Throttle Body Injection September 2004

If you’ve been following this project you’ll know the big push was to get a car to The British Invasion car show in Stowe, Vermont for the weekend of Sept 18th. We did it! Special thanks to Aaron Cropley for allowing me to use his prized 71 TR6 as a test bed. Aaron’s car is a bone stock TR6 with about 20K miles on a rebuilt engine that has been overbored .020″. There were many late nights as the deadline approached. The show deadline helped push the project along after taking it easy this past summer.

The car was actually not even running properly until 3AM Wednesday morning. Aaron put on about ten miles on Thursday and off we headed on a five hour trip on Friday morning! The trip to Stowe up through the mountains of New Hampshire and Vermont was pleasantly uneventful. I followed Aaron and Kim and just couldn’t stop grinning.

Back to Wednesday; That morning we were still without an operating ECU. CustomEFIS had overnighted the last components from Georgia to arrive in Maine Wednesday afternoon. CustomEFIS was standing by in case of difficulty. Now I should mention that while we were on the phone with John of CustomEFIS he was preparing his family and home for hurricane Ivan. We caught up with him on his way home with candles, bottled water and the like. By the time we were ready to fire it up the hour was late and the wind was picking up in Georgia. The engine fired right up but was running fat. We plugged a laptop into the ADL connector and emailed the datalog file to John for analysis. Within minutes it was determined that the throttle position sensor (TPS) was operating backwards! I had picked up the wrong TPS. Now it’s 11:30 at night and time is really running out. John suggested that we reverse wire the TPS and try it. WOW! It ran great and it was only 2AM.

Earlier that week I’d purchased an AEM air/fuel ratio meter that uses a wide band Bosch O2 sensor. Extra bungs were welded into the down pipes of both cars and the power cord wired with a cigarette lighter plug. This set up could quickly be moved from one car to the other. Remarkably the TBI car ran just about optimum ratio of 14.7 to 1 immediately. I shouldn’t have been surprised as that is exactly what it should do. The ratio would richen on acceleration and lean out on deceleration. It was 3AM and time to experiment was over. The meter showed that the ratio was right on target and I felt confident that we wouldn’t damage Aaron’s engine. Thursday was used to neaten up the installation, bundle wires, mount the computer (ECU), and spend a few minutes cleaning the cars. Friday morning it was off to The British Invasion.

The trip was delightfully uneventful but there are a couple of small items that eventually will need attention. As we prepared to depart on the trip the fuel pump started making a whining noise. It was cavitating because it’s intake was restricted by debris from the gas tank. I had opted to not use an intake filter hoping that the pump’s intake screen could handle debris. Starting and stopping the engine revealed that sometimes it whined and sometimes it didn’t. Evidently it depended upon where the debris ended up against the screen. We headed off without remedying the noise. After the trip we took apart the intake side and there was quite a bit of dirt plugging the intake so a very coarse in line diesel filter was added ahead of the pump.

The other item was that the idle was smooth but higher than spec. At times it would run about 900 and at other times closer to 1200 and occasionally as high as 1500. After a bit of troubleshooting it became obvious that we have a vacuum leak providing enough air that when mixed nearly perfectly with fuel, caused the high idle. Best guess is that the carb’s bypass valves are the culprits. Will let you know but in the meantime Aaron will be on the road with the only TBI TR6 in the world. Neat. Really neat!

These photos are of a fuel injected TR6. Look closely.