Obviously, the context is and was the torque holding up with rpms. If the torque holds up with rpm, you don't have simply a restrictive exhaust system after the cross-over. I thought pointing that out might have saved some time, effort, and energy by allowing you to look for the problem where it might conceivably be, instead of looking for it where it clearly isn't. But no.

 

Slightly modified version of the stock intake, I will be going back to completely stock in the next week to eliminate that element

 

Might have saved my some time, I thought the change of system would be a lot quicker but had to wait for exhaust boxes being delivered.

 

This morning I performed a warm compression test and this time cranked the engine for longer and checked the gauge to ensure I got the full reading for check cylinder. These were the results (in PSI)

1 - 175
2 - 167
3 - 173
4 - 170
5 - 168
6 - 170
7 - 168
8 - 169

These are a little lower than when I tested the a standard S4 engine with this gauge which recorded somewhere around 180 - 190 psi

 

Hi Fred

You are going to have to remind me what the timing ring is, before I can check it - would this be the ring that the rotor arm screws into?

 

If you install camshafts with more duration the compression reading will always be lower.
Åke

 

Marti,

The timing ring is an interference fit on the crankshaft and if the index point for the crank position sensor. Despite the interference fit, such items have been known to slip on the crankshaft and thus the introduce timing error in the ignition system that is then firing correctly relative to an incorrect reference point. Such instances are quite rare but i have read about them having taken place albeit not every week or anything like it. Given you have ST2 and thus can see what part of the idle map the car is running at you know what advance it thinks it wants and a timing light should indicate the same value. If the timing ring slips and the advance is supposed to be 15 degrees but it shows 5 degrees you would then know that all your timing is out by the same margin.

I liked Colin's suggestion simply because he suggested it and the fact that you seemed to be able to add in quite a lot of advance that might suggest some retarding influence but of course something else could be going on whatever it may be.

I presume you have checked the traffic light indicators in the ST2 ignition parameters page that show healthy knock sensors and Hall trigger with a green traffic light ?

 

Thanks Fred, would the procedure be a timing light on no.1 cylinder pointed at the TDC indicator on the crank reading what is indicated off the crank vs the value the ST is indicating?

Re the ST traffic lights, they are all green and hall sensor is very recent (1 yr) and knock sensors are recentish about 3 years but low mileage and in good condition.

 

So this would be consistent with the readings I am getting

 

As far as I know that is correct. Statistically speaking it is highly unlikely to be this but when something strange is going on the more you can safely eliminate the closer you get to solving the issue.

For sure spark retardation kills power- we all know that - it is a given [unless the engine is over advanced to start with and that is most unlikely].

 

Yeah it’s just the IVC moving later and reducing the cranking compression.

I think that this is also one of the reasons why one should increase the geometric compression ratio when installing bigger cams.

 

That'll be potentially informative. Any problems that may be coming from the too-long exhaust cam are magnified by a restrictive intake. If the intake modifications went backwards, then that test would show an improvement.

A higher-priority debugging item would be to figure out if the actual timing in the engine matches what Sharktuner thinks the engine is getting. Suggested by many here. It could be that engine can tolerate high ST2 advance settings without knocking because there's a problem with ignition timing or because cylinder filling is poor.

Another thing to figure out is if the engine is running on all cylinders the same way, that is, getting the fuel and spark the same way.

 

Thanks, priority no.1 will be the check on timing. This engine did have new belts and water pump fitted just before it was installed (not by me) so I guess there is a risk of it being out.

 

Just back in from checking the engine timing vs what the ST thinks is the timing and these are the results

ST at idle thinks it is roughly putting in 10 degrees advance and when I am looking at the crank indicator with the strobe it is indicating just after 0 degrees, maybe 1-2 degrees - it is moving slightly.

So I am guessing the this means a discrepancy with the timing plate as the two don't correspond with each other?

 

Yes, timing ring has slipped. This is an auto, right? If so the timing ring is a separate piece, interference-fit as noted and can slip. (For stock single-disc clutches the timing teeth are integral with the flywheel).

All you gotta do is pull the flywheel, tap the timing ring off, heat the ring and chill the flywheel then put it back on correctly. Then tack it in a few spots so it stays put. It would be best to make a jig to get it oriented correctly, there is a drawing here somewhere...

Edit: This thread explains all: https://rennlist.com/forums/928-foru...-flywheel.html