2.0 or 2.5 what's better?
17 February 2009, 04:18 PM
#61
MY00 UK + TD05-16g (and supporting mods):
Stayed with the 2.0ltr formula myself when faced with piston ring damage and weighing up the 2.0ltr vs 2.5ltr options.
I've even stuck with the rusty TD05-16g and it's been like that for some 4 years as it just seems to work so well. A well setup mid 300s is enough to show its heels to cars of much higher power and specs.
I would have considered the 2.5ltr if going for 450+.
In response to the original question, much will depend on your budget, goals and what you are after.
Stayed with the 2.0ltr formula myself when faced with piston ring damage and weighing up the 2.0ltr vs 2.5ltr options.
I've even stuck with the rusty TD05-16g and it's been like that for some 4 years as it just seems to work so well. A well setup mid 300s is enough to show its heels to cars of much higher power and specs.
I would have considered the 2.5ltr if going for 450+.
In response to the original question, much will depend on your budget, goals and what you are after.
Last edited by Aztec Performance Ltd; 17 February 2009 at 04:28 PM.
17 February 2009, 08:20 PM
#62
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Here is a MY 06 Spec C graph running stock VF36 twin scroll turbo. Only mods are RCM 3" decat exhaust & K & N filter. Fuel used: BP Ultimate with NF Booster. I would be interested to see similar stats for a 2.5 liter engine with basic exhaust mods.
Last edited by Blind Side; 17 February 2009 at 08:56 PM.
17 February 2009, 08:55 PM
#63
Seriously dodgy boost control on show there. When i put the decat on my twin scroll i only did one pull at full throttle just prior to the first flash to check the stock setup had no isues, it felt exactly as that shows, surging up and down to the peak torque point.
Get it remapped, you wont believe the difference, torque will be up around 390lbft and smooth as silk if it's done well.
Get it remapped, you wont believe the difference, torque will be up around 390lbft and smooth as silk if it's done well.
17 February 2009, 10:10 PM
#67
That says 365BHP @ 6055rpm, 404lbft @ 3455rpm.
Dyno graphs are pretty useless without stating all the modifications to achieve the figures, including the fuel used.
Going very nicely Tony thanks, just the brakes to sort and I'll be happy with it.
Dyno graphs are pretty useless without stating all the modifications to achieve the figures, including the fuel used.
Going very nicely Tony thanks, just the brakes to sort and I'll be happy with it.
17 February 2009, 10:17 PM
#69
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[QUOTE=johnfelstead;8517995]That says 365BHP @ 6055rpm, 404lbft @ 3455rpm.
Dyno graphs are pretty useless without stating all the modifications to achieve the figures, including the fuel used.
TD05-20g, supporting mods, mapped by Andy F, on v-power
Dyno graphs are pretty useless without stating all the modifications to achieve the figures, including the fuel used.
TD05-20g, supporting mods, mapped by Andy F, on v-power
17 February 2009, 10:17 PM
#70
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Tony Burns is right, and his knowledge is EVIDENCE based, not based on what he THINKS he knows. Factually, technically, mechanically, the 2 litre twin scroll engine is the best one that Subaru manufacture.
Why was the WRC car based on a 2.0 and not a 2.5?
In the case of STI, an STI engine is not a proper STI engine unless it redlines at 8000 revs. Oh it may have big low end torque, big deal, at the expense of paying through your nose fuel and tax costs?
The 2.5 engine was introduced on UK cars to compensate for variations due to Euro emission laws. It was not introduced as a 'hey, lets make a superb fantastic 2.5 engine for UK cars' How come the JDM even today still has the 2.0 engine? JDM only for the REAL STI driving experience.
Why was the WRC car based on a 2.0 and not a 2.5?
In the case of STI, an STI engine is not a proper STI engine unless it redlines at 8000 revs. Oh it may have big low end torque, big deal, at the expense of paying through your nose fuel and tax costs?
The 2.5 engine was introduced on UK cars to compensate for variations due to Euro emission laws. It was not introduced as a 'hey, lets make a superb fantastic 2.5 engine for UK cars' How come the JDM even today still has the 2.0 engine? JDM only for the REAL STI driving experience.
WRC = 2.0L = regs
JDM = 2.0L = taxation
17 February 2009, 10:44 PM
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17 February 2009, 10:58 PM
#73
[quote=scooby401;8518026]You need to be more specific, supporting mods could be £5 or £2K worth of parts. If you want this thread to be of any use to other people trying to judge what their options are they need the full story. Put the normal retail prices next to the parts/services if you really want it to be an honest apraisal of value/performance.
17 February 2009, 11:10 PM
#74
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2.0 STI semi closed block
forged pistons
forged rods
Inlet Manifold heat spacers
STI heads
STI-5 Cams
3 port boost solenoid
uprated plugs "8's"
CDF lightened pulley kit
Dump valve delete mod
MD 321T
Hybrid front mount intercooler
Ported OE headers and matching up pipe
H&S decat downpipe
H&S Res centre pipe
H&S jap style angle exit backbox
421bhp 375t
forged pistons
forged rods
Inlet Manifold heat spacers
STI heads
STI-5 Cams
3 port boost solenoid
uprated plugs "8's"
CDF lightened pulley kit
Dump valve delete mod
MD 321T
Hybrid front mount intercooler
Ported OE headers and matching up pipe
H&S decat downpipe
H&S Res centre pipe
H&S jap style angle exit backbox
421bhp 375t
17 February 2009, 11:18 PM
#75
The JDM emissions laws aren't as strict as the USA or EU, thats why the 2.5 came about initially, it's easier to make the emissions levels on a larger engine.
The twin scroll engine is a homologation special design for the Production WRC, the ECU has the ability to run MAFless and the inlet plenum has an AIT sensor that isn't used in road trim configuration, it only gets accessed with the Group N mapping. The VF36/37 twin scroll turbo has a perfect match to the airflow a 32mm restrictor can flow, so it is capable of large torque at low/mid range, but isn't a high horsepower setup. The ECU on some of the JDM twin scrolls has the ability to map each gear individually for boost control, so you can pull as much boost in 2nd as you can in 6th, this makes a very tractable road engine that gives a lot of low gear acceleration you might struggle to match with a 2.5 on the stock turbo.
The twin scroll engine is a homologation special design for the Production WRC, the ECU has the ability to run MAFless and the inlet plenum has an AIT sensor that isn't used in road trim configuration, it only gets accessed with the Group N mapping. The VF36/37 twin scroll turbo has a perfect match to the airflow a 32mm restrictor can flow, so it is capable of large torque at low/mid range, but isn't a high horsepower setup. The ECU on some of the JDM twin scrolls has the ability to map each gear individually for boost control, so you can pull as much boost in 2nd as you can in 6th, this makes a very tractable road engine that gives a lot of low gear acceleration you might struggle to match with a 2.5 on the stock turbo.
17 February 2009, 11:36 PM
#76
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The JDM emissions laws aren't as strict as the USA or EU, thats why the 2.5 came about initially, it's easier to make the emissions levels on a larger engine.
The twin scroll engine is a homologation special design for the Production WRC, the ECU has the ability to run MAFless and the inlet plenum has an AIT sensor that isn't used in road trim configuration, it only gets accessed with the Group N mapping. The VF36/37 twin scroll turbo has a perfect match to the airflow a 32mm restrictor can flow, so it is capable of large torque at low/mid range, but isn't a high horsepower setup. The ECU on some of the JDM twin scrolls has the ability to map each gear individually for boost control, so you can pull as much boost in 2nd as you can in 6th, this makes a very tractable road engine that gives a lot of low gear acceleration you might struggle to match with a 2.5 on the stock turbo.
The twin scroll engine is a homologation special design for the Production WRC, the ECU has the ability to run MAFless and the inlet plenum has an AIT sensor that isn't used in road trim configuration, it only gets accessed with the Group N mapping. The VF36/37 twin scroll turbo has a perfect match to the airflow a 32mm restrictor can flow, so it is capable of large torque at low/mid range, but isn't a high horsepower setup. The ECU on some of the JDM twin scrolls has the ability to map each gear individually for boost control, so you can pull as much boost in 2nd as you can in 6th, this makes a very tractable road engine that gives a lot of low gear acceleration you might struggle to match with a 2.5 on the stock turbo.
Last edited by MrRA; 17 February 2009 at 11:38 PM.
17 February 2009, 11:38 PM
#77
Scooby Regular
2.0 STI semi closed block
forged pistons
forged rods
Inlet Manifold heat spacers
STI heads
STI-5 Cams
3 port boost solenoid
uprated plugs "8's"
CDF lightened pulley kit
Dump valve delete mod
MD 321T
Hybrid front mount intercooler
Ported OE headers and matching up pipe
H&S decat downpipe
H&S Res centre pipe
H&S jap style angle exit backbox
421bhp 375t
forged pistons
forged rods
Inlet Manifold heat spacers
STI heads
STI-5 Cams
3 port boost solenoid
uprated plugs "8's"
CDF lightened pulley kit
Dump valve delete mod
MD 321T
Hybrid front mount intercooler
Ported OE headers and matching up pipe
H&S decat downpipe
H&S Res centre pipe
H&S jap style angle exit backbox
421bhp 375t
Holy moly thats some lag, I would take my 2.1 stroker and Turbo Technics T38 over that any day.
200lbft @4000rpm thats a very late spool up. Nice once its spooled up and going, but take its time getting there.
18 February 2009, 12:19 AM
#79
Excellent info as always. Would you say I have this ability for individual boost control on my RA-R? I've finally decided to fit a 3 inch system and get it remapped by either JGM or Bob Rawle. It's making 353bhp at the moment on the standard exhaust, albeit with a few mods which are listed in my plus profile. I'm convinced it could have and should have made more power but Powerstation struggled with the SARD injectors and the scaling of the MAF for the APS CAI as they had never seen either before, well that was their excuse anyway.
I would expect you'll see much more torque than you have now with a decat and remap, the RA-R is on VF42 so should give more top end power than the VF36/37 which seem good for about 360BHP. It's the torque that matters on these stock twin scroll engines, short shift it at 5500-6000rpm and it goes very nicely.
18 February 2009, 12:28 AM
#80
Like all these engines, it's the overall package that matters, which is why it's important to list all the mods so you can judge it properly and understand what the user is trying to achieve.
18 February 2009, 12:29 AM
#81
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Hi John
Yes i found the pads could be a little wooden on those brembo's, are you going to retain the standard calipers or upgrade eventually to some AP 4 pots?
Tony
Yes i found the pads could be a little wooden on those brembo's, are you going to retain the standard calipers or upgrade eventually to some AP 4 pots?
Tony
18 February 2009, 12:50 AM
#85
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Aye, will get back to giving these 2.5ltr boys some stick
Daz, the 2.5 is lazy, it delivers its power with ease, hence lazily, and in standard form (which is what we were discussing btw) it doesnt rev as high as the 2ltr single or twin scroll cars (the twin scroll is still the better road car over the 2.5ltr, even in lightly modified form)
What we are not talking about here is spending stupid money on getting xxx power out of the engine, 99.9% of people DONT want to take that route, and the 2.5 is the cheapest option if you want to do that, though most people are happy at the 400bhp mark and with twin scroll technology coming on in leaps and bounds (hence you see manufactures like vauxhall, renault and peugeot producing twin scroll cars) its catching on
Tony
Daz, the 2.5 is lazy, it delivers its power with ease, hence lazily, and in standard form (which is what we were discussing btw) it doesnt rev as high as the 2ltr single or twin scroll cars (the twin scroll is still the better road car over the 2.5ltr, even in lightly modified form
)What we are not talking about here is spending stupid money on getting xxx power out of the engine, 99.9% of people DONT want to take that route, and the 2.5 is the cheapest option if you want to do that, though most people are happy at the 400bhp mark and with twin scroll technology coming on in leaps and bounds (hence you see manufactures like vauxhall, renault and peugeot producing twin scroll cars) its catching on
Tony
18 February 2009, 12:54 AM
#86
I'd put my money on a well specced 2.5 against a similar specced 2.0L any time!!!
18 February 2009, 01:45 AM
#88
What you list is far from the only differences. The twin scroll heads are different, they breath better, the cams are far more agresive and have higher lift (aprox 10% more) , the MY05 onwards have a nitrided and crossdrilled crank. It's the engine that was developed to win the PWRC so is designed around that requirement.
All the various configs have their benefits, for most people they would be happy with any of the choices, which config you end up with depends on a lot of factors that will determine the route you follow. Which engine works for you depends what your car comes with, what you want to achieve and what budget you have.
The USDM 2.5 bottom end was a cheap option for rebuilds (now the £ is worth less it's less beneficial financially), but it has it's flaws, when matched to 2.0 heads to do it right it needs a bit more work than just bolting the heads on. The issue i always had with going 2.5 on a 2.0 original car was come resale, you are limiting your market, some people wont be able to get insured on an engine size increase, insurance companies tend to not mind too much about power hikes, but they get more concerned about CC increases. Once you start going to 400BHP levels they do have head gasket longevity issues, so if you intend to do high miles a 2.0 would be a better option if it's a fit and forget solution.
I've rebuilt a couple of my 2.0 engines from previous cars, one is up around the 120K miles mark at 310BHP i think now with lots of track miles, build them right, service them properly and get them properly mapped and they last a long time. How much an engine costs depends on where you are starting from, buying an outright engine package is always going to cost a lot of money if you have nothing to start with. You have to compare like with like in terms of what you are replacing. If you already have a twin scroll that just needs a rebuild then it's no more expensive than any other version.
18 February 2009, 08:06 AM
#89
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The MD321T is far more capable of top end than the engine is producing there, so it's probably being held back on purpose until the rest of the package is up to handling more. It's more suited for the 2.5 if you want it to spool early.
Like all these engines, it's the overall package that matters, which is why it's important to list all the mods so you can judge it properly and understand what the user is trying to achieve.
Like all these engines, it's the overall package that matters, which is why it's important to list all the mods so you can judge it properly and understand what the user is trying to achieve.
18 February 2009, 08:21 AM
#90
I dont think you can on that model, i think the hawkeye version doesnt have the option for the megarom. The best thing to do is get the ECU version your car has and ask your chosen mapper the question, it is ECU variant specific.
I would expect you'll see much more torque than you have now with a decat and remap, the RA-R is on VF42 so should give more top end power than the VF36/37 which seem good for about 360BHP. It's the torque that matters on these stock twin scroll engines, short shift it at 5500-6000rpm and it goes very nicely.
I would expect you'll see much more torque than you have now with a decat and remap, the RA-R is on VF42 so should give more top end power than the VF36/37 which seem good for about 360BHP. It's the torque that matters on these stock twin scroll engines, short shift it at 5500-6000rpm and it goes very nicely.
The UK STi 2006 sump design is also the twin scroll design.