Z4 E85 N52B25 performance upgrade

[Ducklakeview]

And if we are being pedantic, the figure is 5,252

Mike

Why should the lines on that dynosheet cross at 5252rpm? (or 5250rpm for that matter)

Due to the fact that a dyno measures torque. It then uses a formula to calculate the horsepower, this is done by multiplying torque by rpm/5,252 hence the 5252rpm figure that people quote. However as the torque and horsepower are usually different at each RPM, the scale itself is altered to fit them both into a viewable window. It also measures "reverse" torque on rundown, ie transmission drag, and compensates for this.

Mike

[Scarp]

The wheel horse power is less but every car producer etc writes engine power not wheel hp if its like that the car whold have stock what 130 whp ?

[jamie_z4]

latest.jpg (75.65 KiB) Viewed 945 times

[Ducklakeview]

Here's one for all those technically minded peeps, and sorry for jumping off topic OP, but it only occurred to me a few days ago..

Say a car has an engine producing 100bhp, driving the rear wheels via a gearbox, that in top gear has a 1:1 ratio (still following me?)

Well, assuming that at the prop, there is 100bhp, less a few for transmission losses, then it goes through a diff, with for example a 3.46:1 ratio? Why then, is the torque and power not INCREASED by this reduction gearing??

Riddle me that....

Mike

[GuidoK]

Due to the fact that a dyno measures torque. It then uses a formula to calculate the horsepower, this is done by multiplying torque by rpm/5,252 hence the 5252rpm figure that people quote.

This is not true for this dynosheet. (and thats the point I'm trying to make)

And a dynometer doesnt only measure torque, it measures torque (or some derivative of that) and rpm (or some derivative of that) at the same time.

[Scarp]

Thanks for the great advice to the first post and topic itself

[GuidoK]

Have you ever measured 100-200 with a 10hz gps? (your video is a bit dodgy for that, but by the looks of it its a decent match for a stock m54b30 I think).

In the end the proof of the pudding is in the eating. Acceleration in real life

[Scarp]

No I dont measure like this I have the car 4fun the video is made with the roof down every roadster owner should try to 250 km/h with the roof down it makes a hell of a difference after the video I had a street race with an X6 4,0d and he had no chance ( I know X 6 with the weight and tyre size is an elephant on the road) but the power it has more I dont think a stock 180 HP car can do 250 km/h with the roof down

[GuidoK]

I dont know if roof up and down makes that much of a difference.
When my car was still stock it could reach 250 and run into the limiter with both top up and down.
Now that it runs a bit faster I dont try that anymore, just too afraid that something will break.

But your acceleration video sure shows more than 180hp. But did you start with a facelift 2.5i or 2.5si (thas quite a difference, 40hp or so.)

[Scarp]

the E85 has only 2,5i 2,5 Si belongs to the E89 in stock it was 130kw .

And these videos dont tell anything they are just 4fun . The weight of the cables big battery sobwoofers instalation in the trunk amp makes a big difference . Big brakes I can see their wight in drag races but I dont care. And yes the roof down makes a difference 2l fuel consumption when the roof is down tells something about the aerodynamics buts its a roadster it must have the roof down

[Ducklakeview]

Due to the fact that a dyno measures torque. It then uses a formula to calculate the horsepower, this is done by multiplying torque by rpm/5,252 hence the 5252rpm figure that people quote.

This is not true for this dynosheet. (and thats the point I'm trying to make)

And a dynometer doesnt only measure torque, it measures torque (or some derivative of that) and rpm (or some derivative of that) at the same time.

Would have thought anyone reading would realise that it also measures RPM, given that it needs that information in order to calculate horsepower...

Mike

[Steve84N]

I can't read the language but it looks like wheel horsepower is 184 which has then then been translated to 255 at the crank which assumes a ridiculous amount of losses. Assuming 15% losses it would actually be more like 215 which seems about right...

NB: Dynos read wheel horsepower so crank figures are always going to be guestimates. I wish everybody just quoted wheel as it's far more relevant.

Dynos actually read torque, not horsepower... The latter is calculated from the torque and rpm figures.

Mike

I was aware of that so strictly speaking it was not an entirely accurate statement but you glossed over the important part. The crank figure quoted is assuming over 36% drivetrain losses and you don't even get that with 4WD.

[Scarp]

I am not a break technician but I learned a lot with the last measurnemt it really matters if you measure on 4-5-6 Gear . On every yer he had to make the RPM settings and then run the measurment. The higher the gear the lower the power

[GuidoK]

the E85 has only 2,5i 2,5 Si belongs to the E89 in stock it was 130kw .

No, the e85 was delivered in both 2.5i and 2.5si power outputs., so both with 177hp and 218hp.
If you post the last 7 digits of your vin I can immediately see which version you had when it came out of the factory.

Afaik the E89 was only delivered as a 23i with the 2.5 n52, and that had 204hp.

[Smartbear]

the E85 has only 2,5i 2,5 Si belongs to the E89 in stock it was 130kw .

No, the e85 was delivered in both 2.5i and 2.5si power outputs., so both with 177hp and 218hp.
If you post the last 7 digits of your vin I can immediately see which version you had when it came out of the factory.

Afaik the E89 was only delivered as a 23i with the 2.5 n52, and that had 204hp.

The si engine in the e85 was also an n52 engine, as far as I know the lower output for the e89 variant was due to emissions regs
Rob