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Nice 944T from Sweden

I agree with the ignition concept. You get far more bang for your buck if you advance ignition - the higher the pressure at combustion the more energy you'll get out of the expansion process. By simply increasing boost you have to retard ignition, but if you can maintain boost and advance ignition you'll get far better results. That's why diesel engines produce more torque out of a far inferior fuel - the compression of the fuel air mixture is greater - it is this extra compression that is the secret to producing the extra torque. Modern direct injection engines allowing compression ratios to increase and ignition timings to advance are catching up with diesels and if they can be developed further to give you the same combustion pressures then you'll have a far more efficient engine than a diesel - though combustion temperatures are likely to become the limiting factor. Heat and pressure are the two key parameters in internal combustion engines. You want to achieve as high a pressure as possible in the combustion chamber then heat it up as much as possible to get the most powerful expansion forces.

Until someone actually invests time and effort in developing a new cylinder head for 944T's with variable valve timing and lift and direct injection then we'll never get to explore the limits. So are there any clever people out there with a milling machine?
 
ORIGINAL: barks944
I guess his head/cams work pretty well, does he have higher CR than your engine? He seems to think ignition is a big factor, certainly seems to prefer less boost and more ignition. Is this something you have played with? I guess his monster IC will help keep the intake temps down and berylium valve seats are supposed to conduct heat from the exhaust valves well. This combination might be helping him to run a lot of ignition advance without getting knock.

He indeed has a CR of 9:1 instead of 8:1.
Yes the large IC must help, but coupled to the large GT35 turbo he is running I suppose he has to deal with a fair bit of lag.
 
ORIGINAL: 333pg333

nobody can remark on this car??

Sorry Pat, it was a Bank Holiday weekend over here so I was away at the coast and missed your post [;)]

I've followed Corleones posts on RL for a few years and he's certainly built a remarkable and enviable car. I agree that the tax laws in Sweden make it very worthwhile to improve an older car as opposed to bying a new one, which is why you see so many impressive 944's coming from such a small baseline of 944 population.

The UK is very different in outlook and also in cross section of enthusiasts. Most of us are more than happy to leave these cars as almost they were when they left the factory but continue to drive them every day in all weathers as the truly practical sportscar they always have been. Because of this we have to spend far more just on maintaining them mechanically and also addressing the dreaded rust that arises in our damp climate.

However, there are always one or two of us mad enough to want more [;)]
 

ORIGINAL: TTM

ORIGINAL: barks944
I guess his head/cams work pretty well, does he have higher CR than your engine? He seems to think ignition is a big factor, certainly seems to prefer less boost and more ignition. Is this something you have played with? I guess his monster IC will help keep the intake temps down and berylium valve seats are supposed to conduct heat from the exhaust valves well. This combination might be helping him to run a lot of ignition advance without getting knock.

He indeed has a CR of 9:1 instead of 8:1.
Yes the large IC must help, but coupled to the large GT35 turbo he is running I suppose he has to deal with a fair bit of lag.
Says the man who states that he sees 17psi at 2700rpm!! [:)]
Seriously Thom I would have said that Corleone's car won't have much lag with the higher c/r and 3L capacity. The GT series turbos spoolup very nicely. He is also using an incredible 36 degrees adv. ign at some point in the curve!!
 

ORIGINAL: Diver944

ORIGINAL: 333pg333

nobody can remark on this car??

Sorry Pat, it was a Bank Holiday weekend over here so I was away at the coast and missed your post [;)]

I've followed Corleones posts on RL for a few years and he's certainly built a remarkable and enviable car. I agree that the tax laws in Sweden make it very worthwhile to improve an older car as opposed to bying a new one, which is why you see so many impressive 944's coming from such a small baseline of 944 population.

The UK is very different in outlook and also in cross section of enthusiasts. Most of us are more than happy to leave these cars as almost they were when they left the factory but continue to drive them every day in all weathers as the truly practical sportscar they always have been. Because of this we have to spend far more just on maintaining them mechanically and also addressing the dreaded rust that arises in our damp climate.

However, there are always one or two of us mad enough to want more [;)]
Oh don't worry too much about me Paul. Sometimes I just shoot from the hip a little. I get the idea of keeping things stock from a reliability factor. Having experienced a lot of down time gets very boring. Now I see it as a good thing in one regard. Gives me a greater chance of keeping my licence. [&:]

When are we going to see more of Lil anyway?? Been a while since you've posted any videos hasn't it??
 

ORIGINAL: 333pg333

Been a while since you've posted any videos hasn't it??

True. No money = no trackdays = no videos [:(]

Things are looking up this year though, the business has picked up fantastically so hopefully I'll get some tracktime in. However I am seriously thinking of going down MarkK's route and getting a full on racecar instead of just dabbling around with a heavy road car on trackdays. Of course this will mean even more of a wallet battering, so I 'd better knuckle down and get back to work [;)]
 
Great news Paul. I totally agree too. The road car on the track is always about compromise. My latest iteration is getting pretty close to crossing the line. Cage is next but that's waiting on $$. Ahh to win that elusive Lottery...
 
I'm afraid I'm going to have to be very controversial on this and go completely against the grain of other peoples replies. I think the design of the internal engine is superb. With the pistons mirroring the design of the head perfectly and excellent work on eliminating hot spots in the coolant. Also striving for good flow and low boost has to be the way to go but after that I disagree with a lot he has done.

The engine is clearly performing very well but you have to ask how much better his car could be with a few changes. His intake manifold is WAY too short on the runners and must be killing the mid range power of the engine.. all to get relatively small gains at the top end where the 8v head and natural inertia of the big 4pot engine are weakest. He's fighting the engines design with tuning more suited to a small capacity ricer rather than working with it and reaping the benefits of low end torque.

The intercooler flow is designed so the air has to travel the maximum distance possible through the cores first down through it one way then back up the next. It's like asking you to maintain pressure on the other end of a 1.5m long straw. I'm sure the cooling efficiency is top notch but its a balancing act and I cannot think how you could have designed an intercooler for more lag or to make the turbo work harder.

I wonder why he's having so many cooling problems?? With no ducting most of the air hitting the front of the car will avoid a massive blockage like that 1/2 mile thick intercooler pushing it around the sides and away from the radiator. An intercooler half the size with cores running the other way so 1/4 of the length would be a breeze for that turbo to pressurize and with proper sealed ducting from the vents at the front to force air through it would probably be 70-80% (random figure) as good at cooling but would allow the turbo to do a tiny percentage of the work so you'd be starting with much cooler air anyway.

That way you'd probably have a lot less trouble cooling the damn thing and the car would be a lot faster accelerating even if the peak hp figure dropped 20-30hp. Which might not even happen if the effort on the turbo due to the intercooler is counteracting the benefit of his short runners at the high end. Which it might be.
 
This run is 5.88 second, from 3200-7100 rpm
Power is 150 hp at 3200 rpm and 449 (330 kw) at 7000 rpm. No hp loss up to 7600 rpm (another run).
Torque is between 493 nm (at 3200) and 526, average is 505 nm (all this torque with 12% calculated drivetrainloss).

Mid range seems pretty epic, spools up at 3200 rpm and produces about 500nm of torque from there to the redline.
 
ORIGINAL: barks944

This run is 5.88 second, from 3200-7100 rpm
Power is 150 hp at 3200 rpm and 449 (330 kw) at 7000 rpm. No hp loss up to 7600 rpm (another run).
Torque is between 493 nm (at 3200) and 526, average is 505 nm (all this torque with 12% calculated drivetrainloss).

Mid range seems pretty epic, spools up at 3200 rpm and produces about 500nm of torque from there to the redline.

Your right. I forgot to add the other thing, 4-1 manifolds are not supposed to be a good thing either but in the end none of the theory matters. Results matter and he certainly has them! I just read through the whole thread properly and he's a really nice guy. I love that he challenges what is accepted. His timing, his compression ratio.. maybe because the 944 is so low end biased in its delivery you need to be as extreme as him to raise the top end in line?

My calculations say that his car can't work. The head simply can't flow enough air to hold 1 bar boost at 7000rpm you'd need 630cfm.. but it does so it must.

Nothing like real world testing I suppose.... I still maintain he could do better than that intercooler though.
 
Well its not out of the realms of possibility that he is being a little generous with his figures. He certainly seems to have have produced an engine with a very special torque curve. The car must be immensely quick.
 
As with most things in life - there are no absolute rules. It is the net effect of all the parts working together. Others and I have said it before - it is all about matching all the mods relative to eachother and not just picking and choosing various random off-the-shelf mods based upon the individual performance improvement claims. I think that often the benefit of manifold designs is much overhyped - yes you can gain small improvements in absolute headline power and torque values but really manifold design is more about achieving the shape of the power and torque curves and achieving the intended behaviour. The stock Porsche manifolds have been proved to be a pretty optimised design from various back to back rolling road comparisons i've read of - but of course if you're going to 3ltr capacity and modifying the head significantly then the stock manifold will no longer be any good for this application.

Seems to me this car is the result of alot of investment in thought about the mods used and very good tuning, the results speak for themselves! It'll be an awsome car to drive - assuming the power can be laid down on the road without wasting too much of that performance.
 
Interestingly, Corleone here still uses a (vastly modified!) 2.5 head which intake ports don't seem as large as the 2.7's and are still round. Though I can't find a mention about it I feel he has had the whole intake line flown on a bench.

This got me passively thinking about intake manifolds and I can't figure out some important points.

The original intake manifold "works" with a 2.7 head if its round ports are ovally widened to fit, but to me such a modification somewhat feels like a band-aid - as far as I understand Fluid Mechanics the velocity of air will decrease in the runners of the intake manifold as the section gradually turns from round to oval (the oval section being larger than the round one), well at least if the pre intake valve air pressure remains constant.

In that case if the runners (well, let's include the whole intake manifold) were widened to fit the oval ports then the next restriction in the intake line is the throttle body. If you then increase the diameter of the TB, then the IC pipes are the next restriction?

I'm sure it's a whole lot more complicated than this, and I don't understand it well - surely the air pressure varies at various points in the intake line, especially before/after the TB.
Thoughts? [8|]
 
ORIGINAL: TTM

Interestingly, Corleone here still uses a (vastly modified!) 2.5 head which intake ports don't seem as large as the 2.7's and are still round. Though I can't find a mention about it I feel he has had the whole intake line flown on a bench.

This got me passively thinking about intake manifolds and I can't figure out some important points.

The original intake manifold "works" with a 2.7 head if its round ports are ovally widened to fit, but to me such a modification somewhat feels like a band-aid - as far as I understand Fluid Mechanics the velocity of air will decrease in the runners of the intake manifold as the section gradually turns from round to oval (the oval section being larger than the round one), well at least if the pre intake valve air pressure remains constant.

In that case if the runners (well, let's include the whole intake manifold) were widened to fit the oval ports then the next restriction in the intake line is the throttle body. If you then increase the diameter of the TB, then the IC pipes are the next restriction?

I'm sure it's a whole lot more complicated than this, and I don't understand it well - surely the air pressure varies at various points in the intake line, especially before/after the TB.
Thoughts? [8|]

Well I can only tell you what I understand about intake manifolds so far and that there can be 4psi or more of difference in pressure taken at various locations inside the intake run (turbo to intake manifold). A guide for throttle plate size in the throttle body is 62mm up to 390hp, 70mm up to 500hp and 75mm up to 600hp. Hard pipe size should roughly follow this and hard pipes must be 'hard pipes' where ever possible. Rubber sections are never good and bends in the pipes are to be avoided (never make a 90* bend if it can be avoided).

The diameter of the runners should be between 0.76-0.8 X the size of the intake valve to give the best flow characteristics into the cylinder. The longer the length the neater the airflow so the better low end power but the shorter the length the less resistance to speed of airflow so the better high end power. The end of the inlet runners where it meets the plenum chamber should always be bellmouthed (or domed as he has done - same thing) the plenum should narrow toward the furthest cylinder and diameter should never be less than 1.5 x diameter of the runner at the thin end.

The intercooler is almost always the biggest restriction in the inlet and so having many short cores rather than a few long cores to do the cooling is best. Also the back of the intercooler is typically 1/3 as effective as the front for cooling so an intercooler shouldn't be more than 50-60mm thick.

Below is the perfect design which gives even pressure to all areas of the intercooler and allows maximum flow and cooling for its size but due to restrictions in the 944 an intercooler with top entry inlet and outlet plus a similar thining end tank design similar to the plenum chamber would probably be better (avoid nasty pipework).

There's loads more to all this that I dont know (perhaps others can expand?) but this is a good start.


D5F4F06385D4497E82B4E761E34A0ED1.jpg
 
Here's my current understanding about manifolds and intakes. Firstly I think its important to note the differences between a N/A and turbocharged design.

A N/A engine uses the gas velocity in the intake and manifold to generate port pressure. The flow of the gas generated during the intake stroke pushes on the intake valve when it closes and this will generate a pressure at the valve which will increase cylinder fill and produce more power the next time it opens. Consider it like a load of people running down a corridor through a door at the end. If they are all at full pace and that door shuts they all cram up against the door. Eventually they will all stop and the guys at the front will be squashed up against the door. At that point they all start moving back the other way. In an engine this can be timed so that the flow doesn't have time to reverse back the other way so when the valve opens you have all that pressure built up which will fill the cylinder nicely. This will have an oscillatory frequency which can be matched to the valve timings over a certain band, if you can change valve timing and the dynamics of the intake then you can maximise the effect over a broad rev range. The kind of pressure generated in this way will relate to the speed of the gas flowing through the manifold. Considerations are cross sectional area and length of the intake. Cross sectional area effects the gas velocity and effects the restriction in the pipe for a given flow rate. Intake length increase the mass of air flowing and its inertia changing the pressure that can be generated. Longer length means a greater mass of air pushing up against the valve. However it also effects the oscillatory behaviour of the gas. Longer length would shift towards more pressure but at lower frequency of oscillation.

In a turbo application you have two scenarios, off and on boost. Off boost you want to take advantage of the pressure that can be generated by gas velocity as your turbo isn't generating pressure. However on boost the turbo is generating pressure for us and certainly over the rev band of our cars that is going to be more than can be generated by gas velocity. It can constantly provide that pressure without oscillation. What we want is a constant high pressure at the valve. Reducing the restriction in the intake will help us get a constant pressure at the valve. However we also have to consider that our intake valve is still opening and closing and this will have an effect on the pressure at the valve, inducing oscillation. Pressure will drop when the valve is open and build up again when closed, we want the pressure drop as small as possible and to return to full boost pressure as soon as possible ready for the next intake stroke. If we use a manifold design like Corleones where there is a short pipe and a large plenum we can help keep that pressure constant. The large plenum is essentially a damper and the short length of pipe leading to the valve means that pressure drop is low and it quickly equalises to the pressure in the plenum after the intake stroke. This design is excellent when on boost but it won't be great off boost.

I think Corleones engine will be great on boost but with his cam profile and intake design I think it may be a little weak off boost. Although this is relative as he's still got 3.0 litres, a decent compression ratio and good timing.
 

ORIGINAL: TTM

The original intake manifold "works" with a 2.7 head if its round ports are ovally widened to fit, but to me such a modification somewhat feels like a band-aid - as far as I understand Fluid Mechanics the velocity of air will decrease in the runners of the intake manifold as the section gradually turns from round to oval (the oval section being larger than the round one), well at least if the pre intake valve air pressure remains constant.
Thoughts? [8|]

It is cross sectional area that is important. If the shape changes as the cross sectional area remains the same then you will get no difference in velocity or pressure (apart from usual losses due to boundry layers and eddy's) assuming that the shape change is gradual and not severe. If you reduce cross sectional area the velocity will increase and the pressure will decrease and visa versa in the case of the cross sectional area increasing.

However this is all largely irrelevant to intake manifolds as you don't have constant and steady flow. You have a pulsing flow with the air inside the manifold changing direction and exhibiting pressure waves within the runners as the valves open and close. This makes things much more complicated by a significant magnitude. The location of these pressure waves along the length of the runners will vary depending upon engine RPM and load. So a single fixed manifold design is a compromise that will only really work for one specific set of parameters of RMP and load and outside of that sweet spot the manifold design will not be optimised. That is why things like VarioRam exists as it attempts to change the properties of the manifold to widen the manifolds operational 'sweet spot'. VarioRam changes the volume of the manifold plenum (the bit that opens up and feeds the runners) to try to dampen out these pulses and to keep the position of the pressure waves constant over a wider RPM band. Conventional design aims to position the pressure waves such that you have an area of high pressure at the cylinder head port to maximise the filling of the cylinder. The downside is that high pressure = higher temperature, but the design is such the benefits outweigh the downsides.

This is why flow bench figures are largely irrelevant. You can have two manifolds of different designs and the one that flows the least might actually be the better option for the given application.

It is rare that the intake manifold is the biggest restriction in an engine anyway. As DevineE says, the IC and other downstream components will present larger restrictions.

The shape of the port is chosen to influence turbulence as the air enters the cylinder through the port. In a turbocharged car then this is of lesser importance under boost at least due to the pressure the air is less inclined to be turbulent and any turbulence settles much quicker. For an N/A car oval ports are more likely to be utilised to minimise turbulence as turbulence causes the velocity of the air (in random directions though) to increase, pressure to decrease, energy taken out of the airflow, losses and ultimately less air to getting into the cylinder. However turbulence is good for fuel mixing - so as always there is a classic Engineering paradox - the two main things you are trying to achieve are diametrically opposing. This is why there is no such thing as one single 'best' design. It all depends upon what you're after, so by saying "such and such's car's manifold runners are tool short or long" is not really relevant as they may be like that on purpose to achieve a specific aim.

Complicated stuff and to simply say one engine is better than another because it develops more power or torque is shortsighted and is like viewing a potential house purchase by simply looking through the letterbox.
 

ORIGINAL: sawood12


ORIGINAL: TTM

The original intake manifold "works" with a 2.7 head if its round ports are ovally widened to fit, but to me such a modification somewhat feels like a band-aid - as far as I understand Fluid Mechanics the velocity of air will decrease in the runners of the intake manifold as the section gradually turns from round to oval (the oval section being larger than the round one), well at least if the pre intake valve air pressure remains constant.
Thoughts? [8|]

It is cross sectional area that is important. If the shape changes as the cross sectional area remains the same then you will get no difference in velocity or pressure (apart from usual losses due to boundry layers and eddy's) assuming that the shape change is gradual and not severe. If you reduce cross sectional area the velocity will increase and the pressure will decrease and visa versa in the case of the cross sectional area increasing.

However this is all largely irrelevant to intake manifolds as you don't have constant and steady flow. You have a pulsing flow with the air inside the manifold changing direction and exhibiting pressure waves within the runners as the valves open and close. This makes things much more complicated by a significant magnitude. The location of these pressure waves along the length of the runners will vary depending upon engine RPM and load. So a single fixed manifold design is a compromise that will only really work for one specific set of parameters of RMP and load and outside of that sweet spot the manifold design will not be optimised. That is why things like VarioRam exists as it attempts to change the properties of the manifold to widen the manifolds operational 'sweet spot'. VarioRam changes the volume of the manifold plenum (the bit that opens up and feeds the runners) to try to dampen out these pulses and to keep the position of the pressure waves constant over a wider RPM band. Conventional design aims to position the pressure waves such that you have an area of high pressure at the cylinder head port to maximise the filling of the cylinder. The downside is that high pressure = higher temperature, but the design is such the benefits outweigh the downsides.

This is why flow bench figures are largely irrelevant. You can have two manifolds of different designs and the one that flows the least might actually be the better option for the given application.

It is rare that the intake manifold is the biggest restriction in an engine anyway. As DevineE says, the IC and other downstream components will present larger restrictions.

The shape of the port is chosen to influence turbulence as the air enters the cylinder through the port. In a turbocharged car then this is of lesser importance under boost at least due to the pressure the air is less inclined to be turbulent and any turbulence settles much quicker. For an N/A car oval ports are more likely to be utilised to minimise turbulence as turbulence causes the velocity of the air (in random directions though) to increase, pressure to decrease, energy taken out of the airflow, losses and ultimately less air to getting into the cylinder. However turbulence is good for fuel mixing - so as always there is a classic Engineering paradox - the two main things you are trying to achieve are diametrically opposing. This is why there is no such thing as one single 'best' design. It all depends upon what you're after, so by saying "such and such's car's manifold runners are tool short or long" is not really relevant as they may be like that on purpose to achieve a specific aim.

Complicated stuff and to simply say one engine is better than another because it develops more power or torque is shortsighted and is like viewing a potential house purchase by simply looking through the letterbox.

1zvlza.jpg
[;)][:D]
 


ORIGINAL: sawood12
by saying "such and such's car's manifold runners are tool short or long" is not really relevant as they may be like that on purpose to achieve a specific aim.

Your right. He seems to have fully dedicated all parts of the design to give the best power right at the top of the rev range and in that way they do all work together.

I don't think this will create the best results for the 944 because I feel your fighting its 'big V8 style' nature but he goes one way (with good results) and I'll go another. I'm going to do everything the way I think is best (with consideration given to my budget too!) and in the end we shall see.

Since the two cars are unlikely to ever meet / compete and going out in my old 3.2 the other day reminded me just how fast 500lb/ft of torque feels.. I don't suppose it really matters what the outcome is. It's just fun to have a try


 

ORIGINAL: DivineE

He seems to have fully dedicated all parts of the design to give the best power right at the top of the rev range and in that way they do all work together.

There's no denying his impressive figures and attention to detail but you are right that it all seems top end with very little low down driveability. I can't quite understand his dyno sheet but if I'm reading it right then both MarkK's and Ricks 2.5L cars make more power low down than his 3.0L car. This strikes me as odd because every larger capacity 944T I have driven has had wonderful low down pull [&:]
 

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