Rb27/ Rb28 Vs Staying Rb26

[ibrox90]

Might sound dumb and coming from na v8s it may not apply .

Surely it doesnt matter if boost starts at x rpm ... it the engine spins that hard?

I had a ford 5.4 lightened alot of the driveline and underdrove ancillaries.

And that used to just throw revs down. Surely a freely spinning driveline negates lag..

[GTSBoy]

There is a difference between boost threshold and lag.

I think you are arguing for negation of a low boost threshold on the basis that an engine that can rev could be kept in the rev range where it is making boost. Superficially, that would seem correct, but it is only true for certain usage scenarios. Circuit racers, drag and perhaps rally are the main examples.

In the real world, you will often find yourself in the wrong gear. Simply needing to make a quick lane change in traffic is a good example. A responsive setup that makes boost from lower revs simply has to make more sense in this situation. And in the rest of the real world, no-one wants to be spinning their engine away at 4500 rpm, using heaps more fuel and wearing it out faster if they could be a gear or 2 higher and using 2000 less revs. Drive any car with an instantaneous fuel consumption display and see the difference for yourself, even just holding a constant speed.

Then there is lag. The real, and only true definition of lag is "the delay before boost is produced when opening the throttle at an engine speed wherein the engine would have been making boost if the throttle had already been open and load applied". This is to be taken to mean explicitly what it says. Lag is when you are already above the boos threshold revs but are not yet asking for boost. When you open the throttle, whatever the delay before you get boost, that's lag. The impacts on drivability of this real lag are effectively the complete destruction of normal NA throttle response. When driving through a tight turn and opening the throttle, an NA engine will start to make all the torque it is able to make from the moment you start to open the throttle. A turbo engine will start to make its NA torque, and then boost will arrive and it will start to ramp the torque level up (either a little or a lot, depending on how much boost we're talking about). Read some old Porsche 911 turbo reviews from the late 70s to find out what the consequences of lag used to be!!

People using the term "lag" to describe what the boost threshold of an engine is is just lazy misuse of the term. It is basically equivalent to the horrible GenY/GenZ use of the word "verse" to describe a competition between two entities. Somebody starts using it, and everybody thinks it's correct and uses it too. But it's not. And it sucks.

[Nismo 3.2ish]

GTSBoy, understand that I am only asking a question and do not want to change the way my car drives well ?

When I bought my car it was aweful to drive under 5000rpm, does this mean that is how an N/A Skyline would drive or did it drive like that because of how the cams were dialled in for the bigger older T78 Turbo?

Blokes talk about strokers not being able to rev the way they like it, before I built my car I had read that Nitto 3.2 strokers go over 10,000rpm , no problem, well except for wearing the engine out more quickly, maybe dropping bits on the road.

I reckon with the extra torque I have now, I could put a different turbo on, like a PT7175 or EFR9180 that would still be drivable as a DD with 3.2Lt and the turbo would allow for much more top end power and would also kick in earlier compared to a 2.6Lt.

So if I wanted, I would have a car that would rev the same as a 26, more torque, more HP at the same revs and can drive it as a DD without changing down a gear when you come to a slope.

I have watched MANY vids of 26s on the track and love the way they sound up in the rev range and have only driven mine when it was a 26, no others, so my experience is practically ZERO and from what I have read the 26s can be sensational as a DD

[XGTRX]

In general turbo car will never drive like an NA car due to one main difference, the compression ratio. But then you have the diffence in head design, cam specs and exhaust design.

However similar limitations exist when chasing power, as in cam selection, and modifying the above mentioned will all compromise low end torque and will drastically compromise drivability on the street. All things being equal you can have a much better behaved FI car than an NA car with similar power levels.

[GTSBoy]

GTSBoy, understand that I am only asking a question and do not want to change the way my car drives well ?

When I bought my car it was aweful to drive under 5000rpm, does this mean that is how an N/A Skyline would drive or did it drive like that because of how the cams were dialled in for the bigger older T78 Turbo?

A 2.6L NA Skyline, especially a GTR with extra weight on board, would be an uninteresting thing to drive. Worse than a Camry. And that's for a completely normal NA engine. A turbo engine below the boost threshold has to deal with the lower compression ratio (as mentioned by XGTRX above) and the obstruction of the turbo in the inlet and exhaust tracts. There's a lot wrong with turbo engines when they don't have boost.

Logically, the best thing for any turbo engine is simply for it to be bigger. A good big turbo engine will always be better than a good small turbo engine. A classic example is when I converted my R32 from RB20 to a 25Neo. The RB20 is completely lacking in torque output unless it is on boost. The car is just slow before the turbo spins up. The 25Neo, even with only an extra 500cc or 25% of the RB20's capacity, makes a lot more torque when off boost and you can surf around the streets with smaller throttle openings and more urgent response to larger openings even before getting boost out of it. Logically, a 3L version would have to be even better. Logically then, a 3.2L version would be even better again. The only problem with chasing capacity is running up against the physical limits, whether they be mechanical or the breathing capacity of the head.

If I had a 3.2L big engine GTR like you I'd probably be happier to give up 500-1000rpm of boost response in order to obtain massive power - IF I was after massive power. The car would be nice to drive off boost anyway. BUT.....in general for a street car I'd probably not be looking for massive power so I'd probably stick with a more responsive setup so that I can transition from driving nicely off-boost to making enough power to run away from most challengers near on instantly, rather than waiting a bit longer for a stupidly large rush of power.

[XGTRX]

...... rather than waiting a bit longer for a stupidly large rush of power.

:D:D:D:D:D

[GTRPSI]

Its a simple thing, get cubes add boost.

Ive been in a LS turbo conversion, stock motor, stock compression with a big single conversion and supporting fuel mods, bejeusus, 500+Rwkw on a E85 tune, it had a lot more in it but no forgies to risk it.

And thats still pulling strong from the get go before the turbo even kicks in.

The only let down is the Commonwhore chassis...

[Anfanee]

Everyone is assuming the option is to go for gold in the power field.... Not everyone wants a 500+KW street driven car.

What if you don't want to go for 450+KW, what if you don't want a single?

What if you want 300kw, subtle, street driven machine?

For some circumstances it just isn't required. Like i have stated many times. Everything is relative. What power goals? Cost restrictions on the entire build? Feel of how it drives? Fitment issues (if going 3L), and even legalities (in some states)

Honestly after all the cars i have been in, anything over about the 350kw mark is just making power "because i can" you seriously can't use it on the street. Anyone that says they do is kidding themselves. I had 320KW and it was already overkill. But don't get me wrong, track car is a completely different ballpark. I'm merely commenting on a street basis.

also

Strokers sound shit

[XGTRX]

Its a simple thing, get cubes add boost.

Ive been in a LS turbo conversion, stock motor, stock compression with a big single conversion and supporting fuel mods, bejeusus, 500+Rwkw on a E85 tune, it had a lot more in it but no forgies to risk it.

And thats still pulling strong from the get go before the turbo even kicks in.

The only let down is the Commonwhore chassis...

And they still get ripped by a 350kw GTR because in street trim they are slow. I was looking at doing FI on my clubby and went for a drive in a few both SCed anf TCed and realised it was a fkn waste of time.

[Nismo 3.2ish]

All I can really say about these Skylines, is , I have come to luvem! luvem all

I have seen 2.6s, 2.8s, 3.0s and 3.2s with all sorts of build specs and think they are an amazing car.

Some of the builds I have followed have been sensational, some I am worried that I wont live long enough to see them finished, shit I was getting worried about mine still being in the shop when they were flushing my ashes down the brasco , lol

I think it comes down to this, build your car the way you want, listen to like minded people and learn from their experience, some people might not agree with what you are doing, but that is only their opinion and not worth shit, it is your car !

[XGTRX]

I think it comes down to this, build your car the way you want, listen to like minded people and learn from their experience, some people might not agree with what you are doing, but that is only their opinion and not worth shit, it is your car !

Better still is to drive/experience as many setups as you can and find what YOU like.

[Nismo 3.2ish]

Better still is to drive/experience as many setups as you can and find what YOU like.

Unfortunately easier said than done. Depends sometimes on where you live

I would imagine like many blokes, you buy the car first, sometimes because you like the look of them, believe the propaganda or just a spur of the moment thing, like I did !.

Out of all the cars I have bought, around 25 , this "was" the biggest disappointment and I have had some heaps of shit.

Whos fault, MINE ​ I did not do my homework

But now I am glad I bought it and lucky I used to have money in the bank

UP THE STROKERS

[GTRPSI]

And they still get ripped by a 350kw GTR because in street trim they are slow. I was looking at doing FI on my clubby and went for a drive in a few both SCed anf TCed and realised it was a fkn waste of time.

Because it couldn't lay the power down?

That seemed to be the only issue in the one i was in, till the owner fitted some ET Streets on it and sorted the suspension and stall converter.

I will comment that he mentioned i was the only one who didn't scare in the car, to me it felt slow too, it didn't impress me.

His drag slips said otherwise.

It was the way it laid the power down, totally different to the way we are use to in a GTR.....

[XGTRX]

Yeah unimpressive due to the linear power delivery, each to their own I suppose.

[mr skidz]

Yeah unimpressive due to the linear power delivery, each to their own I suppose.

maybe if your mate loaded up the engine to 4000 with his linear power then popped the clutch it would be more explosive for you?

[XGTRX]

They were all autos with hi stalls in them.

What's the point anyway. Bake the tires.... Wow.... Bring a sleeping bag next time

[mr skidz]

They were all autos with hi stalls in them.

What's the point anyway. Bake the tires.... Wow.... Bring a sleeping bag next time

when I said my car previously would not move until 5500 you said a thing of beauty, I was just suggesting that you simulate that thing of beauty by pumping the clutch nothing I would do just suggesting it for you since it sounds like you love lag

[XGTRX]

Ha ha ha.

You can't pretend to have lag. Not possible.

Its like pretending to still have a Gtr thoroughbred when you but a VL block in it.

:D:D:D

Edited September 1, 2015 by XGTRX

[Nismo 3.2ish]

You cannot call a car that wont go until you hit 5500 odd rpm , a street car. You cannot legally drive it anywhere on the street or highway and use it in that power range , to keep it going by the time you hit 2nd and ready for 3rd, it is time to hit the brakes ????

Having your neck snapped back when a turbo kicks in is really fun, well at first, but to drive around town in a thing "set up like that" is a nightmare. I KNOW THEY ARE ALL NOT SET UP LIKE THIS. I can only talk about what I have had experience in. As soon as you do something to make it more streetable the power becomes more linear.

I cannot believe your car is like that, you would have to kill yourself after a few weeks of this mental torture of knowing you should have the car in your garage, back of a truck or on the track.

The thing I like about linear power and it does not matter if it is 300kw or 500kw if your car is set up right, you can use it anywhere. You can drive it to the track and be very competitive , or have a street car that can be driven to church or Woolies and then go for a run and get the adrenalin pumping

The very best thing about it, I like mine this way

[QUP29]

ibomu hits full boost at 7,000rpm... Is it ideal for the street?

He drives it on the street?

And it's one of the most powerfulest gtr in the country.

Each to there own how they want there car setup.