Supercharger boost
- Thread starter 6-71
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Twin_Turbo
Der Maulwurf
- Joined
- Mar 5, 2008
- Messages
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IMO boost is a rather poor way to compare this stuff. See, it's just a measure of resistance of the intake tract (intake, valve train..blah blah). What really matters is VE, or better cylinder pressure. If you have 2 similar engines but with different intakes and cams, but with the same "boost" levels, that doesn't mean both perform the same. The one with the more efficient intake will reach higher cylinder pressures for the same boost reading.
Thanks for that, the engine was running 34T bottom pulley and 37T top pulley, which was supposed to give 7-9lbs of boost! This setup actually ran at 3lbs! The bottom pulley has been changed to a 36T and it is now running at 6lbs. Running with the 36T gave max hp of 533@5500 and max torque of 540@4500. I'm running Dart Pro1 heads and hydraulic supercharger rated Comp cam. The dyno guys said that there was no evidence of any 'pinking' (knocking) and the engine could possibly be set up with a larger bottom pulley for more boost without the need to retard the ign. Nobody seems to be able to give me a formula for my engine to determine max safe size to go to. I feel there's a lot more power to be had before needing to retard the ign, but pulleys aren't cheap and trial and error is an expensive option.:search:
Twin_Turbo
Der Maulwurf
- Joined
- Mar 5, 2008
- Messages
- 7,579
By pinking, they probably mean little pink balls deposited on the sparkplugs.
Why not pull a knock sensor and ESC box from a GM car. The old (early 80s) cars have a separate box, the later ones have the ESC as part of the ECM, you would have to remove it from ther. That way you could easily hook it up to a small led to serve as a knock indicator.
Why not pull a knock sensor and ESC box from a GM car. The old (early 80s) cars have a separate box, the later ones have the ESC as part of the ECM, you would have to remove it from ther. That way you could easily hook it up to a small led to serve as a knock indicator.
big_G
Blown Member
Maybe "Pinging"?
We need to know more about your enging combo...such as compression ratio, timing etc. With my ProCharger, my last dyno pull we saw >18 lbs. of boost. I have an intercooler, which helps a lot. You may be close to your pump gas boost limit.
Sorry for the delay in replying, 'been away'. Its running 7.8:1 CR, Twin Holley HP DP 600cfm carbs, Comp Cam 242/248 roller hydraulic cam, MSD boost timing master, Mallory distributer, forged 5.7 Eagle rods, lunati pistons, Forged Eagle blower crank, roller rockers etc. Ign timing 36 degrees @ 3500 (vac disconnected) Electronic Vac advance 10 degrees. Boost retard 0 :huh:
Let me know if you need any other info.
big_G
Blown Member
Wow... that's low compression. You should be able to run lots of boost. If it's pinging, you will need to pull some timing. Maybe get a knock sensor of some kind hooked up for safety. No magic formula out there, each engine is different. Trial and error.
jpetrick
Well-known member
Big G's right there....we have run a 6-71 and we started out turning the blower at 80% of the crankshaft rpm and worked up from there...
MSD also have a standalone knocksensor, its not cheap though...
http://www.summitracing.com/parts/MSD-8964/
I just ordered one to use with my weiand/B&M 250 blower.
http://www.summitracing.com/parts/MSD-8964/
I just ordered one to use with my weiand/B&M 250 blower.
jpetrick
Well-known member
We use a MSD Boost Retard Control to eliminate detonation, Heres an excerpt from weiland about ignition/timing and related issues.
Ignition Systems with a Supercharger
Many street supercharger applications will work fine with the
stock ignition system, because blown engines make so much
low and mid-range power, it is not necessary to rev to high
rpm's. High performance ignitions are primarily required to
provide adequate spark at higher than normal rpm's. If most
of your driving is going to be under 5,500 rpm, you probably
won't need an aftermarket ignition. For optimum performance
at higher engine rpm's, select an aftermarket performance
ignition system.
It is usually a good idea to run spark plugs that are one to
two ranges colder than normal with a blower. The more
boost, the colder the plug required. Colder plugs will foul
easier than hotter plugs, so in this instance a "hot" ignition
may be advisable.
The main thing that needs to be addressed with a blower is to
make sure that detonation is controlled. A handy device to
have is "boost retard control". With the use of this unit, you
can run normal timing settings which will allow for easy starting
and reasonable fuel economy under normal driving situations.
However, when you step on the gas and the engine
goes into boost, this timing setting may cause detonation.
With the "boost retard control," the driver can dial in ignition
retard with a dash-mounted knob. These devices usually
operate on a "degrees of retard per pound of boost" and are
typically adjustable from 1º to 3º of retard per pound of
boost. As an example, if the unit is set to deliver 1º per
pound of boost, that means that when your blower is putting
out 4 pounds of boost the distributor will be automatically be
retarded by 4º. When you reach 7 pounds of boost, it will be
retarded by 7º. Best results are achieved by driving the vehicle
under boost and adjusting the unit until any detonation is
eliminated.
NOTE: We do not recommend using these devices in marine
applications. Retarding the timing under boost increases the
combustion temperatures. On a street vehicle, this typically
occurs for short periods of time. In marine applications the
engine is usually in full boost all of the time. As a result, these
prolonged high combustion temperatures can burn pistons or
valves.
Most blown engines operate best on 28 to 34º of total timing.
Running more total advance will not provide any performance
increase.
Your distributor should have a centrifugal advance mechanism
that has been set up so that all of the advance is in by
2,500 rpm. The best way to set your timing is to put a permanent
mark on your harmonic damper that represents 34º
total advance. If your damper doesn't go this far, you can
measure the timing marks on your damper and then, using
your measuring tape, calculate where 34º would be. 34º is a
very safe figure and should provide close to optimum performance.
After you mark off 34º, start your engine and rev it up to a
speed where all the distributor's mechanical advance will be
in. This should be somewhere over 2,500 rpm. Then read the
new 34º mark like you would read TDC at idle speed. Adjust
the distributor so that the new mark on the damper lines up
with the "0" on your timing tab. This would provide 34º of
total timing or if you wanted 32º of total timing, you could
line up the mark on the damper with the 2º ATDC mark on
the timing tab instead of "0."
http://www.aa1car.com/library/weiand_superchargers.pdf
was taken from here and has some good information on blowers..
Ignition Systems with a Supercharger
Many street supercharger applications will work fine with the
stock ignition system, because blown engines make so much
low and mid-range power, it is not necessary to rev to high
rpm's. High performance ignitions are primarily required to
provide adequate spark at higher than normal rpm's. If most
of your driving is going to be under 5,500 rpm, you probably
won't need an aftermarket ignition. For optimum performance
at higher engine rpm's, select an aftermarket performance
ignition system.
It is usually a good idea to run spark plugs that are one to
two ranges colder than normal with a blower. The more
boost, the colder the plug required. Colder plugs will foul
easier than hotter plugs, so in this instance a "hot" ignition
may be advisable.
The main thing that needs to be addressed with a blower is to
make sure that detonation is controlled. A handy device to
have is "boost retard control". With the use of this unit, you
can run normal timing settings which will allow for easy starting
and reasonable fuel economy under normal driving situations.
However, when you step on the gas and the engine
goes into boost, this timing setting may cause detonation.
With the "boost retard control," the driver can dial in ignition
retard with a dash-mounted knob. These devices usually
operate on a "degrees of retard per pound of boost" and are
typically adjustable from 1º to 3º of retard per pound of
boost. As an example, if the unit is set to deliver 1º per
pound of boost, that means that when your blower is putting
out 4 pounds of boost the distributor will be automatically be
retarded by 4º. When you reach 7 pounds of boost, it will be
retarded by 7º. Best results are achieved by driving the vehicle
under boost and adjusting the unit until any detonation is
eliminated.
NOTE: We do not recommend using these devices in marine
applications. Retarding the timing under boost increases the
combustion temperatures. On a street vehicle, this typically
occurs for short periods of time. In marine applications the
engine is usually in full boost all of the time. As a result, these
prolonged high combustion temperatures can burn pistons or
valves.
Most blown engines operate best on 28 to 34º of total timing.
Running more total advance will not provide any performance
increase.
Your distributor should have a centrifugal advance mechanism
that has been set up so that all of the advance is in by
2,500 rpm. The best way to set your timing is to put a permanent
mark on your harmonic damper that represents 34º
total advance. If your damper doesn't go this far, you can
measure the timing marks on your damper and then, using
your measuring tape, calculate where 34º would be. 34º is a
very safe figure and should provide close to optimum performance.
After you mark off 34º, start your engine and rev it up to a
speed where all the distributor's mechanical advance will be
in. This should be somewhere over 2,500 rpm. Then read the
new 34º mark like you would read TDC at idle speed. Adjust
the distributor so that the new mark on the damper lines up
with the "0" on your timing tab. This would provide 34º of
total timing or if you wanted 32º of total timing, you could
line up the mark on the damper with the 2º ATDC mark on
the timing tab instead of "0."
http://www.aa1car.com/library/weiand_superchargers.pdf
was taken from here and has some good information on blowers..
jpetrick
Well-known member
No Problem, hope it works out for you and when you do get it running would love to hear. The 6-71 I used to run on the 57 I still have and have been looking for something cool to run it on.
Love 57's ..even better with a 6-71. Have you any pictures of it, would love to see it.:nuts:
jpetrick
Well-known member
look in my photos, I have a few of it there.....its set up now with a all roller 468..