I have a small motor home that just can't get over the hump at high altitudes. I'm certain that if it had its sea level rated power that there would be no problem. How I want to do this includes fooling the OEM sensor/electronics into thinking the engine is at sea level so that there is not a need for anything other than just the addition of the turbocharger.

I know this is not the way it's done under any other boost conditions but it seems to me that a little creative thinking should overcome the obvious problems. I start by thinking of the engine being in a pressurized box with a relief valve set to 14.7 psi. Not reasonable but it's not necessary for the entire engine to be enclosed. So, limit the size of the "box" to the size of those components necessarily involved. Somebody please take it from there...

 

Basically just the intake tract like any other boosted setup. The rest will only benefit from elevation.

 

So, I know the MAP sensor has to "see" 14.7 psi. I could simply remove the sensor and connect the wiring to the proper voltage to indicate 14.7 psi since the system will essentially always be experiencing 14.7 psi. (I will have a gauge to monitor the actual operating pressure in case things go south.)

 

I don't think your approach is the best.... by bypassing excess air from the compressor it would be very hard on the turbo itself. You'd be better off building a conventional turbo setup, and limiting boost to the lowest you can. Many engines will tolerate a few psi on the stock fuel system, and ecu without too much issue. What engine are we talking about?

 

You gotta give us a little more info on the engine . Manufacturer? Size? Trying to trick the sensors really won’t do anything other than waste fuel lol. Like the eBay iat resistor which claims 20hp which is bull crap lmao.

 

This is a 2000 Winnebago Rialta HD. The drive train is a VW Eurovan with a VR6 12-valve and the dual-path, “high” torque intake manifold. The transmission is an automatic 4-speed.

So that you know a little about my level of understanding, I am a quintessential ‘60s car guy. If it has a carburetor and a points-type distributor on it I can fix it. I have only a general understanding of late model electronics. Before Windows I was an expert at DOS and GW Basic. I can find my way around in Visual Basic. I’ve been studing turbochargers for some time including the reading of one textbook.

 

That’s probably the last decent vw engine that they built lol! I’m not a fan of the new stuff. One of my friends has the fastest vr6s out there it’s turboed and runs in the 8s . I’ll let you know what kinda set up he runs for the ecm. You probably won’t need all the options he has

 

This is way different from what you guys usually do. The only "boost" I want is what it takes to bring the intake manifold up to atmospheric pressure in Houston, Texas. The vehicle's electronics already know how to handle that. So, it seems to me that what's needed is a boost controller involving a rotary servo motor, a pressure sensor, and an Arduino. I can build it if that would work. We don't know the response time of such a system but my guess is that it's fast enough for the way the motor home is driven.

I live at 1200 ft and mostly travel to higher elevations (hence this post) so there will essentially always be at least 1/2 psi boost ranging up to 5 psi as I take the high road over the continental divide. The boost level would change over a long period of time. The ideal situation would be to run the turbo at a constant speed (reflecting 5 psi boost at ~4500 rpm) and let the waste gate modulate the pressure on a no lag basis. I don't know enough about turbochargers to know if that would work but if the failure mode of the waste gate is to open then I don't see there would be anyway that the engine could get damaged.

 

My MatchBot is http://www.turbos.borgwarner.com/go/JGRS8B

 

I'll tell you that if you run a turbo with the outlet vented to atmosphere (bypassed to limit boost to 0 psig) you will over speed it, and kill it. Using your method to control a wastegate is a much better idea, you just need to find a way to limit it to 14.06 psia

 

You would be much better off to just set up the turbo for 5psi all the time and make it reliable. If you really do drive the thing gently most of the time it probably won't spool except under high load conditions. 5psi even at sea level should not be particularly hard on parts.
Your making a simple thing more difficult.

 

I appreciate the insight. What about reprogramming the ECU, larger injectors, new MAP, etc? I haven't mentioned the stock compression ratio is 10:1 (sorry). It already wants 93 octane. I don't want to pull the head to install a plate. I think methanol injection would be needed under load...

 

My thought was to put a pressure transducer ahead of the throttle body and have the Arduino compare that to 14.7 and in turn signal the servo motor to open/close the waste gate until 14.7 is reached. As Ben says I'd risk running the the turbo over the limit. What would be the minimum boost needed to prevent that from happening?

 

Would it work any better to have the boost control modulate the BOV? The way it would work is the BOV would be open to some degree all the time except at 12000 ft. where I would need the full 5 psi boost. I guess there would have to be two BOVs...

 

Actually it was me who said that, and there isn't a min boost number, it just needs load. It's like putting your car in neutral, with no rev limiter and holding the throttle to the floor, but worse. How long would you expect it to live? The bov is the same scenario as I was talking about... controlling boost from the intake side is a bad idea with a turbo... period. You may get away with it with a centrifugal supercharger, but not on a turbo. You need to limit boost by managing the turbine. Like I said before, most stock fuel systems, and engine management have enough reserve to deal with a few psi of boost, and most have knock retard to deal with limited amounts of octane issues.

 

There are two of us pointing you in the right direction..... A typical turbo setup with very limited boost (a couple psi). The only real limitation is in how well you can control the wastegate.

 

And if you do the math, 5000' is 12.228 psia, so there's a couple psi right there.

 

I would think a boost a pump would be enough to provide the extra fueling you need, but I don't know enough about the stock fuel system on that to say for certain. Im almost positive a drop in chip could be burned by a tuner to handle the extra air and fuel flow. That engine is common enough there is probably someone who specializes in tunes close by or can set one up mail order. Keep it as simple as possible, do your best to allow the turbo system to work as intended.
If your already being forced to run premium fuel due to knock at that compression you may have to run water meth, but the tuner may be able to add enough fuel and remove enough timing to get the thing to be happy.

 

So, a little bitty turbo pushing a minimum of 2 (?) psi and a maximum of 5 psi. Windshield washer fluid injection (50/50, no soap) and I’m on my own for the boost control...

I have a complete turbo system from an ‘88 Turbo Coupe and I have an excellent running ‘86 Turbo LeBaron that needs a main bearings. Would either of these be suitable for the VW? (If someone would point me to a compressor map of either of these I would appreciate it.)

 

You could use a wastegate with a really light spring and a manual boost control to turn it up in the mountains.