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Trials and tribulations of a Porsche tuner..

Indi9xx

New member
Hi, I am Jon Mitchell and I am a Porsche Tuning addict...

My only experience of self help groups is on TV and they seem to be people sat around in a circle introducing themselves and saying "and I am an alcoholic" or "and I am a drug abuser"

Looking back over almost 30 years of my career to date, I do feel like I have had an addiction, or at least I have been doing something over and over again, which brings myself some emotional reward, but in the process destroying my finances, health and free time. Let me explain..

30 years ago it was inevitable I would become a Porsche specialist, even though I had resisted and was educated in science and software engineering initially, my father was a great Porsche specialist and so it was no shock when I became one under his wing..

Once my father retired, my training continued funded by some wealthy people in the middle east, who brought enough cars from the factory, that I ended up factory and factory motorsport trained. I also had a background in thermodynamics, Physics and low level programming languages, so it was no wonder I understood those new fangled Porsche with their microchip voodoo gubbins as my dad would call it (normally before saying something like "what was ever wrong with a carb, points and condensor??")

The business relocated to the UK about two decades ago, and grew, took on staff, and grew some more.. But one thing was constant, I was always a sucker for a project, someone wanting to transform their Porsche.

Often these transformations would involve not only some major surgery, but also an evolution of the project, where while the customers car is being worked on, they also come up with some ideas of other bits they want to do, or we find out the car they want to do it to has some serious issues that also need addressing.

We have always been a bit of a victim of our own success, the workshop is always very busy with servicing, diagnosis, repairs and straight forward modifications... Often booked up for 4 to 6 weeks in advance.. But the big projects always cause a problem, especially when they evolve, such as a car coming in for a chip and later turning into a car with a rebuilt engine, chip, maf conversion, big turbo, exhaust, intercooler, suspension package and a million and one faults rectified along the way, usually also with a customers budget evolving also.

In the past, I always was, as mentioned before, a sucker for a project, this meant that often I priced them low because I was not only wanting the customer to have the best car, but also because often the customer could not quite afford what they were asking for... So typically every project turned into a loss.

The other problem was the workshop being booked up for 4 to 6 weeks in advance, this meant that a car coming in for chips but needing (for example) a head rebuild by the time we checked it out, would not have the time to do the work there and then, meaning the extra work would often happen a month later, or sooner if we had the time.. Normally customers are completely aware of this, and each time they add to the project, with each decision potentially adding another month to the time scale, they should still be aware of this, but others often do not know...

But it does mean, over the years, when a customer comes on a forum like this and says "My car is at JMG having this..." and then a month later says "And now it is having this" and this story goes on for ages, it is not a shock that these days people in the community have an ongoing joke of "Your car is at JMG? Oh, you will have it back in two years!".

While on one side, it is often said as a joke, at the same time, it still isnt good for business and people who do not know the ins and outs, may think that we keep peoples cars here captive for months on end, not realising, that we really are always booked up in advance, and finding the extra time for X, Y or Z additional jobs, after the car is here can be a problem.

The other problem is often that customers start reading forums like rennlist and insisting, part way through a project that we use XYZGoofBallTuning's turbo, exhaust, suspension or whatever.. and that is when things really turn pear shaped.. You would think a turbo is a turbo? A maf kit is a maf kit? a clutch is a clutch... But those parts, so often are not as "plug and play" as the vendors and fans of the vendors will say... Meaning those modifications no longer take as little time as expected for one of our own products, but then take forver with parts being fabricated to make X fit with Y.. Then only to find later that the cheap part really is quite useless anyway.

So, why am I saying all this??

Well of course I want to put the record straight, with some of those that joke or jibe on here about cars being here for 2 years.. I can only think of one car which was here for two years, and that was complicated and included designing the worlds first 3.2 944 Turbo engine.. Another car was here for ages because the owner was adamant that his UK made 3.0 exhaust would flow as well as a Fabspeed and insisted that the detonation problems were not down to the exhaust, until eventually we modified his exhaust and rectified the problem.. Other than that, sometimes a car is here for a long time due to a combination of it ending up having much more done than the original booking, combined with our fully booked diary.

Another reason is because I was taking part in someones post, where they were putting together a project, quite a major one, with lots of parts from lots of sources and a feeling of complete dread came over me, as I have felt the pain all too many times of what happens when you have multiple suppliers go faster goodies all coming together in one Frankenstein car... It becomes a nightmare and where do you point the finger of blame when none of it fits, or something goes wrong.. So I guess just a bit of a warning tale that even specialists who have done this work a thousand times, even get unstuck with big projects and lots of suppliers parts which have been cherry picked from packages which work, when one supplier supplies just that, a package.

The last reason, is like an addict, who has been suckered into one too many projects which have gone pear shaped and almost bankrupted me over and over again, I need to admit my addiction openly.. You are
my support group and here is my confession, I need to recover from my addiction..

What is the solution for me?

I have learned my lesson.. From now on I will only fit parts that I have developed an know, or ones which I know work, R&D will be on my own cars for fun, no more customers throwing down the gauntlet of a challenge and me accepting it and developing something bespoke for them.. and I need to be stricter with my customers and to not let their cars evolve in my workshop, their cars need to become tip top first, then come back for tuning with a clear vision later... Most of all I need to control my desire to say "yes" when they say "Can you also..." once the car is already here...

My name is Jon Mitchell, I am a tuning addict, but I am recovering, one step at a time... Please don't fall into the same traps as I have.


 
I always enjoy reading your threads John, I'm glad I sat down with a biscuit and a brew to do so [:)] you are a perfectionist and an addict which makes it hard for you to say no. Tell me though do you have some new R&D planned for your cars ?
 
blade7 said:
You Potton Road boys are always complaining about something ...


It's not just Potton Road Paul, hate to break it to you, it's all of St Neots from the tone of your posts! :ROFLMAO:

 
Indi9xx said:
blade7 said:
You Potton Road boys are always complaining about something ...


It's not just Potton Road Paul, hate to break it to you, it's all of St Neots from the tone of your posts! :ROFLMAO:


I learnt that from all the Ernulf girls [;)].
 
944Scott said:
I always enjoy reading your threads John, I'm glad I sat down with a biscuit and a brew to do so [:)] you are a perfectionist and an addict which makes it hard for you to say no. Tell me though do you have some new R&D planned for your cars ?


I have a massive amount of half finished projects in my messy lab that I never had the chance to finish, a MAF/MAP kit with proper inlet air temp correction and some lovely software through to dash night illumination kits which made it onto a couple of customer test cars, but never turned into a product, some software for the 944 DME to seriously increase fuel efficiency rather than tuned to emissions (not tested but sound concept), fuel coolers, intercooler redesign and much much more...

More recently I made a bit of a choice, spend some time finishing off those bits for a market which is shrinking, or get deep into Boxster ECU's (not just the engine management one) and unpick their mysteries and potential, which has been really interesting and rewarding, but not sure how it will terminate into products yet.

Also been playing with turbocharging Boxsters, properly, not one of these half baked ones like the many kits out there, but a proper bullet proof bottom end, low compression, big turbo, big boost project.. But can't move forward until I have finished lock picking the engine management on those cars...

More recently my head has been turned by the idea of buying a 718 Cayman and seeing what can be done to it... The first car which has actually excited me out of the Porsche factory for years and the potential to blow the doors off of the GT4 or to be honest the GT3 or GT2 in theory..

But thats the point, I need to spend some more time on those and less time becoming entrenched in customers getting out of hand.. I think customers projects need to be simplified and need to be "Here are some products, pick from them" rather than "Yes buy that cheaper turbo and we will see what we can do with it", which always turns into a nightmare and many many hours unpaid.

If I won the euro-millions, I have my eye on a nice lake in Turkey, where I will build a nurburgring type track around the outside of it, a big air conditioned development facility on the side of it, and spend my days just tweaking and developing, with a few choice employees as machinists, composites guys and electronics people and just play and release the odd amazing product.

 
Jon you are a true gent and one of the nice guys in a minefield of an industry. Your time is precious and you rightly realise some change of direction could ease your sanity and most probably be beneficial moving forward. I think i speak for most on here when i say you are well trusted and respected in the 944 community and certainly in my few dealings with you i can say i have nothing but admiration for your approachability and wealth of knowledge. You kindly sorted out a valuation for me and also greatly assisted with a niggly maf issue which got sorted after some ideas you gave me.

I'm sure your addiction can be controlled and channelled positively in the future.

Cheers

Stuart
 
+1 to Stuarts comments..it's many years sinceI I first met you Jon, I can't remember the venue, but it was held at a colleage, it involved titanic members and you did a demostartion on 944 timing/balance belt fitting... fond memories...:)

regards

Pete
 
Hi Jon,

I've moved the content from the other (Rods & Piston upgrade) thread that we were discussing
on harmonics etc...if you can continue your thoughts and explanations please.
questions in RED.
----------------------------------------------------------------------------------------------------

924srr27L
You mention harmonics are a problem with 104 bore engines, I think mine after a LR hone was close
to 105 and uses Wossner Pistons, but it's not on the 3.0S2 long stroke crank but a 951 2.5 version hence 2707cc.
The crank is 3kg less and the Fly 4.5kg less, and it's runs very well and so smooth.
From the cockpit there are no vibrations felt at all at any RPM, The crank and Fly were balanced as were the pistons & Rods etc..Wayne Schofield also spent 6 + hours mapping the car at ninemeister.
What exactly is the potential harmonic issues here? is it not something that can be felt, but will just fail at some point, or after a certain amount of mileage ?
Would you say the engine's very under stressed with Normal aspiration and 205bhp and could easily be changed to turbocharged with 50% more power and with all the same internals?


John Mitchell
The first time I became fully aware of the harmonic issues in these engines was during meetings with Capricorn (then Dover Group and Perfectbore) where we modeled and simulated the 100 and 104mm engines with the view of building 108mm bore engines for the 944 turbos.
With this we found that the reason Porsche had used such a heavy crankshaft was not just to strength but to act as a big harmonic dampener to move the resonant frequencies of the reciprocating mass beyond the rev range of the engine, in models where the crankshaft was lightened, those harmonic frequencies decreased causing the block to flex, which is why on the 3.2 engines we ended up using interlocking wet liners and brass alloy rings instead of a head gasket to make the engine as close to a closed deck engine as possible.
Decreases in crank/flywheel weight, and any increase in rod and piston weight resulted in the resonant harmonic frequencies becoming lower and towards the used rev range of the engine, which is not something that would probably be felt inside the cockpit, but something absorbed by the engine mounts and meanwhile causing issues for the engine.
Apart from the head to block join fretting due to movement, concerns were that that high frequency vibration and potential flex in the block could have knock on effects beyond the typical cracking oil pickup tubes, but also for the oil pump (as it straddled the block and girdle), rigidity of the main bearings (altering clearances) but beyond that other potential issues of oil and fuel cavitation which makes them more difficult to manage.
One of the problems was that I wanted the engines to be as reliable as a standard 2.5 turbo would be, which was making a rod for my own back, whereas in todays reality a modified 944 turbo is unlikely to be cranking up high mileages as they did back then... I wanted the engines to still be great in 100,000 miles or double that, even with the performance.
In reality, if I was happy with the potential of an engine not lasting that long, I probably would not have been so worried about it, but the people who I were meeting with design engine blocks for the likes of F1 teams at one end of the scale (where they accept a short lifespan) and AMG at the other end who expect the engine to last 150,000 miles and my application being more road based, their advice was based more at the AMG end of the spectrum than the F1 end.
I doubt any of the 3.2's have covered 20,000 miles in the last 10 years, maybe even half that, so I was probably being overly cautious.. However, it is something that people need to make their own choice about with their eyes wide open, which is the only reason I mentioned it as a potential issue.



[FONT=verdana,geneva"]Ok thanks, I would return to my 2 Engine tuners & builders (USA & UK) should any issues ever occur, but my capacity is 2707cc not 3.2, or is it turbocharged but a Normally aspirated 8 valve.

You've mentioned:[FONT=verdana,geneva"]

[FONT=verdana,geneva"]
Jon Mitchell
Decreases in crank/flywheel weight, and any increase in rod and piston weight resulted in the resonant harmonic frequencies becoming lower and towards the used rev range of the engine,
[FONT=verdana,geneva"]

[FONT=verdana,geneva"][FONT=verdana,geneva"]My engine does have a lighter crank and flywheel, but the rods and Pistons are not increased but lighter than the original standard ones, does this still mean the frequencies are in the usable rev range ? and what range is this?

I don't hold any gear no more than 5700rpm (even on a track) as the peak torque is 4500rpm and peak bhp 5700rpm, the torque figure at 3500rpm is exactly the same at 5700rpm. (185 Ft Lbs)

Do these frequencies / Vibrations happen below 5800rpm?

Surely 250kg less vehicle weight help the engine's job? (Less mass to pull)

R
www.924srr27l.co.uk
http://924srr27l.co.uk/wp-content/uploads/2015/05/TEch-Spec-924srr27L-.pdf
[FONT=verdana,geneva"]
[FONT=verdana,geneva"]

 
Thanks guys,

It was mostly, "If I put it in writing, then I will be more likely to do something about it".

924Rss271 - Will pop back into that thread an answer for you. But in short, altering the crank, flywheel, rod or piston weight, either up or down, altered the natural harmonic frequencies of the assembly with different effects, I doubt you will have any problems with your configuration, but if you do have any issues which do not make sense, knowing about the harmonic issues may give you a head start. And the engine will be very lowly stressed in your application, I have had 2.5 8v NA engines at those kind of power levels without issues, closing the top deck or block filling the waterjacket around the bores will help as well.
 
Indi9xx said:
Thanks guys,
It was mostly, "If I put it in writing, then I will be more likely to do something about it".
924Rss271 - Will pop back into that thread an answer for you. But in short, altering the crank, flywheel, rod or piston weight, either up or down, altered the natural harmonic frequencies of the assembly with different effects, I doubt you will have any problems with your configuration, but if you do have any issues which do not make sense, knowing about the harmonic issues may give you a head start. And the engine will be very lowly stressed in your application, I have had 2.5 8v NA engines at those kind of power levels without issues, closing the top deck or block filling the waterjacket around the bores will help as well.



Ok, When you say "altered the Natural harmonic" in regard to the weights of the pistons, rods, crank & Fly etc...

Does Natural mean the Porsche calculated weights of every standard component? which should anything be changed lighter or heavier will affect this balance?

Did the 2.5 / 2.7 & 3.0 and even 968 have different Balance shaft weights do you know?

My engine is made up of a wide mixture of different engines (2.5 crank & Cylinder Head / 3.0 Block / 968 Rods & aftermarket forged Pistons) plus the extensive engine lightening , and one weighted Balance shafts, redesigned shorter Inlet manifold, Turbo Exhaust manifold & a 274 duration Camshaft from California.

All on stock Bosch fueling and Ignition AFM / Coil etc..

Surely such a configuration would be an ideal candidate to be out of Sinc? Or has all the Balancing (Crank & Fly / Rods & Pistons) eradicated this possibility only you say you "doubt you will have any problems with your configuration" ? [/i]

You've had over 200bhp with a 2.5 Normally aspirated engine ?

Is this for a Racing or road car?

That's a fair achievement regardless , which to my knowledge is not easy to find.
There's one company I know who offer many tuning components and services on the transaxle's and they did some work on
a Customer's car (2.5 8v) which started life dyno'd at 144bhp

After a lot of items (ECU Upgrade, Wasted Spark Ignition, ASNU Injectors, AFM Delete, Modified Airbox, Piper Racing Camshaft and
Dyno mapping etc..over ÂŁ2200 found 13bhp!

The same engine then had a rebuild with Steel liners and the fresh Internals found approx another 18bhp
total 175bhp for this road car.

They also recorded 187bhp @ 6200rpm on another 2.7 Engine used for Competition with all the above items & a Racing Camshaft.

Is it a secret how you found 200bhp+ on a 2.5 8v ? if not I'd be interested to know how you achieved this and if it was also running stock fueling and ignition?

R
www.924srr27l.co.uk





 
By the natural harmonic of the engine, what I should have said in easier terms is the normal resonant frequency and the point at which harmonics of that frequency become a problem.

The problem should be broken down into two different main assemblies, the resonant frequency of the block and cylinder head assembly and the point at which harmonics cause issues, and the flywheel, rods, crank and pistons imbalance of mass/energy, to an extent their resonant frequencies and how harmonics come into play. The real problem comes when you have crossovers between those two assemblies and how they interact and how flexible they really are to absorb the energy combined again with their mass and the effect of the undesirable energy.

Secondary to that is the resonant frequency of items like the oil pickup tube, to pick an easy one, which can deal with low frequency vibration, but at their natural harmonic frequency will crack at their weakest point, which is about 70hz, which unfortunately also comes at the same point of one of the harmonic phases of the engine, which is partially damped by the balance shafts.

One of the reasons Porsche made the water jacket a little more shallow in the 968 blocks was to add rigidity but to also alter the resonant frequency of the engine, likewise, balance shafts and hydraulic engine mounts were also there to absorb some of this energy, not only for the driver, but also for the engine.

However, I am not the expert on this, much of this was tested and simulated by some of the engineers at Dover Group / Perfect Bore / Capricorn, modeling the different engine blocks (100mm and 104mm) and cranks (2.5 and 3.0) with various piston, crank, con rod and flywheel options. The software they used for much of it was the Riccardo suite (which I wish I could afford!) being used by several people with degrees in those particular fields, I have just benefitted what was learned from those meetings in the early days which led to the development of our 3.2 944 Turbo engines, for which we tested many configurations of bore and strokes and combinations of internals looking for a perfect mix. The real shame is that everyone who had one realised that there was enough power as they were, because the next phase was going to be development of an intake manifold to match the engines, which never happened as no one wanted it.. Quite mad really.

The 2.5 NA outputs quoted are all flywheel figures (not corrected by on a chassis dyno, but engine dyno) but they were a bit of a disappointment, as the golden goose we were looking for was 100 bhp per litre. But we did not have to go crazy looking for it and I am sure it would have been possible to hit the 100/litre mark with time, money and development.

It would be easier to get more power by increasing the rpm abilities of the engine, however the oil pump cavitates not far above 7500 rpm and the higher you go, the worse the collisions of harmonics would become.. Dry sump would have cured the oil cavitation issues, but the harmonics again become an issue.. Although pistons on a serious F1 diet, along with Ti rods, closed deck block and a lightweight all steel crank could have been made to work together, which in themselves would have released power... But that is the money and development side which was not ever going to be economic or translate into something customers would want. Which is sad but true.
 
Indi9xx said:
By the natural harmonic of the engine, what I should have said in easier terms is the normal resonant frequency and the point at which harmonics of that frequency become a problem.
The problem should be broken down into two different main assemblies, the resonant frequency of the block and cylinder head assembly and the point at which harmonics cause issues, and the flywheel, rods, crank and pistons imbalance of mass/energy, to an extent their resonant frequencies and how harmonics come into play. The real problem comes when you have crossovers between those two assemblies and how they interact and how flexible they really are to absorb the energy combined again with their mass and the effect of the undesirable energy.
Secondary to that is the resonant frequency of items like the oil pickup tube, to pick an easy one, which can deal with low frequency vibration, but at their natural harmonic frequency will crack at their weakest point, which is about 70hz, which unfortunately also comes at the same point of one of the harmonic phases of the engine, which is partially damped by the balance shafts.
One of the reasons Porsche made the water jacket a little more shallow in the 968 blocks was to add rigidity but to also alter the resonant frequency of the engine, likewise, balance shafts and hydraulic engine mounts were also there to absorb some of this energy, not only for the driver, but also for the engine.
However, I am not the expert on this, much of this was tested and simulated by some of the engineers at Dover Group / Perfect Bore / Capricorn, modeling the different engine blocks (100mm and 104mm) and cranks (2.5 and 3.0) with various piston, crank, con rod and flywheel options. The software they used for much of it was the Riccardo suite (which I wish I could afford!) being used by several people with degrees in those particular fields, I have just benefitted what was learned from those meetings in the early days which led to the development of our 3.2 944 Turbo engines, for which we tested many configurations of bore and strokes and combinations of internals looking for a perfect mix. The real shame is that everyone who had one realised that there was enough power as they were, because the next phase was going to be development of an intake manifold to match the engines, which never happened as no one wanted it.. Quite mad really.
The 2.5 NA outputs quoted are all flywheel figures (not corrected by on a chassis dyno, but engine dyno) but they were a bit of a disappointment, as the golden goose we were looking for was 100 bhp per litre. But we did not have to go crazy looking for it and I am sure it would have been possible to hit the 100/litre mark with time, money and development.
It would be easier to get more power by increasing the rpm abilities of the engine, however the oil pump cavitates not far above 7500 rpm and the higher you go, the worse the collisions of harmonics would become.. Dry sump would have cured the oil cavitation issues, but the harmonics again become an issue.. Although pistons on a serious F1 diet, along with Ti rods, closed deck block and a lightweight all steel crank could have been made to work together, which in themselves would have released power... But that is the money and development side which was not ever going to be economic or translate into something customers would want. Which is sad but true.



Ok so the natural effect of all four cylinder engines (Over 1800cc) imbalance secondary vibrations can be masked to stop them reaching occupants but this doesn't mean they are bad just uncomfortable on a car designed for the road and long journeys.

The reciprocating mass (Pistons & Rods) are pulling up on the crank which behaves like a
spring. The heavier the mass and the faster the engine speed the more it vibrates. The 2 Balance shafts which spin in opposite directions and at twice the crank speed merely mask this vibration from the chassis.

Back to the 200bhp 2.5 8v N/A how did you achieve this?


R
 
I should probably say, it is a secret, and if it was some of the things I am working on for Boxsters, I probably still would, but as the market is non existant for 200bhp 944 8v 2.5 na's I am happy to share.

Its mostly in the cylinder head.

The 944 Na 2.5 cylinder head has a dreadful set of ports, the shape is wrong for good flow and port velocity, it promotes tumble rather than swirl in the combustion chamber as well as the port itself, and has all kinds of issues.

The ports also do not follow any kind of conventional wisdom on cylinder head design, so I could only assume that Porsche designed them that way on purpose to limit power and limit tuning potential. Exactly the same issue is really evident on 924 cylinder head intake port which are another car that is natoriously tricky to extract power from.

Like the 924 head, completely changing the ports to conform with good design releases not only peak power but torque as well. However the modification requires the addition of material as well as taking some away.

Key items are to make attempts to equalise the lengths of the long side and short side turns on the port to reduce the port suffering from the difference in port lengths causing tumbling turbulence away from the port ceiling and floor on the turn, but also this robs port velocity.

The ports also need a choke point towards the end of the turn, just before the valve seat but not breaking the 12 degree rule. This choke point from experimentation with my port profile was 85% in this application.

Lastly of course, do not polish the ports, a matt and very slightly rough port wall is needed to keep fuel atomisation at a maximum while also creating a small boundary layer which is much more slippery than a polished port anyway.

A decent cam profile is also needed, not from a re-grind as the standard profile is so far off a massive amount of material would be needed to make a decent profile in duration and overlap.

More than anything, these were the most important steps.

These items work well in a NA head, and could be used on a turbo head, but the turbo dynamics need a slightly different approach and reap less rewards than conventional turbo tuning.

The same tricks can be used on both the inlet and exhaust ports and fundamentally should be the core of any good cylinder head design or modification. The only thing which is trial and error for any head that is new to the modifier is the choke point which works best for that head and the application it is being used in.

Oval ports work well to reduce the difference in long side and short side turn, but ideally you want to use an oval tube for manifolds as well to get the best from them.

My advice would be to build a flow bench if you do not have access to one, and experiment and read as much as you can not only on cylinder head modification theory, but also other sciences such as the gas laws, fluid dynamics and even thermodynamics.

If it were a 9000 rpm screamer, my advice with port suface finish would be completely different, but for a 7000 to 7500 rpm lumbering engine like the 2.5 NA, you want to chase torque and the bhp will come along for the ride also.
 
Indi9xx said:
I should probably say, it is a secret, but as the market is non existant for 200bhp 944 8v 2.5 na's I am happy to share.

- Its mostly in the cylinder head.

- A decent cam profile is also needed, not from a re-grind.

- My advice would be to build a flow bench if you do not have access to one, and experiment and read as much as you can not only on cylinder head modification theory, but also other sciences such as the gas laws, fluid dynamics and even thermodynamics.

- If it were a 9000 rpm screamer, my advice with port suface finish would be completely different, but for a 7000 to 7500 rpm lumbering engine like the 2.5 NA, you want to chase torque and the bhp will come along for the ride also.



Thanks Jon,

I don't think the market is booming but there are a reasonable amount of N/A 2.5 944 owners that would like 200bhp+
I've edited the key tuning points from your answer above, and it makes a refreshing change not to see the usual things often mentioned by quite a
few individuals on forums and also magazine features, only they seem to be blinkered.

EG; A lot of banter is exchanged that the AFM is a joke, very restrictive and needs ditching etc....
Also a large bore exhaust is best, and many other things like more fuel, a better ECU, Bigger Injectors, and wasted spark ignition etc...

I was considering fitting a lot of components sold in the UK by 944 tuning companies but I was lucky to not be "pulled in" by a lot of this hype as
I was not convinced and instead I was recommended to a UK Engine tuner / builder / Race Team & Driver who advised me to use all the stock components:
Fuel pump & Injectors, Bosch 30 year old ECU & AFM, and Dizzy etc..

Lindsey Racing (USA) supplied me with a good bore condition 3.0 block, and 2.5T crank which they Knife edged.
They have a specialist "Flow Guy" with 40 years experience and knowledge who flow benched and ported a 2.5 Cylinder head I sent them to stage II
(Which they calculate improves the flow by 28.8%) from a stock 180 to 232 CFM.

This 2.5 Head was also modified to suit the 3.0 block.

They then sourced and calculated for me a set of New Wossner Forged pistons, CR 10:9:1 and 2nd hand 968 Rods balanced and Modified to fit.

I've never seen / heard or read (so far) of a 2.5 litre 8 valve engine producing 200bhp ? I have seen many people talking about it, and hoping that
with many products and tuning it can be achieved but it certainly doesn't seem easy, and I suspect a lot of this is because the majority of engines in
car's out there are now so old they have lost power from the original manufacturers figures and I wonder if the Porsche figures are probably too ambitious anyway ?

Have you ever seen 163 from a stock 2.5 8v ? or even 210bhp from a 3.0S2 ? only the recorded dyno days and articles I've read on these cars they are
quite a chunk less than the spec sheet suggests, due to age I guess?

As per your other criteria for good tuning progress I also went for a different Camshaft from Web Camshafts (California) which was a mild
duration.

I also had an eye on airflow in the Inlet Manifold and decided to have a punt at a Extrude Honed Service. which if you've heard of it? is an Abrasive
Putty forced under high pressure through the manifold which cleans up the rough casting flash surfaces and improves the CFM by 15%.

Lastly I have a SMALLER bore Exhaust than the original 2.5 stock item ! (By accident)

I had a lightweight 1.2mm wall Stainless exhaust system made for me in Finland by a company called (Martelius) which I was asked if
I wanted a 2" or 2.5" system. I went 2" but when it all arrived it was 2" Outside diameter not ID! so the actual ID is 48.4mm

It's a one box system with (1) rear silencer (To save weight) and a 952 Tubular Exhaust manifold (Lighter than the cast 2.5 N/A)
which only weighed 12.5kg in total! compared to the stock system @ 28.5kg.

I believe the relative small bore, no restrictions (Straight through rear box) and Plasma coated Zircotec Manifold all have some significance for
allowing the hot exhaust gases to exit with quicker velocity than a bigger bore restrictive stock system?

I was intent on having a 2.5 Engine, but it turned out I went for a 2.7 after an issue with a 2.5 worn block
So although my engine is 228cc more capacity than a 2.5 it did make over 200bhp and most impressively all with stock 2.5 8v
fueling / Injectors / Bosch Igniton Coil & Dizzy / and the 30 year old electronic ECU & AFM components.

However also Live Mapped by Wayne Schofield (Chip Wizards) who is rather good at what he does.

See the Dyno spec sheet (LINK below) for details where you can see this is NO Screamer engine whatsoever, it is very torquey from low RPM
and has higher BHP & Torque figures than the first (1985) 2.0 Turbocharged Sierra Cosworth.

So I think somehow I did chase Torque and as you mentioned 205 Ft lbs was then followed by 205 bhp!

(SPEC Sheet)
http://924srr27l.co.uk/wp...ch-Spec-924srr27L-.pdf

R
www.924srr27l.co.uk

 
S2s are pretty much always if in good condition bang on the quoted factory figures it seems, the key in that being good condition as at this age they would have to had the top end worked on by now. The only thing that can be changed according to Wayne is to swing where the torque or power peak occurs i.e. without significantly modifying the motor itself, the bolt ons make naff all difference it seems to that motor. This explains why mine feels gutless in the midrange but made 221 Bhp at 6300 rpm (peak torque of 204 Lb/ft up nearer to 5k than the 4k it should be around).

968 is a different kettle of fish again, some have made pretty impressive power by chasing it up high where that engine will just rev and rev.

 
Neil Haughey said:
S2s are pretty much always if in good condition bang on the quoted factory figures it seems, the key in that being good condition as at this age they would have to had the top end worked on by now. The only thing that can be changed according to Wayne is to swing where the torque or power peak occurs i.e. without significantly modifying the motor itself, the bolt ons make naff all difference it seems to that motor. This explains why mine feels gutless in the midrange but made 221 Bhp at 6300 rpm (peak torque of 204 Lb/ft up nearer to 5k than the 4k it should be around).
968 is a different kettle of fish again, some have made pretty impressive power by chasing it up high where that engine will just rev and rev.



That sounds like you have a good one Neil, and is the motor all stock with just the live remap to change the bhp / torque balance?

I thought it was bizarre but welcome when Wayne pushed the torque figure to exactly the same number as the bhp.
I also have 190ft lbs at 2850rpm which is great on the road, also more so due to the huge vehicle weight loss I can drive in 3rd gear at 25mph and it'll pull
nice and easy without grumbling ! If only I could afford a modern sequential auto box that would be amazing...

R
www.924srr27l.co.uk

 
924Srr27l said:
Have you ever seen 163 from a stock 2.5 8v ? or even 210bhp from a 3.0S2 ? only the recorded dyno days and articles I've read on these cars they are
quite a chunk less than the spec sheet suggests, due to age I guess?


From Rick Cannell's website http://www.cannell.co.uk/
TOP 10 Normally Aspirated BY FLYWHEEL HP
[edited because the table doesn't display here..so just the HP numbers]
222.7
219.3
218.8
215.5
212.6
211.7
209.7
208
206.2
202.4

Most of the cars on the dyno days were turbos, but the few S2's seemed to do OK. This was on the Weltmeister "rollers of truth", which didn't produce flattering figures... FWIW I understand that stock 968's often don't deliver close to their claimed 240 (interesting to see Neil's comments though). I'd quite like to see how my new engine fares on a dyno as it feels a lot stronger than the slightly tired (225k mile) one it replaced. I would also quite like a Michael Mount built 3.0 N/A 400hp motor though [:)]
 
edh said:
924Srr27l said:
Have you ever seen 163 from a stock 2.5 8v ? or even 210bhp from a 3.0S2 ? only the recorded dyno days and articles I've read on these cars they are
quite a chunk less than the spec sheet suggests, due to age I guess?


From Rick Cannell's website http://www.cannell.co.uk/
TOP 10 Normally Aspirated BY FLYWHEEL HP
[edited because the table doesn't display here..so just the HP numbers]
222.7
219.3
218.8
215.5
212.6
211.7
209.7
208
206.2
202.4

Most of the cars on the dyno days were turbos, but the few S2's seemed to do OK. This was on the Weltmeister "rollers of truth", which didn't produce flattering figures... FWIW I understand that stock 968's often don't deliver close to their claimed 240 (interesting to see Neil's comments though). I'd quite like to see how my new engine fares on a dyno as it feels a lot stronger than the slightly tired (225k mile) one it replaced. I would also quite like a Michael Mount built 3.0 N/A 400hp motor though [:)]


aww.. the 'good old days' Ed...fond memories sir.....when 'men were men'.....haha..

Pete
 
I just reread my spec from back then...I think things have changed just a little ...for one the A/C is fully working now....:)
 

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