Honda / Acura K20a K24a Engine Forum banner

1 - 7 of 7 Posts

·
Registered
Mazda MX5 mk1 with a NA K motor (eventually)
Joined
·
1 Posts
Discussion Starter #1
hello,

I have a plan to put a K motor into a mk1 miata. Some targets I have for this engine is to make 300whp on ITBs and have it rev to the moon, up around 10-11k.

I bought a dirt cheap hurt k20a2 that i have been pulling apart to get a feel for the platform and i have been learning a lot.

I think I want to do a Frankenstein using a k24 block, k20 crank and a k20a2 head and a sprinkle of goodies to make the power.My hope is the short stroke of a k20 crank with the tall deck height of the k24 block will let me get a low(ish) enough piston speed and also let me use a much longer rod to get a higher rod ratio.

is there any compatibility issues with my plan? does the k20 crank fit in the bottom end of a k24? also, are there any off the shelf rods and pistons that will fit this idea well (that are pretty light weight but not alloy)

another route could be a destroker crank. if anyone makes a 1.8L crank? that would let me move down a class :)
 

·
Arouse the DAMPFHAMMER!
Joined
·
6,054 Posts
...targets I have for this engine is to make 300whp on ITBs and have it rev to the moon, up around 10-11k....using a k24 block, k20 crank and a k20a2 head and a sprinkle of goodies to make the power.My hope is the short stroke of a k20 crank with the tall deck height of the k24 block will let me get a low(ish) enough piston speed and also let me use a much longer rod to get a higher rod ratio.
Welcome to K20a.org Henry Collingwood!

Now I got you in my edited version of this post. I was going to build a 86x68 K16 engine for 1600 ccm class, parts cost of 18,000 Euro without work and alternation of load parts. This engine was spec'ed to be safe up to 12,000 rpm with 270+ [email protected],500 rpm. Likely we change to a cheaper platform not to exceed 25,000 Euro. Now you have a number what is necessary for around 170 hp/Liter. Your aim is around the same hp/Liter area, just with an 86x86 engine, just the crank, pistons and conrods are some of the shelf aftermarket parts, saving you some 5000 Euro.

With the 86 mm stroke you run in some series dynamic issues: crank assembly forces get really high. The taller block height isn't for all of them an advantage. It depends on the weights of piston and conrod assemblies. It isn't just a transfer of rod-stroke-ratio of high speed engine like an Formula 1 engine into a K-series, while the Formula 1 Pankl rod was around 155 mm at a rod stroke ratio of more then 2.5:1 the K24-block rod would be around 158-163 mm long (piston height!), but the forces at 11,000 rpm at the rod bolts are already higher as on that Formula 1 engine at 16,000 rpm. If you look at that Pankl rod an Mahle Piston you see a lot of design work to make it more stable at around 245 g piston assembly and a roughly 390 g conrod. ONE cylinder assembly cost more than your engine will cost. You can fight weight down, but you can't increase reliability in that manner F1 did. Finally you need to put big effort in a 50 h lasting engine: alu or smart designed steel rods, low piston height pistons (two ring or three ring system) and then the head. What makes it inhaul air for 345 hp at flywheel makes the port inefficient down low, what is needed on a hill climber, so the compromise where the engine performs cost investment into customized exhaust and intake as well as valves and ports.

It would be recommendable to go to an 90x78.5 (= custom crankshaft) or 87x84 (F20C crankshaft), it would reduce the dynamic load in the crank assembly and give more room to the head design to achieve the flow numbers and combustion velocity which is needed. The 231 mm block height of the K24 would provide some advantages, but not in all engine setup cases on that project.

How many race hours do you need it before overhaul?
 

·
Registered
Joined
·
95 Posts
Welcome to K20a.org Henry Collingwood!

Now I got you in my edited version of this post. I was going to build a 86x68 K16 engine for 1600 ccm class, parts cost of 18,000 Euro without work and alternation of load parts. This engine was spec'ed to be safe up to 12,000 rpm with 270+ [email protected],500 rpm. Likely we change to a cheaper platform not to exceed 25,000 Euro. Now you have a number what is necessary for around 170 hp/Liter. Your aim is around the same hp/Liter area, just with an 86x86 engine, just the crank, pistons and conrods are some of the shelf aftermarket parts, saving you some 5000 Euro.

With the 86 mm stroke you run in some series dynamic issues: crank assembly forces get really high. The taller block height isn't for all of them an advantage. It depends on the weights of piston and conrod assemblies. It isn't just a transfer of rod-stroke-ratio of high speed engine like an Formula 1 engine into a K-series, while the Formula 1 Pankl rod was around 155 mm at a rod stroke ratio of more then 2.5:1 the K24-block rod would be around 158-163 mm long (piston height!), but the forces at 11,000 rpm at the rod bolts are already higher as on that Formula 1 engine at 16,000 rpm. If you look at that Pankl rod an Mahle Piston you see a lot of design work to make it more stable at around 245 g piston assembly and a roughly 390 g conrod. ONE cylinder assembly cost more than your engine will cost. You can fight weight down, but you can't increase reliability in that manner F1 did. Finally you need to put big effort in a 50 h lasting engine: alu or smart designed steel rods, low piston height pistons (two ring or three ring system) and then the head. What makes it inhaul air for 345 hp at flywheel makes the port inefficient down low, what is needed on a hill climber, so the compromise where the engine performs cost investment into customized exhaust and intake as well as valves and ports.

It would be recommendable to go to an 90x78.5 (= custom crankshaft) or 87x84 (F20C crankshaft), it would reduce the dynamic load in the crank assembly and give more room to the head design to achieve the flow numbers and combustion velocity which is needed. The 231 mm block height of the K24 would provide some advantages, but not in all engine setup cases on that project.

How many race hours do you need it before overhaul?
Does the s2000 crank fit in either the k20 or k24? I remember reading something about the head gaskets matching between the engines which would suggest you could put an S2k head on a k24 block ? I believe it was on an old hybrid racing article
 

·
Registered
Joined
·
95 Posts
hello,

I have a plan to put a K motor into a mk1 miata. Some targets I have for this engine is to make 300whp on ITBs and have it rev to the moon, up around 10-11k.

I bought a dirt cheap hurt k20a2 that i have been pulling apart to get a feel for the platform and i have been learning a lot.

I think I want to do a Frankenstein using a k24 block, k20 crank and a k20a2 head and a sprinkle of goodies to make the power.My hope is the short stroke of a k20 crank with the tall deck height of the k24 block will let me get a low(ish) enough piston speed and also let me use a much longer rod to get a higher rod ratio.

is there any compatibility issues with my plan? does the k20 crank fit in the bottom end of a k24? also, are there any off the shelf rods and pistons that will fit this idea well (that are pretty light weight but not alloy)

another route could be a destroker crank. if anyone makes a 1.8L crank? that would let me move down a class :)
4piston makes stroker kits for the k20/24 if you contacted them they May be able to make you a custom
Length combo but I would expect it to be expensive
 

·
Arouse the DAMPFHAMMER!
Joined
·
6,054 Posts
Does the s2000 crank fit in either the k20 or k24? I remember reading something about the head gaskets matching between the engines which would suggest you could put an S2k head on a k24 block ? I believe it was on an old hybrid racing article
Yes, it does. It is the 87x84 (F20C crank) engine I recommended above. There is a machine work to do on the shaft outlet to get a fit into the shaft machined. Beside that it is a direct fit. This would be a nice 2 Liter engine, which is maybe the cheapest beside the 86x86 1998 ccm configuration. All other stuff is much more expensive in the 2 Liter area. The cheapest and most powerful is, if class allows, the 90x99 one, then the 89x99 (more reliable, less powerful).

Do you have a further specification to get this condensed more down to reality Henry Collingwood?
 

·
Registered
Joined
·
81 Posts
375hp at the flywheel of a 2.0L motor is a tall order. Get out your checkbook!

 
1 - 7 of 7 Posts
Top