6870 Boost ?
- Thread starter 434nova
- Start date
I had that Turbo in the 3 bolt S cover on my stock stroke 4.1 & it didn’t make anymore power than my 6766 cea jornal bearing H cover & it didn’t spool as fast even though it was ball bearing. Both turbos were ran with the same 18 Blade ptc & both turbos had the same .85 precision housing. The 6870 only started to make more noticeable power at 28 to 33 lbs. of boost . Under 28 I liked my 6766 cea way better all around use . The 6870 liked to be launched at 5-7 psi and the boost would ramp in fast all the way to wherever I had the boost set . But with the 6766 cea I could just flat paddle the car or whatever and it never felt lazy . To make the 6870 fun & snappy I added a little more timing in first gear only. Doing that made me like the Turbo more. If you’re not gonna run 28 plus psi boost that is not the Turbo I would recommend to use in the Buick 3 bolt housing. I don’t know how it performs in a 4 bolt setup. Hopefully this was some help to you . I’m no xpert. That was my personal experience.
dank GN
BlackArts Automotive (661)993-8277
- Joined
- Jan 11, 2009
I’m runing a 7168 from comp with a 3 bolt housing with a .85 A/R . I think it would be different for every single motor for the most part . It depends on what converter you are using plus what cam is in there plus how it’s tuned . I’m runing it on a 281CID so it spools super fast . But agian no one can tell you how it’s going to perform on your car with your exact combo with out just slapping it on and tuning your motor for it . I think you will like it as it’s a decent size turbo that you can grow into . If down the road a year you make some changes to your combo the turbo will just perform better and better IMO . Good luck bud just keep spoolin 
marleyskater420
still needs to learn
- Joined
- Aug 14, 2004
The same turbo on 3 different motors is going to spool at 3 different RPM ranges, unless all of them have the same exact setup..
The head flow, camshaft lobe profile (ramp rate, etc), and the torque converter specs are going to be the most influential aspects to the spooling of the turbo. Especially the latter 2.
I have the 6870 dbb "H" cover with .85AR 3 bolt on my 250 CU stroker motor with PTC 17 blade and it spools fast!
I also run E85 and GN1 Heads with 218/224 Roller Cam. This turbo makes more power at less boost than my 6466 , and spools just as fast IMO. I like it!
I have yet to hammer it with high boost (only seen 21lbs) but can spin my motor to 6200 easy but like to keep it at 5800...It's a handful at 21lbs on the street!
No complaints here!
I also run E85 and GN1 Heads with 218/224 Roller Cam. This turbo makes more power at less boost than my 6466 , and spools just as fast IMO. I like it!
I have yet to hammer it with high boost (only seen 21lbs) but can spin my motor to 6200 easy but like to keep it at 5800...It's a handful at 21lbs on the street!
No complaints here!
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I would love to hear some actual math on your question.I will go first
hpc billet bb 69mm bringing in initial boost at 2700 rpm and from initial boost reaching 37psi in .5 of a second.
ttypewhite
Well-Known Member
- Joined
- Oct 1, 2001
The 6870 is a true street cars dream turbo. The turbo spools instantly and makes good power. This video below is me driving my Dad's heavyweight GN at the track. Notice how fast it hits 8psi on the transbrake, and running 28psi out the back door with a Dusty spec'd PTC converter. This is a 4 bolt unit with a 1.00A/R exh housing too...
434nova
Active Member
- Joined
- Sep 30, 2013
Whats the engine combo?
