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Discussion Starter #1 (Edited)
I am in the process of making the decisions on my build, I have found my self trying to make the decision between the short stroke of the rb26-27-28 and the long stroke of the OS Giken rb30-31-32.

Short stroke pros:

Fast responce from the RPM vs. right foot
Great top end and legs from you turbos


Short stroke cons:

Lack of VE @ botton/mid rpm
Slow responce from larger Turbos


Long stroke pros:

Good bottom VE and great mid VE
ability to light mid sized turbos from low/mid rpm

Long stroke cons:

Running out of breath @ the upper rpm.
Not willing to ramp rpms as quick as a short stroke.


this is just speculation as i have never run a long stroke motor, however it makes common sence. What do you guys think and what would you choose to run in your GTR and why?
 

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3.0L all the way!

I don't know who started the myth that OSG motors run out of breath at the upper rpm but its total BS unless the supporting mods are restricting airflow in some way and "not willing to ramp revs as quick as a short stroke" might seem correct in theory but in a the real world application my OSG revs just as violently as my 2.7 trackcar motor. The only difference being the 9000rpm limit on the RB30 compared to the 10000rpm on the 2.7.
If its a roadcar the increased torque and off boost driveability of the 3.0L TOTALLY hoses on all other options.:clap: :clap:
 

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Cossy already owns a 3.0 OS Giken, which is for sale at a bargain price
 

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canadian said:
thank you

if you were to buy a OS Giken today would you purchase the rb30,rb31,rb32
If I were doing it all again I would stick with the 3.0L until the larger OSG motors (IIRC a 3.4 conversion is forthcoming soon) have been installed in a few cars and any possible teething problems have been addressed. The RB30 is a known quantity whereas the RB31/32/34 are the new kids on the block..lol
 

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COSSYCam said:
If I were doing it all again I would stick with the 3.0L until the larger OSG motors (IIRC a 3.4 conversion is forthcoming soon) have been installed in a few cars and any possible teething problems have been addressed. The RB30 is a known quantity whereas the RB31/32/34 are the new kids on the block..lol
3.4? Does the car move, or does it just spin the earth under it?
 

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COSSYCam said:
If I were doing it all again I would stick with the 3.0L until the larger OSG motors (IIRC a 3.4 conversion is forthcoming soon) have been installed in a few cars and any possible teething problems have been addressed. The RB30 is a known quantity whereas the RB31/32/34 are the new kids on the block..lol
Do you know what the stroke and bore sizes are of those motors? Will they use a taller spacer plate of just use a shorter rod?

Interesting stuff!
 

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canadian said:
What do you guys think and what would you choose to run in your GTR and why?
Depends on what you want to set up the car for (e.g. Circuit, Street, Drag, etc.). Although the OSG setup is a ood option, its not the be all and end all of RBs (as you might occasionally conclude from reading posts on this board). Your other options are definitely worth considering.

Cya O!
 

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Depending on how much power you "really" want or need an OSG might not even be needed. Realisticly how much power do you want and what do you want to use the car for?
 

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manage13 said:
:eek: There is a 3.2ltr and a 3.4 on the way. Where can I read up more on this??
I'm just as intrigues as this. Very interesting.
 

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The whole stroke thing is really interesting, so I did a few computer simulations on my software dyno engine simulator to see what happens.

First observation is that, peak power is always limited by airflow through the cylinder head and induction system. So by just changing the stroke, peak maximum power does not vary much, but it DOES change.

Not surprisingly with a longer stroke, higher torque is developed and at lower Rpm. But you can do pretty much exactly the same thing by changing the diff ratio! It is just more leverage between developed piston pressure and the road. And you can do it at either the crank, gearbox, or diff.

But the most fascinating thing is that the cylinder head and induction system, if left exactly the same will always make more maximum power with a shorter stroke. Power always increases with improvements in breathing, but the short stroke engine is always ahead. The big disadvantage of doing this obviously, is the vastly increased mechanical stress imposed by higher Rpm.

So it really all comes down to your power goal, and what you might consider to be realistic Rpm. Stroking is never a good thing to do by itself, but it may be the lesser of two evils where very high power is desired.
 

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Stroke does not dictate how much torque you will make, it simply contributes to where peak torque is made due to the relationship between piston speed and gas flow velocities.

One importance of having short stroke is it can help accelerate engine RPM - the rate of horsepower delivery is better when comparing 2 engines of the same displacement and power.

One other important aspect I think is forgotten here is that stroke length may play 2nd fiddle to bore. As it is the bore size vs displacement that is the key to potential horsepower. Top race engines and performance engines have a high bore vs displacement ratio, Formula 1 v10's, Ferrari Enzo V12s, the 2 litre Honda F20C from the S2000, the S54 engine from the BMW M3 are fine examples. The RB26DETT is rather impressive with this as well. :p

If the design criterion is that the performance engine must be 3 litres, with 6 cylinders, you would want as much bore as possible for each cylinder - the more bore you can get - the less stroke you can have to meet the required displacement.
 

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Assuming the bore is kept constant, stroke most certainly does effect torque. It does so in two ways, the engine capacity has been increased, and the combustion pressure over the same piston crown area has a greater leverage on the crankshaft.

Big bore engines are better power producers simply because there is moe cylinder head surface area in which to fit the valves and ports. Hence, better breathing is possible than with a small bore long stroke engine of the same capacity.

Actually, total combined bore area is a fairly good indicator of the power potential of any engine, and total engine capacity is a fairly good indicator of torque potential (assuming normal aspiration or similar forced induction).

Where engine capacity is fixed by racing class rules, a multi cylinder short stroke engine is always first choice.
 

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Short stroke vs Long stroke

all depends on your preference, and how deep your pockets are.

If you want the best of both worlds, go with a 2,8 litre conversion. 3,0 conversion is a bit over the top unless you want BIG BIG horsepower.

plus rb26 was built to rev... personally i would keep it that way!

OSG 3.0 sure can rev up high but that is because it is strengthened to do so. You gonna pay a fortune for all that strengthening stuff that comes with it. Cost wise it just don't make sense unless you building a drag monster.
 

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Has anyone actually seen an OSG RB31, RB32 or RB34, seems there has been talk of them 'comming' for ever but I've never seen anyone say they have actually seen one or have one or know of one in a car.

Do OSG advertise them somewhere?

I'd love to see once and for all if all this talk of bigger cube RB's is true or all just specualtion.

Rob
 

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yep, sweet as, was sure the 31 wouldn't be a problem, its only 1mm extra throw on the crank and .25mm more bore, thats not too much of a major at all, what about these mysterious 32's and 34's or bigger?
 

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Bump......anyone know of anything bigger than RB32?
 
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