wicked_sten

I'm currently running an On 3 76 on an lq4, (completely stock besides for springs and pushrods tuned on e85 non IC) into a powerglide with a 3k stall in a tube chassis rock buggy. I've been fighting some back pressure issues with the tiny 65mm turbine and want to try the 7876 on3. I'm afraid it won't spool as quickly and i absolutely love how responsive this thing is now. Did anybody that switched notice any significant lag?

Forcefed86

iTrader: (4)

Whats a back pressure issue consist of?

Kill'n yourself with that baby turbo. Id go for the VSracing 77/83 T4.

http://www.vsracing.net/catalog/prod...6c8e74eaab98d0

MontecarloDrag

iTrader: (3)

We upgraded from the 76 to the 78 and the lag was noticeable higher but not by a lot.
However, the car now runs much stronger than before. it is a better turbo for sure.

wicked_sten

I had issues with drive pressure blowing the WG open before any boost was built with a 10 psi spring, this mostly happened in low rpm/high load situations. I remedied that by installing a MUCH heavier spring in the gate, but this creates a very small tuning window for the boost controller, and feels like a bandaid fix for something that could be easily remedied with a more appropriately sized hot side. I don't think an 83mm turbine would spool quick enough for my application.
thanks for the reply, what kind of converter stall are you running?

Forcefed86

iTrader: (4)

What boost level do you run? Sounds like the control method may be off, what are you using? how is it plumbed?

The more drive pressure have the easier boost control should be. A 10 pound isn't going to give to 10lbs of boost unless oyu have 1:1 BP ratios. There are many factors involved. What size spring did you install? What size gate?

A 6.0 needs a larger turbo. You're compressor isn't the problem. The exh wheel and housing are the restriction.

wicked_sten

I realize that the restriction is the exhaust wheel, hence the purpose of this thread and wanting to go from a 76/65 to the 78/76. My only question is the difference in lag/spool time (if any) between the on3 76 and 78, from those that have ran both turbos on the same vehicle/setup. thanks

denmah

iTrader: (2)

i havent gotten to do an apples to apples comparison but used my first 7875 on the colorado build and im kinda blown away by how good my numbers are and how fast it makes boost

i can make 7lbs at 2000 rpm
and i have a 3k converter so its instant

also i did 500whp at 6psi unlocked
and 610 at 10psi unlocked lifting early (fuel delivery issues)

wicked_sten

Thanks for the reply, you've answered my question pretty well. I need to often lift and get back on it to maintain control on an obstacle such as this, and why spool time is critical.

Tjabo

Is anyone on the forum using this turbo? Very interesting...

I've heard there can be a leverage advantage with the larger diameter turbine wheel, so I'm a bit confused. Lol I ran a Precision 6265 on my old 2.0L 4-banger when most people were running 6262s, or even smaller turbines on similar sized engines, and my setup was surprisingly responsive. It made me think there might be something to the leverage concept.