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So the red got to 200kph first... ?
 

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When I had my 3.6 on the rolling road (320.8 bhp) the operator commented that he often found the 3.6 to be producing more than the factory claimed, but had rarely seen a 3.8 produce more than 325? They certainly produce more torque but in a straight drag that appears less important than how brutal you're prepared to be with your clutch, gearbox etc

Mine is de-catted and nice and loose so mebbe that makes the difference?
 

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When I had my 3.6 on the rolling road (320.8 bhp) the operator commented that he often found the 3.6 to be producing more than the factory claimed, but had rarely seen a 3.8 produce more than 325? They certainly produce more torque but in a straight drag that appears less important than how brutal you're prepared to be with your clutch, gearbox etc

Mine is de-catted and nice and loose so mebbe that makes the difference?
Yes ,, i have heard ,, and we have been reading on many BMW forums exactly what you are telling

What surprice my most is that an individual coil @ each cylinder,, more cc ((200)) and larger ITB is not making anything in a positive progress
vs 3.6,, that runs a smaller diameter ITB.. .............DINASAUR type of ignition ,, the same as on M20 M30 and M70
B38 also use a newer version of TPS,,,

in my case .. my engine was extremely healthy IMO,, the HP was 306WHP but the grunt was 386NM WTQ i was running ALPHA-N when those numbers were measured
there is one and one 3.6 that really can do something,, and here in Iceland those owners that have driven and owned those cars agree that if the car is pushed hard the engine is working better,,
when driving a B36 vs B38 in normal traffic i will say that the grunt difference between these engines is quite a lot

But a friend of mine have a B38 with ALPHA-N and schrick cams,, and i can tell you that is the most powerful N/A IL6 i have ever driven
the engine was in an E34 oem 520 1995 but cluster.. instruments etc was converted + drivetrain,,,,,, unbeliveble fast B38
 

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I have a feeling that the B38 MAF being a film type is more prone to contamination longer term and that this degrades performance over time until cleaning or replacement.
 

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5.5 kg single mass flywheel and shorter stroke of 3.6 B36 goes some way to making them feel a touch more aggressive than the B38 .

D
 

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Sorry to drag OT but I can't send PM's yet-Davidoli, how much is the 5.5 KG flywheel, and do you have an estimate of what shipping to the states would be? Thank you.
 

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Sorry to drag OT but I can't send PM's yet-Davidoli, how much is the 5.5 KG flywheel, and do you have an estimate of what shipping to the states would be? Thank you.
Hi brian d , a standard 3.6 M5 single mass flywheel only weighs 5.5kg and can be fitted to a 3.8 M5 in conjunction with a sprung hub 3.6 clutch .

We can supply a chromoly billet 4.5 kg smf for £415 + shipping .

Email me at [email protected] to discuss options and details if required .

Regards,
David
 

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Ah, thanks for setting me straight on that David. I can't say it will be soon but I really like the idea of a lighter flywheel that isn't aluminum so I will keep this in mind.
 

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When I had my 3.6 on the rolling road (320.8 bhp) the operator commented that he often found the 3.6 to be producing more than the factory claimed, but had rarely seen a 3.8 produce more than 325? They certainly produce more torque but in a straight drag that appears less important than how brutal you're prepared to be with your clutch, gearbox etc

Mine is de-catted and nice and loose so mebbe that makes the difference?
The B38 is only a 7.4% larger engine and if you do the math from the B36 at torque peak: 356Nm @ 4750 RPM the B38 should be closer to 382Nm @ 4750 RPM (356 * 1.074) or only 26 Nm more torque and not the advertised 400Nm @ 4750 RPM.

So in a naturally aspirated engine, the basis for power comes from the cylinder/engine size (liters, CC, ci). The size defines the air-fuel charge that can be burned per engine revolution. Yep there are a few things that can be done to make an engine pump more air-fuel charge at a given RPM (torque peak) but it is with diminishing returns because if you move the pumping efficiency RPM the engines power will move with the pumping efficiency, that is: move it up to higher RPMs and there is less power at lower RPMs. The cams are the main component that establishes the pumping efficiency (Torque Peak) RPM and big cams typically make more power at higher RPMs by sacrificing power at the lower RPMs. Boosted intake is the only way to get both.
Note: the B36 & B38 both have a torque peak at 4750 RPM with near identical cams and cam timing as well as the intake tract.



7.4% is a small fraction and I anticipate a variance that could be easily lost in any car.

An engine only makes torque with Horse Power represented mathematically as (torque * RPM)/5252 = HP. HP is a good representation of how well the engine develops RPMs.
 

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B38 has larger valves and throttle bodies too. Also a better ignition system and higher flow cats. And a higher compression ratio, higher pressure fuel injection. There's more to power than cubes.
 

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The B38 is only a 7.4% larger engine and if you do the math from the B36 at torque peak: 356Nm @ 4750 RPM the B38 should be closer to 382Nm @ 4750 RPM (356 * 1.074) or only 26 Nm more torque and not the advertised 400Nm @ 4750 RPM.

So in a naturally aspirated engine, the basis for power comes from the cylinder/engine size (liters, CC, ci). The size defines the air-fuel charge that can be burned per engine revolution. Yep there are a few things that can be done to make an engine pump more air-fuel charge at a given RPM (torque peak) but it is with diminishing returns because if you move the pumping efficiency RPM the engines power will move with the pumping efficiency, that is: move it up to higher RPMs and there is less power at lower RPMs. The cams are the main component that establishes the pumping efficiency (Torque Peak) RPM and big cams typically make more power at higher RPMs by sacrificing power at the lower RPMs. Boosted intake is the only way to get both.
Note: the B36 & B38 both have a torque peak at 4750 RPM with near identical cams and cam timing as well as the intake tract.

7.4% is a small fraction and I anticipate a variance that could be easily lost in any car.

An engine only makes torque with Horse Power represented mathematically as (torque * RPM)/5252 = HP. HP is a good representation of how well the engine develops RPMs.
Just to elaborate a bit on the differences between the B38 and the B36.

- Intake wise you have larger throttle bodies at 50mm and associated velocity stacks.
- Increased intake and exhaust port and valve diameters.
- Improved head cooling through revised cooling passages and sodium filled exhaust valves.
- Added resonance flap switch point at 2480rpm to improve cylinder filling.
- Cams are the same PN between intake and exhaust and between the B36 and B38. The difference is in the lobe separation angle which is set by the cam gears. You get increased exhaust scavenging and fill for with the B38 gears and increased cylinder pressure which means increased efficiency and with it more torque.
- Increased compression ratio to 10.5:1.
- Improved fuel and spark control and with it improved efficiency.
- Higher flowing catalytic converters .
- Increased bore and stroke.
- Improved harmonic balancer mounting/retention.
- Resonance flap actuation controlled by the DME vs standalone controller in B36

Easy to see the little changes that added up to make more power and improved reliability.

As for the B38 tending to lose power more than the B36 I think a lot of that can be chalked up to neglected maintenance and any number of outside influences when being dynoed. My $.02.

-Greg
 

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B38 has larger valves and throttle bodies too. Also a better ignition system and higher flow cats. And a higher compression ratio, higher pressure fuel injection. There's more to power than cubes.
The higher fuel pressure is just to account for the things you and I both listed, it doesn't make more power necessarily it just gets more fuel into the chamber in the allotted time while using the same injector.

-Greg
 

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Having owned both (at the same time), i'd also say there's quite a noticeable difference between the 3.6 and 3.8. And that was with my 3.6 having 3.8 cam gears etc.

I think a big area of loss, as others have said, is in the mafs. Similar to the e39/S62. Drive an S62 with 50k miles on it's mass airflow sensor, then put a new set in and the improvement in power is huge. I wish we had a cheap option like we did with the S62 (using VW TDI mafs inserts)
 

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The higher fuel pressure is just to account for the things you and I both listed, it doesn't make more power necessarily it just gets more fuel into the chamber in the allotted time while using the same injector.

-Greg
True, but you also get better atomisation and therefore (hopefully) better combustion.
 

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Just to elaborate a bit on the differences between the B38 and the B36.

- Intake wise you have larger throttle bodies at 50mm and associated velocity stacks.
- Increased intake and exhaust port and valve diameters.
- Improved head cooling through revised cooling passages and sodium filled exhaust valves.
- Added resonance flap switch point at 2480rpm to improve cylinder filling.
- Cams are the same PN between intake and exhaust and between the B36 and B38. The difference is in the lobe separation angle which is set by the cam gears. You get increased exhaust scavenging and fill for with the B38 gears and increased cylinder pressure which means increased efficiency and with it more torque.
- Increased compression ratio to 10.5:1.
- Improved fuel and spark control and with it improved efficiency.
- Higher flowing catalytic converters .
- Increased bore and stroke.
- Improved harmonic balancer mounting/retention.
- Resonance flap actuation controlled by the DME vs standalone controller in B36

Easy to see the little changes that added up to make more power and improved reliability.

As for the B38 tending to lose power more than the B36 I think a lot of that can be chalked up to neglected maintenance and any number of outside influences when being dynoed. My $.02.

-Greg
What I am saying, is the difference between the B36 & B38 is small because the part of the power equation that makes a difference is the cubic centimeters, cubic inches, the engine size!!

That is there isn't enough difference between the throttle bodies, valves, cams, cam timing etc. to make much of a difference and I could produce similar torque/power to the rear wheels just by changing the drive train gearing.

Although the 3.91:1 diff ratio with the 5-speed is already pretty low if you want to cruse over 100 MPH for any distance. However the 6-speed provides more options for lowering the overall driveline gear ratios 1st thru 5th and still maintain the OD cruse RPM.


I've built a couple of engines that could make significant HP gains over the stock naturally aspirated engine and all I can say is a lot of cam duration, valve overlap, intake port/throttle body size, high-flow headers will reduce the low end torque for the gains at the higher RPM and IMHO it is a compromise that makes an engine useless for street drivability!!
I learned the hard way there is no substitute for cubic inches or forced induction!!!

Just a little light reading to get a pro's perspective:
Torque vs. Horsepower - Engine Power Delivery Explained - Hot Rod Magazine All Pages
 

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We'll have to differ on this one - the volumetric efficiency has a huge impact on cylinder charging and the utilisation of engine capacity.

My money is on some defect. I found one on my own 3.8L last night whilst installing the throttle bodies... the butterflies were over travelling (presumably from a lifetime of full pedal bending the plate that hits the stop). This reduces airflow before the TPS reads wide open.
 
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