[Tom Droze]

I had my automatic 328i (e92, N51) weighed today with me in the car and a full tank of gas, and it topped the scale at 3580 pounds. Fully clothed I weigh 165 pounds. Based on my 93.00 MPH trap speed from last Friday's drag racing, the calculated RWH is 225 and the horsepower at the crank is estimated at 273. For comparison purposes, I peaked at 188 horsepower on the dyno! Because my 1/4 trap speed and the weight of the car are real world, I'm inclined to trust this data over the dyno data.

As a refresher my car has the following: N51 (which has the 3-stage intake manifold), Dinan ram air, charcoal delete, intake scoops, silicon intake tube, the BMW performance exhaust, and the stock tune.

I had my car weighed on a certified truck scale, which gets recertified every two weeks.

[Taskmaster]

I always figured the coupes to be lighter than sedans. Hmm...

[hassmaschine]

273 at the crank with the stock tune? I find that pretty tough to swallow despite your trap speed.

what kind of dyno were you on? everyone likes to use really high drivetrain losses too, 225whp is believable sorta but I don't buy into 18-20% drivetrain losses in a modern BMW.

in the end, I guess all that matters is how fast the car actually is.

[zhp43867]

The E90 328i got a 96mph stock trap speed (via Car and Driver) At 3352lbs. What would it's calculated horsepower be based on that?

I think your dyno data is better than your calculation.

[E46driver]

What options do you have?

[Taskmaster]

He's an Auto RWD. His actual dyno numbers seem more accurate when gearing it taken into account.

[Tom Droze]

Originally Posted by hassmaschine

273 at the crank with the stock tune? I find that pretty tough to swallow despite your trap speed.

what kind of dyno were you on? everyone likes to use really high drivetrain losses too, 225whp is believable sorta but I don't buy into 18-20% drivetrain losses in a modern BMW.

in the end, I guess all that matters is how fast the car actually is.

Dynojet, I made six passes and five of the six trap speeds were 92.XX with the fastest being 93.00; so there was less than 1 MPH variation amongst the six runs.

Even though the N51 and the N52 are rated the same at 230 horsepower, I have a suspicion that the N51 with the 3-stage intake manifold (but with lower compression 10.0 /1 compared to 10.7 / 1) makes more power than the N52 in a stock configuration. Also, I have the Dinan ram air intake and the intake scoops, both of which are useless mods on a dyno because there is no significant air flow.

[Tom Droze]

Originally Posted by zhp43867

The E90 328i got a 96mph stock trap speed (via Car and Driver) At 3352lbs. What would it's calculated horsepower be based on that?

I think your dyno data is better than your calculation.

231.5 horsepower

http://www.ajdesigner.com/fl_horsepo...trap_speed.php

[Tom Droze]

Originally Posted by E46driver

What options do you have?

Base model with a sun roof.

[Taskmaster]

Originally Posted by Tom Droze

Dynojet, I made six passes and five of the six trap speeds were 92.XX with the fastest being 93.00; so there was less than 1 MPH variation amongst the six runs.

Even though the N51 and the N52 are rated the same at 230 horsepower, I have a suspicion that the N51 with the 3-stage intake manifold (but with lower compression 10.0 /1 compared to 10.7 / 1) makes more power than the N52 in a stock configuration. Also, I have the Dinan ram air intake and the intake scoops, both of which are useless mods on a dyno because there is no significant air flow.

I'm going to disgree with this, maybe more torque, but at peak it's about the same. The real news is the automatic/coupes more aggressive gearing that allows you to multiply torque and maximizing the power you already have. I bet the Dinan/Scoops help too.

Remember, our 1/4mile numbers are pretty much the same all the way up through the 1/8 mile and then you outtrap me by almost 3mph...

[Tom Droze]

TheAxiom,

You know what the difference is, it's my Sprint. Booster, I forgot about my Sprint Booster! ;-)

[Taskmaster]

Originally Posted by Tom Droze

TheAxiom,

You know what the difference is, it's my Sprint. Booster, I forgot about my Sprint Booster! ;-)

[jc5988]

Originally Posted by Tom Droze

Dynojet, I made six passes and five of the six trap speeds were 92.XX with the fastest being 93.00; so there was less than 1 MPH variation amongst the six runs.

Even though the N51 and the N52 are rated the same at 230 horsepower, I have a suspicion that the N51 with the 3-stage intake manifold (but with lower compression 10.0 /1 compared to 10.7 / 1) makes more power than the N52 in a stock configuration. Also, I have the Dinan ram air intake and the intake scoops, both of which are useless mods on a dyno because there is no significant air flow.

you should really be running with some tune, stock n51 is "detuned" to match N52 328's power. also you should only be about 235-240hp at crank with the mod you got. with tune and secondary delete will net you 250-255hp. PE does nothing on HP, intake will get you that 5-8hp.

compression wise N52 will net about 5-7 more hp, N51 not only has less compression but also more restrictive cat. header and secondary mod will net more on N51 then N52.