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EGTE
Imola


Joined: 06 Jul 2015
Posts: 823



PostPosted: Wed Apr 12, 2017 10:57 am    Post subject: Reply with quote

Looks great.

Is it possible to turn a 3.6 into a 3.7 (by shortening the rods), then? Or are the engines just too different?
 
  
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Robertb
Dijon


Joined: 01 Sep 2003
Posts: 7108
Location: South Oxfordshire

2002 Porsche 996 Carrera 4S

PostPosted: Wed Apr 12, 2017 12:08 pm    Post subject: Reply with quote

EGTE wrote:
Looks great.

Is it possible to turn a 3.6 into a 3.7 (by shortening the rods), then? Or are the engines just too different?


I'd imagine whilst he's retained the original 3.4 heads, he's had them bored out to increase the capacity, plus fitted bigger pistons, unless I have the wrong end of the stick.
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MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7069
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Wed Apr 12, 2017 12:18 pm    Post subject: Reply with quote

Different liners and pistons for larger capacity, not sure of the details on the head.
I am suprised that this isn't done more often if people need a rebuild. If ever my 3.4l engine needs a rebuild this is what I will be doing. In fact, it is something I might consider anyway with a spare engine I have.

MC

Last edited by MisterCorn on Wed Apr 12, 2017 12:44 pm; edited 1 time in total
 
  
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Jay.
Montreal


Joined: 20 Oct 2015
Posts: 561
Location: Brize Norton


PostPosted: Wed Apr 12, 2017 12:38 pm    Post subject: Reply with quote

Excited for the figures! worship
 
  
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poppopbangbang
Nürburgring


Joined: 25 May 2015
Posts: 480



PostPosted: Wed Apr 12, 2017 9:41 pm    Post subject: Reply with quote

EGTE wrote:
Looks great.

Is it possible to turn a 3.6 into a 3.7 (by shortening the rods), then? Or are the engines just too different?


No, in short Smile If you shorten the rods you will still have a 3.6 just with a lower compression ratio.

3.6 and 3.4 share a common bore, the 3.6 just has a longer stroke crank. If you do the same as I have done (100mm bore) on a 3.6 then you'll get a 3.9L motor, although as I mentioned in my earlier post I didn't want to go 3.6 crank in mine as I wanted to keep the piston speeds low, the pistons I am using are lighter than the OEM ones so rod loads are actually lower now than the were as standard.
 
  
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poppopbangbang
Nürburgring


Joined: 25 May 2015
Posts: 480



PostPosted: Wed Apr 12, 2017 9:54 pm    Post subject: Reply with quote

crash7 wrote:
PPBB

Off-topic, could I ask what ride heights are you running on your car?, taken form the Porsche suggested points.

How close is your FVD oil pan to the floor with those heights?

Cheers


It is max allowable for a Mk1 GT3 so 112mm front and 135mm rear. This gives me 10mm either side of this to play with as needed but in reality it tends to stay at these heights, the slightly less rake than a GT3 usually runs helps a little with stability on the road.

The pan very rarely scrapes anything, mainly because the exhaust manifolds are lower than the pan by about 10mm so tend to act as useful mechanical bump stops. The car also has quite a bit of low speed compression damping in the rear shocks which helps to avoiding it loosing too much heigh over speed bumps and pot holes.
 
  
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poppopbangbang
Nürburgring


Joined: 25 May 2015
Posts: 480



PostPosted: Wed Apr 12, 2017 10:01 pm    Post subject: Reply with quote

Marky911 wrote:
Looking good poppop. Good to see it's back.

What benefit does the Motorsport AOS have please? And how does it compare price wise? I know most Porsche Motorsport parts are usually cheaper.

I'm interested in the IMS bearing goes as the roller type is top of my list should I need to change mine.


The Motorsport AOS is a twin chamber design with more capacity than the standard item which amongst other things means it avoids the smoke on circuit with sticky tyres that sometimes happens with the standard AOS. Apparently they are a bit more reliable too but I think that is mostly anecdotal as I doubt the KMs have been done on the Motorsport version to validate that against the standard part!

Image from Rennpart:
 
  
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toohey
Monza


Joined: 22 Jan 2009
Posts: 191
Location: Naarfolk


PostPosted: Thu Apr 13, 2017 7:31 am    Post subject: Reply with quote

poppopbangbang wrote:
Marky911 wrote:
Looking good poppop. Good to see it's back.

What benefit does the Motorsport AOS have please? And how does it compare price wise? I know most Porsche Motorsport parts are usually cheaper.

I'm interested in the IMS bearing goes as the roller type is top of my list should I need to change mine.


The Motorsport AOS is a twin chamber design with more capacity than the standard item which amongst other things means it avoids the smoke on circuit with sticky tyres that sometimes happens with the standard AOS. Apparently they are a bit more reliable too but I think that is mostly anecdotal as I doubt the KMs have been done on the Motorsport version to validate that against the standard part!

Image from Rennpart:


I had the motorsport AOS on my previous 996..... it failed at around 40K and 6-7 years old. Sad the problem was then trying to find another as the Reg number showed a standard AOS but i think from memory the garage said the pipes were in different places?.... Whatever I'm not sure its the cure to all AOS woes - maybe i just had a duff one!
 
  
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skinny_monkey
Nürburgring


Joined: 16 Sep 2014
Posts: 429



PostPosted: Fri Apr 14, 2017 9:54 am    Post subject: Reply with quote

poppopbangbang wrote:
EGTE wrote:
Looks great.

Is it possible to turn a 3.6 into a 3.7 (by shortening the rods), then? Or are the engines just too different?


No, in short Smile If you shorten the rods you will still have a 3.6 just with a lower compression ratio.

3.6 and 3.4 share a common bore, the 3.6 just has a longer stroke crank. If you do the same as I have done (100mm bore) on a 3.6 then you'll get a 3.9L motor, although as I mentioned in my earlier post I didn't want to go 3.6 crank in mine as I wanted to keep the piston speeds low, the pistons I am using are lighter than the OEM ones so rod loads are actually lower now than the were as standard.


Oh I had no idea - I thought the 3.6 was bigger bore hence why it was more susceptible to bore score and ovalling
 
  
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bazhart
Approved Trader


Joined: 20 May 2009
Posts: 947
Location: Bolton Lancashire


PostPosted: Fri Apr 14, 2017 12:14 pm    Post subject: Reply with quote

I can confirm that extra mid range is quite significant. We are currently road testing a 996 3.4 converted to 3.7 (100mm pistons), a 996 3.6 converted to 3.9 (different 100mm pistons) and a 997 3.8 converted to 3.9 (same pistons as the 3.6) - all with Nikasil alloy cylinders.

We will also be building a 3.2 Boxster S into a 3.7 and Cayman S 3.4 etc using many common parts for our oversized engine range (just need to finish testing the others before moving them on so we can get in the other models we intend to offer in the range).

All testing is going well and we hope to be taking orders later in the year.

Although it is theoretically possible to change the 3.2 and 3.4 engines right up to 3.9 (or more) to do it reliably would require many more parts to be changed and updated at significantly greater cost for relatively little extra performance and after all that you would question the brakes and suspension etc - so for now we are limiting our future conversions to those ranges.

Also in build a Gen 2 - 4 litre car - something for next winter perhaps?

Baz
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EGTE
Imola


Joined: 06 Jul 2015
Posts: 823



PostPosted: Fri Apr 14, 2017 4:15 pm    Post subject: Reply with quote

You're such a tease, Baz Hand

Good info as ever, though.

Seems like the longer my engine keeps going (perfectly), the bigger the replacement displacement! will be Grin Cops
 
  
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Dammit
Watkins Glen


Joined: 23 Sep 2016
Posts: 2199



PostPosted: Fri Apr 14, 2017 4:32 pm    Post subject: Reply with quote

I'm planning on a prophylactic rebuild at around the 80ish thousand mark for my engine - and yes, I know what thread I'm posting in, and that I'm clearly lacking moral fibre etc etc, but I'd rather it be done and out of the way as it were. I had a chat with a chap from Hartech (not Baz) a month or so about it and the 3.7 litre option (I've a 1998 3.4) certainly seems to make sense.
 
  
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911munKy
Montreal


Joined: 26 Nov 2014
Posts: 521



PostPosted: Fri Apr 14, 2017 5:23 pm    Post subject: Reply with quote

I'm going to wait until I've also done 1/2 million Km's until my 3.7 build.
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Poker2009
Österreich


Joined: 09 Sep 2009
Posts: 899
Location: London


PostPosted: Sun Apr 16, 2017 6:22 am    Post subject: Reply with quote

bazhart wrote:
I can confirm that extra mid range is quite significant. We are currently road testing a 996 3.4 converted to 3.7 (100mm pistons), a 996 3.6 converted to 3.9 (different 100mm pistons) and a 997 3.8 converted to 3.9 (same pistons as the 3.6) - all with Nikasil alloy cylinders.

We will also be building a 3.2 Boxster S into a 3.7 and Cayman S 3.4 etc using many common parts for our oversized engine range (just need to finish testing the others before moving them on so we can get in the other models we intend to offer in the range).

All testing is going well and we hope to be taking orders later in the year.

Although it is theoretically possible to change the 3.2 and 3.4 engines right up to 3.9 (or more) to do it reliably would require many more parts to be changed and updated at significantly greater cost for relatively little extra performance and after all that you would question the brakes and suspension etc - so for now we are limiting our future conversions to those ranges.

Also in build a Gen 2 - 4 litre car - something for next winter perhaps?

Baz


Great news for the smaller engine cars, but owning a 3.8 - I would hope (and I am sure I am not alone) for at least 4.0 or 4.1 - wouldn't that be the sweet spot? Smile

I think people will at least feel they are getting an upgrade, rather than spending so much money on a "repair" - this definitely the way to go Baz thumbsup
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63k miles, tiny IMS bearing, Millers NT+ 10W50, driven above 3000 RPM.. original engine.
 
  
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bazhart
Approved Trader


Joined: 20 May 2009
Posts: 947
Location: Bolton Lancashire


PostPosted: Mon Apr 17, 2017 9:56 am    Post subject: Reply with quote

The problem is that although the same basic parts and design of the smaller engines are also in the 3.8 - it is the model we repair the most of and as such too big a capacity increase may be reflected in unreliability.

Our capacity increases are largely for people who need a repair anyway and therefore will be offered more or less as a benefit for very little extra cost.

The Nikasil alloy cylinders will take bigger pistons and more power but the crankshaft journals from the 3.8's do show wear sooner than smaller engines and we are intent on preserving reliability combined with extra performance.

Once we have got some miles under our belts with the present range - depending on how they perform - we may well try a further capacity increase but probably with a new crankshaft and rods (as we perceive this to then be the probably Achilles' heel) = more cost - by which time owners may well be more prepared to pay for such an upgrade.

We always test our products for long periods and high mileages before offering them to the public and although this may be frustrating for some (as it actually is for us) we regard it as a responsibility we have to fulfil.

Baz
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kas750
Reims


Joined: 31 Mar 2013
Posts: 4476
Location: Chorley lancashire

2006 Porsche 911

PostPosted: Mon Apr 17, 2017 11:48 am    Post subject: Reply with quote

poppopbangbang wrote:
Dammit wrote:
Great news, did the rebuild come in according to your budget?


Yes no surprises or dramas. Autofarm were great to deal with, as they always have been in my experience. I think we were a bit under budget in the end.

Agreed Autofarm are a great company to deal with. Thumb
 
  
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poppopbangbang
Nürburgring


Joined: 25 May 2015
Posts: 480



PostPosted: Mon Apr 17, 2017 4:01 pm    Post subject: Reply with quote

Preliminary Results

So with around 1200 miles on it now I thought it was time to see where we were in terms of power compared against the previous engine. Now the below is fairly accurate, even when compared to what a direct measure would be, but it's very reliant on the figures you are plumbing into it. It's really a system we use to monitor how the engine health is doing over life in a racing car but it does provide repeatable results and obviously having some 200K miles of data to compare it against is the important thing for measuring a gain. The below is based on linear acceleration over time to determine the wheel power developed to move the specific amount of mass with the specific amount of aero drag at the measure rate of acceleration.

It's fairly simple stuff, firstly we calculate the power absorbed moving the car through the air at the current speed which we can do by knowing the frontal area of the car and the drag coefficent along with the speed in metres/second. Once we have this value we can then calculate the wheel power of the car (it's important we know aero drag or the resulting figure would be vastly different for a given RPM in first gear vs 6th gear due to the greater vehicle speed), to do this we need to know the mass all up (so with fuel, driver, additional kit etc.) which I have from time spent on the corner weight scales along with the linear acceleration of the car - linear acceleration being essentially the rate of change in velocity. For the sake of accuracy we are using a 10hz GPS to determine the start and end velocities and validating this with a longitudinal G measurement i.e. to accelerate from X to Y speed in a certain time has to have yielded an average accelerative G of Z so if our measured G is vastly different at one point or our measured average G between the points doesn't match our calculated average then we disregard this measurement as flawed. To get to flywheel power from wheel power we use a simple formula based on a known measure of wheel power against a known OEM SAE corrected engine dyno result, in this case what my car made as a standard 100 and a bit thousand mile car vs Porsches 300PS no aircon, no PAS, engine dyno rating. It's a sliding scale based on torque produced but at peak power the total loss between flywheel and tyre contact patch is about 14.8% by my math.

It might all sound a bit math heavy but with a decent logger you can do this live on the box and it's pretty much the same system we used in pro motorsport in the days before we had reliable and long lived drive shaft torque sensors.

So here is where we have ended up from testing today. This is an average across 12 runs with 6 in each direction to account for the slope of the runway:



According to this it's making 363.2bhp at 6250RPM and a peak torque of 318.8ftlbs at 4750RPM. What's nice is that it makes over 300ftlbs from 3500RPM to 6200 and a bit RPM. It is quite clearly all done by 6.5K and torque drops away rapidly here to the rev limiter at 7200rpm.

Lambda is fairly good considering the ECU calibration is pretty much standard. There is something odd going on at mid RPM in low gears where the ECU is winding the throttle down during 100% PPS which is likely to be the result of a torque limiter somewhere being exceeded (not surprising all things considered!) and performance could clearly be found by going richer below 4500RPM, at the moment the ECU is staying in closed loop mode until this point to keep the cats happy (which is fairly pointless as mine hasn't had cats since 2013).

Gains wise when compared against the old engine (and that is compared using the same math as determined this engines performance so it is a good comparison!) this engine is about 30ftlbs and 25bhp up on it when the old motor was at its best with considerably more torque at lower RPM - indeed the additional low RPM torque is far more than I would have thought would be gained by going up a relatively small amount in capacity, it's likely there are some improvements in cylinder filling at lower port velocities/engine speeds as a result of the larger bore/swept capacity.

For those interested the full spec of this engine is:
- Autofarm 3.7L castings.
- Autofarm cylinder heads
- CP Pistons in standard C/R with reduced size skirts for friction reduction.
- Standard size inlet and exhaust valves.
- Standard Cam Shafts
- Variocam fitted and working.
- Cams timed to Autofarms spec for 3.7L
- FVD Equal length exhaust manifolds
- Cat delete crossover pipes.
- No name perforated tube stainless silencer boxes (I think these are the same as D911, Porscheshop etc. sell).
- 996 GT3 Throttle Body
- Slightly hooky IPD plenum to suit the above
- 997 Airbox
- Large diameter silicone hose to suit the above joint to the GT3 throttle.
- No Secondary Air System
- No Air Con Compressor.
- ECU Calibration is essentially standard but with lower fan on temps etc.
- FVD Large Capacity Sump (not that this really has any effect on power)
- Low Temperature thermostat (as above)
- Metal impeller water pump (12 months life) (as above)
- Roller bearing IMS (as above)

It will go on a dyno at some point in the near future as it's very clear there is more to be had from some engine calibration development (not least solving the torque limiter problem that rears it's head when launching the car hard) and the instant 30 second feedback a chassis dyno provides when doing this does rather minimise the time required. It's also pretty clear the cams that are in it are probably too soft for an out and out performance engine as the additional low RPM torque could be traded off for high RPM power, however as my car is 99% a road car and the lower the revs the longer the engine life I'm quite happy setting the last shift light at 6.5K RPM Very Happy

For those interested in how I'm logging this data the car has an AIM EVO5 logger onboard with two LCU-One wideband controllers, a GPS08 GPS/Glonass receiver and a GS-Dash (with motorsport cable tie mounting!). It takes basic data from the car via OBD2, RPM from the tach signal at the OBD2 connector and oil pressure on a dedicated sensor.

To sum up - I'm rather pleased with how the old girl goes now and it would be interesting to see where we are vs a 996 Mk1 GT3 Very Happy
 
  
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16369
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Mon Apr 17, 2017 4:06 pm    Post subject: Reply with quote

Bow Bow Bow Bow
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maldren
Suzuka


Joined: 07 Oct 2016
Posts: 1100



PostPosted: Mon Apr 17, 2017 4:34 pm    Post subject: Reply with quote

Agree Wot he said, I think I want one of those engines.

Mike
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2003 996.2 C2 Coupe Arctic Silver
 
  
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Dammit
Watkins Glen


Joined: 23 Sep 2016
Posts: 2199



PostPosted: Mon Apr 17, 2017 8:49 pm    Post subject: Reply with quote

PPBB - what do you think the power and torque would look like if you had standard throttle body/manifolds/catalytic converters still in place?

I know that you moved all of this over from the old engine, but wondering what the delta would be for a stock 3.4 to 3.7 conversion.
 
  
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