 | Home > Tdi > 300tdi EGT temp increase post new Gear & Transfer Box? |
 
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| MarkBrown Member Since: 03 Oct 2022 Location: Mid Wales Posts: 475   
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I don't know anything about egts, but now with a 1.2 box your TDI will be working harder as each of the high range ratios is now higher. More load on the engine will mean more heat. I'm going to swap my 1.2 back to a 1.4 and I'm running a 300hp Merc engine. It will pull the ratio ok, but it's only beneficial on motorways where a higher speed can be utilized.
My 1.2 in my TDI was hopeless, too high, so I swapped back to the 1.4, which was much better. I'm sorry it's probably not what you want to hear. |
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26th Aug 2023 1:28pm |
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| ickle Member Since: 22 Jul 2010 Location: South Vendee Posts: 1786  
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1.2 in my mildly tuned 200tdi running 265 tyres was fantastic
Good economy, towed 3.5t easily, performed well, 85 on motorways no problem (with earplugs!) Perhaps you had / have another fault Hth keith |
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26th Aug 2023 1:41pm |
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| MattH268 Member Since: 01 Dec 2021 Location: Moray Posts: 66  
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The primary reason for the change of ratio was that I spend a huge amount of time in 5th with my mildly tuned 300tdi (boost pin, full size intercooler) and it always seemed like I needed a 6th gear. I don't tow or off road much, the vehicle is used primarily to tour the Highlands & Islands which it's great at. It doesn't sound like it's working at all hard to justify the heat. Maybe that's the deceptive part, the engine is working harder but it's not complaining as much so maybe more heat is generated instead of noise. That's the biggest difference so far, 2 weeks & 400miles since the swap is that it's so much quieter in the cab and I'm back to changing gear more often which I don't mind at all. 300tdi 90 CSW
2.2tdci 110 HCPU 1972 Series 3 88" Truck Cab |
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26th Aug 2023 2:43pm |
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| geobloke Member Since: 06 Nov 2012 Location: Nottinghamshire Posts: 4410
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As above. Went to the 1:1.2 (110 TD5 though) and also noticed that the EGTs went up due to the higher gearing. Actually hated the 1.2 box as 30mph just seemed to be between 3rd and 4th gear. When the intermediate shaft began to leak I replaced it with the standard 1:1.4 defender box and an over drive which is hands down the best of both worlds. It is worth noting that when the overdrive is engaged the EGTs do not take long to rise when driving even minor inclines. Here in Wales the 1:1.4 rules the road as you rarely get to 60mph, especially at this touristy time of year  |
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26th Aug 2023 6:27pm |
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| Will@LRW Member Since: 04 May 2019 Location: UK Posts: 183 
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My EGT sits in the 300 range and goes above 400 on hills; above 500 on the longest motorway hills. Also have a 1.2 box but a standard 300Tdi on 200k. Fitted the gauge after the box so don't have any before figures to compare to. I suspect your mods are the reason. LR Workshop
Find a Defender's history and spec: https://defender.lrworkshop.com |
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27th Aug 2023 8:33am |
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| MattH268 Member Since: 01 Dec 2021 Location: Moray Posts: 66
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Have to say I like the reduced engine tone and 3rd 4th is perfect for me trundling on narrow single track lumpy roads locally. The test will be up over the Lecht in a couple of weeks' time and to see if I can stay below 600! My gauge had started to flicker before the box change, nothing obvious loose so suspected LED failure with what is a relatively cheap Fourby screen that's 3 years old now. I fitted the EGT when I had my AlliSport intercooler, steg supplies boost pin & dynamic advance spacer kit fitted to monitor the exhaust temp on a 165k engine. 300tdi 90 CSW
2.2tdci 110 HCPU 1972 Series 3 88" Truck Cab |
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27th Aug 2023 10:42am |
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| I Like Old Skool Member Since: 23 Feb 2015 Location: Manchester Posts: 814 
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I read an article on EGT sensors and values a few years ago when considering an EGT sensor (never did fit one as I'm running completely stock). The one snippet of info that stuck with me was that exhaust gas temp would rise with the engine working hard at low revs and, for instance, if climbing a long hill and seeing the EGT rise then a way to lower this would be to change down a gear so engine is revving faster but at a lower throttle.
This sort of fits with the rise in EGT you are seeing after changing the t/box ratio? |
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30th Aug 2023 8:29am |
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| MattH268 Member Since: 01 Dec 2021 Location: Moray Posts: 66
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I am definitely seeing a rise in EGT from the new transfer box during normal driving even if the engine doesn't sound as if it's working hard at all. Before the Transfer box change and on long climbs the best way to restrict the temp rise was to drop to 4th or 3rd, so exactly as you say. It was nice to see the reading just to confirm what you were hearing but as I drive by sound anyway you knew not to push it. I guess over the last 18 years of ownership the different sound it makes now combined with different readings is something to get used to and drive accordingly.
Many thanks for your reply. M 300tdi 90 CSW 2.2tdci 110 HCPU 1972 Series 3 88" Truck Cab |
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30th Aug 2023 9:45am |
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| Chicken Drumstick Member Since: 17 Aug 2020 Location: Near MK Posts: 751
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Its the load on the engine, not the revs.
What size and type of tyres are you running? And I'm guessing the Tdi is tweaked. The tall gearing means you have to have the throttle open further, so more fuel and more load and more heat. You either need to back off and go slower, i.e. the same load you'd have been before or drop a gear. If the EGTs are too high for you liking and you don't want to drive different or revert the gearing. The only other option will be to detune the engine. |
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30th Aug 2023 12:56pm |
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| MattH268 Member Since: 01 Dec 2021 Location: Moray Posts: 66
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265-75 16 BF Goodrich AT on steel modulars which have been the same wheels & tyres for the last few years. The vehicle was fully restored 3.5 years ago, and I made a couple of alterations to the engine then that have made a difference to its driveability and keeping up with traffic. The reason for the recent change was that the gearbox needed replacing and as 5th had worn out due to me being there most of the time, I thought 1.2 would be beneficial.
I am driving differently, as you need to. 4th now is like the previous 5th. It is still early days, so it does need for me to get used to it. The 90 isn't my daily driver but it will be used more in the coming weeks exploring. My surprise was the extra heat at lower speeds with the indication the engine was working harder to go slower, yet sounding super quiet, as if it was merely doing its thing without a care in the world. Anywhere near 55mph is high 400s low 500s regardless of terrain and I back off anytime it creeps into the mid 500's. I always had kept an eye on the gauge previously but when initially I saw 625, backed off immediately, on a hill 500 was only possible into a headwind I pay more attention to it. Thank you for the replies. M 300tdi 90 CSW 2.2tdci 110 HCPU 1972 Series 3 88" Truck Cab |
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4th Sep 2023 9:51am |
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| jocklandjohn Member Since: 16 Sep 2016 Location: Highlands Posts: 62  
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I read a long and interesting (USA) article on 'driving by EGT' which basically involved watching your exhaust in the wing mirror and changing down when you saw black smoke. (Exactly what Old Skool notes in his reply.)
The author eloquently made the point that although your revs may *seem* higher than might be necessary, rather than chuck unburnt fuel out the back as black smoke in a higher gear you'll use the fuel to go forwards and your EGT's will be much lower. Author was able to extract maximum mpg (& perfomance) from his diesel by canny use of the EGT and adjusting his driving/gear selection accordingly. I've been chasing a poor running problem for ages (may. have now resolved it) but the symptoms were as you describe, and the cause as Chicken has noted - is probably over-fueling or an incorrect fuel/air mix. The change in your gearing is probably the cause, pulling too high a gear compared to your previous gearing setup. |
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10th Sep 2023 8:55am |
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| MattH268 Member Since: 01 Dec 2021 Location: Moray Posts: 66
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Just an update, I've now done a good few miles, fitted a new gauge that no longer flickers, and adjusting my driving to suit the new gear ratio's I can easily keep things below 500. I peaked at 525 in 3rd going up over the Lecht but can easily float around 300-350-400 without issue. Unfortunately, I do need the take the vehicle back to the garage that did the work to sort out the new Ashcroft gearbox as when cold 2nd doesn't exist and 5th to 4th needs a double declutch or pause in neutral before there is an audible click then 4th can be found. Not ideal as it's getting worse not better.
M 300tdi 90 CSW 2.2tdci 110 HCPU 1972 Series 3 88" Truck Cab |
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24th Sep 2023 12:01pm |
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| L110CDL Member Since: 31 Oct 2015 Location: Devon Posts: 10782 
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Glad you've sorted out the EGT issue, only to have another one present itself
Your lucky that you had time to use your gearbox before this issue showed itself, not like mine 1996 Golf Blue 300Tdi 110 Pick up.
Keeper. Clayton. |
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25th Sep 2023 8:06pm |
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| MattH268 Member Since: 01 Dec 2021 Location: Moray Posts: 66
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Second update, the new gearbox is now sorted (some sealer removed & a different oil used (MTF94 to TRIPLE QX ATF Dexron III) but I also had the boost pin & dynamic spacer kit removed. Now back to the original settings the EGT is now reading in the 200s-300s under normal driving - 400 if hilly at speed and 500 only if deliberately trying too, so way better.
The air mix was fine but clearly my issue was overfueling as had been suggested. L110CDL I hope you manged to sort your Gearbox. M 300tdi 90 CSW 2.2tdci 110 HCPU 1972 Series 3 88" Truck Cab |
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24th Oct 2023 6:18pm |
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