View Full Version : Dyno testing headers and air filter on a new 347
I recently built a new 347 for a fellow Factory Five owner. Pretty standard build 10:1 compression, AFR 185 heads and a comp 35-518 cam. One difference on my engine dyno setup is that we run all accessories and the actual headers and sidepipes from the car. So, these numbers are a bit lower than you might see from other shops who use dyno headers and no accessories. Attached are 3 dyno runs. The first is using 1 3/4 tube FFR headers, I believe they were made by Hooker, and no air cleaner. The second run was adding the oval Cobra air filterwith 2" element. Finally since I had a set of BBK 1 5/8 headers on the wall I wanted to compare the 1 3/4 vs 1 5/8 primary diameters. The headers were virtually identical other than tube size. I removed the air cleaner for this test so we had no other changes from the original run. I expected a low end torque increase with the smaller tubes but that doesn't seem to be the case. Maybe at very low rpm but did not test it that low. Anyway attached are the results.
Bob
Jeff Kleiner
03-07-2021, 05:36 PM
Interesting results; thanks for posting that Bob!
Jeff
GoDadGo
03-07-2021, 09:19 PM
It's always interesting to see minor changes tested under a controlled environment.
..................Thanks-O-Million For Sharing Your Results!
AdamIsAdam
03-08-2021, 10:04 AM
So the air cleaner lost 11hp. Was the base flat or a drop-base type? When Engine Masters did a big air cleaner shootout, they found that the flat base was much better than any drop base, even if it meant having to run a small air filter.
On my car, similar 347, when I added the air cleaner (flat base oval) it actually made +6hp. I figure that was more likely due to the engine getting nice and heat soaked. But at least it didn't go down! Here's my dyno chart.
EDIT: I went back and looked at my 3 pulls.
#1 was air cleaner on, hood open. 374hp.
#2 was no air cleaner, hood open. 379hp.
#3 was air cleaner on, HOOD CLOSED, 384.6hp. Either the car was running a bit better as the day went on or it likes the hood closed with the air cleaner on best for some crazy reason.
143963
143966
So the air cleaner lost 11hp. Was the base flat or a drop-base type? When Engine Masters did a big air cleaner shootout, they found that the flat base was much better than any drop base, even if it meant having to run a small air filter.
On my car, similar 347, when I added the air cleaner (flat base oval) it actually made +6hp. I figure that was more likely due to the engine getting nice and heat soaked. But at least it didn't go down! Here's my dyno chart.
EDIT: I went back and looked at my 3 pulls.
#1 was air cleaner on, hood open. 374hp.
#2 was no air cleaner, hood open. 379hp.
#3 was air cleaner on, HOOD CLOSED, 384.6hp. Either the car was running a bit better as the day went on or it likes the hood closed with the air cleaner on best for some crazy reason.
143963
143966
Air filter was flat based.
There are so many variables it's very difficult to pinpoint changes. A lot of times you'll see air fuel ratio changes by adding or removing air filters that can affect power. Maybe the fans on your chassis dyno were affecting air flow, causing turbulence, etc. and closing the hood changed that dynamic. You really have to take each change and see if it repeats. Was your dyno using a weather station. Maybe correction changed for some reason. When you see something out of the norm like that you really need to repeat the test and try to determine what is really happening if it's of interest.
AdamIsAdam
03-08-2021, 12:17 PM
Interesting perspective on changes. I do not think this dyno was connected to weather station. Hmm, here's a pic of the car on the dyno. Looking at that big fan... your idea could be spot on. Close the hood and more air may have come in through the grill and hood scoop.
GoDadGo
03-08-2021, 12:23 PM
Interesting perspective on changes. I do not think this dyno was connected to weather station. Hmm, here's a pic of the car on the dyno. Looking at that big fan... your idea could be spot on. Close the hood and more air may have come in through the grill and hood scoop.
I watched only a few of Dyno Pulls (Engine Only Type) that were done back to back and heat soaking seemed to reduce the output by a few ponies as time progressed.
Once things cooled off the ponies came back and fell off as things got hot.
Heck, air quality is another huge factor too.
AdamIsAdam
03-08-2021, 12:36 PM
I watched only a few of Dyno Pulls (Engine Only Type) that were done back to back and heat soaking seemed to reduce the output by a few ponies as time progressed.
Once things cooled off the ponies came back and fell off as things got hot.
Heck, air quality is another huge factor too.
So we're told. But there's a balance. An old time, very well respected Pontiac engine builder/racer told me most engines, especially street engines, need a certain amount of heat in them to produce peak power. And this guy takes his cars to the track weekly and he methodically tests each change. He's the one who told me you need some heat in your engine. How, AIR and FUEL should be cool for obvious reasons but not the actual engine. Again, within reason. The last two cars I've owned and dyno'd, one a 469cid Pontiac motor, the other this one, both saw power increase over the first pull. All over a short period of time, like within an hour or less. Not like all day where temps can change.
I'm sure those much more knowledgeable than I can add/correct this info. It's what I've been told and what my limited experiences showed me. Oh, and that's also backed up by my day at the drag strip with my GTO as well. Car got faster after the first few runs. (Of course, many more variables at play, ie, the driver there.)
I generally see power increase on successive dyno pulls, especially with aluminum heads. They need that combustion chamber heat. As far as air quality, most engine dynos have a weather station that will correct on every pull. But I have seen instances where smoke or dust in the air can affect the power and the weather station cannot detect it.
Rdone585
03-08-2021, 09:16 PM
I was present when my engine was fresh and first put on the dyno. The builder had a controlled room so he new what he was working with. He made sure the oil was up to the proper temp, and the engine block as well. He controlled the air/fuel ratio also before he ever made the first pass. Then after break-in and the first couple of runs he started adjusting carb jets. He made sure all the variables were at least above minimum baseline before each pass. The one thing that was an uncontrolled variable was the barometric pressure, that was the luck of the draw depending on the weather that day. Even so he had a correction factor so he could compensate for it to compare results seen on previous days. Of course this is an engine dyno, so the results will vary from those when running in car, rear wheel runs.
I've seen correction factors change over 5% in just a few hours when a weather system rolls through.
mcondos
03-09-2021, 02:39 PM
Thanks for the info Bob! Just curious which side pipes were used? thanks!!
Thanks for the info Bob! Just curious which side pipes were used? thanks!!
I have a set of pipes that I cut off and welded straight tube in place of the muffler. These then connect to my dyno mufflers. No power loss through that muffler.FYI I previously did an extensive muffler test and documented that the stock mufflers cost no power at the 500hp level.
AdamIsAdam
03-09-2021, 03:33 PM
I have a set of pipes that I cut off and welded straight tube in place of the muffler. These then connect to my dyno mufflers. No power loss through that muffler.FYI I previously did an extensive muffler test and documented that the stock mufflers cost no power at the 500hp level.
Which stock muffler? You mean the FFR side pipes?
Interesting info. They are so loud I can imagine they would not rob HP! LOL
I'm about to install Gas-N touring pipes. I'm willing to sacrifice a little HP for some quiet. 95dbl at idle is just too much.
Which stock muffler? You mean the FFR side pipes?
Interesting info. They are so loud I can imagine they would not rob HP! LOL
I'm about to install Gas-N touring pipes. I'm willing to sacrifice a little HP for some quiet. 95dbl at idle is just too much.
I tested stock FFR mufflers, open headers, Flowmaster Slimlines and a custom set that I built. I did noise measurements and power measurements. I wish I could have gotten some Gas N's to test. To my knowledge no one has run a comprehensive dyno test on them for power loss. None of the headers in my test cost power over open headers. The Flowmasters actually showed an increase.
Here's a link to all the muffler testing I did.
https://www.ffcars.com/threads/muffler-testing.544713/
Bob
AdamIsAdam
03-09-2021, 07:08 PM
Awesome! Rolling up my sleeves and reading that thread now. It's like Engine Masters all over again. Too bad you couldn't find someone who was planning to buy Gas-N pipes to lend you theirs before installing them. I would have done that - ya know, in the name of science! LOL
EDIT: when I got to the YouTube video I realized I'd seen it before. Heck, it's in my "Cobra" bookmarks folder! LOL
Lickity-Split
03-09-2021, 08:03 PM
The above air cleaner results were interesting.
I run a 2,000 LB, 406 powered bracket car on Methanol. With an air cleaner on it the car will consistently ET about a half a tenth quicker. My thought was that the air cleaner better directed the air flow into the carb.
seagull81
03-10-2021, 10:43 AM
Bob, I think Glenn R. has a set of Gas N pipes sitting in his garage. He might let you test them some day.
GoDadGo
03-10-2021, 11:05 AM
I generally see power increase on successive dyno pulls, especially with aluminum heads. They need that combustion chamber heat. As far as air quality, most engine dynos have a weather station that will correct on every pull. But I have seen instances where smoke or dust in the air can affect the power and the weather station cannot detect it.
Thanks for giving me something to think about.
We must have been running mine lean plus I'm running Iron Eagle Heads.
I need to go back and look at my sheet to see what the A/F ratio was because you've got me wondering.
Bob, I think Glenn R. has a set of Gas N pipes sitting in his garage. He might let you test them some day.
I talked to him about testing them but time just got away from us and I think Tom was ready to get that engine back in his car.