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That all totally makes sense for the way the Weber works, and as much as I'd love a p-port 12A (I'll have one someday, I swear!) I guess my next step is to RTFM that Carl emailed me and maybe learn more about how the Nikki is designed to operate. Unless any of you good gentlemen know of anyone selling a 12A weber set up on the super cheap I think I'll just have tp accept that I have the wrong tools for the job right now and work around it until I can afford the $1000 or so a full Weber set-up would run me. The jet sizes Carl has me interested in trying are only $10 or so from Mazdatrix so I may invest an afternoon into swapping those in to see how they feel.
For anyone who was wondering just how rich the car is running, take a gander at this pic! This is the spot behind the tailpipe after about 30 min or so of tinkering with the idle speed and the mixture. I don't think that's normal!
Hello all! Nothing really has happened to the racer car over the last 10 days or so due to work and life obligations, but the 110/170 jets Carl recommended have come in! Hopefully this Saturday I can begin (and hopefully finish!) the process of swapping the jets out. I'm looking forward to it and I'll keep y'all posted on wether or not the mixture leans out any!
On an unrelated note I picked ups new car! I bought a black on black 1983 RX7 GSL from an elderly lady in my area. The car is very clean and it has 285,000 miles on it! She used it as a delay driver for decades. The catalytic converter is clogged and its running like crap but the rest of the car is in great condition. The cat has been ordered and hopefully I can sort out its running issues soon. It bogs down and almost stalls under acceleration until the pedal is mashed, then it shoots passed 3000 rpm and gets going. I won't post about it much, if any, here on the race car thread but I may start a new thread for it. I'd like to daily it as a companion to the racer. Hopefully some of the knowledge and experience I gain from wrenching on one car translates to the other!
Alright, Lads I've just taken the carb off of the car! now its time to disassemble as per Carl's pictures (posted earlier) and I'll serif I can get the jets swapped over!
Hello, gentlemen! Now that my long work week is over I can get y'all up to speed! Last Saturday I was finally able to get cracking on re-jetting my carb. I got the carb off the engine in no-time-flat and broke it apart on my workbench to find that the jets had already been swapped to Carl's recommendation 120s and 170s, the issue however was they'd been swapped primary to secondary!!
I have no idea what that may be, but I assume that it was done to aid the failing engine in starting be grossly enriching the mixture to aid the starting with the failing seal springs. I swapped the jets to they're proper locations and threw the carb back on the engine.
The good news: the engine now runs so much smoother and so much better! the low and midrange throttle response is much tighter and the engine revs up and down so much better than it had before.
The bad news: the engine is running hotter now given the engine is running way leaner at low RPM than it used to. That's not a long term issue as I have a Mishimoto electric fan coming in the mail. The worst news however is the engine is NOT ported in any way! The brap idle was caused by the super rich idle. That just means that I'll get started on gettin a P-port 12a built much sooner than I was initially planning seeing as I don't have a B-port motor to throw in once I move classes to a faster set up as I evolve the car. It's a bummer but in the end I'll be totally fine with the set-up I have.
On a related note: the engine running as rich as it was has really diluted my oil with gasoline. I'm currently running Royal Purple HPS 20W-50. Racing Beat says they recommend 10W-40 for NA racing engines. What weight and type do all y'all run? I'm thinking of following their recommendation but I'd love to hear what you guys use and why!
Lastly, a HUGE shoutout to Carl who was foolish enough to give me his cell phone number! I pestered him all day while i was swapping jets and testing the tune with questions and pics and he really helped me greatly! I also talked with him about a noise in my rear end that may be jus the brake pads moving in their seats (as he suggested) but I won't know for sure until I can get testing that. I'm currently trying to swap intake manifolds on the new daily (the black 83 GSL I have yet to name) as it had a gnarly vacuum leak and a clogged cat. I'll be starting a thread for that shortly.
20w/50 Valvoline VR1 racing oil. In the past we have used various synthetics and semi-synthetics but the Valvoline seems to transfer heat better (oil temps are lower). Plus it is cheap and available everywhere unlike Amsoil, Royal Purple, M1, etc. So I change it allot and it doesn't break the bank.
Viscosity selection is from recommendations from various engine builders I have spoken too. Rotary engines have really big bearing journals and I don't think a thinner oil is a good idea.
Idemitsu did the oil development for the Lemans cars, and there is an SAE paper. they found what you'd expect, lighter weight was more efficient, but there is more wear. if you look at the graphs that they have in the paper, for a street car 30 is fine, a race car 40 is about right. they used a 50 weight, its a long race. in a street car you'd want like 5w-30 or something, but in a race car the additives they use to get the oil to thin out at low temps can be weird, so 20W-50, or even a straight weight 40 is ok, although you need to get the oil up to temp before you beat on it.
and then at the end of the day the rotary doesn't care much, especially compared to some other engines that require special oils
Well I'll then I guess I'll stick with good old VR1 then!
The updates on the race car are that there aren't any right now. I've yet to be able to get to the track, but now that the car is running really well and seems to be pretty well sorted a track trip is the next big step. My focus lately has been shifter over the the 83 RX7 daily recently. Currently that car is running awfully and I'm trying to go through it to get it usable. I'll be going into detail on the thread dedicated to that car, but I'll link it here incase any of you distinguished gentlemen want o hop over there and check it out. Suffice it to say that I believe the smog equipment is causing the engine to run like crap, but as I'm in Cali I'm retiscient to remove it long-term, but I may have to short term just to get the car usable. I'm nowhere down with the race car, I just need to be able to get to work to earn money for more parts!!
Hello gentleman!! The absolute tonne of maintenance work I needed to accomplish to get the daily usable on a daily basis has been (pretty much) completed! So now I'm free to get back to wrenching on the racer! The few test runs I've had in the car after changing the carb jets had the car running really well. I think I mentioned it earlier but the engine revs so much more freely and doesn't hesitate anywhere in the RPM range now that the A/F ratio is closer to where it should be. The new issues that have cropped up seem pretty simple to handle. The engine now seems to run much hotter than before and it also seems to be running much leaner than before. The latter issue is probably causing the former! I don't have access to a wideband to measure the A/F ratio but I'll tweak it with the butt dyno to get it running a little better at idle/lower RPM. To address the cooling I've purchased a Mishimoto electric fan and I'll hopefully get that installed soon.
The next major project I want to begin for the Mozu the racer is to prep another (potentially hotter) engine. Considering my goal is to go endurance racing I'd like to have a spare engine available if I'm ever in need of it. I currently have a fully-dressed 12A out of an 83 auto with the counterweight sitting in my garage. I'd like to strip it of it's smog equipment, affix a lightweight flywheel and a 4-puck spring clutch disc, instal the 13b oil pump and RB street performance oil pressure regulator, and convert the carb to mechanical secondaries and top it off with a power pulse intake! I have only briefly searched the forum here for tips and instructions on how to accomplish the carb mods and reviews on the lightweight flywheel sort there. When I have more time I'll look more throughly. Before I do that does anyone have any warnings or advice in regards to any of those ideas or plans?
Regarding the Carb. Some of the guys I raced against in Improved Touring did the mechanical secondary trick but I never did because it wasn't legal. It probably works because so much time is spent at WOT with a stock port 12A but since the Niki doesn't have a accelerator pump for the secondaries making them mechanical could cause slow corner driveability issues. As long as the secondary diaphragm is working, the secondaries will open when the engine calls for it.
Regarding the power pulse intake. Spend some time making a cold air intake set up. Drawing in air from the engine bay, no matter how good the air filter housing is, will not make more power than air sourced from outside the car. On my car, I removed the snorkel from the OE air filter housing and welded on a piece of 3" exhaust tubing and ran a hose over to a remote cone filter that had access to "fresh" air. Seemed to work better at the top end.
Regarding the Carb. Some of the guys I raced against in Improved Touring did the mechanical secondary trick but I never did because it wasn't legal. It probably works because so much time is spent at WOT with a stock port 12A but since the Niki doesn't have a accelerator pump for the secondaries making them mechanical could cause slow corner driveability issues. As long as the secondary diaphragm is working, the secondaries will open when the engine calls for it.
I understand the lack of accelerator pumps in the secondaries may cause slow corner drivability issues. I haven't gotten the car on track yet (I'm really trying hard to get it on Big Willow this 23rd) so I can't speak to how the current mechanical set-up on the car handles in slow corners, not that Big Willow has many of those anyway! I do hear what you're saying in regards to the engine getting all it needs if the secondaries are functioning properly; after all, it is a stock engine so it should function with a stock carb set-up. Vacuum systems are always a point-of-failure concern for me, but I guess a properly sorted system should be properly sorted so in reality that's probably a non-issue.
Something that is interesting to me is that the mechanical secondaries on Mozu the racecar function extremely smoothly and it's impossible to tell when they engage. The vacuum secondaries on the daily on the other hand are very noticeable. There's an abrupt boost of power as you really get on it in a way similar to how VTEC was described to me. The mechanical secondaries I have feel much better to drive and I'd like to keep that.
Originally Posted by mustanghammer
Regarding the power pulse intake. Spend some time making a cold air intake set up. Drawing in air from the engine bay, no matter how good the air filter housing is, will not make more power than air sourced from outside the car. On my car, I removed the snorkel from the OE air filter housing and welded on a piece of 3" exhaust tubing and ran a hose over to a remote cone filter that had access to "fresh" air. Seemed to work better at the top end.
As far as a cold air intake go, what do you think of this set up currently on Mozu the racecar? I was thinking that a Power Pulse intake may be freer flowing and less restrictive than a stock air cleaner, but I understand a cold air intake may have better energy density than even the power pulse intake. I have an extra air cleaner or 2 laying around so I can modify one as you did if I need.
Last edited by IMSAaspirations; 07-10-21 at 10:04 PM.
Reason: Added a picture
Cold Air > Free flowing air cleaner that is getting air from the engine compartment. Back when I was running IT, I would have killed for a setup like the one on the Mozu the race car but it would not have been legal.
Maybe the best setup would be an air box around the the Racing Beat power pulse and supply it with air like the Mozu set up. The Motor Trend show "Engine Masters" did a dyno test on popular V8 air cleaner designs - https://www.dailymotion.com/video/x693421. It is worth a look even though the mule engine is a V8. I used the information from this episode when I designed my air box/air filter setup.
With respect to vacuum secondaries the tuning recommendations was to get the secondaries to open as soon as possible in time with when the engine needed the extra air/fuel. The book stated that if you could "feel" the secondaries open then the secondary spring was too light and the secondaries were opening too soon.
When you "feel" a sudden rush of power on a car with vacuum secondaries you are not "feeling" the secondaries open. In fact the secondaries were already fully open before you felt the surge. What you are feeling is an engine that has caught up with an over abundance of air and is finally able to pull fuel through the secondary barrels. So first the engine was leaned out because more air was added (but not a requisite amount of fuel) and then it reached the point where it could actually draw fuel through the secondary jets.
Blow out all the vacuum ports, install a new vacuum diaphragm and have faith that it works. I don't believe I ever lost a race to a car with a Niki that was cheated up as you describe. Remember that with stock HP you cannot afford any length of time where the engine isn't making max power.
A while ago I dynoed with and without stock aircleaner, with and without Power Pulse and with just the Power Pulse base. There was no real difference between any of those options. I think that just indicates that it is not the restriction to airflow into the engine. I agree with Scott that cool air is the important thing. Your intake was the standard for Pro7 in SoCal and is what I had until I switched to ITA. Then I just ran the air hose up to within about 1/2" of the big hole in the "bulkhead" behind the removed right headlight.
Oh how I love it when y'all take me to school over these things! If Carl says the Power Pulse intake didn't make much of an improvement over stock then I see no reason to get one and make an airbox for it. Scott says cold air is more important than hot, potentially freer flowing air so I'll be sure to make that the priority.
In regards to the methods of secondary actuation I'll be sure to do the maintenance on both the daily's carb, and the extra I'll build for the race motor so they're running properly and have the right a/f ratio. Carl, are you running mechanical or vacuum secondaries? Scott, on your racer do you have all the non-intake related vacuum systems capped, if not removed, from you racer? After having looked over the 81-83 vacuum system diagrams it doesn't seem much would be needed on a race car.
I love that episode of Engine Masters! I remember catching in on YouTube a while back! It really helped me understand the variety of intakes on our old V8 powered racers at the shop, and convince me that all I need is a big salad bowl! The older guys at my shop are pretty well versed when it comes to big mechanical 4-bbl Hollys or Hillborn or Kinsler fuel injection systems, but they have no idea of the vacuum secondaries on an old Nikki on a rotary so they help the best they can with the general concepts but they don't know nearly as much as y'all about the specifics, and nothing we run has vacuum secondaries anyway. I'm loving all the figuring out that there is to do with these things!
My carb was converted to mechanical secondaries about a year ago. The only reason I changed was that with bored out primary venturis there was not enough vacuum signal to open the secondaries. If not for that change I would still be using the vacuum secs. They raced fine that way. Never had a problem. I am sure the diaphragm can fail, but I suspect it is very unusual.
My carb was converted to mechanical secondaries about a year ago. The only reason I changed was that with bored out primary venturis there was not enough vacuum signal to open the secondaries. If not for that change I would still be using the vacuum secs. They raced fine that way. Never had a problem. I am sure the diaphragm can fail, but I suspect it is very unusual.
Carl
I had forgotten you'd hogged out your venturis! It makes sense that you then needed to convert to mechanical secondaries. Speaking of carb issues my daily is having some strange hesitation and self-accelerating issues I've outlined in a new thread to try to solve the issue. This is my shameless plug to try to get you rotary wizards to check it out and lend me you expertise! https://www.rx7club.com/1st-generati.../#post12476823
Hello all! Sorry that I've been AWOL for the last month; life really got the better of me for a little while, and car stuff just couldn't make it on to the to-do list. A small update on Mozu the race car, and a big one too!
The small update 9is I finally wired up the electric fan and the car no longer has ay overheating issues. The Mishimoto 16" slimline fan pushes 1850 CFM and that's more than enough to keep the temps right where they should be.
The bigger new is that I finally acquired a 13B! I found an NA 13B out of an 87 in a pick-your-part yard and scored it complete for $275. Some of y'all responded to my thread about making a 13B out of a 12A, but suffice it to say I don't know what to do next. The engine is well and truly knackered and I'm not sure what parts will be salvageable. But I'm on my way to finally having an 80s IMSA style GTO motor! It'll be a very long term project but I'm stoked to have even gotten to this step! I couldn't borrow the truck, but suffice it to say a 13B fits in the back of a Toyota Sienna minivan pretty well!
The only other new is I'm now trying to head to Willow Springs test and tube on the 17th of September. I'd also like to fit a passenger seat and go to Speed Ventures at Fontana Oct 2 but Idk if that'll work out
if you get the E shaft, and Stat gears you're ok. if you get rotors its a plus. everything else can just be sold off...
I'll take anything I can get! Thats the big if though, the motor is locked up and I have no idea what will be usable.I'll probably makes Frankenstein's motor out of my rebuild needing 12A. Hopefully I'll have ether non wearing assembly parts from the 13B at least.
05-14-21, 03:04 PM
The brap idle was caused by the super rich idle. That just means that I'll get started on gettin a P-port 12a built much sooner than I was initially planning seeing as I don't have a B-port motor to throw in once I move classes to a faster set up as I evolve the car. It's a bummer but in the end I'll be totally fine with the set-up I have. 
