Help/advice Rb30 rebuilt head power figures

[Smith666]

Hey guys just joined, been using the page for awhile very helpful thanks. As title states unsure if power figures are low or normal/expected.

I've had my head rebuilt (will post Pic of cam specs) camtech cam, 1mm oversized stainless steel valves, Port & polished, new lifters, cracked tested, match ported manifold etc. Stock bottom end 

Bolted everything together took it in for a nistune and dyno tune, had a few minor issues. He finished the tune ended up with 108kW and around 240nm.

Just thought it would produce more kW with the head work.

Mods: rebuilt head, match ported manifold, 6-3-1 extractors 2.25inch straight though, believe hifow cat, nistune, k&n podfilter

Thank you

[KiwiRS4T]

What's your compression ratio... what head is it?

[Smith666]

Rb30 head. Was told compression ratio wouldn't have changed so I believe it's 9.0:1, Could be wrong.

[Dale FZ1]

RB30E with a cam and extractors.  If it made a genuine 120rwkW you'd have to be satisfied.  Not far short at 108.  Guessing it's all done at 5000rpm?

It's a lot harder to make NA hp, and it's going to involve compression, proper fuel eg E85, lots of revs and light components that rotate and reciprocate.  Toss out the 2 valve head and get a 4 valve.  Multiple throttles inlet, and then find someone who understands inlet tract length, header design, and cam spec/timing.

Presuming you're in love with NA RB engines.

[Smith666]

17 minutes ago, Dale FZ1 said:

RB30E with a cam and extractors.  If it made a genuine 120rwkW you'd have to be satisfied.  Not far short at 108.  Guessing it's all done at 5000rpm?

It's a lot harder to make NA hp, and it's going to involve compression, proper fuel eg E85, lots of revs and light components that rotate and reciprocate.  Toss out the 2 valve head and get a 4 valve.  Multiple throttles inlet, and then find someone who understands inlet tract length, header design, and cam spec/timing.

Presuming you're in love with NA RB engines.

Differently not disappointed with the power, just wanted abit more torque and kW's as I'm hoping to get into hill climb/time attack, I was thinking around 120rwkw but like you said not to far off. Yeah on the dyno sheet all done by 5000rpm.

Yeah nearly everyone I've spoke to has said go DOHC or turbo but I wanted to keep the SOHC and remain NA, ahaha yeah don't know why just not a fan of turbos in my cars, driven a hand full and their fun to drive just rather NA.

Just got into RB's so pretty much a learning experience, pretty much just been into rotarys for the last 10 years. (I'm only 23)

 

[admS15]

Nos

[Dale FZ1]

I started motorsport in rally, navigating in a R31.  There's nothing wrong with a good NA.  It's just that a 2 valve RB head is nothing at all special. 

The whole thing can be made better ie able to breathe and make the torque at higher rpm with a 4 valve head. Depends how much you want to go down that path, and what the budget is to make things less wrong.

Big heavy NA RB won't go through twisty hillclimb stuff that easy, and you'll need a sun dial to time it for Time Attack.  But you could certainly have fun.  Fatz evidently had a whale of a time in 24 hour Lemons event with his R31. 

[Dose Pipe Sutututu]

Get a RB25DET NEO head on it, bring up the comp to about 11:1, put massive cams into it and rev it to the moon... could even adapt ITBs to it.

A high comp, 3.0L, NA with ITBs and VCT would be pretty fun.

And as Bill said, nitrous.. I would spray nitrous into it.

[admS15]

2 of the big ones [emoji12]

[Scottyd 240z]

I recently got 130rwkw from a n/a RB25/30 with Tomei cams, pod filter, good exhaust no extractors, 10.5:1 comp. You could spend approx 3k on head and cams and only really get another 20kw. I’m looking for a Supercharger

[Dale FZ1]

On ‎12‎/‎26‎/‎2017 at 8:16 AM, Scottyd 240z said:

I recently got 130rwkw from a n/a RB25/30 with Tomei cams, pod filter, good exhaust no extractors, 10.5:1 comp. You could spend approx 3k on head and cams and only really get another 20kw. I’m looking for a Supercharger

A decent L series with LD 3.1 stroker crank and LOTS of attention to detail with all the right bits to achieve airflow might struggle to do better than 210rwhp (say 165rwkW).  There's a fairly serious spend required to get there, and a lot of revs that sacrifices low rpm torque. 

One of those IMO is a spiritual father to a 30DE donk.

I think a 30DE build as you've described is pretty good if it made 130rwkW while retaining a dirty old cast manifold.  I'd guess it did its best before 6000rpm too. 

If you wanted to play up around the 8000rpm mark there's a fair bit of engineering magic required: complete inlet tract, porting, cam profile and timing, complete exhaust tract, and I'd say a proper crank trigger kit to avoid timing scatter.  Notice that's all airflow related.  You'd still want pistons/rods/fasteners/proper valve springs, retainers, light buckets/light flywheel and balance the lot.  And a properly thought out oiling system.

N/A horsepower doesn't come cheap.  But it can be very effective when done right.  Look at the BMW M3 engines, particularly thinking the 3.0 and 3.2 litre I6.

 

[niZmO_Man]

There was a bloke with an R31, RB26DE with 12:1 comp ratio. I can't seem to find it around here.

[Scottyd 240z]

On 29/12/2017 at 11:30 AM, Dale FZ1 said:

A decent L series with LD 3.1 stroker crank and LOTS of attention to detail with all the right bits to achieve airflow might struggle to do better than 210rwhp (say 165rwkW).  There's a fairly serious spend required to get there, and a lot of revs that sacrifices low rpm torque. 

One of those IMO is a spiritual father to a 30DE donk.

I think a 30DE build as you've described is pretty good if it made 130rwkW while retaining a dirty old cast manifold.  I'd guess it did its best before 6000rpm too. 

If you wanted to play up around the 8000rpm mark there's a fair bit of engineering magic required: complete inlet tract, porting, cam profile and timing, complete exhaust tract, and I'd say a proper crank trigger kit to avoid timing scatter.  Notice that's all airflow related.  You'd still want pistons/rods/fasteners/proper valve springs, retainers, light buckets/light flywheel and balance the lot.  And a properly thought out oiling system.

N/A horsepower doesn't come cheap.  But it can be very effective when done right.  Look at the BMW M3 engines, particularly thinking the 3.0 and 3.2 litre I6.

 

Yes they are expensive, I know a guy with a stroked L-series in his 240Z producing 220rwhp that cost $25k to build.

My 30DE peak power was at 5800rpm,  and I will be replacing my dirty old cast manifold with some extractors and new exhaust soon. 

Will I need a re-tune for extractors and exhaust ?

 

[Dale FZ1]

Two things I'd suggest before spending up on some extractors.

First, establish what you want the engine to do, what rpm range you are going to find acceptable (implicit in that is the gearing you have, and whether a diff ratio change is necessary or desirable), and what $$ cost you want to limit this upgrade to.

Second, find a competent engine builder who understands RB heads. ( I'm hesitant to recommend any particular builder, but suggest The Mafia might be able to help with a name. )  Depending on their advice and your budget,  you should review those cam specs and decide to either replace or re-time the Jap cams.  Your head may require porting modifications (and I've seen instances where there was material added into an RB port to improve flow).  At the very least those cams should be properly degreed for the outcome you want.  Not a guessing game.

Then find who is going to build those extractors for you. (unlikely there will be any off the shelf for an RB twin cam).     They should establish the diameter/length of the primary and secondary pipes, plus the diameter of the system being built, based on your goals and some critical spec details on the engine.  There is a handful of people in the country who are properly competent in this area, IMO.

Once that's done, you're probably heading towards an engine spec where things are designed to work together.  And yes, you should then be looking to have the tune sorted so that fuel and ignition are working with the airflow characteristics of the engine.  

[niZmO_Man]

Fatz's Winefulled Racing R31 was dropping below 1:05 around SMSP south (from memory), but that's a stripped out car with advanced F1-style aero.