Back in the Saddle!

[AndyM]

Had my first drive yesterday in the coupe since the 3.5 conversion and custom injection. After sorting out some misplaced wiring and a defective MAP sensor, I must say it turned out awesome! Better than expected. No leaks, no pinging, runs cool, tons of power, etc., but what surprised me the most is how smooth it seems to run. I haven't really pushed it too hard, but I did squeeze one (okay maybe two) wide open throttle runs. The higher compression pistons and Shrick cam really bring the 3.5 to life. There's not a single hiccup from 1,000 rpm through 5,000 rpm -- just a broad, smooth powerband with more to give. I still have some injection tuning to sort out -- the idle isn't as clean as it could be and it keeps stalling on decel dropping back to idle -- but otherwise it seems my hundreds of hours of work have paid off! Phew, that's a relief.

 

[corsachili]

Congratulations Andy. It's always nice to hear about success rather than frustration! Any idea what sort of compression ration you're running? What is your "custom injection" and what sort of electronics are controlling all of this?

 

[AndyM]

TJ --

I ended up sticking pretty close to my original plan. The motor is a 3.5 with the stock bore -- it only needed a hone job. The head was rebuilt and I used new style Schrick cam with 284 degree with 10.1 mm of lift. I'm running the flat-top Mahle pistons intended for a VW. They are much lighter than stock and the C/R comes out to somewhere between 9.5:1 and 10:1 (depending on what calculator you use) -- perfect for street use -- and no clearance issues with the valves.

For the custom injection, I used my stock D-Jet manifold, but retro-fitted new Accel 24# injectors and GM sensors (manifold pressure, coolant temp, intake air temp, throttle position, O2, etc). I'm using an L-Jet distributor to control the spark. The stock L-Jet VR sensor in the distributor triggers an MSD. That triggers a GM '730 computer which controls the fuel.

The conversion is very similar to the Motronic conversions that have been done before, but there's no air flow meter since the GM system is speed density (MAP) based. The other main reason I used GM is the vast after-market support. I enjoy tinkering on things and liked the idea of being able to tweak the programming. Plus I can get replacement parts just about anywhere. Now that its running, I'll probably go ahead and convert it to full timing control, too. For now, though, I'm just going to enjoy driving it again.