Zoomies vs collector headers

[Roger]

In a current thread there’s been a conversation about collector headers and zoomies on FEDs. I agree with most, zoomies belong on FEDs and I think they also belong on altereds. With that said, has anyone out there done an actual comparison between the two? I’ve been studying, or trying to, the difference in performance between the two. The only actual dyno test information I’ve been able to find is one conducted by Joe Sherman in which he stated “have seen as much as 55 or 56 HP (less) on a 1000 HP engine“ compared with collector headers. Now zoomies won’t have the inertial scavenging of a correct length and diameter pipe (roughly 28” to 34” long) because they are to short and it won’t have the wave scavenging of the collector because there’s no collector to share the wave with other cylinders. But what a set of zoomies have working for them while hanging out in the breeze at 180mph is the Bernoulli principle effect on drawing exhaust out of the cylinder. That’s the same effect that draws fuel out of a carburetor bowl and draws a crankcase vacuum with a pan-evac system. Any comparative tests out there of zoomies vs headers or any thoughts?

[dreracecar]

7 seconds is not enough time to worry about scavanging
On a blown car the collector outlet area is restrictive vs open pipes
For what I have seen, the dyno shop has headers set up to use in their room with all the hook-ups, and there might be a difference between those and the headers that fit the vehical, also consider that open zoomies in the dyno room without someway of collecting the exhaust, contaminate the air in the room, which hurts performance.
NASCAR teams spend $100,000's on header designs and dyno testing because the runs are longer and take advantage of every  single 1 hp gain, If they change cams, it might also need a header swap. We on the other hand are happy if they just fit right off the shelf

[coupemerc]

I know that Bill (masracingtd1167) has run his FED with both header types. His engine is a normally aspirated SBC on methanol. It used to be quicker with the 4 into 1 collector headers but recently he made some changes to the car and ran his best et ever. I think he had the zoomies on it. Maybe Bill will chime in on this thread.
I agree with what Sherman said. Recently I went to the dyno with my injected, methanol SBC. I run zoomies on the car and I did not want the scavenging effect of collector headers to give me bogus (higher) dyno numbers. I ended up using custom dyno headers that are basically 12" long zoomies that dump into an 8 inch "log". They were more representative to what I run on the car. The idea came from Scott Parks.

[masracingtd1167]

I can't honestly say witch one is quicker ! I have been using a collector header on my cars for a long time and we always ran quicker with them ! When I built the zoomie headers for my current car my plan was to slow the car down for 7.50 racing and I did not notice much difference in performance at all ! Back when we started running the collector headers we were also running on gasoline and the headers were worth a solid tenth !I think the only way to really tell the difference is with an a to b to a test . Also about 10 lbs lighter with the zoomie header . This picture is from the early seventies   

[JrFuel Hayden]

My experience with dragster pipes has been it depends on the fuel, head flow, and RPM. When we were running a non-raised runner 23° Iron SBC, we used 1 5/8 pipe zoomies, on alky, then as we started running raised runner heads, we increased the pipe size 1 3/4, then 1 7/8, then 2" and now with the bigger cam, and 10,000 RPM, we have 2 1/8" zoomies.
On my 1'st 1962 dragster, C/D on gas we tried different pipes based on formulas , we didn't learn enough, since it broke allot and only race it a year. Next dragster I ran for 5 years [63-68] it was a real nitro JrFueler, again we tried long pipes, short pipes, different pipe sizes, For us none of the formula pipes seemed to make a difference burning nitro. I ended up with just about 8" zoomies, because they were just lighter, and out of the way to work on the valves, etc.  The other thing is we always aimed the traditional zoomies back toward the slicks. Remember the big deal on the funny cars zoomie angles last year, action/ reaction, helps moves the car forward. I had a B/ND motor in a car and I put my angled zoomies on it and took the mostly upright zoomies off. The car picked up MPH.
I don't know any team that has found any improvement while burning injected alky. I know of one team that runs collectors on his injected alky, and he said he just picked 4-1 because he just wanted to look different and he runs the 7.60 class, and not looking for max performance. 
Good Luck
Jon

[dreracecar]

Plus it keeps the rocks out of his engine without have to use covers

[Roger]

I agree with Bruce that a blown car with a lot of exhaust volume probably doesn’t need or work well with headers. For now I don’t have a blower and was looking at this more through the lens of a naturally aspirated engine. It’s interesting that Bill’s cars were a tenth or less slower with zoomies. Having been told they don’t work well in the past with n/a engines I was curious as to how much the engine performance was actually affected and at least in his instance it wasn’t much, if any. Of course the car would weigh less with the zoomies. The ones I have weigh 10# for the pair and the headers I have for the street rod engine weight 34#. Now Jon brings up an interesting point about how far to lay the pipes back from vertical. With the case of big show cars they have a huge amount of exhaust that’s angled rearward to propel them forward compared to a smaller volume and force from a junior fuel car. So while there is some exhaust volume to propel the J/F forward, is there an optimal angle to lay the pipes back to get maximum benefit from the Bernoulli effect? Ya, this is splitting hairs but I’ve always told the kids in my classes that in order to do something right the first time you must have some knowledge of it before you start. Thought Scott’s idea of the test zoomie thingy on Chuck’s car was I good idea. Kind of reminds me of some of those old lakester style headers on steroids!

The pictures show the Bernoulli effect. First photo is a glass of dyed water with a straw in it. Second is the same glass and straw with 60psi blown across the opening. In this case it drew 3-1/2” of water.

[George]

Agree. Ya, this is splitting hairs. 

[THE FRENCHTOWN FLYER]

I wonder what 60 psi equates to in FPS/MPH?

[dreracecar]

My question on the "tenth or less" statement,   was the test done on back to back same day runs??? under the same conditions??

[masracingtd1167]

When we first tested with collector headers was a long time ago and yes it was same day same conditions . That being said we were running injected on gasoline in c/d so a tenth was a huge gain ! So I stuck with that theory for years ! Like I said we put the zoomey on recently and noticed no change but it was different days . This season I will try a a to b to a test just to see what happens !

[denverflatheader]

My first response would be the glass of water is in what could be termed a low pressure condition.  Within an engine’s exhaust system, there would be again what I’ll term low pressure condition as long as the engine is not expelling exhaust.  Once the exhaust pulses start, the low pressure condition would diminish, and as the engine rpm increases from idle to redline, the low pressure condition may not be measureable.  My guess is the Bernoulli effect shown by Roger’s example may also diminish with higher rpms.  That being the case, design the exhaust exit for optimal forward thrust and traction.

Agree there’s hp increases with properly tuned exhaust, however, even more hp gain with camshaft options.  Back to Roger’s question; if you want every single hp, you must design your exhaust system properly.  If you have headers and collectors with incorrect tube diameter and length for your engine and camshaft application, you might be equal or even outperform that "mistake" with a suitable set of zoomies.

Here’s a well written article on effects of camshaft design on scavenging from Specialty Products Design, Inc., Company started by Jim Hill.  Note possibility on achieving greater than 100 percent volumetric efficiency:

“The exhaust systems role in increasing engine performance centers around improving volumetric efficiency. Volumetric efficiency (VE) refers to the ability of an engine to intake and expel gases (i.e.: air/fuel and exhaust gas), in relation to the actual pumping volume of the engine. Free flowing intake and exhaust systems help an engine to achieve this. Achieving greater than 100% VE is done in part by optimizing exhaust gas scavenging to draw out exhaust and bring in air fuel mixture during valve overlap. As the piston reaches the top of the exhaust stroke, it dwells as the crankshaft sweeps across the top of its stroke. This is where valve overlap occurs. Before the piston reaches Top Dead Center, the intake valve begins to open. The trick is to design the exhaust system so that the exhaust pulse (pressure wave) leaves behind a pressure drop or vacuum to take advantage of the valve overlap. If successful the combustion chamber will exchange residual exhaust gases for a fresh air/fuel mixture before the piston has any real effect on the intake charge.

To design a successful exhaust system or tuned header, the tube size and length are selected based on a list of engine specifications and application characteristics. The tube size controls the speed of the exhaust pulse, too big and the velocity (energy) is lost. The tube length is all about timing the pulse to synchronize with the cam in a specific RPM range. 

At the collector, the timing of the pulses is crucial to scavenging. Imagine a four lane freeway on ramp merging into one lane. If you get the timing and speed right, the pulses draft each other like stock cars at Daytona, increasing their speed.  This is where the Merge Collector comes in. It makes that transition from primary tube to collector as smooth as possible. This reduction in turbulence helps maintain velocity through the collector, thus increasing the scavenging power of the header system.”

[wideopen231]

Ok while we are on exhaust flow and zoomie. Old thing from harleys especailly with drag pipes.They made a cone shaped piece that goes in between pipe and head.Idea it icreases velocity.Band aide for improper pipe being used.Dragpipes suck IMO.They add some needed restriction also.

question has anyone tried this on N/A engine,especailly with zoomies? Have thought about making a set to test at some time.

Probably well know but here is another thing on flow.The adapters made for sbc running bigger pipes that relocate bolt holes can also increase exhaust.Ind cylinder heads was selling plate for Hemi heads at one time 500 per set.Mine cost 100 per 3 sets and two days on mill.You have to match ports in basically make it a longer port.Now this was all done on blower motors and be beifit for N/A motors.

[dusterdave173]

I know that when I ran a door car we ran about an 18 inch torque tube on the end of the collector--we started with about 2 ft --put a yellow tire marker crayon line down the tube--made several good runs and the wax crayon would be burnt to a certain distance we cut he pipe off right there--Car ran faster and the 60 ft was better--the sound of the car changed so much I could not believe it--folks beside the starting line always covered their ears after we 'tuned" that header--it was awful to be inside or beside of it during burnout!! Would knock your ear drums out

[dreracecar]

Jim Fueling (rip) came up with those anti-reversion cones/headers back in the late70's, if they worked, they would still be used today you think?
 Again, long runs at a constant rpm could show some improvment (B'ville) but for the short duration of a drag race and that the classes that allow collectors are index/bracket---whats the point??