New BW EFR Turbo Thread
I think a lot of people don't realize that when you hit fuel cut, be it by ECU load control or by fuel starvation, all the air that was already compressed by the turbo has more volume going through the motor in this scenario then it would if it got used in combustion, this air flows through the motor (if the throttle stays open) and actually speeds up the turbo. And if your running the turbo close to max then it just pops.
That doesn't sound right. The ideal (stoichiometric) gasoline combusion equation is:
2C8H18 + 25O2 ~> 16CO2 + 18H2O
This means that the ratio of combustion product molecules to incoming air-fuel molecules is about 1.3. The reactants and the products are essentially all in a gaseous state, so the volume taken up by the combustion products is at least 30% higher than the reactants (air and fuel) without taking into account the higher temperature of the combustion products. We deal with imperfect combustion where the ratio is not as high as 1.3, but nevertheless, the combustion products are going to occupy substantially more volume than if the incoming air charge just passed through the motor.
What I might be inclined to believe is that if the BOV somehow were able to get open during fuel-cut, then the existing exhaust manifold pressure combined with the lack of any back pressure in the charge piping might allow an overspeed event. This would essentially be the same as an intercooler pipe blowing off at WOT with high pressure on the turbine wheel.
Anyhow, I'm curious to see the logs and to understand exactly what happened.
2C8H18 + 25O2 ~> 16CO2 + 18H2O
This means that the ratio of combustion product molecules to incoming air-fuel molecules is about 1.3. The reactants and the products are essentially all in a gaseous state, so the volume taken up by the combustion products is at least 30% higher than the reactants (air and fuel) without taking into account the higher temperature of the combustion products. We deal with imperfect combustion where the ratio is not as high as 1.3, but nevertheless, the combustion products are going to occupy substantially more volume than if the incoming air charge just passed through the motor.
What I might be inclined to believe is that if the BOV somehow were able to get open during fuel-cut, then the existing exhaust manifold pressure combined with the lack of any back pressure in the charge piping might allow an overspeed event. This would essentially be the same as an intercooler pipe blowing off at WOT with high pressure on the turbine wheel.
Anyhow, I'm curious to see the logs and to understand exactly what happened.
Ok so it wasn't related to fuel at all!
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From: Welly NZ
HA! I was even thinking when you posted the turbine rpm plot that all I could imagine causing that was a pre-turbo blockage (ie, draw through TB type setup) but never considered the possibility that something like this was happening. Awesome!
Fun fact, people have installed an "extra" throttle pre-turbo to keep shaft rpm up on shifts/part throttle because of this phenomenon. Cool to see actual logging to see exactly what effect it has
Fun fact, people have installed an "extra" throttle pre-turbo to keep shaft rpm up on shifts/part throttle because of this phenomenon. Cool to see actual logging to see exactly what effect it has
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From: Croatia
renault was using that on R5 turbo rally cars, and I think even BMW and Renault did it in F1..
I tried a K&N but the collapse just happened faster. I think the issues was that the coupler rubs against the shifter cables (Evo X) deforming it and it was weakened by heat.
I replaced the coupler with a aluminum elbow and all is good now.
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From: Tri-Cities, WA // Portland, OR
I'm using the largest Blitz SUS filter, not much of a filter lol.
I tried a K&N but the collapse just happened faster. I think the issues was that the coupler rubs against the shifter cables (Evo X) deforming it and it was weakened by heat.
I replaced the coupler with a aluminum elbow and all is good now.
I tried a K&N but the collapse just happened faster. I think the issues was that the coupler rubs against the shifter cables (Evo X) deforming it and it was weakened by heat.
I replaced the coupler with a aluminum elbow and all is good now.
Get yourself a MASSIVE air filter. I think mine is almost 12" long and 8" in diameter tapering to 6".
My friend's Supercharged G8 was doing that to his 90* elbow as well. As a temporary (that became permanent) fix was to just cut some PVC that size, clean it off real well, and stick it in there. Hasn't had any issue since.
I wouldn't recommend it though.
you need a truck air filter!
I wouldn't recommend it though.
you need a truck air filter!
Last edited by cerevo; Sep 14, 2015 at 10:42 AM.
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I agree I need to do something about the intake situation but I'll need to have a custom intake and heat shield made to be able to fit a larger filter while having the MAF is a good location. The intake itself it's probably 3' long all together, it's a Evo X with a bottom mount turbo so not much I could do to change that but once I have a intake made then the actual piping would be shorter.
The K&N I tried was 9" tall with a 6" inlet so it wasn't exactly small. The Blitz one is 6" tall and also has a 6" inlet and you can pretty much see through it....but I agree, I'll do something about the lengthy piping and try to fit like a 15" long filter so the piping would be like 20" from filter to turbo.
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Well if he changed from a 3" to a 3.5" and didn't retune for the larger MAF housing then his tune must have been super rich on the 3" and then yes I could see it gaining a good amount of power.
The K&N I tried was 9" tall with a 6" inlet so it wasn't exactly small. The Blitz one is 6" tall and also has a 6" inlet and you can pretty much see through it....but I agree, I'll do something about the lengthy piping and try to fit like a 15" long filter so the piping would be like 20" from filter to turbo.
The K&N I tried was 9" tall with a 6" inlet so it wasn't exactly small. The Blitz one is 6" tall and also has a 6" inlet and you can pretty much see through it....but I agree, I'll do something about the lengthy piping and try to fit like a 15" long filter so the piping would be like 20" from filter to turbo.