99 sc540

[kjq69]

Hey there,

Looking for more ponies in my 99 SC540i.....Story is that a Dinan mechanic owned and put the car together.....

Dinan claims 6 psi originally.....The tune is pretty cool, 7000 rpm redline. e34 M5 injectors.....stock resonator with straight pipe from there (sounds perfect)........went down in pulley size from 3.48 to 3.33.....maybe gained 1 psi.....recently replaced plugs and coils along with the addition of an M5 differential. I run a blend of 100 octane / Super and 1 gallon of E85............Car runs quite well.

It seems like the easiest way to increase hp would be an "upgraded" impeller and maybe one more size down in pulley. That would put me close to 8psi or so......Can I run 8 plus psi without a cooler and have good results? .........Would a WI unit work well with just 8psi?

I have a line on a set of Supersprint headers and exhaust system out of an M5. Being in California, I still would want to run some kind of catalytic converter and what ever is needed to keep the CEL off........what type of "real" hp is expected with headers?.......

Anything you can share with me is greatly appreciated!!!.....ken
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[chikinhed]

Definitely install a WI kit even if it’s a cheaper progressive kit like Snow or AEM. It will make a huge difference.

[philly98540]

If your bored at work. https://www.bimmerforums.com/forum/s...-the-Stock-M62
16 psi, W/A, Meth.

Do the water/meth as first step. What size injectors do you have? If going above 12 psi, youll need at least 42 pounders. You can pulley down to get where you want.

[kjq69]

Thanks for the advice........The injectors are S38 M5 ...25lbs.......

So what are your thoughts on the kind of gains with just the addition of headers???.......an honest 25 - 30 for a supercharged car?.......Does a WI unit add another 10-15 or just eliminate the inconsistency from day to day weather?...thanks ~ ken

[philly98540]

Those injectors are likely maxed out where you currently sit. Gotta go bigger if you want to go smaller pulley. An AFR Guage is required to ensure safety.

Headers may give about 20 or so. Do the water/meth for safety and better hot weather performance.