Mines R34 v HKS R33

[T0nyGTSt]

rb26 is 240/236 in/ex

rb25 is 240/240

256 to 260 is a good general setup

T.

[MarioGTR]

rb26 is 240/236 in/ex

rb25 is 240/240

256 to 260 is a good general setup

T.

This is just what Mine's quote them on their website as, which is incorrect. Infact, the R32 to R34 all had slightly different cam specs.

I seem to recall that the early R32 GTR's used more along the lines of 232/228.

Mario.

[lwells]

B. On a GTR don't touch the standard plenum, throttle bodies or inlet manifold.  I have yet to see anything that improves the standard system's response.  There is a strong argument for retaining the RB20/25 inlet as well.

SK: does that include the Greddy plenum? I would have thought having a plenum that doesn't force a major turn in the piping would create less turbulance?

LW.

[Sydneykid]

SK: does that include the Greddy plenum? I would have thought having a plenum that doesn't force a major turn in the piping would create less turbulance?

LW.

This is a much discussed topic, I suggest you do a search, "Sydneykid" and "Greddy Plenums".

As for camshafts, it is my understanding is that all GTR's have the same cam timing and lift, but the lobe separations are slightly different. Would make little difference to max power, but a bit to emmisions and fuel consumption. I have never actually measured them, so I could easily be mistaken (mislead), but I think the R34 GTR's have exhaust camshafts which are 3 (or so) degrees retarded in comparison to R32/33 GTR's.

I think the Tomei web site has all the specs of standard camshafts, if you want to confirm.

[lwells]

This is a much discussed topic, I suggest you do a search, "Sydneykid" and "Greddy Plenums"

Thanks SK, did a search and came across some great stuff. Excuse my ignorance but does the following on apply to the RB25, or does it also apply equally to the RB26:

The problem is the Trust plenum (like the GTR one in my personal experience example) has an 80 mm inlet. Running 63 mm pipework up to a 80 mm throttle body would disrupt the airlfow through the butterfly something fierce. So you have no real choice but to make the pipework from the intercooler to the plenum out of 80 mm diameter pipe. Particularly if the intercooler has an 80 mm outlet. It would no be good for airflow quality to go 80 mm out of the intercooler and then down to 63 mm pipe and then back up to 80 mm at the throttle body.

So what I did was use 63 mm alloy pipe from the turbo to the GTR intercooler, with a step up silicone joiner to the 80 mm intercooler inlet. I then used 80 mm pipe from the intercooler to the GTR plenum. The result was 0.5 litre more air in the pipework (not including the intercooler). I believe anything else would have made the response worse due to disturbed airflow.

On turbo inlet systems flow bench comparisons are a bit nebulous at best. A flow bench sucks up stream and measures the resistance to that suction. In a turbo engine the air is blown (boost) not sucked, so the results are quite different.

The guys I have asked about improved throttle response, all went from the "across the front of the engine and behind the radiator" type of pipework. Or the "across the back of the intercooler" type of pipewoprk.

We found a noticeable improvement by going to the 120 degree at the throttle body style, this eliminated considerable pipe length and 2 X 90 degree bends. Unfortunately I did not measure the difference in volume from that change.

To summarise (and get back on the point of this thread), on an engine with standard internals, I would rather change the pipework to the 120 degree bend at the throttle body than change the plenum to a front throttle body style. You get almost similar improvement in response (due to the lower volume of contained air) without the inherent dissadvantages of aftermarket plenums.

Cheers,

Lucien.

[Sydneykid]

Hi Lucien, if you look at a standard RB26 plenum and a Greddy RB25 plenum, there are noticeable differences, particularly at the rear (cyl 5 & 6). But the big difference is the RB26 inlet system has multiple throttle bodies after the plenum, equidistant from the inlet valves. Whereas the Geddy RB25 plenum has one throttle body before the plenum.

Hope that answered your question.

[lwells]

Hope that answered your question.

No, it doesn't, but that's my fault since I didn't make it clear what I meant What I was asking was would you recommend the same pipe work for an RB26 as you discussed above if I wanted to increase flow, decrease turbulence, and ultimately improve response?

Thanks for you time -- you are a true champ

Lucien.

[N/A®]

On the Mines Website, they claim 630PS from the R33 GTR using GT2530. 1/4 mile time of 10.6! whats the chances of that?

[Sydneykid]

No, it doesn't, but that's my fault since I didn't make it clear what I meant   What I was asking was would you recommend the same pipe work for an RB26 as you discussed above if I wanted to increase flow, decrease turbulence, and ultimately improve response?

Thanks for you time -- you are a true champ

Lucien.

Sorry Lucien, let's have another go.

If the RB26 is running a single turbo, then that's what I would use. If it is running twins, then you can't use the part of that design from the turbos to the intercooler. This is due to balancing, turbulence and back pressure issues. We use 50 or 55 mm pipework from each turbo, depending in the compressor outlet diameter. They then join to 80 mm pipework to the intercooler, with the collector configuration being very important in that layout.

Second time lucky?

[Sydneykid]

On the Mines Website, they claim 630PS from the R33 GTR using GT2530. 1/4 mile time of 10.6! whats the chances of that?

Hi N/A, which part of their statement is the problem? The 630 ps or the 10.61?

[browny]

Hi guys,

I was reading the discussion of rotational inertia of components with interest and whilst the concept of having lighter rotating components is valid - I was wanting to get an idea of the relative merits of the different ideas so I came up with the following calcs:

For a cylinder the rotational inertia is, I = m x r^2 <- note the r^2 term so this has a large dependance upon the location of the mass within the oblect.

So if we take assume a flywheel is a uniform circular disc of diameter 300mm (maybe inaccurate diameter? - I can revise):

"standard" 10kg - rotational inertia is 0.113 kg.m2

"lightened" 5kg - rotational inertia is 0.056 kg.m2

Reduction 0.057 kg.m2

Now obviously this isnt going to be completely accurate because flywheels arnt a uniform disc and the lightened flywheels often have more material removed from the outer edge because of the r^2 term but the whole idea of this analysis is to give a "feel" for the relative effect rather than definitive numbers.

Now we can model a tailshaft as a tube with OD 100mm and wall thickness 2mm (once again maybe not accurate dimensions but hey I can revise if someone tells me the something more correct):

"standard" 14kg - rotational inertia is 0.0013 kg.m2

"light" 8kg - rotational inertia is 0.0008 kg.m2

Reduction 0.0005 kg.m2

So now what if as an guesstimate, the flywheel represents say 15% of the total rotational inertia of the drivetrain.

The change by adding a light flywheel is therefore around an 8% reduction. The change by adding a light tailshaft is an 0.08% reduction, an effect of 100 times less.

Therefore the effect of a lightened tailshaft seems to be not much compared with say a lightened flywheel.

Comments please.

[Sydneykid]

Hi Browny, you are pretty much spot on with the comparison, the absolute numbers themselves are irrelevant. For a hollow cylinder you should use I=1/2M(B2+A2) to get a perfectly accurate result. But back to the topic.....

If you have a choice, do the flywheel. But if you have already done the flywheel, what next? Remembering that road wheels are actually my first choice, even before the flywheel. It is also worth noting that the 2 piece tailshaft (with universal joints, centre bearing and mounts) weighs substantially more than 14 kgs, I would reckon on around 30kgs. So if you relace it with a single piece carbon fibre tailshaft that weighs 6 kgs, that benefit is something like 50% of the flywheel benefit.

As an aside, now you know why F1 clutches (and flywheels) are <100 mm in diameter.

Good post, nice to see someone testing the theories.

[EnricoPalazzo]

hey gary, ill answer n/a's question.

is the 10.61 possible?

[lwells]

Sorry Lucien, let's have another go.

If the RB26 is running a single turbo, then that's what I would use.  If it is running twins, then you can't use the part of that design from the turbos to the intercooler.  This is due to balancing, turbulence and back pressure issues.  We use 50 or 55 mm pipework from each turbo, depending in the compressor outlet diameter.  They then join to 80 mm pipework to the intercooler, with the collector configuration being very important in that layout.

Second time lucky?

We have a winner Just further to that, would you use the same "path" as the factory piping, or do you change the angles/turns as per the RB25?

LW.

[browny]

sorry my formula was incorrect due to a typo - I = 1/2 x m x r^2

The calcs used the correct formula

Also, shouldnt that be I = 1/2 x m x (A^2 - B^2) ?