2.5L with lower revs/more torque, or 2.0L with higher revs?

[Admiral Ballsy]

Originally Posted by ZDan

You're saying this car needs to rev 3000 to 4000rpm higher?

I think he means the 3200-4500 range needs improved.

I agree - if that range was flat rather than diminished, the car would feel a lot faster than it currently does.

[DoctorNick]

I loved my 207 RA spec C engine with its 8750 redline. If they could bring a motor like that, I would take it over any "tuned" 2.5L motor any day of the week. Granted its an apples to oranges type comparison but the smoothness of that 2L was just exotic and intoxicating.

[Adeets]

Originally Posted by diss7

There's a 2 door, lightweight, rear wheel drive, good looking wrx? Kthxbi

There is, and if u googled you would find it, kthxbi!

[StormTrooper]

Originally Posted by Admiral Ballsy

I think he means the 3200-4500 range needs improved.

I agree - if that range was flat rather than diminished, the car would feel a lot faster than it currently does.

Yes,

The car needs more mid range punch... More torque and power from 3-7k

I could care less about 8k or 2k range.

[ZDan]

Originally Posted by StormTrooper

Yes,

The car needs more mid range punch... More torque and power from 3-7k

I could care less about 8k or 2k range.

Ah, the infamous 3200-4600rpm dip...
There is hope for a modded intake and exhaust to at least help out there. Modding the airbox and exhaust on my SV650 motorcycle improved its midrange dip more than I'd expected.

But from 4600-6500, I don't see anything to complain about.

[neurokinetik]

People seem to obsess over the redline of the engine, when all that really matters is having a broad, flat torque plateau. From there, it's just a matter of gearing.

[Suberman]

Originally Posted by Admiral Ballsy

I think he means the 3200-4500 range needs improved.

I agree - if that range was flat rather than diminished, the car would feel a lot faster than it currently does.

But would it actually be faster? There's no free lunch on valve timing with fixed cam profiles. To fatten up that torque dip you'd have to change the torque curve in other ways. It helps if you think of the torque curve as having two peaks rather than one dip. More accurate description.

The gearbox is designed to help you avoid the dip. Run high rpm for performance and low rpm for commuting. Avoid driving the engine through the dip. This is counterintuitive to all of us raised driving engines with a definite torque peak in the mid range. Don't complain, Porsche has been tuning its engines this way for years. Try driving a Cayman/Boxster and you'll find exactly the same torque dip in exactly the same place in the rpm range. That's why the redline needs to be so high. Enjoy that, don't bitch about it.

Interestingly, this torque dip is only really noticeable in flat out acceleration runs from a standstill, something nobody really does driving on the street. For all other driving situations you avoid the torque dip by using one half of the rpm range or the other. Personally I like driving from 4,500 to 7,400 most of the time. Car goes like a stabbed rat if you do that.

FIAT powertrains multi air engines with more or less infinitely variable timing and lift look promising but... are patented to FIAT. It's a clever variation of the hydraulic lifter which was first invented to eliminate the need for valve shim adjustments. Now it can be used to vary the effective cam profile by varying the height of the lifter and the timing of the changes.

The continuously variable valve, both lift and timing, is the holy grail of internal combustion reciprocating engines. BMW Valvetronic and Vanos systems are pretty good. FIAT has one answer but can it be made reliable enough? A Chrysler dealer near you has the answer: Dodge Dart 1.4 multi air. Works best with a turbo: the other holy grail, if you can have two, which would be variable displacement and variable compression ratio which is what supercharging does. (Is that three holy grails? That's too many, I need a different metaphor).

Fully programmable 3D engine management with DI fuel injection took street gas engines as far as they can go without adding full 3D valve control. Supercharging is a cheap way of sidestepping valve train inefficiencies.

Finally, if fuel is cheap there's no substitute for displacement. A boxer engine is so well balanced a 2.5 four needs no balance shafts.

[s2d4]

Originally Posted by ZDan

There is hope for a modded intake.

How do you plan on doing this?

[StormTrooper]

Headers do wonders for the dip...

[Gords_zenith]

9000 rpm NASCAR engine....850hp who says displacement can't also have rpms!

[StormTrooper]

Lol...race engines don't last very long though.

[Dimman]

Originally Posted by ZDan

With stock cams? No way. Headers and lower-restriction exhaust will not give this engine an 8000rpm power peak. Same as with the intake manifold, you can free it up all you want and peak power is going to remain around 7000 until you go to different cam profiles with greater lift and overlap, and possibly port out intake/exhaust runners to support that.

There is NO magic!



You're saying this car needs to rev 3000 to 4000rpm higher? That would be nice but I don't see it happening, not by a long shot! Suffice it to say it would take a LOT more than an intake manifold and a header to get there...

I actually believe this is possible, ZDan. I did some calculations on the positive and negative exhaust-generated pressure waves given some eyeball measured lengths of the stock exhaust manifold primary and secondary lengths. What I came up with was a negative acoustic return at the first torque peak, and a positive return just after power peak. Adjusting the lengths to move those returns around could improve scavenging/flow in both the 'valley' everyone complains about, and/or past power peak.

[brichard0625]

God damn you guys are smart!!! so many knowledgeable people. I have no clue what half the stuff means but its very interesting. I've learned plenty from this forum...but back on topic i would like more low end power because like someone stated that is where 90% of the time people will be at when they drive. I know headers help improve top end but only by so much. So to me more rpms would be useless unless it can make power all the way up. Does anybody think there is more hidden juice left in this engine N/A? or is 200-205hp the most we will probably we see?

[Dimman]

Originally Posted by brichard0625

God damn you guys are smart!!! so many knowledgeable people. I have no clue what half the stuff means but its very interesting. I've learned plenty from this forum...but back on topic i would like more low end power because like someone stated that is where 90% of the time people will be at when they drive. I know headers help improve top end but only by so much. So to me more rpms would be useless unless it can make power all the way up. Does anybody think there is more hidden juice left in this engine N/A? or is 200-205hp the most we will probably we see?

There is more hidden juice. But depends on what you mean by 'NA'. Bolt-ons only? Or getting into cams and port work?

For bolt-ons I'm waiting to see better header results than we have, from there we can start playing with a complimentary intake runner/plenum/ram tube to boost the areas where the header is most efficient or any holes that need filling because of it. There is also a chance for improved exhaust performance after intake and headers, but keeping it muffled will be tough since optimally we want a shortish open dump to atmosphere, but quieting that by simulating atmosphere with a termination box takes a fair bit of space that doesn't look to be available.