Slee256

Hey guys, I'm really happy with the way my Ralliart has been running(I've never had a single problem with it), the only thing I wish could be a little better is the top end power/torque at high rpm's. Right now, my torque starts falling off pretty quickly at around the 4500 rpm mark, and my hp drops off quick after about 5500 rpm's. Here's a link to my dyno graphs:
http://www.facebook.com/photo.php?fb...3527.690762784

The first option that I thought might help would be to replace the stock midpipe with a 3" custom made one(I currently have a 3" rear axle back exhaust running all the way through to the 4" exhaust tips, so that's been done already). The other option would be to replace the stock IC with something larger and more efficient. So, my question is, which one of these two options will give me the most noticable gains at the top end of the power band? And yes, I know that replacing the stock turbo with something bigger would be the best solution, but I really have no interest in doing that at this time. Anyway, thanks in advance for your advice!

SudzRA

iTrader: (2)

I find myself in the same situation as you. From what I understand (still learning the Mitsu since coming over from a turbo'd Honda) the turbo itself approaches the end of it's efficency band in higher rpms and that's why we lose power in the top end. Mods can help with that problem to a degree, but not enough to create a torque curve that doesn't drop off at higher rpms.
As far as the two mods you suggested, a turbo back exhaust upgrade will help with flow, and make the turbo a bit more efficient, while the IC will help keep with keeping the intake mani temps down, especially at higher rpms.
I don't think you'd immediately notice a massive difference one way or the other, but after a tune the exhaust will net you more power (as long as you do something about the cat at the same time).
However, I'd say that the IC would be the best upgrade to do first, while it may not net you more power than the exhaust upgrade, it will bring town temps and reduce your chances of heatsoak, and that's a safer bet for the engine. I'd do the exhaust upgrade second.

DaJackson

iTrader: (4)

Turbos do not have the best of bothe worlds (strong low end and strong top end) Small turbos that have good low end run out of air at the top end. Stong top end turbos have significant lag that keeps them from having good low end.

Twin scroll and twin turbo set ups help with these issues. If you want more top end get a bigger turbo but you will sacrifice some low end. Just find that happy middle for what you want.

zx-319

iTrader: (2)

Intercooler is the first thing you should do. The stock intercooler is way too small. It won't directly impact your high end power. But will allow you to maintain the same level of boost longer and help maintain you engine reliability.

If you want more high end power, try getting the GST Basemap, this will give some extra kick on the whole power band.

If a tune is still not enough for you, you'll need a bigger turbo. Bigger turbo have a higher flow so they can maintain a certain boost pressure at higher RPM. But as mentionned, the time needed to build enough pressure in your exhaust to be able to build some boost will be longer (more lag)...

skazar

Try Bryan's GST Basemap. Dramatically improved top end.

Rough 01

I agree with skazar about the GST Basemap. I found out that my car developed knock at around 5,000pm and basically shut itself down from there to redline with the stock tune. Getting a good tune on it will fix that and now mine pulls hard all the way to 7,000.

Slee256

I guess I shouldn't have assumed that all you guys would read the mods that I've already done in my "signature", so I better elaborate a little more. Not only did I run the GST basemap for a while, but then earlier this year I went into the local dyno-tuning shop near my house and got a custom dyno-tune using the GST basemap as the starting point for the custom tune. After the custom tune, I gained even a little more hp and torque over and above what I already had with the GST map, which is how I ended up achieving my current 261 whp and 274 wtq. I never imagined that you guys would have thought that I was running the factory/stock map, because there's no way anybody is going to put up these kind of numbers without SOME kind of tune.......

Rough 01

I didn't mean to imply what tune you're running but that usually a tune helps. Personally, I went the other way with it. I hired a professional tuner who ripped me off and damaged my clutch to the point that I already have the parts and different mechanic lined up to fix it when it goes out completely. I tried the GST basemap after the failed tuning attempt and so far it's work great (except for the messed up clutch but that's not from the GST basemap).

If you get a professional tune make sure they have experience with Ralliarts and keep in mind that experience with EVO 8, 9 and X doesn't count. Learn from my mistake.


PS. Slee's putting out some great numbers and I'm just happy when my car doesn't slip in the high end of 4th...

zx-319

iTrader: (2)

With the ad that show up between you post and your signature, I'm sure a lot of people did not even notice you had a signature.

But anyway, most of the comment propose solution that go further than what you already have.

If you want to see a good example of someone who got a lot more high end power, look at Brian's Sportback. He has some decent power without getting too much torque (because of SST limitations).

Slee256

I agree, Brian has an awesome setup on his Sportback. However, to do that he had to upgrade to a different turbo, which is something that I'm not prepared to do right now....

zx-319

iTrader: (2)

The only way you can get more power in the top end after a tune, is to get a bigger intercooler and bigger turbo.

If you don't want to go this way, you can spend an incredible amount of money to reduce all restrictions and get very minimal gains: better intake, better exhaust.

Our engine does not deliver big high-rpm power simply because our turbo is too small. The maximum air flow of our turbo is not sufficient to maintain the boost pressure at high-rpm.

You can go for E85 if you want, I'm not sure how much gain you can expect
but you'll have to spend for bigger injectors, better fuel pump, etc.....

boondoc

iTrader: (4)

Yea i agree. Bigger turbo is the way to go for more top end. After my tune the car was amazing compared to stock and has way more top end than the horrible factory tune but now i can really feel where the turbo runs out of steam and it's time to upgrade.

Slee256

So, based on what you're saying, let's say that I ONLY upgrade the intercooler but DON'T get a bigger turbo. Will the larger intercooler ALONE give me any noticeable gains on the top end of the power band?

Westbound&down

no.

the turbo dies off flow wise around 5500, there is nothing you can do to change the turbo simply running out of strenght.

mikesim

No. You'll only have better resistance to heatsoak. Keep in mind on a hot day this will feel like more power and response, but mo top end will be gained.