Dyno Day
April 2nd, 2005
(Trip Report and photos by Tim Bowsher)
April 2nd we started off with a local run the club we have never done before. It was local and didn’t even require 4WD, but turned out to be a lot more stressful then our traditional pavement run at the Scottsdale Pavilions.
While in theory it isn’t anymore stressful on the truck then a full throttle acceleration onto the highway, the chassis dyno at Arizona Dyno Chip did put 4 of our rigs through the paces. The owners of the 4 rigs who showed up were Tom Gismondi, Mike Corder, (myself) Tim Bowsher and Doug Schulz.
With only 4 people around, we were not too rushed to get people on and off the dyno. This allowed everyone to make a couple of pulls to try check repeatability and see if any little changes could be made. The timing light never came out until the last rig of the day was on the rollers. That might have made a difference for Tom. When the date was chosen at the club meeting, we had a good dozen people who were interested in attending. With the smaller turn out it was a nice relaxed pace, at least until the engines fired up.
Tom Gismondi was the first to run on the dyno. With a fresh 351 sporting ported heads and GM throttle body injection (sorry can’t remember which company made the conversion) we made the first pull of the day. There was a wide band oxygen sniffer stuck in the tailpipe to check everyone’s air/fuel mixture. Tom was slightly lean on both passes. Peak HP was 140.76 and torque was 234.98 Ft-Lbs.
(Above: Tom Gismondi)
Second up was Mike Corder. The 302 is sporting a GM throttle body conversion as well. We discovered some interesting stuff with Mike’s engine. At full throttle it goes so rich that the oxygen sensor is simply pegged at full rich. Above 3500 RPM it starts sputter from being loaded up with fuel. Simply put, this is not a race motor. But it does drive nice on the bottom end. The extra fuel going through the engine may not be the nicest for tailpipe emissions, but it should help keep the engine running cool. If you look at the torque lines on the charts, you can imagine that line below 2000 RPM. The reason there isn’t any data below 2000 RPM was that we didn’t start taking data at that low of an engine speed. HP peaked at 132.70 and torque peaked at 245.40 Ft-Lbs.
(Above: Mike Corder)
Tim Bowsher was up next with the Holley injected 351. Unfortunately the laptop connection wasn’t being happy that day so tuning on the dyno was out. I did find a few things out. The engine was running slightly lean and the tip in hesitation was from too much fuel. Playing with the fuel pressure regulator made no difference in power, but did hurt drivability.
The 4R70W was played with a little and asked to hold 3rd gear. Several runs were done to try different tricks. There was the manual control of the torque converter so I could get readings on loss through torque converter slippage. Found that having the converter unlocked up to about 70 MPH helped the bottom end and locking it above 70 MPH helped top end power. We did a couple of runs as I drove it in and the later runs were after I removed the extremely dirty K&N air filter. The dirty filter was costing me about 11 HP in places according to the dyno.
I also ran it through the gears and we checked the shift timing. Found it was shifting at 204 HP as it came off the HP peak and picked up again at 204 HP below the peak, so no need to change shift timing. I have data down to about 1000 RPM because I lugged it down nice and low, locked up the converter at idle before taking data. After several pulls it was still running and I pulled off with the best of 246.17 HP and 309.28 Ft-Lbs at the rear tires.
(Above: Tim Bowsher)
Last up was Doug Schulz with his built 5.0 mustang motor sporting cobra intake and factory ford fuel injection. This is a strong running motor. Doug spent a lot of time playing with a bunch of aftermarket stuff getting this engine running. We did find a few tings that may need attention in the future. The fuel pressure drops off at high RPMs and the mass airflow meter also pegs at peak speed. It was a little nerve racking to be leaning over the engine as it was turning over 6000 RPM at full throttle to watch the fuel pressure gauge. The fuel system that was never really built, just evolved over time. It is now time to gut the fuel system and get everything to work with the strong motor. Don’t want it going lean at the wrong time. The Bronco turned out 227.02 HP and 261.52 Ft-Lbs at the rear wheels.
This is one system that Keith can reprogram. The EEC-IV can take a custom chip to correct things like injector size, rev limit, desired idle speed. Features can be turned off if not wanted like EGR, TAB and TAD. Eliminates having to trick the computer. Hence the name of the shop, Arizona Dyno Chip. We were a little surprised that he didn’t do the older GM throttle body chips at this time.
( Above: Doug Schulz)
Three hours later we were leaving with a wealth of knowledge that none of us were expecting to know about our Broncos. What started as a simple “what does it make” turned into a learning experience. Engine tune, exhaust flow, Air/fuel ratios, tire harmonics were all part of our learning. We were informed of the errors of trying to use a trick mass airflow sensor calibrated for larger injectors. The meter lies to the computer about the amount of air entering to choke down the oversized injectors and now the computer can’t correctly calculate engine load since it doesn’t really know how much air is really entering the engine. Don’t trick the computer, just get it reprogrammed to work right.
Compliments were given on our parking ability. We could actually park between the lines instead of on them, earning us compliments from Keith. Apparently the ricers can’t figure it out and always park on the lines. Keith mentioned how he has a bronco sitting around not running. It is not running because he didn’t tie the battery down. The battery came and took out the fan, overheated the motor. This leads to a Bronco that is sitting stagnate. With how Keith was running on about an LS1, we might be looking for an LS1 powered Bronco one of these days.
For fun we started the day with a sign up sheet that included our best guess on what we though our trucks would make. Most people were guessing engine numbers, but we were measuring rear wheel numbers. So a little discussion we settled on a 30% loss as a realistic number. So the numbers we were seeing are only 70% of what the motor is making. I will admit that I was the only one estimating my rear wheel numbers.
Dyno Results:
Estimate Measured Corrected engine HP Torque HP Torque HP Torque Tom 265 300 140 234 200 334 Mike - - 133 245 190 350 Tim 225 300 246 309 351 441 Doug 300 - 227 262 324 374
