How to get some low end power?
11-12-2010, 10:27 AM
#41
Long tubed intakes seem to boost low and midrange power but suck @ higher rpms due to being to restrictive due to it's length..... most longer tubes make good low/mid range gains and most shorter tubes make better mid/high range gains.....But when a JWT 6" bellmouthed SRI is used in conjunction with the Helmholtz and Oem muffler the lowside is still linear and crisp.....play around with it....you'll see!
....guess ill take your word for it....maybe things have changed....but when i did a true CAI on my old 3rd gen, my low end seemed to suffer....but watch out when i would do a high speed run....really could feel a difference...
11-12-2010, 05:13 PM
#42
As far as the SRI vs. CAI discussion, a rough summary of the theory is as follows: under low-flow conditions (low rpm--> low air velocity), the increased density of the air from a CAI aids low-end performance. Low velocity has a minimal pressure loss, calculated as follows:
h_f = f*(L/d)*(V^2/2*g)
Note that this depends on velocity^2 and length/diameter of tube (f = friction factor, g = gravitational constant). Also, the longer intake runner produces lower-frequency pressure waves that aid cylinder filling at low rpm.
However, under the reverse conditions (high-flow--> high rpm--> high air velocity), pressure loss increases and the air heats up less, reducing at least some of the benefit of cold vs. warm air intake. (That is why spacers add the ~10 hp midrange and only ~1 hp peak). Similarly, the SRI produces a smaller pressure loss at high rpm (than CAI) and produces high-frequency pressure waves, both of which aid top-end filling. It is for this reason that OEMs are now producing dual- or [completely] variable-length intake runners. Helmholz resonators are primarily for sound-tuning, but do slightly negatively affect the flow.
This is just the theory. Each setup clearly has an optimized performance point (e.g. rpm of maximum benefit).
h_f = f*(L/d)*(V^2/2*g)
Note that this depends on velocity^2 and length/diameter of tube (f = friction factor, g = gravitational constant). Also, the longer intake runner produces lower-frequency pressure waves that aid cylinder filling at low rpm.
However, under the reverse conditions (high-flow--> high rpm--> high air velocity), pressure loss increases and the air heats up less, reducing at least some of the benefit of cold vs. warm air intake. (That is why spacers add the ~10 hp midrange and only ~1 hp peak). Similarly, the SRI produces a smaller pressure loss at high rpm (than CAI) and produces high-frequency pressure waves, both of which aid top-end filling. It is for this reason that OEMs are now producing dual- or [completely] variable-length intake runners. Helmholz resonators are primarily for sound-tuning, but do slightly negatively affect the flow.
This is just the theory. Each setup clearly has an optimized performance point (e.g. rpm of maximum benefit).
11-20-2010, 12:10 AM
#47
Junior Member
Join Date: Oct 2010
Location: W. Wyoming Pa
Posts: 32
DIY Intake Spacers and some other power methods...
The intake spacers definitely help. I wasn't about to pay $215 bucks for $20 worth of phenolic board so I ordered a 4" X 20" piece of 1/4" and 2 4" X 14" X1/16th" pieces of phenolic board and made my own. I ported and polished my entire intake path out 5+ mm so I would have had to bore them out anyway so I just used my intake as a stencil of sorts and router'ed out my own. I don't want to advertise for any one phenolic board supplier but if you google it like I did they are not hard to find. The additional space is not so much the cause of the added power. The fact that they insulate the intake from the engines heat lowering the air temperature entering the heads causing the air to be much denser. More air + More fuel = More power. I also bypassed the intake heater circuit and have had no problems even here in N.E. PA where it gets a little cold. I'm not knocking a kid for making a buck but charging $215 bucks for the spacers is a little rough. I made mine for under $50 bucks including shipping, longer studs and the barbed coupler to bypass the intake heater. I definitely noticed a difference though. Porting out your lower intake and polishing it to a shine does way more though. That lower intake really strangles all the VQ's. Headers and Y-Pipe are a must too. I have a generation 4 96 Maxima and people freak when they see the kind of nuts it has for doing everything home school. I made a flapper out of a spring parts grabber and dowel with a slot to hone out the upper plenum. You make a slot in the 3/4" dowel, wrap it in coarse emery paper and run it up and down each run of the plenum 10 times then change the emery cloth and move on to the next runner. That keeps them all even. I must have spent 20+ hours doing that to open up the runners 5+mm each to match the the ported lower intake. I installed another 1/4" phenolic board spacer between my throttle body and plenum though I don't think that had any affect one way or the other and removed it as it was making my intake rub. I ported out the throttle body 4mm and fabricated a larger butterfly and machined the obscenely large butterfly shaft down to 3/16th's of an inch looking at it in the open position so that it does not restrict the airflow. That definitely helped! You can hear a serious amount of air going into that thing with the short ram intake. It makes people jump away from the car when you crack the throttle. I use a dedicated onboard kiosk size computer I tossed together to run the consult cable via touchscreen for engine management. I run a gas conserving profile below half throttle and offset the rev limiter to 7200rpm. Once the throttle position sensor goes past 1/2 throttle it goes into more aggressive mode advancing ignition timing and fuel maps so it's the best of both worlds. Before I opened up the intake and installed the headers the VQ30DE stopped making more power around 5600RPM, it just wasn't breathing right. I used hillbilly engineering and opened everything up a far as possible within reason and voilà! It's a real tire wrecker. While I was redoing the engine I went with the 3.5L Rev-up cams and valve springs out of a twisted up 350Z. They have a little more height to them. There's also 2 more degrees of overlap, there is a little more time when both the intake and exhaust valves are open at the same time. That really helps at higher RPMs. I don't plan on supercharging it, If you plan on supercharging or running turbo or turbos try to find cams with as little overlap as possible. Adding a 1mm spacer between your springs and retainers also gives you a little more tension so you don't get valve float at high RPMs. The extra 1mm of lift and slightly longer duration of the 3.5L cams gives it a nice lope at idle too. When you add all of the above mods together it's crazy. Next time I rebuild the engine I'm going to try 10 to 1 compression pistons and some good I beam rods. I'm still beating the stock lowers. It only has 92,600 miles on it and they seem to be solid still so I saved a little money figuring I would finish the bottom end next round. I have another VQ30DE in my parts i30, I may just build that one up. I found a source for the MEVI's brand new for $400 and I want to see how they run after a through porting and polishing. It's a ***** honing out long curved runners but it is well worth the effort. Just make sure you keep a pattern up so they all come out exactly the same size. If I get a little extra cash up I may just have it extrusion honed professionally but I'm sorta cheap and like to do everything myself for free. I found that if you have patience and some skill you can do a nice job with a flapper setup and a die grinder. It just takes major time and commitment. Nothing cool is easy I guess. One last thing. When you port and polish your heads never polish the combustion chamber! It will lower your compression ratio. Just lightly round the sharp edges where they meet the cylinder wall as those sharp edges will act like glow plugs causing premature detonation at higher RPMs and compression ratios if you are running crap gas. I religiously run 93 octane even though my compression is not crazy high. Not only can you go farther advanced on the ignition timing it also keeps all the crap from building up in your engine. You don't want your ECU throwing it into Briggs and Stratton mode all the time from the knock sensor going off .
Ps. Someone mentioned a 35+ shot of nitrous for low end torque??? Don't ever blow nitrous at low RPM and make sure it only blows at WOT. I would never use nitrous on something I plan on driving for a while. Save the nitrous for the rental cars!
Ps. Someone mentioned a 35+ shot of nitrous for low end torque??? Don't ever blow nitrous at low RPM and make sure it only blows at WOT. I would never use nitrous on something I plan on driving for a while. Save the nitrous for the rental cars!
11-22-2010, 07:16 PM
#50
Senior Member
Join Date: Sep 2010
Location: Jacksonville, FL
Posts: 10,349
How many miles are on the engine you want to gain more low end torque? If there's alot of miles on it I'd do a compression check and go from there before you spend any money on any mods. Nothing will work well to gain the torque you desire if you're not getting proper compression.
11-22-2010, 08:54 PM
#51
11-23-2010, 11:04 AM
#52
Member
Join Date: Oct 2010
Location: Mississauga, ON, Canada
Posts: 48
As far as the SRI vs. CAI discussion, a rough summary of the theory is as follows: under low-flow conditions (low rpm--> low air velocity), the increased density of the air from a CAI aids low-end performance. Low velocity has a minimal pressure loss, calculated as follows:
h_f = f*(L/d)*(V^2/2*g)
Note that this depends on velocity^2 and length/diameter of tube (f = friction factor, g = gravitational constant). Also, the longer intake runner produces lower-frequency pressure waves that aid cylinder filling at low rpm.
However, under the reverse conditions (high-flow--> high rpm--> high air velocity), pressure loss increases and the air heats up less, reducing at least some of the benefit of cold vs. warm air intake. (That is why spacers add the ~10 hp midrange and only ~1 hp peak). Similarly, the SRI produces a smaller pressure loss at high rpm (than CAI) and produces high-frequency pressure waves, both of which aid top-end filling. It is for this reason that OEMs are now producing dual- or [completely] variable-length intake runners. Helmholz resonators are primarily for sound-tuning, but do slightly negatively affect the flow.
This is just the theory. Each setup clearly has an optimized performance point (e.g. rpm of maximum benefit).
h_f = f*(L/d)*(V^2/2*g)
Note that this depends on velocity^2 and length/diameter of tube (f = friction factor, g = gravitational constant). Also, the longer intake runner produces lower-frequency pressure waves that aid cylinder filling at low rpm.
However, under the reverse conditions (high-flow--> high rpm--> high air velocity), pressure loss increases and the air heats up less, reducing at least some of the benefit of cold vs. warm air intake. (That is why spacers add the ~10 hp midrange and only ~1 hp peak). Similarly, the SRI produces a smaller pressure loss at high rpm (than CAI) and produces high-frequency pressure waves, both of which aid top-end filling. It is for this reason that OEMs are now producing dual- or [completely] variable-length intake runners. Helmholz resonators are primarily for sound-tuning, but do slightly negatively affect the flow.
This is just the theory. Each setup clearly has an optimized performance point (e.g. rpm of maximum benefit).
I might be understanding what you wrote wrong, but does that mean the True CAI will increase your low end power and decrease your high end power or would it just not affect your high end power? And SRIs will make you lose some low end power and give a gain in your high end power?
If that's the case where True CAI is for good for low end power and SRI for high end, that sucks! Haha is there any intake setup that gives you both a boost in low and high end power?
11-24-2010, 09:31 AM
#53
Yeah, he answered that question by writing, "It is for this reason that OEMs are now producing dual- or [completely] variable-length intake runners." People on the Org are obsessed with shifting that powerband north to higher RPM. This aids driving on a track, where your RPM will never be dropping below 3500 or so, but hurts driving on the street. Unless you drive on the street the same way as on the track. =/
The manufacturers have realized they can use recent developments in technology to optimize the intake for a variety of conditions. The VQ35DEs have that present in the VIAS that increases or shortens the "effective length" of the intake runners depending on its open or closed position. The block plate NWP sells prevents it from ever opening which keeps it stuck in "help high RPM" mode (unless I have that flip-flopped? A block plate would imply it never opens). The FSM has a nice picture illustrating how this changes the airflow.
You'd have to ask members like Rochester to see why they removed their block plate to revert their manifold back to stock.
The manufacturers have realized they can use recent developments in technology to optimize the intake for a variety of conditions. The VQ35DEs have that present in the VIAS that increases or shortens the "effective length" of the intake runners depending on its open or closed position. The block plate NWP sells prevents it from ever opening which keeps it stuck in "help high RPM" mode (unless I have that flip-flopped? A block plate would imply it never opens). The FSM has a nice picture illustrating how this changes the airflow.
You'd have to ask members like Rochester to see why they removed their block plate to revert their manifold back to stock.
11-24-2010, 09:54 AM
#54
The point of deleting the valve apparatus in its entirety is that the opening is larger without the valve than it is with it but in an open position. Better air flow over 4K (or there-abouts), when you're needing more air. There's also an urban myth about modified cars requiring more air and thereby introducing a turbulence that the VIAS actuator can't handle, resulting in a fluttering of the valve... but that's pure conjecture. I personally don't subscribe to that, because the spring is very strong. But IDK really. It makes for a good discussion, either way.
I didn't even bother trying to read that run-on paragraph. Too bad, too, because it looks like a lot of thought went into it. Oh well.
Here's a picture of the valve. Compare the surface area of the circle to the expanded surface area of the entire valve, and you'll see what I mean.
And here's a picture of the block-off plate (BOP) from NWP. This is their premium plate.
It's made with a little more bling in mind.
Last edited by Rochester; 11-24-2010 at 10:09 AM.
11-25-2010, 06:30 AM
#55
Senior Member
Join Date: Feb 2008
Location: Central TX
Posts: 338
Editorial liberties exercised!
"Block-plate" is a curious name for this mod. It's not blocking anything, per se, except the hole at the UIM elbow. "VIAS-delete" is more appropriate. Without the VIAS butterfly valve, the UIM is always open.
The point of deleting the valve apparatus in its entirety is that the opening is larger without the valve than it is with it but in an open position. Better air flow over 4K (or there-abouts), when you're needing more air. There's also an urban myth about modified cars requiring more air and thereby introducing a turbulence that the VIAS actuator can't handle, resulting in a fluttering of the valve... but that's pure conjecture. I personally don't subscribe to that, because the spring is very strong. But IDK really. It makes for a good discussion, either way.
I didn't even bother trying to read that run-on paragraph. Too bad, too, because it looks like a lot of thought went into it. Oh well.
Here's a picture of the valve. Compare the surface area of the circle to the expanded surface area of the entire valve, and you'll see what I mean.
And here's a picture of the block-off plate (BOP) from NWP. This is their premium plate.
It's made with a little more bling in mind.
The point of deleting the valve apparatus in its entirety is that the opening is larger without the valve than it is with it but in an open position. Better air flow over 4K (or there-abouts), when you're needing more air. There's also an urban myth about modified cars requiring more air and thereby introducing a turbulence that the VIAS actuator can't handle, resulting in a fluttering of the valve... but that's pure conjecture. I personally don't subscribe to that, because the spring is very strong. But IDK really. It makes for a good discussion, either way.
I didn't even bother trying to read that run-on paragraph. Too bad, too, because it looks like a lot of thought went into it. Oh well.
Here's a picture of the valve. Compare the surface area of the circle to the expanded surface area of the entire valve, and you'll see what I mean.
And here's a picture of the block-off plate (BOP) from NWP. This is their premium plate.
It's made with a little more bling in mind.
The additional space is not so much the cause of the added power. The fact that they insulate the intake from the engines heat lowering the air temperature entering the heads causing the air to be much denser. More air + More fuel = More power. I also bypassed the intake heater circuit and have had no problems even here in N.E. PA where it gets a little cold. I'm not knocking a kid for making a buck but charging $215 bucks for the spacers is a little rough. I made mine for under $50 bucks including shipping, longer studs and the barbed coupler to bypass the intake heater. I definitely noticed a difference though.
Porting out your lower intake and polishing it to a shine is very effective. The lower intake really strangles all the VQ's. Headers and Y-Pipe are a must too. I have a 4th gen 96 Maxima and people freak when they see the kind of H.P. it produces with DIY mods.
I also made a flapper out of a spring parts grabber and dowel with a slot to hone out the upper plenum. You make a slot in the 3/4" dowel, wrap it in coarse emery paper and run it up and down each run of the plenum 10 times then change the emery cloth and move on to the next runner. That keeps them all even. I must have spent 20+ hours doing that to open up the runners 5+mm each to match the ported lower and upper intake. I also installed another 1/4" phenolic board spacer between my throttle body and plenum, though I don't think that had any affect one way or the other and removed it as it was making my intake rub.
I ported out the throttle body 4mm and fabricated a larger butterfly and machined the obscenely large butterfly shaft down to 3/16th's of an inch looking at it in the open position so that it does not restrict the airflow. That definitely helped! You can hear a serious amount of air going into that thing with the short ram intake. It makes people jump away from the car when you crack the throttle.
I use a dedicated onboard kiosk size computer I tossed together to run the consult cable via touchscreen for engine management. I run a gas conserving profile below half throttle and offset the rev limiter to 7200rpm. Once the throttle position sensor goes past 1/2 throttle it goes into more aggressive mode advancing ignition timing and fuel maps so it's the best of both worlds. Before I opened up the intake and installed the headers the VQ30DE stopped making more power around 5600RPM, it just wasn't breathing right.
I used hillbilly engineering and opened everything up a far as possible within reason and voilà! It's a real tire wrecker. While I was redoing the engine I went with the 3.5L Rev-up cams and valve springs out of a twisted up 350Z. They have a little more height to them. There's also 2 more degrees of overlap, there is a little more time when both the intake and exhaust valves are open at the same time. That really helps at higher RPMs. I don't plan on supercharging it, If you plan on supercharging or running turbo or turbos try to find cams with as little overlap as possible. Adding a 1mm spacer between your springs and retainers also gives you a little more tension so you don't get valve float at high RPMs. The extra 1mm of lift and slightly longer duration of the 3.5L cams gives it a nice lope at idle too.
When you add all of the above mods together it's crazy. Next time I rebuild the engine I'm going to try 10 to 1 compression pistons and some good I beam rods. I'm still beating the stock lowers. It only has 92,600 miles on it and they seem to be solid still so I saved a little money figuring I would finish the bottom end next round. I have another VQ30DE in my parts i30, I may just build that one up.
I found a source for the MEVI's brand new for $400 and I want to see how they run after a through porting and polishing. It's a ***** honing out long curved runners but it is well worth the effort. Just make sure you keep a pattern up so they all come out exactly the same size. If I get a little extra cash up I may just have it extrusion honed professionally but I'm sort of cheap and like to do everything myself for free. I found that if you have patience and some skill you can do a nice job with a flapper setup and a die grinder. It just takes major time and commitment. Nothing cool is easy I guess.
One last thing; When you port and polish your heads, never polish the combustion chamber! It will lower your compression ratio. Just lightly round the sharp edges where they meet the cylinder wall as those sharp edges will act like glow plugs causing premature detonation at higher RPMs and compression ratios if you are running crap gas. I religiously run 93 octane even though my compression is not crazy high. Not only can you go farther advanced on the ignition timing it also keeps all the crap from building up in your engine. You don't want your ECU throwing it into Briggs and Stratton mode all the time from the knock sensor going off .
Ps. Someone mentioned a 35+ shot of nitrous for low end torque??? Don't ever blow nitrous at low RPM and make sure it only blows at WOT. I would never use nitrous on something I plan on driving for a while. Save the nitrous for the rental cars![IMG]file:///C:/Users/Daniel/AppData/Local/Temp/msohtmlclip1/01/clip_image001.gif[/IMG]
I felt most of the info was sound so I decided to assist with the basic formatting.... In for dyno proof
HAPPY THANKSGIVING ALL
Last edited by DCZC; 11-25-2010 at 06:36 AM.
11-25-2010, 07:02 AM
#56
But thanks.)He might be wanting to call those efforts "hillbilly engineering", but I wouldn't mind having this guy as a neighbor. Pretty impressive.
11-26-2010, 10:18 AM
#59
I didn't. Not sure why you thought I did. 
Here's the story, end-2-end: http://forums.maxima.org/5th-generat...r-5-5-gen.html
I'm keeping the VIAS-delete mod. Because of the spacers (and maybe the crank pulley), I don't notice any low-end loss. And the power curve is so much smoother without the VIAS closing and opening.
Let's keep in mind that the VIAS-delete is high-end power, not low-end power, which was the original point of this thread. I was just reacting to Eirik's post about the BOP, is all. Sorry to derail, OP.
Here's the story, end-2-end: http://forums.maxima.org/5th-generat...r-5-5-gen.html
I'm keeping the VIAS-delete mod. Because of the spacers (and maybe the crank pulley), I don't notice any low-end loss. And the power curve is so much smoother without the VIAS closing and opening.
Let's keep in mind that the VIAS-delete is high-end power, not low-end power, which was the original point of this thread. I was just reacting to Eirik's post about the BOP, is all. Sorry to derail, OP.
Last edited by Rochester; 11-26-2010 at 12:09 PM.
11-26-2010, 01:58 PM
#65
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