Tach spikes under load/RPM

AlHounos · Post by **AlHounos** » Mon May 29, 2006 12:46 pm

Using stock CAS. V3 29q2

The car idles very well, and under very light loads and low rpm, it is fine. But when any load is put on the engine, the car stutters violently and I tracked this down to a tach spike using datalogs.

The car ran very well on fuel only, is there some type of interference
I should fix or resistors that I could add?

Thanks!

In neutral, it revs freely to about 3000-4000rpm, when it starts missing and the tach becomes unstable.

AlHounos · Post by **AlHounos** » Tue May 30, 2006 1:01 pm

Can anyone help? Everytime I think I'm going to get this on the road, a new problem comes up.

Keithg · Post by **Keithg** » Tue May 30, 2006 1:25 pm

What are you using for a coilpack? I assume you are running wasted spark with the CAS dizzy/2nd input. Are you running resistor plugs? Do you have your VB921s grounded to the star ground point (head on engine)?

KeithG

AlHounos · Post by **AlHounos** » Tue May 30, 2006 1:40 pm

I am using the LEDs to fire the stock external ignitor and coils. It uses wasted spark. I am running resistor plugs.

Thanks!

Keithg · Post by **Keithg** » Tue May 30, 2006 1:59 pm

well, I am at a loss. Someone with more CAS experience may be able to help. My first thought was resistor plugs.

KeithG

AlHounos · Post by **AlHounos** » Tue May 30, 2006 5:01 pm

Alright, thanks anyway.

Could it be caused by a poor ground? I have one MS ground grounded with the factory ECU, and the other grounded with my LC1 ground on a bolt sticking up through the floorboard.

Leistung Elektronik · Post by **Leistung Elektronik** » Wed May 31, 2006 6:23 am

I have a similar problem. I have added some resistance to the VR negative cable on the board ( input of the LM1815) and the misfire climbed to around 7000 rpm, but still there. I have the maps by TPS (Alpha N), but i don't think that was the problem.

I guess the motor have a poor ground, because it is a drag car and have a lot of work to do yet. I will make some test later.

Code: 26h4 - TPS - 4 ITB - 1.600 cc - Racing Cam

Thanks

hzdistributor · Post by **hzdistributor** » Wed May 31, 2006 9:13 pm

I have the same problem, I don't remember but I saw somewhere the problem is the ground on the board something about GX2 Pin external grounded.

Leistung Elektronik · Post by **Leistung Elektronik** » Thu Jun 01, 2006 6:07 am

Wenn you have an noissy tach signal you must ground externally the input ground of U4 to insolate the noise tach input.

I have no problem with noise, but always is a god practice insolate cables with sync signals.

I use a 36-1 wheel and LM1815....but have no scoped a noissy signal at all.

I have fried the starter motor, when the motor run again i will made some test with the coils and the VB921 ground directly grounded to the negative terminal of the batery.

I hope ground connection is the problem.

I will post the result of the test soon as possible.