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      11-19-2018, 08:59 AM   #1
CornM3
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Exclamation S/C WOT cuts power?

Hey guys so I recently swapped pulleys and belt on my s/c but when doing some pulls up top my engine stops giving power as if I just let off the gas pedal completely.
Example
I’m in 3rd gear, I do a pull it’s nice and smooth and pulls hard, I shift at about 8300 and it shifts fine into 4th but then it just cuts off at like 7800-8000 rpm as if I just let completely off the throttle but I don’t.
But I noticed if I let off the throttle when it cuts off and put my foot back down it keeps going.
I did a 4th gear pull and it did the same in 5th. And sometimes it even does it in the gear that I’m doing the pull.
I tried another test where I left off the pedal then shift and then reapply pressure and it doesn’t cut off.

I’m not sure what could be causing this, my guess is maybe my plugs need to be gapped tighter since it’s getting colder? Or possibly belt slip? But I don’t think belt slip would cause complete loss of engine power will it?
Afr is reading mid 11s on wot

Last edited by CornM3; 11-19-2018 at 03:24 PM..
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      11-19-2018, 09:01 AM   #2
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What SC are you running? Did you change the pulley size and not change the SW going with the SC? Could be a sw issue where the pressure release waste gate is opening before redline.
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      11-19-2018, 09:08 AM   #3
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Quote:
Originally Posted by Mvy View Post
What SC are you running? Did you change the pulley size and not change the SW going with the SC? Could be a sw issue where the pressure release waste gate is opening before redline.
I’m running the evolve kit, and according to the tuner I don’t need to change my tune since it’s suppose to adapt to it
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      11-19-2018, 11:12 AM   #4
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Sounds exactly like what happens when your fuel system is maxed out.
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      11-19-2018, 03:23 PM   #5
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Quote:
Originally Posted by Green-Eggs View Post
Sounds exactly like what happens when your fuel system is maxed out.
And if I’m correct there’s nothing really out there for fuel system upgrades right?
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      11-20-2018, 08:36 AM   #6
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If you changed your pulley size, im not buying that the tune will adapt to it. The evolve kit is supposed to be able to run on the stock fuel pump I believe, so you might just have one that is failing. Do you hear any blow off at the time you lose power? Probably hard to hear at WOT.
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      11-20-2018, 05:49 PM   #7
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Quote:
Originally Posted by Mvy View Post
If you changed your pulley size, im not buying that the tune will adapt to it. The evolve kit is supposed to be able to run on the stock fuel pump I believe, so you might just have one that is failing. Do you hear any blow off at the time you lose power? Probably hard to hear at WOT.
Yea I can’t hear the BOV especially since they’re not atmospheric, but according to my boost gauge I am going into vacuum when it happens so I would say it’s safe to assume it is releasing the boost.
I’m going to log it soon and see what’s going on, but I agree the tune has something to do with it, time will tell
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      11-20-2018, 06:20 PM   #8
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what was the original pulley size vs the smaller one that you put on? If you think it is belt slip just swap pulleys back.
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      11-20-2018, 08:01 PM   #9
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Quote:
Originally Posted by bvrider1 View Post
what was the original pulley size vs the smaller one that you put on? If you think it is belt slip just swap pulleys back.
95 mm was the original I’m now on a 85mm, I’ve swapped belts and the tensioner is pretty tight but it’s not maxed out so I don’t wanna go to much smaller on a belt since then I won’t be able to put on or off, but I don’t think belt slip would cause complete engine power loss could it? I figured it would just cause boost issues? I’m just trying to narrow down possibilities.
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      11-20-2018, 08:28 PM   #10
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Who tuned it for you? Going down 10mm and the tune will adapt?
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      11-20-2018, 08:52 PM   #11
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Quote:
Originally Posted by bvrider1 View Post
Who tuned it for you? Going down 10mm and the tune will adapt?
Evolve, that’s what they been telling me. I thought I would at least need bigger injectors but they said my blue ones would be fine
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      11-21-2018, 01:17 AM   #12
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10mm is a fairly large change in pulley size, I can't imagine this not requiring an injector and/or tune change. What size injectors does your kit run?

Our suggestion would be to log the car and make sure to record boost and air/fuel ratios. Logging this will provide useful data as to whether this is a fueling issue or potentially belt slippage.
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      11-21-2018, 04:34 AM   #13
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Quote:
Originally Posted by BPMSport View Post
10mm is a fairly large change in pulley size, I can't imagine this not requiring an injector and/or tune change. What size injectors does your kit run?

Our suggestion would be to log the car and make sure to record boost and air/fuel ratios. Logging this will provide useful data as to whether this is a fueling issue or potentially belt slippage.

I agree and I’m running the blue Bosch injectors, I’m going out of town for a bit but I plan on logging when I get back
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      11-21-2018, 05:16 AM   #14
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I have same problem with AA but it's ok now . Because lost boost at high rpm and the injector keep working .A/F ratio come to 10 . so rpm keep at 7000 with full throttle .
check boost and A/F .I think belts and the tensioner is ok .
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      11-21-2018, 12:32 PM   #15
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I don't think logging AFR will tell you much about your fuel system capacity. That's not how Robert discovered the fuel system cut out issue. I asked Robert, and here's what he told me:

"Wow, it's been a long time since I've looked at this. I had to look at the graphs to refresh my memory. I remember I was visiting Simi Valley and Drew came over to pick me up and make some 60-130 runs in early morning winter weather. He said his car was cutting out. According to the data, it was December 10, 2011 -- a nice cold day. I hooked up my BT tool and we used his vBox. You're right, AFR alone wouldn't tell you what was going on with the fuel system. I data logged RPM, throttle position, AFR (both banks), and fuel pressure. We did five runs, and I graphed the data to see what was going on. You could clearly see the RPM cut outs on the graph. Sometimes AFR would go lean, but on at least one occasion it didn't. In all cases, the fuel system dipped to 4-bar (or below) pressure. Only when the fuel system dipped to 4-bar would we see the RPM cut outs. Like I said, usually AFR would get real squirly, but not always. So AFR alone won't tell you the story. If you think your customer is having fuel system issues, I suggest data logging and graphing the same things I mentioned above. Hope that helps."
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      11-21-2018, 12:49 PM   #16
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Quote:
Originally Posted by Green-Eggs View Post
I don't think logging AFR will tell you much about your fuel system capacity. That's not how Robert discovered the fuel system cut out issue. I asked Robert, and here's what he told me:

"Wow, it's been a long time since I've looked at this. I had to look at the graphs to refresh my memory. I remember I was visiting Simi Valley and Drew came over to pick me up and make some 60-130 runs in early morning winter weather. He said his car was cutting out. According to the data, it was December 10, 2011 -- a nice cold day. I hooked up my BT tool and we used his vBox. You're right, AFR alone wouldn't tell you what was going on with the fuel system. I data logged RPM, throttle position, AFR (both banks), and fuel pressure. We did five runs, and I graphed the data to see what was going on. You could clearly see the RPM cut outs on the graph. Sometimes AFR would go lean, but on at least one occasion it didn't. In all cases, the fuel system dipped to 4-bar (or below) pressure. Only when the fuel system dipped to 4-bar would we see the RPM cut outs. Like I said, usually AFR would get real squirly, but not always. So AFR alone won't tell you the story. If you think your customer is having fuel system issues, I suggest data logging and graphing the same things I mentioned above. Hope that helps."
Oh wow thank you for asking and for that information I’ll make sure to graph those, did he mention what he did to fix his fuel system issue?
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      11-21-2018, 06:00 PM   #17
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Quote:
Originally Posted by CornM3 View Post
Oh wow thank you for asking and for that information I’ll make sure to graph those, did he mention what he did to fix his fuel system issue?
Drew (DLSJ5) made his own fuel system. After going through a few vendor fuel systems that didn't work, he made his own. That one works, and it's the one most vendors use today for the high horsepower cars. Drew made one for Sergei in Russia for his 885 whp S65 beast. Drew also made one for one of our customer cars. You can expect to spend about $3500 for a working fuel system regardless of who provides it. At this point, I don't think he's making any more of them.
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      11-21-2018, 11:54 PM   #18
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Quote:
Originally Posted by Green-Eggs View Post
I don't think logging AFR will tell you much about your fuel system capacity. That's not how Robert discovered the fuel system cut out issue. I asked Robert, and here's what he told me:

"Wow, it's been a long time since I've looked at this. I had to look at the graphs to refresh my memory. I remember I was visiting Simi Valley and Drew came over to pick me up and make some 60-130 runs in early morning winter weather. He said his car was cutting out. According to the data, it was December 10, 2011 -- a nice cold day. I hooked up my BT tool and we used his vBox. You're right, AFR alone wouldn't tell you what was going on with the fuel system. I data logged RPM, throttle position, AFR (both banks), and fuel pressure. We did five runs, and I graphed the data to see what was going on. You could clearly see the RPM cut outs on the graph. Sometimes AFR would go lean, but on at least one occasion it didn't. In all cases, the fuel system dipped to 4-bar (or below) pressure. Only when the fuel system dipped to 4-bar would we see the RPM cut outs. Like I said, usually AFR would get real squirly, but not always. So AFR alone won't tell you the story. If you think your customer is having fuel system issues, I suggest data logging and graphing the same things I mentioned above. Hope that helps."
First of all, you are Robert or Robert by proxy. It's pretty obvious in nearly every post you make.

Second of all, if it's going lean toward the top end, it's an indication that either the fuel pump or injectors can't supply enough fuel. We've tuned hundreds and hundreds of kits from almost every brand and every level and know a thing or two. If you have better advise instead of trying to downplay my advise, then please share it. Are you saying not to monitor the AFR and boost as an initial check? For all we know 10mm could be 5 PSI more and far exceeding the injectors, which is why I inquired about injector size.

No where was it mentioned that this is the only thing that should be logged. Kits running out of fuel religiously go lean on top. Go put too much E85 in an FI M3 and watch what happens. Look at johneastvolds dynos with 10psi and E85.

It would have to go VERY lean to cut out abruptly, normally it will lean out more and more as it approaches redline without cutting out (into the 13s while the target is low 12, depending on boost and fuel used of course). A 10mm change in pulley size is not small, so I stand by the statements previously said to monitor AFR and Boost, these are the first two things that should be done. It's not the full story, its the beginning of the story.
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      11-22-2018, 09:19 AM   #19
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Quote:
Originally Posted by BPMSport View Post
First of all, you are Robert or Robert by proxy. It's pretty obvious in nearly every post you make.

Second of all, if it's going lean toward the top end, it's an indication that either the fuel pump or injectors can't supply enough fuel. We've tuned hundreds and hundreds of kits from almost every brand and every level and know a thing or two. If you have better advise instead of trying to downplay my advise, then please share it. Are you saying not to monitor the AFR and boost as an initial check? For all we know 10mm could be 5 PSI more and far exceeding the injectors, which is why I inquired about injector size.

No where was it mentioned that this is the only thing that should be logged. Kits running out of fuel religiously go lean on top. Go put too much E85 in an FI M3 and watch what happens. Look at johneastvolds dynos with 10psi and E85.

It would have to go VERY lean to cut out abruptly, normally it will lean out more and more as it approaches redline without cutting out (into the 13s while the target is low 12, depending on boost and fuel used of course). A 10mm change in pulley size is not small, so I stand by the statements previously said to monitor AFR and Boost, these are the first two things that should be done. It's not the full story, the the beginning of the story.
That’s why I thought it was odd I didn’t need injectors since I am making about 9.5psi I was at 6.5 before, and johns wasn’t cutting out just leaning out like you mentioned, I think John posted about a new fuel-it fuel system but never installed, when I get back in a couple weeks I’ll get some logs but I’m pretty sure you’re right about it being my injectors, I’m running 93 with hopes of adding some e85 when she’s running right, I had e85 with the 6.5psi and it ran fine
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      11-22-2018, 04:21 PM   #20
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If a banned person posts by proxy, then does the ban extend to the proxy?
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