how much time does it take from initial boost to full boost (climb)?if you could include rpm as well?i understand if you dont want to answer.i am curious though
6870 DBB .85 A/R 3 Bolt Buick Housing-Backpressure Data
- Thread starter jmendlik
- Start date
forcefed3.8's
Buckeye Bullet
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- May 26, 2002
I am hitting peak boost from launch boost in .4 secs. This is a 4500 rpm launch at 10 psi.
20psiofevil
Active Member
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- Feb 10, 2013
What did you run to the 1/8 mile? Is that the gen2 7 blade 72mm? Killer mph btw.
toomanymodz
Well-Known Member
- Joined
- Oct 14, 2009
Has anyone tested the new Precision 6875 CEA turbo? I wonder how it compares with the 6870, especially concerning the back-pressure. I'm still running the 6466 and I'm seeing my boost fall, starting at around 5800 rpm. It falls from 22 psi down to 18 by the time I shift at 6500. Not sure where 279 cid at 22 psi is on the pressure map but I feel it's off to the right of the sweet spot. I'm thinking about going with a larger turbo, but it depends on what other items I'll have to change. I think my new goal is 140+
i think you should look at the wastegate setup.i doubt your using 85+lb min at 18psi on pure pump gas.
forcefed3.8's
Buckeye Bullet
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- May 26, 2002
Yes. 1/8 mile was 5.46@128.
that is lighting really good
forcefed3.8's
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- May 26, 2002
You probably dont have to shift at 6500. When set up properly, the 70 turbine doesnt have back pressure issues in the 3 bolt.
BEATAV8
The Engine Whisperer
- Joined
- Feb 14, 2002
Can the 66 3 bolt housing be modified similarly?
forcefed3.8's
Buckeye Bullet
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- May 26, 2002
I havent looked at a 66 turbine housing to see how they were machined.
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- May 26, 2001
To my knowledge, the 75mm CEA turbine wheel is too big to fit inside PTE's current 3-bolt .85 A/R turbine housing. Even with massive machining, it's a no dice scenario. This question was brought up when PTE first introduced the 1st Gen 75mm turbine wheel by at the time, heavy hitter 3-bolt Buick racers. This lead to the evolution of the GT4276 turbo as seen in TSL class. Anywho, enough history lesson, back to the topic at hand.
IMO, 274 - 280 CI is large for a 3-bolt "anything" turbo, in order to maintain proper efficiency and control back pressure, while making good power past 900 rwhp. Sure, some have and are doing it with the 3-bolt housing, but we learned years ago with testing the old school PT88 with the Outlawed "Cantaloupe" 3-bolt .96 turbine housing, what the limits were. I loved that turbo and if I would have kept my gray T-Type, I would have upgraded to it with other mods to make another 200 rwhp easy. But that was big boy money back then for those upgrades. That turbo's soul purpose in life was to be the biggest, baddest, class legal 3-bolt turbo in the land. And it was.... for about 8 months, until it got the ban hammer. If I could have back then, I would have bought up all of the new / old stock of those cantaloupe 3-bolt housings, as they really worked. Today's Gen 2 CEA turbine wheels would definitely fit with some fancy machine work, but alas, they are long gone or someone has them in hiding somewhere.
I personally would never have spec'd a 6466 turbo on such a large CI build. Yeah, I bet it's a light switch for spool up on a 279", but I'm also betting it's suffering a tad, as witnessed by the boost falling off up top. The compressor wheel can move some air, but only when properly matched with a better flowing turbine housing, the larger H compressor cover (although not offered on the 6466), and a high efficiency engine. What turbine housing does it currently have? On the PT6466, in order to really ring out it's potential on the large CI setup, I would have gone with either a Tangential T4 .81 for mainly street or .96 for all out with the standard 3 5/8" v-band downpipe flange and a 3.5" downpipe. From there, you get into the T4 divided inlet turbine housings, but the biggest I'd put on the PT6466 would be the 1.15 on the dbb version. I don't think the 1.32 would be very street friendly on this turbo and combo, even with dbb.
Turbine wheel tech and turbine housing tech are booming from all of the turbo makers. Unfortunately with such a low demand from the serious Buick 3-bolt racers, the "next level" Buick 3-bolt turbine housing R&D is currently asleep, off the radar and not economically viable. I sure wish PTE would dust off the plans on the Cantaloupe 3-bolt housing and bring it back. I would LOVE to see a new GEN 2 PT8385 Street Fighter with a GEN 2 Cantaloupe 3-bolt turbine housing. I'd be willing to bet it would be insane on a 274+ CI combo.
I've been following this thread closely and I'm sure I'm not the only one.
I'm very impressed with what forcefed3.8's done with the 7270 on his combo. Excellent work sir.
I'm also watching the other thread closely as well.
Carry on guys.
-Patrick-
forcefed3.8's
Buckeye Bullet
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- May 26, 2002
I have a cantaloupe housing in my stash. How much power were you able to get out of it?
turbo nasty
Turbo Dojo / MNTR
- Joined
- Jul 19, 2001
Make the Cantaloupe great again
whats the size of the intial opening?
forcefed3.8's
Buckeye Bullet
- Joined
- May 26, 2002
pics of the hole?
- Joined
- May 26, 2001
That's what I'm preaching!
Behold!
THE CANTALOUPE!
I don't remember the actual dyno numbers, but memory tells me the test engine made right at 1100. Turbo was rated at 1150 with the canteloupe 3-bolt housing , but that number was underated.
Thanks for hanging onto one and posting pics.
-Patrick-
