Question I've long since pondered. Is it the architecture of the engine? Head design? Cam profiles? Tuning ability? Lack of air flow? What exactly makes it so much less desirable to mod without going FI than an HR? Excuse my ignorance on the subject but I've never seen the question posed like this before.

 

From my understanding. The de is pretty much max tuned from the factory so it doesnt really react well to mods. The hr can handle much more power than the de. Overall the hr is just a better building block than the de. Reacts to mods better and can handle i believ 5-550 whp vs de 400whp "safe" power band. Hr also revs higher.

 

The VQ35DE and VQ35HR are best considered as two different engine designs. This is best illustrated by the fact that 80% of the HR's internal engine parts are different than the DE. It has more in common with the succeeding VQ37VHR (as used in the G37 and 370Z) than the DE engine design.

Both engines were well tuned from the factory, but the HR has the advantage of better breathing and a higher rev limit. Cam profile is different, and it makes slightly more power at the top end. Neither engine was designed for FI from the factory, but both can be adapted on a limited (durability) basis. Having owned both types of engines in a Z, I like both designs and think the HR "superiority" is more myth than fact.

 

So if I'm reading this correctly it's breathing that seems to be a limiting factor in which cams play a role in. Explains all of the 3" intake threads I've seen.

 

the hr has bigger connecting rods than a de. and has a lower compression ratio than de (10.5:1 hr 11.0:1 de but correct me if im wrong.)

 

With the addition of the second throttle body/intake on the HR I think we can assume it is certainly going through more air.

 

Stuff I've seen has the compression ratio on the DE at 10.3:1.

Agreed on the second intake. That was kind of a given. I just didn't know if that was the only difference that made it better or if there was more to it but it seems that it's mainly breathing, cams, and compression.

 

Hr- 11:1
de- 10.3:1

 

Stock for stock, the HR is engineered better, the engine doesn't tear it self to pieces to give you 7k rpm. The DE has higher intake velocity which leads to greater plenum turbulence and subsequently less efficient intake cycle. If both were setup for FI, the HR would deliver more consistent numbers, better throttle response and higher peak HP. Some people claim you can modify the DE enough to get over some of its engineering deficiencies but the claims are all fairy tails. People will say anything to defend their investment. I have a completely unmolested stock 06 6MT, I know for sure the engine isn't as peppy as an HR. Its my reliable daily driver that I probably will never mod (I don't even have a CAI).

-------------------
06 6MT 350Z
08 WRX STI
11 BMW X3

 

You are the first person I've ever seen that said high intake velocities are a bad thing.

Just how is the hr engineered better? Not being an ***, asking legitimately.

 

Faster moving fluids is not always a good thing, in fact it rarely is. When a fluid moves with greater velocity a few things happen:

1. The pressure reduces
2. The potential energy of the fluid reduces
3. The resistance caused by surface curvature anomalies disproportionally increases with fluid velocity

This leads to significantly increased tolerance requirements for carefully crafted piping, routing and porting. It becomes more difficult strategically direct fluid flow, creating excessive turbulence in manifolds. Turbulence only serves to exaggerate the existing fluid flow problems. Its a very well understood problem for process engineers (look it up). The principle applies to the automotive world as well, its the same problem just different application. The bottom line, the HR has a significantly better plenum design which reduces intake velocity resulting in a better combustion cycle and compression level. The engineers at Nissan didn't change the engine design just because they got bored, the old setup was very inefficient.

 

Old subject. Hotly debated by many. I have owned both a 2006 (Rev-up DE) and a 2007 (HR) 350z. I still have the 2007 and it's a beast.

There was a internal PowerPoint deck being circulated that someone lifted from Nissan Marketing/engineering that extolled the improvement in the HR (Update: Attached below).

The real difference is about 40 Horsepower near the top end that the HR can produce over the rev-up DE. Nissan cheated with the 300 HP rating for the 2006 z. In 2007 they were required to use SAE ratings so they had to redesign the entire engine so that the vulnerable z would not show a reduction in power for 2007.

The 2006 engine had some critical flaws in it - for one, the intake manifold had to fit under that sloping hood so they had to thin out the intake manifold air chamber at the front. This caused air-starvation to the front two cylinders. The HR engine deck is taller and the hood was raised to accommodate the new engine. The second problem with the DE was heat management. The heads would run too hot and cause the engine to ping madly even with premium Chevron gas (California 91 Octane). THe new engine has twin knock sensors, but the return hot coolant now flows externally from the rear of the block back to the Radiator.

The HR engine has longer connecting rods and asymmetrical piston skirts the list goes on... let me see of I can figure out how to post a pdf document here... If not, send me your email and I'll email it to you.

Here is a dyno with my 2006 and 2007. The 2006 had the Motordyne plenum spacer and throttle body coolant bypass on it. and the 2007 is still up 40 HP at the top end.

I am putting down 301 WHP in the HR now. Mods are in my signature. The DE folks that ride in it swear it feels like forced induction. It MOVES!

Hope that helps.





Here's my final Dyno. After tuning which was the last step. Still loving this car.

 

And there it is, this discussion is pretty much over.

Thanks,

 

When I got my HR equipped Z33 Niz, I discussed the "driving differences" between my '03 DE and '08 HR cars ad nauseum here: https://my350z.com/forum/2003-2009-n...omparison.html

Got really curious to know exactly what made the two so different and looked deeper into it beyond what I ruminated in the linked post.

Everyone is right here. But just to summarize what everyone has pretty much already stated (cuz I like bullet points ) :

The DE and HR are pretty much different engines, the HR being an evolution of the DE incorporating the following changes:

1. Displacement is identical (bore and stroke retained) but...

2. All new block is taller by some 8mm (adding strength) and the con-rods were lengthened and pistons made shorter - to maintain bore and stroke dimensions but new configuration reduces the incidence of piston slap aiding in higher rev limit.

3. Lighter but stronger rotating assembly through use of improved (larger) crank journals and bearings utilizing a new ladder reinforcement design (that's racing shid) of the main bearing structure (caps and saddles). I believe I read that this was the result of the JDM racing efforts by Nismo in the S1 competition engines. Could be wrong about origin but suffice that it's much stronger and mo' bettuh.

4. Much improved intake design - dual path, dual inlet, dual MAF (with corresponding software to process a new input) new intake manifold design, re-located cam sensor (dubious if this improved anything though)

5. Valve timing much improved (something not yet mentioned here I don't think) - the HR added variable valve timing on the exhaust side whereas DE only had such on intake side.

6. Exhaust manifolds were improved through equalizing the exhaust path and the exhaust system aft of the manifolds was also improved for better flow (to keep up with the enhanced breathing on the front end (intake) side of things.

7. Compression ratio increased by .3 (DE: 10.3:1, HR 10.6:1)

Essentially, the HR is the evolved DE using time honored hot rodder tricks.

Which is better? Welllllll, not gonna open that can of worms. As David stated previously, the "superiority" of the HR is something of a myth as both are great engines. One is just newer and the recipient of "newer technology" so it "should" be the better engine, right?

As far as which responds to mods such as FI better, well, it stands to reason that the stronger basis of the HR SHOULD but can't really say. I'd venture that the HR is already a pretty maximized design as it is and adequate for most. But that's IMO only.

Mic

 

Might want to double check your numbers fellas.

10.3:1 for the DE
10.6:1 for the HR

 

What I find amusing is that I lived through the era of 8.5:1 being state of the state (no forced induction even) and the guys running 10+:1 were the nuts, er, kings of the street. Heh heh.

Even our "built" street Chevy mouse motors never went much above 9.5:1.

Thank you, microelectronics.

 

Cool. Thanks for the info.

 

Sorry the VHR is 11:1. My bad