Need help choosing which GT2871 to take (maps included)

[WDRacing]

HAHA, me either. That dude just goes on and on and on...lol.

[C-Kwik]

Sadly, I never actually intend to write so much when I do. That one just became my excuse to take a break from homework.

HAHA, me either. That dude just goes on and on and on...lol.

That's what she said...

[Brandon93240]

Thats awesome, lol. I know how it is, sometimes bodymen will come up to me at work and ask me questions so I EXPLAIN it to them and they are like o uh yeah, ok. It makes me mad sometimes its like man u asked so I told you.

[WDRacing]

Yes sir...I get that on AIM. "Hey...how much boost can I run...yada yada" Then I drown them with info. Which is followed by, "so do I need to get my ecu tuned to run 1,000,00cc injectors"?

At that point I usually block the username

[Shift_Kouki]

Seems you forgot one of the zeros on the millionCC injector thing.

[Brandon93240]

thank god u pointed that out, we don't want misinformation around here.

[GTR PrYdE]

As I've learned that the gt28r series make such good power(at a steep price for the turbo) they really don't seem(to me) a bad choice at all, low or moderately high boost.

I'm going the sr t25 route. Point being that I can be turbo'd nowand easily buy a gt28r in the future without having to modify my whole setup.

However if I could afford a pricey build in the beginning, I would go t3 with a 50trim.

[GTR PrYdE]

Another thing was:A good friend of mine has an SR.He just fully built his head with bc 272 cams and all the other goodies, and decided to go with a bb50 trim and peakboost mani, shooting for 400whp.

Everyone on his local forum ragged on him saying the gt2871r was such a better choice that the bb50trim was going to be a lag monster on the 2.0

WD, would you have personally recommended something other than his choice for his 400whp goal?

[Brandon93240]

Sr guys think everything is laggy if it isn't a t2. A good friend of mine has my old gt32 on his sr and it spools pretty close to how it did on my ka, and makes hello topend power now. To me it was a good compromise.

[guillermoe]

/me raises a hand

A question: lets suppose we face some extra lag we are not able to allow, would things like a lighter flywheel, pulley or no-clutch fan/yes-electrical fan help to improve spooling time a bit?

[C-Kwik]

There is a difference between turbo response and boost threshold. They are intertwined to some extent, but to be clear, you should understand the difference first. Boost threshold is the engine RPM where you reach the set boost level at full throttle. Boost response is how long it takes for the turbo pressurize the intake manifold when you go from a closed-throttle position to a wide-open throttle position. This will vary with RPM and unless you're over the boost threshold, there will not be any boost response.

That said, lightening the flywheel, underdriving the crank, removing the mechanical fan, simply allows you to rev up a little quicker. This allows you to reach the boost threshold a little sooner. Boost response can be slightly increased as the same effect gets you to a higher RPM where more airflow exists sooner.

I wouldn't use this as a way to get around a turbo response issue however. Perhaps as a last resort, but chooing the right turbo will be much more effective.

[guillermoe]

Ok, there is something I dont understand well.

Boost threshold is the engine RPM where you reach the set boost level at full throttle.

By this I understand the BT is the instant when spooling is finished, we run at full boost and the wastegate starts working. Right?

If this is true, please explain me what you mean by this:

This will vary with RPM and unless you're over the boost threshold, there will not be any boost response.

How can we be in a point over the boost threshold if spooling hasnt finished, or even started, yet?

On the other hand, I understand choosing the correct turbo is the key for making your car behave as you would like. My question on the light flywheel and underdriven cranks was just to know it there would be any gain in using them. I already bought a gt28 with housing options focusing on response but, once finished, would like to test some extra options for increasing response. This is my first turbo project so I want to learn all the possibilities.

[C-Kwik]

What I mean is that if you are below the engine RPM where the boost threshold is, then you will see little or no boost at all. Lets say for example, boost threshold occurs at 3000 RPM. If you are at 1500 RPM, and you stomp the gas pedal, you won't hit full boost until you reach 3000 RPM. On the other hands, if you are at 4000 RPM and you floor it, boost will occur relatively quickly. Depending on the turbo and motor combination, it may vary, but essentially, you don't have to wait until some RPM to reach full boost.

I really wouldn't worry about spool up so much with a GT28.

[guillermoe]

Ah! I get it... lets suppose I am taking a curve so I brake and toe-heel making the RPMs not fall below 3000, in this way i will get back to fool boost relatively instantly as opposed as if I let the RPMs fall completly.

It will take hours and hours of practice to learn these "tricks" with turbos... it will be fun

[C-Kwik]

Yeah. you definitely get it now. However, letting a NA motor fall below 3000 RPM will likely result in poor wheel torque. Point is keeping the RPM's high is still very bneneficial regardless of the type of motor you are using. It tends to get exaggerated in turbo motors though.