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Ok, as for the drivability of turbos...

It shouldn't be a problem if you pick the right turbos, and don't get stupid with the sizing and boost. Most turbo setups are developed with drag racing in mind, and that camp falls for the "bigger is better" [censored] all the time. They choose huge turbos, decrompress the motor, and use tons of boost. The turbos take a week to spool up, and kick you in the ass when they do.


My method of picking a turbo:



Choose your target horsepower.
Choose the smallest turbo that will get you there.



Most drag race guys complain that "you'll want more power later" "Boost is addictive, you'll want more", etc... They choose big [censored] turbos that could power a Kenworth, and then drive it with a tiny engine, with no response, and brag about how much power they COULD be making if they turned up the boost and ran rocket fuel.

Just set your goals, and pick the smallest turbo that will get you there. You'll have the best response and drivability that way.

With properly sized turbos, they work great on track. You should be well above the "boost threshold" in any corner. As such, boost comes on almost instantaneously, and linearly with the throttle. Where you get into trouble is with a massive turbo that doesn't spool until 5000rpm. You come out of a corner at 4000, get on it, then halfway down the straight the boost hits like a freight train. This is another thing that has led to false ideas about turbos. You often hear superchargers guys say they don't like turbolag... Again, this is caused by these guys who use turbos that are too big.

Another thing is throttle bdoies. Most of these drag race guys run these huge barn door throttles, that flow 1000hp with only 10* of opening angle. I've seen guys put these on stock engines, and then brag about how cool it is that they have a hard time not hitting the person in front of them in traffic because the throttle is so touchy. Then you combine that thing with a turbo.... the boost is like a light switch.

On mine, I can get full boost by 2400rpm. On track, I'm rarely below 4000rpm. At 4000, I've got enough exhaust gas that it can accelerate the turbo in 0.2 seconds. So, as you roll onto the throttle coming out of an apex, the boost is linear and instantaneous. Feels just like a naturally aspirated motor. Ok, almost. There is a *slight* "squishiness" to the throttle. But it's very easy to work with.

In my opinion, a good target is to double the power of the motor, with 10-15 psi. Beyond that, you're going to have to decompress the motor, and that's when you start getting into drivability problems. A low comperssion motor with no boost is a dog, and then the boost hits hard. A high compression motor will have more power when off boost, and the change in power output as boost comes isn't as abrupt.

I'm running the stock TB on mine, and refuse to change it. I'm sure I'm losing a couple peak horsepower, but I get much better throttle control. Since the air from a turbo is compressed, you don't need such a big throttle to flow the horsepower. Smaller throttles make it easier to control the power at lower rpms, and if you want a little more power up top, just blow on it a little harder... I'd bet half a psi would give you just as much top end power increase as going from a 55 to a 65mm TB.

Anyway, that's enough for now. Any questions?


2000 Rio Red I4 Cougar 200whp & 210wtq at 9psi 254whp & 276wtq with NX 35shot WRX TD04 Turbo, Cut Short Shifter, Strut Tower Bar, 17" ZN Wheels, Roush Springs, Starion Intercooler, NX 35 shot, HKS SS BOV, Full 3" exhaust,StreetFlight Chip