Long Rod 2.0L questions

[sleepydsm]

I only recently have read about a long rod 2.0L engine.

Apparently you get a nice torque boost similar to doing a 2.3L stroker (because of the longer rod)

Can someone explain to me exactly how? Is there were a simplified image of a triangle comes in and the now longer rod forms the hypotenuse of the triangle, the crank a short leg, and the other leg I think the wrist pin to crank center?

Also, people claim much higher revving ability mostly in part to a much physically smaller and lighter piston. But doesnt this long rod (156mm) combo have a worse rod ratio than say a regular 2.0L?

[turbotalon1g]

Lol at you, you will never leave dsms hahahaha

[Super Bleeder!!]

I think the long rod stuff is totally blown out of proportion with respect to results compared to a stock rod motor.

Also, the longer the rod the better the rod ratio gets.

I seem to remember a honda based magazine doing an article on this exact topic. They built up a stock length rod motor and dyno'd it. Then took it apart and changed out the rods/pistons for a long rod setup and dyno'd again.

If memory serves correct the stockish rods prevailed.

[Tachyon]

It's slow at work, so I'll create a diagram.



As you can see, the angle is a bit different. However, it's very marginal.

Stock R/S = 1.70

2.0 Tall rod = 1.75 (whee..)

There might be some gains due to greater piston dwell at TDC, however I would be very hesitant to expect any real noticeable gains with that small of a change. (and I am usually the "go for it" guy when it comes to weird stuff). While I have no proof for this exact build, I would suggest the price of custom pistons is not enough to offset any performance gain unless you were also doing high compression, reverse offset, gas porting or something else to warrant the custom pistons.

[Super Bleeder!!]

Nice diagram!

[sleepydsm]

You can use off the shelf 2.3 stroker pistons. And I guess reading more the biggest benefit is the combos ability to rev as pretty much everythingon the piston below the wrist pin is removed.

[sleepydsm]

Thanks for the info.

[Super Bleeder!!]

As if stock rod length 2.0s have any trouble revving? Niqqa plz

[Tachyon]

Originally Posted by sleepydsm

You can use off the shelf 2.3 stroker pistons.

I made a critical error in my haste yesterday. Long rods are 156 long, not 154... not sure why I posted that.

This would bring the B/S ratio to 1.77

That being the case: The stock 2.0 piston has a 35mm compression height, with 0mm deck clearance. The 2.3 Wiseco stroker pistons (using them for this example since I have the numbers handy) have a 28.7 compression height with a .3mm deck clearance. Assuming you use a 156mm rod:

35-28.7 = 6.3. so you would have a .6mm final deck clearance.

If you installed Wiseco's stocking piston: K571M855 (28.7mm), with the long rod (156mm) and stock crank (88mm). You would end up with a final static compression ratio of 7.4. That seems far to low to be able to rev that quick.

I'll hunt down some numbers for other stroker pistons.

[niterydr]

So..what magical transmission is going to shift at the 10500+ rpm the long rod is capable of? Also, I am curious to see how much money will be spent on head and intake manifold design to make usable power that far up?

I remember when Mike from QPR was obsessed with this and taking over the world when it was completed...sigh.

Works great in theory, but I really don't see the point in it. If it works, good luck and post results!

[goodhart]

Originally Posted by niterydr

So..what magical transmission is going to shift at the 10500+ rpm the long rod is capable of?

a dog box? lol



Also, Shep claims his stage 4 will shift at "10,000 rpms with ease" with a properly working clutch.

[Pushit2.0]

Originally Posted by goodhart

a dog box? lol



Also, Shep claims his stage 4 will shift at "10,000 rpms with ease" with a properly working clutch.

The latter part of that quote meaning everything. Let alone as stated above 99% of the dsm's out there would be hard pressed at making usable power that high in the rpm range to warrant a shift point at 10k+.

~John