Ultimate Na Rb20

[zebra]

As weve been saying this whole thread lol

[SKiT_R31]

Yes, but he has said it multiple times that he isnt going to change his mind, so none of this is contructive.

[mad082]

we were trying to be constructive by telling him that if he wants to build a race car that will be competitive then he is using the wrong engine. this isn't just some poser car he is building, it is a race car, and the whole idea of racing is to win, or at least do the best you can. no point building some massively expensive engine if for a fraction of the price you could build a lighter engine that puts out much more power.

[zebra]

we were trying to be constructive by telling him that if he wants to build a race car that will be competitive then he is using the wrong engine. this isn't just some poser car he is building, it is a race car, and the whole idea of racing is to win, or at least do the best you can. no point building some massively expensive engine if for a fraction of the price you could build a lighter engine that puts out much more power.

Exactly!

Considering IPRA is one of the most closely fought race series around, Any advantage should be exploited.

[Galois]

just wondering, do they have a division for turbo skylines? or at least 30L NA? just thinking that you're going entry level skyline engine size vs top levels of other brands...

definitely interested to see how much power you can get out of it tho mate

[Chris-06R]

Thanks for some more constructive replies, not sure where I said I wouldn't change my mind, so I'm all ears for options. SR20 power is proven in U2L IPRA so I agree with everyone that says its a better choice and easier to make NA power. But then, since I'd be running a Pulsar motor, I may as well put it in a pulsar which is probably lighter anyway.

To those who keep suggesting other motors and classes, IPRA is split into 2 classes, Under 2L and Over 2L. If you run a turbo car you must run an intake restrictor and you must multiply your capacity by 1.7, moving almost every turbo car into the Over 2L category where you go up against Natro 5+L commodores and falcons, and of course the benchmark rotary Rx7s.

Sticking within the 2L class should keep costs lower (though maybe not by running a trailblazing Rb20).

Would putting an sr20 into a gts-t be considered sacreligious?

[Galois]

just wondering, and sorry to stray a bit off topic, but why is it easier to get power from an sr20?

[mad082]

because of the VVL head. the power they make from stock with a few very minor mods (ecu, cams, etc) will be as much, if not more than a rather heavily modified rb20.

look at the stock figures (of the most powerful versions of each).

rb20: 114kw, 186nm

sr20ve: 152kw, 206nm

the sr20ve puts out more power (but less torque) than a rb25de. even the autech version of the sr20de put out 150kw (the one that came in the autech s15).

there are plenty of people on the pulsar forums with ve motors who are making up to around 130kw at the wheels with relatively stock motors (just a tune, exhaust and some with cams). a few guys have gotten the n1 cams out of the sr16ve n1 motors to put in them, but so far i'm not aware of anyone who has actually tried to build a high powered one yet. also comes down to which of the 2 versions of the VE motor they use, as 1 is only around 139kw at the fly stock.

[-Jimmy-]

I haven't seen it happen a lot around here (Australia) but I have seen SR20 conversions done a lot in Japan.

I think it would be interesting to see you go ahead with a build like this, especially being NA. Good luck with it all

[SKiT_R31]

Thanks for some more constructive replies, not sure where I said I wouldn't change my mind, so I'm all ears for options.

OK cool, that’s my bad.

Right, questions on comparisons then

Yes stock for stock, the SR20, especially SR20VE is miles ahead. But that’s because its been more worked from the factory, which means you wouldn’t be able to squeeze as much power out of it, compared to a rb20det, which lets face it, was pretty crap out of the factory.

OK, so first I just want to ignore the obvious weight and size/overhang differences, just worry about power.

The RB20DET has a shorter stroke and is a 6cyl, which is better for quicker engine acceleration and higher rpms. The SR20DET with its longer stroke will be more responsive at lower revs.

The RB20DET has a 30mm inlet valve and 27 mm exhaust valve. Now yes, these are small when compared to the RB25/26's, but when you compare it to the SR20DET, they are actually bigger... If you calculate the total area of the SR20s 8x 34mm valves VS the RB20s 12 x 30mm valves, SR has 7263mm2, RB has 8482mm2, that’s 15% larger in the RB's favour. Its the same with the exhaust, 8x30mm on the SR vs 12x27mm on the RB = 5655mm2 & 7389mm2, That’s 24% larger once again in the RB20's favour.

Now I don’t know how much you can get out of the SR's, but I would have thought, with access to RB25 valves etc, maybe again in RB20's favour?

The SR20VE has an 11:1 compression ratio? Now I don’t know about their squash efficiency in comparison (which may ne negated if both had equal headwork anyway, to open the combustion chamber etc) but the RB20DE has 10:1 compression, so there's one reason to it being lower in power, so both engines should hit a similar compression limit on your chosen fuel, but the RB20 will have the bonus power (when compared to stock outputs) by having that extra 1 atmosphere on top.

The SR20VE has 10.7mm lift, 264 duration. Stock this gives it a lot more power, obviously - compared tot he RB20's weak 7.8mm lift with 240duration (i know there is more to it than this, but I’m trying not to get too messy with complications). So once again, I see this as a limit on the SR, but in comparison a bonus for the RB, since there is only so far you can go, the RB can handle a massive upgrade over stock, where the SR can only make small improvements with after market (though the RB20 head would have to have a some headwork to support such extreme cams).

I wont bring management into it, as both will become full after market (one would assume) so same kettle of fish there.

Of course The SR20 has VCT, but with serious cams, could/would you keep it?

They both have a lot of aftermarket support for water/oil pumps, etc (thanks to turbo boys) with the SR having more options with using pistons for compression (rather than block & head skimming)

Also, there are a lot more people working N/A SR's, compared to RB's, so there is a lot more information out there.

So really, as I see it, you should be able to get similar power from each motor, due to benefits on both sides. Really the only gain I see to using SR, is the less overhang & weight, but that comes at the cost of locating the engine, making it fit and wiring it in to the chassis loom/instrument cluster gauges etc. (so more time and money).

Edited May 24, 2010 by SKiT_R31

[Chris-06R]

Awesome comprehensive reply, some good points there...

The VVL head is obviously key to generating decent power in the VE, but you would think in a race motor by matching the cams to everything else, and then running the motor in its optimal power band you would mostly make up for having variable timing...?

As you said the biggest problem with the rb20 is the weight - can't do much about that. That said, why go to all the trouble of fitting an SR into a skyline when there is already a 2 Door Rwd coupe that needs no mods - i.e. a Silvia (which has been proven to be pretty successful in IPRA). Half the fun would be doing something different... which brings me back to the point of this thread - trying to decide whether it would have half a chance of working or whether it would be a complete waste of time and money.

[XRATED]

I think you'll find you will get more revs out of a correctly built 20 as compared to an SR- shorter stroke and smaller bore.

Basically light is fast.. The lighter you can get the liner, the better your brakes will work and the more effective your hp will be. An na 32 dosn't give up much weight to a silvia... just give your car and yourself a diet!! ha ha ha

Look at keeping your rolling resistance low too.

[iseekool]

OK cool, that's my bad.

Right, questions on comparisons then

Yes stock for stock, the SR20, especially SR20VE is miles ahead. But that's because its been more worked from the factory, which means you wouldn't be able to squeeze as much power out of it, compared to a rb20det, which lets face it, was pretty crap out of the factory.

OK, so first I just want to ignore the obvious weight and size/overhang differences, just worry about power.

The RB20DET has a shorter stroke and is a 6cyl, which is better for quicker engine acceleration and higher rpms. The SR20DET with its longer stroke will be more responsive at lower revs.

The RB20DET has a 30mm inlet valve and 27 mm exhaust valve. Now yes, these are small when compared to the RB25/26's, but when you compare it to the SR20DET, they are actually bigger... If you calculate the total area of the SR20s 8x 34mm valves VS the RB20s 12 x 30mm valves, SR has 7263mm2, RB has 8482mm2, that's 15% larger in the RB's favour. Its the same with the exhaust, 8x30mm on the SR vs 12x27mm on the RB = 5655mm2 & 7389mm2, That's 24% larger once again in the RB20's favour.

Now I don't know how much you can get out of the SR's, but I would have thought, with access to RB25 valves etc, maybe again in RB20's favour?

The SR20VE has an 11:1 compression ratio? Now I don't know about their squash efficiency in comparison (which may ne negated if both had equal headwork anyway, to open the combustion chamber etc) but the RB20DE has 10:1 compression, so there's one reason to it being lower in power, so both engines should hit a similar compression limit on your chosen fuel, but the RB20 will have the bonus power (when compared to stock outputs) by having that extra 1 atmosphere on top.

The SR20VE has 10.7mm lift, 264 duration. Stock this gives it a lot more power, obviously - compared tot he RB20's weak 7.8mm lift with 240duration (i know there is more to it than this, but I'm trying not to get too messy with complications). So once again, I see this as a limit on the SR, but in comparison a bonus for the RB, since there is only so far you can go, the RB can handle a massive upgrade over stock, where the SR can only make small improvements with after market (though the RB20 head would have to have a some headwork to support such extreme cams).

I wont bring management into it, as both will become full after market (one would assume) so same kettle of fish there.

Of course The SR20 has VCT, but with serious cams, could/would you keep it?

They both have a lot of aftermarket support for water/oil pumps, etc (thanks to turbo boys) with the SR having more options with using pistons for compression (rather than block & head skimming)

Also, there are a lot more people working N/A SR's, compared to RB's, so there is a lot more information out there.

So really, as I see it, you should be able to get similar power from each motor, due to benefits on both sides. Really the only gain I see to using SR, is the less overhang & weight, but that comes at the cost of locating the engine, making it fit and wiring it in to the chassis loom/instrument cluster gauges etc. (so more time and money).

Just to add to that since the RB is a short stroke inline 6 - It should theoretically be able to "rev up" faster and smoother as inline 6s are "perfectly balanced" - compared to a 4 cylinder

@ SKiT_R31 for the excellent N/A info - Bit off-topic are you a mechanical engineer (or something along those lines)?

[Finny]

I agree with SKiT_R31, Also you have to remember engine wear. People will defend SRs to the ends of the earth especially thoes who drift them but I think you will get much less problems with bearings etc. with an RB20. High compression is hard on the crank bearings and I know there are things that can be done to the SRs to make them more reliable but you probably wont have to worry so much with an RB20.

SKiT_R31 also has an RB30 twin cam non turbo which was dyno'd quite some time ago at 151RWKW but that was on a really bad tune and before a lot of other mods. I wouldn't be surprised if it pulled over 180RWKW when it next hits the dyno and being that he has been building this car for many years he does know a lot about NA power. Makes me laugh when this car spanks turbo'd cars.

Edited May 25, 2010 by Finny

[zebra]

If you want to be at the pointy end of the IPRA U2L field, than engine wear is way down the list of things to worry about.

A high comp NA engine will be way easier on bearings than even a Low comp turbo/supercharged engine,

Plus SR's dont break Oil Pumps everytime they hit the limiter.

[SKiT_R31]

@ SKiT_R31 for the excellent N/A info - Bit off-topic are you a mechanical engineer (or something along those lines)?

Nah, I've just done a lot of research whilst procrastinating with my engine build. As well as spoken to a lot of old school engine builders/mechanical engineers, the sort that squeeze 150whp out of 1.2L Datsuns, 1000p out of N/A big block V8's, etc.

There is a lot of info on all sorts of things that you rarely hear about in the internet world (usually because its not relevant/necessary for FI). But the same can translate visa versa.

Edited May 25, 2010 by SKiT_R31

[mad082]

while a lot of this discussion is valid, i think a lot of what will make the decision of which engine to run will come down to how much money the OP has to spend. the reason being that there is a hell of a lot more aftermarket parts to build a high HP sr20 than there is a rb20. on a small budget the sr20 is going to be well ahead of the rb20. an unopened vvl motor with just bolt on goodies such as exhaust, ecu, can get you up to around 130kw at the wheels.

my main point is that if you tip in buckets of money into the rb20 it may end up making more power than a sr20, but if that isn't the case then going the sr20 with a vvl is going to give better yields for less money since your starting power is going to be 20 or 30% higher, as well as there being plenty of parts available as the ve motor is very popular in the states.

[Galois]

To those who keep suggesting other motors and classes, IPRA is split into 2 classes, Under 2L and Over 2L. If you run a turbo car you must run an intake restrictor and you must multiply your capacity by 1.7, moving almost every turbo car into the Over 2L category where you go up against Natro 5+L commodores and falcons, and of course the benchmark rotary Rx7s.

whoa so to go turbo you have to be less than 1.2L?! so there a like no turbo's in that class, unless someone's got some random 1.2 kia or something and put a turbo on it?

[HtwCHACtkh]

whoa so to go turbo you have to be less than 1.2L?! so there a like no turbo's in that class, unless someone's got some random 1.2 kia or something and put a turbo on it?

Nissan March Superturbo! 900cc Turbo+Supercharged.

Or turbo charge a K10 or 1L K11 Micra. These things can go surprisingly quick so it seems.

I wonder how light you could get an R32 after removing pretty much everything that makes the Skyline different from a Silvia.

EDIT: Also, out of curiosity if you had an SR20VE could you use the ITB's from the GTIR's SR20DET?

[mad082]

Nissan March Superturbo! 900cc Turbo+Supercharged.

Or turbo charge a K10 or 1L K11 Micra. These things can go surprisingly quick so it seems.

I wonder how light you could get an R32 after removing pretty much everything that makes the Skyline different from a Silvia.

EDIT: Also, out of curiosity if you had an SR20VE could you use the ITB's from the GTIR's SR20DET?

pretty sure you can. i have seen some threads where people have put the vvl head onto the gtir block to get the oil squirters. don't know how that would go for using it rwd though (don't know if the rwd turbo sr20's also have the oil squirters). then they use the sr16 n1 pistons to raise the compression (just getting them modified slightly), sr16 n1 cam.