My brother has a 1994 A4 Z28. Bone stock, with 2.73's, the car ran 14.33 @ 98.05 mph. The stock dyno looked like this:



Slowly, he has been adding mild bolt-ons to the car and it now has the following:

K&N CAI
1LE Elbow
Airfoil
Magnaflow Catback
Electric Water Pump
3.42 gears
Nitto Drag Radials

The current best ET is 13.671 and the best mph is 100.20, before the electric water pump.

We took it back to the dyno today to get a basline before we finish the exhaust and install 1.6 rockers and springs over the winter. This was a different dyno, both were Dynojets, SAE corrected.

This is the graph from today:



The torque hit 287 on one run, but we rolled into the gas to keep it from downshifting, so each run was slightly different down low.

Does anyone have an idea about what will cause the graph to be choppy like that? Ignition misfire? I know the early skip is from the tack signal dropping out.

One of my A4 LT1's was the same way when I dynoed it, but I didn't have the car long enough to figure it out.

Any input is appreciated

 

Ignition or detonation due to how lean it is. Hopefully he hasn't already hurt the motor if its detonating.

 

Yeah, that was one of the things we were thinking when we were tossing ideas around at the dyno today. If it is detonating, I'm not hearing it when we drive the car, even when it was hot out during the summer (same setup for about a year now).

Plugs and wires are definitely on the asap to do list, and the tune needs to be richened up.

Thanks, man!

 

Where was the A/F reading taken?

 

The probe was put into the passenger side tail pipe.

 

Still running cats? Tailpipe sniffers are questionable at the best of times and if you have cats then I wouldn't believe the A/F reading at all.