stroking the rb20det, pros/cons?

[kwazza11]

anyone had any experiance with stroking the rb20det to 2.4 with the 26 crank/rods?

i'd like to know how it behaves compared to the rb25det, what its torque curve's are like, and can you retain the factory ecu? things like that.

anyone done this conversion as i see it as a very cheap and profitable upgrade, the only costly thing being (as long as you can run it on the factory ecu or power fc) would be the pistons.

rb26 crank/rods = $300-400

machining = no more than $200

pistons = ???

pistons i cant see costing more than $2000, so compare this to upgrading to a rb25 ($3000) or 26 ($6000) and it seems pretty enticing, considering you'd rebuild it for little extra cost (price of bearings, gaskets and seals) and rather than have a used motor that you dont know much of its previous life, youd have a fresh 2.4 with plenty of strength for some big boost.

any opinions or personal experiances?

Karlos

[Clint32]

At the moment in tossing up if im going to do that or build a rb30. About 2.3L is the max you can i belive before you get into trouble. It should be fine to run on the stock ecu but i have only just started thinking about this so i cant help you any further. I know others have looked at doing this so hopefully they will add and help us both.

[blind_elk]

machining - you forgot a '0', try $2G - that's the indication I got from a machine shop to balance everything up for a rebuild. Doesn't include boring for the bigger pistons.

I'm planning to rebuild my 'old' engine (it spat a chunk out of #1 piston). The Toyota pistons (4AGE or 4AGZE, no-one can confirm which) seemingly cannot be got (new) for love nor money (if you're lucky, you might be able to pick up a S/H set from somewhere). Otherwise you'd be stuck with an expensive Tomei or similar set. I'm planning to just get a set of 1mm oversize 'standard' pistons.

You should be able to utilise the R32 ECU, because it can be re-programmed if necessary.

[kwazza11]

machining will only cost a minimum as i have most of the machining equipment at work and can do it myself, the boring is the only thing i need to outsource and i can get the company we use to do it at cost price. the motor will only make max 300kw at the fly so i wont go over the top with cc'ing, balancing and blueprinting etc.

whats this about toyota pistons? are they the right size to suit the stroker? are the gudgeon pins the same diameter?

or did i read into that too much and you just mean your rebuilding a toyota motor?

if i can get the dimensions necisary i'll email a few piston places and see if they can find a suitable piston.

however is it either 80.5mm or 82.5mm? and what about piston height?

[blind_elk]

Well, having all the gear certainly makes a difference.

I was referring to the 80.5 mm pistons - there's some confusion as to whether they are 4AGE or 4AGZE pistons. As far as I can ascertain, they basically 'bolt in'.

I had a mate in Toyota searching for them - but it seems they no longer exist. And the Lotus boys who run 4AGE engines in their clubmans can't seem to find any either.

[kwazza11]

well i found some info

http://www.toysport.com/catalog/parts%20by...engine/4AGE.htm

these guy say the OEM pistons for the 4AGE are 81.5mm (although they have hks pistons that are 81.00mm)

http://www.club4ag.com/faq%20and%20tech_pa...cifications.htm

http://www.club4ag.com/faq%20and%20tech_pa...A-GZE_specs.htm

piston pins can be either 18mm (80's 4age) or 20mm (90's 4age and 4agze)

cant find any info on the pin size for the rb26det though, anyone know?

[CRSRB25DE]

afaik all RB series engines have 21mm (.827") wrist pins

[gts4diehard]

hi, check out the tomei site, it gives you all the info, except you need their pisotns of course...

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

[gts4diehard]

The wiseco catalogue shows some of the toyota pistons they do, not sure of pin location but maybe worth checking out, from the american site.

got some prices in us $$ from http://www.pistons-online.com/sport.asp?ma...ta&st=48&end=48, prices for piston kit i.e. rings too.

they have gtr pistons for $870 K551M88 (88mm)

celica 2ZZ (also Pontiac Vibe)

K569M82 82.00 / 3.228 both 20 mm pins $580

K565M82 82.00 / 3.228

Celica/MR2 4AG

K533M82 82.00 / 3.228 .040 (18mm pin) $580

K505M82 82.00 / 3.228 .040 (19 mm pin) $580

K506M82 82.00 / 3.228 .040 (20 mm pin) $580

[Fitzpatrick Speed Works]

rb30 way better option at half the price!!!

[Mandingo]

^^ Agreed

[Ahh32]

or you could just put the 20 head on a 25 block, i have put the 25 headgasket on the 20 head and everything lines up except a few water and oil holes which need to be made a bit bigger, other than that all the head bolts ect line up perfectly.

even better buy a RB25 Na from a R32, use the 25 bottom end with the 20 head. and the 25 head with a 30 bottom end. then u can choose which one u want

[FATGTS-R]

I have also breifly considered doing this and from what I understood the toyota pistons needed are from a toyota 4agze as they are forged and ceramic coated to suit the factories supercharger.

But I beleive there were two different compression ratios in the gze, hence two different types of gze piston and there is also an issue with pin height.

Where can you get an RB26 crank with rods for $300???

Anyways, this has been covered many times and there is more info hiding under the search button. Try RB24/23 etc.

[nedb]

Would the R32 RB20 det head fit without mods on the R32 RB25 de bottom end?

[browny]

AFAIK the std 4AGZE pistons are 81mm with a 20mm pin.

With a RB26 crank this gives around 2300cc

The RB26 rods have a small end of 21mm, so they need to be bushed if using the Toyota pistons.

Regarding availabilility of the 4AGZE stuff, when I looked into this last, there was a thread on Toymods that said the pistons were available through Toyota, however most dealers didn't want to help. From memory they were ~$120 each.

I think the head also needs some work to suit the increased bore. There will also be some fiddling with combustion chamber & deck height to get the desired compression ratio.

RB26 crank and rods seems way cheap for $300-400. I'd be budgeting more like double that.

A new oil, water pump and new fasteners would probably be worth factoring in as well.

[RB30-POWER]

You should think about this for a minute too.

If you make a RB20 2.3/2.4L you will still have the standard RB20DET head, where the standard valves will cause a potential restriction with the larger capacity motor.

If you got a standard RB25, already you have extra capacity, and a fair increase in valve size.

If you have the smaller 20DET head with the larger capacity, its a sort of flawed idea from the beginning.

Only my 2c.

If you want effortless torque and power build a RB30DET. (You will never look back at smaller displacment motors again)

[kwazza11]

that $300 for crank and rods was a price i got off someone in the for sale forum, look around and you'll always find a bargain.

in the end i just bought a 31 with the rb24det already in it.

but seriously the main reason for doing this isnt to make huge power, think about it, instead of spending 3k on a second hand motor with no service history and having to go to the trouble of changing engine no's and engineering engine swaps, you spend 2k and get a fresh motor. (spend the left over on better breathing cams or head porting?)

besides, theres plenty of rb20's with standard heads making close to 300kws

[DLuded]

if ur after 4agze pistons there are 4 at

http://forums.toymods.org.au/index.php?t=m...00a7e297afecbc6

just try and get another 2 somewhere