325 vs. 328, is there a difference in reliability?

Are you looking at the E36 or E46 models?

ie. Older than 2000

The E36 series fits my budget a little better, so thats the most practical series for me to consider.

I owned a 97 E36 and except for a few oxygen sensors going out, the car was awesome.

Several of my friends have the E36, 325/328 and they noted few issues. The cars are built well with few electronic gadgets to go wrong as the car ages.

I would opt for the 328. I don't suspect there will be a huge cost difference between a 325 and 328 given the age of the vehicles.

It's the same engine. Both are damn near bullet-proof.

The 328 is used in the E36 cars after 1996, the 325 is used in cars before '96. The 328 gives 1 more HP, but has about 30% more torque, give or take a few foot pounds. The 328 is an OBD II engine, and you can pull trouble codes with readily available diagnostic equipment, the 325 is OBD I, and pulling codes requires equipment that costs much more.

I'd recommend getting the best condition car you can find, whether a 325 or

328, but the 328 would be the better choice if you can find a good one.

The 328 used in the E36 cars is also detuned and called a 323. I am not certain, but my guess is that an E46 car with a 328 or 325 motor is also the same power plant. The E36 cars use the M52 motor in the 328 and 323 applications, and the M50 motor in the 325 applications. I think the E46 cars use the M52, but I'm sure that if this is wrong, I'll be corrected soon.

You are correct, with the small correction that the M52 in the E46 cars was called the M52TU (Double VANOS). When the E46 got bumped to the 325 and 330 in 2001, the engine changed to the M54.

Kyle.

98 740iL 97 M3

So, the E46 started out with the M52 motors as the 328 and 323, and now gets the M54 motors, as the 330 and 325?

Actually - OBD-I codes can be retrieved with no equipment at all.. it's called the 5-stomp method. Turn the car to the run position without starting it - stomp the accelerator to the floor 5 times within 5 seconds. The codes will read out as the CEL flashes. Does in a sequence of flashes representing the numbers.

HTH

Yes, the M52TU had double VANOS on the original E46 cars. Basically the same engine as in the E36 except that one was single VANOS. When they got bumped up in 2001 to the 325 and 330 the engine changed to the M54, essentially the same engine. Not to be confused with the N54 in the E90 325 and 330 which is completely different. There was an article in Roundel a few months ago that detailed the evolution of the M20 engine that the M50, M52 and M54 were all based on.

Kyle.

98 740iL 97 M3

That's true, but OBD II simply plugs in, reads, then resets. No holding your tongue just right while stomping the gas pedal ...

You sure about those numbers? I find it hard to believe that a motor with only 12% more displacement could have 30% more torque, when they are of similar design.

Edmunds list the following....

95 325i HP 189 @ 5900 Torque 181 @ 4200

96 328i HP 190 @ 5300 Torque 207 @ 3950

My math (which is subject to correction) gets about 12.5% more torque at 250 RPM lower. I'm not certain, but I think I remember the torque band being wider on the 328 as well (starting to pull lower and continuing higher).

Kyle.

98 740iL 97 M3

Wild but true. Perhaps the torque numbers are only better by 27%, but that's close enough.

I want to be perfectly clear, the 328 does not have 30% more torque. The number is in that neighborhood, but I forget the precise number. I used "about" because I don't know the actual number. But it's a significant number.

I haven't done the math, but I suspect that 328 is not 12% greater than 325. I've done the math now, and I was right, 328 is not 12% greater than 325. It's actually less than 1%.

Well, I'm saying I don't believe it, without some evidence. The Greene's numbers make sense to me. Torque is very proportional to displacement.

Ummm, try 2.8/2.5, and I think you'll see the 12% displacement difference.

This makes sense, with the peak torques in ratio with the displacements. To get the same peak HP, the smaller motor has to be tuned to make it's best torque in a narrower range, higher in RPM's.

As it turns out, we're both wrong. The increased torque in the 328 isn't

27%, it's 27 ft pounds, or pound feet to be more correct.

I like Greene's numbers too.

By Greene's numbers: Displacement difference (rounded to 1/10 liter) is .3 liter, so .3/2.5 =

12.0% increase. Torque difference (207-181) is 26 lb. ft., so 26/181 = 14.4% increase.

Increase is measured as a percentage of the starting figures; that is the

2.5 liter engine.

Tom

Agreed. I originally said that the torque increase was 30%, it's really 30 ft lb, and it's actually 26 ft lb. Dizzy might have been more right than me, but you'll never hear me admitting that, therefore we're both wrong.