How can I gain more top end powe in the VQ3.5L
05-03-2002, 12:16 AM
#41
Senior Member
Thread Starter
Join Date: Apr 2001
Posts: 903
My previous car was a Prelude and, as I'm sure you know, the H22 is a rev happy motor too. It wouldn't come alive until it changed cam profiles at 5500rpms....and after that it would pull all the way to 8000rpms. I miss that. While I'm not trying to make the VQ a torqueless rev happy motor, I would like to keep it strong until redline (6500).
05-03-2002, 06:17 AM
#43
Not DAVEB the parts guy
Join Date: Aug 2000
Posts: 8,555
I doubt a port and polish (Extrude Hone) would do anything for the 3.5 manifold. Honing doesn't do jack **** for the 95-99 VQ (been dynoed) and the 4th gen VQ has a lot more flashing. The 3.5 VQ just isn't the same rev happy motor the 00-01 and 3rd gen VE was. They made the 3.5 VQ to act like a V8. Strong torque that has a very flat curve. They made the low rpm runners really long, lowered the switch over, and the high rpm runners aren't as short as they were on the 00-01. Instead of having power peak right near redline as in the 00-01, the 02 plateaus at 5600-5800. What this ultimately means is less high end, better torque, more a useful powerband.
The ONLY way you can extend the peak power rpm is to change the intake manifold layout (ie shorten the high rpm runners) or add a SC. Either one of these improve breathing efficency. Adding a y-pipe, catback, UDP, intake, etc won't extend your ultimate useable rpms. Instead, you'll either gain more power through out the useable rpms and/or power won't fall off as fast after peak. You can't extend peak rpm without improving the efficency of the intact track.
Dave
The ONLY way you can extend the peak power rpm is to change the intake manifold layout (ie shorten the high rpm runners) or add a SC. Either one of these improve breathing efficency. Adding a y-pipe, catback, UDP, intake, etc won't extend your ultimate useable rpms. Instead, you'll either gain more power through out the useable rpms and/or power won't fall off as fast after peak. You can't extend peak rpm without improving the efficency of the intact track.
Dave
05-03-2002, 07:27 AM
#44
Donating Maxima.org Member
Join Date: Jul 2001
Posts: 608
Originally posted by 02MaximizedVQ
'
I was looking at the same thing the other day. That aluminum plenum that runs between the throttle body and the intake manifold could easily be accessed and ported or extrude honed. I wonder how much that part cost from the dealer? You could order one, ship it out to be ported and honed, then drop it in with no down time! Someone that has access to a dyno should try this.
Jesse
'
I was looking at the same thing the other day. That aluminum plenum that runs between the throttle body and the intake manifold could easily be accessed and ported or extrude honed. I wonder how much that part cost from the dealer? You could order one, ship it out to be ported and honed, then drop it in with no down time! Someone that has access to a dyno should try this.
Jesse
05-03-2002, 08:43 AM
#45
Newbie - Just Registered
Join Date: Apr 2002
Posts: 12
Usually, ECU's have +/-20% to play with, things like intake, y-pipe, exhaust increase flow and the ECU will adjust. The ECU adjusts based on the O2 reading from the O2sensors, it refers to its maps and then adjusts it.
About that crankswap ... I might have kicked myself in the teeth. I'm not sure if the valves wouldn't hit. and what size timing belt would you need. Thats a far fetched idea.
About the intake Manifold, I don't think that by adding short runners of any kind, shape or form you will alter the rev-happy (peak power at higher RPM) motor. I've seen short IM used on a not rev-happy motor, it made huge power mid-up range but still died out at the end.
About that crankswap ... I might have kicked myself in the teeth. I'm not sure if the valves wouldn't hit. and what size timing belt would you need. Thats a far fetched idea.
About the intake Manifold, I don't think that by adding short runners of any kind, shape or form you will alter the rev-happy (peak power at higher RPM) motor. I've seen short IM used on a not rev-happy motor, it made huge power mid-up range but still died out at the end.
05-03-2002, 10:30 AM
#46
Senior Member
Join Date: Sep 2001
Posts: 129
Originally posted by Batman_Canada
Usually, ECU's have +/-20% to play with, things like intake, y-pipe, exhaust increase flow and the ECU will adjust. The ECU adjusts based on the O2 reading from the O2sensors, it refers to its maps and then adjusts it.
About that crankswap ... I might have kicked myself in the teeth. I'm not sure if the valves wouldn't hit. and what size timing belt would you need. Thats a far fetched idea.
About the intake Manifold, I don't think that by adding short runners of any kind, shape or form you will alter the rev-happy (peak power at higher RPM) motor. I've seen short IM used on a not rev-happy motor, it made huge power mid-up range but still died out at the end.
Usually, ECU's have +/-20% to play with, things like intake, y-pipe, exhaust increase flow and the ECU will adjust. The ECU adjusts based on the O2 reading from the O2sensors, it refers to its maps and then adjusts it.
About that crankswap ... I might have kicked myself in the teeth. I'm not sure if the valves wouldn't hit. and what size timing belt would you need. Thats a far fetched idea.
About the intake Manifold, I don't think that by adding short runners of any kind, shape or form you will alter the rev-happy (peak power at higher RPM) motor. I've seen short IM used on a not rev-happy motor, it made huge power mid-up range but still died out at the end.
05-03-2002, 10:44 AM
#47
Not DAVEB the parts guy
Join Date: Aug 2000
Posts: 8,555
Originally posted by Batman_Canada
About the intake Manifold, I don't think that by adding short runners of any kind, shape or form you will alter the rev-happy (peak power at higher RPM) motor. I've seen short IM used on a not rev-happy motor, it made huge power mid-up range but still died out at the end.
About the intake Manifold, I don't think that by adding short runners of any kind, shape or form you will alter the rev-happy (peak power at higher RPM) motor. I've seen short IM used on a not rev-happy motor, it made huge power mid-up range but still died out at the end.
You do realize that your 2k2 does have a variable length intake manifold, right? There are two sets of intake runners dividied by a set of butterflies. At low rpms, the long runners are used, and at higher rpms the butterflies open and let the short runners breath. Short runners increase high rpm power thru reduced turbulence and increased intake velocity. I don't doubt the example you used and it sounds like the cam and valve train couldn't keep up with the increased air. However, I know that using SLP intake runners (4" shorter than stock) on the L98 350 in the 92 Z28 increases peak power from 4700rpms to 5200rpms. That's pretty significant. The motor looses a little torque, but the torque curve is flatter and longer, and the motor makes more HP at a higher rpm. This mod alone is good for about 15-20hp at the wheels. The intake manifold on the LT1 (93-97) F-Body used a small "tunnel ram" intake manifold which had very short 8" runners. Peak torque was lower than the L98, but the motor had 25-35 more HP and a much longer and flatter torque curve. The LT1 was .4 second quicker and 4mph faster than the L98 on average. Dave
Dave
05-03-2002, 11:31 AM
#48
Senior Member
Join Date: Sep 2001
Posts: 129
Originally posted by Batman_Canada
Another thing to take a look at is R/S (rod to stroke) ratio. Perfect Ratio of 1.75 would yield beuatifull top end, less of that would favour midrange, and more of that would require astronomical piston speed to provide enough velocity to create sufficient/required torque. 1.75R/S also means (more important one) that there is least stress on the sidewalls of the motor at high RPMS.
Lets say x = Rod length, y = stroke, z = stroke difference between 3.0L and 3.5L. If Nissan stroked the 3.0L by "Z" units and still used the same block, they have to decrease the length of the rod by "Z" units. Stay with me:
R/S of 3.0L = (persay) 1.53 ... which would mean:
x = 1.76, y = 1.15
Lets say Z = 0.2 for example
R/S of 3.5L would be: 1.15
x = x-z and y = y+z
So R/S ratio also effects top end. I personally don't think that by unrestricting flow, you can get a ton of whp from the VQ. Thats just me.
Hope that helped and that I haven't confused anyone. In any case I can be wrong, those are just my thoughts.
Laters,
~Andy
Another thing to take a look at is R/S (rod to stroke) ratio. Perfect Ratio of 1.75 would yield beuatifull top end, less of that would favour midrange, and more of that would require astronomical piston speed to provide enough velocity to create sufficient/required torque. 1.75R/S also means (more important one) that there is least stress on the sidewalls of the motor at high RPMS.
Lets say x = Rod length, y = stroke, z = stroke difference between 3.0L and 3.5L. If Nissan stroked the 3.0L by "Z" units and still used the same block, they have to decrease the length of the rod by "Z" units. Stay with me:
R/S of 3.0L = (persay) 1.53 ... which would mean:
x = 1.76, y = 1.15
Lets say Z = 0.2 for example
R/S of 3.5L would be: 1.15
x = x-z and y = y+z
So R/S ratio also effects top end. I personally don't think that by unrestricting flow, you can get a ton of whp from the VQ. Thats just me.
Hope that helped and that I haven't confused anyone. In any case I can be wrong, those are just my thoughts.
Laters,
~Andy
Also the only things that impact piston speed are RPM and Stroke Length, Rod/Stroke ratio itself does not have an impact on pistion speed. An engine with the same stroke and same rpm will have the same piston speed regardless of rod length. However piston acceleration is a different issue since the piston in an engine with a short R/S ratio (eg. 1.5) will spend less time at TDC the draw it will create as it moves away from TDC will be greater at the cost of spending less time up there meaning the burn could be less complete.
Anyway, technicalities asside, changing R/S ratio ain't gunna find you much HP, it might be worth messing with once you've exhausted absolutely all other possibilities but compared to S/C, turbo, N20, head work, proper cams, cam timing, compression ratio, etc, etc, it's a pretty lame place to go looking for HP.
05-03-2002, 11:37 AM
#49
Newbie - Just Registered
Join Date: Apr 2002
Posts: 12
Good points, you're right piston speed does not have anything to do with rod length ...
I think that having more ideal R/S ratio, would benefit top end power though .... *shrug* ... at least it should and those are my thoughts.
I'll get back to this later after some research.
I think that having more ideal R/S ratio, would benefit top end power though .... *shrug* ... at least it should and those are my thoughts.
I'll get back to this later after some research.
05-03-2002, 04:33 PM
#50
Senior Member
Join Date: Jan 2001
Posts: 1,816
Originally posted by Dave B
I doubt a port and polish (Extrude Hone) would do anything for the 3.5 manifold. Honing doesn't do jack **** for the 95-99 VQ (been dynoed) and the 4th gen VQ has a lot more flashing. The 3.5 VQ just isn't the same rev happy motor the 00-01 and 3rd gen VE was. They made the 3.5 VQ to act like a V8. Strong torque that has a very flat curve. They made the low rpm runners really long, lowered the switch over, and the high rpm runners aren't as short as they were on the 00-01. Instead of having power peak right near redline as in the 00-01, the 02 plateaus at 5600-5800. What this ultimately means is less high end, better torque, more a useful powerband.
The ONLY way you can extend the peak power rpm is to change the intake manifold layout (ie shorten the high rpm runners) or add a SC. Either one of these improve breathing efficency. Adding a y-pipe, catback, UDP, intake, etc won't extend your ultimate useable rpms. Instead, you'll either gain more power through out the useable rpms and/or power won't fall off as fast after peak. You can't extend peak rpm without improving the efficency of the intact track.
Dave
I doubt a port and polish (Extrude Hone) would do anything for the 3.5 manifold. Honing doesn't do jack **** for the 95-99 VQ (been dynoed) and the 4th gen VQ has a lot more flashing. The 3.5 VQ just isn't the same rev happy motor the 00-01 and 3rd gen VE was. They made the 3.5 VQ to act like a V8. Strong torque that has a very flat curve. They made the low rpm runners really long, lowered the switch over, and the high rpm runners aren't as short as they were on the 00-01. Instead of having power peak right near redline as in the 00-01, the 02 plateaus at 5600-5800. What this ultimately means is less high end, better torque, more a useful powerband.
The ONLY way you can extend the peak power rpm is to change the intake manifold layout (ie shorten the high rpm runners) or add a SC. Either one of these improve breathing efficency. Adding a y-pipe, catback, UDP, intake, etc won't extend your ultimate useable rpms. Instead, you'll either gain more power through out the useable rpms and/or power won't fall off as fast after peak. You can't extend peak rpm without improving the efficency of the intact track.
Dave
WELL, as you can tell by looking at the picture, the manifolds and heads on the VQ35DE are VERY different than on the VQ30. And as you say "You can't extend peak rpm without improving the efficiency of the intake tract."
I'm assuming by intake tract you're referring to.. intake, TB, intake manifolds/plenums, head, valve train... Well consider this, an intake alone has been dyno'ed to see a 10 hp gain. Now with people saying that they feel their 3.5's are running out of breath topend, why wouldn't some manifold/head porting improve this? This has been the way that hot rodders have historically solved this problem along with cams with more lift and duration.
Now also consider this, Nissan has managed to somehow squeeze 280 hp and 249 torque out of our bad boy VQ35. We've got half a liter more of air hungry displacement to work with, and the preliminary numbers for the Z and the G35 coupe seem to indicate there's at least another 30 or so horsies hiding up top. Now the question becomes, how do we get these out?
I've got a few ideas, but we'll have to see when the new Z comes out and people start tearin them apart
I'd like to see a 300 hp to the crank N/A maxima (preferably mine hehe)Fire away Dave, your skeptecism is always appreciated
05-03-2002, 05:34 PM
#51
Senior Member
Join Date: Aug 2000
Posts: 2,807
Depending on how agressive the cam specs are affects the driveablitily. For example lets assume someone got a more agressive grind that shifted the powerband up around 200-400rpm, so now you make more power from 3500-6700rpm. The problem is that the stock ECU will still run the same ignition timing curve that is calibrated for stock cams. The result is worse idle, lower power in some parts of the powerband and less throttle response. However if you were able to tune the ignition curve to the cams you could make the car idle simular to stock and increase the throttle response along with overall power. But without a JWT/G-force ECU a standalone is needed to maximize the gain. Normally it is recommended to do several base timing sweeps to find out what is the optimal settings. However it can't be done for VQ's 
.
.
Originally posted by Maximus1000
I guess camwork is the next logical progression, after a Y-pipe, high flow cat, and cat back exhaust to help the engine breathe as efficiently as possible. How would new cam profiles affect the ECU? Would you need a stand alone ECU with new cams? Would driveability be affected as well? If its all pros, I'll be up for that in about a month and half.
I guess camwork is the next logical progression, after a Y-pipe, high flow cat, and cat back exhaust to help the engine breathe as efficiently as possible. How would new cam profiles affect the ECU? Would you need a stand alone ECU with new cams? Would driveability be affected as well? If its all pros, I'll be up for that in about a month and half.
05-03-2002, 05:37 PM
#52
Senior Member
Join Date: Aug 2000
Posts: 2,807
I'm sure no one wants to tear into their brand new VQ35 to do headwork. Dave is right in regards to the different intake runner size. However a camshaft swap would increase power directly though. The VTC can be modified to run off a rpm switch to fine tune also. I have seen 2k1 pathfinder VQ35's in car-part.com for around $2000-4000 incase someone wants to build a VQ35 .
.
Originally posted by Chinkzilla
I think you've contradicted yourself my friend.. Like you say the new 3.5 VQ is a DIFFERENT engine, so how can you expect it to take to mods the same way? Your logic is, "well, it didn't work on the 3.0 VQ therefore it won't work on the 3.5 VQ"..
WELL, as you can tell by looking at the picture, the manifolds and heads on the VQ35DE are VERY different than on the VQ30. And as you say "You can't extend peak rpm without improving the efficiency of the intake tract."
I'm assuming by intake tract you're referring to.. intake, TB, intake manifolds/plenums, head, valve train... Well consider this, an intake alone has been dyno'ed to see a 10 hp gain. Now with people saying that they feel their 3.5's are running out of breath topend, why wouldn't some manifold/head porting improve this? This has been the way that hot rodders have historically solved this problem along with cams with more lift and duration.
Now also consider this, Nissan has managed to somehow squeeze 280 hp and 249 torque out of our bad boy VQ35. We've got half a liter more of air hungry displacement to work with, and the preliminary numbers for the Z and the G35 coupe seem to indicate there's at least another 30 or so horsies hiding up top. Now the question becomes, how do we get these out?
I've got a few ideas, but we'll have to see when the new Z comes out and people start tearin them apart I'd like to see a 300 hp to the crank N/A maxima (preferably mine hehe)
Fire away Dave, your skeptecism is always appreciated
I think you've contradicted yourself my friend.. Like you say the new 3.5 VQ is a DIFFERENT engine, so how can you expect it to take to mods the same way? Your logic is, "well, it didn't work on the 3.0 VQ therefore it won't work on the 3.5 VQ"..
WELL, as you can tell by looking at the picture, the manifolds and heads on the VQ35DE are VERY different than on the VQ30. And as you say "You can't extend peak rpm without improving the efficiency of the intake tract."
I'm assuming by intake tract you're referring to.. intake, TB, intake manifolds/plenums, head, valve train... Well consider this, an intake alone has been dyno'ed to see a 10 hp gain. Now with people saying that they feel their 3.5's are running out of breath topend, why wouldn't some manifold/head porting improve this? This has been the way that hot rodders have historically solved this problem along with cams with more lift and duration.
Now also consider this, Nissan has managed to somehow squeeze 280 hp and 249 torque out of our bad boy VQ35. We've got half a liter more of air hungry displacement to work with, and the preliminary numbers for the Z and the G35 coupe seem to indicate there's at least another 30 or so horsies hiding up top. Now the question becomes, how do we get these out?
I've got a few ideas, but we'll have to see when the new Z comes out and people start tearin them apart
I'd like to see a 300 hp to the crank N/A maxima (preferably mine hehe)Fire away Dave, your skeptecism is always appreciated
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