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Turbo AR Effect on Drive Pressure

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Old 04-17-2021 | 02:08 PM
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Originally Posted by Kfxguy
mine is an older gen 10 blade. What difference does 9 or 10 make? 9 flows more?
No idea. Mine is Billet NextGen and is also 10 blades on the turbine side.
I know the exhaust cover/housings are different because Viren specifically told me to make sure of what one I had
Old 04-17-2021 | 07:53 PM
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@rel3rd how high do you spin yours?
Old 04-17-2021 | 07:56 PM
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Hey , ramble on!! Curious if you've made a pass on pump gas ? I'm running a 6L / cast 7875 myself but limited to pump gas and W/M , at about the 600rwhp level now and afraid to push it further. Not that I could use any more on the street , just to make a hero pass LOL. Will be interested in your results , cheers
Old 04-17-2021 | 08:30 PM
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Originally Posted by Shownomercy
@rel3rd how high do you spin yours?
If its 15-16psi, (or more) its seeing about 6800 through the traps.

Originally Posted by GMCGreg
Hey , ramble on!! Curious if you've made a pass on pump gas ? I'm running a 6L / cast 7875 myself but limited to pump gas and W/M , at about the 600rwhp level now and afraid to push it further. Not that I could use any more on the street , just to make a hero pass LOL. Will be interested in your results , cheers
No, never have made a pass at all on 93. Have beat up on it pretty good, on the street, with mostly 93 unleaded, but with the ethanol station 4 miles away, I havent really even entertained the idea of testing it on regular old gasoline
Old 04-19-2021 | 11:40 PM
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[QUOTE
No, never have made a pass at all on 93. Have beat up on it pretty good, on the street, with mostly 93 unleaded,[/QUOTE]

What is the highest Boost setting and Timing on 93

Last edited by FrankieD; 04-19-2021 at 11:47 PM.
Old 04-20-2021 | 07:15 AM
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Originally Posted by FrankieD
What is the highest Boost setting and Timing on 93
Way too many variables, and every setup is different.
IMO, a lot depends on how confident you are in your tune, and the functionality of all the mechanical parts that make that tune work, to keep it "safe"...

The highest I have personally felt OK with, is 14psi and 14 degrees, but like I said, that's just goofing off on the street, so no long extended 3 gear pulls, like at a dragstrip. I'm at 18-19 degrees with 4-5psi. Zero KR. I'm sure some have ventured higher


Old 04-20-2021 | 07:39 AM
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I run 19* and 15-16psi on 93, but built motor.
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Old 04-21-2021 | 03:15 PM
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Originally Posted by Shownomercy
I run 19* and 15-16psi on 93, but built motor.
So would you say that 19* is pretty aggressive since you mentioned the motor being built?
Old 04-21-2021 | 03:49 PM
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Originally Posted by The ******
So would you say that 19* is pretty aggressive since you mentioned the motor being built?
I would say it is. I’m pretty sure I’m at 15 degree at 15 psi on 93. 19 seems pretty high. I have 9.4:1 compression btw. Maybe if he’s 8.5:1 that wouldn’t be too aggressive. I dunno.
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Old 04-21-2021 | 04:17 PM
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Originally Posted by The ******
So would you say that 19* is pretty aggressive since you mentioned the motor being built?
Nope, my apologies, I always forget that this is a primary LSX land. I have a gen 2 LTX so heads need a bit more timing compared to LSX stuff.

Timing mark on plugs was not near bend at all so felt like its a conservative number.
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Old 04-21-2021 | 04:59 PM
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Originally Posted by Kfxguy
I would say it is. I’m pretty sure I’m at 15 degree at 15 psi on 93. 19 seems pretty high. I have 9.4:1 compression btw. Maybe if he’s 8.5:1 that wouldn’t be too aggressive. I dunno.
Originally Posted by Shownomercy
Nope, my apologies, I always forget that this is a primary LSX land. I have a gen 2 LTX so heads need a bit more timing compared to LSX stuff.

Timing mark on plugs was not near bend at all so felt like its a conservative number.
Perfect, I'm just collecting data at this point.
Totally understandable with that inferior LTX combustion chamber design, totally kidding lol. ; )
There's a gent on here with a 370ci LS, A2W running 18 lbs. on pump fuel so I'd like to make as much power as possible safely on pump, goal being 800whp.
My setup is similar, fewer cubes but similar.
I also noticed rel3rd's comment about pulling timing out at peak torque, then brought it back in the upper rpm range which seems very smart for longevity.
Sorry, didn't mean to hijack the OP's thread.
Old 04-23-2021 | 09:36 PM
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Glad Im not the only one making the change from .96 to 1.25 with my t4. Most guys are auto and dont have back to back comparisons so its hard to judge the true value of the swap.In my case this is the only change and I noticed slightly better response and have dropped a pound of backpressure.Just got the turbo back from ceramic coating and should be out testing next weekend.once the track opens up again i can get mph differences from my on3 turbo vs the vsr with 1.25 housing.
Old 04-25-2021 | 02:06 AM
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I got my housing in Thursday. I didn’t realize it was divided. I don’t have pipes merged at the flange, I have one big pipe going into my turbo. This divided housing has small holes compared to the gasket, I felt like while the housing would flow better, it would be a bottleneck here. I decided to open it up instead of having a huge flat surface in the middle of exhaust flow.

before:




after:


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Old 04-25-2021 | 07:55 AM
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Makes sense , I would've done the same
Old 04-25-2021 | 08:26 AM
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Originally Posted by Kfxguy
I got my housing in Thursday. I didn’t realize it was divided. I don’t have pipes merged at the flange, I have one big pipe going into my turbo. This divided housing has small holes compared to the gasket, I felt like while the housing would flow better, it would be a bottleneck here. I decided to open it up instead of having a huge flat surface in the middle of exhaust flow.
Looks good. What are your plans for the larger 4" turbine outlet? I'm going to probably use a 4" to 3" v band adapter flange.
Old 04-25-2021 | 10:32 AM
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I bought the Monkeyfab 4-3 vband adapter. very nice piece and no compromise in flow to weld the 3inch pipe.It overall length isnt bulky
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Old 04-25-2021 | 11:14 AM
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Originally Posted by rel3rd
Looks good. What are your plans for the larger 4" turbine outlet? I'm going to probably use a 4" to 3" v band adapter flange.
so this setup is weird. While it takes a 4” v band, a 4” pipe does not slide into the turbo. The hole coming out the turbo isn’t even 4”. The step is slightly larger than 3.5”. So this is actually a good thing. (Ima post pics when I get back home)
what I did was ordered a 4” and a 3.5” v band set. I’m going to put a 3.5” v band flange in my lathe and machine it to fit inside the 4” flange. And weld it together like that. There won’t be any restriction because the 3.5” pipe is a little larger than the exit hole.
I forgot to mention, my downpipe is already 3.5”, I’ll cut the 3” section off that’s at the turbo and make it 3.5”. I had planned on building another complete exhaust out of 3.5”

Last edited by Kfxguy; 04-25-2021 at 11:31 AM.
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Old 04-26-2021 | 07:22 AM
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Although it "may" (or may not) skew my .96 versus 1.25 test, I'm going to blend the transition on mine as well.

I'm looking at one of these (pic attached) V Band adapters. That way there is no "permanent" modification having to be made to the pipes, just to make the housing work. My long term plan is to fab up a true 4" fender/nose exit downpipe, that is also equipped with a cutout. That way my quiet exhaust is still in place and used for cruising around. (See my awesome drawing attached, lol)

Short term plan is use the 4" to 3" adapter and roll with it for the foreseeable future.

.



Old 04-26-2021 | 12:26 PM
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Originally Posted by Kfxguy
I got my housing in Thursday. I didn’t realize it was divided. I don’t have pipes merged at the flange, I have one big pipe going into my turbo. This divided housing has small holes compared to the gasket, I felt like while the housing would flow better, it would be a bottleneck here. I decided to open it up instead of having a huge flat surface in the middle of exhaust flow.

before:




after:

I ran a similar turbine housing on an older TC7868 unit, I didn't bother to port the flange for resale purposes and it worked fine, no noticeable impact on spool or anything else.
Old 04-26-2021 | 11:09 PM
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In all honesty i would just get the monkey fab reducer, its a very nice piece and smooth transition.Just need to cut your exhaust and weld the 3inch onto it.Much cleaner look and 0 flow restrictions.

So i just did some street pull and logs with my new housing. The car definitely shows improvement over 5500rpm for me. Boost carries throughout and no tapering. Backpressure has dropped 2 points.Spool up seems maybe 3-500rpms later but that could be fixed with boost controller settings. It feels like this has crested me over 800whp on pump 93,a gain of 30-40whp and more in torque it comes up very strong. I can see why alot of guys suggest a t6 to start. I started to hit boost cut which never happens on my old turbo on high boost.


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