Crayon Trick? Who's heard or done this?
08-30-2004, 12:05 PM
#1
On The Tree
Thread Starter
Join Date: Jan 2004
Posts: 120
Likes: 0
Received 0 Likes
on
0 Posts
Crayon Trick? Who's heard or done this? I was shooting the...well you know with an old-timer about race cars. We got on to the top of headers and how to determine the optimal collector length. He asked me if I had ever heard of the Crayon test. At first I laughed at him but then I realized this guy was serious. He said that back in the day they would put a set of header on a car and add the longest collector extensions they could find. Prior to bolting up the collector extensions they would take a crayon and draw a line down the side of it so it ran parrellel to the ground. They would make sure is had a good heavy coat of Crayon on it. Then they would make a pass with the car. After they were done they would see how much of the line had burnt off and how much remained. At the point where they could see the Crayon line again they cut off the collector extension because in their eyes the exhaust gases had cooled enough at that point that they were begining to loose velocity.
What do you all think of his logic? Has anyone heard of this or tried this before?
What do you all think of his logic? Has anyone heard of this or tried this before?
08-30-2004, 12:11 PM
#2
12 Second Club
Join Date: Aug 2003
Location: Chicago IL
Posts: 270
Likes: 0
Received 0 Likes
on
0 Posts
Yeah thats an old trick which I am pretty sure has been proven succesful.
My uncle used to paint the collector, make a pass and then cut it off where the discoloration had occured. Don't remeber what kind of paint he used though, it might make a difference.
In general its the same philosophy and would work with our cars too, that is if you want to run open Headers.
My uncle used to paint the collector, make a pass and then cut it off where the discoloration had occured. Don't remeber what kind of paint he used though, it might make a difference.
In general its the same philosophy and would work with our cars too, that is if you want to run open Headers.
08-30-2004, 12:13 PM
#3
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
Back in the day...
This (or, I heard lacquer) was also said to be the right
way to pick your best H-pipe crossover location for
duals. The resonant pressure peak of the exhaust
note standing wave will be the hottest spot, so you
look for the hot spot and take the hole saw to it.
Idea being this would be the highest transfer to the
other side. 'Course nowadays you have X-pipes and
3" plumbing so that's all kinda irrelevant.
The other thing is, the right point depends on the
application - do you want to tune header length
to optimize peak power (like dyno queens and NASCAR
where they tend to run at a pretty fixed high RPM
point at least when the green flag is up) or do you
want to make a compromise to even out the torque
across the street driving envelope - in which case
the crayon might be melted all off the whole pipe
by the time you exercise it all.
But I figure on a nice set of stainless headers I'd
just go with what I get, rather than go hack it up.
This (or, I heard lacquer) was also said to be the right
way to pick your best H-pipe crossover location for
duals. The resonant pressure peak of the exhaust
note standing wave will be the hottest spot, so you
look for the hot spot and take the hole saw to it.
Idea being this would be the highest transfer to the
other side. 'Course nowadays you have X-pipes and
3" plumbing so that's all kinda irrelevant.
The other thing is, the right point depends on the
application - do you want to tune header length
to optimize peak power (like dyno queens and NASCAR
where they tend to run at a pretty fixed high RPM
point at least when the green flag is up) or do you
want to make a compromise to even out the torque
across the street driving envelope - in which case
the crayon might be melted all off the whole pipe
by the time you exercise it all.
But I figure on a nice set of stainless headers I'd
just go with what I get, rather than go hack it up.
