Compressor surge under load?
06-09-2016, 10:49 AM
#1
Compressor surge under load?
I posted this in the SOS supercharger thread, but I think some turbo guys may have some good insight on this compressor issue I am having. I'll start from the beginning.
I am having a strange issue with my upgraded supercharger setup. The boost is fluctuating violently between 5-11psi around the 4000 rpm mark at anything above 60% throttle. I have verified this on my mechanical gauge and from the map sensor. The car still accelerates, but does not feel smooth. On three back to back pulls it didn't do it at all and it was night and day difference in the power delivery.
A little background on my tuned setup from last year that had no issues. My original setup was a Novi 1220 with a 3.4 pulley making 11 psi. That setup had a 70mm SOS throttle body, T1r 70mm exhaust, 70mm test pipe, dual Bosch diverter valves, hondata intake manifold gasket, aeromotive 340 pump, AEM fuel regulator, and id1000's. That setup made around 386hp.
With my new setup I am hoping to reach close to the 500whp mark on e85. I sent the s/c to Paxton and they changed the impeller and volute to a 1200. I ordered a 6.6" ASP crank pulley to help with the slip I would be sure to get on the SOS supplied crank pulley. So with the 6.6" crank, I went with a 3.4" s/c pulley (essentially a 2.8" if i still had the SOS crank on). I also upgraded to id1300 injectors, a Tial qrj with -1.5psi spring to replace the Bosch units, added an Urge header, Supertech 95lb springs and titanium retainers, a Walbro 450, replaced ALL fuel lines with -6an conductive core Teflon lines, a fuelab filter, added an AEM fuel rail, changed to the largest orifice in the AEM regulator, added a Saiko Mitchi catchcan setup, and advanced the exhaust 1 degree and retarded the intake 2 degrees to reduce valve overlap with offset keyways. Other mods include cutting hood vents on the right side of the hood and adding a Mishimoto fan shroud/fans for the radiator.
This is the list of all the things I have tried so far with no change.
1) Capped off the Tial and added one of my previous Bosch valves.
2) Tried different vacuum hoses and source locations on the manifold for the Tial.
3) Captured a video of the Tial with a GoPro to verify it wasn’t fluttering.
4) Tried different pulley combinations.
5) Added an extra pulley to eliminate any chance of belt slip.
6) Performed boost leak test and found no leaks.
7) Performed hot compression test with good numbers.
8) Performed hot leak down test with good numbers.
9) Installed the catalytic converter back to add backpressure.
10) Tried 3 different air filters.
11) Returned the cam timing back to stock.
12) Removed the Tial bypass valve to reduce pressure.
13) Added a line from the air injection nipple on the aftercooler to the intake tube for the supercharger.
14) Put the stock exhaust manifold back on.
The only thing that changed the fluctuation was removing the air tube and filter. With nothing on the supercharger, the fluctuations drop to just under a pound. If I add the intake tube (120 degree bend directly off the s/c) with no filter, it still fluctuates. I tried a shorty filter straight off the supercharger and it fluctuated just the same. I find it hard to believe that this supercharger is pulling so much air that it requires no filter. I know of three other guys who ran a VERY similar setup and did not report any problems like this.
I’m no tuner by any means, but I also don’t see how the tune would cause this since the boost is mechanically produced. I’ve attached a few logs for you to review and see what I am describing.
My latest theory stemmed from looking at the compressor map. After looking over the compressor map for the 1200 (vortech Si trim) it looks as though this particular blower is almost too big for our cars. It's funny, but it barley looks as though it should work given our engine specs. I guess when you try to really spin it up, it pushes it over into the surge area.
Given what my data logs show, at 5000rpms, I am consuming 20lbs/min at 7.5psi (1.51 pressure ratio). Graph that on the map at it is right on the edge of the surge line. Unless I am reading or plotting the map wrong.
Here is a log of the flucuation if anyone wants to take a look. https://drive.google.com/open?id=0B3...jc5MkpPWGZud3M And a picture.
This is the log with no air filter. https://drive.google.com/open?id=0B3...Dhwc0pweGEwRGM
I am having a strange issue with my upgraded supercharger setup. The boost is fluctuating violently between 5-11psi around the 4000 rpm mark at anything above 60% throttle. I have verified this on my mechanical gauge and from the map sensor. The car still accelerates, but does not feel smooth. On three back to back pulls it didn't do it at all and it was night and day difference in the power delivery.
A little background on my tuned setup from last year that had no issues. My original setup was a Novi 1220 with a 3.4 pulley making 11 psi. That setup had a 70mm SOS throttle body, T1r 70mm exhaust, 70mm test pipe, dual Bosch diverter valves, hondata intake manifold gasket, aeromotive 340 pump, AEM fuel regulator, and id1000's. That setup made around 386hp.
With my new setup I am hoping to reach close to the 500whp mark on e85. I sent the s/c to Paxton and they changed the impeller and volute to a 1200. I ordered a 6.6" ASP crank pulley to help with the slip I would be sure to get on the SOS supplied crank pulley. So with the 6.6" crank, I went with a 3.4" s/c pulley (essentially a 2.8" if i still had the SOS crank on). I also upgraded to id1300 injectors, a Tial qrj with -1.5psi spring to replace the Bosch units, added an Urge header, Supertech 95lb springs and titanium retainers, a Walbro 450, replaced ALL fuel lines with -6an conductive core Teflon lines, a fuelab filter, added an AEM fuel rail, changed to the largest orifice in the AEM regulator, added a Saiko Mitchi catchcan setup, and advanced the exhaust 1 degree and retarded the intake 2 degrees to reduce valve overlap with offset keyways. Other mods include cutting hood vents on the right side of the hood and adding a Mishimoto fan shroud/fans for the radiator.
This is the list of all the things I have tried so far with no change.
1) Capped off the Tial and added one of my previous Bosch valves.
2) Tried different vacuum hoses and source locations on the manifold for the Tial.
3) Captured a video of the Tial with a GoPro to verify it wasn’t fluttering.
4) Tried different pulley combinations.
5) Added an extra pulley to eliminate any chance of belt slip.
6) Performed boost leak test and found no leaks.
7) Performed hot compression test with good numbers.
8) Performed hot leak down test with good numbers.
9) Installed the catalytic converter back to add backpressure.
10) Tried 3 different air filters.
11) Returned the cam timing back to stock.
12) Removed the Tial bypass valve to reduce pressure.
13) Added a line from the air injection nipple on the aftercooler to the intake tube for the supercharger.
14) Put the stock exhaust manifold back on.
The only thing that changed the fluctuation was removing the air tube and filter. With nothing on the supercharger, the fluctuations drop to just under a pound. If I add the intake tube (120 degree bend directly off the s/c) with no filter, it still fluctuates. I tried a shorty filter straight off the supercharger and it fluctuated just the same. I find it hard to believe that this supercharger is pulling so much air that it requires no filter. I know of three other guys who ran a VERY similar setup and did not report any problems like this.
I’m no tuner by any means, but I also don’t see how the tune would cause this since the boost is mechanically produced. I’ve attached a few logs for you to review and see what I am describing.
My latest theory stemmed from looking at the compressor map. After looking over the compressor map for the 1200 (vortech Si trim) it looks as though this particular blower is almost too big for our cars. It's funny, but it barley looks as though it should work given our engine specs. I guess when you try to really spin it up, it pushes it over into the surge area.
Given what my data logs show, at 5000rpms, I am consuming 20lbs/min at 7.5psi (1.51 pressure ratio). Graph that on the map at it is right on the edge of the surge line. Unless I am reading or plotting the map wrong.
Here is a log of the flucuation if anyone wants to take a look. https://drive.google.com/open?id=0B3...jc5MkpPWGZud3M And a picture.
This is the log with no air filter. https://drive.google.com/open?id=0B3...Dhwc0pweGEwRGM
Last edited by rmerchant3; 01-06-2017 at 06:31 AM.
06-10-2016, 12:23 AM
#3
If you are experience surge at a particular rpm point, the only ways to eliminate it is to reduce the boost at that point or make the engine more efficient at that point (so it can consume the air that the compressor is supplying) - cams, head porting, extra capacity - anything that will improve the engine's ability to pump air at that rpm point.
Obviously it is a lot easier to do with a turbo, which with electronic control of the wastegate, you can actually tailor the boost curve to match the efficiency of the engine.
From what you are experiencing, it would seem that you are correct that the supercharger is too big and is giving the engine more air than it can deal with at that rpm point, so you get a reversion and thus the surge as the supercharger is working against itself until the engine is working hard enough that it can consume the air the supercharger is giving.
Matching turbos / superchargers to an engine is a fine art. Here in the UK, 2.0 litre YBs (the Cosworth engines) HATE GT35s, they surge their tits off, unable to have full boost until over 5000rpm, but the Evo boys love them on their 2.3-2.4 stroker engines, where the extra capacity means that these engines can take more flow at lower rpm points.
Obviously it is a lot easier to do with a turbo, which with electronic control of the wastegate, you can actually tailor the boost curve to match the efficiency of the engine.
From what you are experiencing, it would seem that you are correct that the supercharger is too big and is giving the engine more air than it can deal with at that rpm point, so you get a reversion and thus the surge as the supercharger is working against itself until the engine is working hard enough that it can consume the air the supercharger is giving.
Matching turbos / superchargers to an engine is a fine art. Here in the UK, 2.0 litre YBs (the Cosworth engines) HATE GT35s, they surge their tits off, unable to have full boost until over 5000rpm, but the Evo boys love them on their 2.3-2.4 stroker engines, where the extra capacity means that these engines can take more flow at lower rpm points.
06-10-2016, 03:58 AM
#4
What pulley setup did you run?
If you are experience surge at a particular rpm point, the only ways to eliminate it is to reduce the boost at that point or make the engine more efficient at that point (so it can consume the air that the compressor is supplying) - cams, head porting, extra capacity - anything that will improve the engine's ability to pump air at that rpm point.
Obviously it is a lot easier to do with a turbo, which with electronic control of the wastegate, you can actually tailor the boost curve to match the efficiency of the engine.
From what you are experiencing, it would seem that you are correct that the supercharger is too big and is giving the engine more air than it can deal with at that rpm point, so you get a reversion and thus the surge as the supercharger is working against itself until the engine is working hard enough that it can consume the air the supercharger is giving.
Matching turbos / superchargers to an engine is a fine art. Here in the UK, 2.0 litre YBs (the Cosworth engines) HATE GT35s, they surge their tits off, unable to have full boost until over 5000rpm, but the Evo boys love them on their 2.3-2.4 stroker engines, where the extra capacity means that these engines can take more flow at lower rpm points.
Obviously it is a lot easier to do with a turbo, which with electronic control of the wastegate, you can actually tailor the boost curve to match the efficiency of the engine.
From what you are experiencing, it would seem that you are correct that the supercharger is too big and is giving the engine more air than it can deal with at that rpm point, so you get a reversion and thus the surge as the supercharger is working against itself until the engine is working hard enough that it can consume the air the supercharger is giving.
Matching turbos / superchargers to an engine is a fine art. Here in the UK, 2.0 litre YBs (the Cosworth engines) HATE GT35s, they surge their tits off, unable to have full boost until over 5000rpm, but the Evo boys love them on their 2.3-2.4 stroker engines, where the extra capacity means that these engines can take more flow at lower rpm points.
06-10-2016, 07:43 AM
#5
Seems like classic compressor surge. I would avoid hitting it as much as possible as it's quite destructive on the compressor wheel and bearing system of the blower. I'd say your best option is put on a bigger pulley to reduce the boost level as that's really the only thing you have control over. The surge margin could be improved by modifying the compressor wheel and housing, but of course, that's nothing you can do yourself.
06-10-2016, 09:35 AM
#6
I'm running a 3.0" pulley with the SOS 5.45" crankshaft pulley. I use the first port after the TB for a diverter valve. The one after that is for my EVAP hose. Maybe try restoring your vacuum hoses to stock and hooking up a Bosch DV where your boost gauge is and logging a pull. I would use a new vacuum line just in case there's a pinhole or something.
06-10-2016, 10:54 AM
#7
Seems like classic compressor surge. I would avoid hitting it as much as possible as it's quite destructive on the compressor wheel and bearing system of the blower. I'd say your best option is put on a bigger pulley to reduce the boost level as that's really the only thing you have control over. The surge margin could be improved by modifying the compressor wheel and housing, but of course, that's nothing you can do yourself.
I'm running a 3.0" pulley with the SOS 5.45" crankshaft pulley. I use the first port after the TB for a diverter valve. The one after that is for my EVAP hose. Maybe try restoring your vacuum hoses to stock and hooking up a Bosch DV where your boost gauge is and logging a pull. I would use a new vacuum line just in case there's a pinhole or something.
Your pulley combination is exactly where I get stumped. I know you, Ilovemyhonda, and Donald have all run under 3.2" pulleys with no issues. Why mine is doing this is driving me nuts. That's why I posted in here about the compressor map. It feels like surge, looks like surge and according to the map should be surge....but why if you guys aren't experienceing the same thing? Yours is a 1200 on a stock engine right?
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06-10-2016, 12:57 PM
#8
Yes, 1200 with stock engine with no surging. My logs definitely did not show any boost fluctuation. Maybe try going partially back to stock (remove s/c belt, swap injectors, etc) and seeing if the behavior is the same going WOT.
06-10-2016, 03:17 PM
#9
That is my next step. Would you happen to have any logs of your setup?
06-13-2016, 10:13 AM
#10
Community Organizer
Ok so i am running a novi 1200 with a 6.75 crank pulley and 4'' blower pulley sos tb t1r 70mm rx comptech 4-1 header 3'' intercooler pipe 4.5'' treadstone 860hp core 2 50mm tial Q50 bov's the hot side is set at 6psi the cold 1,5 vetc above 38% throttle 3300 rpm. I modded my oil pump to make sure i have the pressure at that rpm. The problem as stated is this blower is too large for the size of our motors [I run an ap2 drivetrain] so on the low cam there isn't enough lift and duration to allow that air to be released so it starts backing up and when it hits a resonance is will back up the intercooler to the compressor causing great strain on the blower causing the belt too try and slip. So the way i went about it was allowing as much air out as possible and as much in as possible and getting on the high cam is paramount I would think you want as much overlap as possible. This is what i found swapping to air to air from air water cold air = less compression and your surge line goes up i was running 130-140 f cruising and up to 160 f in the Texas summers with my air to air 117f idle is as high as i have seen and in boost i am ambient temp. also find if I run one baffle it help quell the light blurb er i still get near boost tip in under light throttle. Would need more info on your setup to say more
p.s. i am making 16psi at 8500rpm
p.s. i am making 16psi at 8500rpm
