Define 25 degree After TDC verus "0" TDC

[GNONYX]

Hi All,
After reading Casper cam sensor tool installation guide, but I would like to know what is the purpose of moving to 25 degrees after TDC when the original "0" marking was set by the factory? Thanks

 

[Nick Micale]

The TDC mark is there on the balancer to establish TDC which is, and can be used, for other functions.

To set the cam sensor, the factory designed/established the cam setting used for the SFI to be baselined at 25 degreess after TDC.

 

[BOP4ever]

I think it is to delay the injector spray until
Airflow is established in the runner kinda a timing
Thing. I could see how maybe changes in the cam or other engine parameters
Might change what would be optimum though.

 

[novaderrik]

I think it is to delay the injector spray until
Airflow is established in the runner kinda a timing
Thing. I could see how maybe changes in the cam or other engine parameters
Might change what would be optimum though.

they could have programmed that into the chip and allowed everything to be set at TDC... they probably did it the way they did it to make it unnecessarily complicated to keep people from attempting to work on their cars at home and go to the dealer...

 

[BOP4ever]

Yeah it probably could have been done differently. I am fairly new to my buick and after changing the first head gasket I think there were some messed up people that designed a lot of crap on this car....I mean come on changing the stinking passenger valve cover gasket is a real PITA and its a freaking v6 there should be plenty of room for stuff like that under the hood ... mixed up metric and STD fasteners etc... nothing about this car is easy or makes sense so why should the cam sensor.

 

[GNONYX]

The TDC mark is there on the balancer to establish TDC which is, and can be used, for other functions.

To set the cam sensor, the factory designed/established the cam setting used for the SFI to be baselined at 25 degrees after TDC.

Hi Nick, I'm just curious of what other functions is the marking on the balancer besides the TDC timing?

Also, if the baselined is 25 degree after TDC, then why didn't factory place the marking on 25 degree instead of its original position? Thanks

 

[RmvBfrFlght]

Part of the reason for the strange timing set up is that the crank signal pulse needs to be bracketed by the cam signal pulse. This places the falling edge of the crank signal about the middle of the low going cam pulse.

If both occurred at the same time the ICM and ECM would be jumping between two cylinders as for which one is #1. This would happen as jitter and such would have the two signals moving a tad in relation to each other.

RemoveBeforeFlight

 

[Nick Micale]

I don't want to sound like an ass, but some of you guys have no clue about these Buicks, and not good understanding of automotive technology.

The 1984-87 turbo Buicks were over 10 years or more ahead of engine computer management and turbo use in the automotive world, and developed and produced a package that is still kick-ass even in its stock form.

I know some of you may not have even been born when these cars were new, but the entire auto industry was much different then. It was nothing short of outstanding that the Buick Motorsports Group was able to convince management to even put the intercooled cars into production for 2 years KNOWING the Regal for 1988 was going to be a front-driver, and HP was not important .

Being first generation computer cars, they still are not yet outdated.

Instead of complain and whine, why not study and read to learn about these turbo Buicks, and find someone that does know them and work with them to learn some hands-on skills?

 

[bison]

Lol to most of the replies here. What Nick said is spot on.

 

[mikestertwo]

The cam sensor is set 25*ATDC because cylinder #1 is not the first cylinder in the sequence. Cylinder #6 is. The sequence order is 6-1-2-3-4-5

 

[Blazer406]

This is getting off topic but how many other cars at the time (domestic or import) were sequential electronic fuel injection, turbocharged, and intercooled..... and produced the HP these 3.8's did?

This thing was way ahead of its time..... no doubt.

 

[RmvBfrFlght]

The cam sensor is set 25*ATDC because cylinder #1 is not the first cylinder in the sequence. Cylinder #6 is. The sequence order is 6-1-2-3-4-5

I was using #1 to keep it simple. However, the 3.8l Buick engine's firing order is 1, 6, 5, 4, 3, 2

RemoveBeforeFlight

 

[MeanBuicks]

I am fairly new to my buick and after changing the first head gasket I think there were some messed up people that designed a lot of crap on this car....I mean come on changing the stinking passenger valve cover gasket is a real PITA and its a freaking v6 there should be plenty of room for stuff like that under the hood

To further Nick's point, park an intercooled TR next to a VIN A 2bbl Regal and ask yourself which car you'd want to work on. Considering all the bells & whistles these TRs received, they were packaged rather briliantly especially compared to their 110 Hp cousins.

 

[turbodave231]

These cars are relatively EASY to work on when you compare them to some of the new stuff coming off the line today. The Engineers don't design them with serviceability in mind....They only have one objective: Build it on an assembly line at 50-60 per hour!!!

 

[blackdeathtrap]

I dont know about you guys but i work on tracked light armord vehicles all day and i find theres miles of room when im home work on my gn the when im at work pulling the detroit 2 stroke which are turbo intercooled after cooled and have a roots blower and btw tlav was built not long after gn the m113a6 is same age the mtvr is only a lil younger same vehicle just longer to carrie more troups

 

[novaderrik]

I don't want to sound like an ass, but some of you guys have no clue about these Buicks, and not good understanding of automotive technology.

The 1984-87 turbo Buicks were over 10 years or more ahead of engine computer management and turbo use in the automotive world, and developed and produced a package that is still kick-ass even in its stock form.

I know some of you may not have even been born when these cars were new, but the entire auto industry was much different then. It was nothing short of outstanding that the Buick Motorsports Group was able to convince management to even put the intercooled cars into production for 2 years KNOWING the Regal for 1988 was going to be a front-driver, and HP was not important .

Being first generation computer cars, they still are not yet outdated.

Instead of complain and whine, why not study and read to learn about these turbo Buicks, and find someone that does know them and work with them to learn some hands-on skills?

when i look at something that makes no sense- like using 25ATDC to line up a very important part of the engine control system and not putting another mark on the balancer for it, for example- and ask why in the hell they did it that way.. with as much special engineering as they put into these things, would it have been too much extra engineering to either put a different mark in the harmonic damper (which is unique to these cars thanks to the crank sensor ring, anyways) or a different timing pointer that has the proper mark on it? hell, why hasn't some aftermarket company come out with a pointer with a mark at 25 ATDC to make life easier for everyone? it's almost like TR people get off on bragging about how hard these cars are to work on as if it's something to be proud of..

 

[WH1_T-Type]

I don't want to sound like an ass,

Than why say this?

but some of you guys have no clue about these Buicks, and not good understanding of automotive technology.

and this

Instead of complain and whine, why not study and read to learn about these turbo Buicks, and find someone that does know them and work with them to learn some hands-on skills?

Isn't that EXACTLY what they did by starting this thread? Asked and try to learn? Not everybody has access to someone that knows these cars really well, and a LOT of the information on the internet that is real in depth and technical can be hard to read cold. So we come to forums, ask questions, and learn. It's all some people have.

And despite what some like to say..these cars ARE hard to work on when you are first starting out, and I would say for some time after that! Sure once you get used to things they get easier...but that is true for everything. Just like it is true that once you know something a person often forgets the difficulting it was to learn about it.

 

[87-WE2]

Just like it is true that once you know something, a person often forgets the difficulty it was to learn about it.


^ I like!!

 

[Grumpy]

Obviously none of you have ever worked on a late 60s Mustang Cobra Jet. Buicks are a breeze are far as "room". AND a lot of guys will never get them right.. They just want to throw parts at it an run 10's . Come on !! Hands on will "teach" you a lot faster . After looking at the new Mustang GT 500 the ol 25 year old Buick is a walk in the park.

 

[BobbyBuick]

when i look at something that makes no sense- like using 25ATDC to line up a very important part of the engine control system and not putting another mark on the balancer for it, for example- and ask why in the hell they did it that way.. with as much special engineering as they put into these things, would it have been too much extra engineering to either put a different mark in the harmonic damper (which is unique to these cars thanks to the crank sensor ring, anyways) or a different timing pointer that has the proper mark on it? hell, why hasn't some aftermarket company come out with a pointer with a mark at 25 ATDC to make life easier for everyone? it's almost like TR people get off on bragging about how hard these cars are to work on as if it's something to be proud of..

Well why didnt the factory in 1970 mark the 36BTDC on my Pontiac because that is how I set the timing , full advance.
Step one grab a hack saw
step two grab some tape
step three grab a tape measure i think it is one and 15/32nd
step 4 mark with tape and cut a groove
done
alway helping no problem