Andy Roe

Yep, I think I'd be taking mine to Colin for the 3.6 rebuild plus Motec too.

Cheeksyboy

Thanks Gary, I too have to thank Colin and Co at 9M for my cars speed, but it was built for longevity so there's not much over a standard engine, in otherwords there's still plenty of scope for more HP, but only in exchange for £ and Colin's always happy to relieve me of them......but for now the car is faster than me, so I need to learn to get the best out of the handling before going for more power.....

Frank, we've already chatted a fair bit about this, and you have a pretty good idea how much my engine cost me.

If I were spending your money then of course I'd be saying to go 4.0, throw Colin an open cheque book and enjoy looking at GT3RS's, 458's etc in the rear mirror.....but back in reality I'd stick with 3.6 capacity, and follow COlin's advice for a 7k rpm capped engine with some better breathing, engine management and exhaust (Colin will correct me if I'm wrong, but there are bottlenecks throughout the engine so performance of any rebuild will be limited by the amount and speed of air/fuel you get in and gasses out.

The amount you decide to spend has to be weighed against how much you will use the extra performance and how much you can make use of the extra performance. There's probably more (lap) time to come on track from honing your suspension settings than there is from increased engine power....and from tuition!

I pulled back the GT3RS 4.0 on the brakes and cornering at Spa, but could have recovered more time with better handling through the mid-high speed corners (where his aero gave him an advantage)......of course if I'd have had more HP then I could've stuck with him on the straights.....but hopefully you get my point. If I were racing then more power would be required, but for a trackday I was having fun.

For what you'll probably spend on a trick rebuild you could sell your car and put all the sums towards a much faster car...but you probably wouldn't have more fun! Trust me, 996t's are sooooo much faster, but not more fun!

Just my 2p

Porsche964FP

When running max 7,700 rpm what cams & piston/cylinders are recommended?

Cams: RSR, Cup, 9m other?
P&C: Mahle?



Thanks Grant - as always you're the voice of reason in my ear and your advice has been instrumental over the past weeks.

Agreed there is no substitute for driving talent - however IMO you only rebuild once but you continually become a better driver. So as the old saying goes, while you're in there.

As I keep saying I wish to gain as much knowledge as possible pre build before deciding on final specification. Watch this space it may get interesting...

VR6-er

+1.

mr pg

Having gone from a 964 to 996T, I can vouch for this! I considered an engine rebuild/upgrade before selling my 964, but decided against it. However, if I didn't go down the GT3 route in the future, a fully sorted 964 would rock my boat nicely.

NineMeister

Pleasure.

Yes, you are correct, running ITB's on a 964 engine tuned for max performance under 7000rpm is detrimental to the overall performance of the package. Resonance flap (stock 964) & Varioram (993) manifolds will both make more torque and provide a greater area under the power graph. More area = higher average acceleration = faster car.

In respect of reliability, it is perfectly feasable to build a 100 hour race engine that runs at 8000rpm - the same life as a 964 Cup at 7000rpm. Before you do the maths, bear in mind that the GT3 Cup engine is rated at 30 hours.
In road terms, lifespan is proportional to the average loads that the engine parts undergo. Peak loads increase with the square of the speed, hence a rod/piston assembly at 8000rpm will have a 30% greater load than the same assembly at 7000rpm, but the facts are that a 8k road engine is going to run so infrequently above 7k that the difference in average load will be nominally higher than stock. This nominal increase can be easily offset by the use of a ligher piston.....

NineMeister

These choices are all down to the tuner, it's where the synergistic approach comes into play. For instance, two different pistons may happily do the same job, but one could have a 12:1 compression and the other is 11:1, however if the 11:1 has a better squish design it may have a faster burn than the 12:1 which could make more torque. Lower static compression would also mean that the intake valve closing point would have to change to achieve the same dynamic compression ratio (based on piston stroke from IVC to TDC). But, a lower compression piston also leaves more space to cram in air/fuel mixture hence allowing a potentially higher VE (Volumetric Efficiency or cylinder filling).

In other words, it's a complicated, multi-variable equation and there is no "right" answer - so just go with the recommendation of your builder and use what combination they can guarantee will work.

VR6-er

Colin,

Is it not possible to use a later Bosch ECU to get the benefits that Motec give you? I understand that you'll need an appropriate map.

NineMeister

Anything is possible. I did mention in my first post that a 95 993 ecu is useable for Alpha-N applications, but finding someone to install & map it properly is the hard part.

Motec also has the advantage of being able to run a hybrid Alpha-N/MAP based fuel table with full programmability of the idle valve, so you will trade off the Motronic advantage of knock control against a reduced functionality and lack of user adjustment.

fuch

Frank just put a Subaru sti lump in & you have 400 bhp & it might last till the the end of the summer untill it goes bang & then just replace it....ok back to my medication...........

KiwiSean

lol- at least it's a flat 4.


On a more serious note, why wouldn't you go to 3.8 if you're rebuilding? I'm sure it has been discussed at great length before but it seems topical to this thread since the additional cost is little to nothing if the P&Cs are being replaced anyway?

EDIT: What I mean is Geoff can you explain this a little more for me please as it goes against conventional wisdom- "no replacement for displacement" and all that...

"I'd stay 3.6l for durability, and a properly built 3.6l piston will produce more power and torque than the RS 3.8 piston"

Cheeksyboy

The only thing I'd add is that you need to first decide what your usage requirement is...i.e. do you want a daily driver with occassional track use, or do you want a weekend toy/track car.....

...what I mean is, whilst electronics can make race engines very tractable, the need to perform on the track will, to some extent, create compromises on the road and vice-versa. You'll also get through ligt weight race clutches and have to keep swapping brake pads (to avoid the squeal that associates with many race pads), etc, etc, etc......

...and then talk to your chosen engine builder and, like Kai has done, make a decision not just about your engine, but also how and what you use the car for......

...The Hornet is definitely more of a track car than a road car nowadays.....and I always swore it wouldn't end up that way!

P964miller

Frank you nutty bugger! Where are you getting all this cash! It was a certainty that you would keep the car but this looks like quite an endevour which will cost a wheelbarrow full of cash! Be careful not to get too carried away mate. Tom

boxsey911

When I had my rebuild I considered power upgrades for a few seconds and then dismissed them. Thank goodness I did because (as I've mentioned a number of times before) the rebuild was much more than the cost of the bits inside the engine. Once it's out you see the rusty tins that need replacing, the hardened and corroded oil lines and the miscellaneous items that need replacing like cracked intake stacks. The bill suddenly gets 50% more than the estimated cost of a rebuild.

For me a standard fresh engine with LWF is more than I can exploit. I know for a fact that the car is so much better than me.....a friend of mine who races (Marcus 'the Goose' Carniel) can get it round Oulton Park at least 8 seconds quicker than me (2.13 vs 2.05). I also wonder just how much power a standard fresh engine has. I certainly think it's more than the factory claimed 250 bhp. Especially since at Oulton Park* this week I could keep pace with Oltimer's modified C2 (which has been dynoed at 300 bhp) and kevin's 964RS.

So my vote would be to keep to a 3.6 and work out a plan to give you a 300 bhp engine e.g. a standard rebuild locally and then a trip to 9M for Colin to add some goodies like Motec, injectors and mods to the air intake system.

*I'll post a thread about this week's fun day out at Oulton when I get a chance.

NineMeister

Excellent point. Sometimes less is definitely more.

I think that my first suggestion to Frank was to just go for a 9m Motec conversion on a fully rebuilt engine with new standard 3.6 P&C's, new 993 valves with 9m Sport spring/retainer pack, all assembled to finer RS tolerances & topped off with a LWF assembly. Should be good for 330hp, 100,000 miles and be a complete ***** around town. For more low end the varioram manifold is the next best upgrade if the car spends a lot of time pootling around in traffic. If the stock cams are shot, replacing them with 9m Sports cams (+1 upgrade) will liven up the top end (350hp) at the sacrifice of some low end, the Motec still providing a more than acceptable idle & town performance.