High compression or more cylinder volume ????????............

[Koom]

 vf20/21bg5']

[quote name='Koom said:

Higher compression will limit your det threshold which could limit the amount of peak torque you can make, not just top end power as its not exactly choking flow in the top end.

/quote]ok cool...now wer getting to all the good bits....but wot if i want everything in my engine build to happen well b4 redline like changing gear at 7-7500rpm thus limiting bottom end engine failure as these engines are renound for ?????.....and in this im meening for quik spooling well earlier than standard obviously sacrificing my top end fully

2.5L with a VF23 would spool early and make 200kw by about 5k rpm if done right.

......as thr is another thread debating the same things here ill keep it simple for my final posts.....is it better for my 2.0ltr build (quik off the mark,spooling hi asap etc etc) to go hi-compression(maxed out skimmed heads,thin gaskets etc etc..)..or is it not going to make much difference at all really???..all im after is an answer like "its better than not doing it" or "you shouldnt do it cause"?

In my opinion, I'd stay with normal compression (~8.5:1) as there's other ways to increase spool without loosing det resistance which as I mentioned earlier, can limit the amount of peak torque you can make. Long rods would be better I reckon. Or AVCS heads and twin scroll

2.5L would still be better.

[Koom]

 vf20/21bg5']

[quote name='ODB said:

Doesnt funkytown have that on his 2.0???????

/quote]

Possibly, flatmates 2.0L longrod motor made about 200kw by 4k rpm and ran out of puff by 5.5k rpm. His dad's 2.35L made +220kw at 4k but also choked by 5.5k rpm. Totally different to a street engine though as they ran restrictors and were close to freeboosting down low for max torque and the restrictor kills power in the top end.

Bigger displacement will always win the spooling race (all other things kept equal).

...holly **** really maxed out at 5.5rpm WOW!...ok now thats alot shorter than what t i want from a 2.0ltr but i bet his bottom end would last???

Gets rebuilt once a year or so. Race motor's need it. Still going strong with the new owner as far as I know.

[Guest]

If you go high compression you will need a turbo that flows well at lower pressure ratios.

[Guest vf20/21bg5]

 Koom']

[quote name='Koom said:

Higher compression will limit your det threshold which could limit the amount of peak torque you can make, not just top end power as its not exactly choking flow in the top end.

/quote]ok cool...now wer getting to all the good bits....but wot if i want everything in my engine build to happen well b4 redline like changing gear at 7-7500rpm thus limiting bottom end engine failure as these engines are renound for ?????.....and in this im meening for quik spooling well earlier than standard obviously sacrificing my top end fully

...ok cool thanx koom you have told me all i wanted to know from this thread altho i will leave it open for others to learn off.....im looking at buying the rods soon so do i ask around on here for some long rods or trademe?what are the price differences from 4340 h-beam to the same but long rods?.....

2.5L with a VF23 would spool early and make 200kw by about 5k rpm if done right.

......as thr is another thread debating the same things here ill keep it simple for my final posts.....is it better for my 2.0ltr build (quik off the mark,spooling hi asap etc etc) to go hi-compression(maxed out skimmed heads,thin gaskets etc etc..)..or is it not going to make much difference at all really???..all im after is an answer like "its better than not doing it" or "you shouldnt do it cause"?

In my opinion, I'd stay with normal compression (~8.5:1) as there's other ways to increase spool without loosing det resistance which as I mentioned earlier, can limit the amount of peak torque you can make. Long rods would be better I reckon. Or AVCS heads and twin scroll

2.5L would still be better.

[Guest vf20/21bg5]

 Qwerty said:

If you go high compression you will need a turbo that flows well at lower pressure ratios.

...wot wld you recomend? is a t3-4 silly to use in a twisted turbo set-up with link etc

[Koom]

Long rods is something that you're going to have to source from overseas and need someone clued up to fit it all. If using that option better to leave it to the engine builder to source the parts too.

[Koom]

 vf20/21bg5']

[quote name='Qwerty said:

If you go high compression you will need a turbo that flows well at lower pressure ratios.

/quote]...wot wld you recomend? is a t3-4 silly to use in a twisted turbo set-up with link etc

Depends if you can find a compressor map for it to get an idea of what its ideal operating conditions are.

[Guest]

I don't know that turbo sorry. Just look at its comp map and see if it flows enough at lower PR

A lower comp higher boost engine should make more power than a higher comp low boost engine.

Its not as efficient as higher compression but it will flow better.

[Guest vf20/21bg5]

 Koom said:

Long rods is something that you're going to have to source from overseas and need someone clued up to fit it all. If using that option better to leave it to the engine builder to source the parts too.

..ok well as im building the engine i think ill steer clear of the long rods if thy are that much of a specialist componant altho i do know how to work out static compression ratio's and do most of the things an engine builder would do to the block like dry fitment of tolerences with flexi-gauge,piston ring end gaps and side clearances,crank end float,clay ontop of piston test etc etc etc and so-on..... all the things i learnt i my 6 month pre-apprentiship course b4 i became trade certified,lol still got all those books too frm wen i was 17 heheh.....i think ill just go for thr hi-comp as i originally thought but will be printing off all of your guys information thats for sure....MAN I LUV THIS SITE ! ;D

[funkytown]

 ODB said:

Doesnt funkytown have that on his 2.0???????

lol you talking about me ehhh.. ;D

i do have a "worked 23" on my 2.oL.. and its all over by about 6grand.. Im freeboosting from 6 and its choked itself to death.

Mine made 235..

[Guest vf20/21bg5]

 funkytown']

[quote name='ODB said:

Doesnt funkytown have that on his 2.0???????

/quote]

lol you talking about me ehhh.. ;D

i do have a "worked 23" on my 2.oL.. and its all over by about 6grand.. Im freeboosting from 6 and its choked itself to death.

Mine made 235..

sorry my bad but wots a "worked 23"?

[funkytown]

all good..

worked VF23

Its been high flowed, ported on the exhuast side with completely new "internals". Has a cut back exhaust wheel and similier to a 17g wheel on the compressor side.. supposed to flow about 20% more than a 22.

It pushed my 235 at 18-19psi.. 15-16 at the redline (freeboosting).. dies from 6k

[Guest vf20/21bg5]

 funkytown said:

all good..

worked VF23

Its been high flowed, ported on the exhuast side with completely new "internals". Has a cut back exhaust wheel and similier to a 17g wheel on the compressor side.. supposed to flow about 20% more than a 22.

It pushed my 235 at 18-19psi.. 15-16 at the redline (freeboosting).. dies from 6k

..wouldnt reving it to only 6grand give you more life to your bearings? ond was the engine a hi-comp engine or just sti specs etc?

[ODB]

 funkytown said:

all good..

worked VF23

Its been high flowed, ported on the exhuast side with completely new \"internals\". Has a cut back exhaust wheel and similier to a 17g wheel on the compressor side.. supposed to flow about 20% more than a 22.

It pushed my 235 at 18-19psi.. 15-16 at the redline (freeboosting).. dies from 6k

and realistically its more about driveability than absolute maximum hp anyhow.

if you have a tidal wave at torque pretty much from 2.5k-6k then its all good right?

[funkytown]

 ODB']

[quote name='funkytown said:

all good..

worked VF23

Its been high flowed, ported on the exhuast side with completely new \"internals\". Has a cut back exhaust wheel and similier to a 17g wheel on the compressor side.. supposed to flow about 20% more than a 22.

It pushed my 235 at 18-19psi.. 15-16 at the redline (freeboosting).. dies from 6k

/quote]

and realistically its more about driveability than absolute maximum hp anyhow.

if you have a tidal wave at torque pretty much from 2.5k-6k then its all good right?

it does.. and it hoons..

 

..wouldnt reving it to only 6grand give you more life to your bearings? ond was the engine a hi-comp engine or just sti specs etc?

its fully forged with fancy headstuds.. standard sti bearings though. It has standard 2.0l displacement and compression.

Its built to take beating and not lunch itself.. i.e. be with in good tolerance on the block and internals.

The turbo is the limiting factor in my set up. limit is set to 7grand but im punching into that real easy at the monent so going to get it extended to 7.5 grand to allow for head room when "overshooting" and should be changing gears.

[Solja]

im in the same situation as you funkytown on my v3 engine in the legacy, the rev limit has been set to 7200 and i quite often hits this to easy, link says 27 times out of 1600 engine starts , i was thinking raising it to 7500-7600 as with the 20g turbo it kept making power to redline but because of the lower rev limit and the intake charge was just starting to get abit to hot which will be sorted out with meth water injection

[Guest vf20/21bg5]

...sounds like th go guys...for me it will be a safe 7000rpm limit ,boosting asap from my hi-compression loosing its legs at around 6500rpm keeping that bottom end safe....i too will be running eagle rods,je pistons,acl bearings and arp head studs-rod bolts etc so should easily withstand hi boost at lowish revs as that bottom end setup is made for up to 800hp altho i wont be cross-drilling my crank i will be extending my sump by 2ltrs and running an oil cooler...cross drilling is a must for anything that revs hi and runs over 280-300kw..so ive read and been told....cheers for your help guys

[Guest vf20/21bg5]

 funkytown said:

all good..

worked VF23

Its been high flowed, ported on the exhuast side with completely new "internals". Has a cut back exhaust wheel and similier to a 17g wheel on the compressor side.. supposed to flow about 20% more than a 22.

It pushed my 235 at 18-19psi.. 15-16 at the redline (freeboosting).. dies from 6k

..please explain "freeboosting"? as ive built lots of hi-com engines(old v8's,4's and 6's) ive got no experience with turbo'd builds and sum lingo......lol

[Guest]

Whats a cut back exhaust wheel? pics?

[Koom]

 vf20/21bg5']

[quote name='funkytown said:

all good..

worked VF23

Its been high flowed, ported on the exhuast side with completely new "internals". Has a cut back exhaust wheel and similier to a 17g wheel on the compressor side.. supposed to flow about 20% more than a 22.

It pushed my 235 at 18-19psi.. 15-16 at the redline (freeboosting).. dies from 6k

/quote]..please explain "freeboosting"? as ive built lots of hi-com engines(old v8's,4's and 6's) ive got no experience with turbo'd builds and sum lingo......lol

Freeboosting. Its what its called when you aren't controlling the boost, just leaving the wastegate shut and letting the turbo make as much boost as it possibly can make. Not for the fainthearted

What ECU are you going to use for your build? Need good control of the engine if wanting to get maximum gains from high compression. Also I had a quick chat with my friendly engine builder today and the engine in the Legacy rally car we built a year ago has normal length rods but about 9.5:1 compression and really good heads. Its tuned on BP 98 aswell and makes about 210kw @ 4k rpm (also has a restrictor on the turbo inlet). Is a really nice strong engine. Felt a hell of alot torquier than my normal EJ20 with a TD05 with about the same top end.

[Guest boostcut]

 Solja said:

im in the same situation as you funkytown on my v3 engine in the legacy, the rev limit has been set to 7200 and i quite often hits this to easy, link says 27 times out of 1600 engine starts , i was thinking raising it to 7500-7600 as with the 20g turbo it kept making power to redline but because of the lower rev limit and the intake charge was just starting to get abit to hot which will be sorted out with meth water injection

is that all? when brad was at hampton downs he hit limiter something like 150 times in 4 laps

[wrx_lou]

 boostcut said:

is that all? when brad was at hampton downs he hit limiter something like 150 times in 4 laps

lol the bottem half of his rod also ended up dropping into his sump. :

[WRXER]

I had that issue initially, and found a much simpler solution... Chuck in a shift light and set it a few hundred revs earlier then u would usually change. U will find eventually you will get use to the power and have no issues changing before hitting redline, never really needed to adjust the redline.

[Guest vf20/21bg5]

 Koom']

[quote name='funkytown said:

all good..

worked VF23

Its been high flowed, ported on the exhuast side with completely new "internals". Has a cut back exhaust wheel and similier to a 17g wheel on the compressor side.. supposed to flow about 20% more than a 22.

It pushed my 235 at 18-19psi.. 15-16 at the redline (freeboosting).. dies from 6k

/quote]..please explain "freeboosting"? as ive built lots of hi-com engines(old v8's,4's and 6's) ive got no experience with turbo'd builds and sum lingo......lol

Freeboosting. Its what its called when you aren't controlling the boost, just leaving the wastegate shut and letting the turbo make as much boost as it possibly can make. Not for the fainthearted

What ECU are you going to use for your build? Need good control of the engine if wanting to get maximum gains from high compression. Also I had a quick chat with my friendly engine builder today and the engine in the Legacy rally car we built a year ago has normal length rods but about 9.5:1 compression and really good heads. Its tuned on BP 98 aswell and makes about 210kw @ 4k rpm (also has a restrictor on the turbo inlet). Is a really nice strong engine. Felt a hell of alot torquier than my normal EJ20 with a TD05 with about the same top end.

when it comes to the time i will be doing my homework on a link managment system of a cost of around 2g with all the goodies in it as ill be taking it to "tuning and performance" in ham so thy will expect nothing less out of this type of build for thr final tuning....i think ill be looking at around 9.0:1 to 9.2:1 comp with p&p v5 heads,sti cams,head skimed as far as thy will go(clay on piston testing as i go) big je or wiseco forgies,balanced crank,lightend 4-4.5kg flywheel blah blah blah(and bottom end as i said at beginning of thread)match porting everything as i go,v5 long runner sti manifold (flipped)with custom adapted plenum(lager) new 70mm throttle body,aftermarket intake/exhaust/turbo,big feul system a must... blah blah blah and the list goes on and on........i originally gave myslf a budget of around 12g all up but think this one will be nearer 16g...i know i could buy somthing already built by the pro's for that price that would knock my sox off but wer's the fun in that?...i like the build up and the thrill of it all wen after 1yr building a semi monster tune it can be started and ran... will putting all my weekly income into it so not having to pay interest on a loan, taking my time and doing my homework for every little thing i do as i go.....god im glad ive been on holiday the last couple of weeks as ive spent all my savings buying and doing the following..... sort out the closed deck block and orginise prices for reconditioning work,strip block and send parts,orginise heads,cams,head work and p&pwork(thanx dacca)buy all new air tools/compressor/the latest micrometers and inside micrometers(man thy r dear)..so its been a good start with $3000 spent already not including the $1700 for pistons/rings and conrods or the $1500 for gasket sets/arp head studs/casing bolts blah blah blah...ive built a few old school engines in my time from scratch but nothing quite like this.

[Solja]

if i was on the track im sure id hit alot more but these stats are all daily driving, ill still raise rpm to 7500 bt as wrxer said i may get a shift light installed