Rb25det Vs. Neo - Why The Power Difference?

[frozenwaffles]

calculators you say...oh my!

[Al]

Are you all serious? Do you really think 5yrs of research and enhancements produce nothing.

Ash your 270rwkw was produced using a 600hp turbo, my 270rwkw using a GTRS (420hp turbo). So do cams and porting work?....... YES

Unfortunately I do not have unlimited funds to do dyno runs before and after each single mod, for the benifit of people I have never met. The porting was done by a very experienced person, that goes by his philosophy "more is not always best", and was far from a cheap exercise. But if you believe the STD cast head can not be improved, well time to re-evaluate you opinion.

Yes STD heads can flow the power, but how much bigger turbo do you need? How much more boost is required? How much torque is achieved? How are the graphs comparable?

[Lithium]

Are you all serious? Do you really think 5yrs of research and enhancements produce nothing.

Ash your 270rwkw was produced using a 600hp turbo, my 270rwkw using a GTRS (420hp turbo). So do cams and porting work?....... YES

Yes STD heads can flow the power, but how much bigger turbo do you need? How much more boost is required? How much torque is achieved? How are the graphs comparable?

You did look at the comments on GT2835s on a Neo and a R33 RB25? GT2835 is barely different to your GTRS. A bigger turbo doesn't magically tend to add more power on the same boost level unless the smaller one was becoming inefficient on the particular motor its on. At 270rwkw you are pretty much getting into "outflow the GTRS" type territory, as such you never know - with your bigger cams/"race porting" you could have been elevating exhaust pressure to the point the turbo was choking and causing reversion and your tune may have had to have been pulled back to make it safe, and a stock R33 head may have actually been better for you. If you were talking GT3582R and tried that on both your car and the R34 (and whoever did your "race porting" did a good) then maybe the results would have been vastly different.

Your results are at odds with a lot of stuff I have seen. The reason I asked if you got a before and after is not for our benefit, if I were going to invest the money in doing a whole pile of head work I'd seriously be trying to get a before and after comparison with no other changes to make sure it has worked as I had intended. Messing with the part which dictates how the whole setup works is a good way of making or breaking a setup, quite frankly I take "Years of research" etc etc with a grain of salt. It doesn't mean they didn't have a bunch of monkeys doing the R&D, spending lots of money doesn't necessarily make something work and having a head with big cams and flow numbers doesn't mean its going to work optimally with the other parts you have bolted up to it.

Edited March 10, 2009 by Lithium

[R31Nismoid]

Are you all serious? Do you really think 5yrs of research and enhancements produce nothing.

Ash your 270rwkw was produced using a 600hp turbo, my 270rwkw using a GTRS (420hp turbo). So do cams and porting work?....... YES

Unfortunately I do not have unlimited funds to do dyno runs before and after each single mod, for the benifit of people I have never met. The porting was done by a very experienced person, that goes by his philosophy "more is not always best", and was far from a cheap exercise. But if you believe the STD cast head can not be improved, well time to re-evaluate you opinion.

Yes STD heads can flow the power, but how much bigger turbo do you need? How much more boost is required? How much torque is achieved? How are the graphs comparable?

The changes were not made with performance in mind.

They were made for emissions as the driving force.

Hamish's example on the previous page is exactly what i would expect when you bring minor differences, in some cases differences that have no tangible benefit.

Everything can be improved, but that is not the argument here. The argument is to the point of is the NEO "that" much better, no its not.

A pound of boost or two would negate any 'major' change stock head vs stock head

[Peter]

Wow! Just logged on - thanks for all the information!

I'll print it out and digest it at work tommorrow - very interesting to read briefly - I didn't realise it was that complicated....

Thanks again,

Peter

[joeyjoejoejuniorshabadoo]

on the porting issue here... al's car made 270rwkw (reliable dyno's too) when most gtrs's run out of puff 20kw lower

[Mattw_83]

im no mechanic by a long shot, but wouldnt the cover on an r34 motor be a heat trap? Ive heard its better to remove it....

[Downforce]

Contrary to populart belief, Neo NVCS is also just on and off. NOT continuously variable. It just turns it on and off more than once through the rev range.

Neo has superior heads, slightly larger turbine for higher flow, different stock cams.

Also has different rods and crank but neither of these are performance adders, just reliability. Maybe lighter weight for better revving.

Neo also has an engine cover. It looks better.

I found my engine made more power with the VCT turned off with datalogit during tuning.

[bozodos]

I've been having a continuing argument with my best mate on his engine cover, I keep telling him it looks like it belongs on a holden V6 blargh!

Aren't standard NEO injectors also higher flowing than the RB25? And how many parts are common to both them and the RB26? I've heard that the block is the same, is there anything else?

[joeyjoejoejuniorshabadoo]

I found my engine made more power with the VCT turned off with datalogit during tuning.

weird... do you mean low down or top end? shouldn't it be off up the top anyway?

[sneakey pete]

Are you all serious? Do you really think 5yrs of research and enhancements produce nothing.

Well, its not going to produce a difference between the two, if your going to go and replace a lot of the externals with new aftermarket stuff that's had 10years of research and enhancement behind it.

To properly compare them, you really need to:

a) define what your comparing.

Are you comparing the two engines as they appeared stock in the 33gts-t and the 34gtt? Are you comparing their ability to cope with a bigger turbo? Or do you compare their overall power ability when the majority of external parts are replaced (all of the intake, things like cams etc.)

b) to do the latter, you need to go back and take a look at what is actually different about the block/internals and head. Judging by what people are saying (not seeing a difference with identically modified cars), i'd hazard a guess that the answer to this one is: not much.

So if anyone knows some technical specifications about the changes of the internals between the engines, could you please list them?

edit: spelling

Edited March 11, 2009 by sneakey pete

[Al]

Read the thread the differences have been listed and highlighted.

Ash I don't see how bigger cams, bigger intake valves, solid lifters, etc, are designed to meet emissions.

[benkoau]

what is datalogit ? what does it do

[TiTAN]

tuning software for the powerfc.

[joeyjoejoejuniorshabadoo]

plugs into pfc and your laptop... allows tuning

[R31Nismoid]

Read the thread the differences have been listed and highlighted.

Ash I don't see how bigger cams, bigger intake valves, solid lifters, etc, are designed to meet emissions.

bigger is one thing, majorly different is another.

They are bigger on paper, but its soooo marginal it doesnt matter.

Something that flows better, is more efficient. To get more power and still meet emissions this is what had to be done.

But at the end of it day, they are marginal changes that make little overall difference. Nissan attained 20kw or less from it, if it was 'so great' it would have been far more.

And when you compare stock turbo GT-t to GTS-t the difference again is only marginal, 10-15rwkw variance that is mainly attibuted to a larger turbo as opposed to the head.

Same turbos, stock heads (as shown before) result in virtually identical results. Comparing a heavily modified head raises questions about if it was done right etc etc.

Stock vs stock is the best comparison of the heads.

[gotRICE?]

bigger is one thing, majorly different is another.

They are bigger on paper, but its soooo marginal it doesnt matter.

Something that flows better, is more efficient. To get more power and still meet emissions this is what had to be done.

But at the end of it day, they are marginal changes that make little overall difference. Nissan attained 20kw or less from it, if it was 'so great' it would have been far more.

But then again, on "paper" they wouldnt want the GT-T making more power than the R34 GTR would they?

[R31Nismoid]

What does that have to do with anything?

[gotRICE?]

Well your saying that what they did flows better, so is more efficient to meet emissions laws, and also makes more power.

20wk from the tiny amount of difference your saying there is i feel is a pretty hefty increase isnt it?

All i was saying is that if they went too far then the car would make more power and on paper have more then the GTR lol.

[Al]

At the time the Japanese automotive industry had a "gentlemans agreement" not to exceed 206ps.

To date I am yet to see a STD r33 rb25 produce more than 270rwkw, using a HKS GTRS, on 3 independant dynos, like mine has done.