Since a couple of the TPI tubes had been mangled, we also decided to spice up the intake with a set of SLP runners and a new set of fuel injectors. Since we were purchasing new injectors, we decided to go with larger 38-pound-per-hour (lb/hr) injectors that would allow us to make more horsepower with this same MegaSquirt system. The new injectors were the most expensive single component of our swap at $420, but there are less expensive alternatives. For example, Olds Quad 4 injectors are capable of significant fuel flow and are boneyard cheap. Spend $10 apiece to clean them and you have a performance injector for a ton less cash. The MSD 38-lb/hr injectors will easily support 540 hp at an 85-percent duty cycle with a brake specific fuel consumption (BSFC) of 0.48. Factory 305 TPI manifolds came with 19-lb/hr injectors (the 350 engines used 22-lb/hr units) that are only good for around 270 hp at the same efficiency level.
Test TimeWe loaded up our trusty small-block Chevy and headed for Westech Performance where we bolted the 355 up to the dyno and, after some mild difficulties, created a carbureted baseline for the engine. That's when the fun stopped. After bolting on the TPI manifold, the engine struggled but never ran correctly despite our efforts. We discovered we really weren't ready to test the system because we hadn't spent enough time reading the MegaTune instructions. Eventually we also realized we had not loaded the base fuel map into the new chip we installed (see the "Installer Errors" sidebar-it's high comedy). Eventually we ran out of time and packed up our small-block and headed back to the barn.
Later, we regrouped and headed to Ken Duttweiler's facility for another shot at the dyno. This time, the engine fired right up and ran pleasantly, responding to tuning changes for a short time before an errant ignition ground caused us some grief. Once that was repaired, the MegaSquirt system responded instantly to tuning changes and within a few minutes we had tuned the entire wide-open-throttle power fuel map, making an impressive 450 lb-ft of torque with the almost-stock TPI manifold and SLP runners. We also quickly tuned the idle air-fuel and a portion of the part-throttle map before calling it a day.
ConclusionDespite some initial skepticism, it's clear that this MegaSquirt system works extremely well, becoming easy to work with once we learned how to navigate through MegaTune. There's a bunch of detailed material that isn't in this short story due to space constraints, so it's worth going up on MegaSquirt's Web site to dial yourself into all the details involved with this program. The biggest thing we learned from this project was that the system works as advertised, but that the overall project required a little greater investment than we anticipated. If you already have a complete EFI manifold with injectors, this will dramatically reduce the overall cost. We would suggest doing a cost estimate first before diving in if you're planning on spending less than $1,000 to complete a system. It's also important to note that we did not include the cost of building a high-pressure fuel delivery system.
Overall, we feel our MegaSquirt effort was successful, it worked as advertised, it is the least expensive system on the market, and it's a great way to immerse yourself in the world of EFI. The system has its limitations, as you might expect, but it will make power and do the job for a whole bunch less money, especially if you're good at shopping for parts. If you look at the MegaSquirt system as a great entry-level EFI system that will teach you all kinds of things about EFI, then you've got the right idea.