Hi
my friend just had his 98' 996 (DME5.2) in for a cam upgrade, when he got it back there was a real heasitation, stumbling when flooring it.

We did log o2 values with durametric, and saw that bank1 voltage droppes when flooring it (lean)

RPM Throttle Bank 1 Bank 2 (02 voltage)
opening
3440 0 -0,01 -0,01
3320 9 0,01 0,8
3280 12 0,06 0,07
3520 67 0,77 0,11
3760 67 0,02 0,91
3840 67 0,01 0,83
3940 25 0,01 0,82

Throttle need adjusting( wire) will only go to 67% when flooring it. 80% if i push the butterfly valve by hand. Where to adjust?

If we drive with about half throttle it will stay at about 0.7-0,8v on both o2 sensor til red line. Trying to floor it results in studdering because bank 1 goes absolutely lean.

We are concluding either the fuel pump suddenly cant deliver (bank1 and bank2 are in series so maybe on bank is able to get the fuel it needs and the other has a lower pressure)
Or that the mechanics left something in the fuel line which clogs it (engine has been out of the car)

Is there antyhing else that can lead to on bank shutting of fuel?
i don't think ecu can fuel differently on bank 1-2 , there is only one inj opening time table in durametric

 

If the engine was running ok before the cam upgrade but is not running ok after... the cam upgrade was a downgrade.

That is the camshaft installation is suspect. I'd take the car back to the shop that did the work and have them diagnose the source of the behavior.

What do the short and long term fuel trims look like?

Sincerely,

Macster.

 

Cam Upgrade?? I was not aware that there were alternates to the OEM cams.

 

FVD makes cams for the 996; you will have to remap your ECU and find an installer who really knows what they are doing... that's major surgery.

 

Plus 1 on taking it back.

 

it's an FVD kit, cams, intake filter, ecu
The car was running fine with the fvd ecu for a couple of months before the cams were installed.
Cam positions has been tripple checked by the dealer.
A wrong cam positions wouldn't cut fuel in this manner anyway, car idles perfectly and runs fine as long as you don't floor it, because fuel delivery is ok.
Im not sure where the short and long term fuel tables are, found some FRA TRA upper lower range tables , they were within normal i think -1,7 and some at 7.
I don't think the DME 5.2 is very intelligent, it doesn't throw any fault codes.

 

Under some conditions -- hard acceleration being one -- the DME suspends emissions monitoring. Since emissions aren't be monitored the DME can't note the readings are out of spec and turn on the check engine light and log an error code.

As you relax the pressure on the throttle and the DME resumes emissions monitoring the condition you noted during hard acceleration is no longer present.

If the engine's going lean on one or both banks then obviously the fuel supply has to be suspect.

It is not impossible to imagine that during the camshaft installation and the several times the cam timing has been checked that a fuel line got pinched, crimped or the vacuum line to the fuel pressure regulator got damaged (or simply failed due to being handled) and the fuel pressure drops off under hard acceleration.

The DME assumes a given fuel pressure and bases the amount of time it turns on the fuel injector on this pressure. A lower pressure will find less fuel injected. Under more normal operating conditions the DME will note the lean condition and increase the time the injector is open. Short term and even long term fuel trims will move to the enrichment threshold.

However, as I noted above, under some conditions the DME suspends the normal fuel monitoring simply because it has to supply a richer mixture (to satisfy the torque demand from the driver) and the O2 sensors would read goofy.

In short, check the fuel pressure and fuel supply would be my advice. Give a good inspection to all fuel lines and vacuum hoses/electrical connections to the fuel pressure regulator.

Sincerely,

Macster.

 

Ok so here is the link to the FVD cams for a 3.4 996.

http://www.fvd.de/us/en/Porsche-0/-/...pc-Set%29.html

I'm thinking only $2,779.11 plus shipping, another couple of grand for the install (unless I do it myself), then a reflash for $1,000+ and I can have a car that runs crappy. Hummmm! Tempting

 

All kidding a side, I am curious as to what FVD says the advantage/power increase is for this upgrade.

 

Ditto. I saw this a while back and ???? myself.

I would rather have a super charger.

No, how about a turbo.

Seriously though how does the original map (if advisable) work? Or perhaps put the old cams back in?

+1 to macster, I would probably check the fuel rail outputs.

 

Here is the kit installed 335HP / 284LBF FT

http://www.fvd.de/no/no/Porsche-0/99...LBF-FT%29.html

MACSTER

Yes we saw that when not at WOT the o2's are in closed loop, so when at WOT it will use pre defined tables, i know som bosch ecu, will be closed loop at wot up to certain rpm.
Did check the fpr , but since it's a NA car, only vacum will decrease pressure, so if it was leaking or not the vacum hose not instaleld it would still have the correct pressure (unless it's a turbo car of course)
We will measure fuel pressure when driving this weekend while driving to see if it's keep up, and remove fuelrails.
Did check the fuel lines going over the engine, quite tight space there, but i was able to pull and push both feed and return lines and see movement on the other side.

 

Can't get that link to work.

 

Here is a US link
http://www.fvd.de/us/en/Porsche-0/-/...LBF-FT%29.html

 

I'm always a bit skeptical when a shop/dealer/anyone tells me something's been checked 3 times.

I can't believe a shop would continue to employ a tech that had so little confidence in his skills or the shop had so little confidence in his skills to require he check/recheck the cam timing 3 times.

Once should suffice.

Actually getting inside the engine to check/verify cam timing is alot of work.

Nor would I expect a shop to eat that kind of labor and parts cost (for instance the camshaft covers have to come off and my info is the camshaft cover bolts should not be reused).

With the proper PST2 and know how the cam timing can be triggered for each cylinder. Has this been done and have you gotten a copy of the results?

Sincerely,

Macster.

 

In my experience, changing camshafts effects tuning more than anything else that can be altered in the M96 engine. I have never applied performance camshafts to an engine without having to tune the ECU.