Which is the better AR...68 or .81?
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Which is the better AR...68 or .81? 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.
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.
Last edited by Wicked69; Dec 2, 2013 at 01:59 PM.
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
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
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. 
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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.
Thanks for the input.
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From: hugo okla.
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 
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
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
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From: hugo okla.
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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
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
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
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
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.
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.
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.
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.
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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.