engine upgrade

[zcacogp]

ORIGINAL: morris944s2john Unfortunately the only person on this message board who has experience of a Nitrous Porsche left the board under unfortunate circumstances.[][&:][8|]

Sadly, that person confirmed a lot of stereotypes about people with nitrous cars, and has forever tainted the notion of a 'Nitrous Porsche' in my mind. (I'd also add that Porsche engineering is generally excellent, and adding nitrous has always struck me as a cheap-and-nasty alternative to doing the job properly. But maybe that's just me.) Oli.

 

[idwoodvale]

Sounds like you're really going for something that is 'yours', a bit unique. That's sort of where I want to go. Given the money you must be looking at already then I'd definitely think of an engine transplant as the starting point. I love the mid range pull of the 2.5 engine and an sorely tempted by the S2 - thats the route I'm likely to be going down. At some point though I'll probably be wanting a Turbo lump - my mind seems to change with the wind at the moment. Good luck with the project[]. Hope all turns out well. On the subject of a vented badge panel... Does this work as a direct feed into the S2 air intake? - sort of a bit of forced induction. Perhaps with MAF in addition? I fear I may be exposing a complete lack of knowledge here[&:]

 

[pauljmcnulty]

Unfortunately the only person on this message board who has experience of a Nitrous Porsche left the board under unfortunate circumstances.

Those who follow Pistonheads will know that he's still refusing to run the car in public, some years into the project, despite his claims. 'Nuff said! [&:]

 

[Peter Empson]

ORIGINAL: idwoodvale On the subject of a vented badge panel... Does this work as a direct feed into the S2 air intake? - sort of a bit of forced induction. Perhaps with MAF in addition? I fear I may be exposing a complete lack of knowledge here[&:]

I doubt there's much ram air effect going on sadly, the vents in the badge panel are at a very low pressure point on the car (there's a drawing somewhere of the pressure at various points, I'll post it if I find it) so I don't think there's a great deal of air going in. The intake really needs a J pipe on the S2 to get it to fit, so the air is at 90 degrees to the actual inlet pipe, I'd expect excessive air will just blow across the filter, but it at least allows the egnine to suck cool and relatively low turbulence air.

 

[Tam Lin]

ORIGINAL: Peter Empson the vents in the badge panel are at a very low pressure point on the car (there's a drawing somewhere of the pressure at various points, I'll post it if I find it) so I don't think there's a great deal of air going in. The intake really needs a J pipe on the S2 to get it to fit, so the air is at 90 degrees to the actual inlet pipe, I'd expect excessive air will just blow across the filter, but it at least allows the egnine to suck cool and relatively low turbulence air.

Hi Peter, 1) Are you sure? If you're thinking of the spoilerless 924 pressure distribution diagram, then have a look: The way I read that, the pressure point distribution is rather oddly spread, some being underneath the front bumper. Certainly, having a low pressure area smack on the front of the nose is a bit counter-intuitive to me. 2) On the German Transaxle site, some people have reported M44/41 engines going too lean on the Autobahn & burning pistons, because of a kind of ram effect. Apparently, a flap that should seal the area underneath the badge panel above the radiator often sticks open. The barn door air meter is wide open from about 5400 rpm, so the engine is running only on the WOT map. This, if the reports are correct, is not rich enough to allow for even the minor ram effect the open flap causes. I can link you to the thread, if the Mods here don't mind, and if you speak German.

 

[Tam Lin]

ORIGINAL: idwoodvale I'd definitely think of an engine transplant as the starting point. I love the mid range pull of the 2.5 engine and an sorely tempted by the S2 - thats the route I'm likely to be going down.

Agree[], here's one made earlier [link=http://sqirl.midsun.co.uk/f1gallery/main.php?g2_view=core.ShowItem&g2_itemId=632]http://sqirl.midsun.co.uk/f1gallery/main.php?g2_view=core.ShowItem&g2_itemId=632 [/link]

 

[Peter Empson]

Hi Sean, That's the one I was thinking of but I can't find it anywhere. I must have read it wrong then, but it definately looked to me like the angle of the badge panel was in a (relatively) lower pressure zone than the front. The more vertical location of the opening on the S2/turbo front bumper had much higher pressure. I'd like to see a link to the thread if you wouldn't mind, I don't speak German but I will babelfish it (it's more amusing that way []). I've always thought a 924 is a great place to start with these mods. The afm looks a little squashed in there, I'm surprised it fits so well. One thing we found on my car was that the length of the pipe between the filter and the afm made a difference, too short and we perceived less torque (backed up by a dyno run on another car) which is why we run quite a long J pipe. Sadly it's not something that'll be that easy to try in your location though!

 

[Peter Empson]

Finally found it... It was just before point 10 that I was looking at. I would appreciate any thoughts on this as I'm not sure what to make of it now.

 

[Tam Lin]

Hi Peter, Yep, that's the one I was thinking of. Now imagine the 924T nose slots at about the pressure point 1/2 way between 8 and 10... Linky here [link=http://www.mytransaxle.de/forum/showthread.php?t=1940]http://www.mytransaxle.de/forum/showthread.php?t=1940[/link] Text here: In der letzten Zeit habe ich einige S2 Motoren angeschaut, die plötzlich auf mehreren Zylindern gefressen haben. Es ist jeweils bei zügiger Fahrt um 200 km/h passiert, ohne dass der Motor extrem belastet wurde oder irgendetwas Auffälliges vorgefallen wäre. Bei ALLEN diesen Fällen war allerdings die Entlüftungsklappe des Luftfiltergehäuses verklemmt. Es ist also ratsam, mal nachzuschauen, wie es am eigenen Wagen aussieht. Der motorkillende Effekt tritt nur bei Drehzahlen oberhalb 5000min-1 ein, wenn ich bisher aufmerksam gelesen habe. Bei dieser Drehzahl ist die Drosselklappe fast vollständig geöffnet, ergo auch die Staudruckklappe der LMM. LMM und MAF verhalten sich in diesem Drehzahlbereich also annähernd gleich, will sagen: der systembedingte Nachteil des LMM (luftverwirbelnde Bremse) fällt kaum noch in´s Gewicht. Der MAF misst die Masse der durchströmenden Luft - egal wie stark sie verdichtet wurde. Umgerechnet wird auf das expandierte Volumen auf Meereshöhe. Aber beide Systeme (MAF und LMM) sind so ausgelegt, dass sie bei knapp 5.000 1/min am Anschlag sind. Darüber fährt der Motor nach Vorgaben der DME. Beim 951 sieht es etwas anders aus. Auch dort sind die Systeme bei 5.000 1/min auf Anschlag - aber der MAF entlastet den Turbo im Ansaugbereich und ermöglicht einen höheren Volumenstrom und somit höheren Druck im oberen Drehzahlbereich. Der LMM ist also die begrenzende Engstelle im System. Nur ist das DME/KLR System in 951 so aufeinander abgestimmt, dass durch die KLR der Druck gesteuert wird und die DME darauf abgestimmt ist. Im Vollastbereich fährt der Motor quasi mit einem passiven MAP System. Solange die beiden Abstimmungen passen, hilft der MAF nur, diese Vorgaben zu erreichen. Bei Systemen mit veränderbarer Drucksteuerung (Dampfrad, etc.) steigt der Ladedruck durch ein MAF spürbar an und muss durch Nachjustieren der Regelung oder durch zusätzliche Einspritzmengen kompensiert werden. Sonst wird es mager...

 

[Tam Lin]

Oh, and Happy Ney Year, all in GB.. and earlier/later, everyone else!

 

[Fen]

ORIGINAL: pauljmcnulty

Unfortunately the only person on this message board who has experience of a Nitrous Porsche left the board under unfortunate circumstances.

Those who follow Pistonheads will know that he's still refusing to run the car in public, some years into the project, despite his claims. 'Nuff said! [&:]

The one time I saw it it wouldn't start, which had the same effect.

 

[Peter Empson]

Thanks Sean, I'll have a proper read of this a bit later when my head stops throbbing. Happy new year all! Lately has I unite S2 engines looked at, which ate sudden on several cylinders. It happened in each case during brisk trip around 200 km/h, without the engine was extremely loaded or something remarkable would be before-pleased. With ALL these cases was however the exhaust flap of the air cleaner housing blocked. It is thus advisable to check times how it looks at the own car. The motorkillende effect enters only at numbers of revolutions above 5000min-1, if I read so far attentively. At this number of revolutions the butterfly valve the stagnation pressure flap of the LMM is nearly completely opened, ergo also. LMM and MAF behave in this speed range thus approximately directly, want to say: the system-dependent disadvantage of the LMM (air-swirling brake) falls hardly still in´s weight. The MAF measures the mass of flowing through air - no matter how strongly it was consolidated. One converts to the expanded volume to sea level. But both systems (MAF and LMM) are in such a way laid out that they are with scarcely 5,000 1/min at the attack. Over it the engine drives to defaults of the DME. With 951 it looks somewhat differently. The systems are also there with 5.000 1/min on attack - however the MAF relieves the turbo within the sucking in range and makes a higher flow rate and thus a higher pressure possible in the upper speed range. The LMM is thus the limiting bottleneck in the system. The DME/KLR system is co-ordinated only in 951 so that by the KLR the pressure is steered and the DME with it is co-ordinated. In the full load range the engine drives quasi with a passive MAP system. As long as the two votes fit, the MAF helps only to reach these defaults. In systems with changeable printing control (steam wheel, etc.) the load printing rises by a MAF noticeably and must be compensated by readjusting the regulation or by additional injection amounts. Otherwise it becomes lean…

 

[pylonracer]

Peter In the pressure distribution chart do you know what the pressure scale at the left is calibrated in? I seem to remember some years ago when I was working on Simtek F1 cars, being told by an engineer that the highest pressure in the airintake was 33mb. I have just done a quick bit of Googleing on ram air and come up with this site with info that supported the 33mb.[link=http://www.sportrider.com/tech/146_9910_ram/index.html]http://www.sportrider.com/tech/146_9910_ram/index.html[/link] In the case of a race engine they cannot afford to give the 33mB away but I have always belived that in an application of the type that we are talking about, that the benifit of a ram air type intake is the cool and fresh air that it supplies, the vehicles will rarely go fast enougth for any ram air effect to take place. I belive you were thinking along similar lines. I would think those 924's going pop on the Autobahn were probably running a little on the edge and detonation set in with associated heat build up. Barrie

 

[Suffolk944]

Think I understand more of the original German text than the babelfish translation [8|]

 

[Neil Haughey]

I can't speak German but the diagram seems to be saying that the 0 is the reference pressure, perhaps 15 psi or whatever it is and the Y axis is showing pressures above and below the reference. If this is the case then surely the pressure at point 10 is OK because its pretty much on the axis. Its way better then some of the other points for example.

 

[sawood12]

The y axis appears to be showing Cp which is the Coefficient of Pressure which is a dimensionless number and so is representing a relative distribution of pressures over the car. I'm not sure if 1.0 or 0 represents atmospheric pressure. These numbers are generally measured in wind tunnels at very specific set of conditions. Without knowing those specific conditions it is difficult to determine the absolute values. It's like when car makers advertise a car's coefficient of drag. So what. It is meaningless and doesn't mean that one car with one Cd is more or less aerodynamic than another car with a different Cd.

 

[333pg333]

ORIGINAL: Peter Empson Hi Neil, we can hear you, no need to shout [] I think Nicholas has explained why he wants to keep his car. To be honest I'm not sure the brakes and suspension are the handicap most people would probably imagine. Let's face it, it will be fairly rare to buy a car with recently replaced suspension and rebuilt calipers, so there's quite a bit of work and cost ahead to bring it up to spec anyway. If he is going to run a tuned 944T engine then he can skip the medium black and go straight to the big ones and put a suitable suspension setup on which will be much better than the stock S2 or Turbo setup. This could use up say a third of the budget mentioned leaving plenty left over for the engine and drivetrain. Patrick, I have to admit that most american V8's just don't do it for me. I know the 4 cylinder isn't the best sounding engine, but I am not keen on lazy sounding V8's either. Can't deny the power potential, but I'd still rather have a tuned 944T lump myself [].

Peter, I agree with you in principle and passion, perhaps not in outright performance vs costs. It doesn't seem right to me either and that's why I've gone down the road that I'm in now. (Seems more like a cul-de-sac or roundabout at times. []) It is possible to get some decent power out of a 4 banger and I also believe you can make them sound pretty good (for an i4 motor). The V8 can be had pretty cheaply especially with your still strong pound. It can be modified very simply to make big flat power and the reliability factor can't be ignored. Anyway I hope that you're project blooms fully in 2009 and proves to be a unique and highly satisfying car. My latest version of a 3L turbo is almost built. Should be another couple of weeks. It is being designed to run with E85 as well as normal premium. Should be good for 30psi dyno days and 25psi all day long. Expecting well over 500hp so I don't know why I'm pushing for a V8. [] Happy new year to all for 2009. Patrick