Lewis Engine 2.2 Stroker Rb20

[eightsixboy]

The idea of a 500 wrecker motor i read above, best solution.

2.2 is a lot of money considering what you get if you are after a rebuild etc. Look at the TD06 / RB20 guys making a nice 250-260 on stock motors, would be the economic choice as the 20, even 2.2... won't have 'that' much more down low etc.

As stated also the major issue is the head when it flows around 30% less than a 25 head from most info posted.

So would maybe just some decent head be best for some better response and more mid/top end?

Either way I wanna pull the head of and get it cleaned while the motor is out, replace all the hoses and seals.

[R31Nismoid]

Decent head always gets a good response...

Seriously though spending money on a 20 head is a waste. They are fine for stock capacity upto the 260-270 mark which we've seen plenty of users do.

So i wouldn't be spending the money there at all.

[wlspn]

If you're looking at rebuilding have you considered buying a blown RB25 & freshening that up?

Might not be as dear as you seem to think. Wiring can be done cheap (can point you in the right direction there if you need), tailshaft can be done cheap, gearbox mount nearly free, may be able to re-use your turbo unless its already running out of puff on the 20?

At least ring around & get some prices & compare that to what you will spend on this 20/22.

Will end up with a slightly later model base engine, more capacity ( torque), VCT, better flowing standard head, etc. In my opinion well worth it if you can....

[eightsixboy]

Decent head always gets a good response...

Seriously though spending money on a 20 head is a waste. They are fine for stock capacity upto the 260-270 mark which we've seen plenty of users do.

So i wouldn't be spending the money there at all.

Ok thanks, thats exactly what I wanted to know.

[femno]

Ok so it seems you want more response and low-mid power? The "Race Port' head will most likely make this worse.

Then bin the 20, itll never get any better than what it is now if you want to make some decent power and maintain response without needing a 3k high mount (awesome for legal type stuff) turbo kit.

Also keep in your mind engines built by nissan will last longer and be better than 90% of engine assembled by 'professional' engine builders at your power goal, let alone messing about with it yourself if thats what you plan to do.

The 25 conversion is easier than you think, if you talk to people who have done it before and know exactly what to do its really very easy all you need to know is how to remove and replace an engine. Legality wise its not much of an issue either, there are several solutions there. The 20 box will last if youre nice to it and maintain it.

[sav man]

Only RB20 i've ever driven with headwork is really laggy, and didn't make staggering power (260rwkw). There is a 300rwkw RB20 in tassie, and it's a unopened wrecker RB20 + GCG XR6 Turbo. The RB25 head flows more because it's got 25% more capasity.

[dorifticon]

Whether you go with the Lewis engines option or do it yourself, I can see the advantages to retaining the stock engine block, even if purely from a block fitment/legality point of view.

Fitting taller engine blocks in r32's always ends up being a pain in the ass.

Also, going from a 2.0 to a 2.2 is, in my view, not worth 'stuff all' especially in the driveability stakes - its a 10 per cent increase in swept volume. If you have the engine apart anyway IMHO it's not a great marginal increase in effort/cost.

So I think I understand where the OP is coming from.

My only suggestion would be, instead of trying to make an rb20 head flow, is there some way of grafting on an RB26 head? You get solid lifters and bigger cams, and they're pretty cheap these days. And you known they flow awesomely. Also it gives you the side entry plenum (I presume you are, or are going to be, running a FMIC).

Otherwise the rb25 with vct could be a goer.

I know there were problems putting small-bore heads on big-bore rbs (ie putting rb20 twin cam heads onto rb30s) but is the problem the same in reverse? ie if running an rb26 head on a small bore rb20 block would it be neccessary to take the bore out or modify the head or some combination of the two?

[R31Nismoid]

yeah same issue with 25/26 heads on a 20. of course money solves everything but that's against the point here as there is clear budget.

I see what you mean by 10% extra, but then look and what you get with a 25. More again in every area. If you did cost vs gain, the 25 beats rb22. For maybe 1500 more you get 15%, rarely do you get gains like that on economy of scale in performance.

Realistically there are no legal issues, and its not height problems like a 3ltr.

I still vote wrecker 20 for super budget.

[sav man]

+1 wrecker motor. From first hand experience headword and/or cams only make a 20's worse

[Roy]

... to standard rb20 as the two resitictions are the small cc and non flowing head

A few people have commented on this and thought I would throw in my 2c. The non flowing head, rather then looking at a total number of cfm etc. Consider what volume each cylinder displaces. Then remember for good cylinder filling you need good velocity to give you torque and a usable power band. You happen to be limited in valve size in part by the bore and combustion chamber size, but its all related. You want small ports for small amounts of displaced volume so you have good velocity and cylinder filling and effecient combustion.

So, I posted a similar thing a while ago in another thread. When you consider the surface area of valve between an SR20 and an RB20 you will find that as a ratio of displaced volume per cylinder...(500cc SR20 vs 333cc RB20) you will find the RB20 has more valve area then the SR20. This is perhaps why the RB20 performs better up to 260-280rwkws then SR20s when running std inlets, cams etc as given their displacement they plenty of cam from the factory for a 2L Six

So for a 2L it flows just fine. If you want 400rwkws out of an RB20 say, then you are only going to make it with tonnes of revs and boost. Think about one cylinder of RB20 that spins one complete revolution. It only displaces so much air to mix with the fuel that gives you the power. The only way to cheat that is to give it more boost to squeeze in more air to mix with more fuel for more bang/power.

Now think of an engine that runs for a minute and consider the engine as being a pump that moves air and fuel. If you have a smaller engine then the only way to match the volume of air and fuel being consumed to make power is with more revs. So that is the catch , you need to spin the RB20 harder to make the power, which is no real sin as with a short stroke, a small light piston and similar bearing sizes the RB20 is better capable of handling the bottom end loads you see with revs, well better then the RB25 and RB20 (all things being equal)

A thing to consider is even when comparing to RB30s, if you have a small 250rwkw turbo on one they may not want to do much over 6,000rpm. The same turbo on an RB20 may make the same power but need to spin up 8,500rpm to do it. So as far as power bands go the RB30 may make 230 to 250rwkws between 3,500rpm and 6,500 rpm (3,000rpm power band) and the RB20 may make 230 to 250rwkws between 4,500rpm and 8,500 rpm giving you a 4,000rpm power band to work with.

Truth is that isnt the perfect case as torque etc delivery will be different, and RB30 would smack an RB20 all round generally...but its food for thought and a different way to view things. Especially if you are looking for economic performance that means when you are up it...its quikc. If you want to take 40km/h corners in 3rd gear or accelerate in any gear rapdily then an RB20 is never going to do it.

I am dubious if there is much you can do a std RB20 head to improve response on its own. If you clean up and match port things then you can perhaps make the engine a little happier to take ignition which will help drivability. Maybe with an RB25 like 9.0:1 compression rather then the std lower compression RB20 it will help drivability. There are a few things that can help, but this can be achived cheaply just by running a better quality fuel that allows you to put a better tune in a std motor.

My advice, dont rebuild a running motor! If its blown then there are a few things you can do like discussed above, and a set of oversized pistons with a bump in compression and match porting with the right bolt ons would make for a decent enough thing.

On a sidenote, i have often wondered what the different would be in an RB20 with 9.0:1 compression and an RB25 turbo and a std RB25 engine. Would be interesting

[eightsixboy]

Yea I was also thinking of raising comp a little. But surely it isnt as easy as just getting a thinner head gasket?

I wonder why they made comp lower then the 25? You would expect it to be the other way around, the rb20 needs all the help it can get really.

Edited June 1, 2011 by eightsixboy

[Roy]

RB20 is a generation older. Designed at a time when moving over from leaded to unleaded. Slower processing speeds from ECUs meaning less control over combustion. Turbo technology was evolving and fair to assumed that with every later model of engine came a superior turbo with regards to flow and inlet temps. Not to mention the RB25 has variable inlet timing....its simply a generation newer and with that comes better control over detonation

[Roy]

double post

[eightsixboy]

True True.

Do you think a higher comp ratio would make that much difference?

If its just a matter of shaving the head a little and a thinner gasket I'm surprised if no one has done it before on a 20.

[sav man]

High comp pistons would be the go

[dorifticon]

High comp pistons would be the go

I agree, based on experience with L6 engines (admittedly in NA form) it really helps driveability.

with today's modern ecus and more reliable fuel quality an rb20 should be able to handle a bump in compression and still run decent boost.

[Nee-san]

Only RB20 i've ever driven with headwork is really laggy, and didn't make staggering power (260rwkw). There is a 300rwkw RB20 in tassie, and it's a unopened wrecker RB20 + GCG XR6 Turbo. The RB25 head flows more because it's got 25% more capasity.

Not entirely correct, the flow capacity of a head isn't linked with the swept volume of the engine ??

It has to be head design with the RB20, you can't go around saying 2 Litres isn't enough because we all know that just isn't the case.

[n8ive.2.oz]

Hi - I have just had a rb22 built by Darren from Lewis Engines.

Should be going in the next week or so.

I will let you know dyno figures asap.[9242.jpg]

[DR 32R]

Nice looking rb22, I'll be interested in how it gos.

[StevenCJR31]

Whether you go with the Lewis engines option or do it yourself, I can see the advantages to retaining the stock engine block, even if purely from a block fitment/legality point of view.

Fitting taller engine blocks in r32's always ends up being a pain in the ass.

Also, going from a 2.0 to a 2.2 is, in my view, not worth 'stuff all' especially in the driveability stakes - its a 10 per cent increase in swept volume. If you have the engine apart anyway IMHO it's not a great marginal increase in effort/cost.

So I think I understand where the OP is coming from.

My only suggestion would be, instead of trying to make an rb20 head flow, is there some way of grafting on an RB26 head? You get solid lifters and bigger cams, and they're pretty cheap these days. And you known they flow awesomely. Also it gives you the side entry plenum (I presume you are, or are going to be, running a FMIC).

Otherwise the rb25 with vct could be a goer.

whats the clearence issue with taller (ie RB30E) in a r32? bonnet to manifold?if so how do you get around this?

I know there were problems putting small-bore heads on big-bore rbs (ie putting rb20 twin cam heads onto rb30s) but is the problem the same in reverse? ie if running an rb26 head on a small bore rb20 block would it be neccessary to take the bore out or modify the head or some combination of the two?