Outer Limits 4x4 Board

Can someone explain how Hi-flowing is done?? And are there levels of flowing?

Is it like polishing a head to take the burrs, castings, and shit off, or is it actually changing the wheel and stuff?? And what is achieved thru the process - faster spooling? more boost less EGT?

I've googled and found 3 sites telling conflicting things :(

And I know it depends on the turbo, but is there a scale to figure out how much more sniff you will get or how much quicker it will spool up? (if thats what it does?)

Thanks

Hi Mate - i have been doing some concerted research on this over the past few days, including speaking to Dzltec about my dramas and the progression of your set up...

anywho - as i understand it, hi-flowing is when they machine out the insides of the external housings of the turbo. ie the air intake side and the exhaust side. These very small alterations to the "window" as apparently its called gives a combination of things one of those being the ability to fit larger or different pitched compressor wheels (i think) and lowering EGT by reducing restrictions and heat build on the inside of the housing. I think caused by air friction between the impella and the housing...

It is usually done in combination with a BB centre which i've been told is approx 40% more efficient and this will also reduce heat, reduce lag on spooling up, less exhaust required to maintain boost/exhaust side spinning at constant cruise and producing more efficient boost at lower RPM. This combined with the fact that EGTS are lowered means boost can be lowered for more efficient burn to maintain existing power/toprque figures or alternatively, and as most here would do, fuel can be upped along with boost until top EGT range is achieved. IC it and again more boost and fuel can then be added (if your pump can handle it)

Hope that helps, may not be entierly correct but thats my understanding after considerable discussion over the last few days.

benhl wrote:Hi Mate - i have been doing some concerted research on this over the past few days, including speaking to Dzltec about my dramas and the progression of your set up...

anywho - as i understand it, hi-flowing is when they machine out the insides of the external housings of the turbo. ie the air intake side and the exhaust side. These very small alterations to the "window" as apparently its called gives a combination of things one of those being the ability to fit larger or different pitched compressor wheels (i think) and lowering EGT by reducing restrictions and heat build on the inside of the housing. I think caused by air friction between the impella and the housing...

It is usually done in combination with a BB centre which i've been told is approx 40% more efficient and this will also reduce heat, reduce lag on spooling up, less exhaust required to maintain boost/exhaust side spinning at constant cruise and producing more efficient boost at lower RPM. This combined with the fact that EGTS are lowered means boost can be lowered for more efficient burn to maintain existing power/toprque figures or alternatively, and as most here would do, fuel can be upped along with boost until top EGT range is achieved. IC it and again more boost and fuel can then be added (if your pump can handle it)

Hope that helps, may not be entierly correct but thats my understanding after considerable discussion over the last few days.

Sweet... some food for thought..
EGT's are my worry, anything to help keep them down is a WIN.
Will talk to Andy bout it.

Some points about EGT's and turbos.

Firstly, turbos thrive on heat. The higher the temperature of the exhaust gas you feed them, the more efficient they become. As they get hotter the drive pressure drops.
On my current turbo setup (tiny turbo on a 3.9L diesel) the exhaust pressure starts out around 1.5 times boost at cruise (EGT's around 400-430C) and drops linearly as the temps rise.
Above 600C exhaust temps the boost pressure is above exhaust backpressure. At this point the turbo is essentially feeding entirely off exhaust heat and is greatly helping engine efficiency.

Secondly, EGT's are a result of your air/fuel ratio and your intake temperatures. Cooling your intake charge (intercooler) cools your exhaust. Running leaner (more boost for the same fuel) also cools your exhaust.
Smaller turbine housings create more boost and lower EGT's. This is not understood

Thirdly, EGT's do not skyrocket with increased backpressure. The EGT's only raise in line with the normal pressure/temperature relationship (the ideal gas law) which means you need a massive drop in pressure to get a drop of around 50C in temperature.

Most of the mods done to turbos come from the ricer world and are counterproductive in diesels. Petrol engines have heaps of spare exhaust heat so you can do awful things to the turbos with only minor consequences.
Ricers get turbine wheels trimmed (clipped) which reduces spool but lets them flow more air, doing that to a diesel increases your EGT's and gives you more lag.

There's some guy on clubisuzu who got a subaru turbo housing and fitted it to his isuzu to get more power out of it (ricer trick, bigger housing for more top end), he found out why Isuzu used the smaller housing, he had to pull 3000rpm to get any decent boost. He didn't have an EGT gauge, if he did it would be scary.

On diesels smaller exhaust housings are necessary to get more boost to control EGT's and smoke. Fitting a bigger housing to drop EGT's is counter-productive.

tritontray wrote:http://www.outerlimits4x4.com/ftopic115 ... ght=hiflow

Search is your friend.

I didn't want to say anything...........nice to know even the 'preachers' get it wrong.

Maybe this post is an example of how crap the search function is. I will give him the benifit of the doubt that he looked.

I couldn't help myself.

tritontray wrote:I didn't want to say anything...........nice to know even the 'preachers' get it wrong.

Maybe this post is an example of how crap the search function is. I will give him the benifit of the doubt that he looked.

25 pages actually, and its still only upto Tue Jan 01, 2008 7:47 am and no mention of it.
http://www.outerlimits4x4.com/phpBB2/se ... &start=720
and I'll still be the preacher... even if its just to piss people off.

All good bogged !

cutting across bogged, and his concerns over EGT, do people run an egt on a turbo petrol motor?

not many that i have seen, most run an air fuel gauge

Reddo wrote:cutting across bogged, and his concerns over EGT, do people run an egt on a turbo petrol motor?

I was told that Petrols dont have any issues at all with temps, where diesels shit the bed instantly when they get too hot...

Yes over fuelling is probably the biggest issue. but you do what ever you can to help..

bogged wrote:

Reddo wrote:cutting across bogged, and his concerns over EGT, do people run an egt on a turbo petrol motor?

I was told that Petrols dont have any issues at all with temps, where diesels shit the bed instantly when they get too hot...

Yes over fuelling is probably the biggest issue. but you do what ever you can to help..

The temperature vs air/fuel ratio is a hump, diesels run on the lean side of it, petrols at full throttle run on the other side.
Petrols use extra fuel to lower the EGT's. If you keep a tight rein on the air/fuel ratios (which petrols have to just to run smoothly) then the EGT's look after themselves.
But if a petrol leans out full load, you can get meltdown.