Porsche Enthusiasts Club Forum

This isn't a NA carburreted Ford Escort its quite clear from what you are saying that you have no idea how a Bosch fuel injected engine management 944 engine works and performs. I would suggest you get some basic performance tuning books from the library and do a bit of reading.
You are going about this all the wrong way.
Do you seriously think that you can significantly improve upon Porsche engine design engineering by simply thinning the head gasket to increase the compression ratio ?

Peanut is right. I should point out that I went for the ultimate in tuned heads for mine. Cost quite a bit but the results are interesting. Needed to be rebuilt anyway. Head was done by these guys using the latest technology. http://www.cncheads.co.uk/ It's not just about flow but about gas speed.

So what are they offering here? A brand new head machined buy them selfs? Maybe urs jj will be the 1st in there Porsche illbery.

Peanut, you're clearly astute and obviously more knowledgeable on these issues - which is exactly why someone like me posts questions on a forum like this - because I don't pretend to know everything about tuning a normally aspirated Porsche motor. I, like a great many others, rely on forums such as this for advice from those willing to make a constructive contribution without being patronising...

As for being able to improve on Porsche's motors or get the best from our cars - A whole industry exists simply because it can get more from mass produced manufacturers offerings and reading other forums it's clear that some things can be done, especially on the head, that will do just that.

If you'd like to educate us simple folk on just how to get the most of this specific Bosch fuel injection system or if you'd perhaps like to answer the question posed, then please do so. I'm more than happy to be told just how to go about this as you seem to be so convinced that I'm doing it all wrong.

why do you assume that you will be able to improve on a Porsche 944S2 engine design ? I admire your optimism

If you throw enough money at it you could probably improve the power output quite a bit but one could argue that the money would be better spent buying a more powerful car for less outlay and no work.

Its all about keeping things in perspective.
If you remove both the seats and replace them with 2x lightweight race seats you would probably gain far more power output than you ever could gain by working the head no matter what you spent on it. !

If it is your intention to work on the head no matter what the cheapest and most effective route of increasing power is, then that is what you will do ....
If your intention is increase power and speed by the most economical and effective means possible then you are approcahing the problem from the wrong angle.

Look first to see how you can reduce the power output required !. ie reduce weight and drag .
Working on those two issues alone could potentially gve you more power and speed that even bolting on a turbo charger and they would probably cost next to nothing.


First of all decide what it is you want to achieve. Faster acceleration ? higher top speed ? Faster acceleration in a given power band ? faster cornering speed.?
Improving your braking into corners or improving your cornering speed would make your car faster than an otherwise identical car because you could brake later and corner at a higher speed yet the other car has an identical engine and power output you see?

Hi

I have kept out of this thread until now as my power comes from a different way ...see my signature....

But Peanut is absolutely correct, and I used to be a race mechanic who built engines with 5000 to 6000 hp....

I use Nitrous to give me my extra performance and you know what I did internally to my 928 engine (which by the way is basically 2 x 944 engines in one.... I did absolutely NOTHING....

Porsche design VERY VERY good engines, which are EXTREMELY hard to improve on, take my word....

Your best bet, as has been said is to decide what you want to do with the car....

Top speed.....

1/4 miles....

Track work...

Once you have said what you want, there are a lot of experts here (most are already in this thread) who will help you get what you want....but raising the compression ratio or re-porting an already almost perfect head is not the way to go to do it....

All the best Brett

Increasing an S2s output isnt particularly difficult. By this, I mean that it wont require cunning trickery or lengthy development. What it will require though; is a disproportionately large amount of money spending, relative the the vehicles worth.

The engine itself isnt going to be improved without great expenditure and a lengthy development process, Porsche, better than most manufacturers, really know what theyre doing. Of course: just beciase theyve developed a power unit which is difficult to fundamentally improve upon, doesnt mean that they want it to perform as well as it is able.

Because the manufacturers principal product only produced 240bhp at the time, the 944S2s output was throttled with the emphasis placed on torque and drivability (beyond a manufacturers usual interest in lowering costs by building one base car for all markets and allowing for reliability even after poor care and maintenance).

So, while the cylinder head is beautiful and difficult to improve upon, the vehicle is hobbled through the use of extremely conservative camshafts (both lift and duration/overlap) and primitive (by todays standards and difficult to work with) Bosch DME. To a lesser extent the inlet tract is restrictive too, but this isnt as important because it suited Porsches search for tractibility and youll have to remove it all in order to fit a MAP-based replacement fuel and ignition control system. Add to that the cost of a pair of bespoke camshafts and the associated setting-up costs and youre looking at a relatively straightforward, but prohibitively expensive procedure.

I think that presuming that simply increasing the compression ratio or fitting a different airfilter or exhaust will make a worthhile difference, is foolish in the extreme.

Brett This is not an S2. The gains on the 8v head are good. Technology has moved on. Not worth it £ for £ though. Best bet is an engine swap or Nitrous. Problem with both is insurance. But flow gains in the order of 25% are not a waste of money! And thats with the standard valves. If your head needs attention anyway it doesn't cost that much more to do it right! Certainly good enough to toast the stock clutch.
A good book on fuel injection is the Haynes Automotive fuel injection. Covers Bosch K jetronic in some detail & all that leads up to it. It's actually a good system. Ninemeister spent thousands on throttle bodies & didn't gain a single horsepower. Remapping it is cost effective & it works. Cam profiles are limited by engine design. There is little clearance for the lobes in the box as it is. They do produce more power but cost lots. Really on the 2.5 unless the engine is fit & can take Nitrous. I'd recommend an engine swap if power/£ is the goal. Tuning tired engines is a waste of money.

Hi

I was trying to avoid recommending Nitrous as everyone thinks i am a little biased lol ( I am by the way)

But lets look at Nitrous...a Wizards system WITH a controller so you dont toast the clutch will cost you around £1000 to £1200 for an increase of between 100 and 150 hp, which is about as safe as you could go I would think on that engine (assuming its in reasonable nick)

To get 100 to 150 hp on engine mods is going to cost you several thousand minimum....

All the best Brett

I think we are wasting our breath Brett.

Its clear that some posters do not even understand the significance of 'power to weight' ratio.

The Porsche 944 engine is a well designed and efficient engine in the first place but it is lets face it, the design is over 25 years old !
Developing the engine for substantially more power is going to cost a lot of money and give severely diminishing returns given how well developed it is as standard.

The 944 body is as aerodynamic as a brick in modern terms and to add to that as heavy as a combine harvester.

The first thing anyone should look at before spending any money on cylinder head development is to reduce the huge drag coefficient and to reduce the huge weight that the engine is trying to shift.

Attending to both of these factors first will give huge power gains with the absolute minimum of spending. BUT this is not as sexy as pretending to work on gas flowing improvements on the already well developed cylinder head. Thats all I am going to say on this issue now as it is clear that you can bring a horse to water but you can't make it drink !

Weight reductions is really a wasted off time, when your only got 150hp 2 start with. Your be hard pushed 2 strip 100kg. And keep a the car in a presentable order. 100kg is close 2 the weight of a grown man or your mate, so as soon as someone else sits in the car its lost. Now if you had a turbo with 200-300 a 100kg weight saving would make a huge difference. But only because you got the power 2 weight allready there. Engine swap would be best 2 go chevy. Not a Porsche but ur get a brand new engine and upgraded parts
will be new.

How offeten are you hitting the redline? Once you got the power u dream off will you ever use it?

Nitro seems the best, 4 a quick feel off that power.

But then 100hp+150 is really only the start off a turbo?

You couldnt be more wrong. Even 100kgs will make a very noticeable difference, and not only to acceleration, with improved dynamic performance and greatly improved braking too.

Lets not confuse 'our opinion' for fact.

I couldn't agree more about weight loss. But if your head is off needing a rebuild the small extra to gas flow it properly is worth it. The dyno doesn't lie. The 8v head is less than perfect. Though if my head is pretending why did it kill a clutch that had less than 40K miles on it! The old clutch was like new. Why am I having to use an uprated turbo clutch on my lux? Mine is a road car not a track car & I like the linen leather even if it does weigh a ton. I also need the back seats for my daughter so stripping the car out is a non starter. I would love to put nitrous on it but it's an insurance nightmare. You obviously didn't read my post. I repeat £ for £ it isn't worth spending on the 2.5 engine.

I can see the advantage off weight loss, but it would need 2 be seriously strip out, 2 see any real gains from such low power. Can't really say iv noticed a huge change between driving alone and with a passenger.

As 4 facts or numbers it's only a online calutour, but are these figures something you would notice in everyday driving? He's not looking at lap times/track car. if he was suspension set up would come b4 power. Now if u lose 100kg from a turbo it starts 2 seem worth it!
Power at Flywheel (BHP) : 150
Weight without Driver (KG) : 1180
Power to Weight Ratio (BHP Per Ton) : 129.16
0 - 60 (Secs) : 8.07
0 - 100 (Secs) : 23.92
60 - 100 (Secs) : 15.86
Quarter Mile (Secs) : 16.52
Terminal Speed (MPH) : 83.08
Drag Strip Quarter Mile (Secs) : 16.42
Drag Strip Terminal Speed (MPH) : 84.04


Power at Flywheel (BHP) : 150
Weight without Driver (KG) : 1280
Power to Weight Ratio (BHP Per Ton) : 119.07
0 - 60 (Secs) : 8.70
0 - 100 (Secs) : 26.58
60 - 100 (Secs) : 17.88
Quarter Mile (Secs) : 17.15
Terminal Speed (MPH) : 80.32
Drag Strip Quarter Mile (Secs) : 17.05
Drag Strip Terminal Speed (MPH) : 81.24