Jump to content
SAU Community

Recommended Posts

Gentlemen,

I present for you a mystery.  The short version is;

  • The tank of Shell 98 that I used last week, pretty much right from the beginning of the tank, until I filled it back up on Wednesday, ran really high EGT and in a really odd way.  About 450km of this behaviour.
  • I have EGT probe installed through a hole in the top of the turbine housing.  Has been there for years.  I'm very familiar with what sort of EGTs the car makes.  It will settle to <400°C at idle.  It will run at ~500-600°C just driving around.  It will run >800°C when stomping it hard or driving it fastish up a steep hill.  All normal.  When it has had a problem in the past (like a bad batch of fuel I had once that caused it to detonate), the temperatures would go spastically high under load, as you'd expect when it's detonating.
  • Last week, it would run up to 900-1000°C at odd times.  Sitting at the lights it would continually climb until it got up there.  Driving around it would do it.  Stomp on it a bit and it would sometimes stay high, sometimes it would settle back to the ~600-700°C territory you might expect.  It would also sometimes run normal EGT and sometimes idle down to the <400°C I like to shut it down at.  Other times after pulling up to park it, the EGT would just continue to rise through 800°C.
  • I must stress that I did not hear it ping at all.  It also felt very normal.  It drove the same, it idled at 600rpm, it was just as fast.  It wasn't as if it was running a blocked injector and missing some of its fuel, etc etc.
  • As soon as I put 50+ litres of fresh fuel in it, the car went 100% back to normal.

So, theories on what would cause it to happen on a single tank of fuel?  What could possibly be wrong with the fuel that would make the car seem normal in all other respects but run such high and odd EGTs?

Back story on the fuel.  I pretty much only use Shell 98, in Adelaide.  Occasionally it gets BP98, but I can tell there is a tiny difference in how well it runs, so choose Shell.  I use a number of Shell stations and maybe 10-20% of the time I use the one at Golden Grove.  This tankful came from GG.  The replacement tankful came from the Shell on Churchill Rd.  I have occasionally been suspicious of the operation of the engine after fills at GG.  Some fluffiness at idle, maybe some pinging (in fact, I think the tank that caused it to ping like a meth addict last year came from there).  That sort of stuff.  But only vague suspicions, nothing quite as convincing as last week.  Has anyone else had a weird result from there, or any other servo in particular?

Link to comment
https://www.sau.com.au/forums/topic/472965-high-egt-mystery/
Share on other sites

Yuh, well, my initial thought was low octane.  But it didn't ping at all.  I've seen what happens when it gets a dose of fuel that is clearly not high enough octane.  It pings like crazy on load.  This lot didn't.  And the car should fairly happily run 91 at idle and low load, but in this case would get really hot out the exhaust.  Makes sense, it does not.

Was it a hot day? Does your car have a Nistune and or some form of idle management strategy that retards timing to keep the idle at its set point?

I put in a Nistune into a S13 last week and because his idle screw is cooked the idle was quite high however would settle after 10 seconds or so.

Went to check timing and guess what? Was idling at 4 degrees... I thought something was not right but had a feeling the ECU was pulling timing on idle and yep it was. Changed the TPS voltage threshold and boom, base timing back to 15 degree.

Hi Johnny,

The answers to your questions are yes and yes.  However, it wasn't always hot weather.  Air temps on the road varied from well below 30 to nearly 40 last week.  The normal idle control works very well to keep the idle at 600 since I cleaned and properly adjusted the valve some (long) time ago.  In fact it was the previous occurrence of fuel related weirdness that prompted me to check the operation of the IAC when I found it idling at 5° back then.  I didn't get a chance to put the laptop onto the car while it was doing it because I was invariably too rushed to do it.  Kind of wish I had though, to be sure.

 

  • Like 1

Maybe bad batch, another reason I always tell people to run BP Ultimate and nothing else. I'm sure other tuners would say the same as well.

Wonder of the batch was overloaded with detergents and addictive which could be causing it

A quite relevant detail which seems missing here unless I missed it - what were AFRS doing?  Tracking as normal? 

Did you ever stop and check the exhaust manifold by eye to see if it was glowing like could be expected under those conditions?

I would have needed the laptop hooked up to see any AFR info.  I don't have a wideband and my cute little 0-1v meter hasn't been hooked up since I had to replace the O2 sensor.  Times like these I wish I wasn't so lazy!

I did stop and pop the bonnet once when I was driving at ~80km/h (which is not really a high load) with 800°C indicated but nothing was glowing, nor did the amount of heat near the exhaust feel outrageous.  I looked under there a couple of times when I pulled up at home with high temps at idle, with same non-result.  I can imagine hot gas inside the manifold/turbine/dump not having enough mass flow to heat the metal bits up enough to make them glow if it's only at idle/cruise loads, so this probably isn't really useful data anyway.  I would probably have needed to put it on the dyno - give it some moderate load and both see the manifold and watch the AFRs.

If this bullshit behaviour had continued onto the next tank of fuel I would have gone out of my way to do that.  Because then it would have been clear that the car had something odd going on.  But the instant change on the fresh tank made it dead clear that it was the fuel.

Yuh, me too, except substitute Shell for Mobil, because that's what works better here.  You have to keep in mind that different cities get the various branded fuels from different sources.  Many are the same, but they're not all.

I might have to do a number of tanks of BP or Mobil to see how it goes.  It's been some time since I switched to near 100% Shell.

It's been a while since I've done back to back testing. About 10 years ago, I did a long coast drive in my R31, home to a rented holiday house (end of year uni gathering) + home. 1 full tank of Caltex 91, 1 full tank of Shell. Got 50 km extra from Shell. The dirty30 also liked the Shell better, but ran best with Mobil 91/95 (back when Mobil stations were still around). Bonus was the Mobil was closest to my old house haha. I found that BP ran well but didn't do as well mileage wise, Caltex was consistently the "worst" but there wasn't much difference. Once Caltex dropped regular 91, I avoided it like a plague (E10 stalled my R31 during cold starts).

But yeah, 100% agree it varies between stations and varies between tanks (the underground tanks under the servos). A friend of mine full-tanked her old Cruze with 7 Eleven 95RON (different servo from my local), there was water in the petrol and it stalled her car. 7 Eleven paid for the mechanic's costs though (why I always get a receipt if I fill up elsewhere).

Although, these days, my boat/best gen Liberty doesn't care what it drinks, as long as it's 95RON or better.

Sounds stupid but my car doesn’t like the fuel from shell at GG much at all

I’ve always put it down to fuel quality, particularly storage. It’s a old servo, with old tanks. It’s in a odd spot too, so I don’t think they have the fuel turnover of some others in the area

I’m finding the Mogas on golden grove road pretty good, the tanks there are only a few years old and there’s always cars buying 98 there

The other option is the liberty at sunnybrook with there premium 100 blend with a dash of ethanol

  • 1 month later...
On 1/2/2018 at 4:25 PM, Guilt-Toy said:

try another egt sensor and gauge.

 

On 1/2/2018 at 5:05 PM, GTSBoy said:

I think you miss the point.  EGT was weird for 1 tank of fuel.  Then back to normal.

 

On 1/5/2018 at 8:03 AM, GTSBoy said:

It seems as though one confirmation of GG's oddness will do.  I shall blacklist them immediately (backdated to 2 weeks ago).

 

OK, so a month later (but only 1.5 tanks of fuel later, because I've been overseas half the time).....and it appears as if it is not dodgy fuel.  I haven't put Shell in since then.  Just 2 fills with BP98.  First one was normal operation.  The most recent tank, the EGTs have been high again.  But, properly intermittently.

I finally got the shits up enough with it to put the laptop on it while it was playing up.  Timing was exactly as commanded by the map, so not retarded.  Fuelling looked fine (pulse widths were as expected, narrow band was flicking back and forth from 0-1v as normal). 

Got the shits up even more and took the IR pyrometer along for a drive.  Drove up a big hill and parked it with the EGT indicating 800°C idling.  Turbo flange was only 400°C. which is exactly the sort of temperature I'd expect it to be based on old normal operation where the EGT would sit on about 550°C after that drive.

Suspicion is now nearly 100% on a dodgy EGT probe, or more likely, gauge.

  • Like 2

I figured the CJ compensation is #1 suspect, but given that these things are little microprocessors with an analogue input and stepper motor driver etc etc, I figured that a whole lot of things could go wrong inside them.

These are the relatively cheap Taiwanese made (but decent brand) stepper motor style things that, in my case, had some of the illumination LEDs inside die after only a short period of use, forcing me to choose the other colour LEDS to use.  Lucky none of that colour have died.  Short version, they are built down to a price.  They have been surprisingly accurate for that though, up until this misbehaviour.

Edited by GTSBoy

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • See if you can thermal epoxy a heatsink or two onto it?
    • The other problem was one of those "oh shit we are going to die moments". Basically the high spec Q50s have a full electric steering rack, and the povo ones had a regular hydraulic rack with an electric pump.  So couple of laps into session 5 as I came into turn 2 (big run off now, happily), the dash turned into a christmas tree and the steering became super heavy and I went well off. I assumed it was a tyre failure so limped to the pits, but everything was OK. But....the master warning light was still on so I checked the DTCs and saw – C13E6 “Heat Protection”. Yes, that bloody steering rack computer sitting where the oil cooler should be has its own sensors and error logic, and decided I was using the steering wheel too much. I really appreciated the helpful information in the manual (my bold) POSSIBLE CAUSE • Continuing the overloading steering (Sports driving in the circuit etc,) “DATA MONITOR” >> “C/M TEMPERATURE”. The rise of steering force motor internal temperature caused the protection function to operate. This is not a system malfunction. INSPECTION END So, basically the electric motor in the steering rack got to 150c, and it decided to shut down without warning for my safety. Didn't feel safe. Short term I'll see if I can duct some air to that motor (the engine bay is sealed pretty tight). Long term, depending on how often this happens, I'll look into swapping the povo spec electric/hydraulic rack in. While the rack should be fine the power supply to the pump will be a pain and might be best to deal with it when I add a PDM.
    • And finally, 2 problems I really need to sort.  Firstly as Matt said the auto trans is not happy as it gets hot - I couldn't log the temps but the gauge showed 90o. On the first day I took it out back in Feb, because the coolant was getting hot I never got to any auto trans issues; but on this day by late session 3 and then really clearly in 4 and 5 as it got hotter it just would not shift up. You can hear the issue really clearly at 12:55 and 16:20 on the vid. So the good news is, literally this week Ecutek finally released tuning for the jatco 7 speed. I'll have a chat to Racebox and see what they can do electrically to keep it cooler and to get the gears, if anything. That will likely take some R&D and can only really happen on track as it never gets even warm with road use. I've also picked up some eye wateringly expensive Redline D6 ATF to try, it had the highest viscosity I could find at 100o so we will see if that helps (just waiting for some oil pan gaskets so I can change it properly). If neither of those work I need to remove the coolant/trans interwarmer and the radiator cooler and go to an external cooler....somewhere.....(goodbye washer reservoir?), and if that fails give up on this mad idea and wait for Nissan to release the manual 400R
    • So, what else.... Power. I don't know what it is making because I haven't done a post tune dyno run yet; I will when I get a chance. It was 240rwkw dead stock. Conclusion from the day....it does not need a single kw more until I sort some other stuff. It comes on so hard that I could hear the twin N1 turbos on the R32 crying, and I just can't use what it has around a tight track with the current setup. Brakes. They are perfect. Hit them hard all day and they never felt like having an issue; you can see in the video we were making ground on much lighter cars on better tyres under brakes. They are standard (red sport) calipers, standard size discs in DBA5000 2 piece, Winmax pads and Motul RBF600 fluid, all from Matty at Racebrakes Sydney. Keeping in mind the car is more powerful than my R32 and weighs 1780, he clearly knows his shit. Suspension. This is one of the first areas I need to change. It has electronically controlled dampers from factory, but everything is just way too soft for track work even on the hardest setting (it is nice when hustling on country roads though). In particular it rolls into oversteer mid corner and pitches too much under hard braking so it becomes unstable eg in the turn 1 kink I need to brake early, turn through the kink then brake again so I don't pirouette like an AE86. I need to get some decent shocks with matched springs and sway bars ASAP, even if it is just a v1 setup until I work out a proper race/rally setup later. Tyres. I am running Yoko A052 in 235/45/18 all round, because that was what I could get in approximately the right height on wheels I had in the shed (Rays/Nismo 18x8 off the old Leaf actually!). As track tyres they are pretty poor; I note GTSBoy recently posted a porker comparo video including them where they were about the same as AD09.....that is nothing like a top line track tyre. I'll start getting that sorted but realistically I should get proper sized wheels first (likely 9.5 +38 front and 11 +55 at the rear, so a custom order, and I can't rotate them like the R32), then work out what the best tyre option is. BTW on that, Targa Tas had gone to road tyres instead of semi slicks now so that is a whole other world of choices to sort. Diff. This is the other thing that urgently needs to be addressed. It left massive 1s out of the fish hook all day, even when I was trying not too (you can also hear it reving on the video, and see the RPM rising too fast compared to speed in the data). It has an open diff that Infiniti optimistically called a B-LSD for "Brake Limited Slip Diff". It does good straight line standing start 11s but it is woeful on the track. Nismo seem to make a 2 way for it.
    • Also, I logged some data from the ECU for each session (mostly oil pressures and various temps, but also speed, revs etc, can't believe I forgot accelerator position). The Ecutek data loads nicely to datazap, I got good data from sessions 2, 3 and 4: https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-2?log=0&data=7 https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-3?log=0&data=6 https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-4?log=0&data=6 Each session is cut into 3 files but loaded together, you can change between them in the top left. As the test sessions are mostly about the car, not me, I basically start by checking the oil pressure (good, or at least consistent all day). These have an electrically controlled oil pump which targets 25psi(!) at low load and 50 at high. I'm running a much thicker oil than recommended by nissan (they said 0w20, I'm running 10w40) so its a little higher. The main thing is that it doesn't drop too far, eg in the long left hand fish hook, or under brakes so I know I'm not getting oil surge. Good start. Then Oil and Coolant temp, plus intercooler and intake temps, like this: Keeping in mind ambient was about 5o at session 2, I'd say the oil temp is good. The coolant temp as OK but a big worry for hot days (it was getting to 110 back in Feb when it was 35o) so I need to keep addressing that. The water to air intercooler is working totally backwards where we get 5o air in the intake, squish/warm it in the turbos (unknown temp) then run it through the intercoolers which are say 65o max in this case, then the result is 20o air into the engine......the day was too atypical to draw a conclusion on that I think, in the united states of freedom they do a lot of upsizing the intercooler and heat exchanger cores to get those temps down but they were OK this time. The other interesting (but not concerning) part for me was the turbo speed vs boost graph: I circled an example from the main straight. With the tune boost peaks at around 18psi but it deliberately drops to about 14psi at redline because the turbos are tiny - they choke at high revs and just create more heat than power if you run them hard all the way. But you can also see the turbo speed at the same time; it raises from about 180,000rpm to 210,000rpm which the boost falls....imagine the turbine speed if they held 18psi to redline. The wastegates are electrically controlled so there is a heap of logic about boost target, actual boost, delta etc etc but it all seems to work well
×
×
  • Create New...