The B20VTEC discussion thread

[GSi_PSi]

Ummm yes they do come with 84mm b20 blocks???? no you dont have to spend money or time installing installing it..????
the reason why the itr crank shouldnt be implemented is because its not designed for the b20 bottom end, stuffing up the harmonics of the engine completly.
plus your losing capacity and torque which is needed, the 89mm crank will give you better torque lower in the rev range, without wearing out the sleeves higher in the rev range. Netherlesss its more a fck around installing the itr crank than leaving the stock crank which will give you a better output

[ewendc2r]

Ok so maybe someone like Adrian or Chris or someone else with extensive knowledge can step in here but my belief was:

Harmonics come from the crank, not the block.

Yes the B20 block comes with 84mm but it doesn't come with the 87.2mm crank does it!

Yes, if you want to do it properly, you should get the main's align honed ?? (is that the term?) where they ensure the journals are true and straight. Then new bearings.. ADDED COST / EFFORT

The difference in capacity is a huge 40cc ...

I don't drive my engine on the track at lower rpm where the said 89mm develops more torque, and even on the street if i want the power i change down a gear. Why? To take advantage of a freely spinning engine.. In fact, the rod/stroke ratio and rod/bore ration is inclined to producing peak torque higher in the range meaning (again because HP is a product of torque & RPM) the range i use the motor in, it actually develops power higher where I am using it rather than tapering off..

ITR (again) is fully counterbalanced ... It can be lightened (some say around a kg max) without affecting high rpm harmonics / vibrations. Remember heavier = better vibration damping to some extent however at cost of engine response. Thus my question about weight of 89mm vs 87.2mm..

Look, if I could get a tall deck block, I'd just get a 92mm crank and call it a day with 84mm bore but thats when costs start to ramp up...

I'm not trying to start an argument but it just seems in race motors that the 87.2mm crank has yielded more reliable high rpm performance and with similar power levels (area under the graph, total accelerative effort)

[ewendc2r]

(ps im not trying to disrespect anyone here -- I have not built one, just trying to learn as well)

[Chr1s]

The thread has turned into something for once .

Harmonics can come from anywhere, it mainly gets distributed and amplified in the crank though. This is not apparently in only B20's, it's a phenomena in alot of engines, the F1 engineers spend hours on R&D to minimise/eliminate this in their motors, if anyone can get their hands on a spectograph from the engine recording of an F1 engine you will notice red areas in the lower RPM range, this is the harmonic they avoid, since the engine is barely at that RPM, it's not a worry, but i'm just trying to prove a point, every motor has a strong harmonic, my old nissan KA24 would harmonic so bad at around 7500 with the standard components its known that blocks have split, and we're talking cast iron blocks...

My only advice to eliminate this crap, balance everything in the engine, rods, pistons, pins, etc etc all the same weight, run a good harmonic balancer, ensure you have an oil cooler of some sort (99% of b20's out there don't have one), don't run aggressive cams for no reason and do the checks to ensure everything is ok - crank is true, etc. Align honing of the bores is something that should be done regardless. I don't know how many machine shops go through this process to check but to be honest, Honda blocks are pretty damn good from factory. I've had one block that had a stupidly tight 5th main on it though...don't know what happened there!

Crank weight - lighter is not always better, think of induced wobble. By using the ITR crank over the B20 crank, I daresay the engine response won't change much especially once the motor gets breathing.

This leads me to b20 crank vs itr crank, I don't see the big fuss, it's probably a good idea for the street and to keep the compression manageable, the rod ratio goes from 1.54 to 1.57, which is nothing dramatic. Sidewall/bearing loading is fine with that rod ratio regardless, you probably will find longer life from the later, but this has not been a problem on any street b20 so far.

The problem with making power isn't so much from the bottom end, too many people spend time on the bottom end and forget that power comes from the head. Yes the geometry of the bottom matters and choosing the right components bla bla matters, but who here goes to the effort of finding out what works best, what lasts the longest, what will make better torque and maintain life, at the end of the day, what I just mentioned in pursuit is left to engines with iron sleeves. I can't see standard sleeved b20 motors lasting with a fair big of power going through them for long, even if some do, I still think it's a matter of luck with regards to how long the sleeves will hold together, there is too many variables in the block production process and for material to cool in x amount of time will result in some sort of imperfection and result with a crack size different to the block made a moment ago. If someone thinks i'm talking out of my arse I can show you a simple mathematical model of how internal crack size changes the fracture toughness of a material.

If I was to do a sleeved b20 build, i'd do a tall teck with an 85mm bore and a 98mm stroke. Custom pistons with the pin raised as far as possible and running a rod as long as possible. I put together something that I calculated one night from curiosity, it's doable but the pistons will need a fair bit of insight to design, everything else is pretty much available easily.

This is comparing a typical ~135kw b20vtec build to what my program spat out for the figures of my combo; (assuming a 300cfm flowing head)



For those who can't read the graph, the bottom lines is the torque and HP output of the ~130kw b20v. (red and light blue is the big b20, light green and dark blue is the ~130kw b)

edit: Yes, restrictive exhausts lead to detonation on any engine, not just b20's, the increase in backpressure means that some exahaust gas may find it's way back into the chamber again and the rest is downhill..

[mocchi]

Ok so maybe someone like Adrian or Chris or someone else with extensive knowledge can step in here but my belief was:

Harmonics come from the crank, not the block.

Yes the B20 block comes with 84mm but it doesn't come with the 87.2mm crank does it!

Yes, if you want to do it properly, you should get the main's align honed ?? (is that the term?) where they ensure the journals are true and straight. Then new bearings.. ADDED COST / EFFORT

The difference in capacity is a huge 40cc ...

I don't drive my engine on the track at lower rpm where the said 89mm develops more torque, and even on the street if i want the power i change down a gear. Why? To take advantage of a freely spinning engine.. In fact, the rod/stroke ratio and rod/bore ration is inclined to producing peak torque higher in the range meaning (again because HP is a product of torque & RPM) the range i use the motor in, it actually develops power higher where I am using it rather than tapering off..

ITR (again) is fully counterbalanced ... It can be lightened (some say around a kg max) without affecting high rpm harmonics / vibrations. Remember heavier = better vibration damping to some extent however at cost of engine response. Thus my question about weight of 89mm vs 87.2mm..

Look, if I could get a tall deck block, I'd just get a 92mm crank and call it a day with 84mm bore but thats when costs start to ramp up...

I'm not trying to start an argument but it just seems in race motors that the 87.2mm crank has yielded more reliable high rpm performance and with similar power levels (area under the graph, total accelerative effort)

for added peace of mind if youre so worried about harmonics? ati fluid dampers
http://www.atiracing.com/products/da...s/damhonda.htm

[ewendc2r]

Will get one anyway .. All insurance and tlc hah.

Thanks for the detailed reply chris

[Benson]

An ITR crank pulley is more than sufficient to rev to 9200rpm. Just make sure you balance the bottom end properly

[ewendc2r]

Benson, you mean using an itr crank and pulley is good to 9200rpm no need for damper? Or using itr pulley on b20 crank??

[Touge Tom]

i went the thicker gasket so i could use 98 octane without detonation, other wise i'd have to use aviation fuel, and that shit's expensive!

[Touge Tom]

wasn't all that expensive. just gotta know the right people?. the header isn't restrictive, you should check out the buddyclub site for info on these pipe's. the ports are factory size's. don't know the out put yet, i don't think it's worth knowing till i get my hand's on a S200 for a proper tune. but with the vafc2 i find i get a smother vtec switch point @ 5900, rather then the factory 4900 point, i also adjust the fuel map between these point's up 20%, think about it max rev's 8200 so the gap between these points is 20% of the rev range. i not claiming it's 100% accurate but by feel and checking my spark plug's it's not running lean or rich.

[ewendc2r]

Ahh I see the logic in that (i.e. easier to build high cp short block and lower compression with head gasket and still have high cp capability for track in future etc .. ) Only concern is I heard thicker head gasket can fail easier??? (Confirm or deny anyone?) ..

I got to thinking about it all last night a bit more in depth regarding 87.2mm vs 89mm for my and most applications.. I'm not planning an 11,000rpm build so using the 87.2mm crank is probably unnecessary as Gsi-Psi pointed out in another thread.. I also figure that I can get a forged bottom end sleeved b20 (or b18 bored) to rev happily to 9500rpm when needed..

I think I've secured a head

Chris -- the 98mm stroke would have massive load on bearings wouldn't it? I.e. that would be great for a single race but no more without a tear down and inspect? Seems even with the 95mm stroke the increased load on bearings is an issue.. Thus the 92mm application for a daily duties high peformance motor... Would love to see that build though!

Has anyone had their block sleeved in Australia or should I get a block from the US? Shipping will be $$ compared to block price itself.

[GSi_PSi]

you have balls running that car on only a shitty vtec air flow controller