RollingArt

? ? ?? ? ?

WTF??

That there's some double doodle back talk.

JPS

And baby oil...

TheOtherEric

Ok so you're actually doing that. I assumed that whoever said stock CR was simply mistaken. Although now that I think about it, I believe BMW was able to pull 100 hp/L from their mid-90's M3 engine using a CR of 11.3 and that's exactly what you're doing.

I thought I heard you were bumping up the CR, but perhaps it's more like "restoring" it to where it should be:
https://rennlist.com/forums/993-foru...ade-993-a.html

NineMeister

You're not wrong in what you said Eric, the 9m heads have 3cc smaller combustion chambers than a stock 993 cylinder head, however as you have deduced from Geoffrey's comments the reason why we did this is because every standard engine we measured failed to make the Porsche-specified static compression ratio.

The only reason why I decided not to be immediately forthcoming is that there are a plethora of engine variables which can be altered to gain power or torque, for instance: valve timing (open & close, inlet or exhaust), valve size, valve seat cuts & angles, inlet port area/volume/length, inlet port area profile, header diameter/length, piston to head clearance, piston crown design, etc., etc., hence it has be technically wrong to isolate compression ratio as the one variable that must be changed otherwise none of the above will make any difference.

In fact, in some rare cases of engines with exceptionally high volumetric efficiency, it may actually be desirable to reduce the static compression ratio in order to yield more space to fill with mixture to burn....


Anyway, the build of the engine will use 9m billet heads (50mm/42.5mm valves), 9m Sport camshafts, 9m Sport valve spring set, mechanical rockers with ported intake runners, 100 cell cats and a live remap and we are expecting somewhere around 350hp on the 9m dyno, which will be around 300+hp at the tyres.

RollingArt

Now you're talking!



Phil

CalvinC4S

Colin, how much of a hit would the lazy guys take that want to keep there hydraulic rockers? Can you adjust #6 intake with the motor in the car?

What are box stock 3.6 Varioram motors putting out on your dyno?

Are your cams keyed?

This great stuff, thank you!

Edit to add, Are your cams set up to keep power steering?

NineMeister

We recommend mechanical lifters to anyone with a high miles engine that is going to be used heavily at high rpm, i.e. track use, irrespective of how hard it is to adjust them afterwards. That said, another customer who had the first non-Varioram +2 conversion (John S) told me the other day that he has had his clearances checked twice in the 20k+ track miles that he has done in the car and they still don't need adjusting. The penalty for using old or soft lifters is a loss of power when the engine gets very hot.

A stock NVR will make anything from 275-285bhp, the stock VR will usually make 290-300 with an exceptional few making 310. The best RS we have tested made 320bhp at the flywheel. The VR+2 conversion typically makes from 345-355hp and the VR+3 (3.8) makes 360bhp.

Yes, the cams are keyed and are set up by optimising the centrelines with a degree wheel then inlet lift checked at TDC. The cams come with PS take off, so if you don't need it you get out the hacksaw...

1pcarnut

Colin, curious about the intake manifold modification? Thanks.

NineMeister

Simple - do this until the ports are the optimum profile from top to bottom:

1pcarnut

Okay, thanks, that makes sense. Thought maybe you were changing the vario-ram mechanism.

axl911

Interesting tool. What is it called? The lower section of the Vram is easily unbolted. I may do this the next time I have the intake off.

CalvinC4S

Not a good idea with stock head ports.

axl911

Can you elaborate? Not good idea since it's useless on the stock head port???

NineMeister

The tool in the end of the flexi-shaft electric die grinder is called a flap wheel, made from various grits of emery cloth glued to a 1/4" spindle. I use 40 grit to rough it out and 80 grit for fine finishing. Be warned that you need to use suitable protective equipment.

CalvinC4S

If im not mistaken it's done to match the intake ports of the new heads.