Higher RPM/Boost Hesitation

[lotus23C]

I did a bit of research on all these fancy plugs for a VAG 1.8T and a 20v 4age. Seems common NGK BPR6ES are perfectly acceptable, way cheaper, and perform better as long as you change them every service interval. (about 10 000km). Iridiums are harder to fire than standard plugs as long as the standard plugs aren't too old.
Spark blows out more easily on multi electrode plugs. These fancy plugs are just designed to last 100 000km or the life time of your engine, its a compromise of longevity over performance. Possibly even a way of fleecing money out of people. I cannot imagine you are going to drive your lotus 100 000km in the next couple of years.
I pay the same money for 4 standard plugs as I do for one fancy plug.

[cammmy]

Thanks, the iridium plugs were the same price as the standard NGK's. I'm going to return the new NGK's that I ordered so I'll be left with a set of each type to compare.

[cammmy]

The plugs arrived quick! I'm, going to try and improve the VE table first, then change the coils and then the plugs last to try and isolate the issue.

[cammmy]

Hi All, dyno day on sat which was interesting. Good news and bad.

Good news, the car didn't explode and it seems everything I've done is working fine.

Bad news, looks like my IAT sensor is dying (giving a reading but it's not responding as expected) as well as my fuel pump. Running waste gate pressure we got to about 5,300rpm at .45 bar of boost before it started losing pressure.

On the positive side, the misfire seems to have been tuning (and IAT) related as suspected. The tuner re-did the table from scratch and we didn't run into that problem.

Another positive is that at the point it started to go lean we had 190hp at the hubs. The tuner reckons we'll see about 260-270 when we can get to full boost/RPM.

So between all of that, I think we've found the issue. Thanks for the help everyone, much appreciated.

I'll post back after the next session once I have a new fuel pump and IAT sensor. Might be a while though as Saturday sessions are booked for the next month or so.

Ta

[cammmy]

Unfortunately another partially successful dyno day. Hit the same issue with it going lean at high RPM. Gave it a full health check everywhere, It has full voltage to the coils, injectors and fuel pump at all RPM and has steady fuel pressure. Dyno guy suggested the injector drivers so we measured the current of one of the injectors; it starts to drop off at higher RPM suggesting thermal limiting. Went back to the specs of the MS Xtra board and the drivers are designed for sequential injection setups but are rated at 5 amp (we're drawing about 2.3 with 2 injectors per driver). Did some more digging and we found that they're 5 amp only at 25 celcius! They rapidly drop off after that before cutting completely at about 100 degrees, so I think we have the culprit. Going to re-jig it so the wire for each pair will split before the ECU and be connected to two drivers. That will half the load on each driver and allow them to run much cooler also. It doesn't help that they are only surface mounted to the PCB, there's no heat sink there.

Hopefully that will be it and tuning can be finished!

[whittlebeast]

Turn on your closed loop EGO correction. Toss in a new set of plugs and try again. My bet is you are too fat up top.

[cammmy]

EGO correction is on and the o2 is absolutely fine until it runs lean. It was initially running way rich but the tuner has dialled that in.

We can see in Tuner Studio that it's demanding more pulse width from the injectors as it goes lean but the current actually running through them is dropping by over 30% (as measured with a multi-meter). I'm pretty certain it's the thermal limiting in the injector drivers, especially after finding the product manual which contains a derating curve for current vs temp; it states that at about 90 degrees C it would no longer be able to supply enough power for two injectors.

[whittlebeast]

The last log I saw posted was reporting the EGO cor1 flat line at 100. The last MSQ I saw had EGO turned off and if simply turned on had settings in it that would switch Correction off under spirited driving.

Andy

[cammmy]

Yeah, those original logs are probably misleading now as they were pre-dyno. The tuner has redone everything from scratch, he can see the EGO correction in action when he's making a pull.

I'm going to try and amend the wiring this week. After that I'll I'll do some test drives and upload the new MSQ and logs.

Ta

[cammmy]

Hi All

Just thought I'd reply back as I think I've cracked it. I connected up each injector pair to two drivers but the issue was still there. I went back and improved the grounds this evening and presto! That seems to have cracked it.

I'm back at the dyno this sat so will post up the results.