RB20 or RB25

[Ricer Assassian]

Hey whats up everybody. This is my first post here on the NICO forums. I want to get everyone's opinion on this subject. I want to do a swap, but I'm not sure which engine to get. I know someone is gonna tell me "it depends on what your aiming for". This is true but that doesn't matter right now. I just want to know the reason you choose your engine. Thanx

Ray

[bigk]

if price is no problem then go with the rb25 ,do to it being a bigger engine and more power.But the cheapest engine to get will be the rb20det,higher revs,but less power. still both are good engines. Also the rb25det transmission can handle more torque.

[Ricer Assassian]

i always thought the rb20 and rb25 had the same transmission. you learn something new everyday.

[Nameless EJ6]

I picked the RB25 because it seemed like it would make the amount of power that I was aiming for.. (350-400whp). At the time it was also in my price range so I went with it. The two biggest reasons I picked it are the transmission and the displacement.

However now that I see Mckinney has a mount kit for the RB26.. I might be changing my mind. The 26 has gobs of torque more than the RB25. So I'm at a stand still right now waiting untill I sell my civic before I decide.

[Ricer Assassian]

motor mounts for the rb26 is nice, but how would you get something that beasty inside a 240? you know with it being all wheel drive and stuff. would you have to make it just rear wheel drive and eliminate the front diff. or something?

[bigk]

you would use the rb25det transmission with a upgraded n/a 300zx clutch. mckinney motorsports has a kit that will be ready soon.

[Joe]

Quote »I know someone is gonna tell me "it depends on what your aiming for". This is true but that doesn't matter right now.[/quote]it always mattersif all you want is a fun little car to screw around with a rb20 is fine

if you are going for bigger numbers (400+) you should get a 25

and yes, to use a rb26 you need a rb25 transmission.

[PROJECTRB240SX]

if all you want is a fun little car to screw around with a rb20 is fineif you are going for bigger numbers (400+) you should get a 25

HOW CAN YOU SAY THAT? YOU CAN DO JUST AS MUCH WITH A 20 AS A 25. YOU CAN MAKE JUST AS MUCH POWER, MAKE WAY HIGHER REVS, FORCE JUST AS MUCH BOOST INTO IT, HAVE JUST AS STRONG OF A transmission, ETC.

YOUR CAR SHOULD BE DESIGNED WITH A PURPOSE, ALWAYS! IF YOU DON'T, YOU WILL NOT BE SATISFIED IN THE END. I CHOOSE MY PATH BECAUSE IT FITS MY BUDGET, IT WILL BE DESIGNED FOR ROAD COURSING, MAKES SUITABLE POWER, DOESN'T ALTER THE GEOMETRY OF THE CAR SIGNIFICANTLY, AND WAS EASILY OBTAINABLE.

RB20S AND 25S ARE GREAT MOTORS, YOU JUST NEED TO WAY THE OPTIONS AND CHOOSE WHAT RIGHT FOR YOU.

[frosted flakes]

I chose the rb20det because

1) It was cheap ($1400 for front r32 skyline clip)2) It is more powerful than a sr20det stock.3) It revs higher than most engines4) Its a 6 cyl5) How many people can say they have SKYLINE engines in their cars!!

[Ricer Assassian]

Thanx, everybody. this is all great. i guess my goals are to go 12's and maybe low 11's. i don't have much of a budget contrant right now just because i don't buy much or have to pay bills yet, but i do save some of my money for other stuff besides spending it to go fast.if the rb20 go do what i said above, then in this case cheaper is better. there is still one thing i think about whenever i think to get the rb20. in another post grumpy said that the rb20 is a waste of time. i know its only one person but it still flashes through my mind every once in a while. well anyway. the whole rb26 thing is cool, but i diffenitly don't have that kind of money or time so ill stick to dreaming and reading about it.

[PROJECTRB240SX]

WHO EVER SAYS AN RB20 IS A WASTE OF TIME IS A COMPLETE IDIOT. I'M SORRY I PURCHASED A RB20 FOR LESS THAN HALF YOUR RB25, INSTALLED IT FOR THE COST OF BASIC PARTS, WEIGHTS ABOUT 50LBS LIGHTER, AND WITH ALL THE MONEY I SAVED I CAN PUT IT TOWARDS POWER ADDERS. DOESN'T SOUND LIKE A WASTE TO ME.

[Wulfgang]

Well... I won't go sar far as to say an RB20 has as much potential as an RB25. Consider that someone who just turbo'd their KA could toast your stock RB20 at just 5 psi. And that's just a 2.4L with a 6500 rpm redline. The RB25 is a 2.5L with a bit higher redline than the KA. No comparison, really. The RB25 more than makes up for the lower redline with MUCH more displacement.

But... you can get the RB20 like I did because it was at least $1K cheaper than the next option (either SR or RB25 or turbo KA), and just tell yourself it was really because the RB20 was a "better" engine.

And there are consolation prizes for going the cheaper route, such as having a slightly less heavy car. Plus, the only thing that sounds cooler than an inline-6 at 7000 RPM is an inline-6 at 8000 RPM.

Shane

[PROJECTRB240SX]

MY ANSWER TO THAT IS 9.5 TO 1 COMPRESSION PISTONS AND THE PROBLEM IS SOLVED. IT WILL ADD ENOUGH HP TO MATCH A RB25, SPOOL QUICKER, REV HARDER, AND PRODUCE MORE BOOST EFFICIENTLY.

[WDRacing]

For the money I'd probably take the RB20. I had mine pushing 450 on a daily basis with all stock internals. I lowered my CR though. I couldn't get the stock pistons to hold over 28 psi. I also needed larger cams. I had swapped in the cams from the DE version since you pick up 8 degree's duration. But I needed atleast 256 cams to take advantage of the larger turbo and higher revs.

With a set of cams and forged pistons I would have been over 500whp.

All of the above was done with Alcohol and on my Skyline.

WD

[Ricer Assassian]

the more i read the more i lean towards rb20. so what about that whole weak transmission thing. you'll have to explain abit. i don't know import transmission's by there numbers and stuff.

[Yellow4g63]

For the money I'd probably take the RB20. I had mine pushing 450 on a daily basis with all stock internals. I lowered my CR though. I couldn't get the stock pistons to hold over 28 psi. I also needed larger cams. I had swapped in the cams from the DE version since you pick up 8 degree's duration. But I needed atleast 256 cams to take advantage of the larger turbo and higher revs.

With a set of cams and forged pistons I would have been over 500whp.

All of the above was done with Alcohol and on my Skyline.

WD

What kinda engine managment did you run? Haltech? or something?

[WDRacing]

Nope, stock ECU and MAF. I used a standalone Alky system for additional fuel. The rest was stock...

The RB20 transmission will run fine with a transmission cooler and some heavy wt fluid. If you want it to last forever, don't get a on/off clutch. Get somthing that allows you to feather.

[Ricer Assassian]

is it true that the rb20 transmission use the same flywheel and clutch as the sr and maxima?

[PROJECTRB240SX]

YES ALSO THE 300ZX NA Z32.

[wga240]

You guys are certain the RB20 uses the same clutch/flywheel combo as the sr,maxima, and NA z32? I may be looking for a new clutch soon and don't want to buy one that ends up not working

[PROJECTRB240SX]

I HAVE 300ZX CLUTCH ON MINE RIGHT NOW, SO DID SPEC-V, I HAVE SEEN PICTURES OF THE SR CLUTCH ON A RB20, AND THE MAXIMA IS ALMOST EXACTLY THE SAME AS THE 300ZX CLUTCH.

[Yellow4g63]

Nope, stock ECU and MAF. I used a standalone Alky system for additional fuel. The rest was stock...

The RB20 transmission will run fine with a transmission cooler and some heavy wt fluid. If you want it to last forever, don't get a on/off clutch. Get somthing that allows you to feather.

good info. Know of any sights that have cams listed for the RB20? the HKS sight only list 264's I'm looking for 272's. I want to mix it with a 264/272 combo if can.

[WDRacing]

Check out the Australian sites, go through http://www.skylinesdownunder.com they should be able to hook you up. I learned a ton through them.

WD

[PROJECTRB240SX]

http://www.tomei-p.co.jp/_2003....html

THIS HAS ALL THEIR CAMS AT GREAT PRICES.

[Joe]

HOW CAN YOU SAY THAT? YOU CAN DO JUST AS MUCH WITH A 20 AS A 25. YOU CAN MAKE JUST AS MUCH POWER, MAKE WAY HIGHER REVS, FORCE JUST AS MUCH BOOST INTO IT, HAVE JUST AS STRONG OF A transmission, ETC.

YOUR CAR SHOULD BE DESIGNED WITH A PURPOSE, ALWAYS! IF YOU DON'T, YOU WILL NOT BE SATISFIED IN THE END. I CHOOSE MY PATH BECAUSE IT FITS MY BUDGET, IT WILL BE DESIGNED FOR ROAD COURSING, MAKES SUITABLE POWER, DOESN'T ALTER THE GEOMETRY OF THE CAR SIGNIFICANTLY, AND WAS EASILY OBTAINABLE.

RB20S AND 25S ARE GREAT MOTORS, YOU JUST NEED TO WAY THE OPTIONS AND CHOOSE WHAT RIGHT FOR YOU.

revs dont make power, if you have a motor that revs to 10,000 rpm but only makes power to 7000 its a waste of 3000 rpms. the rb 20 transmission is PROVEN to be weak if you want 400whp you HAVE to upgrade. have you priced a 25 transmission? anywhere from 1300-2000$ that ALONE is almost the price diffrence between the RB20 and 25 clips.

i never said the RB20 was a bad engine but you have to realize what you are buying, an engine that is at the very LEAST 12 years old. its been sitting in a junkyard for god knows how long. if you are going for serious power you have to drop a realistic 1500$ on just a transmission.

[Yellow4g63]

From what I understand the Rb20 transmission is almost the same as the SR20DET transmission just a little bit stronger. There are more than a few of the 400+hp SR's running the stock transmission and it's holding up. I'm sure if you Power shift it like a honda transmission it won't last.