Pelican Parts Forums - 2,9 SS mfi twin plug maximum advance

Pelican Parts Forums (http://forums.pelicanparts.com/)

- Porsche 911 Technical Forum (http://forums.pelicanparts.com/porsche-911-technical-forum/)

- - 2,9 SS mfi twin plug maximum advance (http://forums.pelicanparts.com/porsche-911-technical-forum/795950-2-9-ss-mfi-twin-plug-maximum-advance.html)

2,9 SS mfi twin plug maximum advance

I have a 2,9 MFI twin plug that cannot rev past 6.5 K and has max advance of 25 degrees.
Do you think increasing advance to 32 degress will make it rev higher?

2.0 crank
76 turbo case
97mm pistons on turbo cylinders 10.5 CR
MFI
twin plugs
91 gas

I'd try 28 for starters, and see if that helps. Then 30. My personal experience (not as much as some, more than some) is that I get over 8,000 easily with 30 max, and 28 seemed to work fine from the seat of the pants (as opposed to fine tuning on a dyno).

Both my short and my long stroke 2.8s, as well as my 2.7, have no trouble running up to 8,000 or more on the race track. That may not be the optimum shift point, but it isn't like they feel like they have run up against some limit.

You don't say what heads, what valve and port sizes, and what cam. If those are too small they can limit the ability to pump air. But the 2.2 and on valves and heads are large enough for way more than 6.5K, at least with the ports opened up some.

And then there is the cam. I'd think an E or S would do better than that.

Though with a nice motor like this I suppose you have all that covered.

Another thing to look at is valve springs. Although broken inners (or broken outers, as I have had both although never together) were good for 7,600 rpm, and I finished a race that way with no trouble other than wondering why it felt like a soft rev limiter was cutting in.

I have no MFI experience - are your plugs looking way lean.

2,9 MFI twin plug

I used the head of a 1978 SC(big ports) and regular valves and springs and DC 60 cam per John Dougherty. JE 10.5 pistons

MFI rebuilt by Fairchild Injection

Quote:

Originally Posted by greyes59 (Post 7902392)

Engine timing (cams) have a lot to do with extending the rpm range for more power. However, if the engine can't rev. beyond 6.5K, it could be a mechanical issue. Have you checked the throttle plates at "full throttle" (engine OFF) and confirmed they are indeed vertical? There are lots of engines handicapped with an involuntary rev. limit due to a mis-adjusted throttle cable/linkage.

Sherwood