Hey there, well the local rx7 guy is working on my car right now doing the S5 intake swap. Now the only problem so far is that he can't figure out what to do about the fuel pressure drop between the s4 and s5 fuel rails. From his little manual these are the numbers he's getting:

87 vacuum hose detached (cold start) 35.6-37 psi.
vacuum hose attached 28.4 psi

89 vacuum hose detached 27.33 psi
vacuum hose attached 21 psi.

so you can see there is a diff in the pressure from the two fuel rails. I looked up on the carl davis page and he mentions nothing about this pressure drop. We were thinking maybe a better pump (perhaps TII or S5) But we need the hard numbers before we swap that out as well. If anyone knows of how to correct this problem w/o having to purchase a fuel comp, that would be great.

or if anyone has corrected this problem somehow making a mixed fuel rail that would be great.

thanks

 

hmm..never had any problems with my swap-i used s4 primary and s5 secondary fuel rail w/o ill effects.never heard anyone else with problems.
~d

 

right, no one else has had problems, but from his book a 7 psi drop in fuel pressure is a lot, and he's concerned with that cause if I run low, that could be bad. He was thinking just keeping the vaccuum line unplugged, but then kinda talked to himself why that wasn't a good idea. AND before anyone mentions a fuel pressure regulator, he's not dumb! but he's looking for a better way to do it!

 

Anyone got any suggestions???

 

Glad to see the s5 Intake has worked for you. That page belongs to wozzoom. He Is your best bet to accomadate your concern. It would be best to email him, seeing how he's not on he forum all that much.

 

Hi Ryosuke,

I just checked both the online manuals, and I think your technician is mistaken.
On the specifications pages, the regulated fuel pressures are:
86-88 35.6 - 37 psi
89-91 34.1 - 39.8 psi
nearly identical.

In the pressure regulator inspection and testing procedures, at idle with the vac. hose connected:
86-88 28.4 psi
89-91 27-33 psi
again, nearly identical.

So, I don't think you have anything to worry about. I think he's misread the some of the tests & numbers. Good luck with the swap, I too am about to do it, soon as the weather warms up and I get the E-test done. Are you in S Ontario? Maybe we could get together and compare notes once we're both finished.

regards,

 

Hey thanks for the info, I'll print this out and give it to him. BTW where did you find this, I want to show him the source as well.

I actually live in Winnipeg, but I bought all the stuff from silverrotor, it was all in wicked condition and now that this is solved I hope it'll be done by tonight.

thanks

 

Hey Ryosuke,

The service manuals can be found at fc3s.org in the 'how-to's section, they're in adobe acrobat format.
You can also find the full parts catalog at mazdaformance.com

Kan-pie!

Curtis