NirVTEC

A question was asked by a local friend of mine about the 89x90.7 build. I went a step further and added the 87x95 to the equation.
Assuming same compression and surrounding mods, what difference would be seen if any?
89x90.7/143mm rod=2257cc/1.58 r/s ratio
87x95/141.5mm rod=2259cc/1.49 r/s ratio
Seems like the 90.7 stroke would be kinder to higher RPM.....and dwell would be better for air-flow.
And the 87x95 would beat up bearings more.....

Discuss......

crazydominicanman

Why?

SteelcityLude

wondering the same thing. it looks like he already answered his own question

NirVTEC

Does the R/S ratio just simply knock the 95mm out if a decision had to be made?
Obviously the 89mm x 90.7mm is going to be quite a bit more money.......

SteelcityLude

well i guess it matters what the engine's purpose is the 95mm is more than likely going to make more low end torque and fall off up top

Professor15

If you search on here you can find a lot of debates that were had about r/s ratio. From what I took of it, it's just a number that really doesn't factor much into a street motor, considering there are cars with 1.4 and on kicking ***.

I'm sure there are people that are going to say otherwise and throw a whole bunch of theory into this. 9 out of 10 times those guys dont have the proper data and testing to validate those theories tho. Lol

SteelcityLude

i would say this is true on a street motor, but when it comes down something other than street its like just because people are doing it and kicking *** doesnt mean its ideal, its not a theory that was developed on ht.

NirVTEC

even if both engines have nearly the same displacement?

Professor15

Well then what would you consider ideal ?

I know it's a theory not developed on HT. But it's a theory VERY FEW have proved and disproved, and Im sure even fewer are willing to give that kind of info out.

Considering the majority of us are building street motors and not race motors for different types of racing event, I'm sure we won't benefit from pouring alot of time $$$ and resources into testing an ideal r/s ratio.

SteelcityLude

yes. i would say 89x90 would be better for an all motor app and the 87x95 would be nice for a lower rpm long geared turbo setup

SteelcityLude

here ya go taken from a ford site lol

http://www.fordmuscle.com/archives/2...ker/index2.php

Rosko

iTrader: (1)

Yes, its got to do with the angle the rod is pushing on the crank and for how long. The bigger crank swings a bigger circle, its almost like a gearing thing if you think about it.

The r/s ratio is pretty insignificant if you ask me. In some motors yes, but if you actually draw up the difference in angles it is VERY minimal between these two and I dont believe its worth addressing on a street motor.

Rosko

iTrader: (1)

But they read it on the interwebz so it must be true right???? LOL I like that post

CHEETAH

iTrader: (2)

the H: means its an H-series setup?

on a K-series utilizing the VTC it makes a difference, and the 1.4 rs setup can even win, but with the H and B-series with "fixed" cam timing, the relative RPM/airflow is a constant based on overlap due no adjustability of the cam's timing events, so the longer RS setup might be prone to win.

If its on a Skyline or Porsche motor with both intake and exhaust cams have adjustable cam timing, the RS difference prolly wont matter.

then you also never accounted for using the same camshafts too...that makes a huge difference because you can make a cam best suited for the 1.4 and a cam best suited for the 1.58

BTW 1.58 vs 1.4 isnt that huge of a difference.

again dyno or HP numbers won't be the only deciding factors...

gotta love benchracing lol.

Pippen_001

Cheetah made an interesting point about the VTC stuff.
I know has nothing to do with an H-series. But still good info.

Professor15

Lol that's all nice n dandy. But how does that theory correlates to me winning and losing races? What TESTING has been done on our engines that would prove or disprove that. That's what I'm getting at.

Anyone and everyone can come up with and shoot down theory's until their face turns blue. Without proper testing, it all means squat.

SteelcityLude

alright who has 2 h22's laying around and some cash to burn someone has to do this test now. and like said, i think cams are going to make power difference between the two

Rosko

iTrader: (1)

Cams would deffinately do different things on each motor, but alot of that could be helped by adjustable gears too. What works for one may not be what works for the other.

That would be quite the dyno test haha

SteelcityLude

Troof!

Professor15

The only way that test would be feasible would be on an engine dyno. But you would also have to tailor each engine to their strong suits. so i would image that the cams, im, headwork, exhaust set up on one motor configuration wouldnt be ideal on the other. Lol thats alot of work to conduct a test just so we can say " well X worked on the dyno compared to Y, now lets see if that means anything on the track LOL "

f20b jones

I can show you a dyno of two h series both 12.1 compression ,both head poerted by my dad ,both 88mm pistons ,Mine has a h23 crank (95mm), The other has a h22 crank (90mm). Both rmf replica header similar exhaust and intake . The only major difference is the 90mm stroke was h2b and the 95mm stroke was strait h which might make a small difference because of the gearing . My motor made 252 hp 182 tourqe ,His motor made 251hp 173 tourqe very close . The smaller stroke peaked about 500hp higher (it also had alot lower geared tranny ).

The kicker is the 95mm stroke made almost 20 more hp over the power band and ran half a second faster in a car that weighed 500 pounds more .

Both had pro 2 cams also. Unless you built two motors to test you couldnt get any closer then these two were . Ill try to post the dyno later. I actually had my tunner over lay my dyno on his just to see the difference when we had it tunned so i have a dyno graph to prove this.

SteelcityLude

500 hp eh? lol... idk thats not a close enough comparison and i think the head work might be a little iffy to compare the two along with everything else its just not close enough, we are talking mod for mod possibly on an engine dyno back to back

Professor15

In your opinion, do you think both of those set-ups are utilizing there configuration correctly ?

NirVTEC

I know a lot of people say its all about ETs and NOT dynos.....but that doesn't hold water with me at all.....I'm a RoadRacer.
Too many variables to compare....A dyno is a lot simpler.

SteelcityLude

me? yes i do. but there are too many variables involved in the comparison of them we need both engines assembled pretty much at the same time with the exact same everything, preferably with a stock heads or both ported and seeing a flow bench and flowing exactly the same