Hks Camshafts Into Rb20 Researched, One Last Question

[335]

Hello

I am going to put HKS 272 with 8.5 lift camshafts into my R32 GTS-T with a RB25 turbo, upgraded fuel pump and injectors(They are RB20 camshafts). I read the HKS website and it said that their camshafts are direct replacements and are made to fit stock valve train components. Does this mean that I can put them in without tuning? Also since they are stock lift, do I have to change the lifters to solid lifters?

Please help

[Adriano]

Car will need to be tuned, and will not require solid lifters, cams are probably bigger than i would recommend for your setup though.

[paulr33]

i believe you have spoken to Roy already, cams for the rb20 = waste

[AD4M]

i believe you have spoken to Roy already, cams for the rb20 = waste

haha not entirely... thats one persons opinion.

i saw good gains with driveability when i did mine.

the duration is huge on those cams, but you wont need to do any mods to the head to fit them (i straight dropped in a set of hks 264 9.1mm)

personaly i would upgrade the valve springs, i didnt when i put my cams in and never had any problems, but for my new motor i will just to keep everything safe.

you will definatly need a new tune!

its also worth while fitting adjustable cam gears at the same time and having them dialed in to get the best gains

[335]

Thanks I know big but since I have them I want to try to see how they work.

[Roy]

haha not entirely... thats one persons opinion.

i saw good gains with driveability when i did mine.

the duration is huge on those cams, but you wont need to do any mods to the head to fit them (i straight dropped in a set of hks 264 9.1mm)

personaly i would upgrade the valve springs, i didnt when i put my cams in and never had any problems, but for my new motor i will just to keep everything safe.

you will definatly need a new tune!

its also worth while fitting adjustable cam gears at the same time and having them dialed in to get the best gains

Any before / after dyno sheets and general comments on changes to throttle response and transient boost response?

[SKYPER]

Did engine have a light weight flywheel when you installed those camshafts???

Read this -

http://www.uucmotorwerks.com/flywheel/how_...wheel_works.htm

For RB25 turbo, 256 Tomei Poncams would be better.

Edited April 16, 2008 by SKYPER

[AD4M]

Any before / after dyno sheets and general comments on changes to throttle response and transient boost response?

a few changes were made at the same time so no i cant say i have any dyno sheets befor/after

the biggest set back on the 20's are the heads everyone knows that, make it breath better and you'll make improvements.

throttle response on mine was a huge improvement, but again cams werent the only things that would have aided that

skyper- my car has always had a twin plate os giken. and i agree the 256 poncams would be better suited to the turbo.

[Roy]

the biggest set back on the 20's are the heads everyone knows that, make it breath better and you'll make improvements.

throttle response on mine was a huge improvement, but again cams werent the only things that would have aided that

Bugger One day we will bag a good before after comparison of just cams

Re the head and making it breathe better. At first glance i can understand why people say the RB20 head doesnt flow well. For a long time i went with that thinking and didnt challenge it. Until one day when i noticed my setup getting better results then the same setup on an SR20 which got me thinking

Firstly not saying cams wont help, but consider this when looking at the RB20 head.

STD Rb20 cams are 240/7.8 (IN/EX). Now the RB25 has the same cam size despite the extra 500cc and 0.5:1 compression. It does have VCT though. Now the RB26 runs 240/236 8.58/8.28mm cams

Now looking at the difference in displacement etc then you can start to appreciate that the cams in the RB20 are not exactly small to start with. They have same/similar duration as bigger RBs and only a little less lift then the RB26.

So you then consider that the RB20 has smaller ports, runners and valves. But it has to because it only displaces 2L, if it had runners and valves the same size as an RB25 then its gas velocity woudl suck and would not be able to spool the std turbo let alone an aftermarket one.

So it rightfully has smaller runners/valves to ensure good velocity and cylinder filling. But here is the thing that ppl do not consider. At only 2L the RB20 shares the same basic displacement as an SR20.

Now being a 6 cylinder the RB20 displaces less cc per cylinder then the SR20, which is basically 500cc per cylider vs the RB20 333cc. Now consider the total surface area of valve for the RB20 and SR20 and you will see that per swept volume of each cylinder the RB20 has more valve surface area.

So dont sell short the power and flow that the RB20 is capable of. It flows just fine for a 2L, with time and more ppl actually bothering with the RB20 we are seeing more and more ppl get great results, previously dismissed as impossible for an RB20

[R34GTFOUR]

if anyone can prove that the stock unopened rb20 is good for power, adam can

i could hardley believe some of the numbers that motor pushed out

[r3240sx]

if anyone can prove that the stock unopened rb20 is good for power, adam can

i could hardley believe some of the numbers that motor pushed out

There's a new one on the rb20 dyno thread with a t04z actually.. Stock block, Stock cams, pistons, rods, ebay turbo manifold.

28+ psi boost 370rwkw maxing out the speed on the dyno. He said power was still climbing. The RB20 is so strong for its size, it amazes me.

-Max

Edited April 16, 2008 by r3240sx

[SKYPER]

AD4M, so your car did have lightweight flywheel. I guess it would explain the good drivability.

Also you need a valve spring upgrade with 264 intake 8.9mm lift, 264 exhaust 8.9mm lift cams. At higher rpms, might get valve bounce

due to weaker stock valve springs. I wouldn't take the chance of a valve hitting piston crown or damaging camshaft lobe at

higher rpms.

There's like a set of valve springs suited to different duration, lift cams (for example Type A, Type B, etc).

Even though you don't need a valve spring upgrade with Tomei Poncams, there is set of valve springs suited to those camshafts

if stock valve springs need to be replaced.

HKS 264 intake, 256 exhaust seems to be a good setup for a GTRS turbo on SR20DET for street / racetrack use (240-270rwkw). I wouldn't think

that RB20DET would be any different, as there is that option from HKS for RB20DET.

I guess T04Z would suit HKS 272 duration cams, RB24 engine (stroked RB20), as I saw a Blue R32 GTS-T dragcar (for sale) in Japan with that setup.

Claimed output was around 540ps.

Edited April 17, 2008 by SKYPER

[335]

AD4M, so your car did have lightweight flywheel. I guess it would explain the good drivability.

Also you need a valve spring upgrade with 264 intake 8.9mm lift, 264 exhaust 8.9mm lift cams. At higher rpms, might get valve bounce

due to weaker stock valve springs. I wouldn't take the chance of a valve hitting piston crown or damaging camshaft lobe at

higher rpms.

There's like a set of valve springs suited to different duration, lift cams (for example Type A, Type B, etc).

Even though you don't need a valve spring upgrade with Tomei Poncams, there is set of valve springs suited to those camshafts

if stock valve springs need to be replaced.

HKS 264 intake, 256 exhaust seems to be a good setup for a GTRS turbo on SR20DET for street / racetrack use (240-270rwkw). I wouldn't think

that RB20DET would be any different, as there is that option from HKS for RB20DET.

I guess T04Z would suit HKS 272 duration cams, RB24 engine (stroked RB20), as I saw a Blue R32 GTS-T dragcar (for sale) in Japan with that setup.

Claimed output was around 540ps.

My cams are the stock 8.5mm size, do I still need new valve springs?

Cant afford a new turbo right now so will stick with the RB25 turbo.

Thanks for the info.

[Roy]

Have you actually purchased the cams? if you have then sell them and put the money towards a better turbo. If you havent got he cams yet then put the money towards a better turbo.

Gut feel is if you are going to try cams then i would go smaller, around the 256/8.5mm. Will be interesting to see the results though, i hope i am wrong. Be great if they turn out to be ball tearers, i will run out and grab some

[AD4M]

skyper i think your missing the point, my car has always had the same clutch, so any changes i made i could tell the diference... regardless of the clutch being lighter than stock.

i will be installing stiffer valve springs in my new motor, either tho the car didnt suffer audiable valve bounce and only died because of a broken ring land. and mine are bigger than 8.9mm lift

Mike you dont have too upgrade them.

[r3240sx]

skyper i think your missing the point, my car has always had the same clutch, so any changes i made i could tell the diference... regardless of the clutch being lighter than stock.

i will be installing stiffer valve springs in my new motor, either tho the car didnt suffer audiable valve bounce and only died because of a broken ring land. and mine are bigger than 8.9mm lift

Mike you dont have too upgrade them.

BTW, stock valve lift is either 7.5 or 7.8, I think they are 7.5 but I've seen both figures.

Yours are 1mm higher than stock, and that will not require upgraded valve springs unless you rev it out pretty high.

I have tomei 256/256 8.5/8.5's and I rev to 8, have been for a while now. Stock springs.

I too am curious as to how the 272's work, as mine are pretty mild.

Good luck

-Max

[SKYPER]

335, you don't need to upgrade the valve springs. It's an option if you have to replace stock valve springs, due to age.

AD4M you are correct, they are 9.0mm lift -

http://www.hks-power.co.jp/products/engine...shaft_data.html

Stock cams on R32 RB20DET are intake 240 duration, 7.8mm lift / exhaust 240 duration, 7.8mm lift -

http://www.tomei-p.co.jp/_2003web-catalogu...haft-specs.html

Anything from 260 duration+, it seems engine loses power at bottomend but gains mid to high.

Roy, 256 duration seems to give a near to stock cam / turbo powerband (slight drop in bottomend) on a SR20DET

with a Garrett GT2871R turbo, upgraded clutch/flywheel, upgraded exhaust manifold, etc -

SR20DET dynograph

256 duration should gain more power at the same boost level. I think someone said in the RB20 dyno thread,

it was roughly a 18rwkw gain at 1.25 bar??

Edited April 18, 2008 by SKYPER

[AD4M]

sr20det rb20det not same, chalk and cheese comparison! read Roys post on valve area to engine size and i think you'll understand a bit more where im coming from. the sr20 will act diferently to an rb20 with modifications.

im pretty sure mine are the older style hks cam, bigger than 9.0 im pretty certain there 9.1 but i'll have to do some measurements when we take them out, either way there the biggest lift drop in cams available out of japan for the 20. we set them up at TDC and on the dyno only adjusted the inlet cam 3 degres advance and saw the whole power band shift foward a fair bit. spewing i didnt get that printed out aswell!!

[SKYPER]

I gather I was looking at the 2 litre capacity, not taking into account the valve area, etc, as mentioned in Roys post.

Also I remember someone saying the RB20 has to rev more than a 4 cyl???

Maybe more agressive cams might suit RB20???

[Roy]

What do you mean by more aggressive cams? Think about how an engine works and what it needs to work, then consider what large duration and lift cams do to an engine that doesnt have variable vaalve timing and onl 2L of low compression displacement

I wish i had the money and time (expertise) to play with cams. I tried 260/8.8 cams and the results were not great. Witha bit of tuning i was able to get back most of the top end that i had lost, but was never going to get back the bottom to mid. At this point i pulled the pin.

Thinking back, it was a bit optomistoic to think a little RB20 with a big compressor but smal exhaust housing was going to get a lot from cams with such an increase in duration. Going back to basics...i may have got more out of the setuyp if i had a bigger exhaust housing!?!?!

Dont know for sure. Needless to say though i am with others when i dismiss what SR20s need to work. They have rocker arms, different comrpession and head designs, different inlet manifolds not to mention they are a 4 cylinder. Too many variables.

For the time being i am just waiting until i can find out a bit more about water/methanol injection. Then i may consider soem 256 cams, a change to a 10cm exhaust housing then a re0tune with as much ignition as the engine can hanle. See if i can bag a usable 280rwkws at 22psi out of a std RB20 bottom end. At the moment i cant make any more power because of injectors and i dont thinkk the little 8cm housing is liking th eboost/exhaust flow