Forced Induction

roots is shit no one uses it.
screw is compact easy to fit, it's the standard these days.


>advantage of turbo:
significantly more efficient, especially at high boost levels.

>disadvantage:
more expensive due to the peripherals needed (manifold, exhaust), lag.

>aspects considered
need programmable ecu
for low boost, not much else
for high boost, steps need to be taken to control detonation like water/meth injection, lower compression, etc and internals that can deal with the high pressure and heat like forged pistons, strong rods.

other than that a stock n/a engine going to turbo on low boost (like 1 bar or less), typically just needs to be re-tuned. If you have some skyactiv shit with a 12:1 compression ratio you might have to get dished or flat top pistons to lower the compression or your timing will be shit.

>Potatoes in the trunk

>>14045205
also turbo is tuneable on the fly even while driving to adapt to situations. boost controllers can do some cool stuff.
and even without an expensive ecu and boost controller you can still static tune a turbo to any boost pressure you want with just a simple pressure actuator. with a supercharger you have to change pulley sizes and shit.

superchargers have their merits, but they are basically outclasses in every way these days. modern turbo systems are too good.

>>14045246
>>14045205
also to expand on why they need a programmable ecu

for one, stock ecu maps probably don't have parameters for over barometric manifold pressure. and for two, turbo cars will have significantly different timing maps due to compressed air/fuel charge propagating a lot faster. And for three, not necessary, but in certain load conditions, to be safe, turbo tunes usually run a bit richer. So even if for some crazy reason your stock ecu had parameters for over 100kpa manifold pressure they would still need tuning.

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>>14045246
While the technological advancements in turbos in these recent years have allowed for minimal boost threshold and lag in OEM turbocharged engines, many manufactures such as Audi, Ford and Chevrolet still use Positive Displacement compressors in some of their power plants.
Do they do this to minimize costs and due to tight engine bay clearances or there are other reasons for that?

>>14045323
yes, the main benefit to superchargers as far as OEMs and kit manufacturers is the reduced cost and easy packaging. They are just simpler, easier to sell as kits, easier to make fit in tight spots, easier to design.

the no lag and linear power is a plus, but as you said modern turbo systems especially with advanced boost controlling, even garage brewed ones, properly tuned, it's no longer a real issue. the efficiency gains outweigh the remaining lag.

>>14045323
Complexity.

Easier to manufacture an intake manifold and throw a supercharger on it than complicating the intake piping and exhaust piping...especially on v-motors.

>>14045246
Without a doubt turbos are better than a supercharger.

But honestly I would much rather have a supercharger because it sounds so much better. You can still put power down because muh boost

>>14045205
could you be anymore wrong? Virtually every oem supercharged car uses a roots type blower for reliability and low rpm power.

The only stock twin screw I know of was the Ford gt.

Roots blowers make unfathomable amounts of power off idle while twin screen blowers have a power delivery that feels much more like a high rpm turbo.

Turbos generally produce higher peak hp but less average power throughout the rpm range.

>>14045374
most aftermarket road racing oriented supercharger kits are screw. they make more power and are more compact and remain linear nothing like a high strung turbo at all.

>Turbos generally produce higher peak hp but less average power throughout the rpm range.
this is just wrong, a properly sized turbo can create more boost sooner at WOT and load regardless of rpm.

>>14045435
after initial threshold I mean, not directly off idle like a roots.

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>>14045374
>Roots blowers make unfathomable amounts of power off idle while twin screen blowers have a power delivery that feels much more like a high rpm turbo.

This dyno graph is from a Whipple twin-screw supercharged '03-04 Mustang Cobra running at 19 psi. The torque curve seems to be pretty smooth.

>>14045435

Negative champion. You will not build boost below the transition period with a turbocharger without EMP's going through the roof at target boost. Or you can keep manifold pressure and EMP as close to 1:1 as possible and lose boost down low in the transition period. Or you can use multiple stages of compressors to broaden the transition period with added weight, complexity and heat output (the pressure ratio is multiplied with two or more stages of compression but then as is the heat output.)

A roots blower will make boost off idle. That cannot be replicated with turbochargers without serious limitations in the middle and upper rev range, but then the turbocharger will not replicate the extreme heat output of a roots blower.

I've had a roots blower, a centrifugal blower and a single turbocharger all on the same SBC combo. Power wise the turbo could not be beaten but my word, the feeling of the roots blower is like nothing else. Vicious power delivery, truly something else.

That said now I've moved to a turbocharged 2JZ away from a blown SBC.

Transition response - peak mechanical efficiency - peak thermal efficiency

You may pick two.

>>14045322
You seem like you are smart, how do I learn more about ECU's boost controllers and the like, what's a good one for a budget turbo build, any good books?

>>14045525

Not that fella, but a great way to learn is to download the editing software for currently available ECU's and go through every setting until you understand what the setting is, what it effecting and the flow on effects to other tables or maps that changing this setting may have.

Stinger, Holley, AEM and most of the other big names have the editors available for a free online download. Give it a good dig!

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>>14045472
it's pretty flat but doesn't really peak until 4k rpm

Hi /o/, when a turbo kit is advertised as a bolt on kit, what can you expect to do other than bolting shit on and taking old stuff off?

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>>14045525
ECUs vary from vehicle to vehicle, so there's no one-size-fits-all response. Stock computers are pretty robust these days but there's plenty of room to grow even with the 28-pin EPROM chip in my '86

There are two types of boost controllers, manual and electronic. Manual boost controllers are basically just a relief valve in the vacuum/boost line that runs to the wastegate. When the pressure reaches the setpoint, boost pressure is allowed through the MBC to the wastegate diaphragm which opens the WG.

Electronic boost controllers sense the pressure and open via solenoid. The solenoid is usually actuated by the computer

>>14045525
Not who you were talking to but I'll step in.

You are after engine management theory.

First you need to ask yourself: how much control do YOU as the user want, and di you wish to maintain the stock sensors?

The best set ups right now run speed density setups, utilizing a MAP sensor and IAT.
Secondly, if you are going to self tune... get a wideband with analog output - non negoiable. Even the fastest displaying gauges can not display in time for you to notice you have leaned out a cell.

A set up like haltech or megasquirt costs a pretty penny, but are really for more advanced users who understand the workings of engine management.


If you dont understand it, a power programmer that lets you increase fuel loads by percentages will work -but it will not be optimal. It will run less than the potential you want.

>>14045559
yes

>>14045525
garrett's turbo tech docs are good for learning about turbos, megasquirts tuning documentation is pretty good for the basics of tuning. there's probably some books that talk about more specific stuff like propagation and valve timing and such, but i dont know any off the top of my head.

http://www.megamanual.com/v22manual/mtune.htm#
https://turbobygarrett.com/turbobygarrett/turbo_tech_basic

>>14045559

It really depends man. Was your car originally turbocharged? If not, are your spark plug leads going to foul on the charge piping or new manifold? Will you have to relocate wiring away from the hotside? Does it have every t-clamp and bend you will need?

What about the charge piping itself, do you need to cut or remove any body panels to route the pipework?

I would take most bolt in kits with a grain of salt. I have not had the pleasure of a 'kit' being a bolt on solution. Piecing together a package to suit your engine bay pays off when it is time to put it in.

>>14045624
i linked you the wrong shit ignore that megasquirt link this is the one i meant

http://www.megamanual.com/begintuning.htm

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I went with a Twin screw because of the linear power delivery.
i see Turbo LS engines hitting boost and lighting up the tires.
i wanted something that was controllable for a street car.

>>14045119
>anon: do my homework for me /o/
>/o/: [shitposting intensifies]

>>14045898
theres no shitposting in this thread tho.

>>14045885

CTS-V fag?

>>14045914
I wish i had the cash for a CTS-V
it's just a TVS 1900 from a ZL1
got it for $500
gonna put it on a 5.3L

>>14045950

Jelly, how the fuck did you find a 1.9 for $500?

>>14045950
wouldn't a centri have been better for what you wanted?
that said for $500 who cares

>>14045957
There was a recall on all CTS-V and ZL1 blowers.
a isolator was making noise so Cheby replaced them all.
Eaton didn't allow them to do the $30 repair, so the whole unit had to be replaced.

they are more expensive now on ebay at $700

>>14045374
Roots and twin screw both make power at idle. That's what being positive displacement means: they make peak boost at all RPMs. Twin screws are typically more efficient, but more expensive to produce and have lower RPM limits since the secondary shaft spins at double drive speed.

Centrifugal superchargers increase boost linearly with RPM. They have the least parasitic loss of all supercharger types; they actually have lower losses than turbochargers (from backpressure).

Turbochargers have much lower losses than positive displacement superchargers, but make much more power low down then centrifugal superchargers. Rather than scale up in boost linearly, they make no boost until they hit a certain threshold and spool up to full boost very quickly. You can't increase the efficiency of an engine by bolting a turbo up to it like some people claim, but using a smaller turbo engine to make the same power as a larger naturally aspirated engine can save fuel while cruising.

>>14046055
>the secondary shaft spins at double drive speed.
What?
the shaft and both rotors are a 1:1 ratio.

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I would like to run a m62 off of a Mercedes on a toyota 20R, do you think the rotor bearings will lunch pulling air and fuel in a draw through setup or do you know of a sealed bearing retrofit? How much boost do you think oem cast pistons will take? Oem forged crank and rods should bee able to handle it with arp hardware.

Aiming for ~220hp

>>14045652


That link is pretty decent. Theres some stuff in there that it skips over of course, but its pretty helpful.

For example, min pulse width is a tpic that needs to be discussed in great detail. My 810cc injectors have a min pulse width of 1.2ms. Which means my car idles at 12.5 afr... because if I lean it out anymore my car dies.

>>14046860
yeah its just a basic overview, but it does have a lot of information for someone who doesnt know about tuning. it has the most information of any basic tuning page that i've come across anyway.

>>14045561
>>14045652
>>14045567
>>14045624
>>14046860
Just what i was looking for you fellas are great.