NA Performance RB26

Hi all,

Found this forum via google and it looks like there are plenty of knowledgeable people here.

I am looking to fit an RB26 into my 240z. Seems the logical engine to use.

I am however not a big fan of turbos, and to keep it more in keeping with the 240 I'd like to do it NA. Now I know the Skyline comes in NA form (GTS isn't it?) but I'd like to make some really good power.

I have looked at using the RB30 bottom end from Oz, and the OS Giken kit, and the stroked HKS kit. The Giken kit is a lot of money really, which is fine if you are making 1000hp, but my NA won't. I like the extra capacity of the RB30 block and so I could make my own Giken style kit, and I'd like about 500bhp ultimately so it wouldn't be overly stressed.

Well anyway, if anyone has any experience of this kind of thing, any links to engines other people have built with the same idea, or any stats on the standard GTS engine (which I can use and then hot up??) I'd appreciate it.

Thank you for your time,

Russ

Here are some of my thoughts:

Firstly I'd like to use as many Japanese parts as I sensibly can. I am not willing to throw money away just to do this so the rule isn't written in stone, for instance the ECU, I'd like MoTec, and I know the instructions will be written in English. Now maybe there is the Japanese equivalent, but I may not be able to understand how to use it or the software :)

Fuel: 95 RON probably.
ECU: Motec, or equivalent.
Head: RB25??? I need to up the compression, something like 10:1 would be nice. Obviously worked on (flowed/valve job etc)
Block: RB30
Inlet: Standard throttle bodies??

Ok now I'm lost as I'm not a turbo man and I get confused :)

I'd love a sequential box, OS Giken again? But I imagine that'll cost as much as my engine :) Can is to be used for road, track and strip. Nothing serious so a very fast road set up would be nice, don't want a on/off racing clutch or anything though. Not sure how that works with a sequential set up anyway?

hey mate im from oz here.rb26s only came out in turbo form. the 3 litre you r refering 2 doesnt have a lot more power than your original motor,plus they r getting real old now[86-87]. easiest motor for you would be an sr20. source an import crossmember and theconversion is simple. turbo or non turbo your choice. my advice would be to have a drive of a few turbo cars so u can decide if u want turbo

Hi mate,

Thanks for taking the time to reply. The Sr20 is a no no, four pot and I wan t a 6 :) Sort of had the feeling the RB30 would be getting old now, but I could use a modern head.

I've had more success in this discussion at

http://www.skylinesaustralia.com/forums/index.php?showtopic=119495

Maybe you'd like to take a look.


Cheers

You wanna make 500 hp out of a NA engine not bigger then 3 liters? That means you need a high reving engine. (take the NSX engines for example). A high CR (11.5:1) and therefore high octane fuel. I think you need an adjustable length intake.
And you are gonna use it as a daily drive? Then I assume you want some low end torque also?

In my opinion (but that is only from my point of view) 500 hp is a bit to high for an 3 litre NA engine in combination with a 'daily' drive. (but I don't say it isn't possible, it can be done with the right amount of money. And as you talk about OS giken that doesn't seem to much of a problem) I have my doubts by the low end torque (I don't think you wanna rev the engine to 4500 revs/min everytime you pull away from the traffic light.) in combination with high power.

This is not ment to discourage you.

Derby

(I hereby apologise for my reaction if I understood something wrong)

Hi,

Thank you for your reply. No no, I'm not the sort of person who gets upset when I don't hear what I want.

I was hoping on the holy grail of 400bhp, and the car will be high days and track days, not a daily at all.

High revs, high octane, high comp, high tech. That was the plan basically. Basically a few people in my club run 2.8s with ITBs, trick ECUS, and 30yr old head designs (SOHC, 12v 6 pots) and make 250bhp. I was *hoping* with 24v, VVT, twin cams, and better flow I could see 400bhp. I will probably only run 99 RON as that's what is commonly available here so I may need to back off on the comp a little?

Some low end would be nice, 4500 would be above what I want as the car will see some traffic no doubt, and I'd probably end up killing expensive clutches. Depends on how tall first gear is I guess, was going to go for a 4.11:1 rear diff or something as I intend to do some strip work and the guys in the club aim for about 4:1. I guess it'd be different if you have more power though and I've no idea of skyline gear ratios.

Anyway I like the Skyline Z tune RB26, that was stroked to 2.8 which might be the way to go.

Money doesn't grow on trees for me, but this is a long term project so it just means it takes longer. I don't see the Giken kit to be good value for what I want really, I think I'd be better off with a stroked RB26, and the money saved could be spent on better (lighter) internals.

Cheers

Russ

Good to see you are up to an open discussion.

Te start with what you said last. Lighter internals are the way to go for high reving engines. I think the rb26 will rev up to 9000 with some work done to it. But I think there will be people around that have more experience with that.

About the 4500 revs/min for pulling away is over here a signal a granny is driving a car. It is all about the expectations I guess :wink:

The problem is with the 99 ron or something like that is that I don't know what to compare it to. Is it comparable with the 98 octane number in Europe?

An CR of 10:1 or 10.5:1 is nice for an NA engine. Then there is some safety margin for higher intake temperatures and so on.

About the 400 hp. That is more realistic. The BMW M3 (e46) pulls 343 hp out of a 3.2 six cil line engine. And BMW Motorsport has the reputation to have the best engine tuning capabilities for in-house tuners. I think you should take that engine as an example when you start tuning your engine.
http://www.bmwworld.com/engines/s54.htm An overview of the s54 (e46 m3 engine). I don't have to remind you that BMW has a big budget, but that have one big disadvantage over you and that is emissions.

And if you have a high reving engine with low torque you can compensate for the low torque with short gears. (Honda for example. Very low torque but because of the huge rev range a short gear is sufficient.) For a nice top end speed i would go for a 4:1 final diff with some what longer 4th, 5th and 6th gears.

Just say what you think about it. Having clear what is possible and how to do it makes building an engine more easy.

Derby

High end horsepower sucks! I have a boss 302 that has to rev to 9000 just to get the power out of it, and its horrid on the street. For the track is another story.

I think Derby is correct, 400hp would be a much more realistic goal, and that is at the crank, without making the engine a complete dog on the street.

That is why turbos are so great, you do not have to run a huge cam to make huge power, and your still able to keep the car streetable.

With a V8 its a little different, because you have the cubes to play with, but limiting your self to a 3.0, your going to have to spin it to the moon for power, that is plan physics.

Hi,

I think my original 500hp must have been a typo, I asked for 400hp on every other forum. I don't believe 500hp would be realistic with normal ron petrol :)

I think 99 RON is 99 on the continent, RON is just the measurement, see http://www.millersoils.net/pdf_downloads/octane_nos_explained.pdf for explanation (RON vs MON etc).

We can get 108RON here but it's very expensive and not as readily available. An option I had considered is bio ethanol as a fuel, I think that's about 110 RON, but I know nothing about it... yet :)

If I wanted easy horsepower I wouldn't be considering an NA RB26, I'd drop a SBC in or a turbo engine. BUT my car has a NA straight 6 engine in it, a Datsun L24 to be precise, the RB engine is obviously from the same manufacturer, again a straight 6, and so it has the right soul for my car. I could do turbos, but that wouldn't be in keeping with the L24. Plus big throttle bodies are naughty! :D

Can anyone recommend a comprehensive RB26 engine parts website please so I can start eyeing up products/prices? Also who'd make the most appropriate stroked crank? HKS? Or try and get the NISMO one?

About the fuel...if you go for bio ethanol (which i personally recommend for future HP increases) think about the rubber sealings in bearings, fuel lines. They have to be tested to be resistant to bio ethanol.

About parts...HKS, NISMO, all build parts for turbo engines, which are stronger then they are light (big pressure above the piston). Strength is the main design demand. Lightness is not. And you need lightness.

I think you have to see what you can do with Honda/Acura parts...But that won't be easy.

Let me know what you have found.

Derby

www.takakaira.com (http://www.takakaira.com) or greenline

I know where your coming from on the build, sounds like you have made up your mind, its cool to be different:D

Hence me putting a turboed V8 in a GTR :D

Check this out, it talks about the break down of the silicone when using meth injection.

http://www.turbomustangs.com/smf/index.php?topic=64229.0

I have to say that I would be much impressed by a 240Z revving up to 9500. That makes an interesting competitor at the traffic light :grinyes: I speak from experience that shifting late cos of high revs is an advantage.

And about the bio stuff. Most modern diesels (Volkswagen TDI) have sealings and hoses that are vegitable oil resistant. But the older engines won't. And the damage can be serious.

You can also try to run your car on LPG or even better CNG. CNG has a octane number of 114. And if you have a good ECU setup it can detect the octane your running on.
Fast diesels are out. Sportscars on CNG are in :lol:

Derby

I have to say that I would be much impressed by a 240Z revving up to 9500. That makes an interesting competitor at the traffic light :grinyes: I speak from experience that shifting late cos of high revs is an advantage.

Sportscars on CNG are in :lol:

Derby

Yep fun, except if you are driving normal :shakehead

CNG Sportscars just might be the next big thing:nono: :naughty: :iceslolan

Thanks chaps. Does anyone have any good bio ethanol links? I guess I could build my engine with biothanol in mind, and still run it on petrol, and switch to bioethanol when I feel like it running different engine maps? I'm a bit of a geek so intend to spend a fair wedge on a top MoTec ECU or something, really fancy plugging my laptop into my car and checking it all out.

Thank you for the links, and http://www.greenline.jp/ is Greenlines website. I will spend my break time perusing that :)

Yes 9500 rpm 240zs would be awesome, even if it's not as fast as a turbo'd car it'll sound absolutely awesome (I think/hope). My other car I'm working on getting is a 68 Dodge Charger, so I'd have a high revving jap car and a (blown) yanky v8, best of both then (imho). One day...

I think I'll avoid gas as a fuel for now :)

Another thing a friend is trying is he's fitted an intercooler for his NA engine, just cooling the intake for him, thought it might work and be a bit novel.

I'm gonna look for the bio-ethanol thing.

And the intercooler for an NA car...that isn't gonna work. the internal resistance is quite high of an IC.

I think he is fucking up power.

Derby

Hadn't thought of the resistance, I won't say anything to him and have to see how it goes :)

An IC on a N/A engine? WTF is that about.

Well I know I don't need to spell it out for you :)

But thinking about it (I hadn't up till now) I cannot see the point of it. Its cooled by air (it's not a charge cooler) so there is zero advantage to it.

When I see him at the weekend I'll investigate it and see what the hell he's up to :)

About bio ethanol as promised

"Generally, the higher the ethanol component of a gasohol blend, the lower its suitability for standard car engines. Pure ethanol reacts with or dissolves certain rubber and plastic materials and must not be used in unmodified engines. Additionally, pure ethanol has a much higher octane rating (116 AKI, 129 RON) than ordinary gasoline (86/87 AKI, 91/92 RON), requiring changes to the compression ratio or spark timing to obtain maximum benefit. [5] To change a pure-gasoline-fueled car into a pure-ethanol-fueled car, larger carburetor jets (about 30-40% larger by area) are needed. (Methanol requires an even larger increase in area, to roughly 50% larger.) Ethanol engines also need a cold-starting system to ensure sufficient vaporization for temperatures below 13 °C (55 °F) to maximize combustion and minimize uncombusted nonvaporized ethanol. On the other hand, if 10 to 30% ethanol is mixed with gasoline, no engine modification is typically needed. Many modern cars can run on these mixtures very reliably."

More info (http://en.wikipedia.org/wiki/Ethanol_fuel)

It probably won't work. Or he should install a truck IC or a IC with a huge volume then the resistance will drop.
Same thing with NOS for NA cars... it helps a bit but it was never designed for that matter.

Derby

That's brilliant Derby, thank you. I don't think there will be that much to replace to use bio ethanol, we were talking at work and valve stem seals, fuel lines, fuel pump maybe, and any plastics that are used on the RB engine?

I live in Somerset, usually just farm land but!!

Bioethanol is currently available in a 5% blend at over 250 Tesco petrol stations in the South-East of England. This petrol is supplied through ordinary unleaded petrol pumps and is not identified as bioethanol-blended petrol.

Morrisons have now begun to sell E85 petrol (85% ethanol, 15% petrol) at the following Morrisons filling stations:
Albion Way, Norwich, East Dereham, Lowestoft, Diss, Ipswich plus five sites in Somerset. Further filling stations are planned.

Five petrol stations in my county supply 85% mix :) Of all the places, only thing is I couldn't drive too far! Although I could put in 99 RON with an octane booster if I got stuck. Anyway 85% ethanol, 15% petrol is called E85, which is this

http://en.wikipedia.org/wiki/E85

Which is 105 Octane :) This could work out to be an interesting little engine. 11:1 compression?

11:1 is very good possible with 105 octane. Lucky bastard :lol:

I think it is wise to have your engine converted to be able to run on bio fuel. At least when you think you will run it for more then 5 years. I'm not a tree hugher, not at all. But because it is environmental friendly the government could use a tax cut on bio fuel (I say could, I don't know how the government thinks about that. I know in The Netherlands it is a point of discussion). With the more stringent rules about CO2 emissions and all, bio fuel is a good solution to get within the limits of the Kyoto treaty. And when the price drops it becomes more interesting, right?

About the parts that you need to change, don't underestimate it. BOV, all rubber hoses, sealed bearings, valvetrain cover sealing, rubbers of the throttle. Rubber is used everywhere in and out of an engine. Just don't try to save money on it.

Derby

Yeh, I think bio ethanol must be fairly future proof, seems a good way to go. And if it isn't I could still run another high octane fuel (99RON petrol with booster).

I think you're right not to underestimate the amount of rubber/plastic. My trouble is I've only worked on 70s engines where there was little/no plastic :) At least there will be nothing to perish this way.

http://www.skylinesaustralia.com/forums/index.php?showtopic=119495

I'm also posting there, considering using the RB30 with an ATI balancer, but they still think 7500rpm is pushing it. I want 10k! lol. The higher the rpm the better for my NA performance.

Hmmm

Oh and my friends N/A with intercooler was a wind up, he semi fitted it and took photos for us before the drag season to throw us off lol.