Ka22det

[datzenmike]

As for the coming short I the deck you can use a ford 5.4 connecting rod which is 169.0878mm with the crank and piston pin height it comes out to 246.0878mm. 1.3622mm short of the deck. Compression would be 9.29:1 the rod ratio is high a 1.966 but that's why I think it would make a great turbo motor. The long dwell times would allow time to charge the cylinder sence it's under pressure. As for the question what is the benefit. Well sence the l20b is fully counterweights and can handle around 9000 rpm vs the ka which experiences vibration at 7200rpm and case premature wear. There's is a formula which CID x .5 x max rpm / 1728 = cfm

Granted that is 100% ve. So you multiply that by .85 which is 85% ve. As you will see the smaller motor will make more power.

 

Z24 block

Z24 or KA24E piston

169.0878 mm Ford rod

L20B crank

 

Agree 246.08 mm height but -1.37 mm deck height. This would make a 2138cc motor

 

Z24 piston

Open L head............ 8.02

Closed L head.......... 8.4.... the 1.37mm deck adds 8.5cc to the combustion chamber volume coupled with the Z24's piston dish which is designed for 8.3 compression on a motor that is 62cc larger really drops the CR.

 

KA24E piston

Open L head............ 9.35

Closed L head.......... 9.955 ....the KA piston is almost a flattop so this helps the CR

 

The thing here is that the 'L20B' can have a longer rod. Longer rods are 'rev happy' motors and coupled with the fully counter weighted crank and extra displacement and compression......

 

[EricJB]

I would agree that a KA24de would be easier to swap with better results. I just like messing with the old stuff.

[72240z]

Ya you guys like running the numbers too. Nothing wrong with that. It was just my impression after reading the thread lol, slow rainy day here...

[blackmarkit]

The z22 idea would work but the idea was to get a fully counterweighted crank. Unless I'm wrong the z22 is half counterweighted.

[EricJB]

There is a method to destroking a motor. Look at the 69 camaro Z28 with the DZ302. It was a 327 with a 283 crank, healthy valvetrain, and a dual 4bbl crossram intake. Not much for torque, but they revved like crazy.

 

Black, you are correct the Z22 crank is partialy counterweighted.

[blackmarkit]

Also could use some sbc rods. 2.00 journal diameter. 5.85" legth and $80 each would work good for the 227.45 deck height and yield a 8.92:1 compression with the ka24de head. My goal is I make a fully forged fully counterweighted dual cam.

 

[datzenmike]

My L20B and Z22 cranks

 

[blackmarkit]

So does everyone agree that the 227.45 deck height is more manageable and easier to find rod and piston options. Also would be a lower more steerable rod angle. Around 1.7

[blackmarkit]

Also how safe is it to bore the l20b to 89mm and how common is it for the z series to crank at the coolant port?

[datzenmike]

89mm L20B bore is 2mm off all the way round the cylinder or 0.080". There is the real risk of running out of meat.

[ggzilla]

Rod/stroke ratio would be more efficient and if the racing class only allows 2.2 liters it could be a winner. It will have a bit less HP than the less-efficient 2.4, but would be fun to do.

[flatcat19]

but would be fun to do.

 

Agreed.

So what's the official build. Mike?

[blackmarkit]

According to the math

CFM x .069 = lbs/min of mass flow

And it takes 1 lb mass air per minute to make 10 hp. So the 130 ci (2140 cc) destroked engine will flow 273 cfm at 85% volumetric effienciency. So 273 x .069 = 18.837

18.837 x 10 = 188.37 hp

All math was done at a safer 8500rpms

[blackmarkit]

The full formula is

Cubic inch x .5 x max rpm / 1728 x VE x .069 =

Lbs/min of mass flow

 

Lbs/min x 10 = hp

 

Not exact but very close to factory specs.

[datzenmike]

For a dedicated race motor 8.5K is possible with forged rods and such. Also the rod mods to fit the Nissan pin and crank bearings. won't run well below the red line of a street motor.

[blackmarkit]

Ka stock

146.45 x .5 x 6500 / 1728 x .85 x .069 = 16.15

16.15 x 10 = 161.5 hp

(Factory rated at 155 hp)

 

Destroked ka21.4

130.59 x .5 x 8500 / 1728 x .85 x .069 = 18.83

18.83 x 10 = 188.3 hp

[blackmarkit]

Datzenmike could you please explain why this motor won't run well under redline. Im hear to learn. Rod ratio on the 227.45 deck would be 1.72

[ggzilla]

So you are gaining more HP by revving the KA-22 higher. Why not just rev the KA24 higher and make even more HP? All you need to change is the rods. Stronger forged KA rods will let the KA24 rev to 8500 RPM, won't they? If so, no need to change the rod/stroke ratio to gain a slight efficiency but loose 160 cc. Racers do this to fit into class rules where they cannot run a larger engine. Or if dollars are no object they destroke and run large overbore to bring the CCs back up.

[blackmarkit]

No the ka24 crank is half counterweighted and will start having halmonic issues at 7200rpm.

[ggzilla]

Ah very good. 2.2 liter sounds like the way to go.

[blackmarkit]

I might have already stated but this is the same stroke a a sr20 with a bigger bore and higher flowing head. I don't see how it could go wrong.

[datzenmike]

Datzenmike could you please explain why this motor won't run well under redline. Im hear to learn. Rod ratio on the 227.45 deck would be 1.72

 

What I said....

 

For a dedicated race motor 8.5K is possible with forged rods and such. Also the rod mods to fit the Nissan pin and crank bearings. won't run well below the red line of a street motor.

 

What I mean is...

 

Power is produced by the head. The more air you can run through it the more power you make. To get more air to flow you have to make compromises.

 

Two L20Bs.

One with minor mods to peak power at 6K. I think the red line is 6.5K? Although an L20B will rev way beyond this, this is a safe limit for an unmodified motor, stock rods, small oil pump, Intended for running 200K miles in it's life.

The other L20B, full race and intended to be rebuilt every 10th race, with forged rods and pistons, oil pump and cooler, open header, multi-carb and intake, insane overlap cam 310 range or higher, oversize Titanium valves with 0.520" lift. The head is ported out to 1.5". Makes it's power 6.5K to 8.5K

 

The first will be drivable (docile) on the street to 6K. Start easy and reliably, idle well and run smoothly around town and on the highway.

The other will have terrible manifold vacuum from the long duration and overlap cam and will only idle above 1,500. Cylinder filling at low/mid range speeds will be poor because of this and the large ports and slow air speeds. But when it gets going, the head will flow huge amounts of air and make lots of power.

 

You can have one, or the other, but you can't have both. That which builds power at 8,500 RPMs is not good at half that, hell it isn't good at 2/3s that.

[ggzilla]

You can have one, or the other, but you can't have both -- unless it is a VVL head.

[EricJB]

 

 

 

The other L20B, full race and intended to be rebuilt every 10th race, with forged rods and pistons, oil pump and cooler, open header, multi-carb and intake, insane overlap cam 310 range or higher, oversize Titanium valves with 0.520" lift. The head is ported out to 1.5". Makes it's power 6.5K to 8.5K

 

 

 

I'll take this one.

[blackmarkit]

But as a turbo motor I am not dependant on huge duration to make power. The turbo will continue filling the engine as long as it can keep up. I believe with around 260-270 duration I could easily hit 8500 rpms with a turbo and pull all the way. That is one of the big reasons I want to build this engine is because I can run a bigger turbo spool later and still have it pull for 4500 rpms.