Is it reasonable for me to assume you can make the lower rpm cam lobes slightly more aggresive while making the higher rpm cam lobes much more aggresive? Any consequences to this besides not having as smooth of an idle and a little less power down low (VVL settings off?, upper RPM power unreachable? need new springs? etc).
Corey
Modified by MiniMan at 6:02 AM 10/11/2004
Cam Discussion
-
HeavyDuty
- Posts: 1281
- Joined: Tue Sep 23, 2003 4:51 pm
- Car: 1995 Infiniti Q45
95 Nissan 240SX S14
96 Nissan D21
06 Nissan 350Z Z33
Re: (MiniMan)
Yeah, there's actually three lobes per function (int & exh in a DOHC VTEC) on a Honda/Acura VTEC system.
There's two seperate lobes (pri/sec) that open one intake valve before the other (to increase swirling at low rpm's) and the VTEC lobe that is the large center lobe that when VTEC is engaged, both followers open at the same time at a higher lift. Duration can be changed as well on both cams depending on the application. (Turbo/N2O or S/C)
I remember hearing something about Aussie regrinds once for the VH but haven't expended the energy to pursue it.
I know what you mean, a trade off between silky smooth idle & bat out of hell upper rpm cam phasing. A little less down low in exchange for a lot more up top.
Is there a market for it?
Is it feasible?
There's two seperate lobes (pri/sec) that open one intake valve before the other (to increase swirling at low rpm's) and the VTEC lobe that is the large center lobe that when VTEC is engaged, both followers open at the same time at a higher lift. Duration can be changed as well on both cams depending on the application. (Turbo/N2O or S/C)
I remember hearing something about Aussie regrinds once for the VH but haven't expended the energy to pursue it.
I know what you mean, a trade off between silky smooth idle & bat out of hell upper rpm cam phasing. A little less down low in exchange for a lot more up top.
Is there a market for it?
Is it feasible?
911/Q45, thanks for that. I'm still getting used to the new search page setup. Turns out I should try searching through bodies of posts instead of titles. Appreciated.
Paul Zigouras said there is about 70hp to be gained by doing an N/A build up without cams (porting, polishing, raising the compression, etc). He also said to expect well over 400hp by going with aggresive cams on top of the build up. Anywhere from 410-420hp at the flywheel is expected.
Is there a market for it? Well, as with all things Q45... I doubt it. Maybe for a few people, sure... but not many.
Is it feasible? Dennis says:
Quote »The interferrence of the valve and piston [already have flycuts in piston] means no more lift can be used without new pistons. And 0.490 with a 1.5" diameter valve is already ultra high lift and is perfection for valve curtain area vs valve seat 5 angle cuts.
Cams won't help much because the runners and plenum is tuned to 4,000, 4600, 5600, and 6,000 rpm. Figure out a way to shorten the runners by 2-3" and increase their opening diameter [area] by 8-10% [and maintain the taper ratio] and you might retune the engine to a 6800 rpm HP peak and yield aroud 350-360 HP unfortunately you would lose so much torque at 55 mph cruise that you would have to bump the diff gear up by 25%..........to let the heavy Q cruise with AC on.[/quote]With having the engine built up w/cams, I doubt you'd notice a difference down low... but when you got up into the higher RPMs... I bet she'd be unreal. Having power down low is nice for daily driving, but REALLY showing an M3 whose boss on the highway is another thing. It's a trade off I guess and depends on what we'd want to do with the cars.
Corey
Paul Zigouras said there is about 70hp to be gained by doing an N/A build up without cams (porting, polishing, raising the compression, etc). He also said to expect well over 400hp by going with aggresive cams on top of the build up. Anywhere from 410-420hp at the flywheel is expected.
Is there a market for it? Well, as with all things Q45... I doubt it. Maybe for a few people, sure... but not many.
Is it feasible? Dennis says:
Quote »The interferrence of the valve and piston [already have flycuts in piston] means no more lift can be used without new pistons. And 0.490 with a 1.5" diameter valve is already ultra high lift and is perfection for valve curtain area vs valve seat 5 angle cuts.
Cams won't help much because the runners and plenum is tuned to 4,000, 4600, 5600, and 6,000 rpm. Figure out a way to shorten the runners by 2-3" and increase their opening diameter [area] by 8-10% [and maintain the taper ratio] and you might retune the engine to a 6800 rpm HP peak and yield aroud 350-360 HP unfortunately you would lose so much torque at 55 mph cruise that you would have to bump the diff gear up by 25%..........to let the heavy Q cruise with AC on.[/quote]With having the engine built up w/cams, I doubt you'd notice a difference down low... but when you got up into the higher RPMs... I bet she'd be unreal. Having power down low is nice for daily driving, but REALLY showing an M3 whose boss on the highway is another thing. It's a trade off I guess and depends on what we'd want to do with the cars.
Corey
-
Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Re: (MiniMan)
Most people would want enough torque at 55 mph [1850 rpm] to cruise with AC on........not be constantly down shifting at every tiny rise in the road or with a full load of passengers!
As it is, unless the engine is perfect there is too much downshifting [transmission reliability?]........just a function of 4300 pounds. Why engine nonperfection [dirt/plugs] eats the transmission up!
Study the changes in 97 Q they had to bump up diff to 3.694 [+4.4% with same transmission gears] with a drop of 15 lb/ft even in a lighter car with 4.1 liter engine..........There are reasons no 32 valve V8 in a 4,000 pound car turns less than 2,000 rpm at 60 mph.
Why the G35 AT has a 2.799 TOTAL 5th gear ratio vs the Q 2.455 TOP gear ratio turning 14% less rpm at cruise...........G35 AT turns 2280 vs 2000 at 60 mph to act like a 3.99 liter engine [for fuel consumption] even thought it weighs 500 pounds less.
The VVT [with 248 degree cam] in Q adds 20 lb/ft to WOT under 4600 rpm torque even 5-7 lb/ft at 60 mph cruise..........it is that close every single lb/ft counts!
Just like a seesaw if you raise above 6,000 rpm torque by 20, you will lose 20 at 2,000 rpm..........4,000 rpm is the pivot point. You will also have to raise smooth idle speed by 25% [700> 875]
As it is, unless the engine is perfect there is too much downshifting [transmission reliability?]........just a function of 4300 pounds. Why engine nonperfection [dirt/plugs] eats the transmission up!
Study the changes in 97 Q they had to bump up diff to 3.694 [+4.4% with same transmission gears] with a drop of 15 lb/ft even in a lighter car with 4.1 liter engine..........There are reasons no 32 valve V8 in a 4,000 pound car turns less than 2,000 rpm at 60 mph.
Why the G35 AT has a 2.799 TOTAL 5th gear ratio vs the Q 2.455 TOP gear ratio turning 14% less rpm at cruise...........G35 AT turns 2280 vs 2000 at 60 mph to act like a 3.99 liter engine [for fuel consumption] even thought it weighs 500 pounds less.
The VVT [with 248 degree cam] in Q adds 20 lb/ft to WOT under 4600 rpm torque even 5-7 lb/ft at 60 mph cruise..........it is that close every single lb/ft counts!
Just like a seesaw if you raise above 6,000 rpm torque by 20, you will lose 20 at 2,000 rpm..........4,000 rpm is the pivot point. You will also have to raise smooth idle speed by 25% [700> 875]
-
Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Re: (Q45tech)
The other problem is chain and chain gear wear/stretch! Not unusual to see a 5-8 even 10 degree retard against crank........this would show as a 2-5 degree change in CAS position...........the passenger bank is not easily measurable as no reference.
In 268,000 miles my chains have stretched about 7-8 degrees [roughly 0.125"x 2] [still less than 1% limit which would be 10 degrees] so my exhaust valves close at 15-16 ATDC instead of 8 degrees.........in away I already have a more aggressive high rpm cam and can sure tell the difference at idle from 10 years ago.........especially with AC on.
In 268,000 miles my chains have stretched about 7-8 degrees [roughly 0.125"x 2] [still less than 1% limit which would be 10 degrees] so my exhaust valves close at 15-16 ATDC instead of 8 degrees.........in away I already have a more aggressive high rpm cam and can sure tell the difference at idle from 10 years ago.........especially with AC on.