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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?
Marti,
It's only 9 degrees- a mere trifle!
You could try putting ever more advance in to offset the error factor but the trouble is you have already added in some of that with the advance you dialled in with ST2. I did comment earlier how I was somewhat surprised at the amount you were piling in mid range- maybe you could try a simple experiment by adding across the board timing in 3 degree increments to see what happens. If you do set the knock increment to 1 degree to hep resolution during testing for knock.Alternatively it may be better to load the stock timing map and add the missing 10 degrees across the board to give you a benchmark and then onwards and upwards but it can only be a temporary thing as once they start slipping presumably there is no end to it.
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...
Ok, I think I am following now, this is the timing ring on the flywheel which the crank position sensor is reading
This is telling the ECUs when to fire fuel and spark, so this would explain why I could advance my map so far forward.
What thoughts on how this would affect hp?
I have a spare flywheel from my old engine which I could use however I would want to check that it is ok, I will use the thread referenced to try and check alignment
Ok, I think I am following now, this is the timing ring on the flywheel which the crank position sensor is reading
This is telling the ECUs when to fire fuel and spark, so this would explain why I could advance my map so far forward.
What thoughts on how this would affect hp?
I have a spare flywheel from my old engine which I could use however I would want to check that it is ok, I will use the thread referenced to try and check alignment
Any idea on how these things slip?
Correct, timing ring for the crank position sensor (CPS). Fuel timing is not important but ignition timing is critical. And yes, if you add ten degrees advance to all of the maps (idle, cruise, etc) then you can compensate for the timing ring being ten degrees late. If you don't compensate (or fix the timing ring) then it is a pretty big hit on power, but I don't know if that would explain the dyno results. The best option is to fix the timing ring and then see what issues remain.
I have no idea how they move, but they do. Just part of the rich and exotic nature of these cars.
I dropped the flywheel cover and compared my spare flywheel to the flywheel on the car and the ring gear is in an identical position. To much of a coincidence I thought, so I re-checked the timing with a different strobe gun and found the timing of the crank to be fine.
I am putting the first check down to some setting or issue with the first strobe. So this eliminates the timing as being an issue.
That leaves me back at swapping the manifold back to a stock manifold, hopefully by Monday if the weather plays ball
I dropped the flywheel cover and compared my spare flywheel to the flywheel on the car and the ring gear is in an identical position. To much of a coincidence I thought, so I re-checked the timing with a different strobe gun and found the timing of the crank to be fine.
I am putting the first check down to some setting or issue with the first strobe. So this eliminates the timing as being an issue.
That leaves me back at swapping the manifold back to a stock manifold, hopefully by Monday if the weather plays ball
Is it easy/cheap for you to dyno the car? If it is, why not go in and fill the tank with the highest octane race fuel (with boosters if necessary). Then see how much power it makes at the knock-unconstrained optimum spark timing? You could do this with your currently installed intake and again with the new stock intake. The results would tell you a lot about the intake modifications, for sure. If dynoing is expensive for you, then I understand you may not want to do that.
Is it easy/cheap for you to dyno the car? If it is, why not go in and fill the tank with the highest octane race fuel (with boosters if necessary). Then see how much power it makes at the knock-unconstrained optimum spark timing? You could do this with your currently installed intake and again with the new stock intake. The results would tell you a lot about the intake modifications, for sure. If dynoing is expensive for you, then I understand you may not want to do that.
+1
I'd also pick a different shop just to rule out something wonky with this dyno since you have no before runs.
I'm not very familiar with the geography of your area, but this place is listed as having a 2wd Dynojet chassis dyno, and only 20 miles from the shop you went to: http://www.sitechracing.co.uk/
Once nice feature with Dynojets is you can download their software and load the dyno runs yourself. I cannot find the Maha software anywhere, maybe ask your shop about that??
I have switched back to a completely standard inlet manifold which has made no difference as far as I can tell to the power output.
Here is a picture of the timing of both cams at TDC. It is zero on 5-8 and - 2 on 1-4
The timing ring was checked and is fine. Compression looks fine across the cylinders. There is a slight difference in colour on the plugs between banks, 1-4 look to be better colour (small white deposits/cleaner) than 5-8 which look a bit dirtier. I thought I might find something on the timing or ignition circuit on 5-8 that might have tied into this but it all looks ok. There is also sometimes something that feels like a slight stumble while the engine is running which I put down to the cams being bigger.
In line with what I can hear the ST also shows the idle being affected at the same time however this might just be a condition of running bigger cams.
Earth points in the v were all cleaned up and I have a new earth cable to the engine fitted which I did at the same time as the battery earth replacement. The rotor arm and cap look fine so the only thing left would be the coil and connection to the coil which are very unlikely although I could try swapping sides to see if it makes any difference.
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)
Is the compression ratio standard, and whet were your test readings ?
Can you guys take Marti’s logs and estimate the amount of air his engine is ingesting and compare that to a stock engine?
The engine is either nor getting enough air, is not burning it with fuel efficiently, or losing it in frictions.
Knowing how my air the engine ingests would allow one to speculate on underlying causes of low power output. Too long exhaust camshaft duration would mostly show up as the engine not ingesting much air, for example.
Another thought is that if this would be my car, I’d take a little risk on a dyno trying to understand what’s going on. I’d run it at least to 7000 rpm, set the knock retard to minimum, and give it as much ignition advance as it wants in terms of making more power. If it’s the exhaust cam being too long duration for the usual rpm range, it should carry the torque at those levels to 7000 rpm and take much more ignition advance at mid range rpms than a completely stock S4 engine.
Can you guys take Marti’s logs and estimate the amount of air his engine is ingesting and compare that to a stock engine?
The engine is either nor getting enough air, is not burning it with fuel efficiently, or losing it in frictions.
Knowing how my air the engine ingests would allow one to speculate on underlying causes of low power output. Too long exhaust camshaft duration would mostly show up as the engine not ingesting much air, for example.
This would be great.
Here is a theoretical question, if we were to assume that perhaps the exhaust cam was a little too much for the slightly lower compression S4 engine in comparison to a GT (seems like a lot of HP to drop for the small difference) would it still be right to change your it if the intake flow was going to be greatly improved?
I ask as I am getting close to fitting my prototype manifold and was wondering on whether this might negate any cam profile thoughts
05-22-2019, 11:37 AM
