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If staying with Twins, Help me choose...


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Hey guys, Im trying to figure out if i want to go single BG EFR or keep the twins. If i go twins i would probably go with 2860-5 or -7. I would like high boost whp about 525ish. Traction will be the biggest limitation. 2nd is useless now and some of 3rd unless i dial back the boost with the EMS. I see most you guys have -5s. What kinda boost you seeing in like 3rd gear at certain rpms. are the -5 manageable?

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The problem I had with the -5 s is that I have boost creep. If you look at the performance curve for the -5. The optimal boost is in the range of 2 bar or 29psi which is where the boost tends to want to be. If you want to boost below the 22-23psi level you can't because the internal wastegates are unable to evacuate the charge and the boost creeps to this level. Initially I thought the stock dump pipes were the problem so replaced those and the headers with the Tomei Expreem. This very annoying because I have since then found out that this may have been corrected by simply porting the internal wastegates. But who wants to take a die grinder to a brand new set of turbos? I have not had a chance to determine if the new dump pipes have corrected the problem but for now I have left the wastegates partially open I don't want to close them again until I get it on a dyno. Street tuning is getting a little dangerous the car is just too fast. If 525 is your goal, which I think is a good one for a street driver with street tires, then the -5s are going to over shoot your mark. Like they did with me. The -7 on the other hand is closer to 1.75 bar or 25psi in the optimal range this is going to be closer to where you need to be. If you want to have complete variability from 4psi to 29psi then plan on the 2860R -5s with external wastgates and a boost controller.

 

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Oh yea your right I forgot to mention you would have to do upmounts to do the external wastegates.

 

I was talking to my mechanic today and I was unaware that she had closed back up the wastgates. I drove the car quite a bit on Sunday and the Tomei dumps appear to have fixed the problem 14psi and no more. So thats good news! But my theory about internal gates being inadequate may be moot as the creep has disappeared. But it means you would have to plan on aftermarket or custom dumps.

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Dude, don't open that can of worms right now just get it on the road and enjoy it. If you crack the motor open you are going to end up in a downward spiral of "while your at it" and before you know it you'll be posting a thread of which cams to put in it. The stock motor's power potential with bolt-on additions exceeds the power limits of the chassis in your current setup. The general consensus is that over 500hp the hp becomes unusable. When I've driven mine with boost turned up it's part fun scary and part Kelsey Grammer scary (like flip you car over in your driveway scary).

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