Arrrrgh!! Can nooooo make a decision nooooo!

[Gravy]

I had my heart firmly set on doing the 3.5 conversion to my M40 touring as some of you may have read, I got a 'box, and am/was looking for an engine..............but I am having second thoughts because in the back of my mind i'm thinking is it really worth the trade off in economy as I reckon i'd still be using the car fairly regularly - 12-15mpg doesn't fill me with joy!

It's doing my nut in because i'm on a budget, but I want the car to be swift, but mostly I want it to handle sweetly and put a grin on my face - but mpg figures do feature in my thought process too!

Obviosuly a whole range of conversions have been done here so I'd like to hear what people think is the best allrounder that I may want to consider, I've thought of M42 all the way to M62 but I have to remember about cost! - I'd do the 3.5 in an instant if I knew it was a car I'd use occasionly for Sunday blasts, but i'm thinking maybe a more modern approach is required?

I want the car to be a sleeper so it's not going to shout about what lies beneath, it will just have the right stance on regular 15" crosspokes!

Hit me with your ideas please,
Many thanks!

[fuzzy]

the trade off to going fast is burning more fuel,there is no other way.it depends what youd describe as a happy medium ,i dont even consider fuel economy

[Gravy]

Yeh that's fair mate, i would be happy with power on the right side of 200bhp which to you probably means slow looking at your sig!
But like you say i'm looking for a medium, anything to sling that M40 out and get some sort of respectable pace, but something that has the potentila to do around 30mpg when motorway cruising! I know its a tough one to call but I guess the E34 525i (M50?) would be sensible or the E36 328i (M52?) motor with a 325i manifold???

[Ant]

well, this is the FI section, so I suggest the following..........

Obtain merc SLK 230 kompressor or similar spec..
Fit above
using the cunning electronic clutch, supercharger on/off at will

Go when you want, slow when you dont

small T25 would be as good,

neither option is easy, but given the mixed requirements you've stated, manufacturers accross the world opted for smallish cc, boosted motors for best of both worlds.

Yes, I am biased

[Gravy]

Hehe, nice idea! Is that not a serious sum of wedge to do that? Plus I'd like to do the conversion myself as thats half the fun, and I don't have a clue about bolt-on stuff like that and its associated systems!

Plus, I'm a fan of N/A.................not that i'd ever discount FI!

[Ant]

Were doing an M40 turbo soon, I can change your mind

[stevetigger]

Were doing an M40 turbo soon, I can change your mind

You could of told me before I slapped in my M50.
My car would of been ideal with 74k and FBMWSH

[Gravy]

Hmmm M40 turbo ey! That sounds interesting, when are you hoping to have it "market ready?" and what sort of figures are you hoping to get?

I've been breaking the seven series this afternoon and the 3.5 is still at the front of my mind but anyone of you may swing me in a different direction!

I think the ultimate sleeper would be a Mutec, Dinan or some such tuning company chipped 3.0 diesel from an E46 dropped in the touring but I guess that would be a few years off due to cost of parts to do the conversion!........anyone care to tell me different?

[Turbo-Brown]

Turbo power rules!

The noise, the hand of God shove in the back, the stock(ish) economy when just tootling about, the puzzled looks on peoples faces when they hear a dump valve go pppppssssstttttttthhhhhh.

You know you wanna!

[tim_s]

Turbo power rules!

The noise, the hand of God shove in the back, the stock(ish) economy when just tootling about, the puzzled looks on peoples faces when they hear a dump valve go pppppssssstttttttthhhhhh.

You know you wanna!

so true! don't supercharged small CC cars still do fairly badly on fuel? a guy i used to work with had a mini cooper S and did pretty badly on fuel, and that was when driving in convoy with my IS (which did admirably I hasten to add!). how about the 323i M52, does pretty well on fuel and would certainly be quite pokey in an e30?

[Morat]

I think the problem is that they tend to run lower compression pistons so you don't get the same performance when pootling that you would without the turbo... so you're more likely to use the turbo...

Don't quote me!

[e30_Turbo]

I think the problem is that they tend to run lower compression pistons so you don't get the same performance when pootling that you would without the turbo... so you're more likely to use the turbo...

Don't quote me!

Why not run stock compression and a turbo??

The same N/a performance with a extra 100bhp added in at 3k, perfect

( or 250bhp @ 4k but that's just cos I'm silly )

[jaistanley]

Have you considered a 'tame' engine conversion?

I'm thinking M52B25 (323i engine) with inlet runners/plenum from an M50.

LOADS of torque and great motorway fuel economy (geared really high with a low final drive, reliant on torque).

Just an idea.

Jai

[tim_s]

Have you considered a 'tame' engine conversion?

I'm thinking M52B25 (323i engine) with inlet runners/plenum from an M50.

LOADS of torque and great motorway fuel economy (geared really high with a low final drive, reliant on torque).

Just an idea.

Jai

how about the 323i M52, does pretty well on fuel and would certainly be quite pokey in an e30?

great minds...

[Gravy]

Yeh guys I really like the sound of that conversion - I think I will do it...............after i've gone ahead and done the 3.5!!! I figure that if after its done that I really can't face the pumps as often as it looks like I might then I will either sell the whole car (don't want to though because it's mint)or convert again and sell the M30 bits as a conversion kit for someone else!

Also I'm looking out for an E30 for the missus in the next couple of months so maybe I could do the conversion to hers!

I'm sure I'll be loving the M30 effect on the touring to not really let the mpg get me down - plus my mate has an E34 535i sport auto that isn't running as sweet as it should and says that on a run he sees 25mpg, which I have no problem with! He did however say that giving it stick knocks that figure down to 7mpg!!!!

I am convincing myself that my car is way lighter than his, will have a manual box, will run as sweet as BMW intended it too, and will have a bag load of torque that I can use to waft along on the motorway and hopefully see sensible figures anyway!

Heres hoping

[bigdek]

on a motorway you might see 25 mpg.

but around town its usually between 15 - 20 mpg.

[Ant]

the 323 M52 2.5 engine will need the cams from an M50 single vanos to make it sing, the spec is very tame as std.

small engine , small turbo 6 psi with small intercooler will not hurt the mpg too bad if you can stay off the boost, and 40% torque increase throughout the lower ropm range

lots to be said for going FI, its not all about 300+ bhp and sub 5 seconds to 60

[lentec]

on a motorway you might see 25 mpg.

but around town its usually between 15 - 20 mpg.

On a run i get about 20mpg with the charger off!! Round town about 8 with charger on 13 off

[tylerma]

Were doing an M40 turbo soon, I can change your mind

sounds cool mate
when are you gonna be doing it

should be interesting

[Gravy]

dude where did you get that big pigeon avatar? well funny!

[tylerma]

dude where did you get that big pigeon avatar? well funny!

a friend sent it to me
its a clip from trigger happy tv

[Brianmoooore]

There's always the 3.5 conversion + LPG. Nice simple single point mixer system would work OK on that motor. You'd get about whatever the 3.5 normally does MPG wise, less about 20%, except that it won't drop as much as the petrol would when you push it hard.