Let's do some mathematics

[antiSUV]

Some of you might wonder why our cars (w/ F2 and F2Ts) only redline at 6000. Never mind the fact that we don't have much power above 5k, why is the redline so low, specifically?

The standard answer is usually "becuase our motor is all stroked out." But what does that really mean?

Let's do some math, shall we?

Mean Piston Speed = 2 x Stroke x RPM / 60
(mean = average, in case you forgot that)

We'll start with our beloved F2/F2T:

Mean piston speed = 2 x 94mm x 6000 / 60

This gives you a mean piston speed @ redline of 18.8 meters/sec

Now let's check out the FE3

Mean piston speed = 2 x 86mm x 7000 / 60

So the FE3 has a mean piston speed @ redline of 20.1 meters/sec

So you might be thinking to yourself "why is the FE3 allowed a higher mean piston speed than my F2?"

Well, what if our engine was allowed the same piston speed as the FE3? What would the redline be?

You can solve for that by:

20.1m x 60 / 2 / .94m

This equation gives you a theoretical F2 redline of around 6400 rpm. Why wasn't the F2 allowed to redline at 6400 then? It's because of the stroke again. When you increase the crankshaft throw in an engine, the rods must go through more extreme angles as the crank turns. This puts more sideways stress on the piston/pin/crank, and that would be a reason why we don't get that extra 400 rpm. Another reason is that a larger stroke also equals higher peak piston speeds at the top and bottom of the pistons' travel; you can't go by the mean speed alone.

These numbers are for all else being equal. I'm not taking into account the difference in rod length between the F2 and FE3. I couldn't find that info anyhere.

Any of you FE3 dudes have some corrections or addition info?

[deadmeat]

You make my head hurt.

meaty no like numbers.

-meaty

[hurddawg]

I'm almost sure that my 89 5-spd n/a had a fuel cut at 6400. At least close to it....i hit it once in 2nd gear. I know the cut (it was a hard cut) was past 6k. My 92 auto n/a has a soft-cut (ignition timing retard) at 6K though.

[GT Riq]

The most important reason why our engines can rev higher is not really because of its all stoked out 2200ccs, the reason why we cant rev up to 7000rpms is because our cylinder head!!
I bet that just by putting a higher duration and lift cam, doing a nice porting and polishing to the head and intake manifold, and maybe lifting the compression from 7.8 to 8.5 we would be able to run high rpms. Of course we would have to eliminate the 6300rpm cut off, but I bet that by doing this (and changing the turbo) we could run up to 6500rpms and not loose power.
The new turbo will be needed to provide more air at higher rpms, and the higher compression wouldnt really affect us that much, If you consider those hondas running 10psi with compressions of up to 10.0:1, we could easily run 14psi with an 8.5 compression.
And some people think that high cams dont work in turbo engines, but thats totally wrong. The reason why this high cams usually dont work is because they are made for naturally aspirated engines and have big overlaping, say lobe centers at 106 or 108 degrees, what we would need for the FE2T would be a high duration and lift cam, but with lobe centers at 114 degrees, so then we would loose boost "power" in the overlap.

So I believe that with all this done, Our FE2 and FE2T could hold its own in the high rpms!! Well 6500-7000rpms are not that high considering those Vtec engines, but hey, 1500rpms extra than what we are used to is alot!!

[Moltar]

i wonder if a higher reving engine would be of any benifet considering that most of us dont or shouldnt be doing any high speed driving
and also wouldnt you need stiffer valve springs to prevent valve float. i think that i read one time that jay b used stiffer springs from a toyota because they were the exact same height

[antiSUV]

Moltar, a higher redline allows you to hang on to each gear longer (if you have power up there), thus increaseing acceleration...it's not just for top speed...
Also HP is a function of rpm...Hondas make HP with very little torque because they can rev high.

I wasn't actually suggesting that the F2 should have a higher redline. I was just doing a thought exercise.

[MazdaMiester]

damn james...first off im totally surprised i actually understand what your saying(somewhat) and 2nd off....why dont we tear down that bad f2t and find out rod length....if anything we can clean it up and turn it around for 50 bucks...i took a burned up f2 cylinder head...just the head, no valves, cams, nothing...and they gave me 23$ for it....at an aluminum recycling place...i have another question james...if the head is bad, that does not neccessarily mean the cams are....i wouldnt mind having those cams....did some talking to a machine shop manager this past weekend about building a front strut tower bar, he could probably do a cam grind for very cheap. he is going to Build me a "prototype" front strut tower bar for mine....no idea if it'll work, but its based on the corksport, with a few changest....its not as adjustable but its adjustable using an allen head, and the bar is shorter and the brackets stick inside the car further...crap i jammed a thread with unrelated info...oh well :P

Eric

P.S. 2 88-89 GT wheels, Grey front seat parts, GT radio, wheel chucks, and alot more for ya waiting for your next visit

[antiSUV]

The head's yours the next time you come down...cams have scoring on them so they definitely need to be re-ground. If I ever rebuild that motor (now that it's well-seasoned), it will get a Kia head anyways.

[antiSUV]

FE3 rods are 152mm
F2T rods are 158.5mm

This gives the FE3 a rod to stroke ratio of 152/86 = 1:77
And the F2/F2T is 158.5/94 = 1:69

Both of these numbers are good, but the FE3 is closer to the optimum value of 1:75.
Still both are way better than the Honda B16a, which is 1:56 because that motor needed to be short to fit under the hood, so they had to make the rods kinda short to reduce overall engine height.