Vehicle: 1985 Pontiac Grand Prix
Engine: 355 CI Small block Chevrolet (Iron heads, Comp Cams XE262H camshaft)
Injection: Tuned Port Injection (TPI) from a 1989 Camaro 5.7L (22lb injectors)
Description: MSI v2.2
Hardest parts of this were reaming and spot-facing the post-1987 lower intake manifold so I could bolt it onto my pre-1987 heads and the fuel system.
My big lesson converting this carb'd car to fuel injection: screw metal fuel lines, go AN braided. Raw materials are more expensive ($6/foot for the hose, $5-$8 for the end fittings at my local speed shop), but it is just so much easier.
Earl's AN fittings are superior to Jeg's and Aeroquip from the standpoint of assembly.
I ran -6 AN supply from an external Walbro pump to the TPI, and attempted to use the factory vapor line as a return. It was rusty and burst the first time I fire the fuel pump. I then just ran -6 AN back to the rear axle and then rubber from there to the tank.
There is also a restrictor in the return inlet to the tank that must be drilled out (pull the sender assembly and cut off the little baffle around the vapor return, you'll see the brass restrictor), and you'll have to vent the tank somehow (I drilled a very small (3/32") hole in the gas cap) or it'll pressurize and eventually burst, which would be bad.
I guess the environmentally friendly way would be to run a new vapor return from a nipple welded/screwed into the filler neck up to the charcoal canister and then on to the intake manifold, but I needed to get this thing back on the road.
Use the throttle cable and TV cable for a 305 TPI Camaro/Firebird.
I was able to use a vacuum advance HEI, but there's no timed port vacuum source on the TPI throttlebody, so be conservative with your static timing.
The Megasquirt itself fits in the spot vacated by the factory ECM. Once I'm done tuning, I'll be able to tuck it away and nobody will know it's there.
It started and idled using the default VE table and constants from Bruce's 350 TPI, but this larger camshaft requires a lot more fuel to actually move the car. After a ten minute drive and one run through MegaLogViewer's VE analyzer, I was able to drive car to work (12 miles mixed freeway and City), though it would buck at high loads and ran rather rich at Cruising RPMs. Another analyzer run on the datalog from this morning's drive has built a much better looking map. We shall see if it is actually better.
I will come back and attach my MSQ file once I'm happy with it all.
I have a good 30 mile drive to take tonight, I'll be collecting a log and running it through the VE analyzer in MegaLogViewer. I should have a nice table good enough for mass consumption soon.
These have all been tuned on the road using MegaLogViewer. You'll notice if you poke around inside the MSQ that I have EGO correction off. I don't use it anymore. Once MLV got me close, the car ran better with it disabled. I think the cam gives a lumpy vacuum signal, and adding that to the EGO correction made things jump all over the place, and resulted in a rough running engine.
I may be able to get to a dyno sometime soon, but until then, I think this is about as good as it gets for my little project.
Hope this helps somebody!
MS-II, V 3, 2.886, LC-1. 1971 Chevrolet Monte Carlo 350, 270 HP. 1959 German Corvette, bought in Berlin. With a 160 "KPH" speedo. KPH??? - What were they thinking? 160 KPH is only 100 MPH. We can peg that in third gear!!! 1959 Cadillac, 502, huge Chrome Bumpers and really BIG FINS!!!
The car runs VERY well under these. It should bark gears, but this 150,000+ mile 200-4R is shifting a little soft. I haven't been able to get to a track or dyno to properly tune the upper reaches.. I'm getting 15mpg in town with 3.73 gears, which is very good for a recammed iron head Gen I 350 in a 3600lb car.
Hoping to get a computer controlled distributor in over this upcoming weekend and we'll see how that goes.
However, this MSQ has much smoother throttle tip-in and pulls all the way to 4000rpm with no knock on regular gas. Hot start is also much improved over the last one.
http://www.diyautotune.com/tech_article ... _v8_v6.htm
I fought with what I though were bad HEI modules, but it turned out that the 1.3K resister they have you put in place of D8 needed to be ~1K for my installation. It wasn't pushing enough voltage into the HEI module for the thing to properly trigger tach events.
Here's my .msq. It runs, but I've not done much tuning with the timing map. It's pretty much a vacuum-advance distributor curve translated into the table, but it runs very well. Completely solved a miss and problems with spark scatter above 3000rpm.
Also, a point not really emphasized enough on this modification: once you do it, you can't use a normal 4pin HEI module anymore. The inversion of the tach signal means triggering from the coil negative like you would in a fuel-only installation no longer works. When you go with this, you have to go all the way.