First some background information. I have a 1st gen CRX with a newly swapped B16. I installed a Vortech fuel pressure optimizer and a B&M underhood fuel pressure gauge. I have been trying to get into a local shop for two weeks to get it dynoed. They keep putting me off and saying “we have a car on the dyno” even though I have been scheduled for two weeks. I saw them tune 15 whp just by changing fuel pressure and I think a little timing on another crx B16 swap so I was curious. Anyway I decided I would see what gains I could make on my own. I have only ran a 15.1 ¼ mile so far so I want to improve this. This is on crappy 185 60 14’s and sloppy stock suspension at 4,500 ft above sea level at about 85 deg F. I figured on at least 14’s but I just can’t make it. The car only weighs 2,040 lbs with me in it. Oh and my 60ft times are 2.3-2.4 sec. So on with my test. I went out to a “flat” “empty” road about a mile long with mild wind conditions. I took along my trusty $15 stopwatch and my wife. I started off in second gear and took it up to 3K rpm “EXACTLY” I had my wife say 1,2,3 go and I punched it up to 4K rpm. We did this until we were getting consistent 1.53 to 1.56 second pulls so we knew we would be consistent on the real tests. This took 8-10 runs. The important thing is to get consistent when practicing. Now the real test. I only tested from 5-8K rpm since that’s all I care about for drag racing. I tested 3 different fuel pressures to see which made the most power. First I tested 40 psi fuel pressure which is what I ran that 15.1 ¼ mile at. I logged the following times:

1.75 1.67 1.84 1.93 1.66

The average time was 1.77 seconds. It is very important you get 5 or 6 runs for a good average. As good as my wife and I were at this we couldn’t get exactly the same time every time but pretty damn close. Next I tested at 37psi fuel pressure and here is what happened.

1.79 1.65 1.75 1.56 1.73 1.76

The average time was 1.70 seconds. Next I tested 43 psi fuel pressure and here is what happened.

1.79 1.87 1.77 1.99 1.77 1.77

The average time was 1.82. It’s obvious to me that the leanest setting was the fastest. Since I ran that 15.1 with a fuel pressure of 40 psi then I should be even faster at the track running at the lowest fuel pressure setting that I tested yesterday. How much faster? Look at the averages again and you will see this.

37psi = 1.70 40psi = 1.77 43psi= 1.82

I cut .07 seconds off my average time using 40psi just by moving the fuel pressure down to 37psi. And this is my gain just in first gear. Since I go through 5-8Krpm in second gear also and then again in 3rd gear I can say that if I make these gains in each gear I use that rev range then I can take that .07 and multiply that by 3 and get .21 seconds or 2/10ths of a second and dropping down in the 14’s up here. I know as I go up through the gears these gains in time won’t be exactly what they were in 1st gear but pretty close since the car is light. I think it will go something like this actually. 1st gear I lose .07 2nd gear I lose .06 and 3rd gear I lose .04. That means overall my ¼ mile times should be .17 seconds faster at this fuel pressure. I have no data to back that up but the gain in first gear is proven so all I can do is extrapolate the overall time I will lose. In any case this is something you can do in about an hour and for $15. I didn’t want to go any lower than 37psi for fear of leaning out to much but if I could spend $15 and one hour of my time for almost 2/10ths in the quarter I would do it again. I have a book that tells you how to calculate actual wheel horsepower but you need a stopwatch and a standard g-meter. I would have to go back and read how accurate it was found to be but If I recall right it was pretty damn close. I will post the recipe tomorrow.