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COBB Pro-Tune vrs Unitronic Stage 2 -- DYNO

Fantom1107

Passed Driver's Ed
I installed a USP downpipe over the weekend and switched over to the Stage 2 Stock MAF 93 map. I am using the stock airbox right now. There is pretty significant increase over the Stage 1 high boost, overall pretty happy. I'm currently slipping 1st-3rd due to snow tires, but I'm noticing lower boost levels during acceleration and then a boost surge when I let off throttle.

Is the lower target boost pressure due to the TCS kicking in? I don't think I was slipping much in the datalog14 file and this was in 3rd. On the stage 1 map I was getting maybe 1psi of surge after letting off throttle, now I have 5.5psi. Is this surge normal or sign of bad DV?

Here is the datalog:
http://datazap.me/u/import11/stage-2-pulls-winter-tire-slip?log=0&data=3-19
 
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corman1313

Ready to race!
I would try the DV+ first, that should solve your issue and hold boost better all around. It's boost by gear and yes you aren't going to get 18psi right away, you'll have to get through the band a bit to get it but I believe the DV+ will help for sure.

If traction control was kicking power the light would blink

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hbrown0509

Go Kart Champion
I would try the DV+ first, that should solve your issue and hold boost better all around. It's boost by gear and yes you aren't going to get 18psi right away, you'll have to get through the band a bit to get it but I believe the DV+ will help for sure.

If traction control was kicking power the light would blink

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What he said. Could have crapped out the DV with all the higher boost.


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Fantom1107

Passed Driver's Ed
I would try the DV+ first, that should solve your issue and hold boost better all around. It's boost by gear and yes you aren't going to get 18psi right away, you'll have to get through the band a bit to get it but I believe the DV+ will help for sure.

If traction control was kicking power the light would blink

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If the DV were bad, wouldn't the actual boost be way less than the target boost though? From the logs it seems like the turbo is close to matching what is being requested. I'm more concerned about the large spike during throttle off. Just tying to understand a little more and don't want to go spend $150 if I don't need to.
 

corman1313

Ready to race!
If the DV were bad, wouldn't the actual boost be way less than the target boost though? From the logs it seems like the turbo is close to matching what is being requested. I'm more concerned about the large spike during throttle off. Just tying to understand a little more and don't want to go spend $150 if I don't need to.
The DV isssue has been beat all over the forum, I'm very confident this should solve your issue, your parts are not capable of handling what you are throwing at them so they need an upgrade. What is the point of a DV? It's to release pressure when you let off the throttle so it's not just about holding boost while getting on it, its also how that pressure is released when you let off the throttle which is where your concern is. The DV is not responsible for hitting target boost, the wastegate does that. If the DV was fully trashed then yes maybe you wouldn't hit full boost but we aren't talking about leaking while on the throttle.
Should be able to pick up a new DV+ for 130 and a used for less than 100.

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Fantom1107

Passed Driver's Ed
The DV isssue has been beat all over the forum, I'm very confident this should solve your issue, your parts are not capable of handling what you are throwing at them so they need an upgrade. What is the point of a DV? It's to release pressure when you let off the throttle so it's not just about holding boost while getting on it, its also how that pressure is released when you let off the throttle which is where your concern is. The DV is not responsible for hitting target boost, the wastegate does that. If the DV was fully trashed then yes maybe you wouldn't hit full boost but we aren't talking about leaking while on the throttle.
Should be able to pick up a new DV+ for 130 and a used for less than 100.

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Ah, thanks for the clarification. I was getting the wastegate and DV mixed up. This is my first turbo car, so still learning the basics.
 

corman1313

Ready to race!
Ah, thanks for the clarification. I was getting the wastegate and DV mixed up. This is my first turbo car, so still learning the basics.
The wastegate is what diverts exhaust gases around the turbine and out the exhaust to protect the turbine, it is responsible for holding boost because pressure needs to be met before the wastegate opens and dumps gases, your tune will tell the wastegate when to open and close.

The Diverter valve is responsible for the pressure in the intake tract after you let off the throttle, there is air trapped in the system which would return back to the compressor and could damage it because throttle plate has been closed, so the DV will direct that trapped air back into the system and away from the compressor. We have a recirculating system which means that trapped air is sent back into the intake tract and not to the atmosphere like other blow off valves. If you were to install an atmospheric blow off valve and not tune for it you will run rich because the ecu is expecting that air to come back into the system and it would supply the fuel for it causing the engine to run rich.
Hope that helps a little

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