968 head on S2
- Thread starter colin944
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JamesO
New member
I ran an S2 head on a 968 block for a while. The main differences are the Variocam, bigger valves and ports, an oil temp sensor (not present on the S2) and the valve cover.
I blanked off the variocam hole in the valve cover with a thin bit of ally. I used the 968 inlet manifold and it matched the S2 ports/bolt pattern. Exhaust ports also match either head.
So in summary it should work the other way then maybe a remap?
Not sure the 968 loom/ECU would ba a great Idea unless you have the injectors and the MAF too.
I blanked off the variocam hole in the valve cover with a thin bit of ally. I used the 968 inlet manifold and it matched the S2 ports/bolt pattern. Exhaust ports also match either head.
So in summary it should work the other way then maybe a remap?
Not sure the 968 loom/ECU would ba a great Idea unless you have the injectors and the MAF too.
Neil Haughey
New member
The exhaust manifolds are identical (same part number) and as James says everything else can match up. I believe you can even put an S2 cover on the 968 head such that it will look basically like a normal S2 engine.
Not a lot of point in doing it though unless one is looking to open up the top end where the big inlet valves will help, the Promax chip would probably be sufficient as ISTR you can rev up to 7K rpm whereas a standard S2 engine runs out of puff in the mid 6s.
Not a lot of point in doing it though unless one is looking to open up the top end where the big inlet valves will help, the Promax chip would probably be sufficient as ISTR you can rev up to 7K rpm whereas a standard S2 engine runs out of puff in the mid 6s.
Chrishazle
Active member
Promax 968 Uk chip rev limiter is 7100RPM, standard 968 chip is about 6800. Believe there is a USA Promax chip (or maybe it's more track oriented) that is 7700RPM.
Neil Haughey
New member
I believe the stock S2 limiter is around 6700 to 6800 as I have hit it a few times on track, I have 2 different ECUs to play with as well. ISTR stock 968 limiter is 6900 but many would raise this as the car is still producing plenty of power up at 7k rpm.
I was toying with the idea as I would like a bit extra poke. I was thinking 968 head with throttle bodies and a mega squirt ecu. I have seen vauxhall 2lt 16v engines producing 280 ish bhp with throttle bodies and mega squirt. So I thought if you had vario cam 3ltrs and throttle bodies maybe I would get a nice reliable 3oo ish bhp without any of the turbo lag etc of a turbo conversion.Also advantage of na with throttle boddies is instant go, this makes the car feel alot faster and extremely responsive .Things that the Turbo boys can only dream of.
944 man
Active member
Theyre throttled though. The heads are lovely, but the cams are very steady and the whole inlet tract is restrictive. I realise that by going MAP youll be removing a good deal of this, but I suspect that you end up able to flow a lot more air than the engine will take, seeing extremely modest gains. 
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(Neil Haughey
New member
9meister tried it a few years back with little success. They claimed that the angle of the engine in the engine bay creates a very tight turn into the head which subsequently creates pretty poor flow if trying to go for big power. Motor bike tuners face the same problem and have tended to get greater port velocity by adding material back into the head on the underside to create faster flow. ISTR Colin Belton talked about this on PH several years back as they had thought of doing that but by then had given up. Custom cams would definitely be a good thing as when I looked at this a few years back the cams seemed pretty mild, unfortunately no one in Europe seems to sell modified cams for the 968. There was a German tuner I spotted several years back that did but no amount of searching last year could turn up those old pages.
Ultimately the problem with tuning the 968 engine is its much more profitable in terms of gains to go for turbocharging, either by straight replacement with a turbo lump or a 968RS turbo a like solution.
There was another thread btw over on PH a couple of years back about supercharging and tuning the 968. At the time I did a quicky calculation of bmep for the 968 and other comparable high performance engines. It actually is a pretty powerful engine just doesn't rev high enough to create big BHP numbers compared to modern high performance NA engines. With this in mind and the same gear ratios one has to consider if throttle bodies etc. will really create the extra desired performance. As an example imagine if the engine gets another 50 BHP by hanging on to each gear for another 1500 rpm but produces the same torque (which is highly likely as from memory they don't tend to result in any more torque). It might work out that on track this doesn't actually translate to that much of a gain in performance. Getting 350+ lb/ft though from a turbo motor will make the car fly anywhere and at any time.
Not ready to give into the boost yet Stu. !!!! I will however probs end up building a turbo 3lt 16v though. (sighs out loud) I need to go away and do loads of studdying on this. No where can I get some one to make me a pair of cams ...............
I will crack the big power n/a thing if not then boost here we come.Oh and really need to phone Al.
I will crack the big power n/a thing if not then boost here we come.Oh and really need to phone Al.
bmnelsc
New member
I found this on "How stuff works" page on 924s but I don't think engine position changed much for 944s..."Installation was at a 40-degree tilt to starboard, making this a "slant four," technically speaking."
So the angle of the head should be no worse than a V8 or 90deg V6 as far as intake plumbing and resultant air flow is concerned although I think Porsche probably engineered the intake for near optimal flow while keeping good torque production. In fact - the whole vario cam set up on the 968 is to improve drive-ability by increasing low RPM torque while maintaining good high rpm HP.
I agree about the difficulty in producing substantial horsepower gains without forced induction (turbo or supercharging). It seems that Porsche engineered these pretty well for power production plus reliability so any improvements require significant work (head flow and cam work as well as whole new intake and exhaust setup to match the heads). When you do get a big increase, you might have a good track machine but it might not be very good for street use (too much valve overlap to idle below 2000rpm, torque curve starting at 3500, etc).
Neil Haughey
New member
True. If one looks at bmep figures then many engines with on paper much more power have either less or similar bmep. ISTR the engine in the Honda S2000 as an example has a lower bmep then the 968 motor, despite having on paper a very high specific output (Bhp / capacity). In other words it makes the power with lots of revs.
I also recall an article many years ago in Cars and Car Conversions. They tested various throttle bodies and custom inlet manifold setups on the legendary Vauxhall XE engine (tuners and kit car favourite). The system with the best low to mid range torque was the stock manifold. I knew a guy years ago who had one of those engines kicking out 280 Bhp, pretty mental for a 2 litre engine.
Loads of revs on a 968 engine for track work could work great as long as the final drive ratio or gear ratios are altered to suit i.e. say the max power is now at 20% higher rpm make the gears 20% shorter.
I also recall an article many years ago in Cars and Car Conversions. They tested various throttle bodies and custom inlet manifold setups on the legendary Vauxhall XE engine (tuners and kit car favourite). The system with the best low to mid range torque was the stock manifold. I knew a guy years ago who had one of those engines kicking out 280 Bhp, pretty mental for a 2 litre engine.
Loads of revs on a 968 engine for track work could work great as long as the final drive ratio or gear ratios are altered to suit i.e. say the max power is now at 20% higher rpm make the gears 20% shorter.
Chaps,
I'm reading this thread with interest, although the technical discussions are just at the border of my understanding. I need to google BMEP to better understand the significance of it (I what it stands for, but not much more than that.)
Yes, but this won't overcome the fact that you still have a peaky engine with power in a small part of the rev range. It brings the (road) speeds at which this power is produced down, but still means that you need to assiduously keep it in the upper rev range to make the most of the extra power (making it a very tiring engine to drive.)
Oli.
I'm reading this thread with interest, although the technical discussions are just at the border of my understanding. I need to google BMEP to better understand the significance of it (I what it stands for, but not much more than that.)
Yes, but this won't overcome the fact that you still have a peaky engine with power in a small part of the rev range. It brings the (road) speeds at which this power is produced down, but still means that you need to assiduously keep it in the upper rev range to make the most of the extra power (making it a very tiring engine to drive.)
Oli.
Oli:
Start here - http://www.epi-eng.com/piston_engine_technology/bmep_performance_yardstick.htm
It looks offputting at first but read through the text first without stopping to consider the equations.
Colin:
Barring forced induction or nitrous oxide, you have two ways to go.
This is what I would do if I wanted the best possible normally aspirated 944S2 for road use.
A really fit and healthy 968 engine (nominally 240ps, 236 bhp) installed in a 944 makes the 944 quicker than a 968 due to the car's lower weight. There is virtually nothing to be had be attempting to tune the engine, though a decat and custom remap will get you a few bhp, possibly getting you up to 250bhp, and all without huge development cost because apart from the decat pipe and remap you are using all stock components. Consulting EMC Motorsport in Birmingham, who know a tremendous amount about the 968 engine, would be a good plan.
Having brought the engine up to full potential that leaves you weight reduction. To get your now 250 bhp S2 to feel like 270 bhp you would have to take 100 kg out of it. This is easy for a track car (no sound deadening, composite hatch, composite wings and bonnet etc) but not so easy for something that you want to be a quiet civilised road car. Replacing the front seats with lightweight fixed buckets and ditching the rear seat, spare wheel etc, and fitting the lightest available wheels and tyres (probably the forged CS wheels off a Turbo S) can save you a total of about 50 kg. But having done that you would have a normally aspirated S2 that would absolutely fly, with a power to weight ratio equivalent to about 260 bhp in your car as it is now, quicker than a 968CS and benefiting from the braking and handling improvements that would also come for free with the weight reduction.
I think this would be a really superb car, one I would love to own.
The second way is to put in a small-block Chevy.
Start here - http://www.epi-eng.com/piston_engine_technology/bmep_performance_yardstick.htm
It looks offputting at first but read through the text first without stopping to consider the equations.
Colin:
Barring forced induction or nitrous oxide, you have two ways to go.
This is what I would do if I wanted the best possible normally aspirated 944S2 for road use.
A really fit and healthy 968 engine (nominally 240ps, 236 bhp) installed in a 944 makes the 944 quicker than a 968 due to the car's lower weight. There is virtually nothing to be had be attempting to tune the engine, though a decat and custom remap will get you a few bhp, possibly getting you up to 250bhp, and all without huge development cost because apart from the decat pipe and remap you are using all stock components. Consulting EMC Motorsport in Birmingham, who know a tremendous amount about the 968 engine, would be a good plan.
Having brought the engine up to full potential that leaves you weight reduction. To get your now 250 bhp S2 to feel like 270 bhp you would have to take 100 kg out of it. This is easy for a track car (no sound deadening, composite hatch, composite wings and bonnet etc) but not so easy for something that you want to be a quiet civilised road car. Replacing the front seats with lightweight fixed buckets and ditching the rear seat, spare wheel etc, and fitting the lightest available wheels and tyres (probably the forged CS wheels off a Turbo S) can save you a total of about 50 kg. But having done that you would have a normally aspirated S2 that would absolutely fly, with a power to weight ratio equivalent to about 260 bhp in your car as it is now, quicker than a 968CS and benefiting from the braking and handling improvements that would also come for free with the weight reduction.
I think this would be a really superb car, one I would love to own.
The second way is to put in a small-block Chevy.
Simon,
Thanks for that link. I'll read it with interest.
I was under the impression that 968 engines rarely made their stated BHP, for a number of reasons. Whereas S2 engines usually just about managed to show their full 211bhp. Does the 968 engine have a much more useful torque curve? I am guessing that variable valve timing will potentially allow this, but how effective is it? (Or, putting it another way, is it effective enough to justify the cost and hassle of having the engines swapped?)
The notion of 250ish BHP in a sensibly light S2 is one to get me quite excited. Hmmmm ...
Oli.
Thanks for that link. I'll read it with interest.
I was under the impression that 968 engines rarely made their stated BHP, for a number of reasons. Whereas S2 engines usually just about managed to show their full 211bhp. Does the 968 engine have a much more useful torque curve? I am guessing that variable valve timing will potentially allow this, but how effective is it? (Or, putting it another way, is it effective enough to justify the cost and hassle of having the engines swapped?)
The notion of 250ish BHP in a sensibly light S2 is one to get me quite excited. Hmmmm ...
Oli.
I gather that unless well maintained by those who really understand them, the engines are frequently not often on top form due to cam chain stretch, and that they are very sensitive to the condition and setup of the whole Variocam apparatus, as well as timing. I think a well set up one can do its numbers, though.
This pdf is quite illuminating: it goes into the wear problems and how to inspect them.
http://www.cannell.co.uk/968_Workshop_Manuals/Procedure%20for%20inspection%20of%20Porsche%20968%20Camshafts.pdf
Whether the Variocam setup is worthwhile really depends on the value you put on getting more than S2 grunt out of the 3.0 16v engine. It does add about eight per cent to the maximum torque (225 lb ft at 4100 rpm vs 207 lb ft at 4000 rpm) as well as boosting the top end. Personally I'd love to have that engine in a 944 as I outlined above for high days and holidays, but it is probably always going to be a fairly highly strung engine simply because of what it required of it without forced induction.
The 968 engine, when delivering its numbers, delivers BMEP of 185 psi, which for a normally aspirated 4 stroke is pretty impressive, and is the main reason why there is not a lot left to be had beyond the book numbers by tweaking it.
Obviously for everyday mooching around a simple, easily maintained, 300 bhp, 350 lb ft Turbo remains an affordable and practical option for pushing around the weight of a fully trimmed car, even if it does have slightly fuzzier throttle response.
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