A little off topic, but I think you guys have a lot better understanding of VQ engines than most, so I though I would post this here. I've done just about every available bolt-on available to me on my vq40 powered Frontier(6spd). These include-Brian Crower stage 2 cams, Uprev dyno tune, Headers, Magnaflow 2.25" duals w/ x-pipe, Magnaflow primary cats, secondary cats deleted, Volant CAI, intake manifold spacer, underdrive crank pulley, and a few other minor things. I'm putting out 269whp & 282 ftlbs. Turning about a 14 flat with a 4250lb racing weight.
The question is whether these numbers are about correct for a bolt on vq engine? The only significant difference between our engines is the obvious .5L bigger displacement created by a longer stroke. I also have slightly lower compression of 9.8. And my intake manifold is very different, has longer runners for torque I assume, and is a viarable intake with a butterfly that opens & closes at different points. Basically like the altima and maximas have Other than that, my engine is almost identical to a vq35.
I have been suspecting my vias operated funky intake may be holding me back. In fact I removed the vias butterfly from my intake and it bumped me from 260 to 269whp, though it did take away a little lowend torque.
So Since I see that changes in my intake do make a significant difference, I've been looking at other intakes. Mainly the vq35hr or vq37hr intake. I have the taller deck height, so I THINK these will bolt, but am still not sure yet. I also know the dual TB issue would be a tricky thing to get around. Might try to convert it to a single 70mm vs dual 60mm's, not sure on that yet though.
That issue aside, if I can get either of these intakes on, what do you think they would do for power?? I tend to think the results would be better HP, but possibly lower TQ. If I could gain HP, but keep the TQ even, that would be very cool.
Or am I just wasting my time here? is the 269/282 about all I can expect? Or do I maybe have a another 10-20hp hiding in the engine somewhere? Remember I'm talking bolt-ons. I would eventually like to go with 11.1 compression and ported heads and intake, but thats a couple years down the road. My power levels are pretty good I know. If my HP/TQ numbers were reversed, I would be at about the top of the bolt on cars here. But considering I have a .5L advantage shouldn't I be a little higher? Is my slightly lower compression hurting me that much? Or is it possibly my intake?
And I apologize for long post & going off topic a little here with VQ40 questions, but trying getting answers like this from Frontiers forums isn't helping. Those guys are just not into performance like I or most of you guys are.
Also here is my intake--

 

thats a tough call theres simply not enough reasearch done with your intake yes your what nissan calls power valve being removed will give you some top end power but the total volume of you intake is what may be holding you back you need to look into higher volume intakes and see what fits. thats just my .2 and the lower compression will also have a good bit to do with your over all power.

 

Thanks for the input. I have tried to buy HR intakes twice on this forum, and both times the sales fell through. I guess I might have to go to a salvage yard. If I can pickup the intakes(less TB)for $200 or so, I feel this is a worthy project to play with. If i can get the single TB converted intake to fit & work, i can always try to add the dual TB's down the road. I want to at least see if the HR intake will bolt before I deal with the dual TB issue.
Oh, also what type of gains in HP do you think going with from a 9.8 to 11.1 comp. would be?

 

Eh, from what I've seen, higher compression doesn't do much. My NA build (11.5:1), SG's NA build (~12:1), and so on have shown that the compression bump doesn't do anything. I think you'd need race gas to see ANYTHING significant, if at all.

 

Doesn't the vq40 use heads more similar to the DE. The last 2 letters are for the valve train. But anyway. I would look more into a DE intake and spacer or cosworth if they fit. Sounds like less work then trying to get 2 TBs to work.

 

When you say spacer, are you referring to a spacer between the lower intake and the heads? I know the vq35DE intake is much narrower than my vg40de intake. I think mine is appx 7" at the top and the vq35de is closer to 5.5" at the top. I had a member here measure his HR intake and he also says its appx 7". But until I can can get one in my hand I just cant tell whats up for sure. Of course none of the dealers keep them on hand. I also though my heads were basically the same as the HR head minus the exhaust VVT. I just have the intake VVT like the DE does.

 

Call speed force racing. Ask for Tim in regards to the intake manifold for the altima/maxima. Our manifold look very similar and also have the butterfly valve.

I dyno tested the manifold and gained 5whp over peak and 30whp at redline without a tune.

 

the deck height is like 9" on the VQ40... so the heads are further apart for the intake manifold so no lower intake manifold other than a custom one will work for VQ40 and use a 3.5 intake

 

Yeah, thats what I'm starting to find out. I guess the question is now is if there would still be any gains if I modified my lower intake or made a custom one to use a DE or HR intake? If I could gain maybe 10whp or so, I would say it would be worth it possibly. But is there that much HP hidden by my vq40 intake?

 

the problem with the VQ40 is recipricating mass... you should not be concerned about HP as you should concern of torque... HP= torque*RPM/5252... so if your not able to rev as much then you are going to be at a loss searching for HP... torque wins races... look at the audi R15 1500lbs/ft of torque... VQ40 is a great engine but not for reving... I would search for low end torque which will also give you gains in fuel economy!!!

 

The only catch to that thinking is the fact that my truck is quicker since I removed the VIAS butterfly(Variable Induction Air control System) from my intake. I gained power from 3800rpms through and past redline, usually 10-15whp, but a max peak of 9whp. I did however lose hp of 5-10whp and torque of 10-15ftlbs, down low in the 2000-3800rpms, but peak loss was in the 3000rpms range of 15whp & 25ftlbs. So I gave away low end torque but gained upper end horsepower. But my truck is faster. It feels faster for sure and track times show about 2 tenths better times and appx 2 mph better trap speeds since the VIAS was removed. Now putting around I can feel a very slight loss in the low end, but remember I still have 260-282ftlbs to the wheels from 2200-5500rpms, so its not hardly noticeable. What was noticeable, was that I pull very strong now from 4K all the way to 7K. My peak HP is at 6300rpms now. Up about 250rpms from my cam install peak and up about 500rpms from stock.
Anyway guys I do appreciate your opinions and input on this. It sounds like the HR intake will be too difficult to make work. So I guess I might try making a upper intake myself. Sort of in the direction of the kinetix intake design. If I do most of the fab work myself, I figure the worse thing is I'll be out a couple hundred bucks and some time if I don't see any gains and best case scenario is I'll have a cool looking intake that actually produces power. And I've read the debate on the HR thread about making intakes, but I still think there is room for improvement for my modded vq40 for the style driving I like. Remember Nissan designed my engine for towing and carrying things, so where I'm aiming isn't exactly what the engineers had in mind when they designed my intake.

 

I am still going to get you those pictures today. I was busy over the weekend and didnt have time to dig the parts out.

I would look into a FWD maxima intake setup and see if you can get that to work, its more like the RWD one and might be easier to adapt. The newer 07-08 altima one is plastic and might flow more than the older manifolds, but the older cast AL ones guys open them up and cut out the divider wall and see top end gains with them.

the 09+ Max one looks like the best FWD one though. You may be able to find one for a reasonable price though. just the upper would probably be needed.

 

too bad the FWD manifolds put the throttle body at the back of the engine and facing the wrong way... there isn't an 09 maxima... '10 maxima utilizes HR heads on a shortdeck block.... the ports on the manifold are huge and square so you would have to port match your lower intake to match it up but still then your intake manifold will be on backwards

 

Tim mightg be able to make some adjustments to the fwd manifold for the altima/maxima so it fits your frontier.

 

I guess i didnt type it all up outloud.... i was thinking of rotating the intake and putting the T/B on the other side. The ports are more squareish, but could still be similar.

I'm also just talking about the upper IM I know that no lower IM will bolt on, but it could be possible to modify the lower manifold for another upper to fit.

The only other thing I was thinking was a 02-08 maxima one, then the inlet pipe bolts on, and could possibly cut that and flip it maybe, pointing the T/B the right way on the right side?

I would not expect any of these to bolt on though, would take some work, but than again, it could still be worth it in the end... would just have to try.

 

if the TB was on the other side then the oil fill would be in the way... wiring harness wouldn't be a problem since it runs on the right side anyways, some cutting of tape and retaping would be needed... I am pretty sure the 07+ alitima IM and 10+ maxima IM also 09+murano would bolt on just there is alot of reconfiguring to make it work... might as well build a custom manifold that will clear everything and give you flow numbers that you need... not trying to rain on your parade its just trying to make a horse out of a donkey... just build a torque monster!!! by the way have you seen the size of a VQ40 rod??? gigantic to say the least

 

Add some nitrous.

 

I'm almost certain I'm going to make my own upper intake. The main purpose of this project is to try to eliminate the VIAS butterfly and the shelf it fits into that splits the body of the intake into lower and upper halves. It's been proven by removing the vias and removing the shelf both produce HP in the upper part of the rpm range. It has also been shown that the vias creates some losses down low and the shelf removal even creates more losses down low.
So the actual goal is to gain HP in the upper end, but no or minimal losses down low. I know that might be difficult to do and is why I intend to do as much of this as I can myself to keep costs down.
For any of you that want to make a stab at it. I intend to keep my runners pretty close to the same size, shape, and length as stock. Same thing on the main inlet pipe. So the intake body is where I intend to make the main changes. Right now the body of the intake is roughly 5" tall,4" wide, & 12" long. It is extra tall to allow for the shelf that separates the thing into a upper & lower section with each part feeding 3 cylinders. When you remove the vias, it creates appx a 3.5" hole in this shelf that allows airflow between the upper & lower sections.
So I am planing on making the intake body shorter, in the 3-3.5" range in height instead of the factory 5". Oh also as a note, my runners are appx 2.16" tall & 1.4" wide. They are sort of a rectangular oval shape. So if I make the body shorter, since I dont think its needed since I wont have a shelf, do I make the body wider to keep the body volume appx the same, or is it Ok to lower this volume some by keeping the width close to the original width of 4"? Do I need to keep the volume the same, keeping in mind I'm going from a split system into a single body system???
If anybody has any real knowledge in this area of expertise I would value your input.