in the M50 family of engines (and M60 also actually) OBD1 intake manifold is 40% larger flow volume, the early 92-95 model year engines have this manifold.
OBd2 intake manifold is revised for more low/mid power, it is to suit the later model (heavier body cars).
This is a style of tuning BMW and other engine builders employ to make a powerplant wider fit a range of chassis.
many people install M50 manifold on M52 and S52 here, I installed it on my S52 (M3 E36 USA).
you can reference dyno charts for this modification, many online and on TRM/Miller/shark injector etc websites. ECU chip tuning is suggested to make up for the difference in runner sizing, torque band is mechanically shifting up to suit the Horsepower equation when you change the runners from smaller->bigger style
comparing a factory spec e36 325 vs the 328i
gearbox ratios are both "close" ratio, 1:1 5th gear.
1st gear for g250 is 4.23, 1st in ZF SG320 is 4.2 - pretty much the same.
Tire size OEM spec for 325 is also smaller, usually 15" or 16" rims.
328 oem spec is 16" rims and for M-package 17" rims. These are a bit bigger diameter and heavier due to wider rubbers, wider 7.5/8.5J staggered rims.
heavier larger wheels = more difficult to move from standing.
325 final drive: 3.15
328 final drive: 2.93
- from this you can see that the larger displacement engine (300cc+) has a lower final drive ratio. It makes more torque so can push the taller gear
325 has 3.15 (easier to spin) ratio final drive to move car from standing (with 300cc less torque).
IF one was to use the M50 manifold on the 328 chassis car, the mechanical tune of M50 inlet will inevitably shift torque towards the higher RPM's (that is why you gain horsepower, as horsepower is created by holding torque above the 5252rpm constant in the math equation.
comparing the factory equipped 2 cars, the heavier equipped, larger engine, larger wheels taller gearing car would be at slight disadvantage if toque is lost on lower end. Harder to move it from stop, as its not OEM setup that way.
What is the best tuning solution if you would like to gain ~ 10-15hp on higher rpm 4500-7000 rpm zone?
1. M50 manifold
2. your choice of chip
3. 3.15 final drive swap to increase mechanical torque (to offset lost low range RPM engine torque)
*** if you plan on fitting 18" or larger rims with bigger rubber, you can consider a 3.23, 3.38, 3.46 final drive ratio- the rims increased diameter and extra tire weight will catch up...
Automatic 328i should have a 3.91 final drive, if you do not change this the engine rpm's @ expressway speed will be ridiculous (and poor fuel consumption). But very rapid acceleration like a rally car!. You would also do peg leg burnout everywhere (as automatic 328's do not have LSD spec'ed standard from factory)
If feel like leaving the 3.91 final drive alone, then you need to fit a 6 speed transmission (.83 overdrive); it matches the 3.91 very nice for sport use actually.
clovi5;659694 said:
Wow that is very educational. Thank you very much. I don't think I'm going to do much on the car. Just a manual conversion (a must!!) and probably some mod on the intake manifold (m50).
Though after I saw on Apiz's post the reason why M52 engine has smaller diameter than m50 is because they wanted to choke the air flow so that it improves the torque at lower rpm.
So I'm wondering whether any of the sifus here with M52b28 modded with m50 intake manifold dyno-ed their car recently? How is the torque rating at about 3-4k RPM?
