Ultimate Na Rb20

[Chris-06R]

Ok, this is a hypothetical... at this stage.

I've been dreaming of building an RB20 for use in Under 2L Improved Production Racing, just because it would be something different to the swarms of 4Cyl Vtecs and what not running in the series, plus I'd love to hear something like this at the track -

I know Screamin has done a similar thing with his R32 GTS rally car in NZ, and the fact that he reckons his car is pretty competitive makes me want to do it even more.

So my question is this - what would you do to make the ultimate RB20DE, keeping in mind you can't turbo it, and you must keep it the same capacity. Head is free as are most other components.

Some of the things I have considered and would like to see discussed include:

- Higher compression running on E85 (how high can you go?)

- ITB setup similar to Screamin's (see http://www.skylinesaustralia.com/forums/Rb...d-t222993.html)

- Solid lifters to make it rev (to what redline?)

- Upgraded springs, larger valves?

- Cams, Port and Polish etc... (what specs?)

- Oiling mods

- lighter/stronger pistons/rods (would they be needed considering DETs can put out 250kw+ in stock form?)

- Anything else

And finally, how much power do you think it would make, is it worth it, or should I stop dreaming and move on...

[GTR-32U]

Sounds good but its gonna cost dollars to wring power out of the RB20. But I would be going no less than 12.1 comp on e85....Maybe closer to 14.1. The head is where its going to cost big dollars, as well as the forged pistons. Look into a 6 throttle inlet, maybe a bored out GTR version, Huge cams , ems etc....keep us posted

[KezR33]

Just curious, but why not go for an SR20? Aren't they lighter and similarly powered? An Autech SR20DE would be a nice starting point.

[Galois]

Maybe closer to 14.1

whoa, that's big

Just curious, but why not go for an SR20? Aren't they lighter and similarly powered? An Autech SR20DE would be a nice starting point.

im guessing he's gonna say because 6 cylinders would be interesting vs all those 4 cyl engines. the problem is having the same capacity and increasing the no. of cylinders loses torque. straight 6 sounds better tho lol

im guessing you'll want vct as well, and maybe go for the neo head as a slightly better starting point. might be worth looking through this thread too

http://www.skylinesaustralia.com/forums/20...le-t317633.html

whatever you do, it's going to be expensive.

[iseekool]

whoa, that's big

im guessing he's gonna say because 6 cylinders would be interesting vs all those 4 cyl engines. the problem is having the same capacity and increasing the no. of cylinders loses torque. straight 6 sounds better tho lol

im guessing you'll want vct as well, and maybe go for the neo head as a slightly better starting point. might be worth looking through this thread too

http://www.skylinesaustralia.com/forums/20...le-t317633.html

whatever you do, it's going to be expensive.

You will not be losing or really gaining torque with more cylinders, you will get more torque earlier in the rev range and will be much more linear as the cylinder firing will be more frequent. 8 cylinder will have a power stroke every 45 degrees, 6 cylinder every 60 degrees and a 4 cylinder every 90 degrees.

In theory the more cylinders you have, the higher you can rev it smoothly - but you will then have to start factoring power lost to friction etc. - obviously more cylinders/moving parts = more friction. So there needs to be a balance between engine capacity and number of cylinders.

Then there are other things to consider such as bore-to-stroke ratio. Longer stroke = more torque at low RPM but risk harmonic resonance at high RPMs causing highly stressed or broken cranks. Bigger bore = less torque at low RPMs but can rev higher with the risk of harmonic resonance.

Another thing to consider is each cylinders capacity. eg. an SR20 will have a larger cylinder capacity to an RB20 (total engine capacity divided by number of cylinders).

There are alot of things to consider.

Since this is an n/a application and if you do not want to run any vvt or anything like that - the RB20 will still have more potential compared to an SR20 engine. The key to more power from a small engine is revs. (nothing against the SR20 - I don't want to start an SR20 vs RB20 war).

Reasons:

- 6 cylinder = smoother revs = more potential to rev it higher.

- short stroke design = allows for free reving.

[Rowdy]

i would probably start by putting a turb- dang! stuffed it up already

[Chris-06R]

Just curious, but why not go for an SR20? Aren't they lighter and similarly powered? An Autech SR20DE would be a nice starting point.

im guessing he's gonna say because 6 cylinders would be interesting vs all those 4 cyl engines.... straight 6 sounds better tho lol

^^^ on the money. Does anyone definitively know the weight difference between an sr20de and an rb20de? Some googling tells me theres around 40-50kg difference, but its hard to find a definite answer.

I'm also struggling to find anyone who bothered putting in any effort to make the RB reach its full potential. Surely you could make it rev harder than the SR and make up the difference?

i would probably start by putting a turb- dang! stuffed it up already

LOL

and maybe go for the neo head as a slightly better starting point

Do you mean the R34 rb20 neo? These would be very hard to get in oz I would assume, as no rb20 r34s made it here (correct?). What's the difference and is it worth the hassle?

[ONE-VIA]

sr20ve

fj20 or fj24...

[zebra]

I would sacrifice 10hp to save 50kgs by going SR20, plus good ITB setups are avaliable off the shelf to suit.

40-50kgs is a bit lump to have hanging over the front axle line.

[mad082]

+1 for sr20ve. even in stock form it's got anywhere from 24 to 37kw more than the rb20, depending on which version of the VE you get. that is a noticable power difference, especially if you then also take into account that the engine is lighter. there are plenty of people getting 150kw at the wheels out of these engines with relatively mild mods.

[XRATED]

Hmmm I'd love to see somone have a good crack at an NA rb20.

Good lightweight bottomend, short skirt high comp pistons etc... try and minimalise weight and friction.

Well developed head that all works together.... right shape ports for the valves and tb's, correctly tuned ram tubes/cams/exhaust.

If you want to get serious with CR, look at methanol-

The key to a good engine like this is the builder... Good NA builders are getting hard to find, especially anyone who will play with an import 6 cyl eg. non V8.

[ONE-VIA]

theres no limit to what you can do to your car/engine

the only limit is moneys

[Chris-06R]

^^^ The only limit is moneys... and rules.

IPRA rules say that you must run pump fuel, so e85 is as good as you're going to be allowed to use. No methanol.

And yes, SR20VE may be a better motor, but I wasn't asking for people to name better motors than the RB20. I could have done that myself.

So back to the original question - what would you do to make the rb20 as good as it could be? Does anyone know of any serious NA rb20s around?

Its good to see the support of a few people saying someone should have a go at it - maybe thats evidence that few have tried (or is it that those who have tried failed miserably? )

[Rowdy]

have a crack and if its an epic fail, go with my earlier suggestion

[Galois]

yeah mate im really keen to see how this turns out. there's nothing as interesting as people doing things differently, and you have a real reason to stick to 2L and non-turbo. i, and many others im sure, love to read about how much people can do to engines to get what they want out of them.

hope it works out. id like to get into some sort of series like that one day, when time and mulah permit (uni student lol)

[R33_Dude]

Okay so heres what I would do just on the engine side of things:

Induction:

Independent throttle bodies. I would be looking at 48mm. Should support well over what a N/A RB20 could possibly make while maintaining perfect throttle response. Adapt 20V 4AGE ones or if you were really keen buy a set of slide throttle bodies as used on V8 super cars (cost a mint). Secondary injectors mounted over trumpets for WOT.

Laser cut aluminum manifold. Needs carefully designed runners for optimum torque/horsepower. (I could design this for you if you wanted and get it cut.)

Trumpets, filters, carbon fiber/aluminum box surround (heat soak reasons) with large bore piping to fresh air, preferably polished alloy. Concept is more available cold air than the car can suck in.

Head:

NEO RB20DE. Ported by a real professional. Could be hard to find.

1 or 2mm over sized titanium valves. Depends on porters recommendation. Won't try and second guess the Black Art of race head porting.

All the most lightweight (i.e. expensive) gear you can get your hands on.

Cams that bump peak power and torque to something approaching 7000 rpm.

Block/bottom end:

NEO block. Crack tested and fully inspected as a matter of course.

CP forged pistons (any compression ratio you want), balanced to 0.001 grams. Really anal retentive. 12.5:1 comp ratio is nice on E85 from what I have seen.

Forged conrods, possibly Eagle. Lightened/balanced to within 0.001 gram. Carefully match to each piston to cancel out any minor differences in weight beyond this. Will need super sensitive scales.

Exhaust:

Long runner exhaust manifold. Will look like a basket of snakes.

On top of all that expense add better gaskets, custom engine mounts (lower, farther back to cancel out weight and improve handling), race bearings, possibly a dry sump setup if your lethally serious, water pump, oil pump, belts and lots more cash plus hours upon hours of tuning.

I don't doubt its possible. It would just be so restrictively expensive I would just wander over to the honda camp and buy an integra VTi-R.

Edited May 5, 2010 by R33_Dude

[iseekool]

Okay so heres what I would do just on the engine side of things:

Induction:

Independent throttle bodies. I would be looking at 48mm. Should support well over what a N/A RB20 could possibly make while maintaining perfect throttle response. Adapt 20V 4AGE ones or if you were really keen buy a set of slide throttle bodies as used on V8 super cars (cost a mint). Secondary injectors mounted over trumpets for WOT.

Laser cut aluminum manifold. Needs carefully designed runners for optimum torque/horsepower. (I could design this for you if you wanted and get it cut.)

Trumpets, filters, carbon fiber/aluminum box surround (heat soak reasons) with large bore piping to fresh air, preferably polished alloy. Concept is more available cold air than the car can suck in.

Head:

NEO RB20DE. Ported by a real professional. Could be hard to find.

1 or 2mm over sized titanium valves. Depends on porters recommendation. Won't try and second guess the Black Art of race head porting.

All the most lightweight (i.e. expensive) gear you can get your hands on.

Cams that bump peak power and torque to something approaching 7000 rpm.

Block/bottom end:

NEO block. Crack tested and fully inspected as a matter of course.

CP forged pistons (any compression ratio you want), balanced to 0.001 grams. Really anal retentive. 12.5:1 comp ratio is nice on E85 from what I have seen.

Forged conrods, possibly Eagle. Lightened/balanced to within 0.001 gram. Carefully match to each piston to cancel out any minor differences in weight beyond this. Will need super sensitive scales.

Exhaust:

Long runner exhaust manifold. Will look like a basket of snakes.

On top of all that expense add better gaskets, custom engine mounts (lower, farther back to cancel out weight and improve handling), race bearings, possibly a dry sump setup if your lethally serious, water pump, oil pump, belts and lots more cash plus hours upon hours of tuning.

I don't doubt its possible. It would just be so restrictively expensive I would just wander over to the honda camp and buy an integra VTi-R.

^ 2L NEO (from R34) engine would definately be something different. They can be found on eBay for a bargain.

But on the thought of enlarging valves (head work) etc. wouldn't it be more cheaper/easier to just go for an RB25 NEO head or even an RB26 head - as these heads would have already been ported to the right specs out of the factory... Just a thought.

[mad082]

the rb26 head would also allow you to run the rb26 ITB setup. not sure how that would go for this setup though

[zebra]

25/26 head wont fit. the chambers/valves are too big...also the size of the ports would be way to big and you have have to rev the motor to 10,000+ to make any power.

Dont use titanium valves unless you plan on replacing them after every meet.

Why not just turbo it and live with the 36mm restrictor? You would make around 300hp so at least 60 more than what an NA rb20 would make without 100,000 bucks poured into it.

Still run 10:1 comp and E85 just add a GT-RS turbo and run as much boost as you can.

I love doing things differently too.....but if being different meant trundling around at the rear of the field with no chance of being up the front, then i'll just stick with whats proven to work and win races.

[mad082]

25/26 head wont fit. the chambers/valves are too big...also the size of the ports would be way to big and you have have to rev the motor to 10,000+ to make any power.

Dont use titanium valves unless you plan on replacing them after every meet.

Why not just turbo it and live with the 36mm restrictor? You would make around 300hp so at least 60 more than what an NA rb20 would make without 100,000 bucks poured into it.

Still run 10:1 comp and E85 just add a GT-RS turbo and run as much boost as you can.

I love doing things differently too.....but if being different meant trundling around at the rear of the field with no chance of being up the front, then i'll just stick with whats proven to work and win races.

i'd be more inclined to say more around the figure of 100hp more than what a worked rb20 would make. i think that even getting to 200hp in a rb20 would take a fair bit. not saying it couldn't be done, but it would be a fair bit of work (and money) getting there judging by how much it takes to get a rb25 there.

and look i'm all for doing something different, but when it comes to building an engine to go into a race car, why bother building something when there are other options out there that will do the job better? going something like a sr20ve would give you 20 to 30% more power, and a less weight. we aren't just talking about building something to be different to show off to people with. we are talking about something to win races with, so why not give yourself a good platform to start with, especially when you are talking about a motor that is putting out nearly 40kw more in stock form.