So i havent seen many people mention this...

[chulooz]

Originally Posted by Mr.Jay

Yes but that a tuned extremely low volume track car

The Ford Duratec 2.0 made 143Hp in regular form.

Your point is moot. There is no comparing a tuned engine to a stock engine. If you want to make that agurement there are many tuned s2k making 300+HP NA

Not so moot in my book. I can go out and buy a Caterham Superlite R500 and get those numbers. That is the engines regular(a relative term) form in that model; it is the stock engine for that vehicle. Whether its tuned by the company or not doesn't flex the point that it's more powerful than the Honda. You buy an unmodified S2k with competitive numbers.

[tranzformer]

Originally Posted by EJ20

hell if toyota make the new boxer cr into 12:1 the I guess 220~240 on 2.0L na engine is so easy! but since this is a mass production engine/car I guess we will have a detuned version for better fuel econ?

On another note, Mazda is coming out with their new 2.0l Skyactive engines and will run a cr of 14:1 with 30mpg city/40mpg highway. I think they will be rated at around 163hp/155tq. Just an example to point out you can have high cr and still great fuel economy.

[serialk11r]

Sounds like Atkinson cycle or something similar if it's to run on 87?
High CR = MORE efficient, it's just the cars you see with high CR tend to be performance cars fitted with fat engines/short gearing.

Sorry if this is a noobish question, but when people are really wringing out their engines do they really get to 6th gear? Or 5th gear for that matter? What kinds of speeds do you hit on a track? Is there a good reason why companies want to have such short gearing on cars like the s2k (highway cruise at like 4000rpm?)?

[ichitaka05]

Originally Posted by serialk11r

Sorry if this is a noobish question, but when people are really wringing out their engines do they really get to 6th gear? Or 5th gear for that matter? What kinds of speeds do you hit on a track? Is there a good reason why companies want to have such short gearing on cars like the s2k (highway cruise at like 4000rpm?)?

There's a lot of reason, but simply say "Cuz they said so"

Seriously, I think the main reason is there won't have rpm dead zone

[Mr.Jay]

Originally Posted by chulooz

Not so moot in my book. I can go out and buy a Caterham Superlite R500 and get those numbers. That is the engines regular(a relative term) form in that model; it is the stock engine for that vehicle. Whether its tuned by the company or not doesn't flex the point that it's more powerful than the Honda. You buy an unmodified S2k with competitive numbers.

That car is so low production its crazy there only what 2 delaers in NA?

I don't know the cost of one in USD but considering its 61+ Euro I'll take the S2k and mod it.

If I were to include low volume track cars then I would of said Ariel Atom V8 since its a 3.0 V8 that makes 500hp


I'm just going to agree to disagree cause I don't consider these types of cars should count

[Exage]

Originally Posted by cyde01

couldn't they just add longer rods than changing the whole borexstroke ratio? the F22C is also undersquare, but it feels great revving to 8000. 87x90.7 borexstroke with a 1.65 rod/stroke ratio.

we already know the FT86 is gonna have D-4S, so since it's gonna have a different head already the combustion chamber design will surely be different as well. i really hope they do a good job with this motor!

What happens to your piston to head clearance with a longer rod? It depends on the amount of change in connecting rod length without changing the stroke, think about the crank at Top Dead Center and now increase the height of the piston. You run the risk of unfavourable (very high) compression ratios or possible piston to valve or even head collisions. Like I stated if they're going to change the rod to stroke ratio (longer connecting rods) which was 1.44:1 to +1.50:1 I speculate that the FB would need a de-stroke from 90mm to compensate for the longer connecting rod. The FB boxer engine can't really become that much wider after all (increase block deck height), unless changes in reducing the height of the cylinder head are made...

[ollin]

Originally Posted by Exage

What happens to your piston to head clearance with a longer rod? It depends on the amount of change in connecting rod length without changing the stroke, think about the crank at Top Dead Center and now increase the height of the piston. You run the risk of unfavourable (very high) compression ratios or possible piston to valve or even head collisions. Like I stated if they're going to change the rod to stroke ratio (longer connecting rods) which was 1.44:1 to +1.50:1 I speculate that the FB would need a de-stroke from 90mm to compensate for the longer connecting rod. The FB boxer engine can't really become that much wider after all (increase block deck height), unless changes in reducing the height of the cylinder head are made...

there will be no valve clearance and we need to pray everyday that nothing happens to the timing like on a Z or any other interference engine.

[cyde01]

Originally Posted by Exage

You run the risk of unfavourable (very high) compression ratios or possible piston to valve or even head collisions.

it just sounds a lot easier to change the rod length and change the cylinder heads and pistons than changing the entire borexstroke ratio. also, do those crazy angled rods have anything to do with the short rod length? i wonder if having the rods at an angle may compensate for the low rod/stroke ratio.

[NESW20]

Originally Posted by Mr.Jay

I have driven a CSX type R as well as the new civic Si and this engine does nothing for me tho that could be cause I've driven a K20A RSX type S and that is a much much much better engine.

My bad I shouldnt say its the blacksheep of K engines but I deff think its the worst out of the high preformance Ks (K20A, K20Z1, K20Z4 etc) hell even the older K20A2 I thought had a better feel to it than the K20Z3. Just my personally opinion however tho the K20A is easily the best in my mind.

can you explain what about the A is so much better than the Z3? all you've said is that the A is better, and haven't given much to support it. i'm not looking to start a fight, but i'm curious why you like the A that much more than the Z3. :happy0180:

according to wikipedia, it looks like the main difference is the A has Vtec on intake and exhaust cams, whereas the Z3 only has vtec on the intake side. i'm not as familiar with the A, so if there's something more substantial than that, please tell me.

[Midship Runabout]

Longer rods equal higher piston speeds thus lowering redline. Do not want

[NESW20]

Originally Posted by Midship Runabout

Longer rods equal higher piston speeds thus lowering redline. Do not want

you mean longer stroke. longer rods actually reduce piston speeds, if i'm not mistaken.

[Midship Runabout]

^your right.

[Exage]

Originally Posted by cyde01

it just sounds a lot easier to change the rod length and change the cylinder heads and pistons than changing the entire borexstroke ratio. also, do those crazy angled rods have anything to do with the short rod length? i wonder if having the rods at an angle may compensate for the low rod/stroke ratio.

Although it "sounds easier"; clearance is a much bigger issue that way. If they were "just" going to toss in longer rods then they would have to make the block deck higher (the length between the center of the crankshaft to the top of the block where the head meets) and shorten the cylinder head height. The FB and specifically boxer engines in general don't have a lot of room to play around with side to side.

Extreme example: The FB20 stroke is 90mm, it's current connecting rod length is stated at 129.3mm 129.3mm/90mm is 1.43666 rod to stroke ratio. If you wanted 1.55 rod to stroke ratio without altering the crankshaft you would need 90mmX1.55 = 139.5mm connecting rod.

Compression ratio (CR) of stock FB20 is 10.5:1 and 90mm of stroke results in a ~9.47mm clearance between piston at TDC and cylinder head 10.5:1 CR=(9.47mm+90mm)/9.47mm. Can you already see the problem? Any addition to the rod length decreases the clearance between the piston at TDC and head. In this case I wanted to increase my rod length to 10.2mm when I only have 9.47mm till it nails the cylinder head, less till it meets a valve. And say I don't have the space to increase the block deck height and or shrink my cylinder head by more than 17.7mm to acquire a CR below 13:1. Higher piston wrist pin placement or less tall piston will put some compromise on the pistons ring lands and piston structural integrity so it's not a good solution either.

Fact is you could get a 12:1 CR on a stock FB20. You would need 8.18mm clearance which means you could safely add a whopping 1.29mm to the 129.3mm rod making the rod to stroke 1.451, that engine is still going to wear like nothing else at high rpm and won't like it up there...

I believe the angled connecting rod end caps are better on the set screws in terms of tensional loading when transmitting force to the crankshaft. I can't remember all the reasons.

[Dimman]

90mm stroke also has way more stress at higher revs. Has to change direction faster (I think...). This is pretty close to Toyota's 7M which had 91mm stroke. Not known as a revver.