Overboost or boost creep?
 

Hey guys,

My turbos were blown and were making a whining noise when spooling up so got them replaced at rx7 heaven in auckland, new zealand which seem to be the only rotary "specialists" around here. (It was boosting 5 psi first turbo and 7-8 on second turbo. Now the thing is, on the aftermarket boost gauge 3rd gear it read 12 psi first turbo and second turbo 14 psi. I dont know whether this is a boost creep or an overboost issue as i seemed to find mixed answers from searching about it. My series 7 jdm rx7 has a front mount, no cat, rps muffler with 5" tip.

So the possible fixes i found was to add a cat however i dont want to do that yet single my car is running pretty rich (stock ecu) and a friend of mine driving behind me the other day recorded blue flames out of my exhaust when i let go of the throttle so idk if its safe to add cat.

Question 2) can i run 850cc's in primary as well as secondary using stock rails etc?

Another off this topic question, does a series 6 used power fc work straight on series 7? I was planning to get a safe tune with as much power as i could get with a boost controller and the above stated injectors.

Cheers

There are various things you can do
Like manual boost controllers .

Also the Series 6 PFC will not work with a series 7 motor / harness / car , its just best to save up and get a series 7 PFC . Ebay has them! LOL

You are most likely running past the limits of the factory boost control. An aftermarket boost controller can get rid of those spikes and get your boost more reasonable.

Read up, this has been covered in depth.

Dale

Alright thank you! I will go ahead with the boost controller to keep it stable.
Anyone know about the question 2? Running the standard 850's all around on factory side feed rail. I want to do this just before i go get my pfc installed and tuned.

alot of people say that the car does not idle well with the 800's also you need to modify thigns to fit the 800's into the primary slot ,

a more common and better mod is , getting the 800 secondaries bored to 1300CC , and running stock 550 primary , with 1300 CC bored out secondaries .

that way you don't lose your idle smoothness and , you get an extra 500 CC per rotor , VS having to modify , and only gain 250 CC's per rotor .

yes, you can run 850's all around - you will need to mill down the primary injector housing so that the 850 injectors sit lower. I forgot the exact measurements, do a search for 850 injectors in primary.

You have to modify the primary rail to accept the 850cc secondary injectors.

PFC will have to be tuned for 850cc x4 injectors. I don't know if it will even run let alone drive with the stock ecu and 850cc primaries- that is a lot more fuel.

You should be able to find a 4x 850cc injector base map for the Power FC. If you don't have a way to get it into your Power FC you can send the Power FC and the base map to your tuner and they can put it on and send the Power FC back where you can install it and drive to get the car tuned.

You could however install larger 2ndary injectors and keep the stock 550cc primaries. Then you could use the Power FC with the base map in it and limp (safely) it to the tuner to be tuned. You would just have to drive it under the secondary switchover boost or it will bog/backfire/shoot flames from being rich.

Power FC will also be able to be tuned to resolve your boost issues.

BTW, is your stock ECU completely stock or does it have a sticker on it from being ROM tuned?

Does the car cut out under boost at all or have you been letting off when it boosts up to 14psi?

We didn't get S7 RX-7 here and I am trying to learn how the S7 ECUs behave (is the fuel cut at 10.5psi like S6 or 12psi or or?).

here you go - https://www.rx7club.com/3rd-generati...primary-82244/

I've been reading up on a few more boost spike vs creep threads and what i have seems to be a boost spike coz my boost increases from 12-14 at 5000 rpm which can be enough to detonate the engine? So would you (anyone else) say if i was to drive to the workshop and back, and i didnt boost at all, i'm not risking detonation of my engine?

Also, according to the answers on the threads, a boost controller is not going to control the boost spike? Porting the wastegate would. So if that's the case, would i need to buy an external wastegate or can i get the internal ported as well? And would that be enough to stop the boost spike?

As long as you are still on stock ECU you are pretty safe. It will cut fuel if it overboosts above what it considers safe (varies by rpm) and has knock control.

Except!!! You are running FMIC, no cats and cat back, so you are probably pretty lean on the top end from the VE improvement- don't drive it hard unless you have verified it is still rich.

I am running a downpipe (US spec had precat), highflow cat, catback and small SMIC on stock S6 ECU and it is right on the edge being too lean.

And fix your boost issues.

A boost controller (or two) will fix the primary turbo overboost (anything below 4,500rpm) and the spike at transition, but will not fix boost creep (boost keeps increasing after 5,000rpm).

But, as I said if you are going to install a PFC you will not need the boost controllers as you (or someone) will tune the precontrol and wastegate duty cycles on the PFC.

Once you have the PFC on you won't have knock control, so play it safe with boost and AFRs- no more driving it when it is operating out of desired parameters, no more stock car reliability/idiot proof-ness.

However, you will have the potential to make more power.

S6 PFC does not work on S7 or S8, they have different plugs/pin-outs.