Question about Honda 2.0 vs Mazda 2.0

[Rogue]

The Honda has a K20Z3 2.0L that redlines at 8000 rpm, whereas the Mazda FS-DE 2.0L redlines at 6500 rpm. I guess I'm asking, what can be done to ours to make it rev like theirs?

 

[twilightprotege]

a better rod ratio and a far better flowing head with bigger cams

2L <> 2L

 

[Rogue]

what do you mean by rod ratio? is that the length of the rod in relation to the entire length piston (head and rod)? Could we get our head to flow as well? If we knew the specs of their cams, could we copy them over? Which would be better, the cam specs before or after VTEC "kicks in"?

 

[Gaboost]

Easy, swap the k-series into your car.

 

[twilightprotege]

length of the rd vs length of the stroke.

we could never get the head to flow the same because we are limited to the size of valves we run. they use bigger pistons and therefor have more room for valves, but we could get close.

cams - after vtec if you want the power

 

[Rogue]

by bigger pistons do you mean the bore?

 

[twilightprotege]

yep

 

[Rogue]

so it's a bigger bore, shorter stroke. That's how they rev so high?

 

[AznXstazy]

Easy, swap the k-series into your car.

ya dude, probaly easier this way =)

 

[JCell]

even easier, just buy the whole honda

 

[Dimitrios]

Redundant commentary here, but you want to reduce the reciprocating mass and one way to do it is to tweak the rod/bore ratio.

It's why a 327 is my fav. small block Chevy - same bore as a 350, just shorter stroke, thus winds up faster.

 

[anarchistchiken]

so it's a bigger bore, shorter stroke. That's how they rev so high?

Well the piston/rod/crank assembly can survive those revs because of the short stroke, but even if we had the same specs on the rotating assembly, our head would never survive those revs without serious modifications, meaing larger valves, better springs, and some serious machining to boost the flow.

It would honestly be a lot easier and cheaper to swap in a K20, especialy considering that you swap it in, have that performance, and then start modding, instead of investing ungodly amounts of money in modifications just to reach that level.

 

[twilightprotege]

want the best piston mazda engine? get an fe3 2L of yumyum

 

[Dimitrios]

want the best piston mazda engine? get an fe3 2L of yumyum

Off to the junkyard for you!!
http://members.aol.com/solomiata/FE3.html

 

[TampaSport20]

SOHC ? Sacrilige !

nope

DOHC...WAY better than a FS-DE

 

[peepsalot]

With a shorter stroke, the max piston speed and therefore the centrifugal force on the rods, etc. is much less. Also, our heads just aren't designed for high revs, while honda's are from the factory, I don't think our springs hold up well, the valves don't flow paricularly great comparatively, and our cams are optimised to make power at a lower rpm. You could get cams made for higher rpm power, but without teh VTEC, you will be losing more low end torque.

 

[Gen1GT]

The K20A is literally the best 4 cylinder engine ever made. It's not really fair to compare it to a weak engine like the FS-DE. The K20 is square, with 86mm bore and stroke. But more importantly, it has 139mm rods, giving it a 1.62 rod ratio. Rod ratio is the key factor here, with stroke being secondary. And Dimitrios, bore actually plays a role in the upper limits of power. Larger bore equals heavy piston, which increases accelerative and decelerative forces. Mean piston speed and max piston speed don't matter as much as max g-forces. You can have a high max piston speed through mid stroke, but if it slows appropriately toward TDC, the stresses are lessened. If the piston is still travelling at max piston speed at 30 BTDC, it doesn't have much time to stop and change direction. Small bores and lightweight, forged pistons actually help. An engine with 101mm bore, 76mm stroke and 129mm rods will not rev as well as an engine with 81mm bore, 87mm stroke and 139mm rods(bonus points if you can figure out which two engines those specs are from)

You could easily build the bottom end of an FS to spin to 9000RPM, but you'll need a tonne of work to get it to actually make power up there, and it won't be anything resembling streetable. We don't have variable valve timing and lift, so the cams needed to make power at 8000RPM won't allow the engine to idle slower than 1200RPM. The K20A cylinder head is second to none also, and it's fundamental design is so much better than the FS's. This is an engine that makes 210whp with bolt-ons. 300whp in a serious, but streetable build with IRTB's.

I say just work with what you're given. The FS(or the BP for that matter) were never designed to be efficient NA monsters. Don't worry about RPM for RPM sake. Do a build that best suites your needs. If you need a race engine that screams to 9000RPM, then all the power to you. But I'm sure you'd be happy with a serious street build making 170whp at 7000RPM with a good powerband and reliability.

 

[twilightprotege]

the engine i'm going to purchase for my drag car (recently bought a hos to build up) has a rod ratio of 1.706 rod ratio

85mm bore, 88mm stroke

 

[Rogue]

this is why i love the NA section. All facts, no BS.

I appreciate all the information given here. I was just curious as to why the KA20 was so good compared to the FS-DE. I do agree with twilight's comment about the FE-3. I've looked into that, and have already considered dropping that in the Protege5. Not sure at which end and in what direction, though.

 

[Gen1GT]

If I already didn't have a spare BP sitting on my engine stand, I'd get an FE3 myself...