Stroker pin and Thicker gasket to increase CC
- Thread starter traxxas-modifier
- Start date
superturbocompound
New Member
`stroker pins or big bore pistons???,here are some maths for you guys to tinker around when trying to find out the parameters of an engine,
mean piston speed:-this is done to see if the engine configuration is suitable for a given rpm.not all engine are design to rev to 10000-12000rpm
formula is strokex2xrpm/25.4x12 (bench mark with stock internals in about 4500"/min
example:-
stroke 58.7mmx2 (piston moves up and down/revolution)
=117.4mmx10000rpm
=1174000mm/25.4(convert to inches)
=46221'/12(conver to feet)
=3852'/min(feet per minute)
stroker pin (3mm)
58.7mm+3mm(stroker pin)
=61.7mmx2
=123.4mmx10000rpm
=1234000/25.4
=48583'/12
=4049'/min
that is an increased speed of around 200'/min,so this stroker can rev not too much past 10000rpm.try zxr250(stroke of 34mm@19000rpm)
mean piston speed:-this is done to see if the engine configuration is suitable for a given rpm.not all engine are design to rev to 10000-12000rpm
formula is strokex2xrpm/25.4x12 (bench mark with stock internals in about 4500"/min
example:-
stroke 58.7mmx2 (piston moves up and down/revolution)
=117.4mmx10000rpm
=1174000mm/25.4(convert to inches)
=46221'/12(conver to feet)
=3852'/min(feet per minute)
stroker pin (3mm)
58.7mm+3mm(stroker pin)
=61.7mmx2
=123.4mmx10000rpm
=1234000/25.4
=48583'/12
=4049'/min
that is an increased speed of around 200'/min,so this stroker can rev not too much past 10000rpm.try zxr250(stroke of 34mm@19000rpm)
Hi, I don't do the feet/min way. But there might be something wrong with your maths.superturbocompound said:
• The stock stroke LC/Sniper/T135 has a MPV of 25.5m/s at 12,900rpm.
• If the crank is stroked with a 3mm pin, it'll have a MPV of 25.5m/s at 11,750rpm
These figures are considered the safe peak rpms for circuit racing. And btw, the MPV is NOT in indication of how far an engine can rev till. Its an indication of how far can an engine SAFELY rev till. I can bet you a million bucks that I can rev an engine over the supposely safe MPV. Maths/ Calculations are merely tools. Its how you use them. Cheers
yeah.. sure.. on 57 mm i can rev it more than 11.500, back again to ur needs, and what is ur target peak power.. hey stroker, can u get me a good valve guide and valve sitting material ? something better than AMPCO 45 or the like, but not too expensive and poisonous like beryllium.. ?
On a mildly tuned racebike I worked on (64mm piston), I'm revving it in surplus of 12Krpm. Peak power at 11,000rpm. Fierce? hehe Could've gone higher. Rider can't ride it properly in the track cos the power only kicked in at 8,500rpm (and goes rocket till 12krpm).haen said:
I really don't suggest using bronze or BeCu seats/ guides for non-titanium valves usages. The only reason I'm using BeCu is because of my titanium valves.
I'll suggest the plain iron seats. It works well with most valve material. Its cheap, readily avail and easily machinable. If you can find, ductile iron is a good material too.
I've also used cromoly seats with or without stelite with good results.
Cheers
superturbocompound
New Member
i got the formula out of one of my books,i use it just to see any engine if is design for speed or just a workhorse engine,(the book from usa,that's why its in feet,)and i see which way your maths is and its just looking at the problem from a different angle(both constant are different,mine rpm,yours mean piston velocity ,MPV).
i like this tech chat because it clears up some ambiguity,and the young guys who want to be "would be tuner" will already be equipped with an arsenal of mathamatical formulas to tune their bikes.one software i am thinking of getting is '4sthead',really good for r&d.
talking about stroking the engine,do you change the rods to a longer one since increasing the stroke would effect the rod ratio?
i like this tech chat because it clears up some ambiguity,and the young guys who want to be "would be tuner" will already be equipped with an arsenal of mathamatical formulas to tune their bikes.one software i am thinking of getting is '4sthead',really good for r&d.
talking about stroking the engine,do you change the rods to a longer one since increasing the stroke would effect the rod ratio?
docgabby
Super Veteran
wow what great brainstorming on engine tech. i used to read alot of engineering stuff myself even as a general surgeon. since most of our underbone parts come from hispeed race shop, mr kwang's shop does all the testing and just send us the parts. he says that all kits that he sents us has and have been tested by his or their race teams. the latest bigbore kit for the sniper was the set up they used in sepang cirucit malaysia which he proudly says team thailanfd has won. so i just trust it has been thought of well. of course we give him feedbacks because i guess filipino taste might be different??
docgabby
Super Veteran
filipino taste (maybe not all) want a "do it all" underbone bike...daily driver, dragbike, cirucuit bike in one!! when we tell mr .kwang about this kind of set up, he just sometimes scratches his head (according to the dad of our supplier who goes to thailand every month). you cant have it all in one bike! set up is really a matter of personal taste too and what application. this latest set up he sent us had power, had speed, but can also be used for touring (as exemplified in the sepang race), but reliability definitely is not on the best of sides. so its your choice according to him. bigger engine they can make, he says but dont expect engine to last very long.
4sthead is good if you know how to make full use of it. Very powerful. Again, they're merely tools. At the end of the day, its the timing on the LED that appears at the end of 1/4mile that counts (or for that matter, circuit results slip).superturbocompound said:
I'm sure you guys wouldn't believe me if I say that at least 90% of my 'A' race bike is modified. At least 60% of it is custom designed and precision manufactured—that you won't be able to find similar items anywhere else in the world. Where every imaginable aspect was designed ground up specifically for its usage. Winning the bloke next to it, that is. :twisted: :twisted:
superturbocompound
New Member
hahaha i can understand,stroker said:Its a lengthy topic. Too boring for most readers I'm sure. I've briefly talked about this I think. Ha.haen said:nice topic : rod ratio.. hey stroker.. care to add more info to it ? it'd sweet
basically rod ratio is about the relationship between the length of the rod and the stroke,why is this important?the rod ratio can influence the:-
1)ignition timing=>the dwell time at TDC and BDC will be longer on a longer rod,example,if you draw a wave of piston travel where a rod with higher rod ratio will have a more square wave,meaning that the piston moves slower or spend more time at TDC and BDC,
2)reduce the load on the thrust face on the piston,(this has a lot to do with trigonometry)example,take our beloved t135 stroke of 58.7mm and say it has a rod length of 100mm(rod ratio of 1.7=58.7mm/100mm)so take the angle with highest load on the trust face which is 90 degree angle of crank rotation,this result in a rod angle of 16 degree,if used a rod with say 120mm this would result on an angle of 14 degree,a reduction of 2 degrees.so a rod with 0 degree will be upright(Impossible unless you off set the crank)with 0 load on the piston trust faces,but before you go and find the longest rod to put in your bike...
3) rod length can also influence torque/hp too (not going to do the maths)by the same reason as above,shorter rods are more appropriate for lower revs and as the revs increase so does the rod
superturbocompound
New Member
believe you we will simply because you are making an engine do what its not design to do,so basically its a new engine with a t135 skinstroker said:
Haha its oversimplification. As I've said, there's a huge science and debacle over this very topic for ages. Tons of info are floating around. Lotsa yadayada. But main thing is how to apply this into your engine design.superturbocompound said:
A fuller explaination for those interested which I had (quickly) nicked off some chevy nut head:
the rod ratio in a gasoline engine determines the piston dwell at TDC. the longer the rod, the less downwards piston motion will be the result of the rod angle changing.
if the crank rotates 10 dergees, then a very short rod will be at a greater angle than fi the rod is very long. since the rod doesnt change length then some of the pistons downwards motion will be a result of this phenomenon, so the longer the rod, the longer the "dwell" and the longer the dwell the more complete combustion and higher cylinder pressure. The rod length is limited by other engineering conserns, like bloch deck height, piston height, and thus inherrent stability, and resultant wear. and so on.
In most large cubic inch engines it is hard to get a very high ratio. A Stock 350 Chevy has a 1.64:1 RL/S ratio, which is not very good. By increasing the rod length to 6" the ratio increases to 1.72:1, which is much better. You can squeeze a 6.1" rod in a 350 with little trouble, but longer than that requires plugging the piston pin bores after assembly to support the oil rings. It is not worth the extra expense for the little gains, so a 6" rod in a small-block Chevy has become common because everything fits right in. With endurance engines, longer rods are always better. Most endurance engines are using a RL/S ratio of at least 1.9:1 and some as high as 2.2:1. Before you go out and buy longer rods, let me just say that the gains are very small. This debate has been argued for years and will not end anytime soon. In my opinion, if are building an engine and need new rods and pistons, a longer rod will cost about the same. That makes the small benefits worth it. I would not waste my money buying longer rods if you have a good set of rods that you can use. Use that money to make more power elsewhere in the engine.
Rod Angularity:
A longer rod reduces the maximum rod angle to the cylinder bore centerline. Less rod angle will reduce piston side loading; there will be less friction and less bore wear. Less rod angle also gives better average leverage on the crank for a longer period of time. A 5.7" rod with a 3.48" stroke (stock Chevy 350), will have a maximum of 17.774° rod angle. Switching to a 6" rod will reduce that to 16.858°, assuming that the wrist pin has no offset. (on a ford small block, installing the pistons backwards will actually gain almost 20 Hp. since the piston acts like it was mounted on a longer rod, as the ofset is reversed, at the price of increased noise and wear)
Piston Pin Height:
A higher pin height will reduce piston rock and aid ring seal. please no screaming and name calling about anything about a tighter ring pack, we are talking about pin height and pin height only. Moving the pin closer the the center of gravity of the pistons makes the piston more stable.
Rings:
As the compression height is reduced, the space for the ring pack also get reduced. This can be a problem on some engines. It is good for power to have the top ring as close to the top as possible, but this is limited to the strength of the top ring land. As it becomes thin, it becomes weak. High output engines (especially nitrous engines) need a thicker ring land to keep the cylinder pressure from pinching the top ring. In my opinion, if you have to compromise ring location, it would be better to run a slightly shorter rod.
Skirts:
Shorter skirts are usually combined with a shorter piston for a longer rod, but they are not really related. There is no reason to reduce the size of the skirts just because the pin location changed. A shorter skirts are used to reduce friction and lighten the piston. The cost is a little less stability, but it is arguable that a lighter piston with a higher pin height does not need the extra stability. For a street car, I would increase the rod length if it meant a reduction is skirt size. Most of the things listed here are for competition motors to gain a few hp, not worth a lot of effort for most street engines.
Piston-to-Valve Clearance:
A longer rod decelerates toward TDC and accelerates away from TDC slower than a shorter rod, so piston-to-valve clearances are tighter with a longer rod. This may require deeper valve relief's in the piston (but probably not). A short rod is just the opposite, there is more clearance because the piston decelerates toward and accelerated away for TDC faster.
Piston Velocity:
A longer rod reduces peak piston speeds slightly and delays peak piston velocity until the piston is further down the bore, which gives the intake valve more time to open more. Peak piston velocity is usually somewhere around 75° ATDC and since most cams cannot fully open the cam until at least 106° ATDC, it leaves the valve as a major obstacle when airflow demand is at its greatest. By delaying peak piston velocity, even if it's only 1 or 2 crankshaft degrees, it can allow the valve to open another 0.010-0.015", before peak airflow demand is reached. Not a huge help, but a step in the right direction. With a 350 Chevy, switching to 6" rods from 5.7" ones will delay peak piston velocity from 74.5° to 75.5°.
Piston Acceleration / Deceleration:
Reducing piston acceleration / deceleration from and toward TCD will reduce tensile loading of the rod, the number 1 cause of rod failure. A Chevy 350 with 5.7" rods will have a peak piston acceleration rate of 101699.636 ft/sec/sec at 7000 rpm. Swapping in 6" rods will reduce that to 100510.406 ft/sec/sec at that same rpm. That is a reduction of 1189.23 ft/sec/sec.
Intake Runner Volume:
Since it is easier for an engine to breath with a longer rod, less runner volume is needed. This allows more room for an intake system (this is a very small gain, but is real).
Exhaust Gas Scavenging:
A longer rod is moving slower at TDC, which reduces the speed of the exhaust gasses during the overlap period. This reduces the scavenging effect at low rpm and reduces low rpm power slightly (makes the engine run more cammie). A short rod on the other hand moves faster past TDC and increases the scavenging effect and help low rpm power.
Ignition Timing Requirements:
Due to the fact that the longer rod moves past TDC slower, it gives the charge a longer time to burn. So you need less timing for peak power. Using less timing also reduces the chance of detonation; so higher compression ratios can be used. Switching from 5.7" to 6" rods on a 350 Chevy can allow as much as 1 full point increase in compression. In other words, if you could only run 9.5:1 with 5.7" rods, you could run 9.6:1 with 6" rods.
Longer Rod Pros:
Less rod angularity
Higher wrist pin location
Helps resist detonation
A lighter reciprocating assembly
Reduced piston rock
Better leverage on the crank for a longer time
Less ignition timing is required
Allow slightly more compression to be used before detonation is a problem
Less average and peak piston velocity
Peak piston velocity is later in the down stroke
Less intake runner volume is needed
Longer Rod Cons:
Closer Piston-to-valve clearances
Makes the engine run a little more cammie at low rpm
Reduces scavenging at low rpm
Shorter Rod Pros:
Increased scavenging effect at low rpm
Helps flow at low valve lifts (a benefit if the heads are ported with this in mind)
Slower piston speeds near BDC
Allows the intake valve to be open longer with less reversion
More piston-to-valve clearance
Can allow for a shorter deck height
Shorter Rod Cons:
More rod angularity
Lower piston pin height (if the deck is not shorter)
Taller and heavier pistons are required (again, if the deck height is not reduced)
More ignition timing is required for peak power
Actually to be honest, I don't think one had to go to the degree of engineering work I did to achieve similar results. I'm confident of utilising primarily stock T135 parts modified to achieving somewhat in the region of -20% or so in performance.superturbocompound said:
Doing what Im doing as an interest; as a pet project. To challenge myself. Hope I don't sound braggy. Just cant contain my enthusiam in IC engine work. Hope to complete my 'A' race bike soon and post some photos cum specs. As of now still Top Classified Stuff! LOL! Cheers all!