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Exhaust Upgrade and Lean Condition

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Old 09-22-18, 01:58 AM
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Where's my 10mm
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Exhaust Upgrade and Lean Condition

So my catylitic converter has been rattling (be it very loudly) for long enough, and it's time to use that RB header I've got lying around. However, now that the car has seen the road for a few tanks of fuel, upon inspection of the spark plugs it would appear it's running a bit lean (photo included).

Just trying to figure out why I'm getting 10mpg with it running 'lean'. It's also running a little hot, which I'm assuming is mostly due to the lean condition (around 190 with outside temps of 70ish). Yes vacuum leaks and such are things to check, but I have found none so far and I rebuilt the carb less than 200 miles ago. The other bit is I'm curious if doing the exhaust (mind that it was done previously with a single 3+1 cat while keeping the 82 header box, by the PO) will make the lean issue become worse. I've seen a few posts saying they had to re-jet their carbs when they did their exhausts.


The car is an 80 with a later (82ish) 12A engine, manifold, carb, etc... While it still has the 80 ecu and harness. Running ported vacuum advance and all ratitude has been delt with other than the releif solenoid and the associated ACV system - only port air is operational, split air and the shutter valve have been disabled.

First I would like to clear up if changing the exhaust will make it worse or require a re-jet. After that I can always mess with other things that could be causing it to run lean. Looking at doing the exhaust next weekend so I'll have to be ordering parts shortly if it won't make problems worse.

Thanks
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Old 09-22-18, 09:44 AM
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That plug does not show a lean running condition,looks rather normal for a plug that has some miles on it.A lean running condition will show a plug with off white to light gray deposits. How long have they been in the engine,correct plug? Maybe a fresh set?
How,where are you measuring coolant temperature? 190 is about right-regardless of ambient temperature to a point. Thermostats' job is to get engine up to temp quickly and keep it there,appears to be the case here. What thermostat do you have in your engine?
What carb are you running? If a Nikki,are you certain you haven't mixed up air bleeds and jets,as in inadvertently switching primaries/secondaries? Are you certain your leading/trailing initial/centrifugal/vacuum advance timing is correct?

You comment that the cat is rattling on this car,also say emission systems are removed. 1st,the fact cat insert is rattling is indicative of being loose,more likely substrate has begun to break up and likely partially blocking exhaust flow=restriction,causing a low power condition. Need to remove and inspect,remove. I don't say replace as running car without air pump,ACV is one of reasons cat is rattling. Simple fact is cat has a very short life without those components,runs so hot,will begin to melt and break down and break up.

As far as running lean,it is not common for these carbs to run lean when removing manifold/cat and using a header. What you put on car for exhaust system behind that may,you don't say what type of parts you'll be ordering. Best exhaust for these cars is Racing Beat stuff. Street Port system is the absolute best. Since you already have the RB header,buy their presilencer,power pulse muffler and have an exhaust shop make the intermediate pipe to connect them. You will have a tuned exhaust specifically for a rotary with a good mellow sound.
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Old 09-22-18, 10:02 AM
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That's not lean. Were you expecting blackened with carbon or something? Or white as a ghost? What you have looks pretty normal.
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Old 09-22-18, 10:04 AM
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Plug looks good to me also. If you are getting 10 mpg you either have tuning issue with the carb or you're driving around at 6k all the time but still have a small tuning issue. How are you measuring the mpg?

You should be filling up at the same station and same pump, driving, then noting miles driven at next fill up at same pump trying to fill to the same level. Then divide miles by gallons and get your numbers. Average them for a few weeks to get an accurate number. You may already know and be doing this if so consider this some info for others that may need it.
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Old 09-22-18, 10:09 AM
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Well thanks for all that info, I guess I've been living with some misinformation up till now . I measure the engine temp on the top of each housing, at the bottom of each, along with the water pump/coolant system. The 190 was just an average of what I generally see. I'm still running a 180 thermostat. As for plugs, yes they are the correct set although they are getting a bit old. I bought this set when the car first ran (not driven until recently though), nealy two years ago. Not too long ago they had internal shorting issues that was remedied with some cleaning - the car (before all the part swapping) had run very rich, and so the plugs fouled regularly. As for the jets... it's a Nikki and when I did the rebuild, I used the FSM for jet size and placement along with a quick sketch I made for cross referening, as such I seriously doubt they are in the wrong spots. Float levels are also fine. In all honesty the plugs are whiter/grayer in person as my phone likes to oversaturate colors, but I'll assume you know better than I that it's not lean. I guess I'm a bit rusty with reading plugs . Looks like I've got an exhaust in my future.

Thanks again.
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Old 09-22-18, 10:19 AM
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Wow everyone replied at the same time.....

As for the mpg, yes, same pump and I'm doing the calculations as you stated. I think the biggest issue is that my daily commute is so close; the car spends almost as much time warming up as it does driving. Any clue what the fuel consumption is at idle/1.5k for a stock Nikki 12A set up? I do run the revs out fairly often, but I still cruise around 3k so...

I'm gonna bet I won't know my real mpg before I do a longer trip or something. How long do y'all let your car warm up before pulling out of the drive? To get my defog going and engine temp up a little it usually takes 2-7 minutes. A long time to sit in the driveway every morning with the choke out, but it stalls so darn easy if it isn't warm - maybe a new, clog free, exhaust will help remedy that.
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Old 09-22-18, 12:53 PM
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A redone Nikki will help you as well. Notice I didn't simply say "rebuilt Nikki" as most rebuilds ruin the carb because you can't get stock rebuild kits anymore, only aftermarket, and everyone tries to use the bad parts in the kit because they are there.
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Old 09-22-18, 02:35 PM
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If your header is a road race, I have a nice center section that would work nicely for you if interested. Check out my FS thread or PM me if you want
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Old 09-22-18, 08:58 PM
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Originally Posted by Benjamin4456 View Post
Any clue what the fuel consumption is at idle/1.5k for a stock Nikki 12A set up? I
0mpg. it is miles per gallon, after all.

i usually start mine, and put seatbelts on, adjust heater etc, and then go, its like 10-30 seconds, the P port gets another 30 or so seconds. i do not drive hard until its warmed up.
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Old 09-22-18, 11:03 PM
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As for the rebuild, I did avoid the "new" seats, etc. while everything else was cleaned thoroughly. I learned the seat issue the hard way when it kept flooding all the time - those things are so cheap it's just sad. All I ended up using from the kit were some new crush washers, cotter pins, and the gaskets. Right now I'm actually running SA style springs, clips, seats and floats in my 82 carb. I've found the earlier design less prone to flooding for whatever reason and haven't a reason to swap back.

Unfortunately for both of us, I only have the single pipe RB header so the two pipe road race mid-pipe won't do me much good. Ironically I've got a two pipe "muffler" the PO janked up to the stock header. Thanks for the offer though.

Last.... Thank you for that amazing piece of brilliance . I suppose I should have specified it as gallons per hour (or some other unit) for those who like to take it more literally . I've found that my car won't idle much above 500 rpm until it's been running a little, and with the headlights on it practically "dies" while cold. Hot idle is about 700-800 and then all is fine. I'm about to do an '88 alt swap though which should make the lights-on issue a little better. Hopefully it will stop my flickering headlights and self aware radio issues too. I've done all the other testing to determine it's the alt, and it's bearings are so loud that it drives me crazy enough that it needs replacement regardless. I'm also running a sub and aftermarket stereo system so...

Thanks for all the advice.
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Old 09-23-18, 10:40 AM
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Originally Posted by Benjamin4456 View Post
I've found that my car won't idle much above 500 rpm until it's been running a little, and with the headlights on it practically "dies" while cold. Hot idle is about 700-800 and then all is fine. I'm about to do an '88 alt swap though which should make the lights-on issue a little better. Hopefully it will stop my flickering headlights and self aware radio issues too. I've done all the other testing to determine it's the alt, and it's bearings are so loud that it drives me crazy enough that it needs replacement regardless. I'm also running a sub and aftermarket stereo system so....
An alt swap will help with charging the battery, but regardless of the alt, RPMs below a certain amount, 1000 or so, will not charge the battery enough to keep up with load. My guess is that the battery AMP-hours isn't great enough. The CCA is also important, but they only count during cranking.
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Old 09-23-18, 12:52 PM
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Considering the equipment(electrical load) you're running,may want to upgrade the alternator output(further than stock 88FC) and its associated wiring.
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Old 09-24-18, 10:56 AM
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From what I've found, the 88 alt is the last drop in alt that requires no rewiring. I'm open to suggestions for other alternators if there are recommendations from the forum. I could care less about rewiring, more so it's the budget that is the limiting factor. What do most folks upgrade to? Looking at buying new or reman, not going to a wrecker.

Also, the battery is rated at 750 CCA although while trouble shooting the electrical system, I found it was putting out nearly 1000 CCA. Not sure about it's capacity. It's a cheapy battery I bought back when I was first trying to get the car running, and honestly it probably needs to be replaced.

Regardless, the alt needs replacing so suggestions on what to put in are welcome.
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Old 09-24-18, 11:52 AM
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I'm running an FD alt. It's expensive as all get-out but it's 100+amps and bolted into place physically with just a pulley swap. The wiring is slightly different but it's not terribly dificult - you need to add a diode to the line that's coming from inside the car with 12v-ignition because otherwise when the car is off it will drain power. You also need a power connector cut from a harness of any type similar to the FD.

There are cheaper options. I remember someone around here putting a GM alt in their car but it needed some work to get it mounted and connected. The advantage there is that it was over 100 amps and cheap like borscht. You could find them at any junkyard and even new ones were way cheaper than ours.
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Old 09-24-18, 12:43 PM
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So your flickering lights issue and the alternator loading lends me to think you need to do a relay setup for the power to your headlights and while you are at it you can upgrade to some H4s as well. Used to be you could get all of this as a kit from Black Dragon but unfortunately they are out of business now.

See https://www.danielsternlighting.com/ for some good info on how to do this.

I did a write up awhile ago on installing the BD harness and H4 kit that may help some: https://www.rx7club.com/1st-gen-arch...lation-695121/
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Old 09-24-18, 01:12 PM
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FD alternator on my SE. I believe oe output for FD alt is 90 amps,after changing pulley it is a bolt on. Need to upgrade output wire from alternator to an inline fuse going to battery thats slightly higher than alternator output. .
The original output wire went from alternator to main fuse link on drivers side fenderwell,larger gauge wire needed to support higher output impractical to connect at fuse link. Direct connection to battery with inline fuse is most straightforward way to go.
You will have to do the field wire mod that vipernicus42 describes,very easy. A new field plug will be necessary and connector/pigtails can be bought on bay of e for about $ 16 to allow a professional looking installation.

You will need to run a dual belt pulley setup as the single belt used on original setup will be inadequate,need to lose air pump to do this. The FC alt. install would also require this.
I scrounged a salvage yard FD unit and rebuilt with new bearings,brushes and regulator and fitted a 120 amp stator. Load testing after install showed 128 amp output. Along with dual belt drive i added a Banzai belt tensioner,makes it easier to achieve proper belt(s) tension.
I bumped up alternator output for upgraded headlights and possible future electric cooling fan install.
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Old 09-24-18, 01:15 PM
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Alt install

unable to upload pics.

Last edited by GSLSEforme; 09-24-18 at 01:49 PM. Reason: add pics
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Old 09-24-18, 06:39 PM
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Well guess what random part (among many) happened to be in the car when I bought it:



After reading through tg's write up I realized it looked familiar so out to the garage I went and voila, it's a match! Gonna install this shortly and hopefully fix my flickering issues. Good write up by the way.

Thanks for the alt recommendations. I have't done much more looking yet, but once I do, I'll get back with my findings.


Update: sorry about the ginormous image, I can't seem to figure out how to resize it.
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Old 09-24-18, 07:46 PM
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Before you do anything with the headlights,try driving car til you can duplicate lights flickering. When you can,if the radio/sub woofer is on,turn it off and see if the flickering subsides-especially at low rpm/speed. Subs pull a lot of power in spurts and you may see the lights flickering from that.
Putting lights on relayed harness will definitely help with that,it will also make your headlights brighter as they'll be powered by relays direct to the battery. The headlight switch now only turns the relays on and in comparison to the headlamp bulbs they draw next to nothing taking all the load off your headlight and dimmer switch and associated wiring so those components should last just about forever.
Looking at relay harness pic you posted,it's apparent it's been somewhere damp as the power leads are corroded. I can't see the terminals for the headlight grounds. I would suggest cutting off the corroded eyelets and replacing them.
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Old 09-25-18, 03:49 PM
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Well I got the harness cleaned up and installed last night and the difference is huge. Before my lights were yellow in color and now they are much brighter, whiter, and don't flicker . Install was pretty easy, excluding the fact that the PO stripped the screws on the headlight lids forcing me to cut a slot in most of them to get them off... Otherwise it was relatively quick, clean and easy; although I'm not a huge fan of the bright yellow sheathing.

Previously I had done the testing you mentioned above and found that the lights flickered no matter what. Bumps, no bumps, radio and sub on or off, rpm change/constant, anything. The only thing that seemed somewhat consistent was that the worst issues occurred when I let off the gas and was coming to a stop (probably the idle rpm plus the brake light load).

Still haven't done alt research, but that is next on the list. What pully size (and what double pully for that matter) should I look for. Is there an 'alt swap kit' from any of the rx7 suppliers or do I need to find the tensioner and pully separate?

Thanks thus far.

Edit: Guess I should do my research before I keep asking... Just found the banzi kit with the pullies and belts.

Last edited by Benjamin4456; 09-25-18 at 03:54 PM.
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Old 09-25-18, 05:11 PM
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Figure out what alternator you're using 1st. Fb,FC alternators need a 17mm pulley. FD alternator takes a 19mm pulley. Even though the FD alternator is physically larger,it will bolt in place same as original. However because of the of the size difference,you will need longer belts to accommodate the FD alternator.
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Old 09-25-18, 06:57 PM
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I'd also suggest getting the Banzai Racing alternator bracket regardless of alt used.

Banzai Racing Alternator Bracket Kit (79-91 RX-7)
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Old 09-26-18, 10:26 AM
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Originally Posted by Benjamin4456 View Post
Well I got the harness cleaned up and installed last night and the difference is huge. Before my lights were yellow in color and now they are much brighter, whiter, and don't flicker . Install was pretty easy, excluding the fact that the PO stripped the screws on the headlight lids forcing me to cut a slot in most of them to get them off... Otherwise it was relatively quick, clean and easy; although I'm not a huge fan of the bright yellow sheathing.

Previously I had done the testing you mentioned above and found that the lights flickered no matter what. Bumps, no bumps, radio and sub on or off, rpm change/constant, anything. The only thing that seemed somewhat consistent was that the worst issues occurred when I let off the gas and was coming to a stop (probably the idle rpm plus the brake light load).

Still haven't done alt research, but that is next on the list. What pully size (and what double pully for that matter) should I look for. Is there an 'alt swap kit' from any of the rx7 suppliers or do I need to find the tensioner and pully separate?

Thanks thus far.

Edit: Guess I should do my research before I keep asking... Just found the banzi kit with the pullies and belts.
Good to hear. Next upgrade them to H4 halogens with a decent lens and you will be good to go. I bet the harness has a weak connection somewhere and when the engine bounces or moves around (like when decelerating) it caused the flickering. Using the relays can dampen things like this out but don't be surprised if other electrical gremlins popup down the road, this is your car warning you it has a connection issue somewhere.
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Old 10-01-18, 04:52 PM
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Speaking of connection issues... When I cleaned my grounds a while back my gauge needles went way further up (water temp and fuel). Obviously they were recalibrated to match the poor grounds so is there a way to change them back? Empty tank is now about a quarter up the gauge and operating temp is darned near at the top. Also, is there some remedy to the early year (79-80) gauge lights not showing the needles at night? I know that on the later years they added lights on the top of the cluster that would shine down on the needles but I obviously don't have that. New LED back lights are probably a future upgrade, but will that help with the needles at all?

Now back to the original topic: A friend and I installed the exhaust yesterday. RB header to a Magnaflow 14inch straight through resonator, wrapped up with the muffler the PO installed (it seemed decent enough). 2.5 inch pipe back to a 1.75 inch dual pipe split for the muffler with custom CNC'd flanges. It's a little raspy from inside, but outside it sounds real good. Ironically it's louder outside but I can actually have a fairly normal conversation with someone while cruising - of course not under accel though. Didn't used to be able to do that. Seems like the resonance has gone down but the raspyness up. Definitely sounds a lot more like you would think a rotary would. It also smells better for whatever reason, not sure why getting rid of what was left of the cat would do that. Speaking of the cat... Here's what was left of it:

Not much left in there. Probably a good portion of it is in my muffler...

Something else with the new exhaust is the backfires. The old exhaust had lots of leaks, leading to a constant pop, pop, pop if you let off the gas. Now I'm leak free and the backfires are slightly less common and much more burbly, not tinny sounding like they used to be. Definitely happy with it; hoping there's flames too but I haven't gotten a chance to check that yet .

Alt still needs replacing, although I haven't done much research still. Bearings are getting loud enough that I can here them while cruising with a window open. The relayed lights also seem to have increased load as my radio is doing the shut off thing again. Really just need to get the alt done...

Last thing is a new noise. It's pretty quiet and it's probably just the lack of rattles that I can here it. When I shut off the car, right before everything stops spinning there is quiet noise that sounds just like a cat. Like a living cat, not a catylitic converter. It pretty quiet and just at the very end. I'm assuming it's either the alt, water pump, or air pump. No worries about it yet, just thought I'd mention it and see if y'all have any insight.

Thanks thus far, and I'll keep this updated.
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Old 10-02-18, 08:53 AM
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Originally Posted by Benjamin4456 View Post
Speaking of connection issues... When I cleaned my grounds a while back my gauge needles went way further up (water temp and fuel). Obviously they were recalibrated to match the poor grounds so is there a way to change them back? Empty tank is now about a quarter up the gauge and operating temp is darned near at the top..
I calibrated my fuel gauge on my 83 FB. It was showing 3/4 despite the tank being full. It is a thermal circuit with a bimetallic strip that expands in relation to the resistance of the sender unit in the tank. Here's the thread:

https://www.rx7club.com/1st-generati...-good-1106492/
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