Thread: Bigger exhaust fix for VNT Td5 with high gets?

Sounds like an interesting combo
How high are we talking?

I'll give you a buzz tomorrow Max about the exhaust.

(This vehicle really IS a v8 eater DMuppet.... you'd have to drive it to believe it. However it can quickly see 800 degrees with a tow load (2.5+ton) if you aren't watching...)

jc

Oh I can hear the howls and shrieks of the petrol heads already
Mine will be too JC.
One day.....
Oh wait.
It already is

Originally Posted by Disco Muppet

Oh I can hear the howls and shrieks of the petrol heads already
Mine will be to JC.
One day.....
Oh wait.
It already is

yup, thats why i said it!

jc

As Justin says, (hiya Justine) an unloaded vehicle full bore 0-100km blast will see 750-780. Towing on level 450-550 at 90-95, big hills well I drive to control egts but would hit 800 at the top. Recovers very rapidly. I'm curiuos not concerned as JC has done all the work ;-) . Wonder why the exhaust mod is talked about when turbo outlet is the major constraint isn't it. I'm kinda with Justin's advice, ie why big pipe if turbo is smaller diameter. But I'll try anything if I can use my torque more on hills. Max

I dont have VNT on my Td5 Defender but have all the other fruit, was getting high EGTs towing my van up hills, I don't want to go around Australia looking at the EGT gauge, so got onto Td5inside for a custom map for towing, Try no 1 was over boosting , a few more tweaks and Jose has got me a map thats perfect for my combo, EGT now refuses to go over 700 in 5th, tho I can push it over in 4th but thats fine. No black smoke, no over boosting, heaps low to midrange grunt, and without the Van goes like a cut cat, absolutely creams over any V8 Landy I've had. and fuel economy is leaving a smile on the dial !!

just saying , worth dropping Jose a line.

There has been some discussion on EGT's and exhausts somewhere around here about 12 months ago.
With the mods you have done I have no doubt you have been doing some careful reading.
Reduction of EGTs by using a bigger exhaust is subjective for many, however, it is worth noting that EGT's are a direct function of the combustion process.

As the design of domestic motor vehicle engines doesnt warrant the expense of monitoring the combustion process at all in most cases let alone, at a more accurate position such as the thermocouples in machinery such as aircraft and other specialised engines, an EGT monitor is the most effective and reliable means for the masses to use, but remembering it is exhaust gas temps being monitored at varying positions (i.e whever it fits) for determining critical combustion temps.

This has proven to be generally a reliable method of monitoring, however, it is monitoring the gas temperature post combustion after expansion and therfore cooling.
A drop of some 200deg C is common between probes pre and post turbo on the TD5 in std trim yet the combustion temps have not changed.
A bigger exhaust will not normally help lower your actual/true combustion temps and therfore EGT, but rather will significantly affect the gas temp experienced at the probe, unless your bigger exhaust allows the turbo to constantly produce more boost, therefore more/denser/cooler air charge you will not see lower combustion temps/ EGT.
Otherwise modifications post combustion will be an influence on the probe only and has led some to believe that the actual combustion process is now cooler, giving a false sense of safety margin and now happily peg the engine based on the modified reading at the probe.

The only way to have genuine cooler egt's is to provide cooler/denser air or less fuel for a given charge volume to lower the combustion temps.
Something you have already addressed with bigger IC and boost box.

The popular exhaust sellers claim the reduction of EGT's with their products as will a few here.
Increased performance due to free flow, turbo spool, cooler overall operating temps through the faster removal of hot gases are all benefits of the right sized sytem, but wont reduce the combustion temps.

cheers

Originally Posted by silverhammer

Any comment on the value of a bigger free flow exhaust in reducing gets on my 03 D2auto would be appreciated. I've got a BAS VNT, bigger custom IC and map from Peter Bell BAS. Boost box also from Td5Alive. After over boosting still falsely registering, I bypassed the MAF from airbox successfully. Goes like a cut cat, great economy but big hills and towing really arabise the egts. Can moderate with right foot but would love to unleash the rest of the grunt when under load.

Maybe silicon hoses on IC input side too?

Cheers
Max

A bigger free flowing exhaust will help if your current one is restrictive, if it is standard it will restrict gas flow.

Also

Have a look at water/methanol injection, you will easily take 100-200 degrees out if configured properly.