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[HiProfile]

So I got another project checked off today, something I've wanted to do for a while. I made a simple Honda FPR pressure checker since I've got more curious about the different FPR's out there for Hondas.

It's a few fittings to hook to an air compressor, a valve, a pressure gauge (FPR side of the valve), and a plate to bolt the FPR to. I set the compressor's regulator to 55 psi then slowly crack the valve til the needle hits the bypass pressure & stops. It seems simple, and for the most part it is. I'll post pictures tomorrow or monday.

Everyone thinks they're all 3 BAR (43.5 psi), I know I used to, but they're not. I know GSR and ITR use a 3.5 BAR (51 psi) FPR, and I think some H-series do as well. My H23A's FPR turned out to be 3.5 BAR. I tested an old F22A reg (the larger outlet style) and it maxed at 30 psi; FYI JD's info was true that they flow a lot more before they can't control the pressure. Most D/B FPR's tested at 43.5 psi as did an identical looking CBR 954, but some maxed out at 38 psi (2.5 BAR). 0.5 BAR less pressure works out to ~7% less fuel, or nearly a point of compression. In a stock car the O2 will correct for it, but this can cause big issues with large injectors. The ECU will undershoot with it's corrections, especially during low duty cycles. Unless you test your latency values, the ecu's corrections during low duty cycles can be far enough off to cause AFR instability. I'm glad I did some of these tests. I've had a few customers over the last 2 years that had to dink with latencies more than normal.



Another thing this let me do is mod & test a stock FPR for more pressure. I took an F23 FPR which tested 43.5psi and put it gently in the vice. I put an air compressor fitting over/around the vac nipple and gave it a few wacks. I think I drove it down about 1/8", and it tested at 58 psi (4 BAR) right off the bat. This is essentially what a B&M FPR kit does to a stock FPR. The D/B/H style with the elbow in the vac nipple won't be as easy, but will work just as well. That extra 33% pressure will add ~15% more fuel. It will also work with a Walbro 255HP pump without raising fuel pressure at idle, since base pressure will already be at that higher pressure some get forced to.

[ratcityrex]

I've wondered about certain stock fpr's for a while now. Glad to see these tests.

[92CXyD]

I recently experience using stock OBD0 Inj. and what I thought was OBD0 D16 FRP which works out to 240cc inj w/ 43.5 psi base.

But the inj. were running like they were 340cc on my son's '89 Integra w/ 3stage vtec.

Swapped out injectors for another set 3ohm inj. and still get the same thing.

I look closer to the FPR it looks like on of h/f series ones with a little wider and bent outlet.

[sewell94]

Honda using different fpr has been known for years.    That was an old trick before we could chip the ecu was to put the lower pressure regulators on to lean them out.    There was a post on the old hybrid boards on how identify  which one  was what and what pressure  was.  The fsm for the corresponding model will also tell you what the fpr should be.

Its been awhile but from some old notes
ITR and Gsr are the highest pressure @ 51lbs,
b16/b18a/b and obd1 d are 40-47lbs,
obd2 d  38-46 psi
H23/F22 36-43psi
H22 - 33-40 psi

[Minor Threat]

So, H22 injectors are run at a lower base pressure, has anyone ever had a set flow tested?

[HiProfile]

I've never read anything about this in over a decade working with Honda's, and I'd like to think I know more than the average bear. Guess there's always something to learn. From what I can see they're mostly the same, the outlets are the only possible difference. Even then some bent ends are the same pressure as some straight ends, and some of the same shape have different pressures.

The Prelude injectors are still 330cc/290cc at 43.5psi depending on the year, the data resulting from the different fuel pressure is likely built into the ecu.