Compound air ratio and gate questions

[windrunner408]

The difference between the .83 and .91 with the same turbine wont be much if at all different.

How does this make any sense??

 

[Pizza pig]

If using the 68 turbine wheel, there will be no noticeable difference between the .83 and .91 spool up wise


Hellen Keller sent this?

 

[windrunner408]

Got ya. I'd agree with ya there.

 

[NRHX2009]

If using the 68 turbine wheel, there will be no noticeable difference between the .83 and .91 spool up wise


Hellen Keller sent this?

What he said.

From what ive seen between the .83 and .91 on a 12v cummins, maybe 50rpm difference, If that. EGT's were a tad cooler. Roughly 100 degrees at WOT

 

[HobbyStock62]

FMW62 68mm .83 with s483 96mm 1.32 psi:bp is 60:75 with out a gate. going to try the .91 on it soon.

This the set up on your prerunner?

 

[Cutting-Edge Diesel]

This the set up on your prerunner?

yup

 

[kyle43335]

I would do a 62/68/91 or 62/73/91

Notice the OR in there... OP never posted hp goals. Things can vary greatly depending hp goals and wastegate setup.

dual gates dumped to the atmo, and 62/68 divided would be my poison for quick spool.

i have that very setup for my standard cab. the atmo is a billet 480/96/1.32 t6

 

[Extended Power]

Saying there wouldn't be much difference between a .83 and a .91 is like saying there would be no difference between a .70 and a .80.

Well...maybe on a Dodge, but I can tell you if you run a .70 through the hills, and then an .80....you will throw the .80 in the trash can.

Why would you buy and run such a large secondary turbine when you will never use it unless your foot is glued to the floor?

I totally agree with Shawn, run the smaller turbine on the secondary, and gate around it.

Take it from me...I have tried almost every combination of turbine/compressor there is when it comes to non vgt turbos...60,62,63,64,66,72 compressor wheels run with .58, 68,70,80 A/R's with 65,68,71,73 exhaust wheels...

Been there, done that....but, no one listens, so try it for yourself.

 

[onebadcoastie]

Saying there wouldn't be much difference between a .83 and a .91 is like saying there would be no difference between a .70 and a .80.

Well...maybe on a Dodge, but I can tell you if you run a .70 through the hills, and then an .80....you will throw the .80 in the trash can.

Why would you buy and run such a large secondary turbine when you will never use it unless your foot is glued to the floor?

I totally agree with Shawn, run the smaller turbine on the secondary, and gate around it.

Take it from me...I have tried almost every combination of turbine/compressor there is when it comes to non vgt turbos...60,62,63,64,66,72 compressor wheels run with .58, 68,70,80 A/R's with 65,68,71,73 exhaust wheels...

Been there, done that....but, no one listens, so try it for yourself.

Greg simply said the spool up differences wouldn't be noticeable so I'm curious as to what you can provide as realtime data surrounding the difference of the .83 and .91 housings with the same 68 wheel in regards to that. Not seat of the pants either, ebp ratios, what rpm difference when the turbo lit, etc. A number of guys are running different variations as without gates and they're running just well. I'm not trying to be a dick either, I'm inquisitive. Not all compound setups require a gate either.

 

[Extended Power]

...and that is why I said try it for yourself.

I don't have to prove chit to you or anyone else.

Carry on...

 

[onebadcoastie]

You're right, you don't have to but to come in and make a bold statement like that without data to support it is really just an opinion and you know what they say about those…I mean isn't that what forums are about discussion? Not coming in and implying someone's thoughts or concept was skewered without explaining it. To each his own I guess.

 

[FaSSt9602]

I think it is all up to each person and what their idea of streetable is. It is hard to quantify that. Tire size, gearing, tuning, driving habits, and your driving environment will all affect how a charger lights. Me personally, I am like Ivan. If I have to drive around at 2200rpms or more just to keep on top of a charger, it is junk. Where I drive, we have some pretty big grades and I need that boost down low because I despise billowing smoke out of the truck to light the charger on a grade.

I will admit that I have not tried either of the combinations in question, but I do have a 62/68 sitting here with both .70 open and .83 divided turbine housings that I someday intend to try, hopefully in a S478 combo...If it is a choice of a quicker spool and a gate to keep BP in check or more lag just so I don't need a gate, I'm fabbing up a gate for sure!