The Joshua Tree

I'm just after seein what peoples preferences are when it comes to a hatch and a 2.5 litre single Turbo V's a JDM 2.0 Twin Scroll, what do you view the positives and negs of both as being ?

I've got to admit i grew up on the iconic sounding Subaru's with the unequal length headers and the unique sounding flat 4 burble sound, from what i've read i believe it's easier to tune the twin scroll and its a stronger engine but has less lower dopwn torque and revs higher, is it to around 8500 revs ?

If you was buying a hatch and you had the choice, would you choose the 2 litre twin scroll but you lose the burble or buy the 2.5 litre UK with better lower down torque amd you keep the burble ?

One other quick question, the JDM cars are generally in a lot cleaner condition, how easy is it to convert the 2.0 twin scroll to unequal length headers and would you recommend it to bring back the burble sound, whats the rough cost to do this as well, you could offset some of the cost by selling on the twin scroll turbo setup. I'm just after gauging opinions as it will probably dictate the direction i'll go in.

1509joe

iTrader: (2)

Think you need to check out some of your info

The Joshua Tree

What am i checking, it would help if you say what ive got wrong as i'll be the first to admit im not as clued up as a lot on here when it comes to the Subaru engines and most of what ive picked up has been on google searches where ive been trying to build my knowledge, yeh you'll get it wrong, your bound too.

1509joe

iTrader: (2)

I don't do typing Sir. Twin scroll = less lag, lower down torque amongst other things. You seem to be mixed up twin scroll can run out of puff at the top of the rev range.

The Joshua Tree

Yeh it seems from my research, and reading a fair few online threads that i have it wrong if what you say is right. I was of the understanding that with the 2.5 litre having a bigger displacement it pulls harder than the 2.0 litre twin scroll before the turbos kick in on either car. yeh the twin scroll will be more efficient once the turbo kicks in as it has equal length headers which means the exhaust pulses will be more equally spaced out so will keep the turbo spinning at a linear rate.

If that's wrong then what ive been reading on my research is wrong, it's not just from one site, ive been reading quite a few threads to try and do my homework as i'm buying a JDM 2.0 litre twin scroll and i need to have some knowledge as the engine has an issue which is a chance for me to choose the direction i want to go in hence the reason for the thread, the price of the car obviously reflects the issue.

It was the current owner that contacted me as he knew i was looking for a blue hatch, he thought it would give me another different option where i can build my own spec car, he's actually a member on here.

adam.pah

I currently have both a twin scroll and single scroll setup and in my opinion, the twin scroll is better for road driving. It has hardly any lag and is so much more responsive. As Joe mentioned, it does run out of puff at the top of the rev range but does go all the way to 8k rpm.
I like the sound of the twin scroll. It's not as distinctive as the single scroll but I think it actually sounds better with the right exhaust.

Donie

what exhaust would you recommend for a twin scroll impreza?

adam.pah

I have a non-resonated titanium on mine. It's fairly quite around town but does get louder when you give it some beans. It is a subtle exhaust though. One of my mates has the HKS one on his and that's a louder. I'm not a fan of the really loud exhausts on a twin scroll though, Nur-Spec and Tomei are too much for me.

JdmSti2006

3" decat - RCM ,tomei ,invidia all big money and loud
3" downpipe with sportscat - milltek , Hayward&Scott
i swapped RCM for Milltek with sportscat plus HKS silent power backbox, soon Jetex backbox will replace HKS

The Joshua Tree

When mine is back on the road i'm toying with the idea of putting an invidia R400 on it, i know they are loud, its more to give the twin scroll some kind of deeper, louder sound.

adam.pah

Imo, its easy to make a twin scroll sound like **** if the exhaust is a bit tinny. I prefer a more mellow sound but as we all know, exhaust sound is very much an individual thing. My RA can sound more like a motor bike when it's being driven as it should.

The Joshua Tree

I was thinking originally of converting my Twin Scroll to an unequal length setup but ive taken in what other people have said, including your post on the subject, i think its a case of i need to follow my brain rather than my heart where my brain is saying to leave it as a twin scroll as people have said the performance and pull of the twin scroll is amazing compared to the 2.5. Honestly it would take a lot of me to drop the idea of having the burble as that's how i see a subaru, its part of the car and its iconic history, its why a lot of people buy and like V8's for the sound and roar they make, it wouldn't be the same car if it sounded like a Focus or a Corsa etc.

Vxr2010

a 2.5 with a small turbo works well as per the Fsti , full boost is at 2200 rpm , as it’s not a large turbo so mpg is better , still puts out 340 bhp and same level of foot pound , and as quick as an sti , twin scroll as above has less lag than a standard 2 litre sti , 2 litre is the stronger engine , the 2.5 often in standard ish tune has more torque than a 2 litre so you don’t need the higher revs , mine hits 7200 rpm but you don’t need to go that high , yes jdm cars are often better condition but not always , some of japan’s regional weather is the same as the uk so rust can be an issue , but my money is on jdm cars partly because my model of car was only ever a jdm car and never officially imported , i would drive a few car’s and see what you like , i don’t like the standard 2 litre sti engine lag , i’ve not dry driven a twin scroll but would like to see what it’s like , if you trust google a twin scroll has more lag then a fsti set up 👍

adam.pah

I totally get where you are coming from, I owned UK single scroll cars for 10 years before getting a twin scroll and was also concerned about losing the burble. For me, it's always been about how the cars drive though so that's why the twin scroll would be my go to now. And I have driven various models and specs over the years, both Impreza's and Fozzy's. It's always going to be a case of one person likes it this way and another person the other way. What I would say is stay true to what you have, converting a twin scroll to a single scroll is a lot of work and expense and will ultimately devalue the car (probably).

Just to play devil's advocate though, why not buy 2 and have the best of both worlds!

The Joshua Tree

You might be laughing but i did consider it lol, only because a UK car that i went to view and agreed to buy fell through because of the DVLA, it had a private plate on it that needed to be changed back to the original plate. After 1 half months the DVLA still hadn't done it, i contacted the seller and he fully understood that i needed to look at other options i had, he was just as miffed with the DVLA as i was. Anyway, i bought this twin scroll yesterday morning, the seller of the other car rang in the afternoon asking would i still be interested as the log book had finally turned up, i though hmmmmm, errrrrrrr, should i, no i can't, hang on maybe, no i can't etc lol

adam.pah

Ha ha! It’s meant to be. Do it! 😜

JdmSti2006

burble is muted on UK 2.5l , same exhaust sounds different -worst than on UK 2.0

fpan

iTrader: (11)

I've owned both a "stage1" modified (air filter, turbo back exhaust and remap) FSTi as well as a 2.0 twinscroll GRB and the twinscroll pulls better everywhere along the rev range feeling like a supercharged motor.
The twinscroll is definitely the engine that is more responsive.
The FSTi was around 330bhp, the twinscroll is standard 300.

Julian Layton

Did you end up getting the R400 on yours? Im thinking of doing the same and keen to know how it will sound and if there were any issues fitting it?

EddScott

I have a HKS Silent cat back on my RA. Guy I bought it off sold it as it was too quiet for him. I don't like intrusive exhausts so this suits me. My Evo has a HKS titanium cat back which isn't actually "that" much louder than the silent.

When comparing the two engine notes, you can still hear the flat four burble over the inline 4 of the Evo but it's not as pronounced as a flat 4 with unequal manifold.

Vxr2010

i have both options , well 5 ish options , just because it’s twin scroll or elh v uel , it does not mean you totally loose the noise with elh it’s still distinctive , for performance the elh fsti feels smother and quicker but i’ve never tried head to head , the uel fsti is still very quick , my third fsti is not even mapped , it has a mid section silencer delete and no sports cat unlike the other two , plus sports back box , the mid silencer delete gives it a much more scooby noise plus about 30 per cent louder , then i have a 5.7 v8 , that is not only way louder than the fsti but noise wise is very much on par probably better , then i have a 6.2 v8 😂😂