Does a drag race only car need exhaust boxes?
Because it’s easier to cut some off than to add some. Plus, all the testing I did at the track (will do some dyno testing of this stuff when my junker goes on the pump) showed that going under 18 inches almost always hurt 60 foot times and I never really found any loss at 42 inches.
It’s per header size and combination of the engine and now that you have it in the car, at the track is good, the dyno is great, but a blanket statement is not good.
To add to the mix of parameters you stated less than 18 inches is bad seems to apply to a certain set up and not all or even many. This is a very particular move when it comes to length of exhaust header extension pipe.
Some engines are numb, others very cranky over the pipe length.
When your engine hits the lie detector, IF you can, if you have another set of headers, swap them out and I’ll bet there is a change in header collector length for each header on the same engine.
I don’t see very often this being done. The few times I have seen it only leaves me baffled and above I stated why. The only time I can actually say, this XX length of pipe is what will work is because this is what the racer has done and it’s ether a track tested or dyno proven move. Otherwise I have to say, test it.
No one parameter has stood out except there is a benefit to running a header extension pipe most of the time of some length. I can say I have seen a trend.
The only place I can point to is the “Engine Masters” TV show with Freiburger/Dulchich/Brulè when they did this test. The headers used were dinky 1-5/8 & 1-3/4. Header extension pipe lengths were very different between the two headers on the same engine.
This is what David Vizard discusses in his book and on a on line video which you can find easy enough I think. He goes into header collector pipe extensions, pressure wave cancellation boxes & the rest of the exhaust system.
When time allows at my son in laws shop, we are working on my ‘79 Magnum. The exhaust is half way done. It’ll be done when it’s done since he has to make money first and service his clients needs. He has commercial accounts and average Jane and Joe’s walking through the door. So…. When he has time and is t dead tired from the week……
I’ll make a video on it.
