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Old 06-11-2019, 03:33 PM
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Black_Vegas
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Twin Turbo Manual Owners Only

At what RPM does the twins kick in? I donít want to be cruising down Texas highways between 70-80mph always in boost, itís extra wear on the engine. Thatís why I like the single turbo option but before I make a decision I want to get some real world info.
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Old 06-12-2019, 08:26 PM
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There is no simple answer for this. It depends on the exact turbo you get as well as the load on your car and throttle position.

I have the Fast Intentions Stage 2 Kit (TiAL HTA 2868 with Alpha cover)

Unlike a supercharger, there is no direct correlation between RPM and boost, rather it depends on exhaust volume and speed which is a function of RPM x throttle position. If you tip in throttle gently as the RPM builds and the engine is lightly loaded (i.e. in 1st gear) you can take it all the way to redline with minimal boost. Conversely, I could get full boost (6+ PSI) at under 2K RPM if I'm in 6th gear and going 40mph (don't do this, this is terrible for your motor).

So back to your real question, the simple answer is no you won't be boosting. Highway cruising for me at 70-80 results in 3.1K RPM and my boost gauge says -2 to 0 PSI ish. I don't hear the woosh of the turbos nor the blowoff valves when I let off the throttle so if there is any boost it is minimal/unnoticable and unlikely to wear your motor any more than stock. I have used oil analyses for every oil change and they show less wear than many stock motors. This is with daily driving, about 15-20K miles/year with a few track/autocross days thrown in per year. As far as fuel economy, city is about 12-13 mpg as measured by my daily driving, highway is 28-30 ish as measured on my yearly drives from WA to CA (so basically multiple entire tanks of gas on highway alone)

As far as TT kits go, both the FI and AAM twin turbo kits are great as far as my research and experience goes. I chose the FI kit because the intercooler allows you to keep the laser cruise control module if you have that. The single turbo kit from BP is a cheaper option and easier to install (no need to drop the motor, but has a major flaw: all the important bits are under your car, near/around the tranny. There is even one cross pipe that goes under your tranny. This is unavoidable for packaging reasons, however I feel like it exposes a lot of critical and expensive components to possible damage. A low scrape could crush or tear the crossover pipe or random road debris could destroy the turbo. In addition, in the rain you'll have cold water spraying up onto hot metal which will unnecessarily fatigue it. That being said, I do have a friend that has that kit and tracks it regularly and has no issues, however I don't think it's his DD. Both the twin turbo kits tuck the turbos, wastegates, and other plumbing up in the engine bay where it is all protected and everything back of there including the Y/mid pipe and transmission is essentially stock. The FI kit even has an option for you to include cats if you really want to.

Last edited by Stanford Chiu; 06-12-2019 at 08:40 PM.
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Old 06-12-2019, 10:52 PM
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Originally Posted by Stanford Chiu View Post
There is no simple answer for this. It depends on the exact turbo you get as well as the load on your car and throttle position.

I have the Fast Intentions Stage 2 Kit (TiAL HTA 2868 with Alpha cover)

Unlike a supercharger, there is no direct correlation between RPM and boost, rather it depends on exhaust volume and speed which is a function of RPM x throttle position. If you tip in throttle gently as the RPM builds and the engine is lightly loaded (i.e. in 1st gear) you can take it all the way to redline with minimal boost. Conversely, I could get full boost (6+ PSI) at under 2K RPM if I'm in 6th gear and going 40mph (don't do this, this is terrible for your motor).

So back to your real question, the simple answer is no you won't be boosting. Highway cruising for me at 70-80 results in 3.1K RPM and my boost gauge says -2 to 0 PSI ish. I don't hear the woosh of the turbos nor the blowoff valves when I let off the throttle so if there is any boost it is minimal/unnoticable and unlikely to wear your motor any more than stock. I have used oil analyses for every oil change and they show less wear than many stock motors. This is with daily driving, about 15-20K miles/year with a few track/autocross days thrown in per year. As far as fuel economy, city is about 12-13 mpg as measured by my daily driving, highway is 28-30 ish as measured on my yearly drives from WA to CA (so basically multiple entire tanks of gas on highway alone)

As far as TT kits go, both the FI and AAM twin turbo kits are great as far as my research and experience goes. I chose the FI kit because the intercooler allows you to keep the laser cruise control module if you have that. The single turbo kit from BP is a cheaper option and easier to install (no need to drop the motor, but has a major flaw: all the important bits are under your car, near/around the tranny. There is even one cross pipe that goes under your tranny. This is unavoidable for packaging reasons, however I feel like it exposes a lot of critical and expensive components to possible damage. A low scrape could crush or tear the crossover pipe or random road debris could destroy the turbo. In addition, in the rain you'll have cold water spraying up onto hot metal which will unnecessarily fatigue it. That being said, I do have a friend that has that kit and tracks it regularly and has no issues, however I don't think it's his DD. Both the twin turbo kits tuck the turbos, wastegates, and other plumbing up in the engine bay where it is all protected and everything back of there including the Y/mid pipe and transmission is essentially stock. The FI kit even has an option for you to include cats if you really want to.
Thank you Stanford, this is as real world you can get.
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Old 06-13-2019, 01:28 PM
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Seems easier to just get a Stillen SC.
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Old 06-13-2019, 02:46 PM
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Originally Posted by teahead View Post
Seems easier to just get a Stillen SC.
If OP is worried about engine longevity, then SC is definitely NOT the way to go. Going back to my original answer, superchargers are always boosting past a certain RPM, regardless of throttle position and engine load. This is more constant strain on the motor. In addition, the engine is driving the supercharger which saps 20% or so of your HP and is more load on the engine. Because of this, running the same pressure, you're going to get less WHP out of the SC kit. My TT kit runs 6-8 psi and I get 450WHP at the crank while the Stillen kit at stock puts out similar PSI but gets 380-400WHP.

That's for superchargers in general, as for the Stillen kit specifically, if you look at the design, the MAFs are relocated to just after the intakes, thus pre-compression and intercooling. Theoretically, that's the only entrance for air so it should work, but my gut tells me that measuring the air, then compressing and cooling it is going to dramatically change the properties and really the ECU doesn't have that accurate of a measurement at the end of the day. People going for big power on the Stillen kits typically relocate the MAFs to post SC:
https://www.myg37.com/forums/engine-...stions-17.html
going with an air-to-air intercooler helps a ton too so the MAFs can be post compression and intercooling. This issue might be why there's a large number of blown motors with Stillen SC kits, although this might be because there's also a large number of the kits out there since they are the most popular boost kit by far, you can decide for yourself.
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Old 06-19-2019, 11:52 PM
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Black_Vegas - I agree on the BP kit. That's why the SOHO kit has me interested
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