Datsun Roadster Forum-311s.org

Well, actually this is an appeal to the wealth of expertise that is often found here from our diverse population... ya never know who might be an expert in what...
As some here know, I've converted to EFI. One thing has become apparent, and that is that the fuel pump is louder than I like. It's mounted inside a 10x10x10 square aluminum fuel tank/cube which is then bolted to the underside of the car on the passenger side under the package shelf, as low as it can go. It's kinda rubber mounted but not in a serious manner yet, and that may help in itself. Anyway, the sound I'm looking to kill is a mid frequency hum or whine that the pump makes. I understand this to be typical of EFI pumps, and often a reason why they are put in the tank itself but that's not an option at this time. I'm considering various wraps but have no experience with them, and I do know that sound deadening is a science and some materials work better than others at controlling different frequencies or types of sound. If someone here has some experience or actual expertise please chime in! Since it will require removing the tank and everything connected to it, I'd like to make my best educated guess at what might work most effectively... thanks as always!

No expert here. Could insulate the mounting fasteners of the header tank. Cover exterior with dynamat/etc. Do you think it is transmitting through the fuel lines? Are they hard pipe or flexible hose?

That's why most tanks have become plastic
VWs fuel pumps were so loud in the 80s earlya 140 psi CIS , later pumps were noisy after a year they ended up going to a wierd design plastic and putting top sound systems / radios in all models even the low grade ones 10 speakers . Also they went to a pre pump for the fuel pump . I've seen some have a plastic bagged styrofoam pad rapped around the pump Kia Genesis
Gm"s pumps are very soft sound
The pump isn't connected to the metal assy frame right ?
My z31 T has a big pump that's quiet

I ran into a similar issue when I converted my '66 to a KA24DE. The external pump was just crazy loud. It was mounted on the underside of the read parcel tray.

I know it isn't in the cards, but the investment of moving to an in-tank pump was worth the effort. In the 15 years since I swapped the engine, I've used a few internal pumps. Originally used a used Maxima Pump, then later a Generic Inexpensive pump. Now a Walbro pump.

Greg, you need to lower the resonant frequency of the tank, using dynamat, or equivalent. The thicker(more dampening) the better. I've also used isolation mounts to decouple walls in nedia rooms. There all kinds of frequency specific solutions. I have most of them left over from past work. Let's meet somewhere, and I'll measure your noise with my frequency analyser. Give me a call Pat

Wow, thanks all. As usual, you're an invaluable source of information. I'm a strong believer in the old "7 degrees of separation" theory where if you know 7 people you can reach out to just about anyone in the world given enough time.
Pat, you were one of the first people I thought about, so thank you. The car is running well enough to meet up when the rain has stopped, so I look forward to getting together. The sound meter is a great idea and will give us some nice objective data to compare before and after.

To those interested, I used nylon line for my fuel lines instead of steel braided as they were easier to work with and tend to not transfer sound per the Internet. The volume of the sound can vary a lot, and apparently this has to do with demand, heat, and fuel aeration. I also gather there are sound differences between all pumps, and that the same pump design can be quiet or noisy depending on several factors, as well as the quality of the manufacturer. In the case of the Bosch 044 style pumps, they can range from $45-$250, with a "real" Bosch running about $150 or more. And there are knock offs to contend with that come shipped in a Bosch box but are not real. On top of that, people with confirmed real 044s still run into sound issues. Mine is an Oasis brand 044 that was well reviewed and I don't think is particularly loud as 044s go, but the car sounds like a race car at times.

Hi Greg,
Applying my industrial vibration knowledge here a bit....totally not an actual practical answer;
This isn't a resonant frequency/excitation issue where you would need to tune the mass but more of a isolation issue where you want to completely isolate the natural vibration of the pump from the rest of the car. In otherwords, the motor's gonna vibrate regardless of the amount of mass so isolation is the thing to focus on. Try to eliminate any metal/metal touch points. Even if you have thick rubber gaskets, you still have the metal bolts mounting to the frame. You could try mounting the box with rubber grommets like these:
https://www.mcmaster.com/rubber-mounts/ ... rommets-6/
In the end, it might just be the sound that the pump makes, even with eliminating any amplification from the structure. That would require focusing on insulating the the sound from the pump itself with actual insulation of some sort...or a combo of both.

That's probably no help at all...lol

I appreciate the Input! Pat and I are going to meet up and do some before and after as he has that cool meter... it even reads the frequency so we can try to target it. This is a problem that many deal with so if we're successful it may be a Youtube video.

What type of pump is it? The Bosch pump that I have on my BMW is known to be noisy, and its noisy. Its more noisy when the in tank lifter pump isn't happy (they tend to fall apart, thanks VDO.) It might simply be that your pump is a loud design like the Bosch one I run.

Will

SLOroadster wrote: Mon Jan 18, 2021 3:21 pm What type of pump is it? The Bosch pump that I have on my BMW is known to be noisy, and its noisy. Its more noisy when the in tank lifter pump isn't happy (they tend to fall apart, thanks VDO.) It might simply be that your pump is a loud design like the Bosch one I run.

Will

It's not a real Bosch 044 but is the same design (Oasis brand). So far from what I've been able to listen to on the Internet, it's typical. It does vary based on load and it gets pretty quiet under demand, then louder when I let off the gas. That's why I have not opted to buy a confirmed, real Bosch pump because I don't think it will be significantly more quiet. Longevity will be a potential issue down the road, and as the pumps wear they tend to get louder it seems, so a Bosch pump may be in the future if this one fails. So far it works great and maintains pressure no problem. My lift pump is a 42s and it's almost as loud, so I may try to quiet it up some too. I wouldn't be able to hear it over the exhaust as I can the 044.

With Pat's help, I've been looking at soft 40-50 durometer isolation mounts that can hold the weight. We'll get together soon to measure the sound so we can do a before and after. It's on the back burner though as I just broke off an O2 sensor in the exhaust manifold of my Mazda 3 and now must replace the whole manifold and cat unless I decide to try and drill the thing out... not likely considering the cat has 110,000 miles anyway...

I have a real Bosch 044, and its loud. Nothing you can do about it. My 044 is mounted in the stock mount, rubber feet between the mount and the body as well as a rubber retaining ring around the pump. Its all soft rubber, the pump is just loud.

Will

SLOroadster wrote: Tue Jan 19, 2021 2:37 pm I have a real Bosch 044, and its loud. Nothing you can do about it. My 044 is mounted in the stock mount, rubber feet between the mount and the body as well as a rubber retaining ring around the pump. Its all soft rubber, the pump is just loud.

Will

Ya, I'm hopeful that with mine being in a surge tank we'll be able to keep the sound contained inside better.

Gregs672000 wrote: Tue Jan 19, 2021 9:27 pm

SLOroadster wrote: Tue Jan 19, 2021 2:37 pm I have a real Bosch 044, and its loud. Nothing you can do about it. My 044 is mounted in the stock mount, rubber feet between the mount and the body as well as a rubber retaining ring around the pump. Its all soft rubber, the pump is just loud.

Will

Ya, I'm hopeful that with mine being in a surge tank we'll be able to keep the sound contained inside better.

A 044 is not a submersible pump. Putting it in a surge tank seems like a bad idea. Outside the tank, sure, inside, seems like a bad idea.

Will

SLOroadster wrote: Thu Jan 21, 2021 3:17 pm

Gregs672000 wrote: Tue Jan 19, 2021 9:27 pm

SLOroadster wrote: Tue Jan 19, 2021 2:37 pm I have a real Bosch 044, and its loud. Nothing you can do about it. My 044 is mounted in the stock mount, rubber feet between the mount and the body as well as a rubber retaining ring around the pump. Its all soft rubber, the pump is just loud.

Will

Ya, I'm hopeful that with mine being in a surge tank we'll be able to keep the sound contained inside better.

A 044 is not a submersible pump. Putting it in a surge tank seems like a bad idea. Outside the tank, sure, inside, seems like a bad idea.

Will

Actually, this surge tank is designed for the 044. It uses an O-ring and a metal surround to secure the pump in the tank, while the wiring bits sit outside the tank. See the pics under my Jenvey EFI post if desired. It has a nice snap on filter too, so it can be used external or internal depending on the tank design.