ayrton_rx7

Hey, I have an 85 GSL, which is completly stock, and I was wondering how much faster my car will be once I take off the pollution gear i.e. air pump, and put on a bigger exhaust and better air filter?

What other things can I do to the car that will make it faster, but still reliable, besides porting or forced induction.

Thanks for your time

Ayrton

aarons

lightweight flywheel.......bigger carb

t3hranger

what i have done on my 84 gsl was got a new air intake and added a hood scoop and then did a RB header and a high flow cat+ehaust. That will give more power.

trochoid

iTrader: (6)

Emissions removal will have little hp gain. Biggest bang for your buck is exhaust, which will require removing the cat and air pump, next to do would be a carb upgrade.

Kentetsu

Removal of smog components (excluding cats) will mostly be a weight reduction/simplification advantage. Upgrading the exhaust will definitely be a big step in the right direction. After the exhaust is done, look into a better carb (Sterling is nice), along with a better fuel pump. There is also a lot of power to be found in an ignition upgrade (see the transistor trick thread for details). Electric fan will also help a little.

Rogue_Wulff

As stated above, emmissions equipment removal will not increase power, unless there is a problem in the system. It will make getting to things easier, though.
A clogged cat, or vacuum leaks in the rats nest will affect performce and fuel mileage, but if the system is fully functioning, it will not harm the power output.
A free-flowing exhaust can really help these engines to perform better, as can the e-fan.
A word of caution: removing the air pump can result in the water pump pulley slipping. Adding the e-fan can help to prevent this, as can going to a duel belt alt pulley.

ayrton_rx7

Thanks guys, this is great information, I'm thinking of getting mechanical secondries on the carby, what are your thoughts?

Thanks once again

Rogue_Wulff

I'm planning to try the mechanical secondary mod on my car, mainly for a little better autocross times. Too much on-off-on the throttle for the vacuum secondaries to open when desired.
Doing this mod often leads to a minor "flat spot" or "dead spot" as the secondaries open, and requires relearning the foot operation. First 1/2-3/4 can be mashed like always, but the last bit must be done a little slower, to overcome the lack of adaquant travel in the accel. pump of the carb. Also, mashing it too fast, at too low RPM, can cause it to bog a little.

aussiesmg

iTrader: (1)

Lightening the flywheel mods doesnt raise horsepower, but makes the engine rev more freely, it also can make the car harder to move away from stationary.

Rogue_Wulff

So true. In fact, a lot of drag racers will actually tell you that a lighter flywheel generally gives a slower time. Slower launch causes slower overall time.
Road racers use them, as the engine will rev a little quicker, and deccelerate quicker.

Roundabout

iTrader: (8)

I know exactly what you mean by "relearning the foot operation." If you floor it too soon it will hickup.

CharlieBrownRacing

ok so go read sterlings write up about mech sec and the accelerator pump issue. that is what is causing your "flat spot" opon opening your mech secs. u can fix it guys really

hmmm six years old oh well

Xamnglc

iTrader: (1)

To say that emissions removal does not increase power is incorrect; The 3 cats create exhaust backpressure which decreases performance. The 2 in the front are notorious clogging and even if all 3 perfect/ brand new performance will suffer. The concept is simple, get rid of exhaust and take in new air, however quickly you do it is dependent on the exhaust system and that's why a header will help performance. Most of the emissions stuff in a first gen rx7 is for those 3 cats, to make sure they get to the proper temperature fast and stay there... Air pump, Air Control Valve, Anti-Afterburn valves, Relief air, Switching air, richer solenoid, all of this stuff is for the cats, that’s why when the cats go this stuff can go too.
On the other hand…

Vacuum advance helps performance, letting the computer control it is even better because the computer can shut it off when cold so your car doesn’t lean out and stall on the cold winter days…

The purge valve should be kept because it vents crankcase/bowl fumes
Many remove or disable the coast/shutter valve only to be disappointed with the loss of mpg

I have written more up about this in another thread…
https://www.rx7club.com/1st-generati...l-mod-1005150/

DivinDriver

iTrader: (15)

What's a "Cat?"

And this "computer" of which you speak... Don't have one of those either.

xXGslseSleeperXx

lol, and the purge valve has nothing to do with venting the crankcase

xXGslseSleeperXx

its more for the charcoal canister thats hooked directly to the filler neck

AXA

iTrader: (2)

Good to know, shopping for a RB complete exhaust system as we speak...

ray green

iTrader: (14)

You should also upgrade to a high performance computer. The stock computer keeps the shutter valve from opening at the right time and limits output to 100 BHP.

Seriously, the above post by XAM is so full of misconceptions it's hard to know where to begin.

DreamInRotary

iTrader: (49)

So I'm not the only one that didn't follow that. 6yr thread contribution, fun times.

I'm putting my rats nest back on and doing exhaust soon, and i know the car will run better, idle smoother, and hopefully get a little better mpgs.

Another rats nest removal war I smell coming on here.

Xamnglc

iTrader: (1)

MY statements are based on Mazda service manuals, to say I'm wrong is to say they are wrong...

The Emissions control unit turns off vacuum advance when cold and when decelerating… For more info check my other thread…

The shutter valve does not increase performance it increases MPG...

The truth is that Ray Green Does not know what any of the items in the rats nest are for, that's why hes fearful of removing it...

t_g_farrell

iTrader: (1)

Or maybe you misunderstood them. Or maybe its right for certain years and not
others. I know for a fact theres not 3 catalytic converters on any 1st gen. The only
computer is the one for emssions only. It doesn't run timing or analyze exhaust
gas temps or oxy sensors. Based on some simple logic it cuts some vacuum out
or disables firing the rear rotors sparks or whatever. It does all these things in ways
that vary year to year on the 1st gens. Also, most of what your spewing here applies
to FBs and not SAs so far.

As to Ray, show some respect for our elders. He deserves it. Go Blue!

ray green

iTrader: (14)

Good point Tim.

But go easy on our Grasshopper XAM. He's just learning that the Road to Wisdom ends not with the Acquisition of Knowledge.

And you know me. I'm just trying to simulate conversation and limit didactic claims by posters with fewer than 100 posts.

Xamnglc

iTrader: (1)

thats true, most of the info stated is 1981 thru 85, he says he has an 85'

DivinDriver

iTrader: (15)

Not on all models, and not on all builds within specific models for that matter.

Show me where a Mazda FSM for first-gens refers to the ECU as a "computer" as you did in your earlier post... Then we can discuss the concept of where any errors originated.

The truth is, with a statement like this you will be making a very poor reputation for yourself within a community that thrives on reputation... and Ray has proven over his years of membership here that he knows what he talks about. Talks it, and walks it.

Book knowledge is very useful, but it does not equate to lengthy hand's-on experience.

In that regard, we know Ray's expertise. We've seen it demonstrated.

You, not so much.

Xamnglc

iTrader: (1)

I was responding to the first question which was about an 85... It's true that the information might not apply to say an 80 or 79, but the question was about an 85... Do I need reputation to be right? or smart? I'm an electrician by trade and come from a different era, so when I call it computer am I wrong? Not really, the ecu is a computer albeit a very simple one. The word "computer" implies logic. Why argue over semantics? When Ray Green suggests that the shutter valve has anything to do with performance, or that cats don't create back-pressure then I begin to question...