94RXse7en

I have always had transition problems with my 94 RX-7 - I know a lot of you have - however mine may be a little different and so I am asking for help. I am located in Utah where the elevation is 4,300ft - So I know I have that working against me - My boost pattern is as follows - 14 psi (manifold) and then at about 3,200/3,500 my boost slowly drops to about 11 psi (manifold) and then at 4,500 my boost drops to 6 psi (manifold) and then quickly back up to 14 psi (manifold). In first and second gear it is a little annoying but the higher the gear the more annoying it becomes. What should i look for that would cause that drop to 11 psi and the dip all the way to 6 psi? Thanks!

LAracer

Well, you might find some useful info on this thread:

https://www.rx7club.com/showthread.p...light=altitude

Or you might find something here that will help you:

http://www.autosportracetech.com/RX-7/rx7stuff.htm

Or you might just do what I did and blame it on the altitude. I alleviated the problem by putting home depot boost controllers on the wastegate and precontrol, and I managed to dial in a boost pattern that was acceptable. I still get that slow dip before transition though. I recently switched to a Profec-B, and I did notice a little better response, but nothing that great.

Good luck.

94RXse7en

Thx LAracer - So you are running 10-7-10 @ 7,000 ft in NM - Is that absolute or manifold your talking about. If that is your gauge that is low boost. I saw that you were trying to figure out the differences between the boost gauge reading and the reading on your power FC - did you ever get an answer?

LAracer

Hehe, yeah technically that's low. Without any boost control the primary was hitting 14psig at the manifold. I used the boost control to turn it down to 10. I know I should be safe at 14, so 10 must be even safer (paranoid). The car is still fast (13.7 1/4 using G-tech), so I'm not too worried. Now that I have the profec, I set low boost at 10 and hi at 12.

I don't have a power FC, but I think I got enough concurrence that 14psig@7000ft = 10psig@sea-level for me to feel safe turning the boost up to 12. I'm almost positive that the pressure sensor reads absolute pressure, which, for 10psig@sea-level = 28psia = 14psig@7000ft. No one has corrected me on this so far.

My advice to you would be to check all the troubleshooting stuff on that second link I gave you - check all the hoses, solenoids, actuators, check-valves, etc (buy a vacuum pump if you don't already have one - $20 at autozone). If everything checks out fine then try some inexpensive boost control (the "home depot" boost controller), and try carefully tuning the valves to improve your transition (or to lower the boost if you're paranoid like me). If that works, then maybe invest the $300 in an electronic boost controller just for the convenience.

But most importantly of all, let us know how it goes and if you find a problem with any of the solenoids etc. You may just find something I have overlooked

Have fun

94RXse7en

yes, 10psi on your gauge is low but your right it is safe - If you were seeing 14psi on your gauge that is manifold pressure. And you ECU was registering about 10psi absolute but without a Power FC you cannot read absolute pressure. Years ago after instaling my boost gauge I got the worried when i saw the boost jump to 14psi, after reading that an RX-7 boost pattern should be 10-8-10 - needless to say i did alot of research and came to realize that are ECU compinsates for the lack of oxygen by upping the boost to reach 10psi (absolute) - the side effect is more heat which becomes our loss of power at high altitudes vs a loss of oxygen.

I do have a bleeder valve in place of the pill on the precontrol valve but I could not tune out the drop before transition.. like yourself - thanks - i will keep trying

Fred Sickert

There is a calculator here :

http://not2fast.wryday.com/turbo/boost_converter.shtml