supraturbo1987

iTrader: (4)

First off, I have searched and am currently referrencing the following link:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/how-test-your-solenoids-actuators-other-turbo-stuff-802060/

However, I wanted to put my situation out there in hopes that someone may be able to point me in a specific direction more quickly than starting to troubleshoot all aspects of the system.

The car is bone stock, everything (including all exhaust components) are original. The car drives out well, and I have no other known issues other than the boost issue I will cover here. A/C is cold, idle is smooth etc.

I just installed a new fuel filter and connected a boost gauge because I felt the car had strong initial boost, but didn't notice a transition to the second turbo. Here is what I observed (car at normal operating temp, ambient temp about 40F):

-Idle vacuum is 16-17mmHg

-When going down a hill in 2nd and no gas, vacuum is 22-23mmHg

-after just cruising in 2nd, 3rd or 4th gear and punching it, boost goes to 12-13psi, then begins to drop off...there is no transition at 4500 that brings the boost back up.

-After boosting at 12-13, then changing gear and immediatly punching it again, boost will only go to 3-4psi and stay there till redline.

-When I let off and cruise for just a little bit, then punch it again, its back up to 12-13psi again and it repeats the cycle. Clearly, I don't have anything remotely close to a 10-8-10 pattern.

Again, I will continue to search and do my do diligence, but want to see if there was someone who experienced this exact issue that could point me in the right direction sooner than later.

I do have a Downpipe waiting to go on, but figured I needed to get this boost pattern down before installed it. Is that necessary to wait, or considering everything else is stock, I should be fine in case that pre-cat is a problem? Thank you!

Trev

arghx

iTrader: (3)

[QUOTE=supraturbo1987;10979515]
-after just cruising in 2nd, 3rd or 4th gear and punching it, boost goes to 12-13psi, then begins to drop off...there is no transition at 4500 that brings the boost back up.
[QUOTE]

This is very close to the boost pattern described in Tashima et. al, "Sequential Twin Turbocharged Rotary Engine of the Latest Rx-7" 1994 :



80kpa = 11.6psi, which is within tolerance of what you are seeing considering that it is cold outside. Notice that there is no boost dip in that cart. You're not the only guy to report 12psi peak boost on a completely stock car.

This could be a bad check valve.

I don't agree that 10-8-10 is the only proper boost pattern. But I'm not saying that 10-8-10 is "bad" either. We don't know exactly how the sequential system was designed and we don't know the exact specifications on a proper boost pattern (acceptable boost pressure tolerance). That information is probably buried in some archive in Hiroshima now. We do know that there is gear and throttle-based logic in the control system:

DaleClark

iTrader: (55)

Yeah, check valves are the place to start, your new Viton check valves will be heading your way tomorrow.

Basically the primary is working, the secondary isn't. Gotta get the turbo control actuator to do it's job then go from there.

Is the car BONE bone stock, or does it have a downpipe?

Also, how fresh are the plugs? Very worn plugs can actually give you MORE boost but less power.

Dale

JTurtonRX_7

TL;DR just go non sequential. Its awesome not wondering what your car is going to do when you put your foot down.

supraturbo1987

iTrader: (4)

Thanks dale for the check valves!

It is BONE stock. I have a DP in the garage, but is NOT installed. Catback is still original even.

The plugs only have about 400 miles on them...

Trev

DaleClark

iTrader: (55)

I've had my car since '04 and it's been sequential the whole time. Put new check valves in, made sure the vacuum lines were done right, perfect boost pattern. Had a lazy transition at one point, replaced the turbo control solenoid, fixed. That's it.

The low-end response from the sequential setup is SO good around town. I'd rather have a fat, meaty powerband than a peaky powerband.

Most of the problems with the sequential system are easy - boost leak, bad check valves, bad vacuum line hookup. Going non-sequential "because it's hard" is just lazy.

Dale

supraturbo1987

iTrader: (4)

Agreed. The car is exceptional except for this issue,and being stock I have he advantage of fixing it without having to rifle through someone else's hack job.

I did follow directions from a post of Dale's from a while ago and went to Kinko's and blew up the diagram to 11x17!



Trev

DaleClark

iTrader: (55)

Good man!

BTW, USPS says your check valves will be there Friday or Saturday .

Dale

supraturbo1987

iTrader: (4)

Excellent!! Thanks for all the help Dale, you are a great asset to the forum!

Trev

supraturbo1987

iTrader: (4)

please close thread, I have a new thread to track my progress

https://www.rx7club.com/showthread.p...8#post10986108