Would loosing 3.125mm of stroke be worth tradeing for a 1.67 rod ratio?
I don't want to tell everyone my plans until I'm 100% sure things and parts will come together.
its a trade out.
just like gaining high end hp by losing low end tq.
the stroke ratio is a trade out as well.
each has its pros and cons...you simply need to weigh which you want the most and go that direction
oh god what are you dreaming up now?
If it takes forever.... I will die trying. Underdog Racing
depends on what you want.
how are you reducing the stroke?
if you say with a shorter rod I'll hit you.
If you want displacement, stick with what you have. If you want dwell and reduced cylinder wall loading losses, then there's already an engine with a 1.75 R/S (and larger bore) that's essentially plug-n-play...no reason to mess around with machining offset cranks or what have you. With a 91mm stroke, you are displacing barely more than the Quad4, anyways. I'm all for new ideas, but I foresee alot of headaches and money spent for essentially a parallel shift, rather than a real forward progression.
I have no signiture
agreed..if rod ratio and high revs is what you want then the quad 4 has all that already in a stock package...dont think i would waste time machining, just start with what is closest to what you want to begin with
Haha not with a shorter rod PJ. Brad and I have been talking about offset grinding the crank for more stroke and also looking into custom rods. We were having trouble finding big enough bearings to have an offset worth going through the effort. I started thinking if im getting custom longer rods made anyways why not get the big end of the rod made smaller. I found read about the sbc guys turning their cranks down to 1.89 and using a honda bearing, which would be too wide for the 2.4 by .023. A rod journal of 1.89 is .125inch or 3.25mm under our rod journal size. So I still need to find a suitable bearing.
Destroking by .125 or 3.25mm would allow me to run a 6 inch rod with a rod ratio of 1.67-1 and still have enough meat on my pistons to not burn through. This is .13 better rod ratio than a normal 2.4 or .08 better than a 2.4 with 2.3 rod. Granted it would drop down to a 2.3 displacement I would still have 6mm more stroke than the average 2.3. As for dropping in a regular 2.3, I feel it lacks stroke and lower end torque and you are going to rev the piss out of it all the time to get the power. Realistically monetarily it would only be the price for the journals being turned down and bearings that would be different since I fully intend on shoving the longest rod in the engine I can even if I dont offset grind. Im tired of reading about the same old build all the time, eagle rods, Wiesco 9-1s, HO cams. Although tried and true I want to step outside of the box and try something different just like some others on here currently building. Also if I were to bore the engine out to .080 over or stock 2.3 bore I would be right back to a 2.4. Im just not sure I want to buy pistons when I already have a set.
I guess I should have asked will loosing .1 liter of displacement be enough of a power difference to counteract smaller bearing surfaces, therefore less rotational friction, along with longer dwell time, and a better rod ratio and still more stroke than a 2.3?
you gotta remember though man... with such long rod's your prolly gonna need to clearance a butt load. maybe even the bottoms of the cylinder bores...
but, if your cool with that id say drop the bomb!
If it takes forever.... I will die trying. Underdog Racing
Tiny rod journal FTL, gotta remember that the SBC guys doing this are budget minded and the engine most likely will not see more than 5k rpms. Not trying to sway you away from trying this but loseing that much meat off the rod journal seems like a disaster waiting to happen, since a 4cyl crank has more torsional vibrations than a V8(V8 is a smoother running engine). sorta the same problem with turning down 2.4 crank main journals to fit in 2.3 block. Journal gets to small and BAM disaster.
There are better,albeit more expensive, ways of doing long rod setups. The ideal way is to do longer rod matched to a shorter piston(All custom made obviously). But IMHO swapping to 2.3 would be the best route, and as Brad said, you will most likely need to clearance the bottoms of the bores for rod clearance. You can take what V8 guys do with a grain of salt, some ideas still apply but some dont. SBC guys have it good with an ENDLESS knowledge base and HUGE variety of parts available.
we havent reached the limits of our crank yet.
thats all im going to say.
If it takes forever.... I will die trying. Underdog Racing
Actually from what I was reading they do it for performance benfits and high reving. It is common to see in nascar sbc's and lots of power making imports have this sized journal.
I don't want a quad4 2.3, not enough stroke for me. And from what I see on quad4forums and here you need to put a lot into them N/A to get not so impressive numbers. This idea is intended to try and get a better rod ratio than a 2.4 and more stroke than a 2.3.
yes i really dont think that cutting the journals down will even phase our crank.
we know they can take 550+ whp and 25 psi no problem.
we know they can take 8000+ rpm when GUTTED for many laps no problem.
we know they can take the mains being cut down for use in a stroker engine no problem.
any questions?
If it takes forever.... I will die trying. Underdog Racing
I still dont see why youd want to cut down the surface area of an oiled surface. Sounds like a disaster waiting to happen at high RPMs if you ask me.
smaller journals decrease bearing speed at high rpm... pretty sure it helps for oiling too. But I admit, I'm not very well versed in this area.
DaFlyinSkwirl (Pj) v2.0 wrote:smaller journals decrease bearing speed at high rpm... pretty sure it helps for oiling too. But I admit, I'm not very well versed in this area.
From my logic (which is probably flawed) Id think that you would have the same clearances and a smaller journal so thered be less oil on the journal in general. I done see how the speed would be decreased as the rod is rotating farther around the journal at a given RPM. Its very possible Im wrong too.
as long as the oil fillets are in tact i dont see any issues with having a smaller bearing journal.
i mean if it was a problem why would there be .75mm bearings available?
If it takes forever.... I will die trying. Underdog Racing
z yaaaa wrote:
i mean if it was a problem why would there be .75mm bearings available?
For grandma driven cars that dont see any abuse...thats why
LOL
too each his own i guess but id bet my left arm the LD9 crank could take the abuse and laugh its ass off doing so.
If it takes forever.... I will die trying. Underdog Racing
TheSundownFire (GME Chat) wrote:I still dont see why youd want to cut down the surface area of an oiled surface. Sounds like a disaster waiting to happen at high RPMs if you ask me.
i cut mine and once again i dont have a problem. Have to turn down the mains to fit a 2.4 crank in a 2.3 block ...never had an issue.......
8000 rpm on turned down mains and stillll goingggggg
by reducing the size of the journal, you decrease the distance the bearing has to spin when speaking in terms of circumference.
less circumference = less distance traveled per RPM = lower bearing speed.
less oil is needed to lubricate a smaller area, which means that maintaining lubrication at high RPM will be easier.
you can do this to mains AND rod journals.
DaFlyinSkwirl (Pj) v2.0 wrote:by reducing the size of the journal, you decrease the distance the bearing has to spin when speaking in terms of circumference.
less circumference = less distance traveled per RPM = lower bearing speed.
That almsot seems counterintuitive. Id figure that being smaller it would turn faster but I guess not.
Im terrible at explaining the things that go on in my head so Im just going to shut up.
I guess I'm seeing both points here. The speed would be reduced as PJ is pointing out but at the same time there would be less surface area for oiling... but if it's working for scott at 8K maybe someone should just try it and see.
Brain, think distance traveled per revolution. farther from center is a longer distance per revolution.
as long as the certain thickness of oil is maintained, you're fine.
having a smaller area to keep oiled will be easier on the oil volume/pressure you have available. this will HELP oiling.
in terms of the cirumference change.. you're thinking backwards. something LARGER turns faster.
lets do a hypothetical.
2" journal. circumference = 6.29"
1.5" journal. circumference = 4.712"
RPM for both is the same, say 8000rpm.
for the 2" journal, this is 50,320" a minute.
for the 1.5" journal this is 37,696" per minute.
same rpm. but smaller journal travels less distance in the same amount of time. this means it has a lower speed, and thus generates less heat and will more likely than not survive longer at higher RPM.
again, this is just an example.. you cannot arbitrarily shrink a journal without directly effecting strength. you need a balance of both.
