Combustion chamber and flame tube parts ideas

[adamr]

I used a 3/8 tube that went in about 1 1/2" and about 8 holes only going radialy, not shooting out the tip.

[adamr]

Im trying to buy a turbo now but the descriptuons are confusing, the top part say its the compresor specs which states 52.7mm which is like 2 inches, than under turbine specs it says inducer size is 64.8??? I thought inducer size is compressor and turbine is exducer, so that kinda confusing and than at very bottom is states compressure is 68mm which is a totally different measurement that what its says at the very top

[adamr]

[racket]

Hi Adam

With the comp wheel the inducer is where the air goes in and its exducer is where the compressed air goes out , with the turbine wheel its the same , inducer where the gases go in and exducer where they come out , the difference is the positions are reversed .

That turbo mightn't be suitable even though the wheel sizes are OK , the turb scroll A/R is "tight" at 0.57 and theres an internal wastegate , but it might still work as turbos of that size have wide maps as they're designed for autos that come on the boost early and stay on boost through most of their rpm range .

The comp sounds like a GT2876 but the turb is from a bigger Gt32 , maybe worth a try :-)

Cheers
John

[adam]

Gotcha, well i was gonna weld the waste gate hole closed, just worried about since the turbine is smaller than the compresor because everyone here is saying its better for turbine to be bigger, but would it still work if i closed the waste gate off?

[racket]

Hi Adam

All of our turbine wheels are smaller in overall diameter than our compressor wheels , generally ~90% of comp wheel diameter.

What is preferable is the turbine wheel exducer/outlet diameter is larger than the comp wheel inducer/inlet diameter.

This turbo has a 52.7 mm comp inlet hole and a 55.8 mm turb outlet hole , so OK , the 55.8 mm turb inducer is ~85% of the comps 76 mm exducer , also OK .

Wastegate holes need welding shut , all gases through the wheel to maximise the turbine power to drive the comp , this will keep temperatures low .

Cheers
John

[adam]

Thanks john, sry for so many questions ive now watched a few youtube videos about inducer and exducer and how to rrad the numbers and specs when buying a turbo, appreciate all tge help from everyone here, i know this has probably been mentioned on here, i have been reading through the forums but there is allot, so with the flame tube holes, i was wondering if its better to have the last stage "cooling" holes, at the very end of the flame tube this way colder air comes in closer to the turbine rather that how i see most flame tubes with the last stage holes maybe 1 to 2" fromcthe end, not sure if it rely makes a difference or not, also was wonder about the primary as well as i see people making them also 1 to 2 inches away from the end, i seen a post on here about that part and someone just mentioned that if you have the primamry holes at very end than it just adds cooling air to the end cap, i was also wondering if maybe this helps the fuel mix better if you use a short fuel nozzle with maybe 6 radial outlet holes and maybe keeps the flame front higher away from the end of the tube which might allow for cooler gasses before entering the turbine. And lastly when i make the flame tube 6x the inducer lentgh can i add the flare down peice of tubing that connects to the turbine shroud, after that equation, or does that peice of pipe need to be factored in with the entire lentgh of the 6x rule?, thanks.

[racket]

Hi Adam

You want the Tertiary holes some distance from the turbine wheel to allow mixing and cooling of the extremely hot gases before they reach the turbine scroll and wheel .

Primary hole displacement is more complicated and will depend of fuel injection type and fuel used , with propane injection you want the injection radially towards the flametube holes , so depending on a number of considerations it can be higher or lower in the flametube , if too high the endcap will need "cooling" with high placed holes but that air then contributes to the overal primary air for combustion .

With propane being such a fast burning fuel, the flametube length can be shorter than with liquid fuels , so 6X inducers including the transition "funnel" should be OK.

Different engines with differing fueling methods can have diffent shapes , Jetspecs is a generic set of numbers that "work" in just about every scenario , but with my evaporator equiped engines like the GT6041 its flametube was was "different " jetandturbineowners.proboards.com/thread/78/garrett-gt6041-powered-kart?page=3 but still worked.

Stick to the "standard" Jetspecs setup and your engine should work , Primary at ~1/4 way down , Secondary at ~half way and Tertiary at ~3/4 way

Cheers
John

[adam]

Hey john do you have any idea of a rough guestimate of the thrust you get from a 1" 2" 3" and 4" diameter inducer sized turbo :] im sure theres allot of factors, but kinda curious as to what size people are using on gokarts

[racket]

Hi Adam

LOL.............yep , a huge number of factors will influence thrust outcomes besides the inducer diameter, but its the greatest influence

If we can achieve 50 lbs of thrust per pound of air per second we're doing OK , 60 lbs fairly exceptional .

Mass flow per square inch of inducer can be ~12 lbs/minute , so for a 1" dia inducer of 0.78 sq ins , thats 9.4 lbs/min so maybe a few pounds of thrust , a 2" dia of 3.14 sq ins might get up to 30 lbs , a 3" maybe 70 lbs , a 4 " maybe 125 lbs of thrust , add on ~40% for an afterburner and it'd produce ~175 lbs .

To get any sort of performance from a kart you'd need at least a 3" inducer unless you go for a 2 shaft arrangement and produce shaft horsepower , then a 2 inch inducer will start to do the job .

Cheers
John

[adam]

So i got this prefilled jetspecs sheet online, i for some reason cant use jetspecs on my phone so im going to base the build of this 2.5 inducer prefilled sheet, i saw this turbocharger on amazon which i like and was wondering if the specs will work for this jetspecs sheet, the inducer is 61.5mm which equals to 2.4 inches which seems pretty close, will that still be ok following all the drill bit sizes and amount of holes thats on that spec sheet or should i make sure the turbo i get comes out to exactly 2.5 inches for that jetspecs sheet? Figure its so close it shoukd work but im not the expert here, i was a little confused because on the bottom of the specs it says compressure inlet is 4" but im guessing that is including the surge holes and that whole section around it, so im going with the 61.5mm size, this should be the right size. I also noticed its water cooled, i wanted just a plain oil cooled one but i heard this will still work and dont gotta use the water ports, not sure if a oil cooled one is better thow if your just going to cool it with oil but i cant find one with this size inducer.

[adam]

[adam]

If that turbo is ok, please let me know, im gonna buy it as soon as you tell me and than i could get this thing started and get the flame tube stuff tomarrow, thanks man :]

[racket]

Hi Adam

Nope , this turbo has both a smallish turbine exducer as well as a small scroll A/R , both will conspire to cause problems if you try to run anything more than modest turb temps , but it should be OK to use if the comp flows like the GT3582 , it has a wide map at 2:1 PR so keep the comp pressure down to 15-18 psi and it should cope

Water cooling only needed in an auto scenario to prevent heat soakback and lube coking , we just keep the oilpump running after shutdown to cool things

Our flametubes can cope with some variation in flows, so no concern with the difference between a 2.5 and 2.4 incher , its in the right direction :-)

Cheers
John .

[adam]

Ok so just look for one with a bigger turbine exducer? Like make sure the exducer is at least the same or bigger than the compressor inducer, just not smaller? I keep seeing a bunch of turbos on there where the turbine exducer is just slightly smaller than the compressor inducer. But I thought I saw a T3 T4 Turbo charger jet engine, Isn't that got a smaller turbine exducer thow