Thinking ahead to my ideal Impreza and I'm dubious if a 2.5 conversion is the right way to go for a road car ?

A well tuned 2.0 with say 400 bhp will have a torque curve which is unlikely to overcome traction ie be driveable on our mixed surface roads.
A tuned 2.5 is going to break traction all the time and probably make slower progress in 90% of cases.
This will be made worse if the car is an Sti due to the rear bias for the power ie tail letting go every time you 'boot it'

For the majority of drivers (pro racers and ralliers excluded) a well tuned 2.0 with a non Sti 50:50 centre diff is going to be the best option IMHO.

Considering the costs involved in a 2.5 then would the thousands of ££££'s not be better spent on real upmarket suspension such as Ohlins or Proflex ? This would ensure that the power available can actually be used most of the time.

Sadly a 2.0 will be of little use to those wishing to win 'size matters' competitions at rolling roads etc but will it be the better option for the ultimate road car ???

 

Why not go for the 3.5 flat 6, twin turbo that Pat is considering

http://bbs.22b.com/ubb/Forum8/HTML/000405.html

 

Er... because I think a 2.0 will do a better job......... and I don't feel the need to show off the size of my 'equipment'

 

scoobee,

a 2.5 will only break traction if you map it that way.

bring ther boost in smoothly and it wont.

It also gives you much better low down torque if you want it.

Before considering any of this it might be worth researching some more.

the sti torque distriution is 50:50 like any other impreza as it has the same centre diff.

it is only the type r and type ra having the manually adjustable centre diff which ranges from 65:35 to 50:50, depending on degree of lock up.

And buy the way, a 2.5 costs more than a 2.09 because you have to buy the block. Apart from that all the costs are the same.

If you are going for 400bhp, you will be after a closed deck 2.0 anyway, so you will be buyign a new block as it is.

 

If anything, a 400bhp 2lt, will be less drivable than a bhp 2.2, or 2.5lt.

To get 400bhp out of a 2.lt, you will need a BIG turbo, lots of boost, and it will be laggy (relative).

A 2.5lt will make 400bhp easily, with LOADS of low down torque, as Adam has said.

Power delivery can be mapped to suit, but to be honest, I'd map it to produce the best power, at the boost you want to run, and use your RIGHT FOOT to control the delivery !

Which ever way you go, I'd be more worried about the clutch, and gearbox.

Other engine options would be a stroked 2.lt (2.122), or 2.2lt (2.33).

Mark.

 

But as already proven a 400BHP 2.0 litre does not need to run a lot of boost or be particularly laggy.

 

Harvey,

I did use the term "relative".

I think it's fair to say, that your car is somewhat laggier than it was with the previous turbo, and 1.6~1.7bar is quite a lot of boost.

Whilst I know there is more to come when Bob is able to spend more time on it, that "dustbin" of yours, AKA a turbo, will always be quite laggy on a 2.lt.

But, put it on a 2.5lt, and run it to get the same 417bhp, and it would be a different story !!!! By "comparison" it would be a beast.

Mark.

 

If you already have a closed block 2.0 then 400bhp can be on tap for not a lot of £££££'s and not a lot of lag Not sure you even need closed deck at 400 ??
All IMO of course

 

OK. So before we had 1 bar at 3.3k and now it is at 3.7k so it is a little laggier. However this is an interim map and it did 417 bhp at 23 psi and will run at 26/28psi (1.8-1.9bar) Also remember the previous run was 424 BHP.
The car is very tractable pulling in 5th from 1700rpm if you wish, without complaint and remember this is on 3.9 diffs and not the original 4.44:1 so overall I am very, very happy.

 

Harvey,

Please remember I am talking in "comparative" terms.

What would be interesting, would be to compare your current, and previous WL graphs. Overlaid, it would show the comparative differences between the two turbo's, even taking into account the increased boost you are running.

Mark.

 

the pundits all have views on this but as far as i can tell there is only one person with a 400+ bhp impreza on this board!

and that is a 2.0 not a 2.5

maybe the so called experts need a re-think/re-bore!

mark- what bhp is your car running by the way???

 

Nos there are quite a few 400plus bhp cars here.

Have you not seen Christians 2.5 conversion?

Plus there are others, but they do not wish to publish what they produce

Honest guv

Chris

 

LOL

 

just read pats tread is he serious??!! or just mad? 1000bhp
who needs a skyline

 

ain't no substitue for cubes

EG, Audi RS6, 4L+ V8 twin turbo, 430hp, no lag, super broad torque curve.

Case closed

 

Pat is a lunatic.

Have been warned about him from Mark & his menatl ideas

I though I had some mad ones

Still a bloody good source of knowledge & a thank you for him helping me out a while ago

Chris

 

Well, a fair bit of pro 2.5 feedback then ! I presume you guys are running 2.2/2.3 or 2.5 engines ?

Are these conversions reliable ? What sort of mileage have you put on them ? How does the cost of a 400bhp 2.0 stack up against a 400bhp 2.5 ?

Sorry, lots of questions !

 

none of the 2.2 2.3 or 2.5 engines have been proven to produce over 400bhp here in the uk yet so they won't be able to answer that!

 

Nova boy,

I take it the 2.5L cars in the US and Australia that have a proven 600hp and run 9 or 10 second quarters would do better with 2.0 litre engines?

Yeah, right.

Paul

 

All of the engine conversions mentioned here, are common place in Aus', and if built correctly, without pushing it too far, will be reliable. However, ANY engine that is HIGHLY tuned, is unlikely to last as long as a stock powered engine.

For stroked 2.lt (2.122cc) the only difference in costs, would be an EJ25 crank (circa £425) and the cost of a good second hand closed deck block.

A closed deck stroked 2.2lt (2.33lt) would add circa, another £400 to the above.

For a 2.5lt, it would depend on how much power you wanted. EJ25's only come as "open deck blocks", so this needs to be addressed. There are two ways of doing this, one "reasonably" priced, the other, very expensive, but only really necessary for 450bhp +

The "up side" of starting with another block/crank, is that you would end up with your own short block, that you could either keep, or sell.

The heads, inlet manifold, and ancillaries will just swap over.

For 400bhp, you would need to get a bigger turbo, and injectors anyway, and it would also be worth porting/flowing the heads, and re-profiled cams.

As I said earlier, the main concern would be the gearbox. any of these conversions are "capable" of 400ftlbs of torque +, and the stock box isn't up to it. Not for long, anyway !!

Mark.

 

Just to add a 400bhp 2ltr will be putting out 200bhp/ltr (no **** sherlock), the 2.5 will be 160/ltr. Sorry for stating the obvious but that is a big difference.

I think Mark appears to have covered everything else

 

Harvey,

I am still very interested in your power output. I think the results are fantastic!

Have you posted a graph before?

I dont know much about the history of your project, but am wondering if you can post a before and after graph, since I assume the big power came from a big turbo, I wanted o see how it delivered its power.

If you cant provide a graph, can you just tell me what power the car is putting out at 5252rpm? I find this gives a good inddication of the performance of the car on the road.

Thanks in advance.


Ps. I am one of the 2.5 boys with no power outputs as of yet so to speak. I assure those who doubt, there are others out there who have more than 400bhp already tested by reliable methods.

We wont even talk about pats plans.

My engine has not produced any numbers because it has not been built yet. I am waiting for parts and ddnt want to throw it together in a urry only to have it "expire" when attempting to extract over 550lbft.

It has been off the road a year so far, which is very frustrating when it is your pride and joy, but there is nothing I can do to get the bits to be made faster.

Needless to say, if security is not an issue, I will fill you all in when it has been on the engine dyno!

I have a thing against coming on and sayng, "hey everybody, look at me!" I find it a little arrogant. (nothing against harvey, as someone else posted his results for him.

 

Thanks for that Mark. Certainly the laws of diminishing returns applies here. So ballpark figures (including supporting mods such as gearbox etc) say 350 bhp for £2k. 400bhp for £4k. 450bhp for £10k. 500+bhp for £15-20k !!!!

Perhaps it's just me ?? but I like to read about other peoples results. These after all are proven results for x,y,z mods.

I'm sure many others have found it interesting to follow the different methods involved and monitor the BHP progress of D Wallis, J Banks, Andy F, P20SPD, Harvey and many more.

The approach I find a shade arrogant is the 'I know sombody with more power than Mr x' or 'I'm going to have more power than Mr x'
Perhaps it's not arrogance after all, just envy !!

 

envy?

nah.

I am envious of those with standard 22Bs, who havent wasted a year of ownership driving a pug 205, because their dream of a 500bhp 22B has forced them to make sure everything is perfect, and in the process wasted around the cost of a small house (in the middle of nowhere), all to attain a car that in reality was probably fast enough before, and will end up undrivably fast and most likely unreliable.

[Edited by Adam M - 11/21/2002 1:32:49 PM]

 

Adam

Quote >>> "will end up undrivably fast and most likely unreliable."

Are you suggesting that a mild tune, say 350bhp 2.0 (or 2.2 in your case) is likely to give as much enjoyment ?

 

actually its 2.5 in my case.

I am saying that in hindsight, it would have been better for me to just strengthen the 2.2 (since I had it), and put it back in without making lots of other serious changes, and replace things like the gearbox as and when necessary.

instead I have done EVERYTHING all in one go, crippled myself financially, lost the car for a year, and removed all the fun of doing it in stages.

 

2.5 I say! Ever seen Toni Rigoli car????? Serious amount of power, qurte mile (if memory serves) was done in 10.something @ 142mph.
All good fun ehh?

Cheers

Gez.

 

NOS NOVA....

We've done this argument so many times...

as I've said before ask and all will be revealed... just not in public... Harvey is well aware of the spec of cars that run alot more power than his in the uk.. im sure he will agree..

I have more torque than harvey

Harveys engine will probably last longer than mine though

Lets just say theres lots more to come from the likes of me and AndyF.

500 here I come (on a budget)

David

 

pavlo-Not at all.
Just looks to me that Australians know how to build and fit 2.5 engines because where are the reliable UK engines at that size?

C. Yes. I know that Christian's car did 359 bhp at Well Lane and came second behind Steve McCulloch's 2.0 litre. Car probs stopped him coming next time so that kind of adds to the reliability issues. Are you telling us it has proven more than 359 bhp. Let us stick to the facts. It is one thing having an engine with potential and another having it fully sorted and running reliably.

The only other high profile 2.5 that comes to mind is R19KET. I have no idea if it has been on the rollers but it was not running properly at Elvington and I think Mark had some bad luck with it and it has been in bits since.

Sort of shows up the lack of ability to produce reliable 2.5's in the UK.
The 2litre route is tried and tested and probably less costly but if you were going for ultimate power then 2.5 would be the way to go but it would need to be done properly right from the start and not many are actally capable of that which is already proven IN THE UK.

NOS

 

NOS,

just because something isnt done in public, does not mean it isnt done.

Not everyone likes to tell everyone about their projects for various reasons.

as I said above, i have a 2.5 on the way. Not making any claims about mine is better than his etc, as I dont give a damn. It simply isnt ready yet, has not been built, fired, dynoed etc.

Simply because the bits arent together yet.

That is me done,

there are others who have theirs up and running. There are a few people making good power.

Christians is just one. His power figure you saw was from runing 1 bar with an intake pipe that was closing in on itself.

It isnt doing that now, it is running daily, and working fine. I am even confident it is making over 400bhp. It just hasnt been on the rollers yet.

You also have to forget about the rollers being the be all and end all because they arent.

Only accurate way to gauge power is on a bench dyno.

You also need to look at the WHOLE GRAPH and not just the peak.

it is the shape of the graph that will indicate the speed of the car, not the peak figure.

eg. consider that david wallis has more torque than harvey.