User 52121

Alright... starting to put some miles on the car, the weather is turning (finally) and I'm starting to figure out what's what.

Car is a mild 2.5L (all stock and original bottom end), 50-trim T04E, 3" exhaust, and an M-Tune w/Rogue's injectors.

First few weeks of driving the car, the best term I can describe it's acceleration was "frantic." Especially in 2nd gear... it just RIPPED through it. Totally awesome. Car seemed to be a little on the rich side according to the logger (10.7-11.1 or so)... but I was more or less planning on leaving it there for extra safety margin (maybe lean it out just a tad, but not much).

It's been cool here in Chicago though - up until this week, the weather was consistently in the mid-50s Fahrenheit. We had a brief spurt of warm weather 2 weeks ago, and I noticed the car seemed WAY down on power. Weather usually sucks the life out of this thing but it was pretty bad. Before I could really investigate (was busy troubleshooting a bad ground on the alternator), the weather got cold again - and car was back to being a monster. All was well in the world.

This past week - it warmed up again - upper 80s F and high humidity. Driving around this weekend, I noticed that as it got warm outside, the car got really sluggish under WOT. Part-throttle car felt as great as it always did, just didn't want to make power at WOT.

Took a log and holy cow... AFR's down in the 9s. Certainly explains why the car feels like a turd.

Question is - why?

Nothing (NOTHING) mechanical has changed between the last cold day (FAST!) and this past weekend (SLOW!) other than the weather. I haven't even had the hood up!

I was hoping this was something I could just tune out (perhaps too much AIT compensation?) but looking at the numbers, something is amiss here. Curious to collect the thoughts from the peanut gallery.

Compared to the last cold day I took a log... boost is lower by ~1psi, intake temp is up 50 degrees, MAF volts are up 0.2v, injector duty cycle is up 10%, and AFR's are almost 2 points richer. On a crap air day with lower boost I'd have expected LESS MAF volts and less duty cycle.

All the boost hose connections are new/recent and OE Porsche. A quick glance over things this morning before I headed to work (took the truck) looked like everything was tight, connected and in order. 18" vacuum at idle. Guess I'll dig into it sometime this week and do a pressure test. :/ Just funny that it seems to be temp dependent. Thurs/Fri of this week are forecast again to be high 50s/low 60s so I'll probably hold off on doing any major futzing, and will do another log to see if it's repeatable (I'm pretty confident it is considering last Friday the car was a monster and it was cool outside).

Excel of the logs and the raw Rogue Tuner .xdl files attached for your viewing pleasure.

Anyways... thoughts? Any ideas behind what could be a hot weather only boost leak?

refresh951

I have not looked through the logs yet, I will tonight but are you monitoring knock? I assume pump fuel? Higher intake temperatures can lead to knock and the klr has some control here.

User 52121

Yes pump fuel, Mobil 93 octane. I don't currently have knock monitoring. Suppose I should probably toss a basic counter in there. Somewhat of a tuning "no-no" I know but with running known good fuel and keeping boost low, I haven't felt too concerned about knock. It's an unknown at this point so that could have something to do with it.

- however -

Spark advance between the two logs (cold and hot) shows the same advance for both. 24.5 degrees around 5800rpm. If the KLR retards spark, would I see the end result in the logs, or is the log showing "desired" advance vs. actual?

refresh951

Battery voltage is jumping around on the hot run, looks a bit strange.

User 52121

Seems to be related with load. Plot load, or MAP, next to vbatt and there is a solid correlation.

Unless the experts chime in with a different opinion, I'm willing to consider this "normal" since it was hot yesterday (and even hotter under the hood, with 25+ year old wiring...) I think that the voltage drops are a combination of underhood temps and engine load.

As I recall the route I took in my head, as I look at the full raw log, the voltage gets lower as I idle through my neighborhood. The first WOT romp is after driving at 30mph for a bit and sitting at a few lights. After I drove a bit at higher speeds (45-50) temps came down and voltage went back up.

On a hot day the voltage gauge reads quite a bit lower and seems to be drawn down more quickly as I sit around at lower speeds.

odb812

I think this is particularly interesting. Your duty cycle is a product of MAF volts and your AFR is a product of your duty cycle matching your actual air intake for the current state(other variables like rpm, etc). If your MAF voltage is not accurately representing the actual air intake, it would throw both of these values off. Looking at your logs, I'd say you have a boost leak somewhere. Boost is coming on at a slower rate(slope of the curve) and slightly later RPM. Also, you're AFRs in both hot and cold ambient air temp logs match until you start building boost, in which case the hot logs fatten up. You know how these cars can be and I think you're on the right track checking the intake system holds pressure first.

refresh951

Could it be an ignition miss at one or more of the cylinders? That would result in the rich condition and sluggish performance and explain why spark advance is the same between runs.

User 52121

Hmmm - awesome catch, I didn't notice that. I'll have to dig through the full log and look at that. Certainly supports the "boost leak" conclusion. Thanks for giving me something else to look at!

Refresh - misfire. Also entirely possible. The car seems to "surge" when it's driving like poop. No popping and farting or anything but the first hard pull when it's running poorly, it's not 100% super smooth. My original plan was to take a look at the plugs (they have ~20k on them, haven't checked them in a while) and inspect their general condition and gap before I remembered, "Duh I should hook up the logger...." I'll take a look at the plugs tonight and see if anything is funny looking.

User 52121

Ok on the train and looking at the data.

A quick XY scatter chart of WBO2 vs MAP shows its running fatter on the hot log. Across the board.

odb812

I guess there's no chance the FQS setting changed between the cold and hot logs? What type of FPR are you using? How long have the FPR and dampener been on the car? Do you have a fuel pressure gauge on the rail?

I'd suspect either somehow you're not metering the air properly or intake air is escaping somewhere between the MAF and intake valves; or you have more pressure on the fuel rail in the hot logs than the cold.

User 52121

Same FQS. Bosch 3 bar, 3 years old. Damper is ~4 years old.

Pulled the plugs, looking a little sooty, gonna swap them out. Will also take a look at fuel pressure tomorrow too.

rlm328

You should be making more power on cold days. Air is denser etc.

993GT

I want to say a post-turbo boost leak, turbo is attempting to compensate thus pulling more air through MAF(higher volts/over fueling) and reducing turbo efficiency(boost down, heat up-more than just ambient differences??)..

dizzyj

interesting to watch this. I'm about to pull the trigger on josh's tuner so i can datalog to help debug issues like these. unfortunately, I cant look at your charts and see a trend

andycowman

Hello

I don't know much about the ECU you are running, but mine (emerald K3) has a compensation table for air and coolant temps. These are applied to the main map and are what actually happens - do you have something like that causing it to add extra fuel in?