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Discussion Starter · #1 · (Edited)
Engine and cam in my sig. Clay Forrester is going to do a twin front mount setup for me as soon as my engine gets back from the machine shop.

My goal is low to mid 9's on E85 through a TH400 in a 3700lb car with the potential to go faster with a better block and heads down the road. I don't class race, just do test and tune. I'm leaning toward twin TC78's with .96 exhaust housings so I have room to grow. But I don't want it to be a dog because I put too large of turbo on.
 

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Discussion Starter · #3 ·
I would like the power to carry to 7500rpm. I wasn't sure if the .81 housings would do it. Since they are pretty easy to swap I may start with them though.
 

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Discussion Starter · #6 · (Edited)
Can't wait to see it done man, going to be a beast!
You going to race any AFSC or AZ Grudge races?

-Chris
I'll need to look at the rules, but I may race for fun.

My cam is from Mark at Bullet. It's a 250/254 .625/.600 on a 115. Getting degreed at 110. Super Victor manifold fully ported.

My head is going to explode soon, lol. I've been looking at a few different turbos all in the same price range and HP level they support. What do you guys think of these:

Precision 62 or 67 Billet

TC 67,70,72(F1 turbine wheel)

Borg s300 66(68mm, 71mm, or 73mm turbine wheel)

AGP Delta 75(62mm billet compressor and p-trim turbine)

All of the above turbos are rated for 750-850hp each. I'm just not sure if I should go as big as the TC76.
 

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Discussion Starter · #8 ·
Since they are all the same price, it's pretty much a question of why shouldn't I do the TC76/78? Will they be ok at 10-12 psi for street driving? I don't need it set on kill for going to work, lol.
 

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I'm going to have to chime in on this one. I'm looking for the same numbers that you are. I have talked to several companies that sell all models. I've heard a strong argument for the Precision billet 67mm turbos over the TC series 76/78. Chris at Custom Racing Turbos and Josh at Kentucky Turbo are sold on going with the billet models. I'll be purchasing the turbos last (warranty reasons) so I still have some time before I have to decide. You may want to do more research before you pull the trigger. I think it's a great question.
 

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Discussion Starter · #10 ·
I'm just worried the billet Precision turbos are just a flavor of the month kind of turbo. Plus I've read of people having issues with them. Turbonetics has a pretty kick was warranty also. I've left a message with Reed at Supernatural Turbo to see what he says on the subject.
 

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The billet precision units are nice nice pieces but DAMN that's alotta coin!!! There's one thing to consider with the TC stuff and that's compressor wheel size to turbine size relationship. Which F1 wheel are the putting with the 76 comp wheel? I'm figuring it's the 68. 76-68 is pushing that relationship a bit much IMHO. I like the 72/68 alot better. Do you really NEED 2000 horsepower worth of air? If you get em too big they will surge on you on the street.

The F1 turbine wheel is an awesome wheel and will support more cubes/hp/rpm than an equally sized precision or Garrett wheel will before it hits it's choke point. The reason that is important information is because that wheel will allow you to run a tighter A/R housing giving better response and probably making the car more enjoyable on the street.

The 76mm compressor wheel is too big IMHO. That is right at 2000 hp worth of air. I think a 68 or 70 would be perfect, and the 72's would be a tad big but useable if you are gonna try and make 1400 to the tires one day.

Final vote is for the turbonetics TC70 with a F1-68 turbine wheel and a .81 housing.
 

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The billet precision units are nice nice pieces but DAMN that's alotta coin!!! There's one thing to consider with the TC stuff and that's compressor wheel size to turbine size relationship. Which F1 wheel are the putting with the 76 comp wheel? I'm figuring it's the 68. 76-68 is pushing that relationship a bit much IMHO. I like the 72/68 alot better. Do you really NEED 2000 horsepower worth of air? If you get em too big they will surge on you on the street.

The F1 turbine wheel is an awesome wheel and will support more cubes/hp/rpm than an equally sized precision or Garrett wheel will before it hits it's choke point. The reason that is important information is because that wheel will allow you to run a tighter A/R housing giving better response and probably making the car more enjoyable on the street.

The 76mm compressor wheel is too big IMHO. That is right at 2000 hp worth of air. I think a 68 or 70 would be perfect, and the 72's would be a tad big but useable if you are gonna try and make 1400 to the tires one day.

Final vote is for the turbonetics TC70 with a F1-68 turbine wheel and a .81 housing.
The Precision billet 67mm turbos are the same price as the TC78's. They can be purchased for right at 1K a piece through Chris at CRT. One of my biggest concerns is the warranty history through Precision. I have heard more than one time, they make every excuse other than honoring it. I have also heard it's basically a no questions asked deal with Turbonetics. I have a great guy helping me out with my project. He is sold on the TC's and their warranty. At this point now, if I get PC 67mm turbos and it doesn't run like it should, I can hear him saying already, " I told you so".
 

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Discussion Starter · #13 ·
I'll most likely go with the TC just because of the warranty. Plus I found a place that will do $899 shipped on them. That saves some coin over the Precision. I think the 72's would be the best fit for me with the ability to go higher later when I build my 4.125 bore, 3.622 stroke engine in 2012. Gotta do it before the world ends right? Lol.
 

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Plot the compressor map vs engine consumption for your 403ci at 7400rpm and look at the eff difference in a 72 and a 76. Then make your decision.

$899 for a journal bearing or ceramic ball bearing TC?
 

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Discussion Starter · #15 ·
Journal bearing TC is $899. I'm on my phone at work, so I don't know if I can get to the consumption charts on Forced Inductions website. I will try though.
 

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Discussion Starter · #16 · (Edited)
The chart on Forced Inductions only went to 6800rpm. Just doing some extrapolation I figure I will need 125-130 lbm at 20psi for the 403. Using the calculation of lbm x 10.86=HP that means a TC67 is 74lbm, TC70 is 78lbm, TC72 is 83, and TC76 is 92lbm. Based on theory ratings of 800, 850, 900, and 1000 HP respectively.
 

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Discussion Starter · #17 ·
Here are some compressor maps I found. How do I read these things? I want to run 10-12psi on the street and 20psi at the track. 12 psi will need about 90lbm at 7500rpm and 20 psi about 130lbm.



 

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(atmos p + gage P)/atmos p = PR So plot your points. EX: 20psi = (14.7 + 20) / 14.7 = 2.36 PR

2.36 and 65lbs (130/2 for 2 turbos) will plot on the 76 map at 75% eff....great for cooler discharge temps. And you eill have room to grow because 20psi will not be the limit....never is.

Now plot the rest and you can compare.
 

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Discussion Starter · #19 ·
Awesome! Thanks.
 

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Discussion Starter · #20 ·
Soon I will have twin ceramic ball bearing TC76's with the 68mm exhaust wheel and .81 AR exhaust housings courtesy of onfire.
 
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