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Boost gauge and boost control question.
https://www.slantsix.org/forum/viewtopic.php?t=9374		 Page 1 of 1
Author:  Dartvader [ Sat May 22, 2004 5:26 am ]
Post subject:  Boost gauge and boost control question.
The stock Buick turbo has a t fitting in the waste gate pressure line. The guy who sold it to me said he thought this was for the boost gauge. Does anybody know if the output of the turbo sees vacuum under idle, and no- load operation? If so, then I can use a vacuum/boost gauge, and plumb it to this 't'. If it doesn;t see vacuum, then this particular line could input only a boost gauge. The other option is to plug this, and take a tap off the throttle body. Then there is the question about whether the ports on the throttle body see boost. I assume they do, but you know the old joke about the word assume.

Also, Dart270 just mentioned a boost/spark control unit from MSD. What do you know about this? How does it interface with the standard MSD-6? Where can I search mail order or internet to purchase one? Most important, any experience about how to tune it with a slant?
Author:  Bob D [ Sat May 22, 2004 8:13 am ]
Post subject: 
The signal to the boost gage comes from the same source as the signal to the wastegate actuator, and yes it sees both vacuum and boost. As far as the "T" is concerned that is OK as long as it isn't a "Y". If it is "Y" shaped replace it with a "T". The "Y" has a restriction in one arm and is only used with a wastegate solenoid that is used by the Buick ECM to control the wastegate actuator and consequently the boost. I understand that you are using a MS ECM so you won't be able to use this.
Bob D
Author:  Charrlie_S [ Sat May 22, 2004 9:07 am ]
Post subject: 
The MSD boost timing master can be used with the MSD 6a box. I have one that I bought to upgrade my turbo system. However I have been having problems. When I install the BTM between the mag pickup and the 6a box I get spark scatter and erratic tach operation. The btm has been sent back to MSD, and they said there is nothing wrong with it. Then they sent me another BTM, still had the same problem. They sent me a tach adapter, did not help. Tried a different tach, new Accel mag suppression wires, still have a problem. I am going to try some other things this week, and will post the results. Just letting you know about a potential problem, you may, or may not have.
Author:  Bob D [ Sat May 22, 2004 10:21 am ]
Post subject: 
I also have had problems with a MSD Boost Timing Master. When I tried mine the engine developed a "miss" at higher RPM. I put it aside and haven't got back to it. I have the 8762 model which is suppose to work with my MSD ignition. I haven't been impressed with MSD customer service in the past, and I can just imagine the confusion if I call and ask about my car that uses a SL6 electronic distributor with the centrifugal and vacuum advances disabled, a GM ignition module and GM ECM to control timing, and a MSD 6A box!
The car runs fine without it, and because I also have a knock detector with ECM control of the timing, it's not really necessary. I would like to use it eventually for added insurance but don't know when I'll get to figuring out what the problem is.
Charlie, what do you mean by "spark scatter"?
Vader, both Jeg's and Summit sell this box. Just go to their web sites and do a search.
Bob D
Author:  Charrlie_S [ Sat May 22, 2004 10:38 am ]
Post subject: 
Bob, If you are using the knock detector, I wouldn't use the timing master. You will not have optimum advance, using both. As for "spark scatter", if you put a timing light and the engine, the timing marks jump around. It is like I am getting extra ign pulses. I though, the BTM might be picking up "noise" and amplifing it, the the 6a would se this as distributor pulses and give extra sparks. But MSD says there is no way the BTM could amplifi "noise". Two things I'm going to try is, change the distributor, for one with a new pickup. I also got some shielded twin lead from radio shack, and will run this from the dist to the BTM, and see what happens.
Author:  Bob D [ Sat May 22, 2004 12:56 pm ]
Post subject: 
Thanks Charlie. Let us know if you resolve the BTM issue. I'll do the same.
My thinking on using both a knock detector and BTM was as follows: The knock detector only retards spark when knock occurs. The problem is that once knock occurs, to stop it the timing has to be retarded by the ECM by as much as four times what it would have taken to prevent the knock in the first place. This is known as knock hysteresis. As a result the timing curve has to be kept conservative throughout the RPM range to insure that knock doesn't occur at full boost with a resulting drastic retarding of the timing. With the addition of a BTM the timing curve can be kept aggressive throughout the RPM range and then only retarded as boost increases. In this way knock can be avoided as boost increases and timing can be kept optimum through both the RPM and boost ranges.
Bob D
Author:  69dart [ Sun May 23, 2004 9:41 am ]
Post subject: 
Thsi thought comes with a big disclaimer I HAVE NOY TRIED THIS YET. I am working (slowly) at putting a centrifugal supercharger in my car and I worked on this problem for a while on paper. With the supercharger the boost would be created at a very predictable rate do to the belt dive but I do not know if this holds true with a turbo. My thought was to use the MSD Multi Function Ignition Controller in place of the BTM. this will allow you to map out the timing curve on the computer. this will eliminate the spring and weights in the disributor and allso allow for changes in each cylinder. at about the same cost as the BTM. you still need to run your 6A or ?, if you do not have that yet you can buy it all in one box. you can still add a knock retard to this I belive.

what do you think?
Steve
Author:  Bob D [ Sun May 23, 2004 11:18 am ]
Post subject: 
It does look like a "trick" component and I think that it should work. There is quite a difference in price though. The MSD Multi-Function Ignition Controller with boost control (which is the one that you will need) Summit price is $419 while the BTM is $183. It does look like it's worth the difference though to have that kind of ignition control. For now I'll stick with me $25 junk yard ECM for ignition control. At that price I carry a spare in the trunk. :D
Good luck with the project and keep us posted!
Bob D
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