300tdi Exhaust Gas Temperature

**owoodland** · 30th December 2006, 09:22 PM

So following the wisdom of the fuel pump tinkerers, I have fitted a thermocouple to the exhaust manifold of the tdi, namely by drilling a hole through the EGR blanking plate and welding the thermocouple holder onto it (a really ugly welding job too, my welder doesn't seem to want to drop back below about 100 amps and it just blows molten steel everywhere - that's a whole different story!)

So I've had a bit of an eye-off of the exhaust temperatures over the course of this afternoon and I have observed that:

-temp is usually 190-220 degrees when the motor is to operating temperature
-temp on cruise is about 290-330 degrees
-temp on acceleration is up towards 400 degrees
- temp on full boost accelerating up to 100 on the flat heads up to 500-550 degrees.

So question: how much is too much? The recommendation for checking the 'base case' EGT is to drive up a long hill in a high gear and max out the boost (which I will do, it's just that long hills are few and far between on the perth coastal plain).

Does anyone else have much experience with this?

Cheers

Owen.

**LRHybrid100** · 30th December 2006, 10:17 PM

Just about to do the same thing to my Tdi Rangie - I have am ETG to install before I put in the new BIG Intercooler and tweek the fuel.

So will watch this post with interest. I will also let you know what temps I get.

LRH

**LRHybrid100** · 30th December 2006, 10:21 PM

oh and the max recommended temp is about 700c

HTH

LRH

**Blknight.aus** · 30th December 2006, 10:30 PM

back it down a tad mate 650 deg c is normally about the limit for turbos unless you have a more exotic turbo (and pistons and and and and), in the states they will quite happily quote 1000+ degree values and it sure sounds impressive untill you realise that they talk foreignheights.

**Bigbjorn** · 30th December 2006, 10:34 PM

I used to have terrible trouble getting truck drivers to use the pyrometer as a driving tool. The idea is to back off the throttle and maintain the same speed at the lowest exhaust temperature. Excess fuel still burning in the exhaust is the reason for the elevated temperature. Not good for your turbo or your fuel bill having a wide open pump squirting in more fuel than the engine can usefully burn.

**rick130** · 31st December 2006, 05:21 AM

stock fuelling/max boost = 623*C in my experience on 2km long climb over the range here. Used to range from 612* to 623*, depending on ambient and fuel (which used to vary a bit pre ULSD)
Fitting 3" exhaust dropped this by over 20*C, giving more scope for safe power gains. (2.5" off dump pipe, [stock is 60mm/2,3/8"] 15* taper up to 3" starting 15mm below flange)

Generally accepted safe maximum pre turbo reading is 720*C, stock internals, post turbo 550*C, although many diesel tuners have noted stock Nissan Patrol 4.2TD (non intercooled) often far exceed 550*, sometimes approaching 700*, post turbo !

720* is very easy to exceed only using the diaphram adjustment on the aneroid (boost compensator) In my experience the max fuel adjustment doesn't need to be touched on the back of the pump.

**TuffRR** · 31st December 2006, 06:33 AM

I've found that my EGT's will go to around 710 on really long climbs. Doesn't really go any higher and regardless at this stage i start backing off.

Interestingly, it is possible to maintain the same speed up a hill but use less throttle and hence less fuel and lower EGT's. I guess this is the difference between driving my tdi vs my 4.4 V8 RR. Gotta love the instance throttle response of the V8!!!

**Bush65** · 31st December 2006, 07:39 AM

When I 1st tweaked my pump (diaphram only), the egt didn't exceed 720C on my local hills.

But pulling the boat trailer (not heavy) and the disco loaded with camping gear, it would easily exceed 720C and I had to drive with 1 eye on the egt gauge, even on easy hills.

**Grizzly_Adams** · 31st December 2006, 08:49 AM

On mine when towing the 1.2tonne fully loaded camper up to Cape York I always tried to keep the temps below 600 degrees. I found that on one long arduous soft gravelly hill I kept the temps up around 600+ degrees for a prolonged period of time and by the time I was half way up my "normal" temperature guage was starting to rise also.

So I try to keep my temps below 600 as a rule.

natanchris · 31st December 2006, 09:07 AM

My 300 tdi is usually below the 400c mark on the highway (it is an auto), but can climb over 700c on a long steep climb, foot down hard. I don't usually let it get much over 600 for any length of time. There was a link on Outerlimits to a site from an American diesel tuning specialist and they advised a max temp of (converted from farenheit) about 725c. Justin C says he usually aims for a sustained of around 600c when he tweaks his customers cars in Tassie. Hope this is of some help, Cheers Chris.

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