Cuzy

Hey Gang: I'm in need of a new exhaust and I see several different combinations from Bonez and Racing Beat and Victoria British. I'm curious what you guys think of my choices.

First, I've got a stock '85 GSL with original stock 12A engine (170K miles). I'm not getting very good acceleration or speed (tops out at about 70mph with a good tailwind), and I'm not sure if my current exhaust system is to blame.

Exhaust consists of original manifold and first two monolythic cats, which are hollowed out, then hollowed out main cat and muffler from an '83 or '84 RX7. The cats hollowed themselves out, although I had to disconnect at main cat to clean out the blockage of broken up catalyst from first 2 cats.

I'm suspicious that some of the converter material may be blocking the muffler. I'm thinking of disconnecting either the main cat or muffler and test driving to see if it restores much of the power.

If it does, then I will be needing to replace my exhaust system. From investigating on the web, I see I can do any of the following:

1 Replace entire exhaust with Racing beat system (header, presilencer, powerpulse muffler) for $540 direct from Racing Beat

2 Replace all 3 hollowed out cats with straight pipe from either Racing Beat ($110) or Bonez ($125) and RB muffler ($237).

3 Replace all 3 hollowed out cats with straight pipe and much cheaper Victoria British Monza muffler (~$140).

4 Replace all 3 cats with Bonez Hi-Flow Cat Converter for $245) and either RB or VB muffler.

Option 1 is pretty expensive for a rusting 18yr old car. I'm not sure how much of a PITA it will be to remove the original manifold.

Option 2 and 3 make me curious how loud the exhaust will be.

Option 3 makes me wonder how long the Monza muffler will last. Anyone have first hand experience with this muffler living in midwest (Indiana) rustbelt?

I would like to know if Option 4 would reduce my car's stinky exhaust smell. Currently there is no catalyst material to clean up my car's smell. It is really powerful. My wife was following me in our van and she could smell it. It remains in our garage for hours when I drive home (I'm sure after I turn off the engine, the unburned hydrocarbons and oxides of nitrogen slowly eke out of the tailpipe...)

Has any one gone from no cats to either the RB or Bonez hi-flow cats and noticed the exhaust smelled a lot better?

Thanks much, Cuz.

Nick-7

My car smells real bad, especially when sitting at a stop light. I think you either have some serious exhaust restrictions, or you have low compression. I don't know anything about the monza mufflers, but as long as it will withstand the heat I would just buy it and replace the cats with a straight pipe.

rotary emotions

RB exhaust are the best, period. Anything less will be a waste of money.
Monza etc are NO GOOD! Search the forum and you'll come up with the same answer: Racing Beat...

poweRX-7

It tops out at 70mph with a tailwind?!?!?! i would get the compression checked before i put money into the exhaust. Even though it is old and stock, you should be able to top out higher than that. when my 85gsl was stock, i hit around 120, and i pulled off because of the floating nose.
Anyways, Monza is ****, don't waste your money. I have the RB header and presilencer, but don't have the RB muffler and i can't complain at all. Although it is loud.
jeff

Cuzy

Thanks for your thoughts guys!

Back in '98 was the last time I checked the compression. I know that is a long time ago in years, but it is less than 10K miles ago on the odometer.

Using a standard piston engine compression checker with the check valve removed, I saw even bouncing of the gauge's needle to 100psi in both rotors. This was with engine warm on a warm August day, battery fully charged, throttle wide open. I could easily restart engine, but then, as now, my car would top out at 70.

Does this seem like low compression to the point of needing an engine rebuild?

The last time I used auto tranny fluid to get my RX7 to start was also in '98 (I quickly learned that if I start it, I better let it fully warm up before I shut it off). With the engine cold, battery fully charged and throttle wide open I measured 108psi in front rotor and 125psi in rear rotor BEFORE the ATF treatment (engine still wouldn't start).

After pouring in ATF through carb and spinning engine a few times, I saw increase in compression to 138psi and 148psi front and rear, respectively. Engine started immediately when I put in clean dry plugs.

Do you guys have any experience with what are OK compression readings, and what readings signify the best thing to do is either rebuild the current engine or swap in another vintage 12A with many less miles on the clock?

Thanks for your assistance! Regards, Cuz.

bubba211

100-120psi is good, but i don't think a regular piston compression checker will work. Correct me if i'm wrong.

bubba211

100-120psi is good, but i don't think a regular piston compression checker will work. Correct me if i'm wrong.

Cuzy

I thought I could "read" the "bumps" of the compression meter's needle as the three rotor "chambers" each go through their compression cycle as the rotor spins in one complete revolution.

With the check valve removed, the needle drops immediately as the rotor continues to spin but then comes back up again as the second rotor face approaches.

I read about this in the old RX7 forum on majordomo back in '97 or so, and I have found it useful since I don't have the money for a real rotory compression testor.

At the very least, it gives me a good seat of the pants feel for the compression of my engine.

Since you think my compression is ok, I'll look at the restriction of my exhaust. If it is ok, then I'll investigate my Nikki carb (I'm pretty sure it needs rebuilding as there is black gunk oozing out from between some of the gaskets (my RX7 sits for many months, as you can tell since I've only put on 10K miles in approx 5 years).

Rgds, Cuz.