2.5 N/A, what to expect?

[malfunkshun]

Let's say that I was to build a N/A racing engine based on a 2.5L block using a 7a head. What kind of power would it deliver (no fantasy numbers please) with the following setup:
Dry sump
Balancing the crank.
Lighter con rods (as light as possible without compromising the strength)
Lighter pistons (F1 style or similar=light)
Mechanical lifters
Better suited camshafts
Lighter valves
ITB with injectors mounted F1 style
A good tuned exhaust
A silly high comp. ratio
And all this running on E85.

My goal is around 250bhp, at lest, trying to be realistic.
An engine with this spec. has been a dream of mine for quite some time.
Any issues, comments and suggestions you may have about my thought and dreams are welcome.

[s2 on the way]

for 1/3rd of the price you could have a more reliable turbo setup with much more power.
I've even heard of people dialing their em runner lengths to the turbo in the ideal manner as to make some sort of f1 sound out of it if that's what you're after.
although the sound of a na 20v at high revs without the restriction of the turbo is amazing (or would be amazing)

[magarv]

It realy depends on wich Tuner you choose, but I know there has been built 2,1L NA cossie engines with 286bhp and same tuner is now building 2,5L cossie engine with estimated power level of 310-320bhp. All figures on 98okt

So with a extreme race engine setup as you describes, I cant see 300bhp as a problem (if the right parts and right tuner is choosen.)

[Puglife]

I know of plenty of N/A 4cylinder 1.9/2.0l engines making 300bhp+ some are obviously easier to tune but audi engine can respond well. I'd say 250bhp would be a very good low end power output for a well built engine... anything up from that really would be down to tuning methods and the limitations of the engine...

[stiglet]

With a high compression ratio and E85, yes definately. Raise the rev limit and you could acheive more. Look over at motorgeeks.com, a few guys there have got similiar results on NA setups.

You can get higher displacement than 2.5 too.

[GazzaG60]

to get hp you need to rev.

the power on a na engine is finite. what you are doing is moving the power up the range to get high hp figures.

extreme port, solid lifter, cams, pistons, rods, crank weight reduction just to start. super high compression is needed which gives a fine line when tuning.

[S2central.net]

100bhp per liter should be easy on any modern N/A engine...

With good attention to detail and all the mods that can make the engine spin faster and intake more air (providing fuel for that is easier without turbos involved) you could get into 125bhp per liter territory. Maybe more actually when E85 is factored in - need to be careful on how the thing is setup on camshafts and such for usable torque in the mid range... depends on the racing application you have in mind.

But you might need to trade off some ultimate peak power for a wider torque band. I'd say adjustable camshafts are your friend here.

[stiglet]

You don't need "super" high compression. As mentioned, 100bhp/litre is not hard. All it needs is a little fettling, with maybe 11:1 comp and a slightly higher rev limit and you could reach your target.

[goodall]

with the itb's and exhaust with the stroker and cams you could probably make 250 on super unleaded and standard compression (allow youll have tune the comp anyway since using diesel block ete) and without port polish job

[GazzaG60]

show me some evidence of 250+ NA without ported head and solid lifter.

300hp engines are revving to 9k plus. thats solid lifter land. so solid lifter cams are needed too. to get the engine to drag in enough air higher compression is needed along with a good header.

if it was a honda then yes as the head design is streets ahead but an old 4v vag head i doubt.

big hp NA engines that are low displacement are crap low down. mid range is going down thats for sure. he wants at least 250hp. you would be able to keep some midrange at 200hp but not at 250+

[stiglet]

Search on Motorgeeks, there are projects on there similiar to this. You're right, it won't be driveable BUT for racing application it is perfect.

With ITBs 250 is well within reach.

[GazzaG60]

it would need throttle bodies thats for sure. id expect 48mm ones too.

finding a place to pick up map signals can be a pain.

if its what you really want then go for it. it will id expect be a pig unless up and down the gears at 6k plus and on the track. homefry s2's will more than likely leave you for dead.

hard to beat the throttle response of itb's on a high comression NA though.

[Sonic]

100bhp per liter should be easy on any modern N/A engine...

Bring on the 120hp modifications to my Renault Clio 1.2 16v

[stiglet]

Exactly. No turbo means no lag and much better response. In a straight line a homefried S2 would be far superior. NA is just better suited for a track.

I guess it' s amatter of opinion though. You can't beat the torque of a turbo, but it has drawbacks. Seen this discussion a million times on here before!

[Acidburn]

Exactly. No turbo means no lag and much better response. In a straight line a homefried S2 would be far superior. NA is just better suited for a track.

I guess it' s amatter of opinion though. You can't beat the torque of a turbo, but it has drawbacks. Seen this discussion a million times on here before!

after seeing you keep up with most cars around the track think yours works better at the high rev's you run it at.

any progress with your engine?