Darren congrats on a great car ,I had the E34 4 litre 6 speed manual good cars all round, bit heavy for the twistys but stil a good perfromer none the less.
I did this to pep her up & it did make the car a goer, 1st of all you can buy a diff from a 1991 750iL BMW, you will have to change the Prop flange & thats it ,it will then bolt straight up in there.
Its a LSD Diff but the beauty of it is the ratio is 3.15 instead of the 2.94 that is in yours, this just gets you off the line that tad bit quicker , as far as the revs goes it will rev approx 600rpm more so instead of say 2100rpm at 80 you'll be 2700rpm so MPG is not to affected . people reading this may think Pah why worry about MPG in a 4.4 litre well these will give you just over 30mpg at 80 all day long!!
After the diff you then open up the front of the standard airbox, if you take the box out you can actually dismantle the front secrion which will give you roughly a oblong air entry of 2.5" high x 5" long & then fit a K&N panel filter & listen to that V8 burble. Then the exhaust, a nice stainless system can be bought & fitted for about £300, I think you have to change the gear lever for a short throw one as well,as the throw on these boxs are a joke for quick changes , do this when the diff is being fitted as you have to take the prop off to get to the gear lever to fit. After this contact E Maps to re map the car & then you have something that not only sounds as good as any Alfa ever has but will take off like cat with its balls on fire! I have a M3 evo ehich goes quite well ,the 540 obviously will not stay with it from standstil at all but I know that if I was in my M3 next to you at 80mph & we both dropped from 6th gear to 4the gear & nailed it that the M3 would lose up to 120ish , the mid range on a sorted 540 maual will embaress most cars except the V8 M5 ofcourse but then look at the money a 540 has set you back against say my 98 M3 Evo will almost double well done Darren here's my old 540
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