A while back I posted pictures of a homemade custom air box that seals to both the naca duct and the high pressure area of the grill. Here are some interesting details. I have not dyno'ed yet, but still have some results. I had a hard time dyno'ing last year due to the nitrous, we couldn't keep it on the wheel. That was solved by road tuning using a logger and measuring the slope of the rpm curve. If you can accurately measure the rate of rise of the rpm curve you can calculate hp. In my case the logger has a built in accelerometer and the two quantities can be cross checked.
Here are some facts, in third gear (2500-5000 rpm) with 3.33 gears and level ground with two people aboard the car did the following:
NA: 546 rpm/sec
100 shot: 650 rpm/sec
200 shot: 710 rpm/sec
300 shot: 865 rpm/sec
325 shot: 900 rpm/sec (52 to 87 mph in 2.2 sec)
All runs needed drag radials, except the NA runs. These are all averages of several runs at each level.
These are all repeatable numbers and have been logged mutiple times, sorry about the long route here, but, this is the interesting part. Over the winter the following was done:
1. We fixed a vacuum leak caused by the shop that did the head porting. They never milled the intake side of the heads after milling the block side.
2. Had the intake matched to the heads.
3. Installed the sealed cold air box.
All of these should notadd that much hp, but here is the data:
638 rpm/sec with 3.07 gears, whereas in NA previously withh 3.33's it went 546 rpm/sec. This was the average of three runs. The 638 is comparable to a 100 shot which was 650 rpm/sec. Even if the rear wheel 100 shot was 75-80 hp, these simple mods brought 60-70 hp. What is interesting, when the car is floored at 2500 and starts accelerating, when the car reaches approximately 4300 rpms it feels like the car drops into another gear. On all three runs the tires (pilots) break loose at 4300 when it hits that spot. It shows up on the log also. I have to think it is the cold air box. The car ran one full point leaner than last year across the full wot curve, with the vec i brought it back to about 12.8.
The final point, all last year the logger showed the IAT approximately 20 degrees higher than ambient with the cones. This year with the sealed box the IAT is 5 degrees hotter than ambient.
Here are some facts, in third gear (2500-5000 rpm) with 3.33 gears and level ground with two people aboard the car did the following:
NA: 546 rpm/sec
100 shot: 650 rpm/sec
200 shot: 710 rpm/sec
300 shot: 865 rpm/sec
325 shot: 900 rpm/sec (52 to 87 mph in 2.2 sec)
All runs needed drag radials, except the NA runs. These are all averages of several runs at each level.
These are all repeatable numbers and have been logged mutiple times, sorry about the long route here, but, this is the interesting part. Over the winter the following was done:
1. We fixed a vacuum leak caused by the shop that did the head porting. They never milled the intake side of the heads after milling the block side.
2. Had the intake matched to the heads.
3. Installed the sealed cold air box.
All of these should notadd that much hp, but here is the data:
638 rpm/sec with 3.07 gears, whereas in NA previously withh 3.33's it went 546 rpm/sec. This was the average of three runs. The 638 is comparable to a 100 shot which was 650 rpm/sec. Even if the rear wheel 100 shot was 75-80 hp, these simple mods brought 60-70 hp. What is interesting, when the car is floored at 2500 and starts accelerating, when the car reaches approximately 4300 rpms it feels like the car drops into another gear. On all three runs the tires (pilots) break loose at 4300 when it hits that spot. It shows up on the log also. I have to think it is the cold air box. The car ran one full point leaner than last year across the full wot curve, with the vec i brought it back to about 12.8.
The final point, all last year the logger showed the IAT approximately 20 degrees higher than ambient with the cones. This year with the sealed box the IAT is 5 degrees hotter than ambient.
