Glass Cars, Grounds and Ignition questions

[Cajun Kid]

I know on my Fiberglass HotRods with powder coated frames and all the wiring for running on the street getting all electrical components a good ground is very important.  My question is on my race car it is a glass body on a new freshly powder coated chassis.  The new engine did very well on the dyno... When we fired it up in the car it seemed as if the starter was very slow and then the engine seemed FAT  not wanting to rev as crisply as before.  We put jumper cables from the battery to the engine block and the starter spun over very strong and fast. but the engine did not seem to rev a crisply.

The motor mounts and trans mounts are urethane,,, can the MSB box with a poor ground and the engine with a poor ground cause this symptom?

We just finished putting new grounds wires from the block to the chassis, the battery to the chassis, the MSD boc the the block..  When I get off work tomorrow am going to the shop and crank it again to see if that fixed it..

Just wondering if we are on the right track ?

Thanks

Charles

[RichFox]

I think you just proved the answer. MSD needs full current flow.

[Cajun Kid]

Never used MSD box before,,, But when I get to shop tomorrow after lunch, I hope to fire her up and see if all the grounds we put on solve the problem.... Car sounded good but the rev's just did not seem sharp and crisp.. I talk to my motor guy he told me about the grounds... Since we are on time crunch to get all the bugs worked out before Maxton, I figured better ask some of you experts...

It has been 17ish years since I piloted a race car or race bike... just want everyting to be right when I unload the car at Maxton nect friday.

Charles

[Glen]

Charles, we have a lot of faith in you, there is help at the races as well, don't be bashful. Hope your tests go well and you get in a few good runs.

[Cajun Kid]

Thanks Glen.... this is one good group of people...Have a great night.

[sanger351]

I think you are on the right track also.  My instructions suggest grounding each head, if you haven't done so already and possiably the distributor.  Good luck

[Cajun Kid]

S351  yes I was thinking it would be a good idea to ground them as well.  It is going to look like the block, heads and dist are on an EKG machine LOL...

Thanks for the tip

[doug odom]

Ground everything with wire back to the battery. I might use two or three grounding lugs depending on how far apart the electonic units are so there are fewer wires running the length of the car. Race cars should never rely on the chassis for ground.

[Cajun Kid]

Thanks, I am doing just that.

[Blue]

Ground everything with wire back to the battery. I might use two or three grounding lugs depending on how far apart the electonic units are so there are fewer wires running the length of the car. Race cars should never rely on the chassis for ground.

Ditto, big time.

A zero resistance ground reference is critical to anything that carries a load.  Ignition and starters apply.  Clean, filtered power is critical to the performance of all electronics;  most of these have good internal filters but can't function without a low resistance current path to ground.

Too many builders make sure of good power connections and neglect the grounds.  Use wire and connections equal or better than the power connections and never rely on the chassis.

[POPS]

Cajun,
If you are running a data acquistion system be carefull.  If you are, use only one ground point for everthing.  I recommend using one wire from each head, one from the ignition, one from everything else to a 1/4-20 stud.  If you have more than one ground point you introduce what are called ground loops.  The ignition will emit RFI which will radiate to the ground loops which will then mess the data acquistion up.  This not a small point, it is very important.  Do not use the frame as a return path when you use a data acquistion.  We do this on Top Fuel cars and we did it on our lakester and the Racepak data is perfect.
Sorry for being a no-it-all, but it comes with being an engineer.
POPS

[manta22]

Pops;

Running all ground returns to a single point (a "star" ground) is a good idea at DC. At high frequency the inductance of ground return wires can make them a relatively high impedance and if any EMI/RFI source has significant capacitance to the chassis, you have a ground loop even in a star- ground system. The ideal case would be to create a big ground plane by sheathing the bottom of the car with sheet copper but this isn't practical, of course. When all is said and done, the best compromise is probably a star ground systen like you suggested with heavy gauge wire. Placing RFI filters in the power lead of sensitive systems can also help.

[Cajun Kid]

Hmm I a still a bit confussed  but with such good answers from the this group of folks
I am just confussed at much higher level ... LOL

Thanks for the help.  It seems as if your suggestions have worked.

[DahMurf]

Hmm I am still a bit confussed  but with such good answers from the this group of folks
I am just confussed at much higher level ... LOL

Very funny and very true Charles! That is how I always feel with LSR involved. The more I think I understand the more indepth things get and the more confused I get and the less I feel I know and as you said, always on a higher level! LOL

Ask Todd about the circle of knowledge when you see him this weekend. I think the thought was passed on to us by ScottG and it fits the bill!

Deb

[narider]

That's a perfect example, and just what Charles is experiencing. The circle of knowledge was shared with me by Joe Timney when both of us were in the middle of my shop and a conversation had us each telling the other hjust ow much we didn't know.... Joe just happens to not know alot more then I do, which made me understadn the circle of knowledge all that much more. 

Lack of knowledge can be a very productive way of not looking at things - and it only takes more knowledge to gain it.

Looking forward to seeing you in a few days Charles.. glad it's coming together for you.
Todd