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-   -   2.1 or 2.5 engine (https://www.scoobynet.com/general-technical-10/1056462-2-1-or-2-5-engine.html)

rsjohn 09 October 2018 12:23 PM

2.1 or 2.5 engine
 
Probably been asked before but hey ho.

So im looking at uprating the engine in my impreza sti widetrack and iv seen a few engine options, 2.0, 2.1, 2.35, 2.5, theres probably more but the main ones iv seen.

Iv seen a couple of engines for sale a 2.1 which is built to a good spec and a 2.5 again built to a good spec.

The 2.5 is alot more ££ than the 2.1.

My aim is to get a quick road car and maybe the odd track day in the future and looking for around 480-500bhp

So which would be better the 2.1 or the 2.5?

thanks

hackisfun 09 October 2018 02:13 PM

The best thing to do would be list the relevant spec and prices of the engine options you are looking at. Parts used will be a big factor on reliability etc.


the 2.5 will have more torque over the 2.1

ScottyPPP 09 October 2018 04:39 PM

The 2.5 will have much better spool and pick up over a 2.1

rsjohn 09 October 2018 04:46 PM


Originally Posted by ScottyPPP (Post 12030062)
The 2.5 will have much better spool and pick up over a 2.1

What turbo did you run on your 2.1?

ScottyPPP 09 October 2018 04:48 PM


Originally Posted by rsjohn (Post 12030065)
What turbo did you run on your 2.1?

Biggest I had on it was a 20G at 380bhp.

bustaMOVEs 09 October 2018 07:08 PM

A 2.1 cdb has gotta be the reliable one with quality parts of course, 2.5 cd inserts are reliable upto a certain bhp because of thin liners, a 2.35 using a 22t block is great and a in between of both but at a great cost also but the best choice for big power builds.
take your pick in what you want, any 3 will be fine at your level but needs to be a good build with good parts for reliability

rsjohn 09 October 2018 11:32 PM

This any good, it’s a 2.1?

Ej20 semi closed deck block

Group n arrow billet crankshaft

Group n arrow Conrod’s

ACL race bearings

Omega group n pistons

RCM 14mm head stud conversion

Spec c big port heads with oem spec c cams

Uprated valves and spings

RCM 12mm modified oil pump

Group n Twinscroll baffled sump


bustaMOVEs 10 October 2018 05:59 PM

Thats a very good spec, but I don’t understand why spend so much on a arrow crank and use a scd?
get a recipt for that build to confirm

rsjohn 10 October 2018 06:18 PM


Originally Posted by bustaMOVEs (Post 12030211)
Thats a very good spec, but I don’t understand why spend so much on a arrow crank and use a scd?
get a recipt for that build to confirm

Chevron built the engine

the shreksta 10 October 2018 07:32 PM


Originally Posted by bustaMOVEs (Post 12030211)
Thats a very good spec, but I don’t understand why spend so much on a arrow crank and use a scd?
get a recipt for that build to confirm

same.....

i thought the standard subaru crank was good for 600-700 bhp so see no reason to pay ££££ for a billet one

bustaMOVEs 10 October 2018 09:40 PM

My issue is, pay upwards of 2-3k for a arrow crank but yet use a scdb? The arrow crank can take some serious rpm!
the rest of the build is more than perfect though

rsjohn 10 October 2018 10:06 PM


Originally Posted by bustaMOVEs (Post 12030211)
Thats a very good spec, but I don’t understand why spend so much on a arrow crank and use a scd?
get a recipt for that build to confirm


Originally Posted by the shreksta (Post 12030219)
same.....

i thought the standard subaru crank was good for 600-700 bhp so see no reason to pay ££££ for a billet one


Originally Posted by bustaMOVEs (Post 12030264)
My issue is, pay upwards of 2-3k for a arrow crank but yet use a scdb? The arrow crank can take some serious rpm!
the rest of the build is more than perfect though

iv not paid that for it so Iv gained a very good spec engine for less £££

scoobypaul_temp 10 October 2018 11:35 PM


Originally Posted by rsjohn (Post 12030267)

iv not paid that for it so Iv gained a very good spec engine for less £££

You haven't paid for it - but the point being made is that it doesn't match the rest of the build. But, if you got it at a good price, and don't push it too far, bargain :thumb:

domino46 11 October 2018 06:21 AM

had both the 2.1 and my current 2.5 ,,, prefer the 2.5 for the road ,, 2.1 for the track

bustaMOVEs 11 October 2018 06:49 PM


Originally Posted by scoobypaul_temp (Post 12030279)
You haven't paid for it - but the point being made is that it doesn't match the rest of the build. But, if you got it at a good price, and don't push it too far, bargain :thumb:

this.
p.s I'd want proof of that billet crank as that's a lot of pee. And pics of build from seller?

k_duraman 14 October 2018 07:43 AM

if built propperly , a 2,5 will be better on every aspect. it will have better torque and earlier spool. that spec you have given for the 2.1 is over kill regarding the crank and the oil pump. both the crank and the oil pump would be a good investment if you want to achive 700+bhp at some point but want to hang around at 450bhp mark for a while. but then you wouldn't take a semi cd as your base (scd runs out of breath after 550ish bhp). also there is the 14mm stud issue for me. i dont have experience building a big hp 2 liter so not sure about clearances but on a 2.5 semi cd it would be a big no no for me to put 14mm studs as they touch the liners and thin the liners down. if when they drill bigger holes (for the 14mm studs) on a 2 liter block and touch the liners you could easily crack a cylinder wall. i beleive the arrow crank, 12mm rcm oil pump and the 14mm studs belong to a cdb or even a sleeved block aiming for at least 700+ bhp. you dont put an arrow crank in your engine for 450 bhp. it is like giving a gold plated barbie doll to your 3 year old.

the shreksta 14 October 2018 09:04 AM


Originally Posted by k_duraman (Post 12030624)
if built propperly , a 2,5 will be better on every aspect. it will have better torque and earlier spool. that spec you have given for the 2.1 is over kill regarding the crank and the oil pump. both the crank and the oil pump would be a good investment if you want to achive 700+bhp at some point but want to hang around at 450bhp mark for a while. but then you wouldn't take a semi cd as your base (scd runs out of breath after 550ish bhp). also there is the 14mm stud issue for me. i dont have experience building a big hp 2 liter so not sure about clearances but on a 2.5 semi cd it would be a big no no for me to put 14mm studs as they touch the liners and thin the liners down. if when they drill bigger holes (for the 14mm studs) on a 2 liter block and touch the liners you could easily crack a cylinder wall. i beleive the arrow crank, 12mm rcm oil pump and the 14mm studs belong to a cdb or even a sleeved block aiming for at least 700+ bhp. you dont put an arrow crank in your engine for 450 bhp. it is like giving a gold plated barbie doll to your 3 year old.

how come so many engine builders recommend 14mm head studs then? only 1 place i have spoken to said they are not needed and that an extreme version of the 11mm will be more than enough.


bustaMOVEs 14 October 2018 05:07 PM

I'm with k duraman 100% there, apart from the 2.5 better in every aspect (not as good as a 2.1 cdb on track when at extreme temps the 2.5 liners will be weaker and could crack etc)

amd yes 11 extreme are fine for most applications, shrek, most say 14 as it's probably sounds safer for the customer lol. What folk tell you take with a pinch of salt and figure the wider picture out yourself and go from there on what's suitable and what's not.

the shreksta 14 October 2018 06:50 PM


Originally Posted by bustaMOVEs (Post 12030671)
I'm with k duraman 100% there, apart from the 2.5 better in every aspect (not as good as a 2.1 cdb on track when at extreme temps the 2.5 liners will be weaker and could crack etc)

amd yes 11 extreme are fine for most applications, shrek, most say 14 as it's probably sounds safer for the customer lol. What folk tell you take with a pinch of salt and figure the wider picture out yourself and go from there on what's suitable and what's not.

really dont know which way to turn now lol


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