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Turbo Charging and Forced Induction BASICS

Provience said:
here is a question that's probably right up your alley :flipoff2:

none, and i do mean none, of the turbo maps i've been able to find are in any way charting 3-7 psi stuff for a 300 cubic inch + engine. damn near everything is way off on the bottom right, bottom left, or at 6k rpm WOT they might just touch the base of a 70%+ efficiency island.

does that actually just translate to the efficiency dropping off (let's say, to 50%) and won't actually cause things to be unhappy or damaged? building something low power would much rather toss efficiency out the window over price and backpressure and detonation. is it more important to just find a turbo that will support 1.4 ratio and whatever CFM at 2000 rpm in addition to 1.4 and 5k rpm?

i think i'm having a hard time reading the island maps, or maybe not and i'm just confusing myself
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With a centrifugal compressor you will never see 100% efficiency. 80 is very high.
Both sides of a turbo charger have leakage.
Their is no positive seal around the exhaust/turbine blades to turbine case so some of the expanding exhaust gases/energy leaks through as losses.
The same way with the compressor blades with no positive seal between the compressor blades and case so they loose some of the pressure built as leakage between the blade and case.

One thing that helps with efficiency is variable vane geometry found on newer vehicles turbo chargers . This guides the exhaust gases in the most efficient paths across the turbine blades depending on load, speed, and temperature. The best way to control these are with a processor.
 
To me surge is more of a concern than overspeed.
‘Loading and unloading a fast spinny piece of equipment can shorten the life greatly.

I don’t know if overspeed to catastrophic failure is a big deal on a turbo charger. If it was we would have all kinds of you tube videos showing the carnage. :grinpimp:
 
IGT said:
To me surge is more of a concern than overspeed.
‘Loading and unloading a fast spinny piece of equipment can shorten the life greatly.

I don’t know if overspeed to catastrophic failure is a big deal on a turbo charger. If it was we would have all kinds of you tube videos showing the carnage. :grinpimp:
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nice, surge seems easier to mitigate
 
Your dynamics of pressures and temperatures at both suction and discharge of your compressor determine your surge line and efficiency.
That’s where some of the head, flow, and efficiency curves are derived from. The shape of the blades and case are the other dynamic.

Most think that pressures, P1 and P2, are the biggest factors of performance but temperature, T1 and T2, are equally as important.
That is the why we have intercoolers and aftercoolers.
 
IGT said:
Your dynamics of pressures and temperatures at both suction and discharge of your compressor determine your surge line and efficiency.
That’s where some of the head, flow, and efficiency curves are derived from. The shape of the blades and case are the other dynamic.

Most think that pressures, P1 and P2, are the biggest factors of performance but temperature, T1 and T2, are equally as important.
That is the why we have intercoolers and aftercoolers.
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does it stand to reason the increased volume between the throttle blades and compressor wheels is generally effective at minimizing surge?

for the rear mounted consideration with a 5' or more length of intake tube, in my head, it seems like there would be enough volume to turn a ~10psi into much less actual force just because there is so much more volume to work with.

or does it not work that way because pressure is pressure :homer:
 
Provience said:
does it stand to reason the increased volume between the throttle blades and compressor wheels is generally effective at minimizing surge?

for the rear mounted consideration with a 5' or more length of intake tube, in my head, it seems like there would be enough volume to turn a ~10psi into much less actual force just because there is so much more volume to work with.

or does it not work that way because pressure is pressure :homer:
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Heat and expanding exhaust gas is the energy for the turbine wheel and blades. The further away away from the source the more losses of that energy. But volume sometimes is beneficial because reactions to flow changes happens slower.

Think of surge as pressure of the compressor trying to go backwards instead of forwards into the charge air into the cylinders.
In a centrifugal compressor there are no check valves to keep the pressure of the compressor going in the direction of design.
If P2, compressor discharge pressure, has no where to go, lowering load of engine or RPM, the pressure of the compressor has no where to go but backwards to the compressor. This causes surge. That’s when the pop off valve opens relieving unneeded charge air.
 
Provience said:
Carburetor and Intake Manifold Design for Superchargers on Older Motorcycles (victorylibrary.com)


Eaton supercharger data (victorylibrary.com)

despite claiming to be all about motorcycles, this page has some awesome supercharger information.

apparently Eaton's are sized by C.I.D. with the M122 being ~$1200 on ebay, the M112 ~$600, the M90 being ~$300

let's pretend 5.5k is our engine max rpm.

M122 max sustained RPM = 11k = 1,342,000 CID/M * 0.000578 = 775.67 CF/M is theoretically 570hp would give up 2:1 pulley ratio gives us "cruise" engine RPM of 2.2k and supercharger "theoretical" airflow of 310 CFM or about 227hp would put us about 540 lbft

M112 max sus rpm = 12k = 1.344M = 776.8 CFM is the same theoretical 570hp with a 2.18 ratio pulley "cruise" airflow of 310 CFM ... huh

M90 max sus rpm = 12k (but apparently get modded up to 17k?) is 624.2 CFM is about 460hp same 2.18 ratio pulley "cruise" airflow of 249 CFM is 183 hp and about 436 lb-ft

Page Title (mscperformance.com)

this is also an interesting page, it has a chart that shows the M90 requires 28-42 hp to operate depending on if you are running 5 psi or 10 psi

honestly, looking at those charts makes it look like there is almost nothing to gain except for heat from running the M90 at 10 psi instead of 5 psi (well, less than 10% gain inlet airflow for about doubling the heat on average)



Mustang GT500 Supercharger Tests - Twin Screw Vs. TVS (mustangandfords.com)
Mustang GT500 Supercharger Tests - 5.0 Mustang & Super Fords Magazine

Planet Soarer: Estimating Boost and Eaton Pulley Change

I can see a pretty good push for the M112 with a lower RPM engine

with the M122 being a "theoretical" 570 hp and producing on the dyno 520 hp, knowing we lose ~25hp at least just to turn the thing, i'm pretty happy with that estimation.



i'm surprised that the M112 and M122 are so close in flow at their max sustained. despite finding many things that say "charts are easy to find" I actually can't find power/airflow/rpm charts for the M112 and M122 :confused:

this is all spawned from arse_sidewards suggesting the AMR500 and me spending an hour or more thinking about what it would take to rig up 4 of them together :laughing: :flipoff2:
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Your numbers are pretty close.

He also tried a M90 on the same engine and that wasn't cutting it

 
He's legit AF.
I'm building my blower setup based on some of his work and the various sloppy mechanics recipes that have proven results.
 
I will.
Lots to be done before I'm ready to release any info though. I want to make sure I have it pretty dialed before I'm sharing tech.
 

neat article for estimating HP using 1/8 and 1/4 mile trap speed, close enough for estimating purposes certainly to see where you are before a FI swap and what about you end up with after

meat of it

1/8 MILE vs. 1/4 MILE.

After monitoring tons of good passes, patterns emerge. Typically, the mph at the quarter is around 1.26 times of the mph at the eighth, and the time at the quarter is around 1.55 times the time at the eighth. You can use these values if you only have a 1/8 mile track and get a real good idea of the theoretical 1/4 mile.​
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THE HP FORMULA.

Here's the formula to use to calculate HP:

Net HP = Weight in pounds x (Speed in MPH/228.4) ^ 3

As an example, a car magazine tested a car that weighed 3,081 lbs. without the driver (the race weight was 3,231 lbs.) The car ran a 15.7 second quarter at 86 mph. Let's plug it in to the formula:

HP = 3231 x (86/228.4) ^ 3
HP = 172 Net

The vehicle manufacturer rated it at 162 Net. We come out a little high (or did the manufacturer underrate it a little?)

Still, for such a simple formula and such a simple test, it's surprising how accurate this can be. And the best thing is -- there's no arguing the numbers on a timeslip. There are always differences between DynoJet and Mustang dyno numbers, because every setup is done by someone different and subject to error. The quarter mile is arguably the best comparison you will ever have. The only real difference to argue about is the altitude of the track! You can compare ET and mph all day and have a good discussion.​
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online calculator


if you know your weight, sweet, if you don't then advertised curb plus driver will be close enough. again, not exact anything, but if you are within 5% who really gives a shit?

and i've downloaded the "trackaddict" app for the smart phone to use GPS to get an estimated 1/8 mile timeslip :rasta:
 
Good thread Provience.
I chose a transaxle low pressure turbo 4-banger for my new buggy precisely because I want a smallish package plenty reliable power and response as immediately as possible when i mash the throttle.
The engine I'm using provides max torque from 1700rpm.
 
No way said:
Good thread Provience.
I chose a transaxle low pressure turbo 4-banger for my new buggy precisely because I want a smallish package plenty reliable power and response as immediately as possible when i mash the throttle.
The engine I'm using provides max torque from 1700rpm.
Click to expand...
awesome and thanks :smokin:

what kind of details have you got pictures of that you could share on your setup?

Engine size/turbo size hot & cold, wastegate size and setting, relief valve size...them sorts of things
 
Provience said:
what kind of details have you got pictures of that you could share on your setup?
Engine size/turbo size hot & cold, wastegate size and setting, relief valve size...them sorts of things
Click to expand...
It's a bone stock 2005 Saab/GM 2,3L. I don't know squat about any of those things :laughing:

If it needs more power I go see a man about a tune..
 
subbing to this thread.

any thoughts on suck through, you gain some advantages of the fuel being atomized in the air charge but not as much as intercooling and you cant intercooler. Advantages of using a stock-ish carb which is alot of the battle. with that no boost reference fuel pump and the like BUT.

You can super heat your fuel if you dont isolate the exhaust heat from compressor side of things, remote mounting carb, linkage issues etc.


has anybody done any looking into how much the exahust before the turbo effects turbo performance. My engine doesnt have a turbo manifold for it. But ive founds some builder flanges and ive thought of just doing some 3-4 inch stand offs then welding a tube across all the ports to a vband, pipe around the engine. same on the other side but connected to y pipe before turbo flange.

Thats a bunch of exhaust hitting a a hard wall before moving on
 
A_G said:
subbing to this thread.

any thoughts on suck through, you gain some advantages of the fuel being atomized in the air charge but not as much as intercooling and you cant intercooler. Advantages of using a stock-ish carb which is alot of the battle. with that no boost reference fuel pump and the like BUT.

You can super heat your fuel if you dont isolate the exhaust heat from compressor side of things, remote mounting carb, linkage issues etc.


has anybody done any looking into how much the exahust before the turbo effects turbo performance. My engine doesnt have a turbo manifold for it. But ive founds some builder flanges and ive thought of just doing some 3-4 inch stand offs then welding a tube across all the ports to a vband, pipe around the engine. same on the other side but connected to y pipe before turbo flange.

Thats a bunch of exhaust hitting a a hard wall before moving on
Click to expand...
is the concern about intercooling with suck through that you would de-atomize your fuel? it seems like running smaller, whatever that is, intake tubes and runners would help keep the air charge velocity up to help keep it atomized while making sure that the intercooler wasn't too large. at least, that seems like the best way to keep the fuel atomized and still have some gain from lower temperature.

just in my head and based on nothing.

the other concern would be monitoring the vacuum signal at the carb base to ensure that it isn't reading high vacuum under load when the compressor is drawing hard through it. the holley and edelbrock both use vacuum signal referenced springs in addition to the jets to supply mid load and WOT fuel, you'd either want to reference those to the manifold vacuum OR make sure you have a strong enough spring that it can overcome whatever vacuum you are actually seeing with the compressor kicking off as it sucks hard through the carb.


as far as the exhaust manifold, in a random act of fanboi-ism I actually "asked on social media" to the engine masters show about basically that. Baseline a motor with stock stuff, then hook up a turbo to it an plumb the cold side just into a box with a couple smaller holes in it so that it will build boost, and dyno it set at 5 and 10 and 20 PSI to measure just how much the exhaust restriction makes a difference if there is no additional power. The exhaust pressure on a turbo is the equivalent type of loss as the pulley and belt off the snout of a supercharger, it is just harder to "see" the exhuast power loss, though it is certainly there. Obviously, like a supercharger, it is worth it to eat the loss for the gains you get and it is more of a balance across the system when you are forcing more air in to make it easier to force more air out.

anyways, yeah, have at it. 3" runners before the flange is very common. people run absolute trash manifolds and call them "turbo manifolds" all the time, a smooth short runner would be better than a log, but even the logs work. Nice thing about short runners is you get more heat. more exhaust heat means the exhaust doesn't have to work as hard to spin the turbine.
 

Draw thru Turbo w/ Carb Question, Disappointing Replies (Page 1) — Lemons Tech — The 24 Hours of Lemons Forums

Draw thru Turbo w/ Carb Question, Disappointing Replies (Page 1) — Lemons Tech — The 24 Hours of Lemons Forums —
forums.24hoursoflemons.com forums.24hoursoflemons.com

pretty interesting thread, of course, lemons being lemons they aren't overly concerned about max efficiency or peak anything, but that is also kind of the point. what is the bare bones simple that works and does "better"

on poster in that thread says they used a vacuum secondary holley carb and did have some driveability issues, that were easily ignored, due to the change in vacuum signal with boost, and another guy says he did absolutely nothing to the carb and had no complaints, also with a vacuum secondary holley.

neither of them claim to run a blow off valve and neither had an issue.

Unfortunately, the carbon based seal really is your only option in this endeavor. However, it works surprisingly well.
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seems to be the consistent reoccurring theme, check that your turbo has good seals in it or replace them to "carbon based" and rock on
 
 
dismayed at the internal combustion engine's low thermal efficiency numbers and the gobs of waste heat that the engines produce
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from the link above, an interesting article but it's still fun to note that ~30% efficiency is "dismal" for ICE, but electrics would be thrilled to reach that same goal :laughing: from source to source, ICE still comes out on top from a draw it out of the ground, refine it, burn it for fuel compared to convert sunlight, transport it, retain in a battery, release it for motivation timeline :rasta:
 
A_G said:
has anybody done any looking into how much the exahust before the turbo effects turbo performance. My engine doesnt have a turbo manifold for it. But ive founds some builder flanges and ive thought of just doing some 3-4 inch stand offs then welding a tube across all the ports to a vband, pipe around the engine. same on the other side but connected to y pipe before turbo flange.
Click to expand...
An engine at its most basic is an air pump. Poor flow characteristics = pumping losses. The additional pressure from forced induction helps overcome pumping losses but is still no substitute for proper design
 


I watch quite a few of this guys videos. This one caught my interest the other day and seems relevant to add. He shows the difference between a twin scroll and duel volute turbo's air flow on the turbine side of a turbo. kind of reminds me of the 180* header concept and makes me think of a Subaru with BRAPP headers.

what I find interesting is the high static compression ratios of today's cars along with there added dimension of forced induction. Im no expert on the performance side of the game (im not a "tunner"), but I work on quite a few turbo cars (mostly Ford ecoboosts and chevys) to pay my bills. The orchestrated events of vairable valve timing, variable valve lift/duration, and direct injection seems to keep everything in check. We had a 2019 Mazda CX30 in the shop about a month ago.The mechanical timing of the exhaust cam was off and the car would crank and not start. I had to do some research on the setup because its pretty new and I found the engine has a COMPRESSION RATIO OF 16.3:1! HCCI is fairly new and makes slapping a turbo on an LS seem like middle school science project. I think the newer second generation 3.5L ecoboosts are 10.5:1-10:1 and they haul ass for a V6.
 
16.3:1 is pretty dang impressive, though i'd wager the new ecoboost is putting down much higher than 10.5:1, based on zero research.

it really seems that the modern high quality timing and fuel controls are so far ahead of the TBI and other fairly dumb spray systems that they really can run compression ratios unheard of even 10 years ago as "pump gas" options. It's got to be where how and why they are making just so much more power out of these smaller motors
 
Provience said:
16.3:1 is pretty dang impressive, though i'd wager the new ecoboost is putting down much higher than 10.5:1, based on zero research.

it really seems that the modern high quality timing and fuel controls are so far ahead of the TBI and other fairly dumb spray systems that they really can run compression ratios unheard of even 10 years ago as "pump gas" options. It's got to be where how and why they are making just so much more power out of these smaller motors
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When you have a diesel style high pressure injector and can keep the fuel out of the cylinder until it's time to burn it you can do all sorts of things.
 
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