E39 528i power gains

[jeffbebe 1559]

Have sorted fuel consumption issues so now interested in any simple things I can do to improve power at the wheel in my E39 528i. Particularly low-end power - she's very comfortable and has more than enough grunt at mid RPM levels but a bit slow off the mark.

Not looking to race anyone off the line so don't need major power gains (i.e. no supercharging, turbo or upgrading to 4.4 V8).

Would decat and ECU remap make much difference? Anything else I can do that wouldn't cost an arm and a leg? And anything I can do myself without too much technical know how?

[BM WORLD 1265]

diff ratio change??

[jeffbebe 1559]

diff ratio change??

Hey Brent, you know I'm not overly technical! So a lower ratio will provide slightly higher acceleration at the expense of slightly worse fuel consumption, right?

How easy/cheap is it to do?

[smiddy 76]

Think I may still have some long headers somewhere for E39. Good for about 12hp.

[jeffbebe 1559]

Think I may still have some long headers somewhere for E39. Good for about 12hp.

Cool. PMd you.

[Michael. 2312]

Depends how much coin you want to spend... but I would do

1) Modified valvebody for your automatic transmission, aka 'shift kit' - this will turn it from a slush box into a much more responsive quick shifting automatic. The general idea of them is to have various internal fluid passages enlarged (drilled) for higher flow along with harder shift/accumulator springs etc for firmer application of the auto brake bands and clutch packs.

2) Like Brent suggested, change the diff ratio, by going shorter your going to loose top speed, have slightly higher rpms at crusing speeds but a great upgrade in my opinion, it will really help the car off the line big time.

3) As also mentioned above get the appropriate headers.

4) If you don't want a S/C or Turbo then perhaps look at tweaking the cams to some that will aid with lower RPM torque/power - you may loose top end but one size never quite fits all...

5) Strip the interior out, you could probably save in excess of 300kg by removing the luxuriousness of the machine and turn it into a big.... JOKE. I kid - obviously this is not a solution.

6) Get a 330i and do all of the above? (already a lighter car etc....)

[liyi_92 37]

That nagging feeling that it should be a little more...power. I completely understand the situation but all in all, the things you do to a 528i for power gains are very limited without going FI. Intake, headers, exhaust, Dinan ecu. So in the end you may be spending a lot of money for not a lot of gains...

[Michael. 2312]

That nagging feeling that it should be a little more...power. I completely understand the situation but all in all, the things you do to a 528i for power gains are very limited without going FI. Intake, headers, exhaust, Dinan ecu. So in the end you may be spending a lot of money for not a lot of gains...

Indeed.

[jeffbebe 1559]

That nagging feeling that it should be a little more...power. I completely understand the situation but all in all, the things you do to a 528i for power gains are very limited without going FI. Intake, headers, exhaust, Dinan ecu. So in the end you may be spending a lot of money for not a lot of gains...

Neither require big gains, nor want to spend a lot of money! Long headers and diff ratio seem best bet and affordable (in the new year!).

[jom 96]

Neither require big gains, nor want to spend a lot of money! Long headers and diff ratio seem best bet and affordable (in the new year!).

Or - just get the gearbox software zeroed, put it in sport mode and drive it like you stole it for a while. That should improve the shift - it's adaptive and responds your driving style.

[jeffbebe 1559]

Or - just get the gearbox software zeroed, put it in sport mode and drive it like you stole it for a while. That should improve the shift - it's adaptive and responds your driving style.

I've reset the adaptions before... Didn't make a great deal of difference TBH.

[jom 96]

I've reset the adaptions before... Didn't make a great deal of difference TBH.

I had the same experience until I reset the box before 20 laps of Manfield - and that really did make a difference. Also the "Italian tune-up" factor would have come into play too.

[Allanw 1052]

chuck the slush box my 528 was a manual and far more engaging and dynamic to drive because it sucks less powere leaving more to drive the car

That's probably the best, reliable bang for buck upgrade - resolves possible future auto issues, and greatly transforms the car. I really enjoy our manual 525i, even though it's only a 2.5. You'd think it would be a slow barge, but it eats Dads manual E30 325i for breakfast - blitzes it! even with the extra weight.

[jeffbebe 1559]

That's probably the best, reliable bang for buck upgrade - resolves possible future auto issues, and greatly transforms the car. I really enjoy our manual 525i, even though it's only a 2.5. You'd think it would be a slow barge, but it eats Dads manual E30 325i for breakfast - blitzes it! even with the extra weight.

Would love to do a manual conversion but my better half can only drive autos and, unfortunately, she has to borrow my pride and joy now and again!

[tmase 19]

My missus won't drive an automatic and she's a menace!

[jeffbebe 1559]

teach her to drive properly - people who are only competent to drive autos are a liability on the road , they brake in corners, sledge and do all sorts of other nasty things

Some people, sure, but I think that's a sweeping generalisation. She's actually a very competent driver and has been on several of those advanced driver courses (for work) so she can probably handle herself better when the car gets sideways, etc than I ever could. She's just never learned to drive a manual and I don't think she has any desire to learn.

[jeffbebe 1559]

Been tinkering with the car all weekend and have come to the conclusion that the issue is not a lack of power - at least not when the car is running at peak temperature. The problem is that she's not that happy from a cold start. in particular the car just feels sluggish until it's warmed up and idles pretty roughly until the temp gauge gets well above the blue. It wouldn't be such a big deal if it wasn't for the fact that 80% of my driving is around town from cold - so I don't get many opportunities to drive the car when it feels good. If I could get it to feel half as good when cold as it does at peak temp I wouldn't need to improve it in any other way (though I might still do it for fun!).

So far I've done the following:

Replaced all ignition coils + spark plugs

Cleaned fuel injectors and replaced all o rings

Checked vacuum hoses for leaks and can't find anything

Scanned and the only fault is memory module because I've got the wrong driver's seat in at the moment

Any advice/ideas or is it something I should just live with? I've got a replacement o ring for vanos but haven't got round to replacing. Have had mixed reports about what difference it will make. Lots of people in forums talking up the benefits of replacing the vanos seal but quite a few mechanics I've spoken too think it's a bit of a placebo.

Edited December 2, 2012 by jeffbebe

[tmase 19]

I got my Vanos O-rings replaced the other day. Done about 300 kilometres of city driving since then which is about the minimum recommended to bed them in. I wouldn't say the before and after difference was night and day but I reckon I can feel a bit more mid range urgency from around 3000 RPM. Doesn't seem to have made much of difference lower down the rev range. That's just what I feel, I haven't done a before and after dyno or anything but I am sure someone has somewhere. This is in an M54 but I guess you'd get similar results in an M52.

I actually got mine done more to see if it would eliminate a slightly rough idle when the engine is cold (less than 15 degrees ambient) that lasts for about two minutes, but it doesn't seem to done much to that. The other benefit touted was better fuel consumption but I haven't done enough driving to see if there has been a difference there.

I think the idea that they can fix the rough cold idle might only be limited to the M52TU engine.

With more driving I might see better results, but unfortunately I am away with work so I haven't been doing any. I'll keep you posted with any other observations when I get back.

[jom 96]

The problem is that she's not that happy from a cold start. in particular the car just feels sluggish until it's warmed up and idles pretty roughly until the temp gauge gets well above the blue.

How long does it take to get up to temperature? My 328 shows normal after about 2km, but took much longer to warm up before I replaced the thermostat.

[jeffbebe 1559]

With more driving I might see better results, but unfortunately I am away with work so I haven't been doing any. I'll keep you posted with any other observations when I get back.

Thanks. Very interested to know. I wondered whether a lot of people like to think replacing it has made a massive difference because it cost them a fair bit of time and/or money to do but an honest appraisal would be great.

[jeffbebe 1559]

How long does it take to get up to temperature? My 328 shows normal after about 2km, but took much longer to warm up before I replaced the thermostat.

The rough idling is usually gone after a minute or two but I'd say that it's at least 7-10 minutes before the car is at peak temp and the difference in performance by then is significant. Unfortunately, most of my driving at the moment is short trips around town, so the car rarely gets to fully warm up and feels a bit sluggish as a result.