Turbo Kits: Rational boost threshold yet?

[industrial]

Originally Posted by OrbitalEllipses

Transient response outweighs any criticism of too little top end.

Many people will end up with too large turbos and realize that while they make 400+ peak who their car sucks to drive anywhere except the track (or unsafe highway pulls). A large portion of the STI crowd is like that: GTX35 turbos and gobs of power...above 5K rpm.

So true. My gr sti was pretty fun with just a flash and turboback. Lots of torque early (like 340ft/lb @ 3200rpm) and great response. I made the mistake of going big turbo (fp red) on my first sti and while the rush of power up top was fun, it was worthless day to day. Transient response is so underrated for a street driven car. This makes me want to go the expensive route and just stick to NA.

[gmookher]

there isnt a racecar in the world thats built to make power at 3000 rpms guys

[industrial]

Originally Posted by gmookher

there isnt a racecar in the world thats built to make power at 3000 rpms guys

Not everyone wants to drive a racecar everyday. Or I'd be in an exige.

[Supermassive]

The thing is that even with the turbo's torque curve and power, most of these turbo kits are at 75% of their torque before 4k rpm. Also i dunno about most people here but when I am in the twisties I keep the car in the 4.5k+ rpm range just to stay in the power of the stock engine...with a turbo you dont have to change how you drive this car since all of us already know that stock power doesn't really come on til after 4k rpm. So what is with all the misguided hate for turbos on this car.

[serialk11r]

Originally Posted by Ryephile

It's rather surprising how ignorant most aftermarket tuners are of the TVS's unrivaled qualities. Not to totally derail the thread, but personally I feel this would be a fantastic solution for the FA20. TVS's overall efficiency is excellent and they're still an air pusher, so there's no inherent significant parasitic drag from internal compression like a twin-screw or centrifugal. They're really the best overall solution for a supercharged setup, but they're also the most expensive.

That said, a good small turbo setup would give a big flat torque shelf while offering the best fuel economy. You can't have everything; a small turbo setup would trade throttle response and a little bit of lag for better FE and more torque in a less-expensive package over a TVS setup. For most enthusiasts that can't swing a $8k TVS setup, a $4k small turbo solution that gets great fuel economy and is super fun on twisty back roads is hugely attractive.

Eh, I don't think a small turbo's fuel economy would be any better than a TVS, and it might even be worse if it has the usual spring actuated wastegate rather than an electronically controlled wastegate due to the extra restriction. The turbine is going to be the reason for the power falling off at higher rpm, unless you want to blow off a lot of boost pressure throughout the powerband to flatten the torque curve (could be done to improve reliability, but then again, why not just use a cheap Eaton M62 if you're going to run the turbo so inefficiently).

It's too bad that the smaller TVS units are impossible to find. If they don't hurry up, variable speed centrifugal chargers might take off and nix any chance they had, they have to work at taking away market share from turbos anyhow. Truth be told, the 5th gen M45 and M24 are pretty efficient and are actually better suited for low boost than the TVS chargers in some situations (though the TVS still has packaging/mass advantages), someone should try strapping an M45 to the FA20, running the M45 at max speed will give maybe a 25% bump in power everywhere and that would represent a very efficient usage of the supercharger, although you won't be able to just swap pulleys if you're not happy with the power.

[gmookher]

Its not misguided.
Supermassive, youre building it right.

your project will be kosher when its done
most the guys on here think they can strap on a turbo kit for $4000 and be done
youre smart enough to see the big picture, dont give everyone on this forum that credit

early boost= smaller turbo, and that seems to be the trend to try and make power down below 4500 rpms, which makes no sense to me at all
without fuel upgrades, 9psi is the max, no matter whose kit you buy so its all boost curve vs TQ curve choice, buyers

past 10psi, it depends what youre building, and your budget

can the motor run 15 psi?

yup

supermassive is an exception, I wouldnt suggest you emulate him unless you have his experience set, budget and expectations. Not everyone is ok doing what he is doing, so watch in awe, but realize what he is doing isnt gonna be for everybody

I put him in with crawford, fully executed build potential is there. not for average joe's budget tho
for most folk a 6 psi kit is great
for some who want and know how to handle the power overage, they can get to that 9psi spot

it will be a very small percentage of folks who exceed the fiscal barriers presented past 9psi

[leon78]

Originally Posted by gmookher

there isnt a racecar in the world thats built to make power at 3000 rpms guys

My speed3 was tuned to hit full boost by 3200 rpm at 21 psi...and tapered to 17 by redline. Where talking K04 here, so lots of torque down low. This was great for a DD....so not really racecar status.

[gmookher]

Originally Posted by leon78

My speed3 was tuned to hit full boost by 3200 rpm at 21 psi...and tapered to 17 by redline. Where talking K04 here, so lots of torque down low. This was great for a DD....so not really racecar status.

right. its a ms3. no offense.

[leon78]

Originally Posted by gmookher

right. its a ms3. no offense.

Ya, bitches love turbo wagons....lol, Im just saying in reguards to OP's post....small turbos are great for real world driving. They may just be blowing hot air up top, but thats where meth comes in, and E85 if ya got it. Lower BAT's and help prevent KR.

[gmookher]

wagons are hot dont get me wrong, but the turbo at 3000 rpms peaking is a turn off
that tells me alot about what I will get at 6000 rpms
anyways, I will digress and brag about our wagon, which I saved up for and lusted for over a few years before buying:

2005 s4 AVANT (wagon)
4,163 cc 4.2 liters V 8 front engine Quattro with 84.5 mm bore, 92.8 mm stroke, 11 compression ratio, quad overhead cam, variable valve timing/camshaft and five valves per cylinder
Power: 254 kW , 340 HP SAE @ 7,000 rpm; 302 ft lb , 409 Nm @ 3,500 rpm
Top speed 155mph.
0-60 5.4 seconds
QTR 13.7

I eat NEW mustangs & hemi chargers and the like at red lights only to have them catch up ask, and I tell them its stock, which is true 100%

yes, ms3's are cute cars

[arghx7]

Originally Posted by gmookher

wagons are hot dont get me wrong, but the turbo at 3000 rpms peaking is a turn off
that tells me alot about what I will get at 6000 rpms
anyways, I will digress and brag about our wagon, which I saved up for and lusted for over a few years before buying:

2005 s4 AVANT (wagon)
4,163 cc 4.2 liters V 8 front engine Quattro with 84.5 mm bore, 92.8 mm stroke, 11 compression ratio, quad overhead cam, variable valve timing/camshaft and five valves per cylinder
Power: 254 kW , 340 HP SAE @ 7,000 rpm; 302 ft lb , 409 Nm @ 3,500 rpm
Top speed 155mph.
0-60 5.4 seconds
QTR 13.7

I eat NEW mustangs & hemi chargers and the like at red lights only to have them catch up ask, and I tell them its stock, which is true 100%

yes, ms3's are cute cars

cool story bro. you realize that they replaced the 4.2 with a blown 3.0 right?

[Dimman]

Originally Posted by Supermassive

The problem you run into is that if you go with a twin setup you only have 2 cylinders spinning a turbo, in effect you have 1 liter of displacement per turbo. It's not ideal, but a turbo feeding a supercharger could be interesting...

Another thing to consider is where the hell would you cram a dual turbo setup in this car...dunno if you've looked under the car but theres not much room under there for getting too crazy with the turbo setups.

That's not the whole picture.

I did a rough calculation comparing the moment of inertia between 2 43mm dia cylinders vs 1 60mm dia cylinder. Heights were adjusted so total surface area was the same. The 2 43mm cylinders have only 74% the mass and 38% the rotating inertia of the 1 60mm cylinder.

While turbines and compressors are obviously not solid cylinders, the same principle applies to twin vs single turbos.

So while you have 50% the exhaust flow per bank you are only pushing against 19% the inertia.

[Ryephile]

Originally Posted by gmookher

there isnt a racecar in the world thats built to make power at 3000 rpms guys

wake up man, your agenda doesn't match everyone elses reality.

My inquiry is not aimed at anyone going to the track or racing. The intent is to offer an option for those that end up being stuck in traffic a majority of the time and want accessible low-end grunt.

Originally Posted by Supermassive

The thing is that even with the turbo's torque curve and power, most of these turbo kits are at 75% of their torque before 4k rpm. Also i dunno about most people here but when I am in the twisties I keep the car in the 4.5k+ rpm range just to stay in the power of the stock engine...with a turbo you dont have to change how you drive this car since all of us already know that stock power doesn't really come on til after 4k rpm. So what is with all the misguided hate for turbos on this car.

That's all well and good, but it's also not the application I'm talking about. Not all of us live solely in the twisties over 4500 RPM. Don't get it twisted, there's no hate, let alone misguided. There are obviously plenty of turbo options out there for your preferred application. My point is there are none for the average city commuter that is stuck in traffic, then needs to shoot the gap, only to realize his turbo is too huge to spool up until he's already been cut-off by an angry soccer mom in a minivan. This is where my call for a lower boost threshold kit stems from.

[raul]

The type of turbo you describe you want for this car doesn't match it's personality and design, which is why you probably won't see turbo kits of this type for this car. You want enough torque to avoid having to downshift to pass, which to me seems more like a luxury car trait, not a sports car trait. Yes, it would be nice, but if you're tired of downshifting to pass, maybe you should have chosen the automatic transmission.