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The best thing to use if your considering a EFR is BorgWarner's MatchBot program. It's has all compressor and turbine information for any BW turbo (non OEM) and let's you input your individual engine parameters for a overlay on the compressor and turbine maps.
Both the 8374 and 9174 are rated at a max RPM of 128K. The 9180 is rated to 116k.
In my experience in better to stay at 80% or lower from the max rating for longevity. 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.
I'll post a log later for better visualization.
Oh and to answer your question about how the speed is measured, the sensor does measure at the compressor blades but there's a calculation made that determines shaft speed based on the number of blade revolutions and the number of blades.
T... 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....
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.
Here's 2 views of the same log. Turbo speed is interpreted in 0-5V and there's a mathematical equation to get to RPM. The turbo speed goes from 105K RPM to 124K RPM in like 30 milliseconds.
2.71V= 105,155 RPM
3.25V= 124,870 RPM
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.
You may be right. I just looked at the logs and correlated the fuel cut with the overspeed as seen in the logs.
Is worth to note that the WB sensor is around 4-5 feet after the turbo so there is some lag.
Both the 8374 and 9174 are rated at a max RPM of 128K. The 9180 is rated to 116k.
In my experience in better to stay at 80% or lower from the max rating for longevity.
You said your 8374 turbine exploded right? Can you give us an idea of turbo RPMs you were running regularly and when you were in kill mode? If you were logging at that time.
Also depending on the engine VE and turbo manifold design, I have a feeling turbine speeds is really the limiting factor to sustainable power on these turbos over exhaust manifold pressure and turbine housing a/r. I've been playing with matchbot....these turbos don't seem to be happy running super high boost anyways, which is the time when exhaust manifold pressures would become a big issue to power gains.
So much for what I heard about the 9174 having an MFT turbine. Would you say that the 9174 and 8374 turbines are identical? (They look the same to me.)
Both the 8374 and 9174 are rated at a max RPM of 128K. The 9180 is rated to 116k.
Can you tell me where you got a max speed rating of 128K rpm for the 9174?
That is a tip speed of 610 meters/second at the OD of the compressor wheel. That does not sound right, because every other EFR has a highest speed line at 560 meters/second compressor tip speed.
On the other hand it might be realistic if the turbine wheel is the limiting factor, rather than the compressor wheel.
Matchbot doesn't help with assigning a max turbo rpm because you can put a point into it that is way off the map and it doesn't throw you a warning at all. The only thing I see in matchbot that you could infer a max rpm from is the compressor maps shown, which are the same compressor maps we see everywhere else, that I've already seen. Also, the matchbot I get from turbos.bwauto.com doesn't even show a map for the 9174. I am not looking at this from the standpoint of a shopper looking for a right-sized turbo. I am looking at it from the standpoint of someone who has done all that, they have it on the car, they are logging turbo speed, and they want to know when they've pushed it enough already!
I didn't ask which wheel the sensor was picking up, I mean that's interesting, but all I really am asking about is the shaft rpm.
Who told you that the 9174 is rated max at 128K rpm?
You said your 8374 turbine exploded right? Can you give us an idea of turbo RPMs you were running regularly and when you were in kill mode? If you were logging at that time.
Also depending on the engine VE and turbo manifold design, I have a feeling turbine speeds is really the limiting factor to sustainable power on these turbos over exhaust manifold pressure and turbine housing a/r. I've been playing with matchbot....these turbos don't seem to be happy running super high boost anyways, which is the time when exhaust manifold pressures would become a big issue to power gains.
The limitation of the EFR's def is the turbine speed due to the material.
I was not running the turbo speed sensor on the 8374 but it was def getting over spun, I had the TurboSmart 26 PSI IWG arm preloaded to 12mm (basically bottomed out the threads) and was running 100%WGDC from 6K on. This would result in 33 psi at 9K in 2-3rd, 35 psi at 9K in 4th and 40psi flat in 5th (I never got to 9K in 5th, max was like 7500)
Originally Posted by Talonboost
Can you tell me where you got a max speed rating of 128K rpm for the 9174?
That is a tip speed of 610 meters/second at the OD of the compressor wheel. That does not sound right, because every other EFR has a highest speed line at 560 meters/second compressor tip speed.
On the other hand it might be realistic if the turbine wheel is the limiting factor, rather than the compressor wheel.
Matchbot doesn't help with assigning a max turbo rpm because you can put a point into it that is way off the map and it doesn't throw you a warning at all. The only thing I see in matchbot that you could infer a max rpm from is the compressor maps shown, which are the same compressor maps we see everywhere else, that I've already seen. Also, the matchbot I get from turbos.bwauto.com doesn't even show a map for the 9174. I am not looking at this from the standpoint of a shopper looking for a right-sized turbo. I am looking at it from the standpoint of someone who has done all that, they have it on the car, they are logging turbo speed, and they want to know when they've pushed it enough already!
I didn't ask which wheel the sensor was picking up, I mean that's interesting, but all I really am asking about is the shaft rpm.
Who told you that the 9174 is rated max at 128K rpm?
If you re read what I said, It measures at the compressor to determine shaft speed.
So the 9174 is really not publically available yet. You can get one but its not a straight shot affair at this point and that's why there's no info for it in matchbot.
But we can still know what the turbo maps are, a 9174 is a 91mm compressor from the 9180 and a 74mm turbine wheel from a 8374, so you can use a 9180 compressor map if you are planning on a 9174.
I don't know why Matchbot has that speed rating of 560m/s for the larger turbos, that's incorrect, but it used to have the correct info...you can contact BW or go back on this thread to confirm my max speed statements. I have worked with BW since I got the 9174 and they were the ones that told me the 74mm turbine wheel is rated to 128K rpm max and the 80mm to 116K rpm max.
If you pull up the compressor map for the 7163 in matchbot you'll see what I meant and what all the maps should look like.
The limitation of the EFR's def is the turbine speed due to the material.
I was not running the turbo speed sensor on the 8374 but it was def getting over spun, I had the TurboSmart 26 PSI IWG arm preloaded to 12mm (basically bottomed out the threads) and was running 100%WGDC from 6K on. This would result in 33 psi at 9K in 2-3rd, 35 psi at 9K in 4th and 40psi flat in 5th (I never got to 9K in 5th, max was like 7500)
I see this issue about the EFRs not holding boost a lot actually. Have you considered using a 4 port ebc instead of a 3 port? Thats what honda guys use because they run a 10lb spring in their WG and 10psi boost in 1st gear to hook up, and going up to 50psi in 3rd gear when they get going. Works really well to keep that flapper shut if thats what you want. Will improve spool too.
I see this issue about the EFRs not holding boost a lot actually. Have you considered using a 4 port ebc instead of a 3 port? Thats what honda guys use because they run a 10lb spring in their WG and 10psi boost in 1st gear to hook up, and going up to 50psi in 3rd gear when they get going. Works really well to keep that flapper shut if thats what you want. Will improve spool too.
The problem here is the single port actuator that is supplied with the EFR. It is garbage. Throw it away. Use the Turbosmart two port actuator and use the 3 port solenoid.
couple reasons.. a) its a garbage actuator b)it's single port c) flapper diameter is huge compared to most other IWG housings d) the pivot ratio (mechanical leverage) from the wastegate is very poor.
