Rb20 Build Direction

[Spoolup]

Apart from the intitial purchase price difference in the RB20 to RB25, all other modification prices should be the same.

RB20's are a strong engine, no doubt. Anyone who drifts a stock engine is always pushing the engine design to its limits :-) and will come unstuck at some point in time.

" Will the RB25 make more grunt everywhere, yes. " is basically what I was saying from the start.

[andylaurel]

mind you it comes down to the history of the motor, my 2nd 20 was revving to 8000 rpm which is massive for a nissan motor.

my RB25 will probably fall over at 6000 with the tiny RB20 turbo on it!

[Roy]

But again, 230-240rwkws?

If you not happy waiting until 4,000rpm for your fun with the RB20 then go the 25.

But, i would buy a good RB25DET engine from a wrecker and slot that in. For that power level there is no way i would be building a motor.

[Josh]

Far out.. my 20 is running 20pound and is a daily... in 4th and 5th it runs some pretty stupid boost too... it runs rich as tho, 10.1 ratios throughout the range..... got me thinkin how long till she blows..

Edited September 23, 2006 by Josh

[RedDrifter]

i think old matey who started this thread was actually going to be doing internals? unless i read wrong...

I understand your point of view, but i have killed 2 RB20s with only a little drifting and i consider them weak.

lets agree to disagree

May I ask what it was that killed the motors in the end? (IE what did they die from?)

[boot_it]

im sorry but in my experience, the RB20 is a complete waste of time.

Short Stroke, no torque, small exhaust pulses...

its just not on... plus they are the weakest of all the RB engines.

If your going to look for a reliable 240 RWKW then go and get yourself a $900 RB25DE and start adding your fancy name brand parts...

an RB25 making 240 rwkw is a hell of a lot less scared and stressed than the equivilent RB20...

and if your on the coast, i know of a RB25DE (catch is its the 4wd model) for $750.

Heres a picture to prove my point...

doesnt take me long to kill 20's

thats because u starved the bottom end of oil constant hi rpm keeps the oil in the head causing the pic u posted

(esp as u are drifting)

ive made 280rwkw on my old rb20det it did it for over 3yrs and i abused the engine somthing shocking not just reving the ring out of her but only changin the oil every 20-30,000km running no coolant just water

ive rebuilt a fair few rb20 and 25 and im sorry to say it the 25 doesnt quite stack up to a rb20 (but im just another roy i love my rb20det over rb25s )

[boot_it]

because the rb20 has the weakest rods of the RB generation..

and the RB25DE is internally the same as the 25DET (save for the high comp pistons and oil squirters)

Do you understand that a turbocharger is just an artificial way of raising the compression of an engine? 10:1 compression on an RB25DE needs less boost to make the same power.

eg 1 bar boost on a factory turbo engine with 8:1 compression is effectively a 16:1 CR engine

whereas 0.6 bar boost on a 10:1 CR engine is effectively also 16:1 CR

another reason for choosing the RB25 is purely for displacement, as a 2.5 litre needs less boost and revs to make the same power as a 2.0 litre

what the u are jokin right

how can a shorter stroke rb20 corod (which is 3x thicker than a rb25 rod be weaker ) as they have the same grade metal in them

[legend01]

Rb 20 and rb26 rods spot the differance

[Spoolup]

please explain your theory on how the rb25 " doesnt quite stack up to a rb20 "

Is it the small ports and valves of the RB20 you like, or the 25% less cubic capacity

[Roy]

Sure its valves are smaller, they have to be the bore is a sh1t load smaller. Does the head flow as much, no way.

But compare it to say an SR20DET, sure the valves are smaller again, a function of the smaller bore, but based on the cc of each cylinder im betting the valve area is actually superior (Is it, i have never been bothered to work it out)

The RB20 bottom end is a good thing. And whilst its small bore and short stroke hurt it in the torque stakes. the small bore means a small, light pistons so its kind to its bottom end. It has bloody strong rods for a std car. Its bearings are basically the same size as its bigger RB brothers, and has lower piston speeds. So on paper the bottom end is damn strong.

So moving to the head and flow. They do not flow as well as an RB25. But put the same turbo on both engines and tell me that for the power figures that most of us chase there is a tangible difference over and above the fact that the RB25 enjoys a 500cc advantage and 0.5:1 in compression. If the head flowed that much worse an RB20 would not get near the figures the RB25 gets with the same turbo.

RB20 isnt as good, but it has advantages, and its disadvantages are as bad as ppl make out. The mods you do just have to play to its advantages.

Or you can go out and spend 10k on an engine that will smack everything....but it costs 10k Id rather spend 10k chasing se4xy back packers accross Europe