The B20VTEC discussion thread

[Touge Tom]

okie dokie?

[ewendc2r]

Togue Tom .. How many kms u got on that setup? Longest I've seen so far is 25000miles so about 40000kms on a b20 stock sleeve before dramas... I guess they haven't been around that long to get an idea of longevity..

[tinkerbell]

i just don't get how we assume that my build would fail and have to be tow'd home due to a VAFC2.

VAFC works fine for a B20VTEC... it all comes down to the tuner i guess?

[tinkerbell]

Togue Tom .. How many kms u got on that setup? Longest I've seen so far is 25000miles so about 40000kms on a b20 stock sleeve before dramas... I guess they haven't been around that long to get an idea of longevity..

mine did over 40'000km and is still going...

my other one is also still around, from 2002 - no idea how many km on that one!

[ewendc2r]

Do you give it a hard time reguarly or do you putt around town and only give it on the track???

[Mugen_R]

man if ur worried about the motor dying then don't build one

[ewendc2r]

Hardly a logical path.. I am mitigating weak points or concerns so I need to know those problems first. To say that is a little ridiculous. Everyone that builds an engine tries to avoid failure!

If you're saying don't build it unless you can afford it to fail then sure, but that's why I'm not going too hardcore with cams / rev requirement. Just making it as reliable as possible given others experiences!

[Touge Tom]

Togue Tom .. How many kms u got on that setup? Longest I've seen so far is 25000miles so about 40000kms on a b20 stock sleeve before dramas... I guess they haven't been around that long to get an idea of longevity..

about 65,000klm. serviced every 5,000klm by myself.

[Touge Tom]

VAFC works fine for a B20VTEC... it all comes down to the tuner i guess?

thank's for the support man!

[TODA AU]

I'm about to buy an Endyn head thats been prepared -- 1mm oversized intake valves, extensive porting and welding etc .. Hoping to use it as my 'power-getter'

Stay away from oversized valves they will not deliver unless your combination is perfect.

irrellevant, using a 89mm will give you more capacity

Is the extra 40cc more capacity is worth the inferior bearings & inferior rod ratio.
Not to mention the better crank that doesn’t seem to have the same harmonic issues.

The thread has turned into something for once .

Harmonics can come from anywhere,

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..

The longer the stroke, the greater the problem with harmonics
The higher the power output, the greater the problem with harmonics
The higher the rpm the greater the problem with harmonics
Balancing helps… & lightweight parts can help in an effort to push the resonant frequency beyond the rev range.
So for high output B-series applications, reducing one pasts propensity to exasperating the harmonic problem of the engine seems obvious, particularly with the change is a positive on three fronts & a negative on only 1.
Better bearings, rod ratio, harmonics V 40cc
Increasing the stroke on a high rpm engine is a less than considered approach.

Re exhaust flow…
Actually a more efficient exhaust means you need less total advance to produce best power. The reverse is true when an exhaust system is restrictive. The same is true of the intake.
Volumetric efficiency is reduced by a drop in efficiency & because of this less charge enters the cylinder.
If compression remains the same, more total advance is required because the dynamic compression is reduced.
The exhaust leaves of it’s own accord & some may be left behind.
But it never left & then came back. LOL
Anyway…

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

Fluidampr is another excellent brand

Ewen, the 98mm stroke build in the previous page had a long rod that made the rod ratio something like 1.52 which will show acceptable wear. I would go 84x95mm tall deck. 92mm will buzz harder but we all know rpm is teh devil.

With a 98mm stroke the pistons are still going to flog out because it’s got a 98mm stroke.
Rod ratio is irrelevant, this just tells you where the power is going to arrive best & how you aught to tune the thing.
& even with 95mm stoke in a dart tall deck, you still have to graunch big cut-out into the bottom of the bore to clear the rods & say goodbye to the piston under crown cooling jets.

Are there any sleeving specialists in aust that u builders would trust ?

We have a number of engines out there that are sleeved locally with no reliability issues.

[Chr1s]

Nice input Adrian, it's nice to see someone not agreeing all the time, it's the beauty of human life is it not? different views and all.

The 340hp calculated engine I did has nothing to compare with 40cc, let alone it's not even a 2.0L anymore, it's a 2300cc combination. The harmonics caused I beleive are negligable and that motor combination is very doable, if your logic sticks to plan, the mighty K series will turn its arse to bits if spun hard with their 99mm stroke or whatever it is, my donk I learnt on had a stroke in the 1000s and people spin them to 9500rpm while putting down 350hp at the tyre happily in new zealand sprint cars, but lets keep this b series related, i'm just putting it out there. The harmonic at the end of the day, is unavoidable, but can be minimised.

If you want to take the route of running less stroke and doing the rest to reduce the negative effect of the harmonic, well I don't see high output being possible with a reducing displacement.

Exhaust gas never coming back in the chamber? Umm, overlap? I think we're talking about different things and yes I agree with you 100% about the efficiency effects and pretty much in a nutshell, greater backpressure = harder for exhaust gas to evacuate.

The 98mm stroke build is possible, I wouldn't bother running oil squirters anyway, the pistons can handle the heat just fine, i'd rather maintain my oil stability and reduce slight pumping losses. Rod ratio will tell you where power is? So what if I had an engine with a rod ratio of 1.9 and a restrictive camshaft? When I see higher rod ratio numbers, I associate it with a motor than can carry the torque as the RPMs increase as there is less sidewall loading as a result the vector loading on the bearings is minimised, what do you think of when looking at a rod ratio number? (in detail please!)

Block notching, I don't mind this, there is actually less friction at that point but obviously more loading since the surface area is minimised. It's all one big tradeoff as you said earlier, minimise one thing, increase the other.

Keep this going, it's good

[ewendc2r]

Now we're talking! Thanks Adrian..

Hmm .. I'll consider the itr crank again now...

Adrian - also been advised to sleeve a b18c so I can retain the stock girdle and have a vtec block without risk of leaks... Apparently there are also dramas associated with sleeving a b20 due to different construction and wall thickness.. I like the Dan benson approach of removing the top half of the cylinders then installl a stepped sleeve which locates itself onto the original bored out cylinder half way down... Proper heat based install too rather than pressed.. Avoids issue of dropping sleeves. Only otherway is to slightly taper the bore?

With regards to exhaust since we want to maintain high velocity to create torque, I'd imagine the restriction in my 4:1 header bs big tube would promote mid range torque with limit on top end power ... Ie reach maximum velocity at a lower rpm due to increased displacement and aggressive head pattern?

Reason I wasn't concerned about oversized intake valve was that the examples I've seen show the engine needs about 80% exhaust flow compared with intake (due to atmospheric pressure dragging intake charge In compared with force acted upon exhaust gas exiting and heat of charge.. It seemed some of the heads responded well to the additional intake flow capability while maintaining exhaust around the same to increase effectiveness of the cycle? This is a ported head and alaniz was going to supply .5mm oversize on his intake valves too???