Steeve_Civic

Is there any dyno results?

I ask myself about switching from my 6766 to 6870 gen2?

Thks

Pumpking.

If you're racing class races, why bump from a 67 to a 68, and A) get booted out of true street, or B) lose the weight break that you'd get vs doing 67+?

68 is no mans land since it doesnt fit TS, yet leaves power on the table vs a 72mm as well as have to run the weight of a 72 now.

Casey

iTrader: (5)

Hes in France. I doubt he cares. Not that I have any more useful input.

Steeve_Civic

Yes, do not have any class races here. I want around 100hp more than my 6766 and looking for good spool and power.
You advise to switch to 7275?

mint

iTrader: (1)

Red 6870 T4 .81 H cover E98
Blue 6766 T4 .96 H cover E98

Yes the 6766 was 2psi less then tapering to 1.5psi difference but this was the closest I have.

PTE will cut down the inducer down to make it true street legal if needed.

DC-2uned

Thanks for the sheet Mint, always good to see hard evidence(even if it's 1-2psi different)

That .81AR turbine housing really makes a difference. It still seems to spool the same/slightly better despite 1mm bigger Compressor Inducer and 4mm bigger Turbine Exducer while, as to be expected, making more power the whole way up. This agrees with my theory in turbo sizing...I always thought when upgrading that it's better to go a size up on wheels and run a smaller size AR housing, than trying to squeeze out more power with same wheels and larger ar housing. It usually allows for substantially more power with the same(and occasionally better) spool as opposed to worse spool and only slightly more power.

For example(for arguments sake, I know diff setups react differently): If you have a gt3071r with .82 housing and want a little more top end power, I'd rather upgrade to a gt3076r with a .63 housing(or really the TS .78 which spools like a .48 housing but flows what a .63 does. But, that's kind've apples to oranges) than a gt3071r with a 1.06. Yes, it's cheaper to buy a turbine housing than a new core but I'm talking "ideal wise" not "$ wise".

(Waiting for Shodan or other turbo experts to come poke holes in my theory lol)

Do you have any pulls starting at lower than 4000rpm to really see a spool comparison?

Also, I know it's probably a drag car so street driving and transient response are probably irrelevant but, have you done an street driving in each setup to test the difference in transient response for curiosity's sake?

DC-2uned

Here is a thread of someone making 920whp with a 6870 on a built k20 in a MR2: https://honda-tech.com/forced-induct...0-mr2-3234040/

kr3w108

The 6766 is a really nice turbo, i have thought about the 6870 also. I do not class race either but it has crossed my mind, that if i were to class race then i would need more weight in the car.... the 100 gain is pretty much equaled out buy the heavier weight....

mint

iTrader: (1)

No I have not drove the car on the street I just race it.

I went with the .81 A/R housing because I wanted to try to keep a similar power band just more power it worked out. The compressor wheel is 1mm bigger inducer and 5.5mm bigger exducer and the exhaust wheel is 4.75mm bigger inducer and 4mm bigger exducer. since it its bigger and a new designed compressor (7 Blade) wheel It had to spool later with the same A/R from the 6766 I had.

I'd like to try the .96 A/R to see how much it would bring the back pressure down to see if I could get more boost out of it with out changing my 7psi waste gate spring.

kr3w108

How much boost is that? lol

mint

iTrader: (1)

Look at the graph its shows whp and boost.

kr3w108

I see what you were talking about now. lol i was looking at the chart wrong. thought it was wtq. The 6766 didnt do all that bad. for the boost lvl. I made 761 @30 psi 1.15 hotside. The 6870 is really nice. I like the gains you made through out the power band. The turbo deff makes for a great upgrade, but the price is almost doulble.

1lowek2007

I made 920+ HP on the 6870 spinning @ 36lbs of boost. That was also before we added 2 more * of timing. It made about 75hp more then the 6766 i had at same boost levels above 30lbs. And actually came in sooner then the 6766 did, although my 6766 was JB. This was on my K20 with mild cams dynoing on 26" 275 radials.
https://youtu.be/TsNvUosd2Z0

Steeve_Civic

Very Nice, which AR are you running?

Steeve_Civic

Is the 6870 Much bigger and need more space under the hood?

1lowek2007

I run the 1.0 twin scroll

Physically the same size as a 6766

Steeve_Civic

Thks

kr3w108

If the inducer was to be trimmed to make it a 67mm , how much do you think that would affect the performance? I dont see 1mm gonna affect all that much.... All that they would trim would be the leading edge correct?