Why all the "big" turbo kits @ low boost

[Dipstik-sportech]

Higher boost threshold is traction control

The Frozen North

[Sportsguy83]

Originally Posted by qtwre

I love reading you guys talk about these technical topics and I lurk much more than I post.

One thing that is bothering me a bit in this thread is that some people are talking about the slower ramp up in power of a big turbo like it's a feature. I understand that it's better for the drivetrain not to be overcome with power too quickly, but we do have throttles we can modulate and having the option to use power lower in the powerband is arguably better than not.

Other than that, I agree with everything else being said about the benefits of a bigger turbo.

At the end of the day its a "different strokes for different folks" type of deal.

Some people will love the instant torque hit and will be willing to compromise a turbo that will fall flat on its face at the end.

Others will hate that, and will want a turbo that progressively makes more power and keeps pulling pulling and pulling up to redline.

The main difference between both aside from feeling, is that one is already maxed out while the other has room from improvement.

I have owned both (on this car) and let's just say I am happier with my current (room for improvement) setup.

[mrk1]

Originally Posted by qtwre

I love reading you guys talk about these technical topics and I lurk much more than I post.

One thing that is bothering me a bit in this thread is that some people are talking about the slower ramp up in power of a big turbo like it's a feature. I understand that it's better for the drivetrain not to be overcome with power too quickly, but we do have throttles we can modulate and having the option to use power lower in the powerband is arguably better than not.

Other than that, I agree with everything else being said about the benefits of a bigger turbo.

yes your foot is the final determining factor but wot is the common factor that will ultimately compare turbos, especially very different ones like large or small.

but @Sportsguy83 hit it on the head, different strokes. Just like the SC vs TC discussions.

[Ironsquid]

Originally Posted by Sportsguy83

I will soon

You cheeky

[Dephective]

Small turbos become hair dryers while trying to maintain constant PSI up to 7k. Virtually useless past 5k. Lower BAT's at the same PSI will yield more power. Less heat means less wear as well.

As far as drivetrain, yes there are a bunch of guys running an impressive amount of power on stock internals, quite a lot actually, but they are one det event away from having $5k pour out of their motor. Our internals aren't that great really, it's really the Direct Injection that is the saving grace, due to the proper cooling of the cylinder. One of most important things to consider when trying to prevent detonation, aside from a PROPER tune, is reducing BAT's. That hot air going into the chamber is not good, and relying on a knock sensor to prevent the big bang is like Russian Roulette . I'd rather have a proper turbo for my application. Seems to be the 3076 is the perfect size for 95% of applications.

Edit: assuming you aren't running E85, because then of course your headroom on stock internals is far greater. Man that stuff is really knock resistant.

[cdrazic93]

Originally Posted by Dephective

Edit: assuming you aren't running E85, because then of course your headroom on stock internals is far greater. Man that stuff is really knock resistant.

Even if you run E85, the 3076 is still a decent turbo to fit the needs of the added knock resistence.

[mrk1]

I dont even have e85 here

[Sportsguy83]

Originally Posted by mrk1

I dont even have e85 here

Pls pls pls pls get this!!

http://www.carscoops.com/2011/02/bre...from-food.html

[Ironsquid]

Originally Posted by Sportsguy83

Pls pls pls pls get this!!

http://www.carscoops.com/2011/02/bre...from-food.html

$30k nothanks, that's like 6 built motors down the road, lol

[mrk1]

wow thats a lot of money. A few years ago I was in another shop and one of the others guys in the building was secretly brewing very very large quantities of bio diesel. The land lord, fire department, town, and insurance company was not very pleased with him.

[Reaper]

Using a larger turbo in relation to its VE is easier to control knock in high comp motors. It usually comes at the expense of severely increased lag. Higher compression ratios help combat this lag but its always been a trade off. In the case of a DI motor we can get away with higher CR than usual and a consequently larger turbo without making it "laggy". This also prevents us from choking this motor with backpressure at lower rpms where's its not a lot of relative power anyway.
As far as going to a larger turbo because of a smoother curve that's nonsense and can be tuned. Cam, ignition, DBW and electronic boost control all can help that.
Remember fia rally rules were 34mm restrictors and lots of hp! Granted those were still kind of on/off even with all the tricks.

[Ironsquid]

Originally Posted by Reaper

As far as going to a larger turbo because of a smoother curve that's nonsense and can be tuned. Cam, ignition, DBW and electronic boost control all can help that.

It's not nonsense, it's science. Larger turbos spool more linearly than smaller ones do, given the same exhaust volume and target MAP. The reason for this is because the curve for a larger turbo is higher. Doesn't mean it's unbearably laggy which is the main "incorrect" assumption by people who say big turbos suck. You have no evidence to prove otherwise besides the napkin-math you find on nasioc or other less than 12.5 compression ratio car forums.

Yes, you can always take power away from a smaller turbo like you said with timing/ebc. It's not for me, I like efficiency, which is the entire point of the turbocharger, efficiency.

I'm fine with people making their own choices, but don't give out your opinions as facts. So before you go saying "severely" increases lag, I invite you to take a ride in my car.

[Reaper]

Originally Posted by Ironsquid

It's not nonsense, it's science. Larger turbos spool more linearly than smaller ones do, given the same exhaust volume and target MAP. The reason for this is because the curve for a larger turbo is higher. Doesn't mean it's unbearably laggy which is the main "incorrect" assumption by people who say big turbos suck. You have no evidence to prove otherwise besides the napkin-math you find on nasioc or other less than 12.5 compression ratio car forums.

Yes, you can always take power away from a smaller turbo like you said with timing/ebc. It's not for me, I like efficiency, which is the entire point of the turbocharger, efficiency.

I'm fine with people making their own choices, but don't give out your opinions as facts. So before you go saying "severely" increases lag, I invite you to take a ride in my car.

Slow your roll I'm not calling your car laggy. I'm saying going to a larger turbo for the SOLE purpose of slowing the onset of power is silly and can be handled otherways.

[Ironsquid]

Originally Posted by Reaper

Slow your roll I'm not calling your car laggy. I'm saying going to a larger turbo for the SOLE purpose of slowing the onset of power is silly and can be handled otherways.

Nobody here said it's the SOLE purpose.