2.8 high revs (asking for another owner)

[DaveP]

Hi all,
I just saw a post on FB by a 2.8 owner who has converted to a kobra. Seems they have a high revving car. As an armchair mechanic i am very unsure what the issue is but know people who do
Here is the post from FB.


"" "" hi fella-asking you as you're familiar with the z3/kobra & sure seen on here you're in the trade. Hoping for a little advice if you have time...I was adamant remap & inlet manifold swap once on road but now on road I'm little puzzled...in 5th 70mph is @ 4.5k rpm!surely that's not stock?..its epic on backroads though!!! Rear diff been swapped for low ratio?? Also this crazy lill kobra will rev right past 7k redline & the needle is at the 6 o'clock position before I get chance to change up if driving hard...wouldn't there be a rev limiter???cheers "" "

 

[Dino D]

It sounds like it has a much lower ratio diff.
Must be very lively!

The high rev limit is due to the a remap which is probably set at any anywhere between 7-7,6k rpm (you can usually choose when having it done)

 

[DaveP]

Thanks @Dino D.

Is there anyway to tell the diff ratio from the outside do you (or anyone else) know?

 

[Lee]

Thanks @Dino D.

Is there anyway to tell the diff ratio from the outside do you (or anyone else) know?

Theres normally a sticker on top of the diff with its ratio. If it's at 4.5k at 70 I would guess around 3.88 / 4.10

I changed my diff to a 3.38 and thats now 3.3k at 70mph ish.

 

[DaveP]

Thanks @Lee

I presume it must have been swapped in a previous ownership. The ratios you mention; they common in the E30 E36 world ? I would have thought they not in a Z3 unless it’s one of the four pots?

You still have the 2.2’s diff in the soon to be 3.0 ?

Dave

 

[Lee]

Yeah your on the money, those ratios are common E30. Most likely swapped internals.

Yeah still running the 2.2 diff it's one hell of a setup, going to be more fun with the extra horses from the 3.0. It kept pace with an M high into third gear with the 2.8.

 

[DaveP]

Hi all,

Latest on this one from the 2.8 Kobra owner is :

“Hey Dave well after some head scratching thinking a straight 6 just can't rev like that put a infrared tacho on crankshaft pulley & yep the cars tacho is reading about 14-1500rpm too high-havent a scooby why?? “

Any clues as to why Rev counter may be reading incorrectly ?

Cheers

Dave