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Sun Jun 14, 2015 3:36 pm

I'm building a 2110 ....what rod ratio should i use

Sun Jun 14, 2015 4:05 pm

1.670 would be best

Mon Jun 15, 2015 8:34 am

cb650 wrote: I'm building a 2110 ....what rod ratio should i use

Building it for what? Land speed record? Trike? Bus?

almost like asking what color the sky is....

Mon Jun 15, 2015 3:48 pm

midtravelmidengine wrote: cb650 wrote: I'm building a 2110 ....what rod ratio should i use

Building it for what? Land speed record? Trike? Bus?

almost like asking what color the sky is....

Drag race....street/strip car..

Mon Jun 15, 2015 4:08 pm

I feel that choosing rod length to make the engine "assemble right" is more important than the rod ratio. IE: You don't want to have to hack the tins and exhaust to make them fit.

Mon Jun 15, 2015 7:28 pm

While John is absolutely right in recommending the rod that makes everything come together nicely - I would rather jump some hoops to get as long a rod as possible.
Long rods produce more horsepower, and better mechanical efficiency.

Mon Jun 15, 2015 7:29 pm

cost is another issue. Sure you can use C pistons and 5.7" rods, but you aren't going to be able to do that with a $170 P&C set.

Mon Jun 15, 2015 7:35 pm

Boolean wrote: While John is absolutely right in recommending the rod that makes everything come together nicely - I would rather jump some hoops to get as long a rod as possible.
Long rods produce more horsepower, and better mechanical efficiency.

How much more HP? on a 2110 are you talking about 1/2 HP or 15 HP. I think rod ratio is grossly overated in a 150 HP VW engine. Build whatever make it easiest to build.

Mon Jun 15, 2015 8:22 pm

Maybe 5-10 hp? Just guessing here. The main point would be mechanical efficiency. Extreme sideloading of our cylinders promote engine case movement as well as cylinder and piston wear and fatigue.
It's not a linear function - a bit better rod ratio goes a long way.

Tue Jun 16, 2015 8:16 am

Boolean wrote: While John is absolutely right in recommending the rod that makes everything come together nicely - I would rather jump some hoops to get as long a rod as possible.
Long rods produce more horsepower, and better mechanical efficiency.
I couldent of said it better my self.

Tue Jun 16, 2015 2:38 pm

Boolean wrote: Maybe 5-10 hp? Just guessing here.

I guessing it won't be more then one or two HP on a typical 150 HP 2110. Anybody have any actual dyno testing to prove me wrong?

Tue Jun 16, 2015 3:08 pm

Not everything about engines is measured in hp. Getting more miles from your engine has value, too.

Wed Jun 17, 2015 6:31 pm

vwracerdave wrote: Boolean wrote: Maybe 5-10 hp? Just guessing here.

I guessing it won't be more then one or two HP on a typical 150 HP 2110. Anybody have any actual dyno testing to prove me wrong? You may well be right about that. But that doesn't detract anything from the efficiency/wear issue though.
If I wasn't so lazy I'd love to do the dyno test.

Thu Jun 18, 2015 4:51 am

Do you guys really think .200" longer rods are magically going to give you an extra 50,000 miles of engine life?

What a racer does with an 8000 RPM race engine is sometimes pointless on a street cruiser engine that only sees 3500 RPM highway cruising speeds.

Thu Jun 18, 2015 5:25 am

3500 rpm engines are of no interest to me.

Thu Jun 18, 2015 5:32 am

But if my engine goes a few races more between rebuilds, that's totally worth it.

Thu Jun 18, 2015 7:28 am

Boolean wrote: 3500 rpm engines are of no interest to me.
ditto....I think I like that way this guy thinks :wink:

on a side note what is the oe rod ratio??? and what is it on a 84 stroke with 5.6 rod? 86 with a 5.6 rod? 86 with 5.7 rod?

Thu Jun 18, 2015 2:48 pm

mark tucker wrote: on a side note what is the oe rod ratio??? and what is it on a 84 stroke with 5.6 rod? 86 with a 5.6 rod? 86 with 5.7 rod?

Did you flunk grade school math? Divide rod length (mm) by crank stroke (mm), it is that simple.

5.600 rods (142.2mm) divided by 84mm stroke = 1.692 rod ratio
stock 5.394 (137mm) rods divided by stock 69mm crank = 1.985 rod ratio

Thu Jun 18, 2015 4:27 pm

no dove I know how, but i needed to make a point. look at those figures of Your's the short rod is already way more ratio them the long rod stroke combo.so........get it now??? just how long would a 84 stroke crank need a rod to be to just equal a vw rod ratio for the angles vw had intended for these engines.....and we all know that vw did thier homework and just didnt throw a long rod high ratio in the engines when they could of made the engine somuch narrower and lighter too.

Thu Jun 18, 2015 6:32 pm

In this day and age, car company's may very well design entire engines around a rod ratio but I doubt very seriously that they did it 70 or 80 years ago. I'll bet they didn't give it much thought at all.