younG_Gunner

iTrader: (2)

I've recently bought another 87 TII and was planning on doing out with the stock exhaust seeing as its been pitted through and seen better days.

Cat Back Exhaust System, 1987-91 TURBO II
Part Number: 16418
Retail Price: $635.00

Plus this:

Cat Replacement Pipe w/Presilencer, 87-91 TURBO
Part Number: 16207
Retail Price: $335.00

I was planning to change it out with this but I wasn't sure if I'd have to switch out for bigger injectors? Just trying to clarify whether or not I have too. The piping is only 2.5" and I dont plan on going up to 3" any time soon. Might throw on an S5 turbo but thats about it. Don't really have plans to boost crazy numbers with this one.

arghx

iTrader: (3)

so you are planning on going from a 100% stock exhaust to a catless 2.5" exhaust?

john ward

iTrader: (7)

I would be more concerned with boost creep first. Once that is under control then you can look into larger injectors and a way to control them.

misterstyx69

iTrader: (142)

before you do this,Look Up "Boost Creep" with the search Function.
and the Numbers look like Racing Beat part Numbers..am I right?

jjwalker

I didn't read enough....

excuse me.

younG_Gunner

iTrader: (2)

OH WOW!! After reading what I posted, I can't believe how much information I left out!

First off, yes, these are from Racing Beat. And as far as boost creep, the most that I can think of is porting the turbo wastegfate. Possibly an MBC/EBC?

I'm not necessarily saying I'm going to upgrade injectors, I'm merely asking that if I change out for the RB exhaust, will I HAVE to run something bigger or can I just keep the stock 550's and be relatively safe?

Any comments and suggestions are encouraged.

john ward

iTrader: (7)

Only wastegate will stop creep. A boost controller will not.

arghx

iTrader: (3)

you live in California. maybe you should get an exhaust system with a cat. That would help keep boost under control (you'd probably still need to port the wastegate) and help you with emissions.

Black Knight RX7 FC3S

iTrader: (7)

anything more then 8-9psi will require atleast bigger secondaries on the stock turbo.
If you are going to install a more freeflowing exhaust, porting the wastegate bigger to prevent boost creep will save you from a blown engine.

younG_Gunner

iTrader: (2)

What do you figure the boost will be pushed up to and what injector combo would you recommend for the secondaries. I have an extra set of 720cc's from a previous motor but would that be a bit excessive? I could probably get my hands on a set of 680cc's from an gsl-se if that would work out.

j9fd3s

iTrader: (3)

680 is basically the same as a 720....

first step actually is to upgrade the fuel pump, an FD pump works great, and can usually be had for free as the FD guys like to run larger pumps too. the next choice is a walbro.

the 2.5" RB stuff isn't that big of a power change from stock, but think of it this way. if you increase power by 10% shouldn't you increase fuel by 10% too? in real life its not quite a 1:1 ratio like that, seems like the 3" exhaust, which is more like a 20% gain needs 10% more fuel, there is some margin on the stock ecu.

plan B would be to run the RB DP, and catback, and just put a cat in there. that should be perfectly safe on stock fuel.

Black Knight RX7 FC3S

iTrader: (7)

From what people experience with boost creep on the stock turbo, it creeps up to atleast 12 psi on a free flowing exhaust.
When I had my stock turbo on with the wastegate not ported and set at 8psi, it boost creeped all the way to 15psi on 4th gear pulls between 3.5-5.5krpm. But I have already installed a walbro pump, and 4x 720cc injectors with a rtek 1.8 so I was safe from detonation from leaning out.
On my 4th gear pull when it boost creep to 15psi, my wideband was showing 12.1 afr which is pretty lean for that amount of boost, suffice to say, I took out the stock turbo and ported it, now it boost creeps, but barely 2 psi above set amount.