JB4 + catless DP's: Report back on gains with Dyno

[thedoctor]

Here are the gains i was able to achieve with JB4 and custom catless DownPipes...

+ 42 kw's (56 hp) at the wheels
+ 107 Nm's (79 ft. lb) at the wheels

Car is non competition pack and running 95 octane pump fuel (no ethanol added). Also, i am at high altitude (approx. 1750m or 5750 ft above sea level).

Am i correct in calculating the engine / crank output by adding approximate 5% correction factor for the altitude and a further 15% for drivetrain loss to get to 512 kw's (686 hp) and 982 Nm (725 ft. lb)?

Are these number in-line with what should be expected? Car is feeling very strong and definite difference can be felt. And the sound from the dp's is AMAZING.

All thoughts and comments welcome...

[gmd2003]

The ECU is already correcting for altitude by increasing boost so take off that 5% and the drivetrain loss on our cars is more along the lines of 12% . Now you have a more realistic number , but most dynos are only useful really for showing the delta between mods not absolute numbers .

[thedoctor]

Originally Posted by gmd2003

The ECU is already correcting for altitude by increasing boost so take off that 5% and the drivetrain loss on our cars is more along the lines of 12% . Now you have a more realistic number , but most dynos are only useful really for showing the delta between mods not absolute numbers .

So you're saying our cars will not lose any power going from sea-level to a high altitude? I was aware that turbocharged cars lose LESS power (as a %)than a N/A engine, but losing no power whatsoever is news to me?

[MCarsFan]

Originally Posted by thedoctor

So you're saying our cars will not lose any power going from sea-level to a high altitude? I was aware that turbocharged cars lose LESS power (as a %)than a N/A engine, but losing no power whatsoever is news to me?

Thought turbo charged cars accommodate for altitude. I'm originally from JHB and I always remember the altitude being a big factor for normally aspirated cars..

On the whp to crank conversion for RWD cars.. (Whp or KW) /0.85 = crank number..12% -15% is a more or less standard and 18% - 20% for AWD.. (As far as I am aware Boss330 is good with these calculations..http://f10.m5post.com/forums/showthread.php?t=1086187)

Hope you're having a lot of fun with your setup..

[gmd2003]

Originally Posted by thedoctor

So you're saying our cars will not lose any power going from sea-level to a high altitude? I was aware that turbocharged cars lose LESS power (as a %)than a N/A engine, but losing no power whatsoever is news to me?

That is correct the ECU runs more boost to meet the target airflow and power .The ECU has both MAF and MAP sensors to calculate airflow at different altitudes and runs different levels of boost accordingly .

[Northern X5M]

Originally Posted by gmd2003

That is correct the ECU runs more boost to meet the target airflow and power .The ECU has both MAF and MAP sensors to calculate airflow at different altitudes and runs different levels of boost accordingly .

It does compensate for elevation and air density, but I don't think it is a perfect system. Taking air temps out of the equation I think there is still some power loss. Even at 2200 ft elevation, I will not achieve some of the faster numbers posted. I mean we are talking a few tenths and a few MPH, which to most people equates to zero.

[lfelunden]

Those are almost stock numbers man, check if your intake has a hole.. If so, buy the plugs and you should be at 600+ whp

[MCarsFan]

At the wheel 423 kW is almost 498 kW at the crank with a 15% correction factor..
Stock M5 around 412 KW?
http://en.m.wikipedia.org/wiki/BMW_M...0.93present.29

I think the number posted was at the wheel.

[lfelunden]

Originally Posted by MCarsFan

At the wheel 423 kW is almost 498 kW at the crank with a 15% correction factor..
Stock M5 around 412 KW?
http://en.m.wikipedia.org/wiki/BMW_M...0.93present.29

I think the number posted was at the wheel.

Well, M5s are rated at 560, but they are do like 530-550whp on a dynojet at the wheels.. Well it has some gains, but not enough IMO

[thedoctor]

Originally Posted by lfelunden

Well, M5s are rated at 560, but they are do like 530-550whp on a dynojet at the wheels.. Well it has some gains, but not enough IMO

As you can see on this particular dyno, car, altitude and all other variables that can have an effect, the baseline / stock car only managed 383 Kw at the wheels. So the mods added 42 kw's at the wheels.

In your opinion, is this gain lower than should be expected?

[MCarsFan]

Originally Posted by thedoctor

As you can see on this particular dyno, car, altitude and all other variables that can have an effect, the baseline / stock car only managed 383 Kw at the wheels. So the mods added 42 kw's at the wheels.

In your opinion, is this gain lower than should be expected?

42 kW in gains sounds good to me

[lfelunden]

Originally Posted by thedoctor

As you can see on this particular dyno, car, altitude and all other variables that can have an effect, the baseline / stock car only managed 383 Kw at the wheels. So the mods added 42 kw's at the wheels.

In your opinion, is this gain lower than should be expected?

Your car should correct for whatever condition it runs in. So after a few hundred km, it should have similar power to other M5s..
The delta would be OK with Bms stage 1 only, but dps too, that's low in my eyes