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Slippydiff's Zanzibar GT3

The motor should go well past that mileage before needing adjustment, Nick, some of the bikes are checked at 30000 miles, despite revving to 14000+ rpm. 4500 seems to be needlessly early, assuming that on the road, a motor can never be used as hard as on track.
 
I believe that's what the engine builder recommended - probably erring on the side of caution (not a bad thing given what could happen if they do go out of spec!). Of course, the GT3 valves / springs are considerably heavier than the ones in a bike so I'd guess that's also a factor. Even on the standard engine, the springs are very close to being coil-bound on full lift.
 
NXI20 said:
I believe that's what the engine builder recommended - probably erring on the side of caution (not a bad thing given what could happen if they do go out of spec!). Of course, the GT3 valves / springs are considerably heavier than the ones in a bike so I'd guess that's also a factor. Even on the standard engine, the springs are very close to being coil-bound on full lift.

Next time I race with Richard I would ask about that. Sounds wrong - the S54B32 as found in the BMW M3 of 15yrs ago has a tappet adjustment interval of 30k miles on the Street cars. In stock form it revs to 8000rpm, while in race trim it revs to 9000rpm...
 
Cheburator said:
NXI20 said:
I believe that's what the engine builder recommended - probably erring on the side of caution (not a bad thing given what could happen if they do go out of spec!). Of course, the GT3 valves / springs are considerably heavier than the ones in a bike so I'd guess that's also a factor. Even on the standard engine, the springs are very close to being coil-bound on full lift.

Next time I race with Richard I would ask about that. Sounds wrong - the S54B32 as found in the BMW M3 of 15yrs ago has a tappet adjustment interval of 30k miles on the Street cars. In stock form it revs to 8000rpm, while in race trim it revs to 9000rpm...

I believe Richard was being cautious in this recommendation. That the clearances needed adjusting wasn't cast in stone, but merely his recommendation to keep an eye on things such as maximum revs used, cylinder leakage, and the valve clearances.
But another Porsche indy who's run 996 GT3 R race cars (and yes it is relevant in this instance) was also adamant the clearances on this engine should be checked and adjusted if necessary.
Bearing in mind the build cost, the above suggestions sound pragmatic.
As for your example of the BMW M3 engine, I think the specific output/maximum rpm of an engine has little to do with it's valvetrain durability and longevity.
I'm sure Mike will confirm that valve train wear has far more to do with cam lift and duration, with as Nick has said the weight of the components within the valve train, those being the valves, retaining collars and rockers etc also being a major factor.
(but the above are only my thoughts, and thus they're not gospel...) :)
 
Slippydiff said:
Cheburator said:
NXI20 said:
I believe that's what the engine builder recommended - probably erring on the side of caution (not a bad thing given what could happen if they do go out of spec!). Of course, the GT3 valves / springs are considerably heavier than the ones in a bike so I'd guess that's also a factor. Even on the standard engine, the springs are very close to being coil-bound on full lift.

Next time I race with Richard I would ask about that. Sounds wrong - the S54B32 as found in the BMW M3 of 15yrs ago has a tappet adjustment interval of 30k miles on the Street cars. In stock form it revs to 8000rpm, while in race trim it revs to 9000rpm...

I believe Richard was being cautious in this recommendation. That the clearances needed adjusting wasn't cast in stone, but merely his recommendation to keep an eye on things such as maximum revs used, cylinder leakage, and the valve clearances.
But another Porsche indy who's run 996 GT3 R race cars (and yes it is relevant in this instance) was also adamant the clearances on this engine should be checked and adjusted if necessary.
Bearing in mind the build cost, the above suggestions sound pragmatic.
As for your example of the BMW M3 engine, I think the specific output/maximum rpm of an engine has little to do with it's valvetrain durability and longevity.
I'm sure Mike will confirm that valve train wear has far more to do with cam lift and duration, with as Nick has said the weight of the components within the valve train, those being the valves, retaining collars and rockers etc also being a major factor.
(but the above are only my thoughts, and thus they're not gospel...) :)

Hi Slippy. There are many factors which need to be borne in mind here, principally the design of the ramps at either end of the cam flanks. These serve the purpose of preparing the valve for lift by decreasing the tappet clearance just prior to the actual lift profile becoming active.

Of more interest is the closing flank of the lobe and its attendant 'closing ramp', which dictates the velocity at which the valve is re-seated. If this engine runs titanium valves and beryllium-copper valve seats (possible?), they need to have a bespoke closing ramp to avoid pounding the seats out. A well designed ramp will gently seat the valve, without adding excess duration to the profile. As an analogy, it is akin to feathering the brakes just before a dead stop is reached after some hard braking, thus avoiding the dreaded kick-back due to an instantaneous velocity change.

If the engine still runs steel valves and standard seats, the mileage at which they should be checked depends largely on the duty cycle of the engine (the amount of time it spends at WOT, basically), which on a road engine is in single figure percentages. A cup car will likely experience a 45% duty cycle, so typically 8-9 times the road car's. This was why I suggested it should run longer than 100 hours between checks, but Richard was probably wanting to get them checked in order to get a feel for the valve train when running under road conditions, rather than race conditions.

The mass of the components should always be factored into the profile design, along with a properly designed valve spring. When properly matched, the inspection intervals should be relatively light.

One odd phenomenon can take place with engines that see sporadic use; the clearances can increase due to carbon lifting off the backs of the valve heads , (as a result of moisture being present in the atmosphere), which then drops onto the valve seats, increasing the tappet clearance. Generally, clearances tend to close up rather than increase, but this is one exception to that 'rule'.

I would imagine that if Richard finds that there is no change at a all in the clearances, along with minimal cylinder leakage, he will be happy for the motor to go for a longer period before inspecting them again. I get where he is coming from, I built a hillclimb motor in 2010, which due to the short run times, I had no idea of the point at which it needed checking. Fast forward to 2017, the motor came in for a freshen up, all the valve clearances were as the day it left the workshop, despite having its neck wrung at 9300 rpm for the last 5 years at least. That engine should now run happily for the next 7 seasons or so, but the valve train was a total unknown when it was built, in terms of longevity.
 
Slippydiff said:
As for your example of the BMW M3 engine, I think the specific output/maximum rpm of an engine has little to do with it's valvetrain durability and longevity.
(but the above are only my thoughts, and thus they're not gospel...) :)

The reason I used the M3 is that physically the dimensions of the valve train components are very similar to the ones found in the GT3. It is simple physics after all. The only major difference is that the M3 uses rockers while the Mezger doesn't. As to what causes valve train wear/problems - well aware of the causes/problems, given that I tend to build my own historic watercooled race engines with somewhat modified valve trains :mrgreen:
 
What a machine! Quality engineering and good taste in spades!

Thanks SlippyDiff for the write up, I really enjoyed reading it!

Interested what sort of spring rates these JRZ's run with.... :D
 
Proprietary info :hand:
 
Apologies for the lengthy delay in updating this thread. Firstly I've found myself embroiled with a ladeeee since the end of July, that's meant I've spent far less in front of my PC, let alone having the time to write further reviews on this amazing 996 ....

But what really brought a halt to proceedings was my dear mother falling and fracturing her hip on November 19th. Though the operation to repair the fractured hip went well, she subsequently contracted sepsis ten days later and fell seriously ill.

My sister I and feared for her life, so much so that I stayed with her overnight on the Thursday 30th November.

Large hospitals are strangely surreal places in the early hours of the morning, with only occasion whispers from members of staff checking BP, oxygen sats etc, or offering kindly cups of tea, coffee or sandwiches to break the long periods of silence. But periodically the tranquility is shattered by elderly patients crying or screaming out for help, all of which I found deeply unsettling when your nearest and dearest is critically ill and trying to rest..

Sleep wasn't an option, so I tried to pass the time bringing this review up to date, but also thought it a good way to take my mind off the inevitable.
My dear mother passed away shortly before midnight two days later on Saturday 2nd December aged 90.

In the best tradition of the English stiff upper lip mentality, onwards and upwards, life must go on ! ! Do please enjoy :

It's 3.30am on a fine Sunday morning in early September, and another pre-dawn alarm call urgently wakes me from my slumber.

Now I'd like to say the exciting thought of a stint behind the wheel of this finely honed Mk1 996 GT3 was the reason for my waking so early, but it wasn't. This early morning alarm call came courtesy of some poorly stored or cooked chicken from a well known Italian chain of high street restaurants. If you'd like to know which one, just PM me and ASK....

So with the world having fallen out of my bottom :grin: I grabbed another two hours sleep before getting up, showering and once again heading up to fine roads of N.Wales to test this phenomenal exercise in 996 GT3 honing.

Apologies for the hopeless images, they were taken in the shade and my iPhone 5S really isn't up to the job :coat:

G4JjXxY.jpg


j9NZh9o.jpg


yj4iqS5.jpg


Same location, far more talented photographer/better camera ...

s3gPiz8.jpg


The new owner has had the car three months now, and in that time has clocked up a good few miles.
Having passengered him on 3-4 occasions, it became clear he'd mastered the throttle response and clutch operation to the point he made driving the car look easy .......

So with the first leg of the route out to our usual breakfast stop complete and a hearty full English consumed, the new owner handed the key to me and says "it's you're turn now" .....

I tend to be pretty generous when it comes to sharing cars (with the caveat I need to feel the recipient of the keys is sensible, mechanically sympathetic, knowledgeable, can "drive" and understands what they're about to drive) and knowing the owner of this car gets emotionally attached to his cars, I felt incredibly privileged to given the opportunity to drive his truly unique and stunning car.

I'd taken the time to watch and study him driving the car (and as said previously, he made it look easy ! !) so what came next was a bit of a shock.

The car has a Cup flyweight flywheel (think 964/993 RS, Mk 1 996 GT3 Clubsport, then remove three kilos more... !!!) the flywheel in itself isn't a problem (I've owned all the above fitted with LWT flywheels) No, what made the process genuinely tricky was the unsprung paddle clutch ie a full race unit more at home in a race, sprint, rally or rallycross car .

A paddle clutch has one function, that being to transmit the engine's power as efficiently as possible without any slippage. Period. In reality that means they're not designed for road use or in traffic. They are effectively in or out, and very switch like.

They can be made to last on the road by avoiding riding the clutch when setting off or changing gear, but they're primarily designed for race circuit/rally stage use.

So that was the first hurdle to overcome, the next was equally tricky.

As I've mentioned before, this car runs some very trick, custom throttle bodies and a Motec management system (not to mention the exquisite carbon airbox pictured) As with most throttle body installs, this one was utilised primarily to liberate additional horsepower and ensure the magical 500hp brief was met. And whilst the throttle bodies are an important part of what is a symbiotic blend of parts (heads, cams, exhaust, engine capacity, and induction/management) they, long duration, high lift cams and large inlet/exhaust ports aren't the perfect solution for a road going car.

So whilst this engine and its driveability were perfected after many hours on an engine dyno (not a rolling road) the throttle response low down in the rev range, sub 2k rpm, still isn't perfect.

Pair the clutch with this less than progressive low down throttle response AND the flyweight Cup flywheel/clutch assembly and things start to get "interesting" especially for an individual as inept as my good self :grin: (actually I once owned an ex Prodrive Impreza WRC car, the second car they built after the one they'd built for the late, great Colin McRae) and that was actually easier to drive once you'd mastered the straight cut 'dog 'box ! ! !

But I digress, I wimped out and asked the owner to extract the car from it's parking space at our breakfast stop :hand: and once clear of prying eyes, I took to the drivers seat :mrgreen:

The gearbox is fitted with Cup cables and a 996 Cup shift assembly. Forget all the other short shift kits on the market (well except the superb and pricey Manthey billet shift assembly) this is THE best 996 shift you'll find, crisp and accurate whilst maintaining sensible throws AND weights. Added to which those peeking through the windows into the interior of the car won't think it's owned/driven by a complete boy racer, unlike the abominations from the likes of Numeric ....

The gearbox itself is a trick item, possibly a 2000 GT3 R or 2001 GT3 RS item (TBC) fitted with a Guard Transmissions (GT) billet LSD and probably a 8/32 crownwheel and pinion (TBC) and an external, front mounted oil cooler. Irrespective of its lineage, it transmits 500 NA horsepower to the Tarmac very, very efficiently indeed.

With each passing mile the JRZ dampers have become more compliant, and this along with the myriad rose jointed toe arms, castor arms and track control arms makes for the best handling 996 GT3 chassis I've ever driven. The suspension geo has been tweaked by danny at Unit11 and on Cup 2's in the dry the car goes where it's pointed, end of.

The finely crafted inconel and titanium exhaust is as quiet, if not quieter, than the standard exhaust, such was the previous owners insistence the car should pass every circuit's noise test. For a brief glimpse of the beautifully crafted masterpiece, watch this video at 27 seconds :

https://youtu.be/b6IQs4rEDw8

When cruising, the intake noise, the mechanical sound of the engine and the transmission (courtesy of the Cup gearchange cables) are more prevalent than any exhaust noise. But don't be thinking this is tiresome overly noisy car to drive, it isn't. Actually that's not true, the noisiest aspect of this car (apart form the induction noise) is those bloody Endless brake pads !! which squeal in protest every time they're used. And whilst there's no doubting their bite, nor indeed their ability to haul the car down from massive speeds with ease, time after time, they are ridiculously noisy.

But the ultra lightweight flywheel (and clutch) also impact steady state cruising on low throttle openings, the lack of any meaningful flywheel effect, means the the engine can fall off the cam and when it does so, it can get histrionic. It's straightforward enough to address though, you change down a gear and get the engine revs raised so it's back on the cam. It could be seen as downside, or you can view it as I did, that being it just adds to the car's incredible character.

I should add the owner has since carried out one modification to the car over the Winter (this review is based on my experience of driving the car early in September last year remember) and it has drastically changed the the drivability of the car to a degree you wouldn't think possible. But I'll update this thread with another driving review shortly (I promise it won't be another 6 months next time !!)

More to follow ....
 
Slippy, firstly may I say sorry to hear about your Mum, that can't have been easy for you and any other family members.

Secondly, I can sympathise with you finding a hospital ward to be a lonely, often scary place, having had a fifty one week spell myself back in 1989. The experience was quite sobering at times, but as you've said, it can give you copious time in which to think - very glad your mind wandered to Zanzibar again!

Thirdly, another great write up! :worship: It's funny, the boys at Center Gravity really rate the 996 platform over both previous and later versions, along with said platform's build quality versus the 997 generation. That opinion was from both Chris and Pete, and it certainly sounds like your friend's car is pretty well resolved.

One thing that may help the drivability is to convert it back to drive by wire (if it is indeed cable operated at present?), in order to soften the pedal/throttle progression. There are several ways to achieve this via a remote actuator, which then opens the throttle bodies. Failing that, a cam throttle works wonders, we have to do the same on the 2 litre V8 hillclimb motors as they are ferocious little blighters when on 1:1 :mrgreen:

Will the beast be gracing any tracks this year? Would be great to see it in action. Keep up the reports as and when you have driven it again.
 
Hi Mike, thank you for your kind words, they're much appreciated.
51 weeks in a hospital ? All joking aside, that sounds like my idea of a living hell.

Having been through aircooled 964 RS's and a 993 RS before getting myself into a 996 GT3, I thought the build quality of the first watercooled cars was pretty hopeless. But then I moved on to a Gen 1 997 GT3 and slowly came to realise the 996 was the high water mark.

Now I realise the 996 was the best engineered of the watercooled cars. As for the 991, best we don't even go there.

I think the 996 GT3 with it's Mezger engine is the perfect balance between the modern 997/991 cars and the 964/993 aircooled stuff. And when you look at the current aircooled prices, the 996 GT3 looks positively cheap/good value for money.

Chassis wise I think Porsche AG nailed it from a tactility and engagement perspective. They were (and still are) real drivers cars.

The Mk 1 996 cars were cable throttle, the Mk2 Egas, so this car came with a cable throttle and retains it.

I drove the car again last weekend after the owned had carried out a significant modification over the Winter, I'll write another report shortly to update on the throttle progression situation.
 
Slippydiff said:
Having been through aircooled 964 RS's and a 993 RS before getting myself into a 996 GT3, I thought the build quality of the first watercooled cars was pretty hopeless. But then I moved on to a Gen 1 997 GT3 and slowly came to realise the 996 was the high water mark.
Very sorry to hear of your loss. Hospital visits can be traumatic at the best of times. Like you, I prefer to stay away from them.

As regards the 996, I have absolutely no hesitation in saying I prefer the overall design and layout of the (admittedly retro) interior, over and above the 997.

The all leather interior (not ruched seats of course!) of my old 996 turbo was a lovely place to spend time. Trips across Europe were always a pleasure and never a chore. The 997 just doesn't look right - to me it looks bit Japanese somehow. The window switches are a total PITA too.
 
Slippydiff said:
The gearbox is fitted with Cup cables and a 996 Cup shift assembly. Forget all the other short shift kits on the market (well except the superb and pricey Manthey billet shift assembly) this is THE best 996 shift you'll find, crisp and accurate whilst maintaining sensible throws AND weights. Added to which those peeking through the windows into the interior of the car won't think it's owned/driven by a complete boy racer, unlike the abominations from the likes of Numeric ....


More to follow ....

Thank you very much for Part II particularly in the circumstances. There was me on the cusp of sending you a badgering PM to ask when the next write up was going to be :coat: . Now all that and a teaser for Part III.

I just thought I would mention the Numeric "abomination" as I bought the one from NXI20 which was further knocked by Matt of Fearnsport 'fame'. Unfortunately mine was initially poorly fitted by an independant Porsche 'specialist' but I do not have any issues with it now. I shall be able to comment further once used at the Nordschleife. All metal it is rather rifle bolt like but seems to be well crafted and lets face it you do not actually see it once fitted anyway. Numeric cables seem to be very similar to the Porsche Cup ones (think and direct in action) and I wonder if you were to fit the rubber cushioning from the OEM GT3 cables as I have, will this buffer the sound. I have not really noticed the increased noise with mine but I don't have a LWFW .... yet - not sure if this is a factor.

I have attached a picture of your exhaust artwork and was a little disappointed there was no sound track to accompany your new shiny system. Perhaps for Part III.

I think I along with others should join you for a drive around Wales to see and hear it all in action. Perhaps once the snow stops and the sun shines. :thumb:

Pip
 

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Slippydiff said:
I should add the owner has since carried out one modification to the car over the Winter (this review is based on my experience of driving the car early in September last year remember) and it has drastically changed the the drivability of the car to a degree you wouldn't think possible. But I'll update this thread with another driving review shortly (I promise it won't be another 6 months next time !!)

More to follow ....

Two weeks left to keep it under 6 months.

MC
 
MisterCorn said:
Slippydiff said:
I should add the owner has since carried out one modification to the car over the Winter (this review is based on my experience of driving the car early in September last year remember) and it has drastically changed the the drivability of the car to a degree you wouldn't think possible. But I'll update this thread with another driving review shortly (I promise it won't be another 6 months next time !!)

More to follow ....

Two weeks left to keep it under 6 months.

MC

Busted. But in my defence, things are somewhat "tricky" with regards to the the current situation with the car :hand:
Rest assured a review WILL be forthcoming, and some :mrgreen: :floor:
 

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