since the advent of the very affordable Hot Rods Stroker Cranks i have gotten lots of PM's....and read lots of thread titles....with the question being which was a better way to go... Big Bore VS Stroker

my answer to everyone has been:

within the amount of bore or stroke change we are talking about in these engines.... you should pick whichever one you either want to replace....or need to replace... because at these levels of change...it is merely a matter of ultimate displacement increase as to what the engine will perform like...as opposed to one changing your engine into a big bore\ short stroke screamer...and the other into a long stroke stump pulling tractor.....

at these levels...it is pretty much cc's of displacement change...and that's it

so it would be up to what someone either like more...or has to change out of necessity.....

the graphs i have for comparison aren't apples to apples.... but it's the best i've got to show.....

the RED lines are from last summer when my own TRX was a 477cc \ 99mm bore setup (stock is 96mm)

the BLUE lines are my TRX right now as a 471cc stock bore 3mm stroker

i've included the A\FR runs for clarity of what's going on on the bottom of the RPM band...... i try to jet for an average A\FR between 13 & 14:1..... the blue runs @ 477cc are way too rich from the accelerator pump shot until the pump shot is burned off @ around 7000RPM... once the air\fuel ratio comes up into good, so does the power curve..... i didn't tune that out of the accelerator pump shot during my dyno testing because nailing the throttle in top gear, at low rpm, where the engine would take the longest to burn off a pump shot....isn't representative of how it works during actual riding conditions....now, for comparison, i wish i had turned down the accelerator pump shot.....

like i said... not apples to apples.... but it's the best i have for 3mm bore VS 3mm stroke comparison....

hope it helps some of you make your decision easier...... once Hot Rods affordable big bore cylinders come out...the answer might just become: do both....lol.... the price of the Hot Rods Stroker + Big Bore cylinder doesn't even come up to the average price of the currently available big bore cylinders alone.....

Click to view attachment

Click to view attachment

very interesting, the big bore/stroker was only aout half a HP more than the stroker alone

i would love to see a dyno of this same build as just the big bore, with stock stroke that would really help comparison

nice comparison mixxer. hondaman, i think you made the same mistake as i did at first. the 477 is the big bore only. and the 471 is the stroker crank only. not the combination of both. his description says +3/99mm bore. the +3 is the bore, making it 99mm. i was confused also.



mixxer, your right about waiting on the new cylinders. i am glad i have held off. i believe i am gonna do both. i really want to have that venom big bore as my build of choice......but....... i fear that stock crank. just hate to ruin all those new parts. plus, last winter it had some wear in the wrist pin journal, so im gonna change her out. sure is gonna push me for time though. waitin on that tax return. hope to have a gt thunder dyno after all is said and done. 2 hour drive from home.

as soon as you hear where one of those cylinders can be gotten, i want to know!!!!!!!! thanks good info

BLUE is a big bore only @ 477cc's

RED is a stroker only @ 471cc's

no big bore\stroker combo here.....

the plus 3mm i wrote meant +3mm bore... from 96 to 99mm

i'll change it to make it more clear!

ohh i see well that makes for a great comparison then its basically what i was wanting they make about the same exact HP the stroker makes more down below, but with the BB being able to rev quicker might make a little difference on the strip

Mixxer thanks for the comparison. Which cam were you running on these builds? This is just what a lot of us were looking for.

in these graphs it isn't a fair comparison at the lower rpms.... the A\FR curve is WAY too rich from the accelerator pump hit on the big bore graph....power suffers until the A\FR recovers up to the correct 13ish range.....

glad to help with the comparison!

Hot Cams Stg 3....

but for my own michigan off roading i prefer the Hot Cams Stg 2

mix, pull out a comparison of these two quads with a time vs. speed graph, pretty please...

any comments on how fast the two revved comparatively? did they both rev quick or was one 2 stroke snappy and the other a little more Rappy oriented (not that extreme tho, I'm sure).

Scott,

the lessened initial hp on the graph with the excessive accelerator shot would make the comparison meaningless..... jetting would have to be perfect for both machines at all rpm...AND i would have to had set the dyno up in its "auto-start\stop run mode"... where it doesn't start & stop manually by the pendant controls...but rather at pre-set drum speeds......



i copied this from an answer i gave in another thread to a similar question.... :




OK...here's the deal.....

time to put on your thinking caps everyone..... this is going to be real simple....and i'm going to explain it thoroughly....

if you don't get it...then think about it until you do before raising your hand to argue....lol .....

the dyno will always keep track of the time a run takes..... that's how it works ....measuring the amount of acceleration VS the time it took for that acceleration.... is EXACTLY how the dyno determines the power it took to do just that.......

BUT.....

if you want to directly compare timed runs to timed runs....you HAVE to setup your dyno to do this.....

when i'm doing dyno runs i hit the green "acquire" button and then whenever i feel like it i hit the throttle.....i can wait zero seconds...2 seconds...5 seconds...before the throttle is hit and it doesn't mean a damn thing to the dyno...the dyno run itself will look the same when there is acceleration VS RPM occuring......

now...if i do 2 runs... one with a ZERO second delay from hitting the button to stabbing the throttle...and one with a 5 second delay from hitting the button to hitting the throttle....

they would both look exactly the same when you use the rpm as the bottom axis of the graph..... BUT...if you used time as the bottom axis of the graph...the throttle stab with the least delay after hitting the acquire button would appear (falsely) to have a massive advantage in acceleration....


so here's the deal..... you have to specifically setup the dyno to do any time comparison runs that would mean anything.....and you do it with the programming....

you CAN set the dynojets to begin run\data acquistion automatically ...start\ stop dyno runs @ pre-set drum mph speeds......

and those....and ONLY those type of dyno runs can be accurately compared on a time scale....! if you don't do this, you can make anything look like anything you want...and that isn't any sort of comparison...

i don't bother with those run types ever .....for this reason.....

when you have rpm as the bottom scale axis...and power as a vertical axis... you can accurately compare any engine at any time.....

rpm is an absolute measurement.....and so is the acceleration\ power....

and on a dyno.... acceleration is measured directly as power.....if you see more POWER at any rpm it is EXACTLY because there was more ACCELERATION occuring at that rpm...... pretty simple right??

you wont see a higher HP reading at an rpm because there was less acceleration occuring will you??!!

don't be silly....lol....

higher power = higher acceleration rate per rpm traversed..... if something is accelrating harder it shows up as more power @ that rpm on a dyno......

that's sort of EXACTLY how the dyno works......

there is no such thing as a cam that shows less power per rpm on a dyno...while it is accelerating faster....or any other performance part for that matter.....

how'd i do on that explanation??

mix, you basically nailed it there, haha

i have always been curious about how dynos got their readings and stuff. i had a rough idea but you layed it down just now

I agree also that a 471 stroker n a 480bore are really close my bros was 4-5 hp below mine I had a ported head vs him no port then he has a web943 vs my hc2 I think ithb the exact components they'd be wihin 1hp n 1tq

anybody ever test a 943 vs a hc2 what made more power ?

good info..peace jim

thanks for that...

good comparison jim....

the 943 cam is the most radically ramped cam i know of.... randy lyman \ rlspeed \ 577cc told me he measued the admittedly radical \ dangerous 208 web cam on his cam analyzer....and then the 943...

he said the 943 was much more radical\ dangerous than the 208...and that after measuring the 943 he wouldn't recommend anyone running it.....

steep ramps make great power....but it isn't without a penalty.....

We was actually unaware of the steep ramp rates and hard wearing that this webcam was at the time my bro called a place and ordered cause he was told it would make better power.. if he keeps it I don't know maybe hell take my stage 2 when I put the stage 3 in

he hasn't done too much to his build caue he's a 100 lbs lighter then me and can keep up but when I add more power n get faster he'll follow right along...haha

i have re-worked several heads that very prematurely trashed the exhaust guides and intake valve\seat setups with the 943.....

it's got to be hell on spring life too....the 208 is...and the 943 is worse yet.....

John,

I agree the 943 ramps are steeper than the 208 in places along the lift curve. I did use the word "radical", but I NEVER used the word "dangerous" when discussing either cam. And, what I said about the 943 was "It makes me think twice about recommending the 943 until I can get more than 100 hours or so on one myself."

I would appreciate accurate use of my words if I am going to be quoted.

Thank you,
Randy

all apologies Randy....

from personal experience on my own machines and on customer's repairs, the 208 is already too radical in my book....and the only thing that "radical" really means is "dangerous" as far as valvetrains are concerned...it can mean nothing else

i only remembered only the gist of you saying not recommending , and more radical than a cam i consider too radical already....

i wasn't trying to quote you....no quotation marks at all...... only convey the gist of the topic......

again...all apologies.....

in the future , i will cut & paste .....

John,

Apology accepted. I agree both cams are a little radical for bolt in. The 943 will bolt in with stock springs and guides, but I do not know how well the valve train will hold up until I get at least 100 hours on mine. It does have some Very steep ramps!

Everyone is entitled to their own opinion and in my opinion I agree that the 208 is not a “drop-in” cam, definitely requires good aftermarket springs, and should have the lash checked every 10 or so hours of riding. I would consider it to only for those who are serious about maintenance and only if they need every last bit of power.

I realize you have a stronger opinion about the 208 that is based on a lot of experience -- I will not try to persuade you otherwise.

cool beans Randy...

thanks for accepting my apology

I believe the 943 was tested against the HC2 and if memory serves - it was nearly identical... Of course it depends on the build somewhat...


Are you guys sure you are not talking about the 493? That has been referred to as the little 208 by some ppl....

i probably got the numbers wrong....the tiny 208 is the one ....

493

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