Sarg

iTrader: (6)

Just trying to figure out the converter I plan on using and I was wondering if anyone has any first hand experience with either of these set ups on the street? I have seen a couple dyno graphs, but in my experience most cars will spool a good bit slower on the dyno than on the street.

ninetres

iTrader: (35)

Sounds like WAY more turbo than I would want on a street car, even with a 5.7. On a street car I would want that sucker to come alive as soon as I stand on the throttle, which I doubt a 5.3 would be able to do with either of those snails.

Sarg

iTrader: (6)

I have seen twin 76mm on a 5.3 hit peak torque at around 5000 and 25 psi on the dyno. I would expect 4-500 rpm better could be achieved on the street, especially if only going to 15-18 psi.

70mm should be significantly faster still.

Fbodyjunkie06

iTrader: (10)

Just make sure you get a a/r that is nice and tight, no more than .8x for quick spool, something in the .6x range would give those turbo's a chance to spool down low. I guess it also depends on which 70mm or 76mm turbo's you were looking at running.

Sarg

iTrader: (6)

I was actually looking at .68 ar turbine housing, although the only one I have seen on a dyno was 76mm and larger turbine ar.

831jd

iTrader: (3)

A twin on3 76mm .68ar should spool good with the right cam and converter e85 on a 5.3 to make 1000wrhp before 25psi correct?

jridenour31

What is with everybody wanting twin 76's for 1000hp lately?

LilJohn

When using the on3/ magnum stuff it just works. I wouldnt suggest going that big with new tech stuff though.

Jon at DB Rods gets a 5.3 to go positive map before 3 and full boost before 4 with twin netics T76's... not tcs....

Hes got this combo ironed very well.

831jd

iTrader: (3)

How much comp would you need then?

HexenLord

No kidding. I've seen some billet 76s making close to 1000rwp alone. The old NHRA sport compact class HOT ROD had a maximum turbo size of 76mm and some of those cars were making over 1000whp on methanol in a 4 cylinder running high 7s low 8s.

Twin 66mm turbos would break 1000whp and spool very quickly for the street
No point in throwing on large turbos and killing spool and street manners when it can be done with much less.

jridenour31

It works but is there really any reason to run that large a compressor with the tiny turbine wheels in those? Seems like even a pair of cheap 70's should make at least 1100.

Black98s10

With you thinking of twin 70's or 76's for a street setup, it makes me feel better about going with twin 67's on my 5.3L. Would you be running a small shot of spray, or trans brake, to help spool them, when you do go, to the track?

ren987

iTrader: (4)

I would just go with the 70's as 76's will be a waste with such a small turbine wheel. I have two on3 76mm's on my 5.7 and should have gone with the 70's to free up some unnecessary rotational mass on the comp wheel.

allout06

iTrader: (11)

FWIW, i bought 2 Turbonetics 66/65's on a .68 A/R for a 390ci.... Talked with jon at huron speed. He said they will spool very fast and would be a blast on the street.

Sarg

iTrader: (6)

I believe John has it dead on. I have seen 66mm Borg Warner twins make over 1200 hp before at the wheels. I would hazard to guess that On3 70mm would have a hard time matching it. I am sure it comes down to wheel design and all that.

knuts82

I guess my question would be what cam would make it work best. Say for twin 76mm on3 turbos. Duration? Lift? Overlap? Reverse Grind? ?????

LilJohn

These On3's and Magnums are old aero technology. You NEED that much compressor to move the kind of air mass being discussed. The turbine/compressor relationship being outta whack comes from when those wheel aero's were "cutting edge". The turbines (o,p,q trims) were further along than the compressors.... soooo when you matched up the mass flows to get a balanced unit.... you got something like the Q trim 76mm. Now...today. compressor wheel aero has progressed expotentially and we have turbos like the S366 where its got a 66mm inducer compressor and a 74 mm turbine.... See how that works? Lol

So today a borg s366 will stomp a mudhole in an on3 76's ***. Had Holdener used those on the big bang theory motor.... he woulda made 1550-1600 if it woulda held together. 10mm smaller inducers moving 30 more lb/min of air.... aint progress grand?

But the on3's are cheap and proven durable. You just have to adjust your sizing to fit your needs.

Just like with frozen boost/ebay intercoolers. As long as you buy it sized 30-40% more than what you actually make...your good.

To hell with worrying about what size the compressor is. Worry about how much mass it moves.

Jons IDC on Redsled was 82% at 26 psi with the 76 magnums.... it was 98% at 20 with the turbonetics..... what does that tell you?

LilJohn

Your whole post is based on the assumption equal impeller size means equal mass flow. Nothing could be further from the truth.

LilJohn

Theres no other way for this to sound but *******'ish... so please dont take it that way...

Best cam will be the one designed for the combination as a whole.

You just gave me a pair of turbos... and im assuming your meaning on a 5.3 application...

I can say with certainty it wont be a reverse grind. Lol.... unless you wanna put em on a 427.....

Generally... twin cams can be made much more aggressive on the exhaust events. This does normally take away torque below peak... BUT with energy diverted to the turbine by opening the exhaust valve early without fear of choking the turbine.... we get a very aggressive boost curve that more than makes up for the torque we lost N/A from opening it so early.

The upper limit for your overlap goes up too. It will tolerate more... just depends on other parameters how much you use.

Converters for twins can normally be a tick tighter than for a bigger single capable of the same power.

Jon's combo uses a stock 5.3 shortblock with an LS9 cam installed 2 degrees advanced. 317 heads and a Holley Hi ram. Its a 4000 pound truck with a 390/45/15 tire,3.42 gear and an 80E. It flat hauls the mail.

He ordered a cam from me today.... back to back dyno testing will be done and ill post the cam specs and results once Jon gets the time to do this.

jridenour31

Wow, didn't realize those compressors were that bad lol.