Stavros

How can you (SAFELY!) install a gauge to read exhaust gas pressure in your exhaust manifold?
Bearing in mind EGTs can get to 1000degC i cant imagine the methods used to measure boost is very safe

What about the pressures themselfs?

Is there a backpressure number where its gone into the realms of dangerous for the engine?
Ive heard people say not to let your backpressure exceed 2.5times your boost pressure.
Ive also heard people saw that if your backpressure is double your boost pressure youd get more gains from dropping the boost lower and advancing the ignition?

Is it purely a trial and error thing with regard to gaining power (without going to a larger exhaust housing) or is there some basic guidelines to go for?

Hopefully this might get the forum all techy again as its been nothing like it for months...

foreigneRS

this was discussed slightly before in a thread steve. i think that it was alex with the turbo mini.

we decided that it should be possible to measure it using a normal manometer. the reason being that it won't get hot at the gauge end very quickly because the pipe will be closed so there will be no mass flow of hot gas up to the gauge.

someone pointed out that the pressure suits that pilots wear are directly pressurised by the jet engine gases, and they don't get hot.

don't know what sort of pressure that you'll be looking at though

Andreas

If you use an electrical sensor that will get hot and what about the plastic connector? And what kind of hose do you use with a mechanical gauge, it will get hot close to the exhaust.

Neil S

iTrader: (1)

Andreas,

I reckon you could easily get metal tube with the same diameter as the capillary tubes for mechanical gauges

Neil.

JesseT

It's ok if the first meter of the whose copes with heat. After that it doesn't really matter anymore as there is no flow.
Some people even think that the backpressure should not exceed the boost pressure.

extra14

I would use 4mm copper pipe 1.5m long, then connect to 4mm pfte pipe to prevent conduction.

Thanks
Darren

Karl

Steve,

For EGT's in the exhaust manifold, I drill and tap each header and use a tapered olive boss suitable for a k type thermocouple. These bosses can also be blanked should you chose to remove the thermocouples after by simply using a blanking cap that screws over.

As a ball park figure I aim to keep preturbo manifold EGT's to less than 950DegC but up to 1000 is Deg C is ok. Post turbo temperatures in the down pipe can be as much as 200 DegC cooler and thus cannot be used to accurately determine peak EGT's.

With regard to measuring back pressure this is primariliy of importance post turbo in the exhaust system. The exhaust manifold back pressure pre turbo is something we can do nothing about as it's a function of the turbine specification and boost required and I don't normally measure this as I'm monitoring EGT's anyway. However measuring exhaust system back pressure is of great use, and I normally use a small fitting again screwed into a boss in the exhaust and use steel capiliary tube for the first few feet. Bare in mind the hole size in the exhaust boss only needs to be tiny to get a pressure reading and something less than 0.5mm is suitable.

With exhaust back pressure the rule of thumb is as low as possible, though I'm not going to give you any ball park figures as that would give the game away as to when certain exhaust sizes become restrictive!!

AlexF

https://passionford.com/forum/viewtopic.php?t=80144

Alex

Matt

karlos what happened to simply the customary LOL

vroooom ptssssh

cant backpressure be either eliminated completely or as close to none as poss?

Stavros

Karl etc- Cheers, thats pretty much it

Dave/Vroom- You mean before or after turbo?
Before would need such a big exhaust housing itd never spin up.
After, yes, easy.

vroooom ptssssh

after i mean steve, jus a large bore exhaust all the way bk i'd immagine!

Stavros

Basicly, yea.

Shorter the better.

Ever seen an Indycars exhaust?
After the turbo its just a single lil stub of an exhaust about 6inches long just to get the exhaust gas past the bodywork, seperate exhaust from the wastegate is exactly the same too

vroooom ptssssh

Good point i have noticed that aye! wheres my angle grinder