Fun...damental flaw in this half ass'd design

[jdwk]

So as anyone with a CAI can attest, our bypass isn't quite cutting it to keep backpressure off the compressors blades.

Call me crazy, but the best part of my day is making some pedestrian fall off the sidewalk when I let the turkey out of its cage.

However, I think all of our "kill the turkey" threads are pretty over-complicated.

If we'd do a little homework, we'd notice that our WGA is connected to a vacuum line connected straight to our intake manifold. If we look at a real turbocharged car, say an A4 2.0T for instance, we'd notice that WGA is connected to a nipple just off the compressor housing.

So when we let off the gas post boost, our throttle closes, vacuum goes to 0 or less psi and our wastegate closes right back up. Then the turbo gets some added exhaust side pressure on the turbine translating to more pressure against a closed throttle plate, making for some ridiculous turkey noises and a slight unsettling of the engine as it tries to pressurize and already pressurized system.

It doesn't take a PhD to realize this is a retarded waste of energy. If we simply actuated the wastegate with pressure in front of the throttle plate, the wastegate would hold open until the exhaust expelled which would decrease if not kill the turkey, but more importantly kill the jerky response of quickly lifting the the throttle under boost.

So the reason I am posting is how do we get a vacuum line off the cold pipes. I've been looking around and there are some silicon couplers with tubes off of them, but I haven't found anything with the 1/8" we would need. We could get a nipple welded to a cold pipe and maybe that's the best option, but seems like this should not have been the first time anyone has suggested a "crazy" idea like this.

After all, the Protege isn't the first or last car turbocharged.

 

[livelyjay]

You might be right, might be wrong. Those other cars might have other design considerations that allows the WG to stay open longer. For the MSP, if you keep the WG open longer it will take that much longer to spool up and fill the intake system with air. Since the recirc air is already metered, the ECU might dump in too much fuel and you'll bog down.

I used to have a 2003 Lancer OZ and put a turbo kit on it. That configuration was also recirc with a MAF. The recirc valve was installed about 6 inches from the throttle body and routed back to the intake, inbetween the turbo and the MAF, with a 1" hose. So when the TB plate closed, the turbo was still spinning so it sucked the recirc air through that 1" pipe and put it back through into the intercooler. Worked great.

The MSP recirc is putting the air back on the pressurized side of the turbo, the valve is pretty far from the TB with a small hose and it's weak to begin with, so the system just has a hard time dissipating the extra air.



Actually .... now that I look back at what you read and what I wrote, you might be right. If you stop the turbo from spinning, the higher pressure from the TB side will push the air to the lower pressure post turbo until the pressures equalize. Might be worth trying. You should be able to cut a hole in the cold pipe, install a 1/8" brass nipple, seal it with RTV, then run that to the WG. Unfortunately I have a stock air box, so I can't hear my turkey any ways, but I plan on changing that soon.

 

[yudkib]

interesting theory, but i dont think it works. most people who want a boost only reference will either drill and tap their turbo housing (cant blame you if you dont want to do that), weld on a nipple, or find a coupler with a barb fitting on it (they do make these - but dont remember where). unfortunately, i dont think the turkey goes away that easily. the issue is more related to the 5/8" BPV port being too small, and the pressure too low to properly force and keep the valve open. its just poor design.

theres also a nipple i found on the bottom of the SMIC... i dont know why but i swear no one knows its there. now, im not sure id use that permanently -- oil blowby can accumulate down there, and it could gum up the hose and cause you to over boost. if you want to test your theory, that might be the spot to do it.

 

[yudkib]

Actually .... now that I look back at what you read and what I wrote, you might be right. If you stop the turbo from spinning, the higher pressure from the TB side will push the air to the lower pressure post turbo until the pressures equalize. Might be worth trying. You should be able to cut a hole in the cold pipe, install a 1/8" brass nipple, seal it with RTV, then run that to the WG. Unfortunately I have a stock air box, so I can't hear my turkey any ways, but I plan on changing that soon.

its not moving the air anywhere, its just allowing more pressure on the turbine side to escape. the pressure on the turbine side is what drives the compressor. so if theres no turbine pressure, the compressor wont compress.

 

[StealthWyvern]

Your talking about doing this....
http://www.frsport.com/Turbo-Quick-Tap-Fitting-for-Boost-Source_p_7854.html

 

[ND4MSP]

That's a nice little peice of hardware

 

[Ricktalife]

Hmm that's an interesting idea. I happen to have a spare piece of my cold pipe laying around after I relocated the MAF, and I think I have an extra vacuum fitting as well. Could be a nice little project if it works as you say. Though as yudkib stated, I was under the impression that the stock BPV is simply a poor design.

I am actually considering some modifications to make my piping fit better under my bumper, so I just might play around with this while I'm at it.

 

[Tzar177]

Your talking about doing this....
http://www.frsport.com/Turbo-Quick-Tap-Fitting-for-Boost-Source_p_7854.html

I have that peice and its working quite nicely

 

[jmv]

interesting theory, but i dont think it works. most people who want a boost only reference will either drill and tap their turbo housing (cant blame you if you dont want to do that), weld on a nipple, or find a coupler with a barb fitting on it (they do make these - but dont remember where). unfortunately, i dont think the turkey goes away that easily. the issue is more related to the 5/8" BPV port being too small, and the pressure too low to properly force and keep the valve open. its just poor design.

theres also a nipple i found on the bottom of the SMIC... i dont know why but i swear no one knows its there. now, im not sure id use that permanently -- oil blowby can accumulate down there, and it could gum up the hose and cause you to over boost. if you want to test your theory, that might be the spot to do it.

You are correct... When I upgraded my intercooler, it came with a BoostSciences Bypass valve, which has 1" fittings, as well as 1" fittings on the intercooler and intake piping. Viola, no more compressor surge (except for when my wastegate actuator diaphragm went bad).

I couldn't say if the OP's idea would work or not, but I can tell you that simply letting more air through the BPV system fixed the problem for me.

 

[jdwk]

Your talking about doing this....
http://www.frsport.com/Turbo-Quick-Tap-Fitting-for-Boost-Source_p_7854.html

That's exactly the kind of link I was looking for. I don't have hard pipes yet, just the plastic tubes, which I probably won't drill into, but I'll start looking for some used hard pipes I guess.

 

[yudkib]

or just get a set of pipes and couplers from cx racing... cheaper that way

 

[jdwk]

Do you know what lengths I need, and which elbows off hand? I'll need to put the nipple on the cold side if I don't want to reduce boost pressure.

 

[yudkib]

no. the kits usually come with a few straight pieces, a few 45's, and 0-2 90's depending on the kit. i would be sure to get a kit with at least one 90* piece for the hotpipe.

 

[CustomMSP]

When you switch the pressure source for the wastegate to the hot side it'll activate the wastegate sooner causing less efficient part throttle and a drop in the final boost pressure of about the same amount as the measured drop across the intercooler. If you are at 9spi using the intake manifold source then you'll be at around 7.5psi using the turbo compressor or anywhere else on the hot side piping (assuming that you have an efficient IC).

 

[yudkib]

true, but that assumes youre going on wastegate pressure and cant dial it out with boost control.

 

[mazdaspeedp]

i have a used hotside sls pipe forsale

 

[CustomMSP]

true, but that assumes youre going on wastegate pressure and cant dial it out with boost control.

You're right.

 

[yudkib]

haha its not just about being right - you brought up a good point.

lesson to be learned, wga goes off boost-only, mbc goes in between and you tune boost referencing a reliable gauge on your intake mani.

 

[jdwk]

So I bought mazdaspeedp's SLS pipe and the nipple you linked. So I will report back the change in lift throttle, overall response, etc. I will lose boost so I am not happy about that, but if driveability improves, I will buy cold pipes and do it on the cold side, or maybe an MBC or EBC. Started doing research on the MS, it can do boost control too, just not sure I want to go down that bumpy road on this car.

 

[AzteCypher]

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