Outer Limits 4x4 Board

before or after turbo??

reading up on this getting conflicting info..

sd33t engine

I guess you're mainly interested in the exhaust temp as an indication of the turbo temp? If so, as close to the turbo as practical I'd have thought. I'd be inclined to put it after the turbo unless there was a good reason not to - if it was to disintigrate, bits won't go through the turbo if it's after it.

Realistically it's the combustion temperature everyone is concerned about - post turbo is not the best place to have the pickup as the turbocharger itself dissapates an indeterminate amount of heat and converts it into energy which is used to spin the compressor wheel.

Pre-turbo is the cheese, even better pre-turbo one per cylinder - but this is fairly impracticle given the $3-400 price tag of EGT gauges. The post turbo solution is a happy medium, although it's harder to judge what is "correct" as it's only a representative figure based on the actual EGT and the heat dissapated by the turbocharger.

So put a hole in the manifold ??

most figers r after turbo tacking into account 4 the turbo

but why???

if its exhaust temp which you are after(which you are, )then why put after turbo????

zen wrote:but why???

if its exhaust temp which you are after(which you are, )then why put after turbo????

If the EGT sensor falls apart, the bits won't go through your turbo if it is mounted in the exaust.

True - this is a risk, but the chances of a welded stainless EGT sensor thermocouple probe when clamped in place with an externally mounted stainless compression fitting are minimal.

It is the *combustion temperature* you need to measure - not the "exhaust gas temperature" - if this were the case ... then you could put one at the end of the exhaust pipe.

The primary purpose of an EGT is to measure how hot the gas is exiting the cylinders - not neccessarily the turbo.

But as rightly xenith points out - most figures quotes are post turbo figures.

So could a person place the thermocouple on the exit of one cylinder only. That would be even closer to the correct temperature than a before the turbo all cylinders at once placement?

In aircraft applications, this is typically the solution - 1 EGT per cylinder, which gives the best possible indication of combustion temperature per cylinder. In this way it's possible to see what is going on with one particular cylinder and identify over/underfuelling (injection problems etc.).

However at $400 / cylinder it's pretty hard to justify the expense.

Thanks,

So what about 1 probe on 1 cyl with one readout? Would there be a significant downside to doing this on a diesel vehicle compared to an all cylinders placement?

cheers fnq

Spannercrustacean has got it right!!

Having said that.....Look, stop sweatin' abt an EGT either before or after the snail...the cheapest (but not necessarily the nastiest) option is to plug it in after the turbo...most aftermarket exhaust guys provide a blanking plug in the dump pipe.

Check this thread for more interesting info..

http://www.outerlimits4x4.com/PHP_Modul ... hp?t=68211