Engine swap or Charge?

[ss2115]

Dont' know if this will open a huge discussion or not, but I'm thinking my 525i Touring needs more power. Its adequate performance but at high petrol consumption, and I can't help thinking that if it was more powerful it probably won't be a huge change to consumption but a lot more pleasurable to drive.

So my question to this forum of experts - which would be better: a swap out of the 525 to a 535 motor, or bolt on a turbo or supercharger?

I suspect the charger route will be cheaper, but there is an attraction to have a 535 badge on the back and the increased torque and drivability that goes with it.
Will my 5 speed auto bolt up to a 535?
Is the cooling sufficient?

I have turbo'd a 1974 BMW 520i in the past myself (2002tii motor) as well as a 12A rotary and a Ford ghia 4.2 six cyl, and I've owned a couple of supercharged cars (2003 C200K being the most recent) which I further enhanced myself, so I'm familiar with the work involved and the results etc.
Loved all of them.

I'd be greatly interested in any similar experience of forum members as well as comments.

[shogun]

charger route will be definitely cheaper. For the M30 engine not much will fit in your engine room, that are (just what comes to my mind now)
-transmission, M30 engine has 4HP22
-drive shaft
-cooling system, including all the hoses
-probably the transmission cooling is different
-complete engine wire harness
-complete new TCU and MOTRONIC

[genphreak]

I have a Touring too. M50 has 141kW vs. 155kW for the M30. Not much difference, and you swap a little more torque for much better consumption with the M50. If you've got troubles chg the O2 sensor and add an EAT chip before you go for a heart transplant... the 5HP18 won't go, but if you chg to M30 you would surely go for manual trans at the same point? I'd be happy with a manual tranny on the M50 without even a chip.

Going M30 would be make sense with Forced Inducton- cheapest bang for the buck there would be to do it with a turbo a la e23 with a modern ECU.

[ss2115]

I have a Touring too. M50 has 141kW vs. 155kW for the M30. Not much difference, and you swap a little more torque for much better consumption with the M50. If you've got troubles chg the O2 sensor and add an EAT chip before you go for a heart transplant... the 5HP18 won't go, but if you chg to M30 you would surely go for manual trans at the same point? I'd be happy with a manual tranny on the M50 without even a chip.

Going M30 would be make sense with Forced Inducton- cheapest bang for the buck there would be to do it with a turbo a la e23 with a modern ECU.

I want to stay with the auto -I drive a fair bit and have another driver who can't drive manual.

What sort of pickup could I expect with a chip and perhaps exhaust modifications?

What other mods that aren't too radical can pick up an M50 motor before resorting to charging?

[Bruno]

Turbo is probably the way to go, or a V8 swap from a donor 540i.
The 535i will have more torque and more power, depending how much power you want at the end.

Do not go crazy on the boost as the automatic transmission will have its life shortened.
Best is 5 spd manual if you want to go turbo but you cannot go that route.

6-7 Psi boost, probably no need to intercool, good engine management, bigger fuel pump, bigger injectors, all the piping... Have fun

[ss2115]

Turbo is probably the way to go, or a V8 swap from a donor 540i.
The 535i will have more torque and more power, depending how much power you want at the end.

Do not go crazy on the boost as the automatic transmission will have its life shortened.
Best is 5 spd manual if you want to go turbo but you cannot go that route.

6-7 Psi boost, probably no need to intercool, good engine management, bigger fuel pump, bigger injectors, all the piping... Have fun

Was wondering on the strength of the M50 - bit worried about the headgasket as its seems to come up regularly in this forum as a problem.

On the 2002Tii motor I didn't decompress and ran the std compression ratio of 10.1:1 with a turbo limited to 6psi by wastegate. Got on to boost real quick.
Ran faultlessly for 4 years that way and I sold the car in good health.
Mechanical fuel injection though and higher grade leaded super petrol.

Tending to go supercharge these days because of the available torque off line and rarely able to use high speed/high horsepower on todays roads anyway.
Not a lot of room under the bonnet though.

[genphreak]

M50 is the best candidate for FI, M50B25 (non vanos I think) some have bottom ends that include M3 spec conrods and so on. A rebuilt ZF tranny will take the load, if you are really worried you can look up the differences between the 4HP22 behind the 745i or as used in Land Rovers, these can handle torque/weight combos that are in excess of what you'll be looking at. M50 will need a thickened copper gasket or new pistons. ARP bits are all available... so easy to do. M30 is cool as a sensible low pressure setup requires no bottom end mods at all. I'd start by megasqurting the existing M50, getting a new O2 sensor and see how that goes- then you can add turbo in your own time without any dramas on the electrical side.

You can get a lot the with a squirt once its wired in, but an EAT chip is a sensible basic change for those avoiding the hard work. A good tune and new O2 sensor would really 'liven it up' however maybe the tranny is slushy too. Tuning gains are more bottom feel of course, 5% power is probably the average improvement- tho each report different differences. Howerver a slushy tranny makes it feel like a dog off the mark...

Maybe look at rebuilding the tranny as an en initlal step, esp if you are going to keep it an auto!

[ss2115]

M50 is the best candidate for FI, M50B25 (non vanos I think) some have bottom ends that include M3 spec conrods and so on. A rebuilt ZF tranny will take the load, if you are really worried you can look up the differences between the 4HP22 behind the 745i or as used in Land Rovers, these can handle torque/weight combos that are in excess of what you'll be looking at. M50 will need a thickened copper gasket or new pistons. ARP bits are all available... so easy to do. M30 is cool as a sensible low pressure setup requires no bottom end mods at all. I'd start by megasqurting the existing M50, getting a new O2 sensor and see how that goes- then you can add turbo in your own time without any dramas on the electrical side.

You can get a lot the with a squirt once its wired in, but an EAT chip is a sensible basic change for those avoiding the hard work. A good tune and new O2 sensor would really 'liven it up' however maybe the tranny is slushy too. Tuning gains are more bottom feel of course, 5% power is probably the average improvement- tho each report different differences. Howerver a slushy tranny makes it feel like a dog off the mark...

Maybe look at rebuilding the tranny as an en initlal step, esp if you are going to keep it an auto!

Great insight - thanks.
Mine is indeed the M50 without Vanos. You've suggested decompressing with a thicker headgasket, but I was hoping to avoid that and just stay with a low max boost between 4 - 6psi.

I'm not worried about the transmission - everyone has told me mine is a very strong unit. Its not slushy on the changes, although for the first 5 minutes when its cold it tends to hang on to the gears. Most forum members have agreed that I probably only need to clean out the valve body to fix this. I can't find a auto dipstick so I must have the so called oil for life version (is this correct?)
Funny though because when I first got it I put it in for a service to fix this and they charged me for an oil change and filter service and there was no difference at all. Hmmmm!

You've also mentioned megasquirt.
I was wondering why as the engine already has a perfectly good injection system that is fairly easy to tune - adjustablefuel regulator, higher cc injectors etc.
Is it just for the adjustability your suggesting it?

I replacedthe O2 sensor early last year. Instant drop from 17 - 22 l/100k down to a more reasonable 14 - 17 l/100k, but I still think that can be improved on by a little more.
I was looking at the design 3 injectors, and then having had the experience that supercharging actually helps fuel consupmtion on light loads and shorter bursts of acceleration to get to speed, I started thinking along these lines again as per previous cars experience.

[genphreak]

I have the same thing happening when the tranny is cold. However more likely that it is at least partly by design- I find the changes it does are better described as 'low torque' changes rather than just high revs (but most are), so maybe this is to reduce wear when cold... so may not be 'blocked orifices'. But maybe some have it worse than others.

Missing dipstick does not mean lifetime fluid. Plate on the tranny is either green (lifetime) or black for Dexron II/Mercon. I use synthetic in the black plate 5HP18 and old 4HP22 without probs.

Motronic is not easy to tune; this is the only reason to dump a MAF based Motronic system really. It does not support FI (except at very low pressures), ie late 745 systems are highly modified and complex, even ignoring the AFM, megsquirt is a better solution.

Stock FPR is not manually adjustable remember- is it s standard RRFPR. Worth changing if economy is bad with no other reason. Larger injectors will get their cycles 'wound back' by Motronic once it works out what they do to combustion. Then they will become less efficient than the right sized ones, so are only worht doing if you've made serious mods that need the extra flow. But Motronic will flow more to them if the engine can use it but the fuel maps will be out. So again, better to go MegaSquirt if changing anything on the induction side.

14-17L/100 sounds fine around town for these heavy cars - fast highway drives should drop to well under 10 though. I've seen an M50 vanos sedan do under 8 over a 100km on high octane fuel.

For more info, search here for posts here by Jon K, he has put up a lot of details about charging his M50 amongst others. I can't imagine a non-factory superchager improving economy on a car... and is hardly the norm on factroy ones either- a turbos does that by design, but again, non-factory mods are sledom designed to 'return' more than power increases...

BTW, All M50 use 4-spot injectors, even the first low octane ones. 4-spot design III is no improvement over these. Make sure they are flowing properly tho, they can reduce economy a fair bit.