Ka22det

[fo0manchu]

I understand all that stuff datzenmike. But I think we are comparing 2 different things. Here is what I was comparing in my head.

#1 - stock l20

#2 - long rod l20

#3 - l20b rod in a ka or z24 block with extra long rods.

 

I was comparing #1 and #3, and I think you were thinking #1 and #2. Whats your input on #1 vs. #3? This is what I was doing research into awhile back.

Also, as I was re-looking up specs I came across a thread from last year from the realm with you and I in it datzenmike, comparing the ka and L20 crank specs! Man, i gotta save all the data I find next time. Did you ever put together a frankenstein motor with all those parts you had laying around?

 

Hey blackmarkit, what block are you trying to source?

[datzenmike]

Oh, hands down the longer stroke would have more torque even if the engine size were the same.

 

I just this summer acquired a Z22 block. The rods and KA pistons I have. I'm not sure which head I will use but would like to run R-1 carbs, I have those also.

[blackmarkit]

I plan on building a plenum and running motorcycle throttle body's with a AEM ems-4.

[fo0manchu]

Oh, hands down the longer stroke would have more torque even if the engine size were the same.

 

All 3 of those motors would have the same stroke though as they have the same crank.

Good find on the z22 block, those were hard to find in the JY's.

[datzenmike]

Same stroke??? Then nothing much changes between them. Rod length doesn't increase mechanical advantage, stroke increase will, as power is applied over a longer distance just like a lever.

[fo0manchu]

ahhh, just clicked for me in my head. Makes 100% complete sense now. I was thinking that the rod would act as the lever, but instead it is the crank.

[datzenmike]

Long rods have reduced sideways thrust than short ones so less friction at high RPMs.

[ggzilla]

Some automakers say short rods make more power.

Others say long rods make more power. They are probably both right -- it depends.

 

I saw the dyno test results from David Vizard on a chevy 350 his long rod version made 1% more power at 7000 RPM.

 

You can gain more power by raising the compression half point.

[TFM1066]

Long rod/high rod stoke ratio are BAD!!!, people talk about "dwell time" with long rods and thats a good thing, NOT!! your all so wrong. heres my point.

 

what makes air flow into the motor?

 

The piston moving down, "right" or am I wrong?

 

So at TDC exhaust. the exhust valve is closing and the intake is opening "right"

 

So at this point of the cycle why woud you want slow piston travel? when the intake valve is starting to open, piston speed and intake charge is most important till @ 118 degress past TDC this the important part of the intake stoke.

 

High rod stroke ratio are good "if" your turning more then 10,000 rpms just look at indy car or F-1 cars and there rpm limits and there rod/stroke ratios.

 

Most of you NHRA cars are running rod ratios below 1.5-1, stop reading that old book from smokey that was written more then +35 years ago, and if you want to beleive what he wrote thats fine, but that motor was to race at the Indy 500 at 10,000+RPMs

 

Now for the Z22-24 cranks. I run them all the time up to 8500 rpm thats when the soft rev limiter comes in. I run a crank, used from the wrecking yards, unturned (polished only, no balancing), stock bearings that I send out for coating.

 

The L-series head is the best flowing head for Datsun/Nissan motors that money can buy.

The Ka12 valve head flow way better! but is more money (valves,srings etc) The 16 valve far more stable then the 12 valve, and exhaust # flow better due to two valves over the 12 valve

a note on the 12 valve head and this applies to stock or race, The rockers are mounted on a shaft that floats around on the cam caps, Nissan did not incorpperate anything to keep the rocker shafts from moving arond. this is a big problem due to the fact that anytime you disasemble the rocker assembly you have to make sure you have the correct distants from shaft to shaft or the rocker ratio all off which means your cam timing is all off.

Stick to the L head its the best the money can buy or be spent.

[flatcat19]

*their

[TFM1066]

Long rods have reduced sideways thrust than short ones so less friction at high RPMs.

 

So at low RPMs theres no friction loss???? a ratios a ratio. its not dependant on RPM

[flatcat19]

That is not what that said.

 

Who the fuck is this guy?

[EricJB]

Long rod/high rod stoke ratio are BAD!!!, people talk about "dwell time" with long rods and thats a good thing, NOT!! your all so wrong. heres my point.

 

what makes air flow into the motor?

 

The piston moving down, "right" or am I wrong?

 

So at TDC exhaust. the exhust valve is closing and the intake is opening "right"

 

So at this point of the cycle why woud you want slow piston travel? when the intake valve is starting to open, piston speed and intake charge is most important till @ 118 degress past TDC this the important part of the intake stoke.

 

High rod stroke ratio are good "if" your turning more then 10,000 rpms just look at indy car or F-1 cars and there rpm limits and there rod/stroke ratios.

 

Most of you NHRA cars are running rod ratios below 1.5-1, stop reading that old book from smokey that was written more then +35 years ago, and if you want to beleive what he wrote thats fine, but that motor was to race at the Indy 500 at 10,000+RPMs

 

Now for the Z22-24 cranks. I run them all the time up to 8500 rpm thats when the soft rev limiter comes in. I run a crank, used from the wrecking yards, unturned (polished only, no balancing), stock bearings that I send out for coating.

 

The L-series head is the best flowing head for Datsun/Nissan motors that money can buy.

The Ka12 valve head flow way better! but is more money (valves,srings etc) The 16 valve far more stable then the 12 valve, and exhaust # flow better due to two valves over the 12 valve

a note on the 12 valve head and this applies to stock or race, The rockers are mounted on a shaft that floats around on the cam caps, Nissan did not incorpperate anything to keep the rocker shafts from moving arond. this is a big problem due to the fact that anytime you disasemble the rocker assembly you have to make sure you have the correct distants from shaft to shaft or the rocker ratio all off which means your cam timing is all off.

Stick to the L head its the best the money can buy or be spent.

 

So do you disagree that it depends on application? N/A drag racers usually prefer a lower ratio. NHRA pro stocks are typically 1.55 to 1.7. Where F1, land speed, cars are highter. I dont think this is by accident.

In a forced induction/NOS set up, I dont think it matters at all, and I would not try to build a motor around a higher ratio for any application. But I wouldn't completely disregard it either.

As far as fully counterweight VS. partialy counterweighted. I have personaly spun partialy c/w cranks north of 8k as well. Most of them started out with no c/w's and they had to be welded on.

 

So if I read your post's correctly, you run a stockish z24 shortblock, with good pistons to 8.5k. Impressive.

[datzenmike]

So at low RPMs theres no friction loss???? a ratios a ratio. its not dependant on RPM

 

 

Draw a cylinder a piston and a crankshaft where the piston has a variable pin height. The stroke stays the same as does the cylinder and the displacement, The only thing that changes is the rod length... well .. and the pin height. A short rod has a pin that is low on the piston, a long rod has the pin higher on the piston close up under the rings.

 

Now rotate the crank (or draw it) so that the crank throw is out to the side and horizontal. This is the point at which the crank is farthest from the cylinder center line. You will notice that on the very short rod the piston is lower in the cylinder and the rod being pulled much more sideways by the crank than the long rod. In fact the longer the rod the less side ways thrust. An infinitely long rod would have zero side thrust.

 

Why did the L20B gain 2cm of block height? Why didn't Nissan just use an L16/18 block? Because as the stroke increases the rod length should too. The Z24 is 2cm taller than the L20B same thing. I don't know what the ideal rod length is, I'm saying that long rods have reduced side loading, where the piston is pulled against the cylinder.

[TFM1066]

rod ratio, who cares??

 

by Darin Morgan » Thu Oct 28, 2004 5:17 pm

shawn wrote:I'm sure Darin Morgan will comment on this.They have a lot of experience wth testing different rod lengths. Here's a quote from Reher-Morrisons site from David Reher and his thoughts on the subject-

 

" We also wanted to point out some of the common myths and misconceptions about high-performance motors. For example, I've seen dozens of magazine articles on supposedly "magic" connecting rod ratios. If you believe these stories, you would think that the ratio of the connecting rod length to the crankshaft stroke is vitally important to performance. Well, in my view, the most important thing about a connecting rod is whether or not the bolts are torqued!

 

If I had to make a list of the ten most important specifications in a racing engine, connecting rod length would rank about fiftieth. Back in the days when Buddy Morrison and I built dozens of small-block Modified motors, we earnestly believed that an engine needed a 1.9:1 rod/stroke ratio. Today every Pro Stock team uses blocks with super-short deck heights, and we couldn't care less about the rod ratio. A short deck height improves the alignment between the intake manifold runners and the cylinder head intake ports, and helps to stabilize the valvetrain. These are much more important considerations than the rod-to-stroke ratio. There's no magic - a rod's function is to connect the piston to the crankshaft. Period."

This is located in the tech article "by the book" if anyone else wants to read the whole thing. Hope Darin does comment on this, he has some deeper thoughts on this with a GM backed test to back them up.

Shawn

 

DITO shawn.

You pretty much summed it up.

People put WAY to much importance on this preconceived " ideal rod ratio" idea. Rod ratio is not a primary consideration when designing an engine. You get the deck as short as possible so the piston does not come out of the bore. That gives you better manifolding which will make ten times the power any " ideal rod ratio" would net you. You shorten the pushrod and make the valve train stable above 9000rpm. You make the piston ring package as compact as possible to get the pin as high as possible and that will make for a light weight, balanced (not top heavy) piston design, THEN you decide what rod connects the piston to the crank. Its not magic, its simple mechanics. People look at what Smokey yunick said and they take it out of context in my opinion. He said you should put the longest rod YOU CAN not the longest rod YOU CAN CRAM JAM OR MANIPULATE into the engine. I see people all the time screw up the engine combination to facilitate some preconceived ideal rod ratio and they wonder why the thing wont turn up and make power. The difference in the GM 358 NASCAR test engine from 5.250 inch long rods to 6.1 inch long rods was maybe 2ft/lbs and 2 HP. Not much to worry about. That satisfied the GM engineers that there is nothing there. Does a short rod make more TQ? Does a long rod make more top end power? It probably does but its such an insignificant amount, its not even worth messing with! If there was a major advantage or power gain in this, it would have been proven a long time ago and we could all put this to rest but no one has. I wonder why???????????

 

Darin Morgan

R&D-Cylinder Head Dept.

Reher-Morrison Racing Engines

1120 Enterprise Place

Arlington Texas 76001

817-467-7171

FAX-468-3147

 

Visit our web site at

http://www.rehermorrison.com

[flatcat19]

That guy must be right then.

Building a racecar motor is the way for everybody to go.

And everyone else is just wrong.

Take note and do it that guys way.

 

We should have have a spot of tea and praise the almighty correct one.

 

 

 

Dude. Were not building race motors.

Drivers. For regular cars. For old cars.

 

I'm sure you know tricks we don't, and have enough experience to back up a portion of your knowledge.

But to continue with the condescension the way you have?

Slow it down.

 

[EricJB]

Well, all opinions aside, Darin Morgan is the man. No, I'm not being sarcastic. I'd give my left nut to pick that guys brain. But I'd probably just get into a rod ratio argument with him.

[ggzilla]

Rod ratio is not a primary consideration when designing an engine.

Dude. Were not building race motors

 

Whey don't we get back on topic about building a cool KA22DE-T ...

[datzenmike]

I don't know if there is a perfect rod/stroke ratio and am not saying there is and what works in theory for a pushrod chevy might not for an OHC 4 cylinder motor over half the size don't you think? What do Nissan/Datsun engine builders say?

[fo0manchu]

Whey don't we get back on topic about building a cool KA22DE-T ...

Ditto. I never started my frankenstein motor build because i didn't have the time or money to. To be honest, my ka24det would probably run faster anyway. But why do it? 1. Its fun 2. because you can 3. its different and cool 4.Why not? IMO i don't think anybody here is trying to prove that destroking a motor with long rods will create better power. I think its just fun to make frankenstein motors. Like putting together a big puzzle. If you have time and money, go for it.

[datzenmike]

The KAs been done. (no offense) No one has a pure ride, everyone has something added from another Nissan product or elsewhere. If we didn't try stuff we would still be living with our parents. I would love to try an LZ23 but with some weird stuff.