Hi (Not entirely sure that this is the correct area to post), I have a 92, 305 rs camaro. In the future I do plan to do the 350 swap, but for now I don't need the extra power. I want to swap in a Hooker Super Competition cat back, a hi flo cat, and hooker competition shorty headers (Side Note I did not see super competition shorty headers, will the non-super competition shorty headers fit the cat back?) I was also interested in doing a new intake manifold as well but I'm unsure on the compatibility with the 350 swap later on. My main question is will I need a new chip/need to make chip modifications after the cat back, headers, catalytic converter, and possibly intake? I read around on exhausts as well and it seems most people here recommend going with 3in, but I don't understand what part is supposed to be 3 inches. The hooker super competitions read as 3in intermediate pipe, 3in tip outlet, and 2.5in tailpipe diameter. From my understanding there are systems to replace the chip with an easier system to tune, but I don't know much about it, and I don't see a need for it until I plan on actually putting more power in the car.

Any and all information is appreciated. On a side note although I still don't know much about my car, I'd like to thank the whole forum for getting me more interested in my car ( and cars in general).

 

My suspicion is you won't need to re-calibrate the chip for just exhaust mods. Exhaust system alone is probably something even a MAP car ECM can probably handle, especially if the intake manifold remains a restriction to better flow. Also, the stock cam may not even take advantage of the better flowing exhaust.

But worst case, if you were to watch the fuel trims in non-Power-Enrichment mode (where it's still in closed loop), you might see an indication of the ECM having to add a little bit of fuel due to better scavenging at moderate loads and into the mid-range and above part of the RPM band. Also, in power enrichment (which is essentially open loop), I think GM builds in enough margin on the fuel mixture that you wouldn't be in danger of going lean.

As far as the intake, it depends on the kind of intake I guess.

 

Thanks for the info. So don't change the intake, because too much airflow isn't going to help me as I can't use it to make power, and if anything unrestricting the airflow might mess with the chips stock parameters (too much air) ? I hope I'm thinking about this correctly, regardless thanks so much for the info! I also am doing the exhaust for the sound, not necessarily for the increased flow, but I am (somewhat) aware how poor the flow is on this car stock.

 

I'm not saying to not change the intake. My suspicion is with the stock cam, that the intake and exhaust probably aren't even that much of a restriction to begin with, so the change in airflow moving through the engine will probably be not that significant.

You may see a little seat of the pants improvement. But I'm doubtful it would throw off the stock calibration that much.

Now, if/when you do the 350, then all bets are off at that point. At a minimum, the displacement constant will need to get changed. Then depending on what parts you put on it, further tuning could be required.

 

I did seem to misunderstand haha. I appreciate the info and now I can get to further planning.

 

Few choices if you go with a mostly stock 350 atjp tune for your existing ecm or the 747 is direct plug and play from a truck if using swirl port heads and want to keep cost down or Dynamic EFI ebl. Not sure I’ve seen a displacement in the stock $61 mask ?

 

atjp tune gif your existing ecm or the 747 is direct plug and play from a truck

Please translate without abreations. Thank you.

 

IMO, when you can and if you can... yes tuning makes it way better. Even stock OEM can be retuned for better (I speak for TPI).

Your RS came with the L03 TBI engine I assume. 170HP factory!!! Search the TGO thread and you'll see what can be accomplished as far as performance. Opening up the exhaust and air intake might yield you... 30hp maybe. Is it worth the trouble?

Here's my 2 cents worth with a bit of experience.

1) Learn as much as you can about your car and tinker with it.
2) Fix it, refurbish it, study it, learn and keep it stock, you'll get lots of satisfaction out of it (a bit of history too)
3) When you feel ready, go for your engine swap, but remember... it works as a whole, so engine swap means more HP, means every other systems need upgrade.

IMO, best mods is subframe connector and upgraded front brakes before any power adder.

Here's an excellent book I read years ago that really help me get going:

 

I'm definitely going to look into that book. Currently I want to do the exhaust system mainly for the sound, and also to prep for a more power in the future. I definitely want to start working on the car myself, might as well look into tuning as from what I've read it seems if I wanted to keep the TBI system, you really should have the equipment to burn the chips and such yourself. I am still conflicted between keeping the stock type chip and converting to some sort of newer system that's easily tunable. But that is something for down the road. I also don't know if I will do the intake as I am just interested in cleaning up the sound of the car a little. I am not looking to these parts to add power. I was looking at crate engines for the future and the minimum horsepower for the 350s on the one website I was checking was around 390. I do realize that with that amount of a power and torque increase the rear would just disappear, so I will have to quite a bit of work on that end, as well as a disc brake conversion. I will probably do the disc brake conversion much earlier than when I actually add power to the car anyways. For now all I want is to restore this car and have a little bit more fun while driving it.

Thanks for the info once again.

 

Do the exhaust if you want but I wouldn't waste time or money on an intake manifold for a tbi305. the stock manifold flows fine for the stock cam, exhaust is probably fine as well but it will be nice to already have it done when you inevitably put in a bigger engine.

Do the exhaust and start getting an engine and parts together for an engine swap is what I would do.

 

Thought I would add on to this thread rather than start a new one.

I have a 1989 LB9 T5 G92 car. It is all stock except air injection and pump are removed. The second owner installed headers, but the third owner did not like the headers and installed cast iron manifolds, an EMI dual cat and Y pipe (2 1/4"), Davico intermediate pipe (2 1/4") and a Walker muffler with tail pipes. None of it is mandrel bent and all are aluminized steel. The cast iron manifolds are not stock part numbers so not sure what they are from.

I plan on replacing this restrictive exhaust with a set of American Racing SS headers and connection pipes (1 7/8" to dual 2 3/4") then a Y fitting to 3" (no cats as I am smog exempt where I live). I plan on using Stainless Works 3" SS exhaust system with Turbo muffler and 2 1/2" tail pipes.

As far as I know I have a stock ECM (ANYS 9350). I'm sure a custom prom will get the best performance but will the stock tune be acceptable or at least safe for the engine?

 

IIRC, your LB9, M5, from 1989 was a stock 225HP engine if equipped with the N10 option (dual cat). I don't remember if G92 included N10. In any case, you are looking at 220-225HP max with stock set-up. With your proposed exhaust, that will certainly help the engine to flow better. But in my opinion, 1 7/8" is overkill, unless you plan later on cam/heads, intake etc... Expect to gain about 15-20hp with the improved exhaust. I had an LB9 improved about 30-35HP with shorty headers, primary 1 3/4" to 2.5" Y, to high flow single cat, to 3" combined with CAI, TPI foil, underdrive pulleys and custom PROM. In any case, it's a lot of money for not much now a days and it will be loud without the cat.

And yes, a custom tune will be way better. The original tune was most likely rich at WOT-PE (Power Enrichment), so it might compensate ok with you new exhaust.

But before anything, I would datalog to check if everything seems normal. I would you put a new 02 sensor first for good measure. FYI, the 02 sensor signal at WOT can give you a ball park AFR at WOT based on 02mv:
830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1

In any case, on your new set-up, I would install the 02 down stream near the header collector on either bank. That would be better, as long as you convert to heated 02 sensor.

Good luck
Peace

 

It will be safe, and it will run fantastic, compared to how it runs now. A custom PROM will get the best performance, but you'll get 95% of the benefits from the exhaust alone....and it'll run great.

 

Adding a heated 3-4 wire o2 will help retain closed loop. If it’s all stock 305 it’s probably running pretty good with the stock calibration. Can always datalog with $6e adx using tuner pro rt to see fuel trims.

 

Thanks for the experienced input! Starting around Feburary all 1989 LB9 G92 cars had the N10 dual cats. I think with the LB9 the only way to get N10 was to also have G92. I think all the L98 cars had N10 starting in 1989?

Agree 1 7/8" is probably overkill and 1 3/4" is more than adequate especially for a 305. I just thought the larger tubes were cooler looking but there is something to say for exhaust velocity when tuning headers so maybe 1 ¾” would even perform better?

To be honest, my car is very original low mileage car and if it had the stock manifolds, air injection and exhaust, I would probably just keep it that way (Although I really don't like the noise of airpumps). I may consider finding some stock manifolds and plugging the air tubes. I think both the LB9 and L98 use 14094063 and 14094064? Then I would install this Y pipe: https://www.hawksmotorsports.com/82-...nifolds-hawks/

Not sure if I also need the HO spacer on the passenger side for this Y pipe to work? I sent a note to Hawks to see what they say.

As far as adding headers, I was thinking to go through all this hassle why not?

In any case, I do like the idea of having a stainless exhaust on a car I plan on keeping for a long time.

 

I've got a complete setup we just pulled from a '89 L98 Camaro, idk where you're located so shipping may be cost prohibitive.