feeling good ..... got the rocket to start

[-SeabrookTrickBagger]

We finally gave up on trying to get the 124ci, VFI intake equipped and DTT TCFI powered ECU to work.  So we told "her": we're gonna stick a carb on you bit*h!  We made another adjustment and she fired up like Carl Owens leaving the blocks.  Amazing.  Started better than my personal bike.  The bike owner was grinning from ear to ear since, for three years, he has not heard it start so well.

The ultimate resolution was recognizing that the TPS adjustments which had been so smooth and easy to find .4 volts was just that:  too easy.  So, we took out the Marelli brass bushings from the TPS and cranked it full clockwise, then set the dual plenum throttle plates to .006" and the TPS to .4 volts which was too much air since the engine lugged down on starting rotation due to higher volume of air entering the engine.  I then went to .003" tight air gap on the TB and set the TPS to .4 volts.  At this time, the TPS was extremely sensitive to any movement and .4 volts was hard to hit since a slight movement while rotating the TPS would cause it to jump 1 volt. Now this is what I am used to.  It fired up with a bit of lean surge and we worked that out; we really did not work that out since the heat sink aluminium TB opened the air gap to a loose .003" air gap after the engine warmed up (but that is another story).  Prior to this magical moment, I spent about 7 days trying to get it to start after chasing down a conglomeration of other problems such as a stuck compression release, bad battery connection, no VSS reading, high amperage starter, broken ring gears, on and on.

The moral to the story is either tell the bit*h you are going to put a carb on it .................. and keep messin' with it and don't quit.  Aftermarket EFI units and exotic intake systems ain't for quitters.  Personally, I don't see how a indep mech can make a living trying to tune mix and match EFI components coupled with exotic heads, wild cams and Burns stainless exhaust.  I suspect, if I was an mechanic, I would say "here is the combo which will work, anything other than that you are on your own or prepare to spend a couple of thousand dollars for the effort to get it to start and for the tuning."  For those guys who can do all this in 4 or 8 hours, my hat is off to them and I wish you had a shop around the corner.

One final matter. It appears that a Marelli TPS is a different animal than the Delphi TPS in that the voltage calculations by the ECU are different between the two units.  So, as far at the DTT TCFI III is concerned, if you have a Marelli TPS, you should use the VFI canned map, for a basic map, since the VFI canned map takes into account the Marelli voltage difference.  If you have a Delphi TPS, don't use the VFI canned map for converse reasons.  Or call Chris S. and ask him if you can switch to a Delphi or make parameters adjustments to compensate for the TPS you are using.  I could not find any adjustments in parameters to compensate for this so I had to use the VFI canned map and then inserted Alpha N numbers from a known good map close to this engine's combination of parts. We ended up with 29 alpha n in the starting cells from 0 percent through 7.5 percent throttle position at 500 rpms through 1250 rpms and it appears we are slightly rich -- thinking 26 might be on the money.  The VFI canned map from DTT, has 17 in these cells:  too lean, but that canned map was probably for a 95ci engine.