993 911 CS - Rolling Road Results

[TD2015]

I have just had the car tested on a rolling road here in Chania, Crete. The results were not good and the mechanic wondered if the Porsche forum might have some thoughts on why.

The BHP recorded was 225 BHP at 5750 revs which is a long way off the manuals stated 285 BHP.

The mechanic had a fairly large air blower behind the open engine, although he did concede the air flow may not have been enough.

He also showed me results from a Cayman he'd recently tested. It had supposedly been chipped to 325 BHP but only recorded 285 BHP on the rolling road. Interestingly, the torque output for the Cayman tested was almost identical to the CS i.e. he laid both graphs over each other.

So any thoughts? We should have more info at the end of the week when he gets some further diagnostic stuff from a friend with Porsche, Athens but he did ask if I'd pose the question on the forum.

The car is tiptronic and the test was carried out in fourth gear. The room temp was 22.5C.

I've attached the graph to this post but any thoughts would be most welcome.

Cheers,

Jon

 

[cobalt911]

Hi Jon,

I have heard nothing really positive about rolling roads and the results they provide UNLESS it is more than you were expecting []

From my perspective I had mine to 265BHP which really disappointed me but both Peter Tognola and Ray Northway have taken it out on the road and think it is no different to the numerous other examples they have driven. I have a 100 cell cat on now but I am not sure I can even tell the difference!

The advice I have seen in the past is to try and find someone with another car like yours and try some rolling accelerations on a quiet bit of road....none of that is easy I would think! Have you timed a standing start to 60mph?

The other thing to check is the vacuum (on actuators etc) and see if that is ok but I would say you have to take every rolling road result with a pinch of salt (unless 10 of you with similar cars all have a go on the same day!). I have also heard that the kit needs regular calibration....

M

 

[burrow01]

What altitude is the garage at? - Sea Level?

You can only really compare rolling road dyno results on the same machine, but that does seem low - does the dyno get calibrated at all?

I've had runs on two different dyno's - one at 282BHP, the other @ over 300BHP with no engine work

Pete

 

[TD2015]

Update:

I've just had a call from the mechanic and he thinks the problem may be due to the flow meter. He will take it out and clean it tomorrow and then re do the road test. If he sees a significant increase in BHP e.g. 20 BHP he will order a new one.

Jon

 

[clyde]

Jon

Have a look over the results from the 993 dyno day last year http://www.porscheclubgbforum.com/tm.asp?m=372779

One car was down 30bhp or so with an issue with the varioram not operating correctly. Not as much as you seem to be missing but a start?

 

[TD2015]

Thanks Clyde, have printed off that thread + graphs and will take it down to the garage this morning so the mechanics can take a look.

Cheers,

Jon

 

[Porker993]

ORIGINAL: burrow01

What altitude is the garage at? - Sea Level?

To answer your question, Chania is at sea level. It's a port. Very nice too, as I recall.

 

[gzhpcu]

In the 964 the camshaft position was kept better in the factory measurement postion than in the 993. As a consequence there are discrepancies in the valve openings between the left and right cylinder banks. The opening distance is not documented by Porsche, but Porsche tuners have found out that the correct opening should be 1mm. An imbalance cause hp loss. My Porsche mechanic said that he has never seen a 993 with the correct and balanced valve openings. He has done the measurement and properly set the valve openings for many 993s, even for 993RSs and he said that each time he notices the engine becomes lively and he thinks that about 20hp can be recuperated

 

[TD2015]

Thanks guys for all your suggestions and advice,

I was down at the garage earlier and they checked the throttle actuator etc whilst I was there and all seems ok. (My can does not have cruise control) I've also given them the schematic for the vacuum lines and they will check those on Monday. Adonis - garage owner - has confirmed that the rolling road is fully calibrated and showed me the graph for a BMW 3 series he'd done earlier today i.e. only 3 BHP off the figure specified in the manual. He says at worst it might be 5% out but that calibration is not the problem.

He then overlaid the two rolling road tests from my 993 (I can scan and post later if anyone is interested) and pointed out that after they cleaned the original air flow meter with brake cleaner it showed an increase of 10 BHP on the second run + a small increase in torque. He still feels fairly sure this is the problem - although he's taking all your suggestions onboard and going through them one by one. The air flow meter won't arrive until Wednesday at the earliest so they have time to check everything else.

I've just sent him Maurice's thoughts along with Geolabs and will report back once he's checked them out. He does not have a Porsche diagnostic tool so it's trial and error at the moment.

I've also attached a pic of Chania harbour - one of the most pitcturesque Ventian built harbours anywhere in the Med.

Thanks again for all the advice - it's certainly great knowing there are others out there albeit 2000 miles away who freely give both time and suggestions.

Cheers,

Jon

 

[TD2015]

The air flow meter arrived and was then tested on the rolling road. The BHP increased from 225 BHP to 245 BHP. The mechanics checked the vacuum lines today and have just called to say there is nothing wrong there.

Adonis' only thought now - which is one he brought up after the first rolling road test - is there is not enough air getting to the engine, even though he has quite a large fan situated behind the car / engine when being tested. He says he has seen the same problem when he tests big engined i.e. 3500 cc and above - BMWs.

I've got to admit that when I road tested it last week i.e. before we knew the rolling road results, it didn't seem any different from before and in fact, because it had been serviced, it actually seemed tighter and more responsive.

I think the only solution is to bring it back to the UK and get it looked over by the same Porsche mechanic who checked it over before I bought it.

TD

 

[pse_SC]

Just a thought that might help...

Quite a while back, my Oxygen sensor (located in the exhaust) was replaced after being diagnosed as faulty after a lower dyno reading - made all the difference[]. Maybe be worth a try?