Ultimate Impreza 2.0 or 2.5 ?
21 November 2002, 03:31 PM
#31
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Nos,
My car hasn't been on the rollers. Any figures that I have, are from an engine bench dyno.
Yes I did have an over fuelling problem at Elvington, and yes unfortunately, I've since snapped a piston gudgeon pin. However, the gudgeon pins JE supplied were the wrong spec', and my supplier, being a person of integrity, is replacing ALL the damaged parts FOC !!!!
My engine first went on the dyno a year ago, and in the last year I've not felt a need to post my figures. I built the engine as a personal challenge, and because I couldn't understand why no one had already done one in the UK, when they are common in Aus'.
The engine has been proven on the dyno, and because I was unlucky because of an incorrectly supplied part, I've now had the benifit of being able to strip, and inspect the engine, to see how the bearings, etc' were holding up. They were fine, as were all the other internal parts.
The engine is being re-built to the same spec' (+ a few additions
I may, or may not put it on the RR. So long as I'm happy with it, it really doesn't matter if people know the figures, or believe the rumours. Not to me anyway.
Mark.
My car hasn't been on the rollers. Any figures that I have, are from an engine bench dyno.
Yes I did have an over fuelling problem at Elvington, and yes unfortunately, I've since snapped a piston gudgeon pin. However, the gudgeon pins JE supplied were the wrong spec', and my supplier, being a person of integrity, is replacing ALL the damaged parts FOC !!!!
My engine first went on the dyno a year ago, and in the last year I've not felt a need to post my figures. I built the engine as a personal challenge, and because I couldn't understand why no one had already done one in the UK, when they are common in Aus'.
The engine has been proven on the dyno, and because I was unlucky because of an incorrectly supplied part, I've now had the benifit of being able to strip, and inspect the engine, to see how the bearings, etc' were holding up. They were fine, as were all the other internal parts.
The engine is being re-built to the same spec' (+ a few additions
I may, or may not put it on the RR. So long as I'm happy with it, it really doesn't matter if people know the figures, or believe the rumours. Not to me anyway.Mark.
21 November 2002, 03:47 PM
#32
NOS numptie,
After carefully considering your advice, i have ditched my plans for a 2.0L engine. My new project will be to take the 1.3L Justy engine, and use a huge turbo.
If we consider the 2.0l is capable of 420hp, and that smaller is better, 2.0/1.3*420=646hp
Projected power is 600hp (based on your theory of power), I feel this is conservative, and *wink* think 650hp is obtainable.
Lag may be a problem, but as 2.5L cars have not proven themselves on scoobynet (the ultimate test) I feel that size can only exagerate the problem. I may need to uprate the valvetrain, and have considered destroking the crank to push down the capacity. But a 18000rpm rev limit should provide a flexible tractable enigne.
The evidence is stacked in favour of smaller engines, just look at F1, where the 1.5 cars produced as much as 1500hp, whereas the 3 litre cars produce nearly 800. Obviously the FIA realised they had got it wrong when the dropped from 3.5 to 3, and power has risen as a result by some 50hp.
I may still use the Sti5 engine I bought, but it will probably go into the Justy donor car as a runabout.
Paul
After carefully considering your advice, i have ditched my plans for a 2.0L engine. My new project will be to take the 1.3L Justy engine, and use a huge turbo.
If we consider the 2.0l is capable of 420hp, and that smaller is better, 2.0/1.3*420=646hp
Projected power is 600hp (based on your theory of power), I feel this is conservative, and *wink* think 650hp is obtainable.
Lag may be a problem, but as 2.5L cars have not proven themselves on scoobynet (the ultimate test) I feel that size can only exagerate the problem. I may need to uprate the valvetrain, and have considered destroking the crank to push down the capacity. But a 18000rpm rev limit should provide a flexible tractable enigne.
The evidence is stacked in favour of smaller engines, just look at F1, where the 1.5 cars produced as much as 1500hp, whereas the 3 litre cars produce nearly 800. Obviously the FIA realised they had got it wrong when the dropped from 3.5 to 3, and power has risen as a result by some 50hp.
I may still use the Sti5 engine I bought, but it will probably go into the Justy donor car as a runabout.
Paul
21 November 2002, 03:49 PM
#33
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Pretty much the only reason for the lack of 2.5 litre cars in the UK is the lack of donor engines. In Oz and the US the EJ25 is commonplace. From what I have read on i-club, the only problem with the EJ25 is it's stupendous low down torque that eats clutches until you replace them, at which point it eats gearboxes. Yes, some have thrown rods etc., but it's usually due to poor tuning (much the same as any turbo engine).
Lets face it, if you compare the engines for the same bhp a turbo EJ25 will be running a lower boost to get equivalent power, and therefore a relatively small turbo that spools up easily. Put the turbo off an EJ20 on an EJ25 and you'll see the boost come in at 2000rpm instead of the 3500 it normally would.
Lets face it, if you compare the engines for the same bhp a turbo EJ25 will be running a lower boost to get equivalent power, and therefore a relatively small turbo that spools up easily. Put the turbo off an EJ20 on an EJ25 and you'll see the boost come in at 2000rpm instead of the 3500 it normally would.
21 November 2002, 04:28 PM
#35
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proof is in the pudding and very few of you seem to have any!
pervlo- why mock what you don't understand?
adam m-
so what you are saying is a 350bhp impreza with a with a better shape graph will be faster than a one with a 400bhp one!LMAO, have you got any graphs from your car???
pervlo- why mock what you don't understand?
adam m-
it is the shape of the graph that will indicate the speed of the car, not the peak figure.
21 November 2002, 04:34 PM
#36
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Nos Nova,
yes I am saying exactly that!
you can have a car with 10bh and then a peak of 1000bhp over a 5 rpm range, and another car with 500bhp rom 2000 to 8000 rpm.
There is no question which one will be faster, and it isnt the 1000bhp one!
with a narrow power band you need the gearing to take advantage of it. The car with the better (wider) graph will be able to make better use of the torque at any point, and it also wont be as crucial to hold it in the power band to get it to go fast.
And exactly what part of "my car has been off the road for a year" and "I am waiting for the engine to be built!" dont you understand?
yes I am saying exactly that!
you can have a car with 10bh and then a peak of 1000bhp over a 5 rpm range, and another car with 500bhp rom 2000 to 8000 rpm.
There is no question which one will be faster, and it isnt the 1000bhp one!
with a narrow power band you need the gearing to take advantage of it. The car with the better (wider) graph will be able to make better use of the torque at any point, and it also wont be as crucial to hold it in the power band to get it to go fast.
And exactly what part of "my car has been off the road for a year" and "I am waiting for the engine to be built!" dont you understand?
21 November 2002, 05:08 PM
#37
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NOS Nova,
You cannot use Christian R's car in any of your uk 2.5s are no good "argument", he bought his motor pre build from SubaruUprated2.5litreMotors_R_Us.com.au or similar.
Moray
You cannot use Christian R's car in any of your uk 2.5s are no good "argument", he bought his motor pre build from SubaruUprated2.5litreMotors_R_Us.com.au or similar.
Moray
21 November 2002, 05:09 PM
#38
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The higher up the rpm range you make your torque the more power it produces. A big torque number means SFA if it's at low rpm. Power accelerates your car.
Comparing David Wallis's torque to Harveys means nothing.
If your gearbox's rpm band is say 2000 rpm between gears ie change up at 7500 drops you in at 5500 then it is the average power produced between 5500 and 7500 that dictates how fast you go.
The torque at 4500rpm or 5252 rpm doesn't matter a **** in this case.
Comparing David Wallis's torque to Harveys means nothing.
If your gearbox's rpm band is say 2000 rpm between gears ie change up at 7500 drops you in at 5500 then it is the average power produced between 5500 and 7500 that dictates how fast you go.
The torque at 4500rpm or 5252 rpm doesn't matter a **** in this case.
21 November 2002, 05:16 PM
#39
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Power accelerates your car? I think not.
Power and torque are of course interelated, however, look at WRC cars... limited by air restriction to ~310bhp power, but running maybe 500 ft lb torque, I suspect a WRC car could out-accelerate a "350bhp/300ftlb" 2 litre scooby road car.
Torque accelerates the car.
Power and torque are of course interelated, however, look at WRC cars... limited by air restriction to ~310bhp power, but running maybe 500 ft lb torque, I suspect a WRC car could out-accelerate a "350bhp/300ftlb" 2 litre scooby road car.
Torque accelerates the car.
21 November 2002, 05:26 PM
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Arent the rigoli 10 sec mostly 2.0's or 2.2's. I havent really seen them mention 2.5's on the website, or on any articles their cars are featured in Autospeed.. They just seem to run 35+psi boost to get the results.
That seems to be a big + after the 35psi...
That seems to be a big + after the 35psi...
21 November 2002, 05:27 PM
#42
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power and torque can both accelerate cars, gearing dependent of course.
scoobee,
comparisons are not irrelevant, at all. They have the same gearing exactly! same 3.9 final drive, therefore the rpm drop between gear changes is exactly the same!
power and torque at 5252 give an indication of what the car is going to do, or the state of tune it is in.
For exmple, the stronger 2 litre cars such as trout, bobs, tims etc, were around the 300 mark at 5252 going on to peaks of 350 ish.
We know from experience that this yields a fast car on the road.
To be doing better than that, would be nice to see cars getting that kind of power at the crossover point and going on to getting over 400bhp.
Thats why I asked about harveys car, and as yet have still had no answer on what it can do.
scoobee,
comparisons are not irrelevant, at all. They have the same gearing exactly! same 3.9 final drive, therefore the rpm drop between gear changes is exactly the same!
power and torque at 5252 give an indication of what the car is going to do, or the state of tune it is in.
For exmple, the stronger 2 litre cars such as trout, bobs, tims etc, were around the 300 mark at 5252 going on to peaks of 350 ish.
We know from experience that this yields a fast car on the road.
To be doing better than that, would be nice to see cars getting that kind of power at the crossover point and going on to getting over 400bhp.
Thats why I asked about harveys car, and as yet have still had no answer on what it can do.
21 November 2002, 05:29 PM
#43
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stevie, they run 2.2, 2,3, 2.4 and 2.5.
I think mostly because they reuild all the time, they simply go for the most commonly available parts.
But then you are limiting yourself to rigoli, and they arent the fastest anymore, having been beaten by some sub 9.5s!
the 2.5s are perfectly capable of these too.
try some other aus or american companies, such as perfourmance motorsport.
I think mostly because they reuild all the time, they simply go for the most commonly available parts.
But then you are limiting yourself to rigoli, and they arent the fastest anymore, having been beaten by some sub 9.5s!
the 2.5s are perfectly capable of these too.
try some other aus or american companies, such as perfourmance motorsport.
21 November 2002, 05:33 PM
#44
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Quote the power to weight ratio for any car and I could estimate the acceleration within reason.
Quote the torque to weight ratio and I or you, wouldn't have a clue !
ps BMW do a 2.5 turbo diesel ............loads of torque, who needs a subaru
Quote the torque to weight ratio and I or you, wouldn't have a clue !
ps BMW do a 2.5 turbo diesel ............loads of torque, who needs a subaru
21 November 2002, 05:33 PM
#45
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Ahem...wrong.
Torque is what produces the shove in the back, power will keep you accelerating....sort of.
Gearing will be the important factor here, a car with a lot of torque in the midrange (the typical scoob) won't need low gearing and 10 gears...it manages v well anyhoo...as opposed to a vtec Honda that will have to be kept on boil to have any go.
I'd rather have a car with a MASSIVE area beneath the dyno graph curve than one peaky revhappy bastid....as I'm a crap driver and need power to be there all the time.
/J
P.S. If I could afford to I'd gone for a cdb 2.5 conversion with a mad garret already. Nothing beat cubic inches and a turbo.
Torque is what produces the shove in the back, power will keep you accelerating....sort of.
Gearing will be the important factor here, a car with a lot of torque in the midrange (the typical scoob) won't need low gearing and 10 gears...it manages v well anyhoo...as opposed to a vtec Honda that will have to be kept on boil to have any go.
I'd rather have a car with a MASSIVE area beneath the dyno graph curve than one peaky revhappy bastid....as I'm a crap driver and need power to be there all the time.
/J
P.S. If I could afford to I'd gone for a cdb 2.5 conversion with a mad garret already. Nothing beat cubic inches and a turbo.
21 November 2002, 05:38 PM
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sounds like a good idea jerry, maybe I'll try it.
scoobee,
there is no question that power and torque can both accelerate a car, but it need not be one or the other, I would rather have both.
an F1 car does accelerate fast, but apparently up to 100 on slicks and tarmac, a wrc can stay with one despite having just over a third of the power.
the wrc car use torque to accelerate the F1 cars use power created by meagre torque but massive rpm and lots of gears.
So jerry and others, to put Nos novas mind at rest, is it possible for a broad power curved 350bhp car to be faster than a spiked 400?
scoobee,
there is no question that power and torque can both accelerate a car, but it need not be one or the other, I would rather have both.
an F1 car does accelerate fast, but apparently up to 100 on slicks and tarmac, a wrc can stay with one despite having just over a third of the power.
the wrc car use torque to accelerate the F1 cars use power created by meagre torque but massive rpm and lots of gears.
So jerry and others, to put Nos novas mind at rest, is it possible for a broad power curved 350bhp car to be faster than a spiked 400?
21 November 2002, 05:39 PM
#48
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Right, When you talk about torque you are talking about a force at a set radius (typically lbs - and feet) this means diddly squat until you relate it to a rate of production (typically rpm) at which point you are talking about POWER
21 November 2002, 05:42 PM
#49
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You bet a car with more area will be faster - IF we're not talking about straight line acceleration....it all depends on alot of variables though - like gearing...
I had no problem hammering an M3E46 on track, though it should be faster than me...my power came in harder and sooner.
Bye bye bimmer.
/J
I had no problem hammering an M3E46 on track, though it should be faster than me...my power came in harder and sooner.
Bye bye bimmer.
/J
21 November 2002, 05:44 PM
#50
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Lets think why they decided to fit a restrictor to WRC's ? Er to limit power and hence speed ?? Correct
Why did they not limit torque by a boost limit blow off ? Er Because then engine builders would build high rpm engines that made LOADS of power and they would be fast ? Correct.
Why did they not limit torque by a boost limit blow off ? Er Because then engine builders would build high rpm engines that made LOADS of power and they would be fast ? Correct.
21 November 2002, 05:47 PM
#51
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Not really...as power is about rpm's (and airflow)....which is what's kept down in the WRC engines.
As I said it's a gearing thing....but being able to rev higher will be an advantage...if both cars are similar otherwise.
But it's got very little to do with acceleration. IMHO of course.
/J
As I said it's a gearing thing....but being able to rev higher will be an advantage...if both cars are similar otherwise.
But it's got very little to do with acceleration. IMHO of course.
/J
21 November 2002, 05:52 PM
#53
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Assuming a car is capable operating in it's power band then the car with the higher average power over the used range will accelerate quickest. Regardless of torque - Period
21 November 2002, 05:56 PM
#54
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Quote - "an F1 car does accelerate fast, but apparently up to 100 on slicks and tarmac, a wrc can stay with one despite having just over a third of the power."
This is due to traction and weight distribution. Nothing whatsoever to do with P/W ratio and even less to do with Torque.
This is due to traction and weight distribution. Nothing whatsoever to do with P/W ratio and even less to do with Torque.
21 November 2002, 05:56 PM
#55
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That might be true, but in Adams example you'd need ALOT of gears on the peaky car.
However - can anyone really claim that a 2 litre turbo engine will be better than a 2.5? Assuming we're not talking about trying to rev to 10k...
/J
However - can anyone really claim that a 2 litre turbo engine will be better than a 2.5? Assuming we're not talking about trying to rev to 10k...
/J
21 November 2002, 06:06 PM
#56
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This thread started by questioning if it was it worth the hassle, expense and dubious reliability of fitting a 2.5 in an Impreza. When a 2.0 could be built which would push the car to the edge of its handling capabilities on the road.
21 November 2002, 06:20 PM
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A valid question...
At the same levels of power the 2.5 will spool up quicker, and give a more driveable "curve"....and no doubt be more reliable.
It'll cost you though.
I've gone the cheap way of adding go-fast-bits to the stock euro lump, and right now the car is too fast in the twisties for me (either it's fast, or I am a crap driver ).
I should be around 350 at the moment, with small, but expensive mods (link, md304, hks fmic, iON header, walbro pump - not exp, but needed).
However, I'd rather have this power in a well built 2.5, but I can't afford that.
/J
At the same levels of power the 2.5 will spool up quicker, and give a more driveable "curve"....and no doubt be more reliable.
It'll cost you though.
I've gone the cheap way of adding go-fast-bits to the stock euro lump, and right now the car is too fast in the twisties for me (either it's fast, or I am a crap driver
).I should be around 350 at the moment, with small, but expensive mods (link, md304, hks fmic, iON header, walbro pump - not exp, but needed).
However, I'd rather have this power in a well built 2.5, but I can't afford that.
/J
21 November 2002, 06:21 PM
#59
Been thinking....
So by running my 1.3 engine to 18000rpm, I can get very high power outputs, then all I have to do is run it through 12:1 diffs, and I'll be leaving all those lazy 2.5 engines in the dust.
I have sourced some titanium conrods already, about £1100 through Extreme (Ralliart), which is silly money. Titanium valves and springs, retainers, followers billet cams, the real deal. I have to get it all nitrided as titanium on titanium (cams/followers)bearing surfaces are not too good.
Reliner the block, with wire eroded Metal Matrix Composite (high Berylium content for added stiffness) liners, which I will get Nikasil coated and radation treated for maximum stability and lowest FMEP. Increase bore to maximise available valve size.
I was also considering running the 2.0 closed deck block and stroking down to about 48mm. This will make the crank extra strong, and further reduce rotational intertia.
Billet titanium crank, case hardened and Ti Nitrided, knifedged webs, combined with dry sump.
Alumnium flywheel (baseplate really) and a compacte muliplate clutch will keep inertia down to a minimum, which really works on a high revving engine. Torque requirements will not be great, as we all know, torque is not important when you have small engine size on your side
Paul
So by running my 1.3 engine to 18000rpm, I can get very high power outputs, then all I have to do is run it through 12:1 diffs, and I'll be leaving all those lazy 2.5 engines in the dust.
I have sourced some titanium conrods already, about £1100 through Extreme (Ralliart), which is silly money. Titanium valves and springs, retainers, followers billet cams, the real deal. I have to get it all nitrided as titanium on titanium (cams/followers)bearing surfaces are not too good.
Reliner the block, with wire eroded Metal Matrix Composite (high Berylium content for added stiffness) liners, which I will get Nikasil coated and radation treated for maximum stability and lowest FMEP. Increase bore to maximise available valve size.
I was also considering running the 2.0 closed deck block and stroking down to about 48mm. This will make the crank extra strong, and further reduce rotational intertia.
Billet titanium crank, case hardened and Ti Nitrided, knifedged webs, combined with dry sump.
Alumnium flywheel (baseplate really) and a compacte muliplate clutch will keep inertia down to a minimum, which really works on a high revving engine. Torque requirements will not be great, as we all know, torque is not important when you have small engine size on your side
Paul
21 November 2002, 06:23 PM
#60
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As Adam states, you could buy a small house for the price of a pukka 2.5 build !!! Or you could buy a dedicated track car and keep the subaru sensible ie 350 ish hmmmm !