LEADfoot

ok i searched the forum but can't find an ansewr to this

is the problem with reving the fs-de
a) the stroke of the crank
b) or is it the rod length
c) the "small" bore
d) or...what?

i'm confused with this because i'm finding other "long rod" engines that
seem, at-a-glance, to make power higher into the rev-range
at least breathing over 7k
the fs seems to always die at around 5.7k or so
and is done spinning by 6.5k

am i realy missing something here
i know heads/manifolds have a part in this too

but would boring-out the engine help this
or is that not going to effect what i'm seeing in this

mattsstang87

Weak rods. All that rod ratio stuff is mostly myth. No manufacturer makes an engine with a rod ratio that is truly on the terrible side. The FS-DE is close, but not there. But when you combine the high piston speeds (rod ratio) with a serioulsy weak rod, then there is trouble.

Roddimus Prime

yeah. boring has nothing to do with anything.

You just have to learn to live with the fact that we dont own race cars with race engines. They aren't designed to do anything but cruise around town and get somewhat decent milage.

To fix the drop off at 5700rpms. I'd suggest the following:

Protegegarages single runner intake manifold
j-spec intake and exhaust cams
aftermarket header
mp3 ecu.

You'll have no more problems.

macdaddyslomo

correct.

mattsstang87

I still need the exhaust cam. Still on the fence about the intake. Though mine pulls pretty good to the tach redline.

LEADfoot

well thats the conclusion i had come too
but i've only worked on small detroit stuff
and even that was just mild camming and a slight overbore...so not the same thing entirely

i don't realy need more revs...in all truth
but knowing i could pull a little more out of the top-end...or even push the
top-end up the revrange and extend the redline just makes me feel good

thanks for the straight answer...not an "anything is do-able with enough money" answer

so to what extent do vavles and porting help it flow higher up?

Roddimus Prime

I think there are a few restrictions to our engines. You guys can back me up if you agree..

1. decade old head design (flows HORRIBLY in comparison to a honda 2.0L head)

2. stroked engine block keeps revs down to give up alittle extra torque down low (daily driver compromise)

3. ECU....intentionally intrusive and un-tuneable. Mazda does this to avoid warranty work and to meet emissions. Performance is nowhere on their priority list.
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If you wanted to make GREAT na power and money was no option I'd find a machine shop that can build you an all aluminum head that is CAD designed to flow MASSIVE amounts of air. Then get custom cams made to keep the main powerband above 5Krpms. Maybe 5-9K rpms. Then de-stroke the engine down to 1.7-1.8L and have everything lightened, balanced, forged and knife-edged. This will allow you to rev more, cleaner and faster.

Horsepower is a function of torque over time (rpms). The more rpms you can pull the more hp you can make (at the expense of torque). Just look at a Diesel and a Honda...

LEADfoot

yeah right, diesel vs honda...
i understand the under the curve aspect of our motor when
my friend (b16a) and i (fs-de) dynoed the same day back to back
on the same dynojet w/the same tech

he was dead until 5.7k+ then climbed straight to 116hp@7500rpm
never making more than 80ft/lbs or so

where the protege had almost all 113ft/lbs across the whole band
and peaking 100hp flat around 5.5k...you all know the rest

ah yes money no object...if that was the case i'ld be hard pressed to keep
exploring this engine if i start thinking i need disgusting amounts of power in this car
i'll be tempted to start a new project

135-145whp is the max for me...(maye that is too much to look for)

Roddimus Prime

stick with a small (35hp) shot of dry nitrous. ZEX will take care of you for less than $500.

LEADfoot

for a road car in the canyons though?
i'm not much on stoplight drags

Roddimus Prime

power is power. Only difference is a 10lb bvottle won't last long. Maybe if you were serious about it you could buy a "multi-bottle" system and only using a 35hp shot it should last a good while.

For instance. A typical ZEX dry kit is about $475shipped. And extra 10lb bottle and t-fitting kit is another $200 or so. A 10lb bottle of nitrous (here near me) is about $32 a fill. So you could save yourself a lot of money over going with a turbo kit...BUT, the more refills you buy the more you'll spend so in the long haul you may spend more....well...no, you wont.

$750 (intial parts + 2 bottles filled)
$60 (2 bottles filled)

=

$810 for 4 bottles of nitrous.

now figure a typical Turbo kit is about $3500+ depending on what you want. That leaves $2690 for bottle refills..That means you could get the system and refill it 46 times for about he same price as a turbo kit.

The turbo will make more power but honestly it would take you FOREVER to burn through 92 bottles of nitrous on a 30hp shot.

LEADfoot

oh i see thanks...good line of thought