What the hell is A/R?

[Samdweezel05]

I don't know enough about these little things to look for my new one so I might as well ask and sound stupid. The turbo I am looking at has 4 different exhaust housings or A/R. What does this mean. I know it is a measurement but what is it measuring and how does it change things. I see the bigger A/R's flow more but I would have to imaging that they also spool slower. How do you pick?

 

[RPM Motorsports]

http://www.moddedmustangs.com/forums/power-adders/628-turbo-size-r-trim.html

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[JoshH]

If you get into selecting turbos, this is a good resource for understanding what everything is and how to select them: http://www.turbobygarrett.com/turbobygarrett/tech_center/tech_center.html

 

[MAXLLY]

The smaller the number the earlier it comes on. The larger the number the later it comes on. Tuning can help some of this.

If your gonna drive it on the street alot... pick the smaller numbers. The housings can be removed and repalced with smaller or larger jousings. example Borg Warner/Airworks exhaust housings are about $150 IIRC.

Think small here, it'll pay you back on a street truck. Memr, first on the pipe puttin' it to the ground wins, not fastest from 60-120 by then iots all over.

Take a look at the Airworks stuff as well. They have extended tips for a little broader range and a softer hit, generally.

good luck Dude.

 

[jonathancasey19]

From what I've heard...... the larger housings will give you more top end whereas the smaller will run risks of blowin head gaskets

 

[malibu795]

The smaller the number the earlier it comes on. The larger the number the later it comes on. Tuning can help some of this.

If your gonna drive it on the street alot... pick the smaller numbers. The housings can be removed and repalced with smaller or larger jousings. example Borg Warner/Airworks exhaust housings are about $150 IIRC.

Think small here, it'll pay you back on a street truck. Memr, first on the pipe puttin' it to the ground wins, not fastest from 60-120 by then iots all over.

Take a look at the Airworks stuff as well. They have extended tips for a little broader range and a softer hit, generally.

good luck Dude.

or

get a smaller housign adn add a waste gate and you can push it farther/harder then a bigger housing

 

[Turbo Buick 6]

A/R is the aspect ratio the provided links should help you.

 

[McRat]

A/R is how tight you make the nozzle that you spray the gasses out of towards the wheel. Like your thumb over a garden hose. Too loose, it doesn't go far, too tight, ditto.

What I found is there is a "right" turbine housing A/R for each size compressor wheel on our trucks. For a 102mm charger on our engines it's about 1.15. Tighter will make less power under the curve, and looser will make less power under the curve. Not a big fan of .90 housings or 1.2x housings. IMO...

 

[MAXLLY]

or

get a smaller housign adn add a waste gate and you can push it farther/harder then a bigger housing

Don't forget overspeed avoidance with N2O as well.

I'm starting to think my 90 housing may be to large, really its to early to tell.

OT sorry.

 

[McRat]

or

get a smaller housign adn add a waste gate and you can push it farther/harder then a bigger housing

The instant that gate opens, it doesn't increase the A/R, it drops the turbine torque.

 

[mytmousemalibu]

Great thread! Now how bout twins? Would you have some room to stretch your legs on the big charger and go bigger A/R?

Sorry for thread jacking:hug:

 

[malibu795]

Don't forget overspeed avoidance with N2O as well.

The instant that gate opens, it doesn't increase the A/R, it drops the turbine torque.

that is what i was gettign at...

if you gate a charger at 40psi the only way you will get more is to generate more exhaust flow then both the trubine and gate can flow.

a gate alows one you use the charger more in a linear direction accros the map then a non gated charger. which is more a diaganal from bottom left to top right

a gate allows a person to use a smaler housing wiht out the risk of overspeeding and higher egt towards the top end that you would normally see with a non gated small housing.. and you would have ot increase housing to kill egts and sacrifice low end repsonse and have higher egt while cruising.

also can use a gate to control drive pressure as well.

 

[Turbo Buick 6]

or

get a smaller housign adn add a waste gate and you can push it farther/harder then a bigger housing

Not true

Had a gated charger on my buick that was in the .6X range and went to a .8X housing and picked up 3 tenths. The larger AR lets you drive the charger harder with less DP.....if you have the exaust flow to do it


A smaller AR with a gate is a crutch for limited exhaust volume

 

[jonathancasey19]

What kinda a/r's are generally ran on the 88 and 94?

 

[MAXLLY]

The instant that gate opens, it doesn't increase the A/R, it drops the turbine torque.

Agreed, but I don't need torque (effort to get it moving, its moving fast enough at this point) I need to relieve some back pressure so it'll continue to work instead of "clog up" with excess pressure and heat.

The A/R is fixed all we can change is the pressure. It could be a band aid if the A/R was way to small and another housing couldn't be had.

 

[McRat]

What kinda a/r's are generally ran on the 88 and 94?

I'd have to go back and look, but IIRC, the 1.06? is the one for our trucks.

 

[Samdweezel05]

Very helpfull info. Thank's guys.

 

[WolfLMM]

A gun that shoots peas.

 

[03 D-max]

A gun that shoots peas.

PostWhore

Phil what are you getting for a charger gt47? gt50?

 

[Samdweezel05]

Maby neither now. I found a super secret hook up for super secret chargers. I will let more info out when the time is right.