Supercharged - Boost controller ?
Registered User
Joined: May 2004
Posts: 1,049
Likes: 5
From: Myrtle Beach
This is odd. My BLV works and I am limiting it to 16 PSI with a 3.2" pulley running to 9,000rpms. I hit 16psi by about 7,000rpms. In fact, the car stops building boost at 16psi and then slowly drops down to 15 or 14psi by 9k.
Here's the dyno plot:
[attachment=24419:Graham S2K.jpg]
I will have to dig up my data logs to show the boost levels relative to rpms.
Here's the dyno plot:
[attachment=24419:Graham S2K.jpg]
I will have to dig up my data logs to show the boost levels relative to rpms.
Registered User
Joined: Jul 2012
Posts: 9
Likes: 0
Thanks for your post.
Assuming your two engines are the same, what I can see at a glance is you are trimming off the top of the boost from approx 18 psi to 16 psi - which the BLV is designed to do.
He is trying to dump a lot more - and go from 18 psi to 12 psi, and its too small to do all of that. He may find, after he installs a turbo wastegate, that it drops from 18 psi to 4 or 2 psi. Wastegates for turbos are deigned to drop it all, leaving only a very little amount of pressure remain in the system. If he selects the right size of waste gate, it can work.
Waste gates and boost limiters are not the same thing....
Anyway, thanks for your post. If you dig out the boost pressure numbers that correspond to that dyno chart, that would be very helpful.
Assuming your two engines are the same, what I can see at a glance is you are trimming off the top of the boost from approx 18 psi to 16 psi - which the BLV is designed to do.
He is trying to dump a lot more - and go from 18 psi to 12 psi, and its too small to do all of that. He may find, after he installs a turbo wastegate, that it drops from 18 psi to 4 or 2 psi. Wastegates for turbos are deigned to drop it all, leaving only a very little amount of pressure remain in the system. If he selects the right size of waste gate, it can work.
Waste gates and boost limiters are not the same thing....
Anyway, thanks for your post. If you dig out the boost pressure numbers that correspond to that dyno chart, that would be very helpful.
Registered User
Joined: Oct 2008
Posts: 1,582
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From: Tulsa,OK
I have no doubt a wastegate will work if set up properly. I'm assuming your using a standalone ems. I reccomend using a boost solenoid and setting up boost feedback so you can control the wastegate more precisely.
Registered User
Joined: Oct 2008
Posts: 1,582
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From: Tulsa,OK
If I were to do this on my own car I would run the smallest pulley you can without over spinning the blower and bleed off the excess boost pressure above 14-16 psi. This would allow more boost to build earlier thus making more power sooner in the power band. Not sure about the emanage but you can do this with any supercharger.
Joined: Sep 2008
Posts: 1,126
Likes: 7
From: Bay Area, CA
This is odd. My BLV works and I am limiting it to 16 PSI with a 3.2" pulley running to 9,000rpms. I hit 16psi by about 7,000rpms. In fact, the car stops building boost at 16psi and then slowly drops down to 15 or 14psi by 9k.
Here's the dyno plot:
[attachment=24419:Graham S2K.jpg]
I will have to dig up my data logs to show the boost levels relative to rpms.
Here's the dyno plot:
[attachment=24419:Graham S2K.jpg]
I will have to dig up my data logs to show the boost levels relative to rpms.
Belt slippage with 1200 and 3" pulley
Are you using the SOS pulley? Maybe you are having belt slip thinking that the BLV is functioning as expected.
Joined: Sep 2006
Posts: 880
Likes: 0
From: San Antonio, TX
Let's talk supercharger high speed seals (impeller shaft seals) for a minute...
There are two kinds: the face seal (which is what Vortech installs OEM) and a lip seal. Ours is a twin-lip seal.
As you know, they both fail. The OEM face seal leaks too after a time, and that's why you went looking for and found our twin-lip seal.
However: be sure that the seal is the real problem, and not just a symptom of a different problem.
Attach a boost pressure gauge to your crankcase temporarilly under load and see how much crankcase pressure you are building.
You might find the underlying cause for why your impeller shaft seals are weeping.
The Vortech supercharger (except the new V3 model) receives oil from the engine at about 60 to 80 psi while the engine is running.
Yet the drain is gravity only, and the oil in the supercharger is now entrained with air, making it even more sluggish and difficult to drain.
If the crankcase has pressure, the oil in the supercharger cannot drain, the supercharger case builds pressure, and the seals leak.
Some tips:
1) Be sure that your oil drain out of the supercharger is in the 6:00 (straight down) position
2) be sure that the oil drain is at least 3/4" in diameter. Nothing smaller.
3) be sure that the PCV system has been modified since the supercharger was installed, and is not pressurizing the crankcase with boost.
4) be sure that you don't have a scratched cylinder wall - one bad cylinder can build more boost in the crankcase than you can possibly evacuate.
Both the face seal and the twin-lip seal require that the impeller shaft be flawless or the seal cannot seal against it. Sometimes I have to tell a customer that their
impeller shaft is so worn at the seal surface that they must get a new shaft from Vortech. It happens.
Here's a story: in a case where the supercharger was weeping oil, and we replaced the seals and the customer reported it was still weeping oil; we asked the customer to run this experiment. With the car on jack stands, he removed the drain hose from the nipple they had installed in the top of his oil pan. We had him attach a boost gauge to that nipple in the oil pan, and aim the supercharger drain hose at a bucket on the floor.
Then he ran the motor and revved the engine a few times. Not really a full-load test, but OK. He reported that the oil streamed out of the hose OK into the drain pan, but the crankcase pressure climbed into more than 2 psi just over 3000 rpm. Under load, this would be much higher. He learned that his crankcase was pressurizing and that his supercharger could drain, or would drain, if the crankcase would let it.
His search for a cause found him to a "vacuum line" from the PCV system (it was a vacuum line when the car was NA, now it's a pressurized line) that was still hooked up, and manifold pressure was being routed to the crankcase and pressurizing it. Shunting that line lowered the crankcase pressure, he gained HP, and the oil seals stopped weeping. (PS: just because you installed a "kit" dont assume the kit developer took this into account. You have to check. If you don't remember modifying the PCV system when you installed your supercharger, assume it hasn't been done.)
There is more on this topic, but that should give you a clearer picture as to what is going on.
If I can help, email me.
Carl Fausett
Member S.A.E.
928 Motorsports, LLC
There are two kinds: the face seal (which is what Vortech installs OEM) and a lip seal. Ours is a twin-lip seal.
As you know, they both fail. The OEM face seal leaks too after a time, and that's why you went looking for and found our twin-lip seal.
However: be sure that the seal is the real problem, and not just a symptom of a different problem.
Attach a boost pressure gauge to your crankcase temporarilly under load and see how much crankcase pressure you are building.
You might find the underlying cause for why your impeller shaft seals are weeping.
The Vortech supercharger (except the new V3 model) receives oil from the engine at about 60 to 80 psi while the engine is running.
Yet the drain is gravity only, and the oil in the supercharger is now entrained with air, making it even more sluggish and difficult to drain.
If the crankcase has pressure, the oil in the supercharger cannot drain, the supercharger case builds pressure, and the seals leak.
Some tips:
1) Be sure that your oil drain out of the supercharger is in the 6:00 (straight down) position
2) be sure that the oil drain is at least 3/4" in diameter. Nothing smaller.
3) be sure that the PCV system has been modified since the supercharger was installed, and is not pressurizing the crankcase with boost.
4) be sure that you don't have a scratched cylinder wall - one bad cylinder can build more boost in the crankcase than you can possibly evacuate.
Both the face seal and the twin-lip seal require that the impeller shaft be flawless or the seal cannot seal against it. Sometimes I have to tell a customer that their
impeller shaft is so worn at the seal surface that they must get a new shaft from Vortech. It happens.
Here's a story: in a case where the supercharger was weeping oil, and we replaced the seals and the customer reported it was still weeping oil; we asked the customer to run this experiment. With the car on jack stands, he removed the drain hose from the nipple they had installed in the top of his oil pan. We had him attach a boost gauge to that nipple in the oil pan, and aim the supercharger drain hose at a bucket on the floor.
Then he ran the motor and revved the engine a few times. Not really a full-load test, but OK. He reported that the oil streamed out of the hose OK into the drain pan, but the crankcase pressure climbed into more than 2 psi just over 3000 rpm. Under load, this would be much higher. He learned that his crankcase was pressurizing and that his supercharger could drain, or would drain, if the crankcase would let it.
His search for a cause found him to a "vacuum line" from the PCV system (it was a vacuum line when the car was NA, now it's a pressurized line) that was still hooked up, and manifold pressure was being routed to the crankcase and pressurizing it. Shunting that line lowered the crankcase pressure, he gained HP, and the oil seals stopped weeping. (PS: just because you installed a "kit" dont assume the kit developer took this into account. You have to check. If you don't remember modifying the PCV system when you installed your supercharger, assume it hasn't been done.)
There is more on this topic, but that should give you a clearer picture as to what is going on.
If I can help, email me.
Carl Fausett
Member S.A.E.
928 Motorsports, LLC
Registered User
Joined: May 2004
Posts: 1,049
Likes: 5
From: Myrtle Beach
Originally Posted by S2000Shifter' timestamp='1343325846' post='21891423
This is odd. My BLV works and I am limiting it to 16 PSI with a 3.2" pulley running to 9,000rpms. I hit 16psi by about 7,000rpms. In fact, the car stops building boost at 16psi and then slowly drops down to 15 or 14psi by 9k.
Here's the dyno plot:
[attachment=24419:Graham S2K.jpg]
I will have to dig up my data logs to show the boost levels relative to rpms.
Here's the dyno plot:
[attachment=24419:Graham S2K.jpg]
I will have to dig up my data logs to show the boost levels relative to rpms.
Belt slippage with 1200 and 3" pulley
Are you using the SOS pulley? Maybe you are having belt slip thinking that the BLV is functioning as expected.
Registered User
Joined: Jul 2012
Posts: 9
Likes: 0
Generally, you can see belt slippage two ways: 1) on the dyno or car-mounted boost gauge, the boost will plateau. Centrifugal superchargers make more air the faster you spin them, almost without limit (almost!). So if you run up to 8 psi or whatever, and the tach shows the engine still increasing revs and the boost stays still - its belt slip. 2) a dark rubber residue on the front of the supercharger near the pulley - that's rubber thrown by belt slippage.
Remember that every time you change to a smaller pulley, you loose tractive force on the belt and the ability to pull a load. To make matters worse - you just increased the load - trying to move more air increases the load on the belt, and now you have even less tractive force to do it with because the pulley is smaller.
Solutions for belt slip:
1) go from a 6-rib to an 8-rib pulley system. If 8-rib, go to 10-rib or a cogged pulley system.
2) if using a sprung belt tensioner, replace with static (solid) belt tensioner.
3) if driving the supercharger from a shared serpentine belt that drives the other auxiliaries, change it so the supercharger has its own belt. The supercharger demands 50 to 100 HP to drive it (depending on model, back-pressure, and rpm) and nothing else in that system (the alternator, the power steering pump, etc) do. So the serpentine system is not designed for that load and you will never get the belt tight enough. If you did, you would overload the alternator bearings to an early failure anyway. It is convenient for kit makers to drive off the serpentine belt, but that only works for light supercharger loads up to about 6-8 psi. Put the supercharger on its own crank pulley with its own tensioner.
3) get more belt wrap. Optimum belt wrap around the supercharger pulley is 190 degrees. Sometimes you can install an idler pulley in the system
to create more belt wrap around the supercharger drive pulley.
4) Increase the sizes of both the drive and driven pulleys in the system. Example: increasing the size of the crankshaft (drive) pulley allows
you to run a much larger supercharger (driven pulley) too, get more tractive force, and keep the ratios you want (or even spin the supercharger faster).
5) use a good belt dressing. This is a short-term solution. Sometimes we apply a belt dressing to confirm a diagnosis of belt slippage. Apply the belt dressing (available from any auto parts store for about $4) and if the boost goes up, you had belt slip. Correct it permanently with one of the solutions 1-4 above.
Do not expect to hear a slipping 6 or 8-rib belt. They usually don't make any noise. V-Belts will squeal, multi-rib belts wont.
Just some tips - hope it helps.
Carl Fausett
Member S.A.E.
928 Motorsports, LLC
Remember that every time you change to a smaller pulley, you loose tractive force on the belt and the ability to pull a load. To make matters worse - you just increased the load - trying to move more air increases the load on the belt, and now you have even less tractive force to do it with because the pulley is smaller.
Solutions for belt slip:
1) go from a 6-rib to an 8-rib pulley system. If 8-rib, go to 10-rib or a cogged pulley system.
2) if using a sprung belt tensioner, replace with static (solid) belt tensioner.
3) if driving the supercharger from a shared serpentine belt that drives the other auxiliaries, change it so the supercharger has its own belt. The supercharger demands 50 to 100 HP to drive it (depending on model, back-pressure, and rpm) and nothing else in that system (the alternator, the power steering pump, etc) do. So the serpentine system is not designed for that load and you will never get the belt tight enough. If you did, you would overload the alternator bearings to an early failure anyway. It is convenient for kit makers to drive off the serpentine belt, but that only works for light supercharger loads up to about 6-8 psi. Put the supercharger on its own crank pulley with its own tensioner.
3) get more belt wrap. Optimum belt wrap around the supercharger pulley is 190 degrees. Sometimes you can install an idler pulley in the system
to create more belt wrap around the supercharger drive pulley.
4) Increase the sizes of both the drive and driven pulleys in the system. Example: increasing the size of the crankshaft (drive) pulley allows
you to run a much larger supercharger (driven pulley) too, get more tractive force, and keep the ratios you want (or even spin the supercharger faster).
5) use a good belt dressing. This is a short-term solution. Sometimes we apply a belt dressing to confirm a diagnosis of belt slippage. Apply the belt dressing (available from any auto parts store for about $4) and if the boost goes up, you had belt slip. Correct it permanently with one of the solutions 1-4 above.
Do not expect to hear a slipping 6 or 8-rib belt. They usually don't make any noise. V-Belts will squeal, multi-rib belts wont.
Just some tips - hope it helps.
Carl Fausett
Member S.A.E.
928 Motorsports, LLC
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