Wicked69

Just curious here. I am running the ON3 Twin 70's with .68 AR. I have a 370, 3700lb car. Cam that peaks around 7k. I have the PRo Flo Intake, Stock 799 Heads, 3.73 gears (new) PTC3400, PG. I want to make more power. I have had no issues with my 70's but as cheap as these are if the .81 AR would work better I would get another set. I got the .68 AR originally because I had a 5.3.

My car will boost higher than 20lbs but didn't pick up any more power after 20. Figured the .81 AR and shifting at 7k would make more power. Yes or No? BTW I have forged internals and stock crank and 8.4 compression

The ON3's don't have compressor maps and I have limited knowledge on which AR on the exhaust side would be better. So which would be better and why?

Thanks.

rotary1307cc

iTrader: (5)

Bigger the better if you can still spool as desired which shouldn't be a problem

Before buying anything I would tap and see what drive pressure is like

As the turbine/housing hits its mass flow choke area the drive ratio will go crazy

ls1_chevelle

iTrader: (9)

.81 no doubt

Wicked69

Why is the .81 better? Is it because of the size of the engine? How will the .81 differ over the .68 specifically?

Is it because it will allow me to run a higher rpm?

Wicked69

Uhhh. Not sure where I got .81 It only comes in .68 which is what I have or a 1.0 Would the 1.0 be too much in a twin set up? I don't want to spin this past 7200. If that matters.

Boo"SS"t

iTrader: (2)

Generally, a .81a/r will net you more power on top (in the higher rpm) in exchange for boost response, but your new 370c.i. will help negate that and having an auto won't really matter much in your case, I would also think that it would be a better match with your new (higher rpm) cam. -Just my .02 cents.

Wicked69

Okay that's what I was thinking but obviously wasn't sure how it works. I got the .68's when I had a used small cam and a 5.3. Now I have more cubes and a custom cam that peaks just shy of 7k so can spin it to 7200. Building boost is not an issue. I can build 15lbs easily. Won't be able to leave with that much anymore anyways because of the steeper gears.

Thanks for the input.

IMPATIENT 1

Talk to chad wicked.he upgraded mine from .68 to .81 .they do sell them with several unlisted ar sizes.call them not buy offa ebay

HexenLord

Switching from a .68 to .81 will help, but won't make a significant difference. That's not really a big size increase. What size turbine wheel do those have on them?

IMPATIENT 1

65 but i need to pull a housing a check both ends of it.me and chad figured my lil 5.3 wld need .81 for how hi i rev my dragboat.a s480 with 1.1 83mm turbine choked on it this past summer so i switched to on3 70's.s480 choked at 6900 3:1

rotary1307cc

iTrader: (5)

You said over 20psi it doesn't pick up. Obviously u are at the limit of the turbine, compressor or both

Unless they are an absolute dog **** compressor, twin 70s ain't done there

Money it being on those ptrim wannabe turbines. Which is why you should measure drive pressure and it will be a dead giveaway with what is happening

Bigger housing would do some but nothing like if you bolted something like a pair of plain jane s366 on with the 73mm turbine

It would blow your mind

00Wildcat

I'm with Rotary. Silver 5.3 S-10 has been 8.54 with out of the box 366's. how many times do you want to change them?

IMPATIENT 1

Wicked is still running his first set of 70's as far as i know.be cheaper to just call chad and buy new .81 turbine housings but as cheap as the turbs are why not buy another set? Use the older set for another build,sell em or keep em for spares.until you have a on3 turb in your hands its hard to knock their quality.i was pleasantly surprised with them but water is too cold to run em, itll be late feb before i see how well they work.as i posted i sold my single small turbine s480 setup to try these twins.if wicked has had such luck with them on a daily driver, i figured what hell ill put em thru 35-40hrs of runnin time a boating season wont be squat.ill be asking 500hp from each on3 70 which i think isnt askin much and shld keep turbo speed relatively low.my deal isnt like a car tho, boats are torture on engines cuz we hit our full load quik and stay there the whole 1000ft or 1/4mile pass if the on3's fail ill report it here no problem.i just dont see myself using turbos worth twice the engine, doesnt compute to this cheap okie

rotary1307cc

iTrader: (5)

You realize the price of a 366 right?

Its not even worth it

qqwqeqwrqwqtq

Agree with all of the above.

rotary1307cc

iTrader: (5)

For his trap and weight he is around 1k flywheel. For twin 70s maxed out that is laughable

The turbine is junk in those things. Housing swap or not it is not going to do crap


A pair of 366s can be had for cheap. His mind would be blown if he bolted them on

They are all of 1500hp worth of compressor and have the turbine capacity behind it to back that

71 chevy

iTrader: (18)

wicked69,

what is the iat at 20 psi? that will be a clue as to the efficiency of the compressor and if you are off the map(assuming no intercooler of course)

then,
what is the back pressure? you wanna know if the turbine is expelling exhaust efficiently. you can use the fuel pressure circuit on the holley.

norotor7

iTrader: (2)

It's $900 more to run the S366's over the On3's.

I wonder what the spool difference and power curve look like between the On3 and S366.

I have On3 70's I'm going to try on a 6 liter in the spring, and i'm thinking about changing to S366's if I don't like the On3's.

Wicked69

Sorry about just getting back on here. My IAT's are barely over a 100 degrees. In the very hottest part of the summer they might hit 150. I am sure the s366 would work better. I don't doubt it. However, my issue is not to make the car as fast as possible, but to make it fast as possible within a decent budget. I have less than $3500 in to my entire twin turbo set up and I am happy with what it has run. I would like to try and hit my goal of 5.70's with the ON3's first. If I am not able to do that then I will probably get a set of 366's. It's just hard to beat $300 for a turbo that runs that damn good. I love my ON3's and would like to hit my goal with those turbos first.

Wicked69

When I get my transmission back fixed and back in I will check back pressure and let you know 71.