.
If you make the valves too large they will favor rpm above the range of the engine, same with keeping the valves open to long or having too much lift too early.
You can have some cake and eat it too if you are willing to have an engine idle faster say 1300 rpms but it would be uncomfortable for average driver and the gas consumption at idle would double. Cruise would be at 3,000 rpm instead of 2,000 so fuel consumption would be 50% worse but you could have a torque peak at 5,000 and a HP peak at 6700 or 6,900 and the HP would be 360-370 but the torque would be the same just at a higher rpm.
If you had to say what one thing was most important in setting the torque peak rpm that would probably be the cam duration and cam maximum lift. The duration sets the mid point of the seesaw.The higher the torque peak rpm the lower the torque will be at low rpms.
The critical aspect is having enough torque at 1500-2000 rpm for the weight of the vehicle to maintain speed on inclines without down shifting.
The problem with street engines is they must work from idle to cruise rpm.
With conventional mass produced pistons and rods, the stroke length sets the maximum SAFE piston speed.......on a Q 3.256" stroke equates to approximately 7300 rpm. However for safety and longevity the facory uses a 6900 rpm redline [where ecu cuts the fuel].With a 4,000 rpm torque peak and the multi- tuned plenum a Q actually has TWO horsepower peak rpms: 5,500 and 6,000 rpm with a slight dip in power between the two peaks [the exact rpm of all three events will vary depending on the ambient temperature, as the tuning [filling wavespeed varies with temperature].The two peaks are a type of supercharging [plenum runner tuning] where the length of the runners from the midpoint [lift] of the intake valves to the plenum and the inside diameter of the runner and the piston speed all come together in unison and add something like 5-6% more air than at lower or higher rpms.
If you make the valves too large they will favor rpm above the range of the engine, same with keeping the valves open to long or having too much lift too early.
You can have some cake and eat it too if you are willing to have an engine idle faster say 1300 rpms but it would be uncomfortable for average driver and the gas consumption at idle would double. Cruise would be at 3,000 rpm instead of 2,000 so fuel consumption would be 50% worse but you could have a torque peak at 5,000 and a HP peak at 6700 or 6,900 and the HP would be 360-370 but the torque would be the same just at a higher rpm.
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Q45tech
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You are confusing me with an expert, thousands maybe tens/hundreds of thousands of engine engineers throughout the world know much more about this.
What is really impressive is the new Q engine [same bore same stroke] gets 12% more HP with only 6.7% more rpms over the JWT ecu reoptimization. The peak torque values are roughly equal however. But the area under the torque curve is higher on the new engine ....more torque at lower and higher than peak rpms.The competition is struggling since the limits for streetable [emissions] engines are close to hitting a wall vs displacement. It has come down to major costs to get 1,2,3,4 more lb/ft-HP.
Lighter parts means narrower bearings are possible yielding less friction, lighter valves mean lighter springs thus less friction.Its not so much about increasing the BMEP to yield more presuure [we are fuel octane limited now] as it is about having less friction to yield more flywheel HP..
What is really impressive is the new Q engine [same bore same stroke] gets 12% more HP with only 6.7% more rpms over the JWT ecu reoptimization. The peak torque values are roughly equal however. But the area under the torque curve is higher on the new engine ....more torque at lower and higher than peak rpms.The competition is struggling since the limits for streetable [emissions] engines are close to hitting a wall vs displacement. It has come down to major costs to get 1,2,3,4 more lb/ft-HP.
Lighter parts means narrower bearings are possible yielding less friction, lighter valves mean lighter springs thus less friction.Its not so much about increasing the BMEP to yield more presuure [we are fuel octane limited now] as it is about having less friction to yield more flywheel HP..
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Q45tech
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Everyone [well almost] is waiting for the full phase in of low sulfur fuel before attempting direct injection........which could allow an extra 10>8>7>6% more torque since the gasoline will no longer displace the air during the intake charge.....the fuel squirt takes up room in the cylinder..........on current engines the fuel may be spraying 60-66% of the time the air is flowing in [at WOT].
11millisec/16.6 millisec=66%
More air in + more fuel in to maintain the AF so more power across the rpm range.......you will see the first 80-82 lb/ft per liter street engines the current Q 333 could go as high as 360/370 lb/ft [even HP] from the same displacement.
11millisec/16.6 millisec=66%
More air in + more fuel in to maintain the AF so more power across the rpm range.......you will see the first 80-82 lb/ft per liter street engines the current Q 333 could go as high as 360/370 lb/ft [even HP] from the same displacement.
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maxnix
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1995 Infiniti Q45t
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VK45DE vs. VK45DD
It would be interesting to see what the actual torque specifications are on a dynamometer of a VK45DD vs a VK45DE.Q45tech wrote:More air in + more fuel in to maintain the AF so more power across the rpm range.......you will see the first 80-82 lb/ft per liter street engines the current Q 333 could go as high as 360/370 lb/ft [even HP] from the same displacement.
Wonder if the JDM specifications are sandbagged?
From the Infiniti -me (Middle East) site:
Feature Description Horsepower 365 HP @ 6,400 RPM Torque 47.8kg-m @ 4,000 RPM Which would be 345.74 Ft. Lb., if my calculations are correct. 76.93 ft. lb. per liter is pretty good.
Unfortunately, I can't determine if it is a DE or DD engine.
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Q45tech
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The low torque 333 vs 345 suggests just a software tweek.......they would have exceeded the transmission specs above 333 lb/ft. The "torque up redesign" is still in progress on the light 72 Kg..[old 4speed weight 97 Kg].......JR507E =450N/meters torque.
You for got the extra 2 digits 76.9336 lb/ft per liter
You for got the extra 2 digits 76.9336 lb/ft per liter
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
http://www.idavette.net/hib/02ls6/page2.htm"The ’01 intake weighed 99 grams but the ’02 weighs only 76. The ’01 exhaust weighed 86 grams but the ’02 exhaust weighs 63 grams. The exhaust stems are filled with a 78% potassium/22% sodium mix to help cool the valve. "NaK" is unstable and may spontaneously combust when exposed to air with 50% or higher humidity. Do not cut open or shorten 02 Z06 exhaust valve stems."
""Even with the lighter valves," Juriga said, "we still needed better control because we open and close them very fast. The closed loads are the same–400 Newtons (90lbs) on the seat–but the open loads increase from 1150N (259lbs) to 1310N (294lbs) for both springs.""
http://www.idavette.net/hib/02ls6/page5 ... /page6.htm
Based on the above 1.17 HP/ci the 274 Q would need to be 320 HP this is achievable with JWT ecu and loud exhaust and some intake cool air mods.
""Even with the lighter valves," Juriga said, "we still needed better control because we open and close them very fast. The closed loads are the same–400 Newtons (90lbs) on the seat–but the open loads increase from 1150N (259lbs) to 1310N (294lbs) for both springs.""
http://www.idavette.net/hib/02ls6/page5 ... /page6.htm
Based on the above 1.17 HP/ci the 274 Q would need to be 320 HP this is achievable with JWT ecu and loud exhaust and some intake cool air mods.
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maxnix
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Couldn't feel them so I rounded.Q45tech wrote:You forgot the extra 2 digits 76.9336 lb/ft per liter
It is a DE engine, but what is more interesting to me is the VH45DD engine achieves only 46 kg-m at a lower 3600 rpm, but with a higher 11 to 1 static compression ratio. This is for the two wheel drive verison only. Evidently, the four wheel drive versions have less power. Maybe its the way they measure since there would be more component drag in all wheel drive.__________________Brian1995 Q45 & Q45t
Discover the power of the button!
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s13sr20chris
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maxnix wrote:
It is a DE engine, but what is more interesting to me is the VH45DD engine achieves only 46 kg-m at a lower 3600 rpm, but with a higher 11 to 1 static compression ratio. This is for the two wheel drive verison only. Evidently, the four wheel drive versions have less power. Maybe its the way they measure since there would be more component drag in all wheel drive.__________________Brian1995 Q45 & Q45t
Discover the power of the button!
thats wierd
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s13sr20chris
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Q45tech
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You could design such an engine but why? The stroke length sets the max safe rpm, then you back off a safe amount depending on the longevity you want......that is where you set rev limiter then you back off from the rev limiter rpm 7-8% and say that is the rpm for max HP.
The problem with a street engine is it must idle at a low rpm and have enough torque at a low cruise rpm.......this pretty much limits the cams you can use.
The problem with a street engine is it must idle at a low rpm and have enough torque at a low cruise rpm.......this pretty much limits the cams you can use.