# Power Surge at 5500 RPM?



## 540-S3 (Mar 29, 2006)

I have an issue with my 1997 540 6-speed with a Dinan S3 supercharger. At about 5500 RPM I get a strong surge of power to redline. Is this normal? Shouldn't the power be more uniform through the powerband with a SC? It feels more like a turbo kick to me. Any help?

Regards,
Audie


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## firedwg1 (May 21, 2005)

Hard to say, I know on my 3.0I SC I had very stong power between 3200Rpm - Redline.

I think you will find that most BMW begin to pull hard around 5K RPM.


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## joema (Aug 28, 2002)

Dinan uses a Vortech compressor. I think they're biased toward top end power, relative to an ASA compressor. The question is how much boost do you feel below 5000, and how gradual is the transition at 5000. 

I don't know what's normal, but it shouldn't come on like a light switch at 5000.

You can get some idea by looking at a before/after dyno graph for your kit. If you look around you should be able to find one, maybe even on the Dinan site. Examine the graph and see if it matches what you feel.

My Technik SK1 (ASA compressor) provides some boost at part throttle as low as 2000 rpm, which I can feel. However it's more obvious above 3000, and doesn't produce huge gains until above 5000.


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## joema (Aug 28, 2002)

Here's some more info that seems to confirm the behavior you observe:

http://forum.e46fanatics.com/showpost.php?p=3858899&postcount=1

Technical info on the ASA TMI12:

http://www.a-s-a.de/htm/english/products/data_sheets/e_dat_tm12.html

The next up is the TMI15, used on Technik's stage 2 kit:

http://www.a-s-a.de/htm/english/products/data_sheets/e_dat_tm15.html

Here's similar info for the Vortech V2SQ:

http://www.vortechsuperchargers.com/support/s-trim_v2_map.html

Unfortunately they use different units, plus are hard to read.


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## 540-S3 (Mar 29, 2006)

joema said:


> Here's some more info that seems to confirm the behavior you observe:
> 
> http://forum.e46fanatics.com/showpost.php?p=3858899&postcount=1


"The Vortech felt like it came alive about 4500rpm and got stronger towards redline. Like it was just getting good and the rev limiter kicked in."

Good stuff joema! Sounds like exactly what is happening to me and it is expected behavior for the Vortech. Danke!

Regards,
Audie


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## dynosor (Jul 15, 2003)

540-S3 said:


> I have an issue with my 1997 540 6-speed with a Dinan S3 supercharger. At about 5500 RPM I get a strong surge of power to redline. Is this normal? Shouldn't the power be more uniform through the powerband with a SC? It feels more like a turbo kick to me. Any help?
> 
> Regards,
> Audie


My brother had a 95 540i with Dinan supercharger and it felt as if torque picked up from 3000 RPM, getting stronger all the way to red-line. This is a characteristic of a centrifugal compressor - they flow much more air as the revs rise.

A Roots "blower" is a positive displacement supercharger and boost would be much more linear.

Your car may be running lean below 5500 RPM or the ECU may be detecting knock, otherwise I would expect more boost from 3000 RPM.

What octance fuel are you using?


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## 540-S3 (Mar 29, 2006)

dynosor said:


> What octance fuel are you using?


91


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