I'm interested in building an engine that can handle higher rev limits than the stock VQ. Shift points and RPMs become an issue on the roadcourse, where you often have to shift just before reaching a corner. Raising the rev limit can widen the powerband and eliminate this issue at the same time.

To this end, I did some analysis on piston speeds and acceleration for a variety of popular engines, as well as some variations of the VQ, including the AEBS bored/stroked 4.3L.

According to this analysis, raising the rev limit to 8000 RPM is very feasible on the stock motor, but becomes potentially dangerous on the 4.3L stroker (which is to be expected). On another interesting note, sleeving the block with ductile iron (for strength) and boring the cylinders to 100mm (same bore as the 4.3L stroker), yields a 3.8L VQ with the same rod/stroke ratio as the stock engine. Seems like a win-win combo to me.

Thoughts from other gearheads out there?

 

Note -- the attached file is a PDF within a zip file. The forum wouldn't let me post the PDF directly, and it wouldn't let me post a high-res screen capture either. It limits you to 640x480, which isn't enough resolution to read the numbers.

perhaps a kind soul would like to host the PDF file and provide a link?

 

Kiss your rods and rod bolts goodbye revving high for duration.

Ever seen a pic of one? Wait till you hold one in your hand, and realize that's ALL that is holding the motor together! Eeek!

 

no kidding.

although, I'm obviously not talking about the stock rods and rod bolts at 8K. I've seen/held several sets of rods. I haven't held the VQ rods in my hands, but the pictures are scary. Nissan did it in the name of lightening the rotating assembly, but wow.. I'd definitely trade a little more weight for some strength.

 

The VQ track cars are revving 8k+

Sunbelt Performance in ATL is making 380NA with a VQ motor... so it CAN be down.

 

what is sunbelt's set up, I went to their Website but its vq set up was not shown can they go global? Or mainstrem? or at least can i buy whats giving them 800 rpm's and 380 hp? Thanks

 

well.. anything's possible with enough cash..

I was just trying to do the analysis to see if it could be done on a street motor and still have reasonable expectations about engine life. The good news is, it looks VERY possible and not too harsh, assuming appropriate strength pistons and rods.

 

I'll Host it. Here you go.

http://home.comcast.net/~jeffr116/enginespecs.pdf



Jeff

 

Great minds think alike been working on the same thing, 3.8L with 8200 rpm and close to 400hp all NA. I have held the rods, and they are not as weak and spindly as people gripe, they are in fact pretty robust pieces and would hold up well I think for all but high hp applications. What is pathetic are the rod bolts, and according to Nissan are prone to tension failures above 7200 rpm. replacing these with some lightwieght, not particularly stronger, forged rods with studs would be ideal for higher revving NA goals. The RZZ heads flow more air than the stock pieces and bump compression, combined with lighter forged pistons that provide more ring land area and comped' for the ratio incease from the heads and all that reamins is breathing. Individual throttle boddies would give awesome response and allow a more open plenum design, and with a MAP sensor would eliminate the need for a single air inlet. Have two inlets feed opposite each other into a single open chamber plenum housing six bell shaped throttle inlets. With a dry sump system, the engine can sit lower allowing more chamber volum in the plenum and lower the Cg, helping reduce the overturning moment acting on the front suspension. The exhaust would be new as well, I don't think there is a system available that would be idealy tuned for the mass of air moving at such high rpm, much less the increased amount passable with the RZZ heads. Custom tuned headers and exhaust would complete the package. The tuning would be the key of course. The NISMO blanks are designed to run in conjunction with the RZZ heads and can be ground for the high lift and long duration to make this happen, but tuning the timing would take countless dyno pulls to vary it just right for idle and power, not to mention spark advance to co-incide. Sounds like a lot of fun if anyone has a lot of money
Side note, azrael- I'm guessing you live in Denver. Are you showing up at Second Creek this Saturday, the 11th. The Z Car Club of CO will be out there and I know some others besides my self are on this forum and will be racing. Just curious if you knew about it or not. It will certainly be a lot of fun, even to watch, and the more Z's the better. And how did you arrive at the piston speed and acceleration in regards to the effect of rotating mass, or was this independent based solely on the piston's position at TDC on the exhaust stroke?

 

Azrael- I've done some critical thinking on building a full-race GT2 VQ with high piston speeds and the first thing that becomes very apparent is that I simply cannot afford it.As most people know, Nissan Motorsports is now offering forged rod sets, revised race heads (with Ti valvetrain components) and cams. After paying for the design, fabrication and assembly work, this engine will have the potential for high piston speeds (8200 redline est) and produce top end power in the range of 380-395 HP.

BUT the two Nissan engine builders I've talked to estimate that building such a SCCA-legal GT2 motor will run between $20K (low-end) and 27K (high-end). Perhaps you can cut those costs substantially by doing all the work yourself, but we're talking high-level craftsmanship to make the VQ run properly. Building a stroker for street/fun is fine, but you'll still need better bottom end hardware and lighter valve train components to raise the RPM level safely. And did we even mention the costs of an engine management system to optimize running such an engine? As I said, it's too expensive for me to consider.

Since you're interested in road course applications, why not refine your driving skills to utilize more of the existing VQ's potential? We'll be planning some more Colorado Z track days for the fall and would welcome your participation again. As Resolute says, there will be several of us playing at SCR this weekend!

 

What about the Tomei crate engine, it can't be more than 10 grand! I hope its no a Forced induction set up, i hope it at least has a natrally aspirated option

 

Ok were talkin stock rods, New Bolts (arent they like 14 dollars a piece for bolts , maybe not) New pistons, heads and titanium blavetrain and cams,

retail:

Cams :$1500 (i would get the nismo spec 1
Pistons: can't be more than $1500
(but nonexistant for campatibility with the RZZ heads, no forged pistons have stock compression)

Heads:2k

Ti valvetrain : 800

6 grand for just parts

What about labor

Sound like its the same price as like a greddy tubo kit, with the same amount of reliablility.

I don't know if the stock crank is rated for such high rpms because the new nismo crank is supposed to be able to handle 8500 rpm (assuming we can't)

Plus this is without sleevin, and that means the rumored cylinder wear from forged pistons will be a factor. oh and the vtc pulleys are a might as well for around 300-600 bucks (forget)

is it worth it, might as well wpen a little bit more , get low compression pistons with this new head set up, and install a stillen or something, can it withstand the High RPM, wow

that would be sick

High RPM supercahrged VQ. WOW

I just found somehting. maybe turob would work better,t

then rods would definetly have to be changed, money would catch up again.

Greddy turbo, ( why its cheaper of course)

pauter rods,

that would be 7 grand more
7 plus five,

12 grand

but high rpm and turbo? Possible?

with two more grand you can sleve the block and get 3.8 liter and that sounds a n awful lot better than anything else out there,

but it would be 14 grand

without installation ahhhhhh!!! and you might as well get frekin AEBS with APS hahaha! back to square one.

Its like building a computer hahahah

 

In that case, i would get the FI then wait a while unitill i need new internals, and send the car away for a while getting its guts refurbished. With 8000 RPM monsterness. Just get a high capacity oil pan and nismo themostat and koyo radiator untill the internals can be changed.

 

I know the stock pistons will carry a lot of inertia but say we keep them, just change the rod bolts, then get the heads and calvetrain and vtc pulleys, intsall them and call it a day.

Then Tune?

no need for sleeving, and our stock pistons have a molybydenium coating , ( ala integra type R) very nice and not offered in the aftermarket.

So, that soulb run like 4 grand and you would have a high rpm high horsepoer 3.5 liter with enough power and high compresison , just tune it. but you will have to install all that. it might run you a couple grand just for install, and 6 grand total, still cheaper than Fi because they charge installation for that too.

But you haven't ruled out the Fi possiblility yet. You can awways get new pistons and rods and sleves and turbo.

 

Regarding the high-revving NA setup --

sounds like you have a lot of good ideas. Personally, I'm leaning towards FI. I simply wanted to do the analysis on the motor to see how it compared by design to other popular late-model engines. Ideally, I'd like to raise the rev limit to 7500-8000 RPM, sleeve the block, install forged rods and pistons with 9:1 static CR, and select a cam that will allow the engine to breathe up that high. Unfortunately, I'd take some loss down low, but that's acceptable to an extent. As far as the dry sump goes.. that's a great idea, but good luck fabbing custom mounts to lower the engine. Easier said than done.

Regarding the piston speed/accelleration --

In truth, I used equations that calculate velocity and accelleration with respect to crank angle, and then calculated for each degree in the full crank rotation. It was then as simple as selecting the maximum value. I wrote an Excel macro to do it. Unfortunately, it doesn't account for the mass of the rotating assembly, which definitely plays a factor in high-RPM operation.

Regarding the SCR track day, and upcoming events --

I might be there to watch, but I've got three problems:

1. Texas vs. Arkansas - I'm watching the game in the afternoon with my fellow ex-Longhorn buddies from work

2. I glazed my pads at the HPDE last fall, and I haven't had a chance to purchase pads that will hold up to track use. I have Hawk HPS pads now, and no interest in ruining those. I'm hoping to get a StopTech 13" front setup for next summer, depending on my finances. I really, really want to hit the road course again, but the stock brakes just don't hold up to the abuse at all. Eventually I'm looking to get the StopTech 13" setup on all four corners. Maybe I can get lucky and buy them used at a discount.

3. My tires feathered pretty badly (on a 2004 no less), and the inside edge of my front tires are worn almost smooth. The car is at the dealership now, and they're going to ask NNA for permission to do a "goodwill" front tire replacement.

 

I'm still interested in volunteering some of my time to assist in your race-car efforts. Sounds like you've thought about this a lot. My only question -- what do you get for that $20k? It seems like most competent builders could do the engine for about $10k, turn-key. The only huge unknowns are camshaft design, intake (ITBs possibly), and tuned headers/exhaust piping. I'm assuming that's what takes the remaining $10k+ ?

Given that my long-term goals are for a forced-induction setup, I wouldn't have to worry as much about the precise intake and exhaust tuning. Scavenging isn't quite as big a deal when you have air being forced into the cylinder at 10-15 psi.

As I mentioned in my response to Resolute, my car won't be seeing any track time this fall, which is very unfortunate. As you very correctly point out, my driving skills definitely need to improve before I spend a dollar on increased engine output. I just don't think the stock brakes are up to snuff. When I fix that issue (hopefully next summer), you better believe I'll be at every HPDE I can get to.

 

With Titaium Rods the package would definetly be complete. Then the engine would be really rev happy and could do 8000 rpm easily. Overall in favour of the 100 mm bore set up (provided by sleves) and 8000 rpms.

Rzz heads and titamim valvetrain and cams

 

pauter can make custom titanium rods for te VQ...I beliece they are $600-$800...each!

I agree with what some others have said. How about just going FI, installing forged rods and pistons, and bumping the rev limit to a reasonable 7100-7200rpm. Does that accomplish your goals for a road course?

 

If one was to upgrade the Cams, Pistons, Rods etc but left the stock crank in place, any ideas as to its RPM limits?

 

The stock crank "should" be strong enough, it is a forged piece, but who really knows right now. The only thing to know for sure is that it would need to be balanced, otherwise I wouldn't think it too weak for high rpm.