Timing question...

I have a 92 coupe w/ factory EEC, extensive list of mods and an S trim. I was wondering how you guys set your timing. I have never heard, or checked, what the factory timing curve is on the stock distributor. I had always set the initial timing up high and retarded it with the BTM, but never really knew what my total timing was, which we all know is important. The car is apart right now, but when it is put back together, I plan on running around 12 to 14 PSI and drive it on the street with a mix of fuel and 93 octane. I have heard that BTM's are junk, and most people don't run them. I just wanted to know what everyone else does and what your thoughts and opinions are on the BTM.

Quote:

Originally Posted by 3blapcam

I have a 92 coupe w/ factory EEC, extensive list of mods and an S trim. I was wondering how you guys set your timing. I have never heard, or checked, what the factory timing curve is on the stock distributor. I had always set the initial timing up high and retarded it with the BTM, but never really knew what my total timing was, which we all know is important. The car is apart right now, but when it is put back together, I plan on running around 12 to 14 PSI and drive it on the street with a mix of fuel and 93 octane. I have heard that BTM's are junk, and most people don't run them. I just wanted to know what everyone else does and what your thoughts and opinions are on the BTM.

what's your fuel setup look like, size injectors/MAF etc.? i don't like FMU's so as soon as i could, i bought 42lb injectors and recalibrated my 77mm MAF. the best thing to do is to get a dyno tune from a reputable shop.

the timing curves are on the EEC and are not on the distributor. now if you up your base timing using the distributor you alter the timing curves used by the EEC. for example, stock base timing is 10deg set by the position of distributor. now the EEC uses timing tables like this:

BASE_SPARK_TABLE # Base Spark Table.(deg BTDC) (Load vs RPM)
35 35 35 28 28 28 28 28 28 28 28
35 35 35 32 35 38 38 38 38 38 38
35 35 35 35 35 36 38 39 38 38 38
17 20 21 26 31 34 36 37 38 38 38
14 17 19 25 30 30 30 30 30 32 32
12 14 15 19 21 22 25 27 28 30 30
10 12 12 18 19 20 23 25 26 28 28
9 10 10 11 15 18 21 23 24 26 26
9 9 9 11 13 17 19 21 22 24 25

if you change the base timing to lets say 12deg, you will add 2 deg to each number in the timing table above.

a good tuner can manipulate these timing tables at all rpm’s for optimum and safe performance. so that’s why a dyno tune is so much better. there’s so much more to this but you’ll fall asleep by the time i’m done. hopefully this will help you see why a good tune is so important.

my BTM went out and i'll never use it again. that's just me though. try and get a good dyno tune.

No, the data was just starting to get interesting when you stopped. I am very interested in that information.

My setup was a stock shortblock 351 w/ factory 8.8:1 Hyperpathetic pistons, etc, topped with Brodix ST 50 heads, 42lb inj. matching Pro M 77 MAF, complete Cartech fuel system w/ Cartech billet FMU. I broke #8 piston - (I think the rings were tired, but that's a long story.) So, I have been contemplating a 393 but I think the heads will choke the motor considerably.

Do you think the EEC will work well with the bigger motor, or is that going to be an issue? I have heard that the EEC doesn't like larger displacement, that it was only intended for 302 CI, but that's not from a reputable EFI source. With more displacement, should I use a bigger injector than the 42lber?

Thanks for all your insight and help. I would like to more driving and less sitting with this car.

Quote:

Originally Posted by 3blapcam

I broke #8 piston - (I think the rings were tired, but that's a long story.) So, I have been contemplating a 393 but I think the heads will choke the motor considerably.

Do you think the EEC will work well with the bigger motor, or is that going to be an issue? I have heard that the EEC doesn't like larger displacement, that it was only intended for 302 CI, but that's not from a reputable EFI source. With more displacement, should I use a bigger injector than the 42lber?

Thanks for all your insight and help. I would like to more driving and less sitting with this car.

I have a 12-1/2 to 1 compression 418 in my car. I have the factory EEC with a tweecer. The stock computer will run your car without any problems. The guy that told you the BS about the EEC not liking anything larger than a 302 should be kicked in the nuts, he doesn't know what he's talking about. As far as the size of your injector, it depends on how much boost/power you are going to make. I would think that the 42's are going to be too small. I run 42's on my motor and they are maxed out. Mine are 100% duty cycle @7200rpm.

As far as breaking the #8 piston, I will almost guarantee that you leaned it out and took out the ring land. It is very common because #8 is the last cylinder on the fuel rail. You can actually suck the fuel rail dry and the piston suffers the effects. Upgrade your entire fuel system before you lean on it again. After you get it running, get it dyno tuned. Its cheaper than replacing a motor.

Doug

Doug thanks for the insight on the injectors. How do I know what size to buy for my application? Are the fuel analyzers online accurate, or is it best to do it by trial and error?

Sorry for all the questions - I just don't want it to go pop when I get it back together.

Alec.