raverx3m

iTrader: (1)

so then an itr crank would be beneficia at higher rpm at the expense of some low rpm torque correct?

and if i understood correctly
1 components are ballanced individually
crank
crank pulley
flywheel
rods and pistons are weighted separately?

but with ITR rods and pistons are ballanced for each specific crank.


and in case of CTR motor the only reason that its able to use N1 style pulley is because of its rod/stroke ratio same as b16?


eg1834
what you mean is that the crank weight does not relate to the mass of the pistons and rods as long as they are equal weight when assembled and same weight distribution on the rod end and piston end for all 4 pistons?
as in. the crank counterballance is for the crank itsself and not to counter the weight of the piston.rod assembly since they also ballance eachother out.

and i also keep seeing same reply about unpredictability of oil flying around crankcase.
with that uncertain condition why would you not ballance the components anyway so the oil does not add to the disaster making the engine even more unbalanced.
what if the weight distribution is already on the borderline and it just happends that at 10000 rpm one of the pistons accumulates more oil than other 3 throwing it even more off ballance and possibly adding more wear or failure. or maybe it would accumulate more carbon deposits in addition to oil that will throw off the weight even more.

EG1834

With a flat plane 4 cylinder crankshaft, two journals are 180 degrees of the other journals and so are the counterweights. The mass of the pistons, rods, etc pulling in one direction is canceled out by the other two rods, pistons, etc moving in the opposite direction so they don't really need to be considered when the crank is on the balancer. The machinist only needs to be concerned with the mass of the two journals and their respective counterweights matching the weight of the other two journals and their counterweights. This is a photo of the first crank I balanced like this, it's a Brian Crower stroker crank for a Nissan SR20:



As for oil, it's going to be different from one revolution to the next. Acceleration, lateral G's, oil squirters, etc will cause it to be completely unpredictable. On one revolution, it could hurt, on the next it could help. Getting the crank to a true zero balance is a fools errand.

Nikos

sorry but I am going to have to disagree with the statement "The mass of the pistons, rods, etc pulling in one direction is canceled out by the other two rods, pistons, etc moving in the opposite direction so they don't really need to be considered when the crank is on the balancer."


The problem with flat cranks with the counterweights is that they can only counter vibrations that occur at the frequency of crank rotation.
The piston acceleration occurs at twice the frequency of crank rotation so there is nothing that you can do with the crankshaft counterweights to solve that problem.
It doesn't matter how big you make the counterweights, the forces are at the wrong frequency.

A cross-plane crank hides the vibration by roughy canceling it out through the sequence of piston motion.
On small stroke engines like 4 cylinder compact cars and short stroke V8 engines with light reciprocating parts, the flat crank vibration is tolerable if you have very well designed engine mounting with proper damping.

On large stroke 4 cylinder engines with stroker cranks the vibration is horrible. There are drag racers that don't make it past the burnout box due to this.

For example in 2009, Yamaha introduced a new crankshaft for the YZF-R1
The new R1 took engine technology from the M1 MotoGP bike with its cross plane crankshaft. Crossplane technology puts each connecting rod 90° from the next, with an uneven firing interval of 270°- 180°- 90°- 180°.




So what I am trying to say here is that with a honda crank, you are limited when you take the crank beyond stock specs. Sure its ok for drag racing but anything else and with larger strokes, its a harmonics mess.

When you are looking at a crank on its own, its much different that was is going on with everything else attached to it at high RPM.

Honda engines are so over engineered with nascar class crankshafts when it comes to precision and balance that it is easy sometimes to take it all for granted.

If you really think about it, honda engines like the b18c1/c5, k20a/a2 ,h22 are high performance engines that come in street engine clothing.

DIY Blueprinting is basically an oxymoron.

Its more like DIY rebuilding. The first step before you go down that road is to realize that OEM engines are what they are for a reason.

That is why Japanese tuners are so conservative, its almost as bad as flat earth society people when it comes to Honda aftermarket. They are too close to OEM and for the most part will not go far from it.

raverx3m

iTrader: (1)

So pretty much using bobweights is same as ballancing the crank without them?
I mean when you want to check an unknown craigslist crank to make sure its not busted or bent.

Nikos

i don't know how you could possible check a crank on your own before you buy it on the spot.

There are good places around the country that could work on the crank but usually the issue here is that most people that buy a $100 crank, do not want to spend $500 to fix it.

$500 is a generic number but you get what I mean?

I received a set of cams (kelfords) that needed to be superfinished because of rust on the bearings etc.. they were in bad condition, I charged the guy $75 like flat short of fee but if I didn't own my own machines, it would be much more expensive to fix.

What I am saying here, is if you have a used crank, just run it. If you want to send it in, to be blueprinted to OEM specs, i would be careful who I would use, because most people do not want to pay a lot of money.

raverx3m

iTrader: (1)

i have a rotisory grill in the trunk with some stuffed bobcats precision weighted

no i means if i buy i take it to a local machine shop to at least make sure its not been used to hammer nails in a wall.and to check the bearing surfaces and if they are all round etc. the guy dont charge me that much ive known him for a while.

he worked at a honda dealership for a while so hes familiar with hondas in general and he had his machine shop for over 30 years not although he mostly does domestics ive seen a few mitsubishi and other honda engines in his shop. so he knows what to do with them and after picking his brain for a bit i have a feeling that he knows what hes doing

my mistake last time was not providing him with all the info needed and proper clearances and i didnt even know there should be taper in the cylinder bore but im guessing that he did since i have no problems with compression and he did put the rings in proper spots.

Nikos

sure, that sounds good.

What I am saying is that even if it was dropped or used to hammer nails, it might still work for what you want. just make sure the bearing surfaces are clean and straight ! lol

raverx3m

iTrader: (1)

im OCD lol

but i think im starting to take this thread off topic so ill stop asking questions

EG1834

I'm talking about the crank on the balancer, mass of the rods/pistons/etc as in the bobweight. It's a whole different ball game than the dynamics of the running engines and taking into account the effects of the reciprocating mass, jerk, etc. That's where "overbalance" is used.

Yeah, pretty much. Balancing the crank with or without the bobweights is practically the same, one just takes more time.

Usually if the crank doesn't have any unusual scoring or discoloration around the main and rod journals, it's probably ok. If it does, and if you see the bearings and they look bad as well, it would be a good idea to have it checked out. I'm lucky to have a very skilled crank grinder local to me, although sometimes absent minded. He usually charges me about $75 to turn and straighten a crank, which is much cheaper than having to rebuild later.

Rocket

Thanks, Nikos.

A common newbie mistake is to concentrate on areas that need to be improved. Spending time getting things balanced to 0.1 gram or knife edging a crank, exotic rod bolts. Spend time on a good cylinder prep, head prep, IM/ITB and cam selection. That will yield much more power and reliability.

Nikos

yes, it seems like the block is supposed to stay together, and the head is supposed to do as much work as possible with the direction of cams making best use of the manifold and header at hand.

Stroke and bore dictate the power range and RS ratio can tell you a little bit more but not everything because it seems like when it comes to drag racing, the important rule is to be able to finish the run.

A longer rod ratio (rod length to crank stroke) has a longer dwell at TDC and shorter at BDC

Fallacy: The longer dwell from a longer rod ratio increases torque

For example Nascar used to run 4.155 bore with a short stroke. At Daytona or Talledega where they had to use restrictor plates, engines could not develop as much HP. In those cases, For those situations they run smaller bore, longer stroke for all the torque possible.

Basically the higher the rod ratio, the later the point in the intake stroke when the piston reaches maximum velocity. (and maximum pressure differential) There is thus a larger volume above the piston to be filled, so a larger charge is induced into the cylinder, increasing volumetric efficiency and torque

Rosko

iTrader: (1)

I go back and forth on the bobweights vs no bob weights issue but I agree its practically the same deal. To me adding more weight would amplify any imbalance that is there and allow you to dial that in more closely, however it also adds in another opprotunity for error such as the bobweights not being made up correctly, or not being clocked right thus affecting the overall balanace. I would say in most cases you are going to have better luck with no weights added. As with anything it depends on who does the work.

Rosko

iTrader: (1)

I wouldnt spend much time chasing after a .1 of a gram but I wouldnt completely overlook balancing either. Its worth doing in my opinion.

EG1834

Exactly. I cut my teeth on a Hines balancer, the one in the photo I posted. It was all computer controlled and very nice and easy to use, but once you were down to less than 2g, the computer said you were done and wouldn't even show where the imbalance was. I'm sure there's a way around it, but that's the settings that it came with from the manufacturer.

Truth be told, when I was still really wet behind the ears, I balanced a crank with a bobweight 36g less than what it should have been. We had everything to weigh except bearings and my boss said "use 36g". Well, I thought he meant just plug in 36g. He meant each pair was 36g. I just plugged in 36g in my bobweight when I should have used twice that so the bobweight was light by 36g. I built the engine, it was installed in the car and fired up. No vibrations, no shaking, nothing. It later made about 1000whp and turned over 7500RPM, never any indication of any kind of imbalance. I didn't even realize it was light until the next one I built and had the bearings to weigh. Talk about shitting a brick!

raverx3m

iTrader: (1)

i picked up a book at barnes and noble about balancing and blueprinting

and theres alot more that needs to be done than just checkign clearanes and measuring ot of round

i mean he goes into measuring each rod and piston to make sure its straignt in ALL directions.

it seems like alot of this stuff cant be done at home because it requires very sensitive tools...

its probably possible to build a basic measuring station with dial gauges etc but after reading that book i see that its not a DIY job by any means.

the rods alone have to take about 8 -10 different measurements to have them exactly identical and not bent/twisted/offset/shorter etc

he also goes into stuff like using cryogenic freezing to strenghten the parts and reveal any defects. very good bock

raverx3m

iTrader: (1)

what kind of tools do I need to measure the actual rod length and centerlines?
is that even done during a typical blueprinting at machine shop?

im trying to buy all the basic tools I need to do the blueprinting at home and save some cash on a shop labor that way I would have more money to spend on parts

I still need the following:
digital bore gauge
depth micrometer
digital scale



question.
how do you pick the rod/piston combination to be same length and weight

because they have to be matching length to the crank and to the piston and piston has to be matching bore to the piston pin and the small end of the rod.
theres a lot of measurements which one you start off with ?