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YOUR RESEARCHMy car is down on power!
Reported repair
Combined work: Clean maf and it cleared the cel + Replace new
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Reported fix
When I had aCEL last year I cleaned my MAF and it cleared the CEL, but only temporarily. A new replacement solved the problem for me.
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Performed · outcome unconfirmed
When I had aCEL last year I cleaned my MAF and it cleared the CEL, but only temporarily.
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Performed · outcome unconfirmed · Original poster
Ok so I swapped coil pack 1 and coil pack 3 round then cleared the CEL and went for a drive.
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Suggestion · Original poster
I had a ride out today and noticed my car has no such kick/pull around 5000 rpm where the variocam is supposed to adjust the cams I believe.
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Hi this is my first post here so i'll attach a pic of my car too.
My car is a 98 996 c2. The car has 49k miles and has just had a full service in the last 1000 miles.
I took the car to a dyno dynamics machine to see what power it is, the results were very disappointing. It got 225bhp at the wheels 275bhp at the flywheel
So its basically 25bhp down on a standard car.
The engine is standard apart from a k&n CAI and PSE.
Can anyone suggest anything I could check on my car to work out why its running down on power?
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Beautiful car! Because you have an after market CAI, I would suggest cleaning your MAF sensor. I replace mine every 25 to 30K miles because I get oil on my sensors from 1st gen EVO CAI. I notice a big difference before and after. Fuel filter replacement is also recommended every 60K miles. Plugs and coil packs?
10 different dynos = 10 different results
There are no universal standards for dynos, most results I see are optimistic, some tremendously so!
If you seriously think you have a problem, have your car checked by an Indy or Porsche dealer. A quick test drive by a tech will reveal more than your dyno sheet. GL
plugs (old wrong ones)
maf (dirty, oiled)
fuel (bad fuel)
fuel filter (dirty, clogged)
CAI (maybe worse than stock)
Dyno set up wrong?
cats (plugged)
mufflers...missing or altered
full diagnostic on cam possitions (one bank off position to the other - cam solenoid)
steering wheel on the wrong side.....
nice looking car
Your '98 C2 is certainly a looker! Can't add much to what has been suggested, but can you drive a friends C2 so you can make a seat of the pants evaluation to compare the power of each?
When I had aCEL last year I cleaned my MAF and it cleared the CEL, but only temporarily. A new replacement solved the problem for me. There is a tamper proof torx tool you'll need, other than that it is very easy to do and might be worth your effort. Do a search and you'll get all the specifics.
Thanks for the suggestions keep the coming!
Car had major 48k service at Porsche 1000 miles ago.
plugs (old wrong ones)
just replaced at 48k major service
maf (dirty, oiled)
Has had a new MAF in the last 500 miles !
fuel (bad fuel)
Always ran on uk 99 ron fuel basically the best stuff we can get here.
fuel filter (dirty, clogged)
just replaced at 48k major service
CAI (maybe worse than stock)
Maybe but I thought it was supposed to add power? I will try car with stock setup back on.
Dyno set up wrong?
Other cars on that day were getting good results, Ive heard dyno dynamics is the most reliable and accurate dyno around?
cats (plugged)
Not sure what how I could check this?
mufflers...missing or altered
standard exhaust/headers with PSE mufflers
full diagnostic on cam possitions (one bank off position to the other - cam solenoid)
Would I take it to Porsche to check this out?
steering wheel on the wrong side.....
Also coil packs would have been changed at the 48k mile service I think.
Because my car is a 98 it has a cable throttle so I have checked to see if it was stretched and not opening the throttle valve fully but it looked ok.
not really. Butt dynos are hideously unreliable. A tech might be able to detect a problem with how the car runs, but its rare for someone to notice 10-15 hp missing.
dynos are only are reliable as the information inputted into them. I believe a dyno dynamics is a load bearing dyno, and you need to input the weight of the vehicle. If you get that wrong, it can sway the results. They also tend to show lower results than a dyno jet.
How did you attain the flywheel numbers? Were they derived from the RWHP values? Few people have an M96 engine dyno (we do! :-)
A normal 3.4 996 makes 240RWHP on my dynojet over and over again..
It was run on a dyno dynamics rolling road which measures rwhp then somehow calculates the braking resistance of the drive train to calculate a flywheel power figure.
The guy who owns the tuning company and was dynoing my car said it was accurate up to 0.1hp.
On the uk 911 forum there is a guy who has made 245rwhp/297fwhp on a dyno dynamics dyno. So I guess thats where mine should be.
I dont think the airbox will make 25bhp difference but will try and fit it when I get time and see if it makes a difference.
Is there anything I could check to see if the variocam is working as it should?
Thanks, it is a great looking car just wish it would go like its supposed to!
The guy only emailed me the graph with flywheel power.
Bit hard to see you might have to zoom in but the orange lines are with a faulty MAF sensor, only hit 170 fwhp!
The blue Line was with my faulty MAF sensor disconected.
The Pink line is my car with a new MAF sensor in its current state. 274 fwhp 225 rwhp and 235 ftlb of torque.
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It might make more sense if the results were not corrected. I could see a variance from of 25HP due to conditions. If those were your corrected results, your car is closer to 200 rwhp... doh!
-td
Hi just to update.
I haven't drove the car for a week so went out for a brief drive but the CEL came on and the car started to run a bit funny so I drove it back home really easy.
Now if I start the car the CEL is on constantly
I just tried the car with MAF sensor disconnect to see if it would stop the cylinder 1 misfire but no difference so that kinda rules out the MAF sensor.
To check the coil packs do I just swap them around to see if the missfire moves to another cylinder?
Ok so I swapped coil pack 1 and coil pack 3 round then cleared the CEL and went for a drive.
CEL didn't come back on so misfire seems to have gone which is strange.
Car still seems to be running at low power though so I need to investigate further.
People have suggested cats and o2 sensor, how do I check for faults with the o2 sensor?
Dyno
actual
values can be different from the
reported/corrected
values. That is, the dyno operator can input some conversion factor for conditions like temperature, humitidty etc. Whatever is actually measured gets multiplied by the conversion number to come up with the 225 number. Some places provide both the actual and corrected values.
My point was that getting 225 as a corrected RWHP number may mean a lower actual reading.
-td
***Update***
Took the car to a specialist and he diagnosed my car with possible faulty variocam solenoid on bank 2.
Hopefully a new variocam solenoid will cure my low power issue.
I will replace this and get a re run on the dyno
that is certainly worth 25 hp... do you feel a dead spot in the rpm range... say between 4-5500 maybe?
get rid of the CAI... go stock box with K&N or BMC air filter...
also your GT3 rims look nice but they are *heavy* and heavy rims eat up horsepower and it shows up on a dyno as well... if you get rims that are 10 lbs lighter per wheel than what you have now you will easily see a 10-15 hp increase on the dyno because its making it to the ground vs disappearing due to that hp turning the extra mass on the wheels...
Not sure I can notice a flat spot at those revs as I think the car has been this way since I bought it.
I may try the stock airbox.
The rims are sport classic II, not sure on the weights. I'd like some oz allegeritta but at the minute I can't really afford to spend money on expensive mods for the Porsche.
I'd just like my car to have stock power as it should. The specialist I was talking to told me every 996 engine was bench tested by Porsche and if they didn't make the 297 bhp they were binned at the factory.
They test to see which gear is best before doing the power run, don't know how they work out which gear is best?
I think 4th gear was selected for my runs.
sport classic II are definitely on the heavier side... bout 27 lbs each... the OZ Allegerita are nice and light in 18" size... like 17 and 18 lbs front to rear...
you will feel the difference with a 10 lb change in rims... also in deceleration and braking...
That does sound like a great way to save weight and increase performance. I'd love a set of allegerittas as with the offsets i wont need to buy wheels spacers either..but all my money's being spend on my supermoto project now, Porsche will have to wait for now.
If I can get a new variocam solenoid fitted to bank 2 and my car returns to stock power I will be happy
strange.... that solenoid is only a coil, not much to break... make sure that the you have good electrical contact.... unplug, clean the contacts and re-plug. Putting in one of those is serious money.
The Porsche Indy said it's quite a common thing to go wrong.
I had a ride out today and noticed my car has no such kick/pull around 5000 rpm where the variocam is supposed to adjust the cams I believe.
Can someone confirm if their car has some noticeable change in acceleration around the 5k rpm mark?
No, I think that the 5th will give the correct number.
Stock 300hp - 15% is 255hp, so I think thats in the ballpark.
I think that the 5th gear is closest to 1 ratio. So this gear should be used when car is dynoed. Even thou the wheelspeed's go up to 240kmh (150mph)
And for the rpm's, my car does wake up after 4500rpm. You can allso hear the engine change in the engine sound.
Are you running a cat? Rich mix? Maybe one side is slightly clogged? I had a 95 993 and it was down on power - but noticeably, at high RPM. One side of the cat was clogged - verified by IR temp gun - fixed with replacement cat. My .02 cts worth without having read the entire diatribe...
Too bad you have a 98 996, I'm stuck in the same boat with a 99 and some potential cam related noises, but I'm pretty sure mine are tappet noises from the cam followers. Our 5.2.2 ME DME cannot read the variocam actuation values like the 7.2 or higher can... the only test we can run is for camshaft deviation or cam actuation (either on or off). It's a simple test really if you have a Durametric or PST2, the problem being we don't know if the solenoid is fully actuated or not - that I can tell - using that particular drive test - just that the engine idle changes significantly as the cam timing is advanced. I'll know soon enough though and will probably bench test the solenoids since I've ordered new chains and ramps as well as some other bits and pieces. Hopefully the solenoids are ok and it's just some worn lifters.
Oh hey, did anyone mention cleaning your throttle body? That can have an impact on the cars performance as well.
On an MK1 car (1998 through 2001, 3.4 liter motor) if you can switch each solenoid at idle w/Durometric and idle speed significantly drops, the actuators should be working correctly. This is indeed not uncommon on the 3.4 and the solenoids do fail, however on a U.S. spec car the check engine light should illuminate in case of failure as it is considered to have an impact on emissions. If I remember correctly non U.S. cars don't have the "redundant" cam position sensors in each head and will not have a trouble code for fault in at least one of the Variocam actuators, which may very well be the problem w/the car.
Non U.S cars only have a cam position sensor on bank 1. Bank 2 has no sensor so like you say a engine fault lamp wont illuminate when theres a problem with bank2.
**Another update**
I had the solenoid in bank 2 variocam replaced in hope that this would cure my low power slight lumpy idle issue...
Unfortunately this has made no difference
when using the pst2 bank 2 varicam will still not activate. The mechanic thinks that the ECU/DME must be at fault.
From my understanding from what the Porsche indy told me, the solenoids in each variocam are switched on and off by the dme by earthing the circuits out. So pin 54 at the dme is a live feed for the solenoids and pins 25 and 52 are the earth connections for bank 1 and bank 2 solenoids. So im thinking maybe bank 2 has a bad earth connection at the dme.
Would it be ok to swap the earth pins around at the dme so bank 1 earth becomes bank 2 earth to see if bank 2 solenoid now works?
Also would I be ok to wire the two variocam earth wires to pin 25 bank 1 earth? if i find bank 2 earth pin to be faulty or would this fry my ecu?
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