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Thread: Sams Polo 3.0

  1. #221
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    Alright cool. All done on that front then. Thx

  2. #222
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    So in the ongoing E20 tuning of my car I've found a few things.

    - The 98 RON petrol tune liked 0.82 lambda which was also described as on the safe side by the tuner. On E20 though it seems to prefer 0.80 sometimes tiping into 0.79's. eg It wouldn't handle 3.75 degrees of timing offset without up to 4.5 degrees of timing pull on lambda's matching the petrol tunes. But richening it up allows it to run that same advance with only a smidge of timing pull near 6000rpm.

    - its not worth trying to squeeze that last bit of timing into it anyway even though 1.5-3 degrees of timing pull is considered acceptable if not a target in the dub tuning community. I don't really get why that is. If I look at a 3.0 degree added log and it has 18.5 degrees of timing in there in the upper rev range, but the 3.75 degree log did have that until it was instantly yanked back to only 15 degrees for nearly 800 rpm, then I dont see how the latter is better. Also this tune is what I'll be using on the track for lap after lap of abuse so coming back from that threshold to a log devoid of any timing pull I think is the wiser move.

    - before I worked out that it wanted more fuel, it was pulling some timing around the torque/boost peak. It did this less so when I was running with the intake VVT activated. I thought that the VVT would enable better cylinder filling in this area and then as it was squeezed and banged that it would make for higher cylinder pressures than if there was no VVT. But the opposite has seemed to be the case. VVT 'on' between 2400 and 4250 seems less prone to torque peak knock - is that because the overlap it creates actually reduces the peak cylinder pressure?

    - When I started out with this I'm pretty sure I was getting spark blowout. Short of LS2 coil converting it all I could do was shrink the plug gap from 28 thou to 24 thou. This worked instantly and the spark blowout that could be heard/felt is gone. But it could still be there. When it was happening it wasnt visible in the misfire detection logs which are notoriously inaccurate for anything other than idle misfires or literally dead coil pack diagnosis.
    So the question is how can I look for spark blowout that might be too subtle to hear/feel? I assume spark blowout means no combustion takes place. The O2 sensor would see this as a sudden lean blip wouldnt it ie its only looking for oxygen content yeah, so a misfire will be seen as a whole lot of fresh air coming at it from 1 of the 4 cylinders right? Can spark blowout be seen in this way?
    I'm reading that iridium/platinum plugs might be the go for ethanol fuels as they have a stable spark position making them more appropriate for blowout issues. On the flip side I always thought that they were higher resistance compared to copper and its all about peak current flow right which is why I've used BKR7E's and just changed them at every oil change... thoughts?

    - oh and for the first time I've topped out the MAF on a few occasions. 194 g/s through a 2.5 inch stock MAF housing. Yes that was a cold dry night after a long cool cruise, but still its never gotten anywhere near that on a petrol tune with any K03 frame turbo before. Usually its hitting 185 g/s though, but thats kind of a moot point because this turbo is all about midrange anyway. So E20 blends work!
    Last edited by sambb; 22-08-2021 at 11:09 PM.

  3. #223
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    Lots of questions Sam, hope I don't miss any.

    I have seem lambda down to .75 work well, but that was on E25, so .79 on E20 isn't outrageous.

    As per previous posts, I have never used a gap below 0.7 mm (28/1000), so my suggestion would be a coil upgrade if you need to further reduce the plug gap. You are going to need it eventually anyway.

    In my experience more ethanol ALWAYS reduces knock, due to the cooling effect. There is a point where adding more no longer reduces the knock, which is where I stop.

    You are correct, more cam overlap reduces the combustion pressure and hence the knock. But as usual you don't get something for nothing, there is a torque loss, but you do get a bit more exhaust turbine efficiency. So as usual it's a trade off, if it's in an rpm range where you need instant response then more cam overlap isn't a bad thing.

    Spark blow out results in a sudden rich spike of unburnt fuel, ethanol does have an oxygen content so it's not as noticeably rich as with pump petrol.

    I have always used copper spark plugs for ethanol, at the end of the day copper is better conductor of electricity than iridium and platinum, which are really there to prolong the intervals between plug changes. I have never had an engine run better on iridium or platinum spark plugs.

    Topping out the MAF, now there is a good thing, more air = more power.

    You know my thoughts on ethanol, best thing I ever did was to change when leaded Avgas became unobtainable from Bankstown airport and unleaded race fuel was $7 a litre (~$500 a race weekend in fuel alone). We used to mix our own E85 about 15 years ago, and then started buying it around 2008 when the United servos stocked it.


    Cheers
    Gary
    Polo GTi 2017, Golf Mk7 110TSI Highline, Golf Mk7.5 R, Skyline R32GTST, Stagea RS4,

  4. #224
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    Alright I might look at getting it out to E25 and do a bit more testing. I'll be buried in LS2 coil conversions now too.

    Hmm surprised that a mis causes a lean condition at the O2 sensor. My thinking was that combustion consumes oxygen. If there's no combustion then oxygen levels in the virgin air remain high. I thought the sensor is not looking for unburnt fuel vapours, that it can't see them. No worries though, i'll take your word for it and now I know what to look for now so it'll be interseting to see if anything jumps out.
    appreciate the help Gary

  5. #225
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    Where is Sam?

    The only interesting ongoing thread on this forum and we have nearly 4 weeks of no posts.

    Hope that all is well in Gladys land.

  6. #226
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    I have a bit of news. The long awaited brake master cylinders have arrived from Germany. But given it's a bitch of a job to fit. Not sure it will be a quick fit to the car.

  7. #227
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    I'm still here. Like Gav said a possible solution to the overly long pedal has finally arrived. It will be a bitch of a job requiring a full flush/bleed with a system that is notoriously bad for trapped air in the ABS manifold. While I'm at it I'm going to do my rear beam bushes. The ones on the new car are two piece ones which aren't really seated correctly and look way to flexible when moved with a pinch bar. So I'll swap in my one piece solid bushes but that requires the rear brake lines being separated so that the rear beam can be dropped. Then while I'm at that, I may as well fit stainless braided rear brake lines. So yeah a master cyl job that needs a full flush, pressure bleed will drag into it a dropped and rebushed rear beam with new lines is quite a biggin and may be a while. Oh yeah and my master cylinder brace will then need to be remade because the master will sit further out. I'm not even sure it'll clear the channel that the fuel lines drop into. If the parts had arrived a few weeks back when the kids were still in home schooling and we were all stuck at home I would have gotten onto it but now it looks like things might open up and the kids are on hols right when the parts arrive which is a bugger.
    Yeah things just went quiet car wise when the ability to get onto a track disappeared or visiting mates and workshops etc . Then youtube, netflix and beer became a problem for me ha ha. Then I ended up on the wrong end of a company vaccine mandate and was nearly stood down. At least I have my job unlike a lot of people which I'm thankful for, but running that line where I thought I was going to loose it wasn't fun.
    Other than that I got back to some E20 blend tuning with UK Dave. I mucked around with plugs and now run some Brisk plugs. They are a silver (coated I assume) plug so slightly less resistance than copper maybe but have a really fine anode like an iridium/platinum. Tried them on a recommendation and despite the ethanol blend and way more timing I'm actually able to run a loose 29 thou gap which is bigger than the 28 thou I was running on peti. Better than the 24 thou I was down to to avoid misfires. Dave checked the dwell times on the stock coils and they were up there eg 2.8ms so there wasnt really anything to be had by pushing the coils harder. I didnt have the stomach to do a coil conversion so I'm glad that playing with plugs gave me a bit of a solution, but more testing needed. I'm glad Dave did offer to do a dedicated E20 tune for me. He was probably horrified that I had just previously upped the fuel pressure and added some global timing! It just keeps taking more and more timing now and is a bit leaner (0.83's) than I had it too. Same deal as before - no more peak power really due to turbo/cams, but the mid range is a proper step up from petrol.
    more to come, I've just been a bit preoccupied

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