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Lighter = Faster (RX-7 Build #2)

mymmeryloss

minitrucker
:
13bT Mazda B2600i
Im so jealous. I can't wait to drive mine. After hearing your battery issue while attempting to start, I think imma have to give it a shot again myself.
 
:
'86 RX-7 Base, '79 RX-7 GS
Im so jealous. I can't wait to drive mine. After hearing your battery issue while attempting to start, I think imma have to give it a shot again myself.
I broke down and bought a new battery. I went with the same size and CCA since it's only $80. Fortunately, the last three times I've started the car it's fired right up after 2-3 seconds of cranking and that's without putting the battery on a charger between runs. It appears 340 CCA is enough after all.

I'd also check your wiring harness. Make sure your coils and injectors are wired properly. The best way is to check for continuity between the pin in the coil/injector connectors and the appropriate pin on the ECU connector. Including my own, I know of several cases where there were errors in LMS-EFI-made harnesses.
 
:
'86 RX-7 Base, '79 RX-7 GS
Made a youtube channel exclusively to upload my RX7 videos:

<iframe width="480" height="270" src="https://www.youtube.com/embed/k388GoFvSl0" frameborder="0" allowfullscreen></iframe>

<iframe width="480" height="270" src="https://www.youtube.com/embed/xV4jqEjA4VY" frameborder="0" allowfullscreen></iframe>
 
:
'86 RX-7 Base, '79 RX-7 GS
Passed 100 miles on the break-in a couple days ago and am nearing 150 now. It's definitely starting to idle/cruise a little smoother now. Generally keeping engine speeds below 5000 RPM and I don't think I've done more than 30% throttle. Overall it's driving well. Moderate throttle changes are smooth and generally it operates within 12-14:1 air:fuel ratios. Idle wants to be around 13:1 but it appears it will cruise happily upwards of 15:1. Starting from a stop and large transients are both still issues...

I wish I had a better way of capturing its sound. It's got a good, low rumble with a hint of "brap" at idle but it definitely has that pissed-off-chainsaw rotary sound at 5000 RPM.
 
:
'86 RX-7 Base, '79 RX-7 GS
I'm over 300 miles now. I can't wait until I hit 1,000 miles and start incrementally increasing engine speed: 6,000 RPM at 1,000 miles, 7,000 RPM at 1,333, and so on up to 9,000 RPM at 2,000 miles. I may ultimately go higher than that. It depends on where the car stops making power. Hopefully it's less than 10,000 RPM...

I had a well-respected rotary tuner stop by the house today and we got the tune switched over from alpha-n (throttle position) to MAP. It's running SO much better now although the transient throttle isn't completely squared away. He managed to get some more efficiency out of the engine because now it's idling at 1,300 RPM at the same throttle position as it was before when I had it idling at 1,000 RPM. It's SO nice to not stall out at every stop and have to baby the throttle when starting again.
 
:
'86 RX-7 Base, '79 RX-7 GS
Trying a different image hosting service. Let's see if this works. I made some small changes. First I swapped in an underdrive alternator pulley.



It doesn't really need to be underdriven but I didn't like that my other one had a different belt spacing. I was afraid that would lead to excessive wear that could cause a failure at some point. I've also been playing around with the MAP sensor placement. I've got it about as high as possible in the engine bay.



Somehow, I'm getting a lot of reversion in the intake system. Even though the vacuum manifold is well above the ports on the intake I'm still getting fuel/oil in the vacuum lines. So far the little inline filters and check valve is keeping that out of the fuel regulator, MAP sensor, and brake booster but at some point I'm going to need to find a better way. I'm thinking about rigging up a filter that usually intended for air tools. Kind of like a catch can for the vacuum system.

I'm up to about 600 miles now. Work has been crazy, which is keeping me from driving my usual ~25 miles a day. I'm still struggling with transient throttle lean events but it's driveable. On the other hand it also wants to flood during quick on/off throttle events like hitting a large bump in the road. The next major milestone is 1000 miles when I get to change the oil again (going with 10W30 this time) and I get to start pushing it beyond 5000 RPM. The plan is still to limp through the rest of this year and the Winter to get to 2000 miles before I take it to be finally tuned.
 

Lewis7789

Evan aka "Lady Hands"
Contributor
:
1995 MX-5, 2006 MZ5, 2001 Yamaha R1
Pictures are working and everything is looking good. Have you really only went up to 5k rpm? I would be soooo tempted to just run it up at wot a couple times...
 
:
'86 RX-7 Base, '79 RX-7 GS
Pictures are working and everything is looking good. Have you really only went up to 5k rpm? I would be soooo tempted to just run it up at wot a couple times...
I think I've hit 6000 RPM once in 1st gear when I wasn't paying attention and I know I've crept slightly above 5000 from time to time. Conventional rotary wisdom appears to indicate 1000 miles for break in, keeping engine speed below 4000 RPM until 500 miles, and then slowly increasing to redline by 1000 RPM. Since my bearings were also new the recommended advice is to double the break-in time. Obviously I haven't followed this to the letter but it's better to be safe than sorry. So far I'm up to 600 miles. Once I hit 1000 miles I'll change the oil again and start going up to 6000 RPM. I'm slowly collecting a list of things to do/address:

1. Transient lean/rich conditions. The car is still going lean immediately after a large/quick throttle movement. The fuel catches up about a second later and then goes rich. Unfortunately this then causes issues during quick open-close throttle events like being stuck in traffic and hitting a large bump in the road, or blipping the throttle in neutral. I've managed to flood the engine a number of times this way.

2. Leaking water pump. It's leaking from the weep hole. I have a replacement. I've just been lazy as it's an annoying job to do. Despite the mess, it doesn't appear to have lost any appreciable amount of water.

3. Noisy transmission. I'm getting a good amount of bearing noise in neutral with the clutch engaged (pedal out). I'm pretty sure this means the input bearing is dying. I get similar noise in 4th gear, which I think is the same symptom. New bearings have been ordered. I'll probably get around to this and the water pump over the Winter.

I realized I don't have any decent shots of the car in its finished form. I took a couple crappy pics in the garage last night.



 
:
'86 RX-7 Base, '79 RX-7 GS
Damn that thing is bright! Looks killer
Thanks, the fluorescent lighting makes it appear lighter than it really is. Someone pointed out it looks like Tennessee orange and that's definitely not the case.

Temperatures are dropping and that's making it harder to get out and drive the car. Ambient temperatures are in the 40's and I'm having a hard time keeping the oil temperature up. It will drop below 140 while cruising making it hard to keep the car "warmed up." Up to 675 miles and playing the the transient throttle settings. I think I may have figured out how to speed up the fuel response. It has to do with the split between synchronous and asynchronous enrichment. I think I need more asynchronous injection as both a percentage of the total enrichment and maintain some at higher engine speeds.
 

chuyler1

goes to eleven
Moderator
:
2013 CX-9



Somehow, I'm getting a lot of reversion in the intake system. Even though the vacuum manifold is well above the ports on the intake I'm still getting fuel/oil in the vacuum lines. So far the little inline filters and check valve is keeping that out of the fuel regulator, MAP sensor, and brake booster but at some point I'm going to need to find a better way. I'm thinking about rigging up a filter that usually intended for air tools. Kind of like a catch can for the vacuum system.
Figured I would come over here and see how your build was going. Didn’t realize how similar our builds were! Your setup is exactly what I’m considering for my FB (if I ever finish the REPU).

I tried to research the fuel in the vacuum line issue but couldn’t come up with any suggestions other than possibly a leaking FPR. I don’t have a vacuum line on mine and yours looks brand new too so i doubt that is an issue.

The only thing I can think of is that it is simply related to the pulses of the rotors allowing a small amount of gassy air to pass between the two intake runners via the vacuum manifold, and from there, the gas can eventually condense in areas that won’t dribble back down to the intake. In your case, maybe tilting the two lines to the MAP and FPR upward so any liquid will always roll back into the manifold, and then back down into the intake. I can’t tell if those hoses always maintain an upward path but if they don’t, give that a try and check back after a few hundred miles to see if the amount of fuel left over has improved. Another option could be to only take vacuum readings from a single throttle body. On my truck, the brake booster was only connected to the rear rotor secondary port. On the later gen RX7s, I believe vacuum is read before the separate runners split so you don’t have a situation where gas filled air can move between runners.
 
:
'86 RX-7 Base, '79 RX-7 GS
Figured I would come over here and see how your build was going. Didn’t realize how similar our builds were! Your setup is exactly what I’m considering for my FB (if I ever finish the REPU).

I tried to research the fuel in the vacuum line issue but couldn’t come up with any suggestions other than possibly a leaking FPR. I don’t have a vacuum line on mine and yours looks brand new too so i doubt that is an issue.

The only thing I can think of is that it is simply related to the pulses of the rotors allowing a small amount of gassy air to pass between the two intake runners via the vacuum manifold, and from there, the gas can eventually condense in areas that won’t dribble back down to the intake. In your case, maybe tilting the two lines to the MAP and FPR upward so any liquid will always roll back into the manifold, and then back down into the intake. I can’t tell if those hoses always maintain an upward path but if they don’t, give that a try and check back after a few hundred miles to see if the amount of fuel left over has improved. Another option could be to only take vacuum readings from a single throttle body. On my truck, the brake booster was only connected to the rear rotor secondary port. On the later gen RX7s, I believe vacuum is read before the separate runners split so you don’t have a situation where gas filled air can move between runners.
I too thought that it might be the FPR since there is significantly less in the MAP sensor line. However, the line after the filter is dry so it's definitely coming from the engine side. It's hard to tell but the vacuum lines all have at least a slight upward angle to them. I'm going to mess with them a little more when I replace the filters in the near future. I'll have to try the single throttle source. Use one for the brake booster and the other for the FPR and MAP. I had just assumed I would have an unstable vacuum single off a single rotor. If anything, it would be interesting to see if I'm getting different numbers from each rotor.
 

chuyler1

goes to eleven
Moderator
:
2013 CX-9
If you are trying to do a VE tune instead of TPS you will need the Map connected to both. No way around that, however the brake booster and FPR aren’t as sensitive to that. I say, get it dialed in, drain the hoses, then rev the piss out of the motor and cut the ignition every time you shut it off. That should help clear out the lines and ensure fuel isn’t resting in the intake.
 
:
'86 RX-7 Base, '79 RX-7 GS
If you are trying to do a VE tune instead of TPS you will need the Map connected to both. No way around that, however the brake booster and FPR aren’t as sensitive to that. I say, get it dialed in, drain the hoses, then rev the piss out of the motor and cut the ignition every time you shut it off. That should help clear out the lines and ensure fuel isn’t resting in the intake.
Yeah, this is what I was just thinking. I'm tuning by VE with a MAP reference. The Haltech actually can tune by VE with TPS as well but I'm not doing that anymore. If the MAP sensor is getting a signal from both rotors then the FPR and brake booster are a part of that same system even if they are only drawing from, say, the rear rotor. No matter what both throttle bodies will be connected via the MAP sensor lines.

I don't know if it's related or not but my crankcase vent was plugged for the first 600 miles. I don't have any kind of forced evacuation system. It's just a catch can connected to the oil filler tube via some fuel line, which was blocked with a plug I had put in place when I pulled the motor back in August. Apparently I forgot to take it out.
 

chuyler1

goes to eleven
Moderator
:
2013 CX-9
I haven’t done anything about crank case pressure either. I had planned to use vacuum to pull it out, but would need yet another port separate from everything else...otherwise dirty crank case air is gonna dirty up all the vacuum lines I have. Maybe I will work on something when I get a real catch can installed.
 
:
'86 RX-7 Base, '79 RX-7 GS
I haven’t done anything about crank case pressure either. I had planned to use vacuum to pull it out, but would need yet another port separate from everything else...otherwise dirty crank case air is gonna dirty up all the vacuum lines I have. Maybe I will work on something when I get a real catch can installed.
What do you have right now - just an open port on the center iron or oil filler tube? I've thought about trying to rig up a PCV system as well, but like you said it would require extra ports separate from the vacuum system. I mainly want to do this so I can reincorporate a charcoal canister into my system again so the garage doesn't reek of fuel all the time.

I've been thinking about the fuel in the vacuum lines things and I'm wondering if injector firing angle has something to do with it. Haltech defines injector firing angle as the angle at which the injector will shut after the injection even has occurred relative to a full camshaft revolution. I'm wondering if my angles are off and I'm keeping the injectors open too long so fuel is bouncing off a closed port.
 

chuyler1

goes to eleven
Moderator
:
2013 CX-9
For PCV, my REPU service manual shows the basic diagram. A check valve on the lower intake manifold sucks air via vacuum at all times, introducing that dirty air below the carburetor. It sucks from the oil filler neck and can also suck gas fumes from the gas tank. The lower port on the center iron attaches to the charcoal canister so when vacuum is sucking, a small amount of air is constantly pulled from the canister so there is never positive pressure in the crank case, it’s always negative. When the vehicle turns off, gas fumes from the whole system that expand/contract with temperature changes are fed through the charcoal.



Not sure how the later models handled this since I haven’t studied the workshop manuals as thoroughly.

As far as injector timing goes, that’s something I haven’t messed with yet but i definitely think you’re on to something. There must be calculations you can make to measure length between intake port and injector but my guess is that it’s something you just have to experiment with until the idle smooths out. At higher RPMs I doubt it matters all that much unless you are after every last fraction of horse power.
 
:
'86 RX-7 Base, '79 RX-7 GS
That's similar to the later models although a little less complex. On the FC I there's still a check valve on the line between the center iron and the charcoal canister that's tee'd into the intake tract after the airflow meter but there's also a "purge control valve." It looks like a check valve but has three ports: one connected to the oil filler tube and the others are connected to the intake with one right before and one right after the throttle body. It opens when the post TB pressure approaches the pre TB pressure so it isn't always drawing in crankcase/charcoal canister gases. It looks like it takes the place of the "ventilation valve" in the diagram you posted. Check out page 70 here: http://www.wright-here.net/files/manuals/1989 RX-7 FSM/F1_Fuel_and_Emission_NA.pdf.

I could make this system work on my setup. The simplest way I see would involve tee'ing the charcoal canister and center iron port/oil filler tube into a catch can with a small filter and then running a line from the catch can to the purge control valve. The other two ports on the purge control valve would then be connected to a new port in one of my air filters and one in my vacuum block. The catch can would collect the heavy oil vapor from the crankcase/charcoal canister, the small filter allows for an air supply and the purge control valve should perform as intended. The biggest caveat is assuming I can figure out the fuel-in-vacuum-lines issue.

There are calculations you can do and whether or not you want closed port or open port injection based on when the intake ports open and close. My understanding is the improvement is best felt at idle and lower engine speeds. People have commented as having a smoother idle, more responsive throttle, and less fumes. All of which are things I'd like to improve. From what I've read this is usually one of the last things to work out in a tune since the overall impact is small (<0.5 change in air-fuel ratios). Basically, it sounds like you adjust the angle until the air-fuel ratio is the richest for that engine speed. This represents the most amount of fuel the engine can take in and combust for that situation. It looks like there will be two angles for which this condition will occur: one for open port injection and one for closed port injection.
 

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