RB20 Rebuild questions.

[TokyoTaxi]

Roy,

That's what I'm planning on doing but the questions are how much do I take off the head to retrieve the lost compression and how much CAN I take off the head before the pistons and the valves start having sex? ( Not actually asking because cause I get the feeling that nobody can actually answer those questions ).

rb20-calais,

Tried running more boost through the GT2530 but it seems peak efficiency is 1.4bar and anything after that is just hot air.

RedDrifter,

The GT2835 would have to be my choice also if I didn't know any better ( which I don't ).

Then the problems are 1: Do I get a GT2835, a GT2835R, a GT2835Pro or a GT2835ProS ?2: What wheel trim and A/R do I get and 3: How much is it going to cost ?.

Every day I get one step closer to selling this car !!

[rb20-calais]

thats very interesting a lot of people say the hks turbos are efficient @ 1.6bar+, the max boost i was going to run with the 2530 was 1.4bar so that makes me happy i have selected the right turbo. Could you tell me what power you made @ 1.4bar with the 2530 ?

Evan

[TokyoTaxi]

On my stock motor ( before it went belly up ) with a programmed ECU and a set of 550cc injectors ( overkill ), GT-R fuel pump and pressure regulator, running 1 bar boost I was making 207.3 kw at the wheels. I never wound the boost up for fear of blowing the head gasket ( I'm told that 18psi is the smart maximum for a stock head gasket ) but then again I WAS happy with 207.3 so never saw the need to crank it any further.

Just my opinion but I think the GT2530 is one of the best turbo's available for the stock RB20DET and the GT2535 for the stock RB25DET.

[Roy]

So FAT32, has the ECU been remapped since the engine rebuild?

[Chris32]

On my stock motor ( before it went belly up ) with a programmed ECU and a set of 550cc injectors ( overkill ), GT-R fuel pump and pressure regulator, running 1 bar boost I was making 207.3 kw at the wheels. I never wound the boost up for fear of blowing the head gasket ( I'm told that 18psi is the smart maximum for a stock head gasket ) but then again I WAS happy with 207.3 so never saw the need to crank it any further.

Just my opinion but I think the GT2530 is one of the best turbo's available for the stock RB20DET and the GT2535 for the stock RB25DET.

What caused the need to rebuild it?

I am about to undertake the next phase of my project, as mine has been making 200rwkw for about 14 months now and I am bored with it, and I am hoping for around 220rwkw reliably out of the stock motor

My dillema is that is the motor dies is to either -

1) Rebuild my motor with forged pistons and INCREASE the CR to 9.0-1

2)Replace my motor with a low km one form the wreckers

3)Bin the RB20 and replace with RB25

So just interested in why it needed to be rebuilt

Regards, Chris

[Roy]

i think a bottom end bearing called it quits, oil pressure/surge related

[TokyoTaxi]

Roy,

Yes, the ECU was re-mapped on the dyno ( same dyno I always use ) and the tuner just couldn't get the power out of it.

Chris32,

I had to rebuild my motor as the number 4 big end bearing failed and the oil pump rear cover had come lose. Otherwise she was a sweet engine.

[Cubes]

I've just been quoted 5,600 for a complete rebuild, bit more if i wanna chuck the tomei forgies in.

What does that include? Mild port/polish & rebuilt head?

My Rb30DET bottom end cost me $3738.50.

Crank, rods & block crack tested.

87mm Wiesco Forged pistons.

Blue Printed.

Balanced 1 to gram.

RB25DET Oil pump clearances checked & re-assembled WITH lock tight!!!

Head fitted & valve clearances checked.

Cam belt inc. fitting of it.

Tensioner relocated above water pump.

Cometic Metal headgasket (O-ring setup around bore).

The head was ported polished & rebuilt by Chris Milton Engineering. It cost me $880 + $80 because they missed a protruding exhaust valve seat in no. 5. (& they wonder why I didn't get the bottom end built there) + $275 for the vrs kit that contains the valve stem seals (if purchasing just the valve stem seals it will set you back $330 from memory) So get the VRS kit. It comes with complete top end gaskets (head gasket, plenum, exhaust, inlet etc).

So all up that would be $4973.50.

I found the little so called performance shops were so damn expensive it wasn't funny. I ended up going with a larger company 'City Dismantlers' that deal with everything from second hand parts, new parts, trimming, engine rebuilding & painting hence everything you can think of they do. They had new clean machinery. They had built up in the past many hi-po VL's with one that he mentioned made 718hp which used an aftermarket crank cradle, h-beam rods etc. He was also in the process of a supercharged 400 chev build that will run a cr of 7:1 and make some where well over 700hp.

I was quoted up to $5500 to have just the bottom end worked with the same specs as above.

So shop around.

[TokyoTaxi]

Well,

Just to keep the info alive re my original problem, I've just found out that the 40 thou oversized Arias forgies that were fitted are 8.3:1 comp ratio. Most people are saying the stock is 8.5:1 but some are saying it's 8.7:1. I guess anyway you look at it, I need more air flow / boost so I guess I'm looking for a GT2535

Does anyone know if the dump pipe that suits a stock turbo will suit a GT2535 ?

Also I guess the same question with regards to a GT2835Pro ?

[Cubes]

Tilbrooks told me anything over a 2530 with a RB20t is pretty usless for the street. On the dyno loaded up in fourth it made full boost at 3700rpm. So on the street you could easily say maybe 4200rpm?!? Any one know where it makes say 1.1 bar accelerating from low rev's in second or third?

lag lag and more lag.

I hate lag.

[TokyoTaxi]

Tilbrooks told me anything over a 2530 with a RB20t is pretty usless for the street. On the dyno loaded up in fourth it made full boost at 3700rpm. So on the street you could easily say maybe 4200rpm?!? Any one know where it makes say 1.1 bar accelerating from low rev's in second or third?

 

 

lag lag and more lag.

 

I hate lag.

Hmmm. Does the same go for a modified RB20 ? ( Keeping in mind I've had head work done and the pistons )

[RedDrifter]

Put a stage 1 or 2 cam in it aswell and id say lag would be a lot less compared to a stock motor especially with your head being ported and all.

As for a GT2835proS the flange is fine I think(t3) but as for the exaust outlet I'm not sure.

[Cubes]

Yer maybe slap a NA 232dur 7.3mm inlet cam and a 264 dur exhaust cam or maybe a 256 depends on what sort of results others have had with cams in the rb20t.

If it doesn't work to well then step up the inlet cam a little. Stepping up the inlet cam will generally loose power down low UNLESS it is something like a RB30 running RB25 cams then up to around 260dur inlet it will pick up power down low. Well thats what Dyno2003 says anyhow.

2530 is the the happy medium 'apparently'.

2535 isn't much bigger and would possible knock 240rwkw as i've heard 2530's making 230rwkw?!?! I don't really know though.

[Roy]

I dont think you can say a certain turbo is useless on the street-its really down to the driver and their needs.

My car is fine on the street with what I consider to be the biggest turbo you would use on a std RB20. Boost really kicks in around 4,500rpm, whilst under that its still has enough power to get around, id guess it would have about 70-90rwkws of boost which is plenty of power the get around...BUT not if you want to race around on the street, then it would be shocking to drive.

On the track though where the revs are always in the required range, then its not a problem. Im having to change my driving style a little, where on slow corners i now use 2nd gear and have to be mindful that while rowing back thru the gears i dont wash off too much corner speed. So whilst i would love a torque moster RB30, when i think about what i need my car to do it works fine for me.

Id say the little HKS 2530s are supposed to be good at high boost levels. so just keep winding boost into the engine while on the dyno until it stops making power. See how you go at 1.5 bar, with your upgraded fuel system and forged pistons and tuned ECU, you should be able to maintain the boost response of the smaller turbo with the airflow capabilities of running higher boost.

blah,blah, blah...basically give it a hit at 1.5-1.6bar to see if it makes the power you want from it, if nbot then think about other mods/turbos.

...oh and Joel do you want ot play with some cam specs for me, http://www.skylinesaustralia.com/forums/sh...ead.php?t=35221

[Roy]

When tuning it what is the reason it wont make more power? Is it overly sensitive to pinging? Was just thinking on the weekend that if the head has been ported perhaps the squish zones have been altered and the combustion chamber has hot spots????

[TokyoTaxi]

Roy,

Pinging is not the problem. It's just not making the oomph. Anyway, I'm going to try another turbo which I think may help a long way towards fixing the problem ( it better !! ).

Will post the results if all goes well. If not, the car is history !