piston to head clearence

[deevergote]

Believe it or not, some people would! I don't think camdizawg is one of those, since his questions are always very well thought out... he's clearly thorough and careful. But I usually give my responses knowing that someone with a little less sense may one day dig this thread up.


Although, I HAVE read a statement from Bill Gude (Gude/Bullfrog) saying that he's had stock Honda engines rev safely to the limits of the bottom end before the stock valvetrain ever gave them trouble. There was no specification on what engine that was, though (if it was a B18C5, those springs are damn near race springs already!)

When it comes to engine parts, I can't stress enough that while these parts may be very strong and reliable... they are OLD! My H22 is 14 years old!

[jhondayaaj]

Believe it or not, some people would! I don't think camdizawg is one of those, since his questions are always very well thought out... he's clearly thorough and careful. But I usually give my responses knowing that someone with a little less sense may one day dig this thread up.


Although, I HAVE read a statement from Bill Gude (Gude/Bullfrog) saying that he's had stock Honda engines rev safely to the limits of the bottom end before the stock valvetrain ever gave them trouble. There was no specification on what engine that was, though (if it was a B18C5, those springs are damn near race springs already!)

When it comes to engine parts, I can't stress enough that while these parts may be very strong and reliable... they are OLD! My H22 is 14 years old!

well, a few years ago, one of my friends had an eg with the bullfrog head package. the bottom end with stock internals did give up before the head. sadly, he put a big ass hole in front of his block. not for lack of oil, just revving too high. I have seen nothing but good works from gude, at least with my experience. I have used his performance parts before when I still had my 91 civic 4 door with second gen b16 in it. now that 4 door was unique.

[camdizawg]

well, a few years ago, one of my friends had an eg with the bullfrog head package. the bottom end with stock internals did give up before the head. sadly, he put a big ass hole in front of his block. not for lack of oil, just revving too high. I have seen nothing but good works from gude, at least with my experience. I have used his performance parts before when I still had my 91 civic 4 door with second gen b16 in it. now that 4 door was unique.

damn ghost....thats a pretty big difference, over twice the clearance that was referenced on c-speedracing

thanx alot

lol...yup i got the gude f22a head it used stock springs , been milled really bad so imma grab the thicker headgasket from f22 parts. it has a bullfrog cam, my understanding is that the lobes on the camshaft are the same size just a longer duration so the clearance really is not affected by the cam . trying to get away from claying the motor.....


btw

my f22 has flat pistons and keeping it all stock, reason being i think the block can handle as long as i dont rev the shit out of it and i have a spare block. new to the high compression thing, so i am trying to figure out how much HP and all that

thanx guyz

[jhondayaaj]

lol...yup i got the gude f22a head it used stock springs , been milled really bad so imma grab the thicker headgasket from f22 parts. it has a bullfrog cam, my understanding is that the lobes on the camshaft are the same size just a longer duration so the clearance really is not affected by the cam . trying to get away from claying the motor.....


btw

my f22 has flat pistons and keeping it all stock, reason being i think the block can handle as long as i dont rev the shit out of it and i have a spare block. new to the high compression thing, so i am trying to figure out how much HP and all that

thanx guyz

that's a good set up. with just the head package, you'll gain a good amount of power. have fun.

[KeeleDesign]

Just to clarify... 11.5:1 pistons, while streetable, would require at least a decent tune and premium gas at all times. That's .4 higher than the H22 Type S compression.

i only use 91 octane every now and then maybe 93.. but i have no tune and she runs just fine, as you can watch my video and see....

but this is not to say for the least that it is wise... it's just cost effective thus far.
i'd like a tune but hey she's been good so far...

[Chrisisiced]

If you spend the money to build a head, I would suggest upgrading the bottom end as well... nothing is worse than dropping $1000+ into a head just to put a piston into it! The h22 stock bottom end is very strong, but these motors are old. Plus, headwork and an improved valvetrain would benefit from a higher redline, and revving beyond the stock redline with old stock parts holding the bottom end together could end up disastrous. It may not... but is it really a risk worth taking?

Well how high are we talking about revving here? Im not trying to make it to 9k! I would think that staying below 8500 I should be ok..... I already take my pretty much stock H up to 8k when going from first to second sometimes.

But i do see your point.... I think i may still take that risk.

[KeeleDesign]

Well how high are we talking about revving here? Im not trying to make it to 9k! I would think that staying below 8500 I should be ok..... I already take my pretty much stock H up to 8k when going from first to second sometimes.

But i do see your point.... I think i may still take that risk.

do you have a video?

[wed3k]

you guys know that you dont need to rev high to make power?

[KeeleDesign]

you guys know that you dont need to rev high to make power?

on a import such as an n/a h22 yes you do, unless modified with a stroker kit.. blah. I am sure deev, or mr phil or someone can explain much better than i.

[KeeleDesign]

i can't put it anybetter than how he puts it

owequitit
Moderator

on the 2.6 liter stroker thread

First, some more information.

Engines are air pumps. They simply burn gas in the process of pumping and extract energy from the burn to turn a shaft.

The only things that matter are how much air we pump, and that we maintain a proper air fuel ratio.

HP - horsepower is derived by calculating the amount of work done over time. In relation to an engine, it is the amount of work done per revolution.

You will hear a lot of people say that "there is no replacement for displacement" or "HP sales cars and torque wins races." These statements are just not true. These are usually muscle car guys referring to torque. The problem is that torque isn't actually responsible for moving a car. Why? Torque implies a radial force being applied to something. It does NOT imply work. If I place 100lbs of twisting force to a shaft, using a lever arm of 1 foot, I am generating 100 lb/ft of torque. If the shaft does nothing, then I am not doing any work, per the definition of work. If I increase that to 500lbs, and the shaft still does not move, then I am still not doing any work.

That is where HP comes into play. Horsepower is dependent on torque, but also on RPM, which makes it an actual measure of work, because the shaft is actually moving.

The formula for HP is:

HP=torque * rpm
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5252

The first thing that should become apparent about this formula is that we actually have 2 ways to increase the amount of work done.

We can:

A) increase the amount of torque at a given RPM, which is usually the route the muscle car guys take when they increase displacement.

or we can

B) leave the amount of torque generated alone and increase the RPMs. This is the route chosen most commonly by Honda. When coupled with the super high flow heads that Hondas are equipped with, we end up with the high revving, deep breathing Honda engines we have today. They still make a lot of HP, they just do it by turning faster instead of huffing more air per revolution.

Let's try it out and see what we get. Let's say we have a 2.0 liter four cylinder and a 4.0 Liter V8. We will assume that the heads flow exactly the same, and that the V8 makes exactly twice as much torque at any RPM. We will also assume that because it is twice as big, it redlines at 1/2 the redline of the 2.0. That will allow us to cleanly demonstrate the formula. We will calculate torque at a redline of 5,000 for the V8 and 10,000 for the 2.0.

HP(V8) = 250 lb/ft * 5,000rpm
--------------------
5252

When we work this out, we get a HP value of 238 HP. Notice that our torque is larger than our HP. That is the result of not being able to leverage torque against a lot of RPMs.

Now the 4 cylinder. It makes half the torque and spins twice as fast, so that is what we are going to plug into the equation.

HP(I4) = 125lb/ft * 10,000rpm
---------------------
5252

When we work this out, we get a HP value of 238 HP. Notice that the HP is much higher than the torque. Why? We are leveraging a small amount of torque over a lot of RPM and are thus make more power with less torque.

One of the arguments leveraged against Hondas is that they have no low end torque because the HP is so high. They assume that they must be weak. In fact this is not true. Most Hondas I have driven do just fine in the low end against other engines of comparable displacement. There APPEARS to be a disadvantage for several reasons.

1) The peak torque usually occurs high. That is what we expect to see since their breathing efficiency extends so high into the rev range. This makes them feel comparatively weak to their top end. However, if everything were compromised towards torque, we wouldn't gain much anyway due to the small displacement, and we would lose a TON of top end. Then they would "feel" like a lot of other "torquey" four cylinders.

2) People fixate on numbers. It is an easy way for them to relate things to one another. This analysis can be flawed though.

Look that the F22A4 vs the F22A6 for instance. The A6 shows 10 more HP in the spec sheet which is good, but it also shows the same 142 lb/ft occuring 500RPM higher, which on the surface is bad.

Most people would see this and assume that the F22A6 has less low end. That is wrong. It actually has more. Why? The dual runners allowed less compromise between low end torque and high rpm power. The low runners only have to function to 4800, not 6300, so they were optimized for lower RPMs. Then at 4800 the secondaries open and the runners can now breathe to redline. The larger cam helps marginally as well, and probably helps explain the increase in RPMs for the torque peak. That is why numbers can be deceiving.

The main upside to small displacement/high rev engines is the fuel economy associated with them. Most people assume that you can't have power AND economy, because this is what we are conditioned to believe. That is also NOT true to an extent.

With a large displacement engine such as a big-block Chevy, we are forced to fuel a large displacement at all RPM's in order to keep the engine running. This results in less fuel economy, especially at low power settings where you are pumping way more air than you actually need to accomplish what you are doing, say cruising at 30MPH.

With the small displacement high revving engine, our fuel need only goes up with RPMs. That means that if 2,000 RPM's will accomplish what we need to do, the four cylinder will burn less fuel at that given point, leading to the fuel savings we typically see with Honda. That is also why if you keep them on boil all the time, you will see a BIG decrease in mileage.

There is a lot more to it than that, head efficiency, cam profiles, intake restriction etc, all add to the equation, but for the purposes of a block and this conversation on bore and stroke, we will assume all top end aspects are the same.

The reason you have to compromise your variables is because each individual variable has certain advantages and disadvantages just like everything else in life.

You have to choose among the variables and potential solutions to get everything set up to work together.

For instance, bore.

A larger bore is one way to increase displacement. More bore = more air moved per revolution = more power per revolution. The advantage of increasing bore is that it allows you to increase displacement without increasing stroke, so we can move more air, and keep our piston speeds the same. That is one reason a larger bore and smaller stroke will like to rev more.

Not only are we covering less distance with each stroke, but this allows us in turn to increase the redline more before we get to dangerous piston speeds since each piston is moving less per revolution. This allows us to increase the redline more without having structural worries, but it does not explain how this works in conjunction with getting air into the cylinders efficiently.

What does explain how it breathes better, is the fact that the piston's velocity changes less between TDC or BDC and the pistons maximum velocity. This means slower acceleration at a given RPM, which is conducive to high revolution cylinder filling with a given valve area because the port velocity remains lower for a longer amount of revs.

This has a lot to do with what goes on at the port, which is yet another variable that has to work with everything else.

The disadvantage to increased bore is multi-fold. A larger bore requires a larger piston. A larger piston means more mass, which means LESS revability. As the piston get larger, it also gets harder to get the entire mixture burned, as the flame front only propogates away from the spark plug so fast. If it doesn't get to the outer portions of the cylinder with time to burn completely, you can get higher hydrocarbon emmissions which is bad for emmisions. This would probably only be the case with a really ridiculous bore size though.

As an example, this is the main reason rotory engines have bad emmissions performance. Their combustion chamber is very shallow, but also very elongated. The flame can't burn everything before the exhaust stroke, so there is a much higher concentration of hyrdocarbon (unburned fuel) emmissions.

A larger bore also requires more spacing between bore centers. This results in a larger block which results in a heavier engine. Imagine if we increased the bore by 1/2". That is a HUGE increase, but works well for rounded numbers. On a bank of four cylinders, this would theoretically make our minimum block length an additional 2". Even in aluminum, that mass is going to be heavy. Now we can do things like thinner liners, closer piston spacing etc, but again, that requires still more compromise, and you can only do that so much..

Increasing the stroke on the other hand, has many of the opposite effects.

The increased acceleration away from TDC causes our peak volumetric efficiency to occur at a lower RPM. Since the torque peak on an engine coincides with peak volumetric efficiency, our peak torque will occur at a lower RPM as well. This is good for around town driving, towing, etc.

Why?

The acceleration of the piston is greater, which brings the port velocity to its maximum at a lower RPM. Once the maximum port velocity is reached, power WILL taper off because it physically can't flow any faster. This leads to an earlier power peak, which again is good for the above reasons.

owequitit : I hope you don't mind me using this....

[wed3k]

meh, if you have been watching endyn's 150hp/lt build, it makes strong power to 8k and after that all torque drops.

its all in the camshaft, changing that will change your power range.

[quickangel93]

its not worth to mill the head really. if you mill the head and like 50k miles down the road and something goes wrong and your pretty broke and find out you need to get some headwork done and they tell you that you cant because they cant cut it anymore. what do you do?

the best way is to get high compression pistons, forged rods, main bearings, bigger cams, adjustable cam gears, .5mm oversized valves, titanium vavle springs, and a really, i mean really good tune.

because if your going to do it, do it right the first time, or dont do it at all. it better to have a car than to not have a car like the situation im in.

[KeeleDesign]

I'm wondering the same thing. I read that milling the head would raise the compression and in turn that would equal more power.... so I want to know how much a jdm h22a head should be milled to see a noticeable gain and keep in mind this is a daily driven car so I don't know how milling affects reliability..??

ok here is something that may help you in your decision on milling for power wise..

A mild n/a engine where you have no control over the mapping of the ecu can usually run a comp. ratio of 10:1 without any problems on 92 octane gas.
if you can program the ecu comp. ratios up to 11:5:1 are possible on 92 octane.
all out race only n/a motorsthat run on racing fuel like used in all motor 8 class drag racing or road racing run comp. ratios of13:1 up to 15:1.

high compression ratios increase an engines thermal efficiency greatly and slightly increase the volumetric efficiency.
FOR EVERY POINT OF COMPRESSION INCREASE, YOU GET APPROX; 3 TO 4 PERCENT MORE POWER.

this increases power across the board at all rpm ranges. The increase in thermal efficiency from raising the compression ratio also improves the brake specific fuel consumption or BSFC.
This is the measure of an engines thermal efficiency measured in pounds of fuel per horsepower per hour, if you care.
high compression pistons normally have a dome: the dome takes up cylinder volume at TDC to raise the compression ratio...
To raise the comp: ratio to what you desire, the dome volume must be stated to the piston maker so they can design the appropriate dome.
It is a good idea to keep the dome as flat as possible, as too high a dome can hamper flame travel and cause unstable combustion, which can cause detonation or loss of power.
the ideal pistonconfiguration is a flat top. This gives the best combustion , but the dome is often a necessary evil required to get the desired comp ratio.
so basically milling is a great idea than pistons in it's own way but not recomended unless you just cna't aford the time or money for pistons.
hope this helps with the insite of power and how to create it the besty you can

[KeeleDesign]

meh, if you have been watching endyn's 150hp/lt build, it makes strong power to 8k and after that all torque drops.

its all in the camshaft, changing that will change your power range.

meh,

[quickangel93]

meh, if you have been watching endyn's 150hp/lt build, it makes strong power to 8k and after that all torque drops.

its all in the camshaft, changing that will change your power range.

yea i learned that today, cams are very important. the less overlap the better