"Sharp edges" possible issue on intake after 62mm throttle body upgrade causing whistle?

I wonder if I could talk Jim Repp into joining this forum, he'd easily put the kabosh to the butt-dyno fueled rumors that bigger throttle bodies or different air intakes cause the engine to produce more power. But then what does he know? He was only Jeep's chief design engineer who recently retired after having started in the CJ days. If anyone wants to 'friend' him on Facebook to ask him directly, he's there as James Repp. Jim was also the creator and and reason for the Jeep Rubicon which was his baby from start to finish.
 
The throttle does feel stiffer as well so that could lead to the feeling of better acceleration and throttle response, it at least feels better to me even if that’s not what the facts say.

The larger bore puts more meat in the lower half of the flow vs position curve, so you might be getting volume equivalent to 40% throttle on the OEM TB at 30% on the big TB. A lot of drive by wire cars accomplish the same sensation in "sport mode", which just opens the butterfly more aggressively for a given pedal position, but since the TB isn't changing, actual performance is still identical; it just happens with less input from your foot.

As for whether a larger TB actually adds performance, that's a matter of whether the stock TB presents a restriction at high rpm WOT that can be reduced with a larger throat diameter. A previous poster has already suggested that dyno results suggest it does, but then there's the question of whether reducing that restriction results in any real world performance gain, and there are varied opinions on that.

As for me, I wouldn't buy one, but if I had one, I probably wouldn't remove it unless it was causing me problems. I would consider annoying noises to be a problem.
 
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I haven't dyno tested the throttle body personally. I know that Newcomer did a video where they tested a range of throttle bodies as well as intake manifolds. He did his testing on a modified stroker 4.0, so the airflow demand would not be the same as a stock 4.0. The larger 65mm throttle body in his video made significantly more power on his stroker. That testing was done on an engine dyno. My testing on the intake tube was done on a chassis dyno, not a butt dyno. The results of my testing were conclusive. The aftermarket tube picked up 8+ hp and about 5 ft/lb. Those results are in line with the results of others that have been dyno tested as well. That video is here if anyone wants to see that test.


Also, I do have a bone stock TJ sitting here and an aftermarket throttle body to test. I just don't have a factory one that I know of. I will look around as I think actual tests of these things are important. I prefer to deal in facts, not opinions.
 
I haven't dyno tested the throttle body personally. I know that Newcomer did a video where they tested a range of throttle bodies as well as intake manifolds. He did his testing on a modified stroker 4.0, so the airflow demand would not be the same as a stock 4.0. The larger 65mm throttle body in his video made significantly more power on his stroker. That testing was done on an engine dyno. My testing on the intake tube was done on a chassis dyno, not a butt dyno. The results of my testing were conclusive. The aftermarket tube picked up 8+ hp and about 5 ft/lb. Those results are in line with the results of others that have been dyno tested as well. That video is here if anyone wants to see that test.


Also, I do have a bone stock TJ sitting here and an aftermarket throttle body to test. I just don't have a factory one that I know of. I will look around as I think actual tests of these things are important. I prefer to deal in facts, not opinions.

I know we're a bit off topic now, but I thought that one of the main concerns with these mods was that after the mod, the computer would recalibrate after a while, and make the short-term results go away? Or was that for some other mod that was being tested and discussed on the forum?
 
I wonder if I could talk Jim Repp into joining this forum, he'd easily put the kabosh to the butt-dyno fueled rumors that bigger throttle bodies or different air intakes cause the engine to produce more power. But then what does he know? He was only Jeep's chief design engineer who recently retired after having started in the CJ days. If anyone wants to 'friend' him on Facebook to ask him directly, he's there as James Repp. Jim was also the creator and and reason for the Jeep Rubicon which was his baby from start to finish.

Actually, I like the idea. Or if he's not one to join a forum and type out his thoughts, I wonder if you could look at this with him and then type up what you two take to be your response to the comments there.

I for one would also be interested to know how/whether these answers differ for the 2.5 4-cyl.
 
The results of my testing were conclusive. The aftermarket tube picked up 8+ hp and about 5 ft/lb.
"once you get down in the 5 percent range on the average chassis dyno in the average facility, it is difficult to evaluate whether the change is real or due to environmental transients."

Snipped from https://www.motortrend.com/how-to/hrdp-0405-chassis-dyno-guide/.

Your data is flawed, as all of the 'increases' you are claiming are well within the margin of error just on the repeatability of the dyno alone. How did you normalize the conditions of each pull? Was the test vehicle engine within an acceptable temperature from pull to pull? (within a few degrees) How about the transmission, differential temps? (oils will warm up and allow less friction equaling more mesured power) Were the tires contacting the drums the same (again within a couple degrees) temperature each run? (tires warm up and change diameter - grow- again increasing measured power).


Ignoring all that...

Your test result 'increases' were all in the upper RPM band, where 90% or more Jeep owners will never venture into anyway.
 
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"once you get down in the 5 percent range on the average chassis dyno in the average facility, it is difficult to evaluate whether the change is real or due to environmental transients."

Snipped from https://www.motortrend.com/how-to/hrdp-0405-chassis-dyno-guide/.

Your data is flawed, as all of the 'increases' you are claiming are well within the margin of error just on the repeatability of the dyno alone. How did you normalize the conditions of each pull? Was the test vehicle engine within an acceptable temperature from pull to pull? (within a few degrees) How about the transmission, differential temps? (oils will warm up and allow less friction equaling more mesured power) Were the tires contacting the drums the same (again within a couple degrees) temperature each run? (tires warm up and change diameter - grow- again increasing measured power).


Ignoring all that...

Your test result 'increases' were all in the upper RPM band, where 90% or more Jeep owners will never venture into anyway.

That's not the point though, is it. Everyone says they don't increase HP, but his test proves they do, repeatedly.
 
I have to TJ's, a 2000 sport ,5 speed 35" tires, 4;56 gears and stock 4.0L. The other is a '05 Rubicon, 6 speed, 35" tires and stock (4:10) gears with 4.0L that has Banks intake and exhaust and Edge TB and module installed by previous owner. Both have around 140K miles. On road the '06 accelerates and pulls a lot better. Maybe it's because of the 6 speed but lot more fun to drive.
Both engines seem to be in good condition, no oil use or any other problems.
Not trying to argue with anyone, just relating my experience.
 
I know we're a bit off topic now, but I thought that one of the main concerns with these mods was that after the mod, the computer would recalibrate after a while, and make the short-term results go away? Or was that for some other mod that was being tested and discussed on the forum?

That is only part true. The PCM can only learn changes for fuel. It cannot learn spark changes. The fuel trim changes are limited to closed loop conditions. Those conditions typically only exist from idle to around 75% throttle. Above that the PCM is in open loop where it uses base tables and limited inputs to determine fueling. If you make changes to airflow the PCM will adjust the fuel in closed loop to stoich. Those changes are limited to closed loop operation. If you increase the airflow the engine will lean out until the PCM adjusts. Which is why sometimes the engine feels stronger right after the mod, but then seems like over time it goes away. That is the PCM adjusting the fuel richer to return the mixture to stoich. The fact is if the PCM has to add fuel to return to stoich you are making more power. Engines are simple, more air = more fuel = more power. The PCM still cannot adjust for WOT so no changes take place there. I truly believe that a stock engine with a good intake and a tune might have as much as a 20 hp gain. Maybe more with an exhaust.
 
"once you get down in the 5 percent range on the average chassis dyno in the average facility, it is difficult to evaluate whether the change is real or due to environmental transients."

Snipped from https://www.motortrend.com/how-to/hrdp-0405-chassis-dyno-guide/.

Your data is flawed, as all of the 'increases' you are claiming are well within the margin of error just on the repeatability of the dyno alone. How did you normalize the conditions of each pull? Was the test vehicle engine within an acceptable temperature from pull to pull? (within a few degrees) How about the transmission, differential temps? (oils will warm up and allow less friction equaling more mesured power) Were the tires contacting the drums the same (again within a couple degrees) temperature each run? (tires warm up and change diameter - grow- again increasing measured power).


Ignoring all that...

Your test result 'increases' were all in the upper RPM band, where 90% or more Jeep owners will never venture into anyway.

I disagree. The tests were all very repeatable. On one of the previous tests I put the stock airbox back on after the cold air and the power dropped again. If you watch the video you can see that the numbers are super repeatable. Pull to pull within a horsepower or two. The dyno was also done on a warmed up engine and drivetrain. I had done probably 15 or 20 pulls before the video. I have been doing this professionally for over 20 years.

Also, if you pay attention to the scanner from pull to pull the ECT and IAT values are reasonably similar.
 
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That is only part true. The PCM can only learn changes for fuel. It cannot learn spark changes. The fuel trim changes are limited to closed loop conditions. Those conditions typically only exist from idle to around 75% throttle. Above that the PCM is in open loop where it uses base tables and limited inputs to determine fueling. If you make changes to airflow the PCM will adjust the fuel in closed loop to stoich. Those changes are limited to closed loop operation. If you increase the airflow the engine will lean out until the PCM adjusts. Which is why sometimes the engine feels stronger right after the mod, but then seems like over time it goes away. That is the PCM adjusting the fuel richer to return the mixture to stoich. The fact is if the PCM has to add fuel to return to stoich you are making more power. Engines are simple, more air = more fuel = more power. The PCM still cannot adjust for WOT so no changes take place there. I truly believe that a stock engine with a good intake and a tune might have as much as a 20 hp gain. Maybe more with an exhaust.

Interesting, thanks.

And yeah, here was that other thread I had in mind, where Blaine was suggesting that the computer would adapt. Maybe you replied similarly there, so sorry if I missed it, but that thread got long.
 
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Actually, I like the idea. Or if he's not one to join a forum and type out his thoughts, I wonder if you could look at this with him and then type up what you two take to be your response to the comments there.

I for one would also be interested to know how/whether these answers differ for the 2.5 4-cyl.
I already had that telephone conversation with Jim back in 2001. I strongly remember what he said as it surprised me that the OEM air intake system was specifically designed to be 100% non-restrictive no matter what.
 
I already had that telephone conversation with Jim back in 2001. I strongly remember what he said as it surprised me that the OEM air intake system was specifically designed to be 100% non-restrictive no matter what.

Every engineer says their designs are perfect. It's an engineer thing.
 
I already had that telephone conversation with Jim back in 2001. I strongly remember what he said as it surprised me that the OEM air intake system was specifically designed to be 100% non-restrictive no matter what.

Either he was putting it in layman's terms for you or there was an asterisk that wasn't discussed, because from an engineering/physics standpoint, that doesn't exist. A literal interpretation of "100% non restrictive" would imply that the pressure at both ends of the tract are perfectly equal, and that's not a physical possibility.

And every one who disagrees with the engineers is an expert on the subject. Yeah, we've heard all that kind of bullshit before.

What's bullshit is the pretense that engineers work in black and white, where things like "100%" and "absolute" are meaningful in any way. What they did with the intake is make it big enough that further reducing restriction no longer made sense in a world where intakes can't cost $3000 and have to fit under a hood and cross an engine compartment.
 
And every one who disagrees with the engineers is a self-proclaimed expert on the subject. Yeah, we've heard all that bullshit before.

The only BS here is the folks citing opinions as facts without data to back it up.

Well besides "butt dynos" and "been theres"
 
P.S. There ARE many air intake systems that are indeed restrictive, replacing them with aftermarket air intakes can produce significant performance enhancements. For a couple examples, the Chevy Camaro Z-28 and the Mustang 5.0 HP. There's a good story behind the Z-28's restrictive air intake system. When the Z-28 was first being tested on the track before going into final production, it was faster on the dragstrip than the Corvette was. The Corvette division of GM had a FIT about that saying only the Corvette can be the fastest GM produced car. Corporate agreed and Chevrolet was forced to restrict the Z-28's air intake to reduce its performance so the Corvette would be officially faster.

Despite the opinions of the self-proclaimed experts, the TJ simply isn't one of the vehicles with a restrictive air intake system.
 
I already had that telephone conversation with Jim back in 2001. I strongly remember what he said as it surprised me that the OEM air intake system was specifically designed to be 100% non-restrictive no matter what.

Right, understood. I just meant that I found that post to be helpful. Was wondering if you or he would care to comment on each topic that it addressed. Especially interested in the 2.5 4-cyl of course.
 
I disagree. The tests were all very repeatable. On one of the previous tests I put the stock airbox back on after the cold air and the power dropped again. If you watch the video you can see that the numbers are super repeatable. Pull to pull within a horsepower or two. The dyno was also done on a warmed up engine and drivetrain. I had done probably 15 or 20 pulls before the video. I have been doing this professionally for over 20 years.

Also, if you pay attention to the scanner from pull to pull the ECT and IAT values are reasonably similar.

Run a type A analysis on each run parameter... 10 runs each parameter, keeping all the contributing factors within a margin for each parameter, and Ithink your repeatability will fail what you are attempting to preach.