Turbochargers: Am I missing something?

[injb]

I don't have much to add, but since gratuitous pics are usually welcome, here's a bit of turbo propaganda that Porsche released in the 80s. This is all the parts that are different from the naturally aspirated 944 on the turbo version.




In 1988 these made 250HP from a 2.5L 4 cyl at a very modest 11psi of boost.

And of course, I can't not mention the BMW M12 turbo Formula 1 engine, that made 1500HP from 1.5L:

https://www.youtube.com/watch?v=r2J-d5MH6s4

 

[russc2542]

You're probably the only person in the world that thinks that, given the 3.5L EcoBoost's torque curve & peak relative to modern naturally aspirated V8s including the 5.0L Coyote.

For the record, I own a 5.3L Silverado, but the 3.5L EcoBoost is a heckuva engine for doing 'truck stuff'. Yes, it gets thirsty when towing or hauling - you can have Eco OR Boost, but not both at the same time....

That's what I was getting at eco or boost, not both... yes it has v8 power and maybe even better bottom end but it has worse BSFC (worse mileage when making the same power).

...
Secondly, I very much dislike the throttle lag and throttle response this engine has. You can't "blip" the throttle for 1/2 second to cross a road. I can fully floor the pedal and let off of it, with no engine response. Secondly, due to the lag, when pulling out in front of traffic, you get no power so you give throttle, nothing happens, so you give more, nothing happens, so you give more and finally the engine wakes up and ROARS, squealing tires and everything. I just wanted some nice even acceleration...

This isn't the fault of the turbos. This is 90% the fault of the throttle (namely, that it's an electric motor). When you put your foot down, you aren't opening the throttle. you're changing the reading on the sensor. once the ECM sees that change it has to calculate what to do to accomplish what it thinks you want. once it calculates it, it has to make it happen and I guaran-darn-tee you can move your foot faster than the motor can move the throttle (I can in all that I've tried). On top of that, yes it takes a second for the turbos to spool up AFTER the engine spins up. Due to the e-throttle, you have to lead with your foot .2-.5 second (depending on the vehicle and desired action). I have a pair of Subaru Bajas... one's NA, one is a factory turbo upgraded with STI bits. The NA is WAY WAY more responsive to throttle input... floor it and it revs up like you'd expect. The turbo revs faster once the throttle's open but takes longer to do it... floor it, pause, idle to about 2500 rpm are lackluster, then BAM it's at 7k.

He's about 90% right.

The EPA test that measures fuel economy and emissions is mixed stop and go driving and some cruising at 55 mph. So, that is what automakers calibrate and design for.

If the ecoboost doesn't have EGR I'll fall out of my chair with shock. Nearly all engines need EGR to keep the NOx numbers down. Ford just turns off EGR at higher loads, because it kills performance and increases HC emissions. I suppose if they spent more time calibrating EGR at higher loads maybe they could do the same thing, but what's the point. That's a lot of spend for some perceived good will from the customer.

Actually lots of cars started dropping dedicated EGR when variable valve timing got big. Why bother with dedicated systems when you can play with the exhaust valve timing. either close them early and keep some in or hold them open long and the intake stroke vacuum do it's thing.

Most cars only use EGR during a narrow window of operation (light cruise at certain RPM window) where the NOx is usually high AND the EPA measures it. On my old firebird it's about 1200 rpm-1800rpm and 10-18 inHg or something like that. nice neat box. old vacuum actuated systems running off port vacuum only used it similarly (off idle low throttle, light load)

The other factor in turbo car reliability is usage: most people do enjoy the sound and sensation, the ones that aren't neglected are going to see harder use than the boring NA brethren. case and point: I finally got the turbo Baja running right and tuned enough to take to auto-cross. holy cow, that thing scoots like a raped ape! Even with the extra 500lbs and no boost control tuning, I bet it's every bit as fast as my previous auto-X: LT1 6-speed firebird with sticky auto-x tires. Alas, the ticking noise from the 150k mile engine turned into a rather more pronounced noise after some time at 20psi...

 

[BugI02]

rus, I can only speak to Subarus (and likely you're aware of this) but the throttle controller is designed to slow and smooth opening and closing of the throttle predominantly for EPA and mileage purposes. There are tweaks to mapping and parts change-outs that can drastically improve throttle response. Don't know if IN does emissions testing, if so make sure changes are reversible (mapping) and save the OEM parts

 

[russc2542]

rus, I can only speak to Subarus (and likely you're aware of this) but the throttle controller is designed to slow and smooth opening and closing of the throttle predominantly for EPA and mileage purposes. There are tweaks to mapping and parts change-outs that can drastically improve throttle response. Don't know if IN does emissions testing, if so make sure changes are reversible (mapping) and save the OEM parts

I'm curious and open to whatever suggestions you have but the Baja already thinks it's an STI (presumably as responsive as there is from the factory). I've looked at the tables available in Romraider/Tactrix cable and they get into pedal-to-throttle relationship tables but there's nothing related to the speed of operation, that's probably all in the equations that read from the tables.

If you're referring to the plug-in interceptors between the pedal and ECM, those only change the curve of the reading from the pedal and cannot change the speed of the throttle body. In fact, while it may not be perceptible, slow down the response because the interceptor has to get the signal, change the signal, and pass it on.

I'm not even getting into transients (on-off-on-off), just put your foot down and wait. On transients, I've logged it and I can hit the floor and have the mech-throttle closed again before the e-throttle can even get WOT. (double clutching an e-throttle is a great test)

 

[BugI02]

For towing I would think electric could make inroads, peak torque available at most any rpm and performance independent of altitude. Likely have to be hybrid, though, to achieve any range

Back in my racing days everybody just had a dedicated tow vehicle that didn't also try to be the family car. I'm thinking the desire to have a truck-like vehicle - one thats large and roomy but rides like a car for everyday utility - has somewhat neutered the breed

 

[BugI02]

I'm curious and open to whatever suggestions you have but the Baja already thinks it's an STI (presumably as responsive as there is from the factory). I've looked at the tables available in Romraider/Tactrix cable and they get into pedal-to-throttle relationship tables but there's nothing related to the speed of operation, that's probably all in the equations that read from the tables.

If you're referring to the plug-in interceptors between the pedal and ECM, those only change the curve of the reading from the pedal and cannot change the speed of the throttle body. In fact, while it may not be perceptible, slow down the response because the interceptor has to get the signal, change the signal, and pass it on.

I'm not even getting into transients (on-off-on-off), just put your foot down and wait. On transients, I've logged it and I can hit the floor and have the mech-throttle closed again before the e-throttle can even get WOT. (double clutching an e-throttle is a great test)

This is a pretty good discussion of the mapping issues/opportunities. https://forums.nasioc.com/forums/showthread.php?t=1537010

I wasn't aware that you might have already done extensive changes to the system, and custom designed mapping can only do so much as well as mechanical issues like turbo lag requiring mechanical 'fixes' (lower mass, twin sequential etc, exhaust improvements)

Apologies if I'm preaching to the choir, but tuner shops are the way to go unless you're comfortable doing some of this yourself. The sampling and mapping are labor intensive and a real PIA. Commercially available add-ons in NIB form will always be limited because; lawyers

 

[jkaetz]

I'm curious and open to whatever suggestions you have but the Baja already thinks it's an STI (presumably as responsive as there is from the factory). I've looked at the tables available in Romraider/Tactrix cable and they get into pedal-to-throttle relationship tables but there's nothing related to the speed of operation, that's probably all in the equations that read from the tables.

If you're referring to the plug-in interceptors between the pedal and ECM, those only change the curve of the reading from the pedal and cannot change the speed of the throttle body. In fact, while it may not be perceptible, slow down the response because the interceptor has to get the signal, change the signal, and pass it on.

I'm not even getting into transients (on-off-on-off), just put your foot down and wait. On transients, I've logged it and I can hit the floor and have the mech-throttle closed again before the e-throttle can even get WOT. (double clutching an e-throttle is a great test)

The motor on the throttle blade can snap the blade open and closed as fast as you can mash the pedal, as stated all manufacturers have placed a nanny between your foot and the motor. My 2 cents is that this is to increase their MPG by a fractional amount and help less attentive drivers have a smooth driving experience. This is even more true with the higher horsepower cars to prevent those with more money than driving skill from immediately sending the vehicle sideways from every stop.

 

[ATOMonkey]

The motor on the throttle blade can snap the blade open and closed as fast as you can mash the pedal, as stated all manufacturers have placed a nanny between your foot and the motor. My 2 cents is that this is to increase their MPG by a fractional amount and help less attentive drivers have a smooth driving experience. This is even more true with the higher horsepower cars to prevent those with more money than driving skill from immediately sending the vehicle sideways from every stop.

Most people don't like a linear throttle response, and it does help emissions when you can prevent the operator from using the throttle like a switch.

We calibrated the throttle to be lazy below something like 25% pedal, so that there weren't big swings in transient operation. Anything over 25% got real aggressive and you were full throttle by 60% pedal. This was so the vehicle would feel "peppy." Mashing the pedal further just kicks down the transmission.

High power cars have so many nannies to keep people from abusing them. Lazy clutches, lazy throttles, manual gearboxes with lockouts... I just want a car that drives, and does what I ask of it. I don't need Bluetooth or sat nav or traction control, or yaw control, or dynamic stability, or whatever else. Give me an FM radio and a real manual gearbox.

 

[avboiler11]

Give me an FM radio and a real manual gearbox.

If FCA made a Charger Scat Pack with the Challenger's 6 speed manual, I'd willingly accept the wife's wrath to have one follow me home.

 

[ATOMonkey]

If FCA made a Charger Scat Pack with the Challenger's 6 speed manual, I'd willingly accept the wife's wrath to have one follow me home.

I don't understand why they decided that the Charger should be auto only. That's a great way to ruin a car.

 

[jkaetz]

Most people don't like a linear throttle response, and it does help emissions when you can prevent the operator from using the throttle like a switch.

We calibrated the throttle to be lazy below something like 25% pedal, so that there weren't big swings in transient operation. Anything over 25% got real aggressive and you were full throttle by 60% pedal. This was so the vehicle would feel "peppy." Mashing the pedal further just kicks down the transmission.

High power cars have so many nannies to keep people from abusing them. Lazy clutches, lazy throttles, manual gearboxes with lockouts... I just want a car that drives, and does what I ask of it. I don't need Bluetooth or sat nav or traction control, or yaw control, or dynamic stability, or whatever else. Give me an FM radio and a real manual gearbox.

Agreed. There is a .5-.7 second delay in mine from 0% throttle before it allows me to have full control of the 415 horsepower and I feel the delay ever time I make a spirited start. It makes a pushrod V8 with fixed timing feel like a VVT engine. It also irritates me on shifts as I will release the pedal, complete the shift and return to the previous pedal position and half the time the throttle blade hasn't caught up by the time I release the clutch due to the delay. I just haven't spent the $$ on a tuning software suite to fix it yet.

I don't understand why they decided that the Charger should be auto only. That's a great way to ruin a car.

Crash test certification. It was never tested with the manual so they can't/don't offer it.

 

[avboiler11]

Crash test certification. It was never tested with the manual so they can't/don't offer it.

Given Challenger and Charger are the same basic platform, and use the same drivetrain...how complicated would it be to engineer a few up for crash testing? Seemingly not very.

Sure it'd likely be a limited volume product, but for a 'parts bin car' they would probably sell at a premium to enthusiasts even after charging an extra grand or so for the third pedal.

 

[avboiler11]

Also, the torque management on 14-18 GM truck 6L80s suuuuuuuuuuuuuuuuuuuuuucks...put your foot to the floor and the transmission says "Are you sure you want me to downshift?" then a half-potato later "Are you REALLY sure you want me to downshift?!?" then it drops two if not three gears as RPMs are rising.

 

[ATOMonkey]

It's not just crash testing. It's EPA testing as well. You have to emission certify every configuration of the vehicle you offer.

It's like this on all vehicles up to the 3/4 ton trucks, at which point they only emission certify the engine.

Light duty vehicles are grams per mile

HD vehicles are grams per brake horsepower hour.

 

[eldirector]

Also, the torque management on 14-18 GM truck 6L80s suuuuuuuuuuuuuuuuuuuuuucks...put your foot to the floor and the transmission says "Are you sure you want me to downshift?" then a half-potato later "Are you REALLY sure you want me to downshift?!?" then it drops two if not three gears as RPMs are rising.

Yeah. My diesel has enough lag when flooring it from a stop, that you can step out for a cup of coffee. It is all 100% intentional, to protect the otherwise under-rated drivetrain. A lot of programmers simply remove the "safety" nannies, so that you get the power you were SUPPOSED to have. They don't really add anything at all (at the lowest setting, at least).

I have driven a truck exactly like mine with the nannies disabled, and no other tune. Completely different experience. Can absolutely roast the tires from a stop, where my stock truck can't even get a squeak.

 

[ATOMonkey]

I suppose most of these new vehicles that pair a turbo with an auto trans don't let you two foot it.

 

[eldirector]

I suppose most of these new vehicles that pair a turbo with an auto trans don't let you two foot it.

Mine does not. Will not spool with the brake on. Can't even "power brake" a burnout.

 

[churchmouse]

Mine does not. Will not spool with the brake on. Can't even "power brake" a burnout.

Now that is just wrong on so many levels.

 

[BugI02]

An ECU's preference for slowing (slightly) and smoothing the closing of the throttle makes heel-toeing much more of an adventure, too

Edit: to avoid confusion, when I talk about the opening or closing of the throttle I mean the triggering of the desired result in fuel flow to the engine, not simply the speed with which the mechanical parts in the circuit can be moved. My apologies if this is too inexact but usually we are talking about acheiving the desired results in a timely manner and less about how we actually got there

 

[russc2542]

An ECU's preference for slowing (slightly) and smoothing the closing of the throttle makes heel-toeing much more of an adventure, too

Edit: to avoid confusion, when I talk about the opening or closing of the throttle I mean the triggering of the desired result in fuel flow to the engine, not simply the speed with which the mechanical parts in the circuit can be moved. My apologies if this is too inexact but usually we are talking about acheiving the desired results in a timely manner and less about how we actually got there

Given the range of knowledge/experience of the people involved, some generality is to be expected. not many want to read a patent or engineering paper.