rb20det block build :question:

[amnash]

So my original plan was to just build the block with stock pistons/rods/crank. but my friend has convinced me to upgrade all that while i have it stripped to save myself a bigger head ache down the road. makes total sense. at first i didnt really have a plan and was just buying things and replacing them. but ive set a goal and gonna build from the bottom up. i figure this will actually save me money.

so eventually i want to have 400 whp. wont all happen this winter but ill build the block to handle it now and do the head next time i win the lotto.
so i have a couple questions:
1) How much horse power can the block handle before you start running into issues?
2) If i had to upgrade the block to easily handle 400whp would it just be the pistons/rods/crank? or girdle aswell? or maybe just pistons and rods?
3) Does anyone know any good "bang for your buck" deal/kits for the rb20 block??

[M13]

It's really up to you.

If I was building a 20, I'd upgrade the head also w/ full valve job, new valve seals, guides, TOMEI solid lifters, spring upgrade.

The block itself is fine as it's very thick. I'd be more focussed on writing things down on a list and see what your options are.

[amnash]

agreed. i plan on doing all of what you said along with top mount exhaust manifold front face intake cams/fully rebuilt head and a nice turbo to go with.
but the last thing i wanna do is build the block now with oem pistons/rings/rods etc and then find out that the block cant handle what i plan on bolting on later down the road.

im aiming for 400whp (soo 430hp @crank???) just making sure the block can handle that now or if upgrades are needed

[Skym]

R31 house (RB20DET experts in Japan) have extracted close to 500hp (495hp) at engine -


http://www.youtube.com/watch?v=BJETc3EfZIE

Here's vid of the lap in above videoclip -


http://www.youtube.com/watch?v=ZVxyp8ErZnA

But I think R32 RB20DET performs best with around 314rwhp and just lighten the chassis alot -

http://eyevio.jp/movie/228538

1:01 around Tsukuba with traffic on racetrack. Fastest is 59sec by a GTS-R.

Thread on above car (photo's of engine bay, undercar, rough spec list, dynochart, etc) -

400hp RB20DET powered R32 GTS-T on Tsukuba

Don't need to spend much on RB20DET to make it quick.

If want an idea of how quick that R32 with RB20DET is, compare to 600hp R33GTR, 600hp R34GTR and stock R35GTR on Tsukuba with no traffic -


http://www.youtube.com/watch?v=mo44KAwHQMs

Group-A GTR racecar with 550hp at engine, setup for Fuji racetrack = 1 minute flat lap around Tsukuba. Basically a R32 with RB20DET can be just as quick for less $$$ spent and have less than 400hp at engine (I think 314rwhp is around 380hp at engine). Also that R32 with RB20DET had traffic on racetrack, so could have been 1 minute or under if the EVO didn't hold him up.

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For fully built RB20DET (like mentioned in post's above) -

With head, bronze valve guides (Tomei bronze valve guides), new stronger valve springs, new lifters (when fitting new cams, good idea to fit new lifters, valve springs and bed them in together if you want head to be reliable), Tomei Procams. Or just use Tomei poncams, new valve springs. If you want upgraded valves (1mm oversize) fit Supertec valves.

Can make custom mains caps and plate that joins mains caps to bottom of block to replace stock girdle, stock mains caps, etc. It helps to strengthen bottom of block.

Example of what I mean on bottom of RB30 block with custom CNC made mains caps -

http://www.trackscotland.co.uk/forum...bca0134b7cb96b

There's a plate that goes over the top of the custom mains, block that joins them together -

http://img525.imageshack.us/i/ripsbi...scapkit00.jpg/

VR38 (R35GTR) has this type of mod at factory -

http://farm3.static.flickr.com/2566/...8cc9cde3_b.jpg

But they use moulded bottom of block as 1x piece for mains, plate. Same design on aftermarket aliminium block for RB26.

For H beam conrods, forged pistons, from Spool -

http://www.spoolimports.com/content/...ONPACAKGES.asp

Also you'll need N1 oilpump with upgraded Reimax gears (can order them online) and a crank collar to replace the short length oilpump drive on front of stock crank -

http://www.spoolimports.com/content/N1OILPUMPS.asp

Then custom copper intake, exhaust gaskets (factory gaskets can blow under higher boost levels on RB20, RB25, RB26), Tomei 1.2mm headgasket (or thicker if your running over 20psi).

Also ATI? crank pully, Nismo flywheel (slightly lighter than factory flywheel), as light enough for higher rpm use. A very light flywheel is said to affect performance of engine when used for road use (I assume off boost). Factory flywheel is heavy for a good reason.

[amnash]

sweet thanks for the info very educational.
i think i will aim for a 400hp at the engine instead of whp seems more realistic for oem pistons/rods

the oil pump set up you described is a bit confusing. i already have a new n1 oil pump i plan on installing. what the point of a crank collar? and those gears..are they the ones internal of the oil pump itsself?

[gtrjon]

i never really understood it before just do your research. heres a site that i find very useful and is updated lots http://skyline-life.blogspot.com/p/r...-oil-pump.html

[Skym]

Yes, the gears inside oilpump. That link in post above explains better than I can (thanks gtrjon).

Also the metallurgy, thickness? of the gears is better with Reimax gears vs stock N1 oilpump gears.

400hp is the safe hp level the gearbox can handle if in good condition (rebuilt / refreshed). Engine can produce more.

Max I've seen is 560hp with stock conrods, stock pistons, stock cams with high octane gas (reason why engine hasn't had any knock that's caused it to fail).

My car can achieve 360hp at engine (16psi) with stock RB20DET engine, Z32 MAF, fuel system upgrade, stock ECU, etc. With aftermarket ECU + MAP sensor, adjustable camgears, 380hp is possible (has been done before with those mods). Basically 295-315rwhp. Or could fit Tomei Poncams + tune to suit to get the extra 24hp bump at same boost level instead of fitting aftermarket ECU, etc.

[nelsonmxmarc]

Like Skym said;

For fully built RB20DET (like mentioned in post's above) -

With head, bronze valve guides (Tomei bronze valve guides), new stronger valve springs, new lifters (when fitting new cams, good idea to fit new lifters, valve springs and bed them in together if you want head to be reliable), Tomei Procams. Or just use Tomei poncams, new valve springs. If you want upgraded valves (1mm oversize) fit Supertec valves.

The most stringent part of your build is moving more air. Proper head work will ultimately ensure this. From what i gather from Skym's knowledge, and SAU, Tomei Poncams with stock valvetrain will get you a great deal of low/midrange power (not very aggressive cams). It's best to fit new valve springs, as the originals are paired to stock lobes and are likely quite worn after 20 years of use (sag etc). Stock valves are good for your particular build, but like mentioned, fitting oversized valves (brian crower/supertec etc) will be a good option. This means new valve seats and $ in machining. If you want to save money, what i can offer as a reliable option is to spend time measuring tolerances..

1. Check your lifters - After considering new buckets, measuring with a micrometer yielded tolerances WELL within spec. Though you will be bedding new cams/springs to old lifters, it's not the worst in terms of reliability.

2. Valve guides - check for play. In my case i was lucky to reuse stock valve guides. The only reason i didnt upgrade to bronze guides is simply because i'm not sure where my next build will go. If i keep the 20 head and decide to go 2.3, i will ultimately change those as well. However, that being said, there was zero play and considered well within spec, so if they're "OKAY", you can do without at the moment.

3. Get a good porting job done and call it a day!

So for about 900-1000$ you can have a well dont head, assuming you went with poncams and valve springs..

As for the bottom end, dont forget, if you're fitting NEW bearings to old journals, you WILL need new con rod bolts and they WILL need to be deformed to the proper size. This is best left to the hands of a professional, as the crank may need to be polished and then balanced. But assuming you're re-ringing, you'll need a line hone anyways, so the block will already be in their possession.

If your you plan is to save money, do the headwork yourself. It's time consuming but will save you a great deal of cash. The bottom end, and crank will best be suited to professionals. Other option is to pull the pistons/rods and take the proper measurements of the journals/bearings. The size discrepancies are in the FSM. Then order the proper bearings on your own behalf to save on cost, give them the goods and let them do their magic. Otherwise, leave it to them. Its a LOT of work, and if you want a mindblowing look into the rebuild, check this out;

http://www.gtrpwr.com/showthread.php?t=9

Mcfly does a good job of abusing the plastigauge, but you can rest assured everything is well within spec.


My build is following suit of Skym's Tsukuba video. A lightweight car with moderate hp is going to work wonders in all respects as it maintains lower spool levels, and at the same time achieves great overall drivability. 350 whp is my goal at the moment, which is roughly 400 crank. With a hybrid rb25 turbo, OEM built bottom end and built head, it shouldnt be an issue (281 whp now with stock RB20 turbo and stock motor). You won't find it hard reaching your goals. With a proper SAFE tune, you'll be driving the car without any worries!

[Skym]

Turbo on my cars RB20DET reaches full boost at 3500rpm and pulls all the way to 7500rpm without dropping off. The stock rev limiter stops engine from producing more hp. Because 0 on boost gauge is around 2000rpm, can drive with the engine off boost to get good fuel economy.

Poncams can help to spool a bigger turbo. How they do this is extra fuel is injected (when you retune engine after fitting cams) to match the cams allowing more air into cylinders at bottomend and throughout revrange. So the extra exhaust gas created at bottomend helps to spool turbo slightly earlier.

If you go too aggressive with cams, the bottomend of power curve starts to bow alot. Poncams don't make the curve bow as much at bottomend and you can see that when compared to stock cams on dynochart. If you look at the Tsukuba spec R32 link above, you'll notice there's a slight bow in bottom of power curve. I suspect that engine might have Poncams, adjustable camgears. But factory cams can produce a similar bow with adjustment to camtiming, so hard to tell.

This RB20DET has Poncams, small T3 turbo (similar to stock VG30DET turbo) and cams are adjusted to produce more topend hp (I learnt from a tuner when were fitting adjustable camgears to stock GTR that adjusting camgears for more topend takes more rpms before engine goes nuts and you can see that in videoclip and the lumpy idle gives it away, which is another thing you notice from engine after adjusting camgears for more topend) -

http://www.youtube.com/watch?v=LKVqmzp1piQ

That looks like the UK dudes GTR build in that link in post above. I think he had a pit in his garage, so he can do oilchanges, etc?

[M13]

what sucks about 400BHP is that you want more.