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Old 04-12-2006, 02:20 PM   #1
Token-Negro
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Question Broad torque Curve?

I'm starting to piece together a 2.5 for my WRX and im looking to build a motor that has a very wide torque curve. I dont need anything more then 2.5 so are there head combo's that lend themselfs to be more torque pron then others? I plan on going with a FP Green Turbo and trying to get as close as i can to 400whp on pump gas & 50/50 meth injection.
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Old 04-13-2006, 11:57 AM   #2
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nothing huh?
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Old 04-13-2006, 12:35 PM   #3
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broad torque curve. Appropriate cams and headwork is what you need.
ex. on my 2.0L im holding a flat torque line from 4000rpms(right after peak boost) all the way to 6400+ rpms.

So if I had a 2.5L im sure I could start my flat torque line a few hundred rpms sooner.
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Old 04-13-2006, 12:44 PM   #4
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Other than suggest you build a BBC , I'd talk to the rally guys. They know what they are doing in the flat torque curve dept.
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Old 04-13-2006, 12:52 PM   #5
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I was hoping someone had a combination of heads and cams that helped achive this.
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Old 04-13-2006, 01:48 PM   #6
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Quote:
Originally Posted by Token-Negro
I was hoping someone had a combination of heads and cams that helped achive this.

Sure, I understand, but remember:

Nothing makes torque like 1) Boost and 2) Compression.

If it were my project, I'd find the best flowing heads (.200-.400"), cams that made lots of midrange cylinder pressure, run 9:1, and boost the bejesus out of it. Run good fuel, too

S.
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Old 04-13-2006, 02:18 PM   #7
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Quote:
Originally Posted by n2xlr8n
...and boost the bejesus out of it...
Heh, heh. That, and use a turbo that can hold as much boost to redline as possible. If it tails off (many will), so does the torque.
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Old 04-13-2006, 02:28 PM   #8
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I plan on using a Green. Just trying to build a well rounded 2.5.
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Old 04-13-2006, 05:12 PM   #9
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^^I'd think an external wastegate set-up with standalone boost control would do as much for a broad torque curve as just about any head work you might do. Of course, both would be even better.
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Old 04-13-2006, 05:40 PM   #10
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would a 20G turbo not be even better for a broad torque band? From what I have read, they wake up earlier than even the stock STi turbo on the stock ej257.
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Old 04-13-2006, 07:05 PM   #11
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Quote:
Originally Posted by jigga
would a 20G turbo not be even better for a broad torque band?
For a lower torque band, yes, but not necessarily for a broader torque band; the 20G will make a little more sooner, and the FPG will make a little more later. All else being equal, the choice of turbo (imo) is as much a matter of where you want it to make power as it is of how much power you want it to make.
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Old 04-13-2006, 08:30 PM   #12
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I want to take advantage of the 2.5 and use the torque from it but also a turbo/head cam combo that all works well with each other very balanced. I use a Dtec for my boost control. I guess ill try to get some STI heads and go from there.
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Old 04-13-2006, 10:12 PM   #13
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Quote:
Originally Posted by Token-Negro
...I guess ill try to get some STI heads and go from there.
That'd be the "no-brainer" way to do it if you can find some...
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Old 04-13-2006, 10:44 PM   #14
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IMHO....

I have a 2.5L swap, WRX heads with helix 264 cams. the heads were ported and polished a bit, the chambers cc'd out to 51-ish. with STi head gaskets that gave me about 9.1:1 compression.
on a VF22, with 50/50 alky injection, i had 15 lbs of boost at 3K, AND 300 ft/lbs at the same point.
i had 300+ ft/lbs to about 5700, and then it started to taper off. peak tq was 340.

peak boost was about 17.5 lbs on that dyno session, on the road it was 18.5 or so.

after another two weeks of tuning, the car kept getting better and better, i think it was probably running around 360ish ft/lbs or so, and it pulled like a beast in every gear. even fifth.

that is all the data that i am goign to ever get on that setup, i am goign a different route.

i would highly reccomend the helix cams if you're looking for a lot of midrange and a big broad tq curve.

also keep in mind that you're goign to want a small ish turbo, like a VF22, big 16G or maybe and 18G to help you build boost fast.
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Old 04-14-2006, 04:03 AM   #15
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Quote:
Originally Posted by banzai
IMHO....

I have a 2.5L swap, WRX heads with helix 264 cams. the heads were ported and polished a bit, the chambers cc'd out to 51-ish. with STi head gaskets that gave me about 9.1:1 compression.
on a VF22, with 50/50 alky injection, i had 15 lbs of boost at 3K, AND 300 ft/lbs at the same point.
i had 300+ ft/lbs to about 5700, and then it started to taper off. peak tq was 340.

peak boost was about 17.5 lbs on that dyno session, on the road it was 18.5 or so.

after another two weeks of tuning, the car kept getting better and better, i think it was probably running around 360ish ft/lbs or so, and it pulled like a beast in every gear. even fifth.

that is all the data that i am goign to ever get on that setup, i am goign a different route.

i would highly reccomend the helix cams if you're looking for a lot of midrange and a big broad tq curve.

also keep in mind that you're goign to want a small ish turbo, like a VF22, big 16G or maybe and 18G to help you build boost fast.
A turbo will help you ALOT..
8cm2 18G should provide enough airflow for a flat tourqe curve to 6500+ rpm's then slowly start to taper.

STI chamber should measure out to 52cc's, so your wrx heads have about 6cc's worth of volume taken out of them.

What "static" compression are your pistons designed for, and for what heads?
.. Or are they stock STI pistons?
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Old 04-14-2006, 01:59 PM   #16
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Quote:
Originally Posted by 02Toyowrx
A turbo will help you ALOT..
8cm2 18G should provide enough airflow for a flat tourqe curve to 6500+ rpm's then slowly start to taper.

STI chamber should measure out to 52cc's, so your wrx heads have about 6cc's worth of volume taken out of them.

What "static" compression are your pistons designed for, and for what heads?
.. Or are they stock STI pistons?
i switched to a 7cm2 TD06-20G in other words a FP20G.

i took a lot of material out of the heads. a LOT. I used to build small block chevys, and i know what a good port job on the heads is worth.

the designed compression of the pistons isn't important.
they are off teh shelf weisco's for an STi, so i am running just on the high side of where they are supposed to run. they are made for STi heads.

given the design of teh pistons, i have no compunctions of running them to 24 pounds of boost, a crap load of timing and beign pretty aggressive compared to stock hyper cast slugs. the ring lands are uber strong, and i think that the pistons will be pretty far down the failure chain. in otehr words, i am not goign to break my psitons before i have catastrophic failure somewhere else int he motor.
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Old 04-13-2006, 10:55 PM   #17
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I've got a broad torque curve considering I'm on a completely stock EJ205 running a TD05H-20G & other boltons.....mine is all in the tune & the components used...



I'm interested to see what the new setup will have for me by the end of the summer...built EJ207, Crucial P&P'd/3 angle valve job'd v8 heads w/ Helix 264 cams & complete valvetrain w/ +1mm Supertech valves...running a TD06H-20G(my 05H, reworked)...
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Old 04-13-2006, 11:42 PM   #18
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that's not a big tq curve.


this is a big tq curve. :P




not trying to be an ass dude. seriously, i am not. those are nice numbers for a 2.0L.
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Old 04-14-2006, 07:11 AM   #19
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Quote:
Originally Posted by banzai
not trying to be an ass dude. seriously, i am not. those are nice numbers for a 2.0L.
thats why I said 'for a 2.0L'...the bigger displacement engines will almost always have broader torque curve than the 2.0L...I was just saying it could be done on a 2.0L also...

nice numbers for a 22 on a 2.5L...
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Old 04-14-2006, 08:36 PM   #20
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just get NOS
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Old 04-17-2006, 08:16 PM   #21
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I had the same thought with reagrds to a broad torque curve.
Here is my approach in progress:
2.5 built block (pistons and bearings)
V8 big port heads w/ Helix valvetrain, oversize valves and V8 cams
GT30R .63 turbo
Ethanol injection of some sort

We'll see what happens. Should be up and running by the end of May beginning of June.
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Old 04-17-2006, 08:28 PM   #22
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Sounds like a great setup, a little expensive but that will be a beast.

Nick
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Old 04-17-2006, 10:07 PM   #23
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Quote:
Originally Posted by Sko
Sounds like a great setup, a little expensive but that will be a beast.

Nick
Yeah...it won't be cheap but I'm hoping it will be reliable.
Andrew @ Gearboxtech will be doing the build and TXS will be doing the tuning.
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Old 04-17-2006, 09:19 PM   #24
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I'm going to be using an EJ5-40T w/ a 2.5 block... Once I get it all tuned with my hydra it should be a pretty flat torque curve, I hope I can get 300whp + >.<

*Offtopic* Anyone have any flow data on those heads? */Offtopic*

Nick
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Old 04-23-2006, 02:53 PM   #25
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this is the best torque curve I've seen and it doesn't even have cams. Peak torque was actually lowered by the tuner. Also this dyno reads very low and was on 100 octane. This is a gt30r .82 that spools faster than greens. Some time was spent on the AVCS map.

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