B20-CRV VTEC - Why it Blows.....

Johnny_9

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Johnny_9

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"In automobile development, the weight reduction is and always has been a significant and challenging issue. When the weight of the engine itself is to be reduced, the proportion of the weight reduction accounted for by the cylinder block is very large and thus very necessary," asserts Honda. The company has been vigorously developing and producing engines, many of whose major components are aluminum, particularly cylinder blocks. It adds, "Cast iron sleeves are being used as cylinder liners in more aluminum engines; this is an obstacle to further weight reduction." Some of the solutions Honda suggests are use of 1) a hyper-eutectic aluminum-silicon alloy (A390), 2) an aluminum liner on which Ni-SiC powdered dispersed plating is applied, and 3) a metal matrix composite, any of which enables the production of a linerless light-alloy cylinder block. At present, its cost is prohibitively high and its manufacturing process too complex for volume-production vehicle models.

So the more-commonly used technology is separate iron liners cast in the aluminum block, which in Honda engines requires at least a 9 mm minimum distance (web) between cylinders. These factors determine an engine's outer size in proportion to its cubic displacement, and there lies, literally, a rub.

In more practical considerations, Honda was readying its first compact sports utility vehicle, the CR-V, which would be produced, including its aluminum engine, at the company's Suzuka factory, the home of Civic cars. In fact, the CR-V, though a considerably larger vehicle, belongs to the broad Civic strategy that the company was pursuing, and that would produce more variants and derivatives.

The CR-V, with good off-road capability, would need an engine with about a 2.0-L displacement. Honda's type F20A engine of the Accord family, with its width of 694 mm, would not fit in the shell, and comes from another factory source. The engine must be of the compact type-B family, for the sporty Civic and Integra cars. The type B16A 1.6-L unit, and the B18B 1.8-L version, shared the same block with with the engine's overall width of 601 mm. The B18B's 1834-cc capacity was obtained by stroking the B16A to 89 mm. Further enlargement to a planned 2.0-L capacity could only be achieved by increasing the bore of the B18B, however, the engine's high-pressure die cast aluminum block with separate iron liners left no room for such enlargement. Thus the development of a new one-piece cast liner unit with four integrally cast cylinder liners came about, which Honda describes as "consecutive liner construction," or "quad-sequential sleeve block." It is more like Siamese-quadruplets. With this liner construction, the web distance, or distance between the inner walls of the adjoining cylinders, could be reduced to 6 mm from the separate lines' 9 mm, while retaining the same bore pitch. This was the essential requirement so that the new block could be cast and machined on the existing Suzuka lines. This enabled the addition of 3 mm to the bore, to 84 mm which, combined with the B18B's 89 mm stroke, increases the engine's cubic capacity to 1972 cc. Further, the increase in block mass is only 0.8 kg, from the B18B's 25.3 kg to 26.1 kg. Efforts were made to shave mass from other internal and external components of the B20B, achieving the end result of a total dry mass of 144.5 kg for the new engine, to the smaller displacement B18B's 148.1 kg, making it one of the lightest in its displacement category.

There were a number of technical problems that accompanied the new block construction that had to be solved. The main problems and solutions were as follows:

Deterioration in cylinder cooling because of the mono-liner construction--The liner connecting point between two cylinders is the most critical area that may be affected by different temperatures between the two materials, the aluminum block and the cast iron liner (there is no coolant passage in this area). A number of connecting point configurations were investigated at WOT at 6000 rpm. An optimized connecting point configuration with the least temperature rise in the area and in the aluminum portion was selected to ensure adequate cooling capability.
Casting gap that may develop between the iron liner and the aluminum block body during aluminum's solidification process--With the mono-liner, the direction of molten aluminum's solidification is different from that of casting-in separate liners. Residual stress exerts inwardly and fairly evenly in the case of separate liners, whereas with the mono-liner unit, its direction is outward along the aluminum casting's outer periphery, thus causing a separation or gap. Honda's solution was the casting of "spines," tiny cylindrical protrusions on the outer surfaces of the critical areas of the liners that ensure secure bonding of the two materials. Honda reports that gap occurrence has been reduced to one percent of what it would be without the spines.
Damaging of the casting and spine by residual stress--The spines receive solidification and contracting forces, thus the area around the liner wall connecting point is subjected to extremely high residual stress, which may damage the spines or crack the aluminum casing. A clamp placed atop each cylinder liner, that provides a path to molten aluminum, disperses concentration of stress, making it similar to that of a separate liner.
Liner distortion due to casting stress--In the mono-liner block casting, contracting force is greater in the X axis (the block's lengthwise direction), that may deform the cylinder bore shape. The mono-liner unit has calculated, slightly oblong circular shapes that re-form to true circular shapes during cooling. Further, the liner unit's bottom portion is subjected to higher solidification stress, bcause of larger aluminum mass in the area. The liner is, therefore, initially shaped as a frustum, which re-forms into a right circular cylinder in casting.
A senior Honda engineer says that mono-liner casting techniques had been presented in papers, the oldest by Ford to his knowledge, and some six years ago by Daihatsu; however, one has reached actual product application. Honda has applied for 13 patents comprising 44 items, according to the engineer.
 

D-IV

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D-IV

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Very good info... Read this a while back. Keep the tune conservative and cooling in top notch, it should'nt crack at all. Ofcourse its the weakest amongst the b-series due to the one piece sleeve design.
 

shiroitenshi

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shiroitenshi

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Woah, zth is alive again, those freq maintainance and server downs were really turning me off.

back to topic

someone once told me he ran 32degs on his b20b at WOT (peak load?)

while in real life, I'm fighting knock at timings way below that. Sure I can set it at 32, and hope that the P30/honda knock sensor retards the timing, but one day the knock sensor fails, kablooie engine. There's also the problem of trying to differentiate between knock and piston slap, but that one is solved in a rather mundane way.


Well, still waiting for the vacuum log, before the ITB install. Won't be much different i'd guess, big throttle bodies, but breathing out a 2.25 inch exhaust.

As to why b20B blows, it's sometimes the tune as well. A lot of people run piggybacks on B20B setups. One problem with this is that honda P30 ecu retards the ignition upon hearing knock. And that confuses the tuner who tunes the ride. What we see on the mapping aren't the real life timings and duty cycle. (honestly speaking though, it's hard to f**k up a tune unless you tune blind, and believe B20B can put out 250whp WITHOUT some serious mods) And I edited that word for accuracy.. SOMETIMES ITs the tune, prolly 90% of the time, it's parts failure due to overevving..

"Oi, my b20b can make 9500rpm!, I did it a few times yesterday.. I'm going to show you today I can do it too.... Vrooommm--BOOOM!"

Lesson: If it works a few times, it MAY not work all the time.

Anyway..
For a B20b, I think most should never ever opt for piggybacks, but invest in standalones.

A second possible reason is injectors. You can bump up fuel regulator and use H22A injectors with the resistor packs, but it's not a long term solution. If the resistor box fails, the injectors will deliver fuel differently, and that's where one of the problems begin. or start to put out fuel intermittently (lean sauce, anyone?)

Another is loose piston to bore clearances. Most B20bs are loose, and they get loose a lot faster than B16s due to the rod stroke ratio and the rod angle. Piston slap, faster wear, and soon enough, low compression and bye bye engine.

Then again, if you daily drive a B20b, it probably won't cost much to maintain. since you probably won't be revving it up to 8K every day.

Love the low end torque, makes driving a breeze, and sometimes you wonder if you really needed VTEC :P
 
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D-IV

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D-IV

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I run that amount of timing with no problem. But that was on Stock block b20b with p3f pistons (valve pocket modified for clearance). Btw, i can run those high timings due to the low compression and it lasted me the beating everyday until i sold it off. But had to retard timing after 6500rpm to 28 degrees flat though.

Not sure what octane rating you guys are running over there. We're using 97 as pump here. But even the Australian tuner smelt that our fuel seems to be acting like a 100 octane. He must've have some sensitive nose to quantify it :biggrin:
 

dcloo

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dcloo

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:adore: its really good explain of b-series family built.....
 

pencalat

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pencalat

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thanx 4 the info..
blown my engine last month..
now left at danau kota woksop...
but, why can't use the piggyback??
 

shiroitenshi

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shiroitenshi

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thanx 4 the info..
blown my engine last month..
now left at danau kota woksop...
but, why can't use the piggyback??
Piggyback applies what we call a lambda on the original fuel mapping.

remember the tables your tuner looks at?
XXXX| 1 | 2 | 3 | 4 | (more, but omitted)
1000 | 2.00 | 2.10 |2.50 | 3.00 |
2000 | 3.00 | 3.20 | 3.6 | 4.00
(more, but omitted)
as an example,
The RPM is the 1000,2000 value, called the RPM index,

The 1, 2, 3, 4, is the load zones (or load index), some, like the PowerFC, uses numbers, while hondata, uses actual units (it doesn't matter really) Most piggybacks just use TPS to simulate the load index, like VAFC, Neo, etc. which means a little like guessing where the computer is ACTUALLY reading the map from.

Yes, unlike what most people think, tuning is not really 100% exact science. Remember vacuum advance? Lol, that's not controllable at all, but the old fellas did it by use of springs and such, heck, they don't even care what kind of ignition it's running, as long as it made power.
You can also replace the load zones with TPS indexing on standalones, but usually that's done for running quads, because they can't have good part throttle (on/off driving) at low rpms due to lack of good MAP signal (it's doable, but well, what's the benefit of running quads with a tuning method designed for manifolds?)

That's why that's there manifold versus ITB, which is better? debate down in honda-tech, I think.

Back to topic. Well, what the piggyback does is apply 'adjustments to the map'

xxxxx| 1 | 2 | 3 | 4 | (more, but omitted)
1000 | 1% | 1% | 1.5% | 3% |
2000 | 1% | 1% | 1.5% | 3% |
(more, but omitted)
Like emanage, and unichip, they work in this method. They add adjustments to the original mapping, which is all good and fine, if the original mapping is static.

The thing is, the mapping of honda ecu's in open loop mode is not static, (for the most part, at near to full throttle it's static) it changes from time to time, courtesy of it's long term and short term fuel trim. I think powerFC does this feature the best as an example, just start and wait for it to find it's own idle during intial setup. That is a more extreme example of how it works, but even the stock honda ecu's have that feature, although not at such a high correction rate.

But it's not like piggybacks are bad, they are good for minor adjustments, esp when the original ecu mapping is suited to the engine, but just need a little tweaking.

In the B20B case, most of the ECU's used, the original mapping is for the B16A, imagine what kind of adjustments are needed for that, and what kind of fuelling changes the original honda ecu will do as time goes by.

having a static lambda (fuelling adjustment) while the stock keeps adjusting itself, it's like trying to swat a moving fly while driving a car in the rain. lol. those raindrops and the fly start to blend in.. and both are moving, so you can't really see where the actual fly is.

I'm not sure if the newer gen piggybacks start tricking the 02 into a closed loop mode yet, but if you're the curious type, if D14 on the P30/P08 ecu is connected to the piggyback, then it probably is. I think that's probably one way to get around it, but well, originally piggybacks were made to map more accurately the original mapping (cleaning up the mapping due to added mods that changed the flow of the engine, when the original cannot cope anymore)

I don't think it'll ever come to that since it's like the piggyback trying to become what it's not, but well, just thinking out loud.

Well, that's just a small aspect of tuning. Now I know why mat salleh find it so fun. :P
 
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D-IV

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D-IV

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long time then baru kena reply... haha...

Over revving too generalized lah. Or maybe just didn't bother to open up and find out what was the weak point. But nevermind.... not that i'm bothered. If built properly and tuned, it should be able to last. Human error is most of the time that blows motors...
 

pencalat

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pencalat

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haha... bz ar bro...
summore tgh kumpul wang mau kasi cun cun punya...
the prob now, rpm n speedo mcm biol la...
maybe distributor....
 
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