Truck turbocharger with large hot housing.

[noshell]

Hi guys, ive just bought a truck turbocharger, but it has quite a large hot housing. The compressor inducer is only 48.3 and the turbine exducer is 58.4

Im not sure how i should build the flame tube. Intuitively i think i should make the flame tube slightly smaller so it keeps that turbine wheel nice and hot and keeps pressure high.

Maybe a 100mm diameter flame tube.

Can i have some feedback on my thought process?

[racket]

Hi

At 46% bigger "hole out" than "hole in" the turb exducer is a tad large , but it will depend on what the turb scroll A/R is as to whether or not your"matching" is optimal or not , it'll work OK anyway :-)

Yep , you'll get away with a 100mm dia FT , but you'll need to have good fuel and air mixing , the size of the flametube won't change either temperature or pressure going into the turbine unlike in a "turbocharging" scenario , we're different.

Checkout Jetspecs for holes

Cheers
John

[noshell]

Thanks for another detailed reply
The turbo is a twin scroll which i can only imagine will help with the fact the turbine is abit too large? My understanding is a twin scroll will spool up easier.

Also, ive seen what happens if the flametube is too small (pressure backing up against the compressor wheel) What happens if your flametube is too large? I cant find any literature on this and im curious.

[noshell]

Im thinking of going all out on this next one, i might try to run it on diesel.

Presumably you guys dont run injectors at thousands of psi like in a car engine?

[wannabebuilderuk]

Twin scrolling on the turbine side isn't ideal for our applications as the extra surface area slows the gases down and takes a lot of heat out too.

As for fuel we primarily use kerosene or a diesel/petrol mix (around 80% diesel) and you can run anything from 100psi + combustion chamber pressure to several hundred/thousand psi for finer atomisation and better fuel control which is what I will be doing using a 1cc/r hydraulic pump and setting my set up to ~700psi

[noshell]

I could grind some of the twin scroll out from the flange side?

[racket]

Hi

Nope , a twin scroll doesn't help spoolup , it'll actually slow it down due to greater losses from the extra friction , again , you are thinking "turbocharging" , we're different .

No , an undersized flametube doesn't add "backpressure" , it simply prevents combustion due to excessive air speeds and combustion intensity , an oversized flametube will generally have good combustion due to the increased dwell time and "low" combustion intensity .

A simple spray nozzle with 100 psi of fuel pressure , or an evaporative system with even lower fuel pressures is all we need .

Cheers
John

[noshell]

Thanks again for the replies.
So the turbine housing has an A/R ratio of 1.0
I cannot find it the AR for the compressor housing. How does the turbine AR affect the jet? I notice you diddnt mention the compressor AR. Is it less important? Thanks, i appreciate all the info.

Im starting to think that it might just blow the flame straight out the back.

[racket]

Hi

The comp A/R is "calibrated" to suit the compressor wheel , it can't be changed, unlike the turbine scroll A/R where there is usually a few sizes available .

You won't "blow the flame straight out the back" if your flametube is constructed to Jetspecs and your fuel injection is as required .

The turbine scroll A/Rs generally influence the mass flow through the engine if the turbine wheel is suitably large enough not be the restriction, as is yours.

Your engine should work just fine ,..... build it :-)

Cheers
John

[noshell]

Thanks John