A Query for those technical out there

[ArthurPE]

Just a thought, if there is no vacuum in the system would this affect the compression test as this was doen when the vacuum was pinched?

I'm not saying you lost 10% torque, I think the readings are wrong...

I don't think vacuum would matter, it's just a mechanical pumping test basically

the bmep of 188 is with the engine at the sweet spot, vol eff >1
the comp test the vol eff is lower becasue the engine is turning slower

anyone with the shp manual? what is the spec?
I'm guessing 175-180 range

[adsgreen]

Just a thought, if there is no vacuum in the system would this affect the compression test as this was doen when the vacuum was pinched?

Compression test done with wide open throttle so vacuum non existent anyway. The only vacuum generated would be by the vac pump not engine.

Remember this was a cold test so is never going to be accurate in terms of absolute numbers.
My basis for bang on comment was the difference between all cylinders being so small. A cold test (dry or wet) is looking for one or two cylinders obviously down on compression not figures. Its a quick test that can be done on an engine with issues whilst keeping any further damage to a minimum. if you had a suspected damaged piston then the last thing you'd want to do is run it to operating temp. I guess you could connect the oil and water systems up to a heater as in f1 but overkill really.
If you want specific compression figures you need to do it with hot engine but that's not needed in this scenario.

[P_G]

To be honest I'm not too worried about it given the consistency across the cylinders. It's appears to accelerate thorugh to red line like it used to and I'll do 3-8k rpm tests today to see what happens. Anyone got a brief 'how to' log timings using VCDS to get accurate readings?

[2manytoys]

Log Group 3. It would be interesting to see Groups 11 and 20 also. Click the turbo button. Just set it to start when you pull up somewhere safe, then go and let it run up to redline. Pull up again and press stop.

Here is mine as a comparison. It's not technically the 3-8k test (not worthwhile) but you can see the timing and correction under full throttle (that tells much more).



This was from my new engine just after it completed the break-in.

Post up how you go as a comparison .

[Revolution]

Hi all,
Some great points getting posted up but we only performed a dry test at cold temperatures on P_Gs RS to ensure there was no significant differences between any of the cylinders.
This was done after we had visually inspected the insides of all the cylinders with our Borescope..(something Audi cant do LOL)
As we found no readings that caused any concerns I felt it uneccessary to perform any further compression tests as our concern was damage to one or maybe 2 cylinders due to ingestion of a foriegn body.
Thankfully as the consistent readings and our visual inspection informed us this is not the case.

As Glenn has already said, we pride ourselves on our customer service and are always happy to help out in any way we can, I have to say though, our car park doesnt look as good now P_Gs car is gone.

Little Glen
Workshop Manager

[P_G]

OK,

I need to tidy up the figures and for some reason group 11 and 20 stopped recording but my peak flow at 7920rpm was 153g/s with throttle angle of 99.6 and ignition timing angle of 30. Maximum ignition timing angle was 33. So fairly comparible to yours Mal? Looks like your peak airflow is some 10g/s (6%) better than mine.

Timings wise it was 17 degrees celcius outside temperature, full tank of V-Power, slight incline on a damp road (mileage 86174) and the DIS timings with ESP off were;

8.6
8.3
8.5
8.5
8.4
8.3

So near enough where it was before. Bear in mind that it is the first time the car has been driven in anger in three weeks and it was getting quicker as the afternoon wore on. I'll try and do the timings again with fields 11 and 20. I do however still have a N145 sensor code error on VCDS (open / non communication) so may have to replace the right engine mount solenoid at some stage although it is not throwing an EML / EPC light.

[ArthurPE]

the times tell the story...car runs like new after 86k miles, amazing...never cleaned
and on cold cylinders the lower numbers make sense...

still like to know the manuals compression test numbers...for future reference

[P_G]

It should maybe be a bit better given the porting / polishing but ultimately I believe further porting (didn't port the throttle body intake or runner flap shafts due to time / cost) and a clean will yield better flow rate because the valves are still the restriction. I'll give it a week of running and try the test again. I'd also be interested in seeing what happens when the torque limiter in the first three gears is removed given the runs is in third. 4th gear runs on the dyno WOT produced gains so I suspect the torque limiter is masking the true potential of the car timings wise.

For those who have had porting polishing done and valves cleaned, what peak flow rate have you been seeing?

[2manytoys]

OK,

I need to tidy up the figures and for some reason group 11 and 20 stopped recording but my peak flow at 7920rpm was 153g/s with throttle angle of 99.6 and ignition timing angle of 30. Maximum ignition timing angle was 33. So fairly comparible to yours Mal? Looks like your peak airflow is some 10g/s (6%) better than mine.

Timings wise it was 17 degrees celcius outside temperature, full tank of V-Power, slight incline on a damp road (mileage 86174) and the DIS timings with ESP off were;

8.6
8.3
8.5
8.5
8.4
8.3

So near enough where it was before. Bear in mind that it is the first time the car has been driven in anger in three weeks and it was getting quicker as the afternoon wore on. I'll try and do the timings again with fields 11 and 20. I do however still have a N145 sensor code error on VCDS (open / non communication) so may have to replace the right engine mount solenoid at some stage although it is not throwing an EML / EPC light.

Your air flow could be down due to not having the valves clean. I looked at one of my older logs and it had 156. I can't remember if that was one when the carbon was really bad though. It would be good to see the logs side by side and see if the percentage difference was across the board or only toward the top end revs. If it's across the board I wouldn't worry about it. If it's top end maybe get a clean and try again (if you are worried)?

Other than that, see if you can log timing correction. That's a good indicator too. Keep air temp in the logs this is an important value to see.