[Kunz]

Hi Orphanowner



I have no problems to share my little knowlege, the results and the way I got there. Personally I think these forums are the place to get on with each others help and experinaces.



I sure know results and numbers always have to be taken with a bit of salt; different dynos, different numbers...what will count are the relativ numbers before-after.



What I also had to learn on the 968: What is true for one car does not neccessarily has to be true for another one. Little changes seem to have a big impact on torque characteristic and performance due to the extremly sensibel balance between the - in my eyes - not so lucky intake design and the exhaust, respectivly the backpressure.

On my car the Cargraphic catback gave some torque down low but produced a signifacant dip at 3500rpm and almost no change up the revs. This was with a badly removed cat.

Installing then the mentioned 2x200-cellers made the engine loose some torque down low, flattened the dip a bit and gave very little gain up the revs.

Installing the Sport-cams gave very little gain over 6500rpm (3hp) but made the car loose significant torque over the revs even though we did everything right (timing and tuning) and as ordered.

On the car of the guy who sold me the cams they made some real gain with the same timing....

So we have to keep that in mind...



Now we have a timing that is COMPLETLY different from the one we were ordered to do and slowly get to the point. It seems in my case, going back from the 2x200 to one 100-celler will bring out the best of the cams...



I can post result and graphs if you and others are interested in the mods and the linked results...



We will see tomorrow...



Cheers

Andi

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

[quote name='flash' date='Feb 23 2006, 08:34 AM']every engine vibrates at some frequency - some have it occur at a specific rpm - this one is at 2300 or so - other engines have a dampener at the front pulley



what happens is the G44, which is a very loosely toleranced box, which is what makes it shift so smoothly, is then allowed to rattle because there is nothing left to dampen it



a spring centered disk would dampen up to about 30 ft/lb of that rattle, which would help at idle and decel, but not at accel - i have looked into getting a chromoly flywheel made that would accept that kind of disk - cost would be about the same as the fidanza in quantity of 20, and would take about 3 months

[right][post="16447"]<{POST_SNAPBACK}>[/post][/right][/quote]



Interesting stuff. So, if the tolerances in the transaxle were tighter, I suppose there would be less rattle. Also, why not go with a dampened front pulley? Is it because the extra weight would defeat the advantage of a lighter flywheel?



The chromoly flywheel that would accept a spring centered disk sounds like it would be a good compromise for many - much lighter than the DMF, but not quite as light as an Al flywheel, but with somewhat less noise and vibration (I know we talked about it when we talked on the phone a few weeks ago). When my clutch goes out (I have over 90K on my car now, but I don't know if the clutch is original or not), I would definitely consider this, if it's available.

Partial Post: Please Login or Register to read the full post.

[Greimann]

[quote name='Cloud9...68' date='Feb 24 2006, 08:21 PM']... Also, why not go with a dampened front pulley?  Is it because the extra weight would defeat the advantage of a lighter flywheel? 

[right][post="16523"]<{POST_SNAPBACK}>[/post][/right][/quote]

Just to be clear, harmonic balancers on the front of some motors is to counteract crankshaft twist due to combustion pulses. This helps keep the crankshaft from going into harmonic oscillation and tearing itself apart.



This is independent of driveline shock which a dual mass flywheel or a spring centered friction disk absorbs.



Why the 968 does not have a harmonic balancer, I am not sure, perhaps the crank is robust enough to take it or there is some other defense that the engineers have devised, but driveline shock is either absorbed by the DMF or the tranny.

Partial Post: Please Login or Register to read the full post.

[flash]

in our case the DMF does some of both jobs - it is also on the crankshaft - they may have figured they would kill two birds with one stone - just a danged big stone - they may have figured tou there wasn't enough left at the other end of the crankshaft to worry about and that the balance shafts may have offset that



speculation, but seems logical

Partial Post: Please Login or Register to read the full post.