Citroen C5 club forum

EvilTwin schreef:

Klussie schreef:Er zijn er een aantal die geen problemen hebben met een Hpi maar............
[..]
Als je er vanaf ziet krijg je roze sokjes van me.

Als je alles zou baseren op de allerslechtste ervaring ooit, zou er nooit meer iemand in wat voor auto dan ook rijden, of in een vliegtuig stappen, of de straat oversteken.
...of op gas rijden

EvilTwin schreef:The Citroën HPi was Europe's first direct injection petrol engine of the modern era (discarding WWII-era D/I)

As such they took a huge gamble. Mitsbishi were the first globally (GDi), and held certain patents which Citroën licensed. HPi functioning revolves around straifed lean burn, which has certain advantages, both in thermal efficiency, pumping losses and pure combustion.

It does so by injecting high pressure fuel into a stratified (layered) air mixture, effectively making the combustion chamber smaller. Interestingly the principle can be traced back all the way to Citroëns first Diesel passenger car, the 1934 Rosalie, which engine was designed with Ricardo UK.

HPi claims at introduction:

1) strongly reduce consumption
2) improve driving pleasure
3) improve the environmental friendliness

ad1) The key is stratified burn (lean mode) in PARTIAL load, IE. lightfooted driving: half-load and below 3500rpm. A 10% reduction is possible.
ad2) only true if you discard 1) and take advantage of the higher power/higer torque available at full load (non-lean mode) At least 5% increase in both power and torque can be attained, 10% if the HPi is combined with increased compression.
ad3) Reduced consumption means reduced CO_2 and lean mode means virtually no toxic CO and low HC. These are great advantages!

But there is a catch, since NO_x and soot (particulate matter) both increase with direct injection, especially in lean mode. The EGR (integral to lean functioning) helps reduce both, as it does in regular petrol engines of the same era, but the EGR valve is also extra susceptible to soot production (clogging up)

The HPi comes with an NO_x storage and release catalytic converter, but this is extremely susceptible to sulphur in the fuel.

All-in-all it already met EURO4 (ie 2004) regulations in 2000, when EURO3 was barely in effect! Since it undercut 2004 requirements by 25-50% it would currently come very close to meeting EURO5 (2009) This alone should have given the HPi a raison d'etre, but alas...

Technically it combines several innovations (outside of the Mitsubishi patents)
-air tumble
-NO_x storage (Barium catalyst)
-NO_x release/burn (3secs every minute)
-novel high pressure fuel pump (J-V between Citroën and Siemens)
-motorised throttle valve to reduce pumping losses.
-EGR valve not only regulates emissions, but power as well.

Weak points/disadvantages:
1) no reduction in fuel consumption outside of lean mode:
Big C5 /w 2.0L +spirited driving/towing/hills => no lean mode.

As such the combination of C5 and a larger 2.2L or 2.4L would've been much better to make operation in lean mode easier. The 2L HPi would've been better suited to the Xsara or Xsara Picasso. Mitsubishi used a 2.4GDi in their larger cars, a 1.8GDi in smaller ones.

2) EGR clogs up fast with a poor combination of loads and fuel, see 3) and 4)

3) extremely susceptible to sulphur in the petrol, as it interferes with the NO_x storage and release, leading to more and longer burn-offs and higher consupmtion, more soot and EGR malfunction.

ca. 2001 German Onzin had plenty of low-sulphur available (at a price), but much less in the Netherlands. German and Dutch HPis would not see much lean burn on the motorways either (at +130km/h)

4) HP fuel pump is lubricated with engine oil. So the HPi is susceptible to oil contamination (ash and soot). This problem is compounded by the additional soot production mentioned earlier, as the soot in particular contaminates the engine oil.

5) Misfiring, not really a specific HP problem, not even a Citroën problem as many early 2000s cars with coil packs (single coil per cylinder) seem to be affected. But once this occurs in the HPi the problems will multiply.

Summing all this up means that the particular advantages of the HPi, can only be used in specific circumstances. Once its use goes outside of the HPi's (narrow) comfort zone, efficiency will quickly drop, sometimes even leading to reduced reliability. Malfunctions on relatively simple stuff, like EGR, oxgen sensors and coils, can grow out of control.

Most real problems associated with the HPi, leading to its bad name, can be blamed on poor fuel and service; the former would currently be much less of a problem, the latter would be exacerbated by the fact that most HPis are now 8 years old.

pitalo schreef:
oke heb het los gehad kap er af dus zit er een bus waar rubbers inzitten die ligt los rest zit vast.
ja moellijk uit te leggen als je van boven kijkt is het de achterste nokkenas daar binnen in it een smalle bus een ring met binnen kant rubbers die ligt los.
nog even een vraag die electroklep waar zit die en weet je ongeveer wat die kost

groetjes fred

exroosje schreef:De tango heeft het nog wel, maar 10 cent duurder als euro 95
Daar gaat al je besparing!