2 400c vs 1 air zenith

hey guys i was wondering what would be a better choice to fill a 5 gal
2 400c or 1 air zenith filled to 150 psi
i also just bought a adjustable pressure switch so i think it might be good to get the air z and adjust the pressure switch to cut off at maybe 160 that way its a little louder then 150 without totally sacrificing souding like a Train ?
send me some input oh but the main reason i asked the question before i got side tracked was this…
which will fill a 5 gal tank faster 2 400c or 1 air zenith also @ 150 psi ?

data for duel 400s
fill rates for duel 400s

air zenith
Voltage: 12v DC
■ Working Pressure: 200 PSI
■ Air Flow: 3.8 CFM @ 0 PSI
■ Duty Cycle: 100% @ 200 PSI
■ Max. Amp Draw: 35 Amps
■ Motor: 3/4 HP

so at 0psi the duel 400s will fill faster and will probably fill your tank faster, however they will only kick out to 150psi, the Air zenith i was comparing it to went to 200psi.

can anyone tell me which will be a faster fill from 110 to 150 1 400 c or 1 air zenith ob
does anyone have a fill rate from 110 to 150 for a 5 gal tank with the AZ?

Look up an OB2 in Hornblasters’ store on Ebay.
They have charts in there.
By the charts it’s 1:20 from 110-150psi.

Here’s a link to the Hornblasters ebay sale.

Air Zenith OB2 Tank Fill Rates
5 Gallon Tank
Begin/End PSi Fill Time
0 To 200 PSI 6 Minutes
165 To 200 PSI 1 Min. 25 Sec.

5 Gallon Tank
Begin/End PSI Fill Time
0 To 145 PSI 3 Min. 50 Sec.
0 To 175 PSI 4 Min. 57 Sec.
0 To 200 PSI 6 Minutes
110 To 145 PSI 1 Min. 10 Sec.
145 To 175 PSI 1 Min. 5 Sec.
165 To 200 PSI 1 Min. 25 Sec.

Air Zenith OB2 Performance Data
5 Gallon Fill Performance
PSI Amp Fill Time
0 0 0 Seconds
10 25.5 9 Seconds
20 27.1 23 Seconds
30 28.5 34 Seconds
40 29.8 48 Seconds
50 30.9 1 Min. 4 Sec.
60 31.9 1 Min. 19 Sec.
70 32.6 1 Min. 35 Sec.
80 33.2 1 Min. 50 Sec.
90 33.7 2 Min. 7 Sec.
100 34.3 2 Min. 25 Sec.
110 34.6 2 Min. 42 Sec.
120 34.8 3 Min. 3 Sec.
130 35.1 3 Min. 21 Sec.
140 35.2 3 Min. 42 Sec.
150 35.4 4 Min. 2 Sec.
160 35.5 4 Min. 24 Sec.
170 35.5 4 Min. 46 Sec.
180 35.5 5 Min. 9 Sec.
190 35.4 5 Min. 35 Sec.
200 35.2 6 Min. 0 Sec.
*Supply Voltage: 13.9 Volts

Sorry to wake the dead thread, but this is highly relevant. I too am debating whether to (eventually) go to a dual Viair 400c setup, or a single OB2.

One thing I have noticed is that spec sheets are deceptive. Some fill charts for the OB2 shows 3.8CFM at free flow, others show 4.25cfm at free flow, and higher cfm values down the line as well.
@ear2ear, take a look at the attached fill chart, it is on Air Zenith’s website, under support I think.

By going with the chart on Air Zenith’s web site (or attached to my post), compare the chart against the speed of the Viair 400c, (google “viair 400c” and click the 1st link).

If you compare the CFM ratings versus pressure, specifically from 100PSI onwards to 150psi, the OB2 is roughly equal to TWO Viair 400C compressors, and in fact overtakes the TWO 400C compressors from 120PSI onwards. Note that this is not the case with fill charts that show 3.8cfm at free flow on the OB2.

However, if you look at the fill times, not the CFM values, these numbers sometimes highly favor the two 400C compressors, showing that the OB2 isn’t that much faster than a single 400C from 85-105PSI but it is as fast as 2 Viair 400C compressors from 110-145PSI.

So compare the 90 to 110PSI time value on the OB2, which is 31 seconds, versus the 85-105PSI value of a single 400c, 35 seconds. Not much difference. This does not correlate with the CFM value comparisons, the OB2 should be getting a better value here. Tweaking to 80-100PSI on the OB2 chart results in 30 seconds, still not that much better.

Then compare the 110psi to 140psi time value on the OB2, which is 53 seconds, versus the 110-145psi value of a single 400c, which is 100 seconds.¬¬ So this does seem to correspond well with the CFM value comparisons.
I don’t know which values to believe. It seems like the tank fill charts are approximate for the 400C, for example the 2.5 gallon values are not half the time as the 5 gallon value. They are rounded or something. They are all pretty close, but this one irks me. 0 to 145PSI on 2.5 gallons is 140 seconds, but on a 5 gallon tank it’s 290 seconds, 10 seconds more.

So why are some charts for the OB2 showing 3.8cfm at free flow, and others, 4.25cfm?
Is the OB2 equal to 2 Viair 400C compressors from 100PSI onwards?

Yeah, you have manufacturer’s charts and retailer’s charts. Who even knows if they’re calculated or real tests. What was the ambient temp for each? For the OB2, I tend to believe the Hornblasters numbers on their ebay page (chart listed above). The times are longer than the AZ listed times.

I did a test about a month ago before I tore down my setup. Made a video of the pressure gauge with a kitchen timer sitting next to it. 0-200 psi. My voltage is 14.7 which is higher than their test. And the AZ tanks are a little less than 5 gallons. Will have to check, but I think it took 5:36. So I think the 6 minutes in the HB chart is right on.

When I decided on the OB2 I was comparing to the 480C since they’re both 200psi. Without both of them in front of me, there was nothing else to believe but the charts…

Don’t I have both retailer’s charts? Viaircorp and Air Zenith->attached to above post.

Yeah it’s a mystery, where your OB2 chart came from and why it was updated and if yours is the truth or not.

Viair & AZ are manufacturers. The retailer’s chart I was referring to is Hornblasters’ chart…which seems to jive with my test.

I don’t have experience with the Viairs though.

I have dual 400c’s and they fill pretty quick… i’m more than happy with them, but I’m going to switch to an EDC soon enough…

DJD audio apparently found some values for the OB2, don’t know yet if he created the data himself or not. I also don’t know if there have been hardware revisions of the OB2 or it has been the same product since it came out.

Once again the time values when comparing it to Viair’s time tables for the 400c, the OB2 barely keeps up with ONE 400c from 80psi to 150psi. You have to approximate the times because of the 85-105psi time and 110-145psi time.
But, if you look at the CFM values of the OB2 vs 400c, the OB2 has at least half again or more cfm between 80-150psi than a single 400c, and in fact has more than double from 140psi on…

I’m beginning to think Viair’s time charts are wrong but their cfm values are right…and I’m assuming djd’s findings are accurate but I’m trying to contact him to see.

Ok I checked the video from my test. It’s (2) OB2s filling (2) AZ 5 gallon tanks to 200psi. As I mentioned, they are not a full 5 gallons. IIRC they’re around 4.25 gallons by the math. I literally recorded the whole fill from 0 to about 203 psi and it took 5 minutes 39 seconds @ 14.7 volts.

5:39 = 5.65 minutes
5.65 minutes / 4.25 gallons = 1.33 minutes per gallon
1.33 * 5 gallons = 6.65 minutes = 6:39

And that’s with a bit of over-volting to 14.7V. I’ll assume you tested the latest version of the OB2 compressor (if there are multiple design revisions).
Thanks for the info. It looks like 2 400C compressors is the easiest route because I already know the performance of them and there isn’t any mystery with them (and it isn’t a slouch).

I’ll update if I ever get anymore relevant info.

Turns out that the chart I put up from DJDaudio on post#10 was a prototype OB2 unit of some sort, so invalid for their modern stuff.

See post#28 and later for conversation with DJDaudio, here (mods remove the link if your not happy)

A response from Air zenith. The 1st chart refers to the chart showing 3.8cfm at 10psi (or free flow), and the 2nd chart refers to their current one, showing 4.25cfm at 10psi (or free flow).

the email;
“1st chart was released by or before 2008 SEMA Show, we improved internal parts design (reed valve, stroke, etc) starting on the 2nd batch OB2’s.”

Yes, that was it, after emailing them back and forth many times, asking them to spill the beans.
So it looks there are two types of OB2 compressors.

Odd that I can’t find any information anywhere regarding their OB1 compressor, unless their OB1 was their current product up until 2008 and that’s what chart#1 is for. Who knows.
The #1 thing I get out of this mystery is that Viair customer support via email is MUCH better than Air Zenith. The Viair rep typed about a page for me each time I emailed him, … and he has K5 train horns.

Im replacing my Zenith OB2 compressor for the second time, not a very well built compressor and it was only used about 15 times for 10 - 15 mins each time to fill up my 8 gal tank set with a 150 psi shut off. I would go with twin Viar’s. Had a single Viair 380C running my 5 gallon tank with also a 150 psi shut off on my other truck never had a problem and it was around the same time to fill up as the Zenith does on the 8 gal. Had my Viair for 5 yrs and the Zenith didnt even last 5 months.

Welcome to the forum. I’ve heard the same thing about Air Zenith compressors. They’re a cheap copy of Viair and that company got its start from Viair. This is word of mouth and I have no experience with them.

I think I’m gonna go with twin Viair 495C’s and a 12 gal tank to run my 2 sets of hornblaster kits one 1/2 inch line and the other 1/4 inch line one facing foward and one facing back both angled doward with horn covers on them.

Welcome to the forum.

The 12 gallon tank should be fine but be aware of Viair’s 5 gallon per compressor warranty.

Why not use 1/2" line for all of the horns?

Two different size lines two different tones 1/2 inch will be a lower tone and the 1/4 will be a higher tone. A single 495C says 8 gallons so I figured go to a 12 gal tank if I get twin 495’s. I was even thinking giving Zenith one last shot and go twin Zenith OB2’s.

At this time, 495’s are not available… Viair pulled them from the market i believe to durability issues when they ran so fast and hard that they fell apart internally…