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Niran

Benefits of larger sized downpipes

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😂 9” pipe. 

 

I’ll stick to my tiny 4” that the v band on the turbo is. 

 

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10 minutes ago, Gripless said:

I’ll stick to my tiny 4” that the v band on the turbo is

 

Aren't all EFRs 3" vband outlet? 

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Waa. True I’ll have to flare out the pipe and make something fancy. 

 

Still bet there is no room in engine bay before right bend anyway. 

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Posted (edited)

Most likely. If i understood correctly form the article, even though the turbine outlet is 3" you will still get big gains from increasing the diameter of the downpipe. The larger cross sectional area of the downpipe means the highly turbulent air post turbine has more room and length to sort itself out, as apposed to being jammed through a 3" the whole way. This reduces back pressure and should increase spool and power. The dyno figures to back it on his post are just nuts.

Edited by Niran
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Posted (edited)

Sadly my down pipe is smaller at 3” than rest of the exhaust 😭

Also explains why removing the cat in down pipe is so much more effective than any other cat. 

 

 

This looks like the same as the CNC head thing. What is good for NA is good for turbo just making the air pump aka engine work more efficiently. Which is the whole pressure differential thing. 

but mostly covered up by cranking up the boost since that is easier. 

 

Looks like two stroke exhaust, step up quickly to get gassed out then taper back down. Wonder if two stroke exhaust modelling would help design the sump pipe?

Edited by Gripless
Cry

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Yeah man. Think i'll do full 4" to my current 3" downpipe with a taper when i eventually upgrade turbos. :D 

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Posted (edited)

Eventually upgrade 😂 

At this rate sell the GR and get the VA 

Edited by Gripless
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Can someone ELI5? Regardless of turbo size, get/make the biggest downpipe you can? 

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39 minutes ago, Timmah said:

Can someone ELI5? Regardless of turbo size, get/make the biggest downpipe you can? 

 

Basically. I read somewhere in the original post that the best match would be 1.5 times your turbine wheel diameter. So for me its 70mm turbine x 1.5 = 105mm or 4.1"

 

So ELI5 - Get the largest possible downpipe you can fit in there

 

F1 cars basically run no exhaust - turbo outlet is the exhaust. That would be the best you can get. So for our street cars, just largest possible downpipe. 

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Fascinating. I wonder how large of a downpipe you can even fit in behind the turbo on our cars though? When mine finally gets an exhaust built I'll probably go for a 4", at least for the first 50cm or so.

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@boon yeah that'll be the challenge aye. Will try make 4" work lol 

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I think @Batbaruman had a 4" downpipe on his V7? Or at least someone on here did. Need to find a nice short 3"-4" transition in stainless, ideally. I wonder if someone makes a nice billet one with a 3" v-band flange integrated....

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s-l300.jpg

 

That'll do it. Weld v-band flange on the 3" side and its Christmas. Thats off ebay. Surely will be some NZ variants floating around

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I think [mention=20441]Batbaruman[/mention] had a 4" downpipe on his V7? Or at least someone on here did. Need to find a nice short 3"-4" transition in stainless, ideally. I wonder if someone makes a nice billet one with a 3" v-band flange integrated....

Nah was 4.5” intake pipe but pretty sure downpipe was o my 3” , might have pics somewhere if someone needs but don’t think you’d get more than 3” very easily there


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Posted (edited)

More use to @preim with the alto. 

4” dump pipe on the 660cc. 

 

Low mount may allow a 4” through the 90 degree bend at the front of the motor.

 

@Niran have you sold @j_bone on the idea yet?

Edited by Gripless

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@Gripless He can't fit a 3" off the turbo - no space for now. But it expands to a 4" downpipe at about where the headers are

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Flatten the pipe to an oval shape. 

 

 

Still want to see the 4” side exit on the alto. 

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Jumping to the other end of the turbo. Has anyone found any relevant articles on turbo inlet sizes and their impact. The ’smaller’ EFR’s with 2.5inch inlets seem crazy small sitting next to GTX Garrett’s with 4inch outer shrouds which must still give 3inch plus inlets (Should probably go measure mine to be sure).

 

Even with the inlet itself being not hugely larger the potential restriction reduction of a bigger inlet tube must have a similar impact to the larger downpipe

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EFR has the BOV inside the housing so that recycling likely helps more than a bigger inlet. 

 

There was like some SAE stuff on inlet tracts somewhere.  Best one was long taper in but not really practical space wise. 

 

 

Isnt there like metal spinners that can shape pipe like that in nz. 

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