Most power I can get from m20 2.5 NA?

[louis_monk]

I'm confident that this has been answered before, but how much can I get from an M20B25 NA? I don't need driveability. Just maximum power. I suppose reliability might be nice, but I don't mind high maintenance.

Anyone know?

Thanks!

[kam-325i]

Depends on how much you have to spend......

Money no issue = 250Bhp maybe

But i think 200Bhp is normaly the holy grail for a M20B25 N/A

[louis_monk]

thanks. Any idea's what needs to be done to get that sort of power. Heres what I can buy/get done easy.

6 branch
chip
K & N Panel filter
stainless exhaust
AGGRESSIVE cam (lol)
lightweight flywheel
porting and polishing
BBTB

What will that lot get me?

[Turbo-Brown]

Sorry to sound harsh dude, but you must be joking talking about getting serious power with that list of mods!

If you want lots more power, you need lots more revs and to get lots more revs, you need stronger bits like pistons, rods and beyond some point or other, a stronger crank!

Bigger valves wouldn't go amiss, head work from some one who knows what they're doing, not just a numpty with a flapwheel and a dremel, probably forget the original inlet system for throttle bodies, forget all about chipping and fit a mappable engine management system, uprate the ignition system....the list goes on!

You don't find 100bhp/litre on an old tech engine down the back of the sofa, it takes lots and lots of prep and lots and lots of money!

[Jon_Bmw]

Sorry to sound harsh dude, but you must be joking talking about getting serious power with that list of mods!

If you want lots more power, you need lots more revs and to get lots more revs, you need stronger bits like pistons, rods and beyond some point or other, a stronger crank!

Bigger valves wouldn't go amiss, head work from some one who knows what they're doing, not just a numpty with a flapwheel and a dremel, probably forget the original inlet system for throttle bodies, forget all about chipping and fit a mappable engine management system, uprate the ignition system....the list goes on!

You don't find 100bhp/litre on an old tech engine down the back of the sofa, it takes lots and lots of prep and lots and lots of money!

Agreed, you need in excess of 8k(and i don't mean revs) to get an m20 up to 250bhp, i think thats roughly what player6 spent iirc. Proper wonga. I would suggest other ways to get 250bhp much easlier, but you said you wanted in to be N/A

[louis_monk]

ok, I can see your point there. It is of course a fair one. But initially, for road use, how much power would that simple list give me? It would at least sound good with the six branch though huh? Lets be honest, it might be quite fun to drive, even if it isn't the fastest thing around!

Bolt on's and simple head work is my limit at the moment. I have to use the car as a daily driver you see

[louis_monk]

in the end I think I might do the obvious, and go M30! Much easier, even if it hasn't got truly ultimate power, it would at least have enough torque to make me smile! LOL

[Motorhole]

Forget the big bore throttle body and zone chip. Individual throttle bodies and standalone ECU is the way forward! Can be done for under 500 squid too using motorbike throttle bodies, megasquirt ECU, knowing a good machine shop and by getting your hands dirty.

[kam-325i]

thanks. Any idea's what needs to be done to get that sort of power. Heres what I can buy/get done easy.

6 branch
chip
K & N Panel filter
stainless exhaust
AGGRESSIVE cam (lol)
lightweight flywheel
porting and polishing
BBTB

What will that lot get me?

I would guesstimate around 180-190Bhp IF the engine was in very good condition to start with, And it does not matter if the exhaust system is stainless or not, stainless is only used because it does not rot as quick like mild steel....

[M5pilot]

190 BHP has already been achieved on Nadz325i's car.

Its got a BTB 6 branch manifold
Schrick 284/272 Cam
ITG Foam Filter
Standard exhaust (at the time)
Big Bore throttle Body

Unichip with Mass Air sensor conversion.

If a 288/288 cam were to have been used and the newer BTB manifold I think 200bhp + is easily achieveable.

200 BHP is not as hard as everyone makes it out to be as long as you start with a decent engine.

Dale also dide alot of tuning to his 325i - Throttle bodies, Alpina 6 branch, MBe standalone management, Schrick Cam,Scorpion exhaust - he got something like 196bhp.

[reggid]

i've never understood why you guys always use bhp when there is far too much error. What about good ol rwhp? saying someone makes 200bhp is garbage, what is the rwhp compared to stock? nobody on the planet actually knows what the driveline losses are and no dyno software is going to tell you either. Using 15, 17% is absolute BS. The variation bewteen the different dyno types can be huge not to mention the error on the operators part. So the only way to gauge is a before and after relative comparsion on the same dyno and operator of stock and after mods to minimise errors.

Back to the real subject, you would be doing well to make 120rwkw (160rwhp) with a M20B25. Its only a 12V head afterall. M3 make 100hp/L at >7500rpm 24V variable valve timing individual throttle bodies etc etc so you need all that stuff to break 190-200 rwhp with a 2.5. May as well do a stroker for actual usable gains at 1500-4000rpm not >5000rpm where the engine spends little time operating.

[Motorhole]

Back to the real subject, you would be doing well to make 120rwkw (160rwhp) with a M20B25. Its only a 12V head afterall. M3 make 100hp/L at >7500rpm 24V variable valve timing individual throttle bodies etc etc so you need all that stuff to break 190-200 rwhp with a 2.5. May as well do a stroker for actual usable gains at 1500-4000rpm not >5000rpm where the engine spends little time operating.

Not necessarily. Need to make the engine rev. Honda's S600 made a specific output of around 97bhp per litre from an 8v head as standard back in 1964. No reason why, with the right parts, an M20 can't be made to rev!

As for rwhp, I agree it is more representative and offers a greater indication of the effect of modifications. But as all manufacturers and journalists quote bhp, it is what most people are familier with. I guess that is why it is used...everybody knows the standard. Same reason I guess no-one uses the Si unit of Pascals for boost pressure!

[Turbo-Brown]

But then to take advantage of the extra revs, you need a cam that pushes power further up the rev range and that means it won't idle or drive well on part throttle so then you need throttle bodies.

[Motorhole]

...and programmable ECU! Throttle bodies are the only way to get enough air in quick enough for serious N/A power though...a big bore is only a halfway measure, and with the price of superbike throttle bodies from breakers being so reasonable there is no excuse!

[louis_monk]

how about M30 on TB's then? Any good? Has it been done?

[Kos]

back in the day BBR used to get 224hp from an 2.5 m20,

if you go for TB/carbs moster cam, mental head porting, and chuck Ԛ£3000 on internal to hold together over 250 is achivable. i once got hammered for giving out the above spec as some asked the same question.

but you dont seem to care about drivability!!!

it will cost in parts alone Ԛ£7-8 grand

[louis_monk]

so... is the general concensus that I should FI or maybe a totally different setup completely? I have a company car coming so I dont need a car that is 'smooth' LOL

[Kos]

FI is good, thats the name of the game on my m3, but i have an IS which loves to rev, i'd love to go slam in an S14, with cams and a super strong bottom end and have the best of both worlds but it comes down to Ԛ£Ã”šÃ‚£Ãƒ”šÃ‚£Ãƒ”šÃ‚£Ãƒ”šÃ‚£'s at the end of the day.

how deep is your pocket, and how far you want to go.

[reggid]

back in the day BBR used to get 224hp from an 2.5 m20,

if you go for TB/carbs moster cam, mental head porting, and chuck Ԛ£3000 on internal to hold together over 250 is achivable. i once got hammered for giving out the above spec as some asked the same question.

but you dont seem to care about drivability!!!

it will cost in parts alone Ԛ£7-8 grand

its not allways about making things "bigger" (although a bigger stroke would help) its about tuning the engine, where everything works together so you have to choose components that "work together". Race engines are not about making the cam and port sizes etc etc as big as physically possible.

[e21Jason]

Hi

At the end of the day the engine is just an air pump, all you can do is increase it's efficency to get the air in and out. 100BHP a litre is a good target for a tunned 2v motor, there is an approx calce based on valve area fro max BHP, I worked it out once for an m20 with 1mm over size valves and it was about 260BHP. In theory a 2v 6cly make more than a 2v 4cly for the same capacity due to biger valve area. Thats why BMW ran a 2.0l 6 cly in the world touting car series.

Jason

[M5pilot]

There are plenty of modified 2.5's on the zone, turn up to a meet and try them out before splashing out any money.

Nadz car is near 200bhp - drive it and see what you think

Drive Ant's turbo - you'll be impressed

Drive a few 2.7's - Simon13 has a C2 2.7 and I can bring my friends C2 2.7

Scott player has a genuine 250+ bhp M20 - but ive never seen him at a meet.

[Boots_Walker]

i would say 200bhp is a reasonable goal on a street motor whilst still maintaining driveability, should be achieveable with a 288 cam improved intake exhaust and engine management. starting with an early high compression motor will help...

250bhp is closer to the real limit, but you are basically talking a race spec motor (from memory some of the old 2.5 racers were making about 250bhp@7500rpm). not going to be cheap....

[bottlecapE30]

metric mechhanic builds a 240bhp NA 3.2l for $8995 plus $800 core charge they do very nice work i think my next motor will be from them.
www.metricmechanic.com

[reggid]

There are plenty of modified 2.5's on the zone, turn up to a meet and try them out before splashing out any money.

Nadz car is near 200bhp - drive it and see what you think

Drive Ant's turbo - you'll be impressed

Drive a few 2.7's - Simon13 has a C2 2.7 and I can bring my friends C2 2.7

Scott player has a genuine 250+ bhp M20 - but ive never seen him at a meet.

i would if i they were on the same continent....lol

i have been in a few worked 2.7 strokers and they are great there is no question about that!

how has his car been proven to be genuinely 250bhp ? where are the uncorrected/adjusted before and after plots?

Any good dyno operator will tell you that dynos are meant to be used as a tuning tool (i.e. before and after), not for someone to be able to say that my car absolutely makes xxx rwhp/bhp becasue they are not accurate enough when used in this way.

[M5pilot]

Dyno's arent super accurate but heres my experience when Ive taken cars dyno runs for diagnositic purposes on the same set of rollers.

325i Touring with INduction kit - 173 bhp
E34 M5 3.6 - 300bhp (stock 315) (170k engine)
E34 m5 3.8 - 330bhp (stock 340) (fuelling issues top end)
Alpina C2 2.7 (Not mine and 210 quoted) - 215bhp after light mods.

Figures are quite close to be honest so to some degree you can say I have XX power.

I personally believe it has 250 brake because its so damn bloody quick and also because after spending 8 odd grand on it it should give that much power!

Nadz 325i is having an upgrade this week so will update with the result.

[MaaasterBates]

£2500, 2-3 year old M54 3 litre from a smashed 330i, 231 bhp standard, will drive like a pussycat, do 30 plus MPG and will shit all over E30 M3's and any of that tuned M20 stuff. Plus it will do 150'000 miles.

The M20 was a very good engine.........15 -20 years ago. Anybody who pisses £2500 away on some old iron block relic from the seventies needs their arse kicking when there are so many decent alternatives. £350 buys you a complete nice running MOT failed 24v E34 525i from Ebay for f*cks sake with 192 bhp standard, so there's no excuse for the M20. Light mods yes, £8000 dollar boat anchors from the States no.

[Lordschleife]

In theory a 2v 6cly make more than a 2v 4cly for the same capacity due to biger valve area. Thats why BMW ran a 2.0l 6 cly in the world touting car series.

Jason

They've gone back to a 4-pot for this season (back to the old e30 m3 roots I hope )
Guess thats more from a handling/turn in point of view though

[tonyppe]

ok nice info there.

you lot use the 525e for the already 2.7 bottom correct?

if this is 2.7 std, why not bore it 90 thou? can it not be done due to wall thickness or something?

headwork headwork headwork. the best headwork around is a must. there is no point spending all that money on cams and throttle bodies if the pistons are sucking through a pin hole.

my 4-pot fiesta could get 3 fingers down the inlet. all the way to the valve.
the valves were pretty much touching.less gap than the side of a penny.
also doing stuff like match porting is a big yes yes.

[bottlecapE30]

£2500, 2-3 year old M54 3 litre from a smashed 330i, 231 bhp standard, will drive like a pussycat, do 30 plus MPG and will shit all over E30 M3's and any of that tuned M20 stuff. Plus it will do 150'000 miles.

The M20 was a very good engine.........15 -20 years ago. Anybody who pisses £2500 away on some old iron block relic from the seventies needs their arse kicking when there are so many decent alternatives. £350 buys you a complete nice running MOT failed 24v E34 525i from Ebay for f*cks sake with 192 bhp standard, so there's no excuse for the M20. Light mods yes, £8000 dollar boat anchors from the States no.

i was not showing this as if it was a good idea i was doing to show how much money would need to be spent to get that kind of power. to tell you the truth i have a e30 with a rough m30 in it and an e30 with a 2.7 stroker and the 2.7 is way lighter and easyer to toss around. I will agree if i had the money i would go with a m52.

[reggid]

some people don't want to swap an engine (why swap a 2.5 M52 when you already have a 2.5 M20 sure it has newer tech and all but so what its still only 2.5) and like the idea of the stock looking engine being "optimised". it is a challenge, even if the results are not huge hp. If pure hp is your goal then M20 is obviously not the right tool for the job but neither is the M52/54/30 or any BMW engine. FI is the only way and why stay with a BMW engine.

[Morat]

I've been having impure thoughts recently about a Fiat Coupe Turbo engine in an E30. It would probably annoy both E30 and Fiat Coupe enthusiasts, but both the 4 and 5 pot 2l Turbo engines are good strong units and make nice power (195 and 220 bhp). They also tune very well....

Just a thought

[tonyppe]

i sued to work along side a person called Barbs. he has his little place over croydon way. his car has been the quickest ive been in. it was 450hp. he also had nos. he managed low 12s at santa pod.
them engines sound quite nice too. the 5 pots are the better, the 20v. hard to work on tho. well, annoying anyway.

[Morat]

hehe, barbs is bit of a legend over on the Coupe forums
I have a 16VT coupe, and a 325i Touring. I love the handling of the BM and the power from the Fiat. Combining the two would be pretty awesome. 20V are definitely more modern and faster as stock, but the 16V integrale engine has a lot of tuning available...

And yes, everyone hates working on the coupe - just so tight under the bonnet

[tonyppe]

o right you know him then
you know them little turbo cones, in stainless... i spent a little while making them haha.
have you been in his car? absolutely mad stuff.
i took a customers 3000 gt out for a spin, he reckoned 690hp (i think his nuts were talking) even if he excagerated a little bit, barbs car was quicker. nothin like RW performance tho ay.

[Morat]

I've not met him in "Real Life" but I'd give a nut to drive his coupe