Remote turbo with a bypass valve... doable?

[deevergote]

I was toying with the idea of installing a remote turbo on a car with an electronic bypass valve that would redirect the exhaust flow down an alternate exhaust pipe for "normal" use. Hook the valve up to a switch that also controls a dual-map ECU, so you'll essentially be able to turn the turbo "on" whenever you want. I'm just not sure the bypass valve would be effective enough.

I know it's probably a silly idea, but I'm curious to see what more experienced people have to add to it. It would be pretty cool if it were feasible!

[Domesticated]

Just run a big waste gate. That's literally what a waste gate does. If you want a turbo without losing fuel economy, run a bigger turbo that doesn't kick in until you're out of the normal driving range.

[93redcb7]

I was toying with the idea of installing a remote turbo on a car with an electronic bypass valve that would redirect the exhaust flow down an alternate exhaust pipe for "normal" use. Hook the valve up to a switch that also controls a dual-map ECU, so you'll essentially be able to turn the turbo "on" whenever you want. I'm just not sure the bypass valve would be effective enough.

I know it's probably a silly idea, but I'm curious to see what more experienced people have to add to it. It would be pretty cool if it were feasible!

you might be able to do it with an electronic cut out

[sonikaccord]

Holset HE351VE...It's a variable geometry turbo that has an electronically controlled turbine A/R ratio. Run it wide open (high A/R) during normal driving, then close it when you want a quick and hard spool.

[dbsharp]

tuning for a variable geometry turbo is difficult. hx 35 spools up slow enough where normal driving you only hear it a little and don't really go into boost.... and they are pretty cheap.

[deevergote]

Probably pretty pricey, too!

I'm thinking of a total ghetto budget setup. Not that I even intend to do it, but the idea intrigues me. Hell, my very first forum question 15 years ago was "can you turn a turbo off?"

That's true about the wastegate. Electronically adjustable wastegates exist, right?

The electric cutout is what I had in mind, though. Just run an alternate exhaust pipe from the cutout through resonators and mufflers... make it as quiet as a normal boring car (I'm imagining this on a Grand Marquis... as it's the most unassuming car I can think of!) With the non-turbo section open, the car is essentially stock.
Flip the switch, which redirects the exhaust from the stock pipe to a turbo (or pair of turbos if we're going dual exhaust), along with switching the ECU to a turbo map... and the beast roars. Goes from like 180hp to 300hp in the flip of a switch. Turbos can dump into hidden glasspacks or something to cut the noise a little... but it'd be loud and obnoxious regardless.

[toycar]

Probably pretty pricey, too!

I'm thinking of a total ghetto budget setup. Not that I even intend to do it, but the idea intrigues me. Hell, my very first forum question 15 years ago was "can you turn a turbo off?"

That's true about the wastegate. Electronically adjustable wastegates exist, right?

The electric cutout is what I had in mind, though. Just run an alternate exhaust pipe from the cutout through resonators and mufflers... make it as quiet as a normal boring car (I'm imagining this on a Grand Marquis... as it's the most unassuming car I can think of!) With the non-turbo section open, the car is essentially stock.
Flip the switch, which redirects the exhaust from the stock pipe to a turbo (or pair of turbos if we're going dual exhaust), along with switching the ECU to a turbo map... and the beast roars. Goes from like 180hp to 300hp in the flip of a switch. Turbos can dump into hidden glasspacks or something to cut the noise a little... but it'd be loud and obnoxious regardless.

running a speed density fuel management system would avoid the need of a "switchable map" which would be the hardest part of all of this.


stole from interwebs:

N Alpha
A relatively simple design, N Alpha systems use only engine speed and throttle angle to calculate the amount of fuel needed by the engine. This system doesn’t measure airflow directly; instead, engine load is assumed based on throttle-angle versus engine rpm. The various load-rpm points make up the computer’s lookup table, with the amount of fuel needed at each point manually programmed by the tuner. N Alpha systems work well on engines that operate primarily at wide-open throttle—such as race cars—but are much less accurate at part-throttle than more sophisticated systems because of their relatively simple fuel map. They generally do not have a closed-loop mode for air/fuel correction, resulting in part-throttle calibration that is crude at best when compared to other systems. This also makes them incompatible with modern catalytic converters. Any significant engine change requires remapping.

Speed Density
Speed Density systems accept input from sensors that measure engine speed (in rpm) and load (manifold vacuum in kPa), then the computer calculates airflow requirements by referring to a much larger (in comparison to an N Alpha system) preprogrammed lookup table, a map of thousands of values that equates to the engine’s volumetric efficiency (VE) under varying conditions of throttle position and engine speed. Engine rpm is provided via a tach signal, while vacuum is transmitted via an intake manifold-mounted Manifold Air Pressure (MAP) sensor. Since air density changes with air temperature, an intake manifold-mounted sensor is also used.

Production-based Speed Density computers also utilize an oxygen (O2) sensor mounted in the exhaust tract. The computer looks at the air/fuel ratio from the O2 sensor and corrects the fuel delivery for any errors. This helps compensate for wear and tear and production variables. Other sensors on a typical Speed Density system usually include an idle-air control motor to help regulate idle speed, a throttle-position sensor that transmits the percentage of throttle opening, a coolant-temperature sensor, and a knock sensor as a final fail-safe that hears detonation so the computer can retard timing as needed.




so basically setup a fuel management system from square one that can read the difference between no boost and boost and manage fuel to air flow accordingly.

no flippable map, one tune.

[Domesticated]

A properly setup tune will be fine, no switch required. A switch may be useful if you run two separate maps where the map is very dense under the high rpms when you'll be boosting, but less dense at lower rpm sacrificing drivability for reliability, then with the non boost map you could have a very dense table around idle and cruising speeds to maximize the smoothness and fuel economy. But still, just run a big electronically controlled wastegate.

[deevergote]

running a speed density fuel management system would avoid the need of a "switchable map" which would be the hardest part of all of this.


stole from interwebs:

N Alpha
A relatively simple design, N Alpha systems use only engine speed and throttle angle to calculate the amount of fuel needed by the engine. This system doesn’t measure airflow directly; instead, engine load is assumed based on throttle-angle versus engine rpm. The various load-rpm points make up the computer’s lookup table, with the amount of fuel needed at each point manually programmed by the tuner. N Alpha systems work well on engines that operate primarily at wide-open throttle—such as race cars—but are much less accurate at part-throttle than more sophisticated systems because of their relatively simple fuel map. They generally do not have a closed-loop mode for air/fuel correction, resulting in part-throttle calibration that is crude at best when compared to other systems. This also makes them incompatible with modern catalytic converters. Any significant engine change requires remapping.

Speed Density
Speed Density systems accept input from sensors that measure engine speed (in rpm) and load (manifold vacuum in kPa), then the computer calculates airflow requirements by referring to a much larger (in comparison to an N Alpha system) preprogrammed lookup table, a map of thousands of values that equates to the engine’s volumetric efficiency (VE) under varying conditions of throttle position and engine speed. Engine rpm is provided via a tach signal, while vacuum is transmitted via an intake manifold-mounted Manifold Air Pressure (MAP) sensor. Since air density changes with air temperature, an intake manifold-mounted sensor is also used.

Production-based Speed Density computers also utilize an oxygen (O2) sensor mounted in the exhaust tract. The computer looks at the air/fuel ratio from the O2 sensor and corrects the fuel delivery for any errors. This helps compensate for wear and tear and production variables. Other sensors on a typical Speed Density system usually include an idle-air control motor to help regulate idle speed, a throttle-position sensor that transmits the percentage of throttle opening, a coolant-temperature sensor, and a knock sensor as a final fail-safe that hears detonation so the computer can retard timing as needed.




so basically setup a fuel management system from square one that can read the difference between no boost and boost and manage fuel to air flow accordingly.

no flippable map, one tune.

Justin's back!

Wow, I didn't even know all that stuff existed! My thought was simply to use a hacked-together setup, and the only way I could imagine setting things up would be to do an on-boost tune, and an off-boost tune. I'll have to do some more research on those systems you mentioned. I wonder how inexpensively such a thing could be built. It seems like that sort of stuff would only be incorporated into some serious engine management software.

A properly setup tune will be fine, no switch required. A switch may be useful if you run two separate maps where the map is very dense under the high rpms when you'll be boosting, but less dense at lower rpm sacrificing drivability for reliability, then with the non boost map you could have a very dense table around idle and cruising speeds to maximize the smoothness and fuel economy. But still, just run a big electronically controlled wastegate.

Would a big wastegate function the same way as I have in mind? I want to find a way to thoroughly bypass the turbo system, and run through an entirely separate exhaust system. Basically, flip a switch and remove the turbo setup from the equation entirely. In "off boost" mode, the turbo wouldn't be spinning at all. Would a big wastegate allow for enough exhaust flow to do that?

[93redcb7]

Justin's back!

Wow, I didn't even know all that stuff existed! My thought was simply to use a hacked-together setup, and the only way I could imagine setting things up would be to do an on-boost tune, and an off-boost tune. I'll have to do some more research on those systems you mentioned. I wonder how inexpensively such a thing could be built. It seems like that sort of stuff would only be incorporated into some serious engine management software.



Would a big wastegate function the same way as I have in mind? I want to find a way to thoroughly bypass the turbo system, and run through an entirely separate exhaust system. Basically, flip a switch and remove the turbo setup from the equation entirely. In "off boost" mode, the turbo wouldn't be spinning at all. Would a big wastegate allow for enough exhaust flow to do that?

Problem with that is even if you didnt run a spring it wouldnt open until 0 psi(normally there is vacuum) BUT even if you did that, the wastegate would never really close even with 100% pressure against it(will normally double your spring pressure)

[deevergote]

That's what i was thinking. I figured the electronic bypass valve would redirect the exhaust flow sufficiently, if not completely.

[93redcb7]

That's what i was thinking. I figured the electronic bypass valve would redirect the exhaust flow sufficiently, if not completely.

well the way i would think that would work is there would be a electronic bypass just before the turbo and it would completely redirect it away from it, and then there would be a Y pipe that they both go into as your downpipe

[deevergote]

That's exactly what I was thinking. My only concern is that the valve may leak too much to allow the turbo to spool up properly. I've never used such a valve (and I haven't had a turbo car in over 15 years...) so my idea is half-baked at best!

[Domesticated]

An electronically controlled waste gate can open and close when you want it to. You also don't want your turbo to not spin. Your engine will still have to suck air past the turbo and the slower is spinning the more restriction you get. I mean, you would pretty much be spoiling the turbo with your intake instead of the wasted exhaust.

[deevergote]

That's true. I meant to include a bypass valve on the intake side as well. That's the side that I fear won't hold the pressure.