I picked this car up for a grand in December, originally deciding to do a swap. The previous owner told me it ran, and he believed that he had the wrong carb for the car, and thought that the proper carb was the one of the two webers sold on racing beat. I don't think that's the case. I wanted to see if I could just get it running without doing a carb or engine swap.

Here are my specs

unknown mileage/year 12a that was streetported (as told by previous owner, no receipts or stamps on engine)
Weber 45 DCOE
MSD 6al ignition
Leading coils are aftermarket
Holly red fuel pump
Holly Fuel Pressure Regulator 1-4 psi
Racing beat headers, not sure what the rest of the exhaust is, no cat.

The problem I'm experiencing is the car dies on wide open throttle. At idle, you can slowly get it to red line, but after 3-4k rpms it backfires rapidly.

I did all of the tune ups. Spark plugs, wires, oil, fuel filters (both), coolant, etc. Did a full tear down, cleaning and rebuild of the carb with the exception of the throttle shaft and plates. I used this video to put it back together:
I verified that all of the passages in the carb were not plugged by using compressed air and carb cleaner

I used a video from the same author to set the float levels:
I changed the jets as well. None have shown any significant changes except an easier and more reliable startup.

My current settings are

Main jet
145 Main jets
200 air correctors
f11 Emulsion tube
45 pump jets (also had a 60, no change)
4.5 Aux Venturis
36mm Venturis
200 seat and needle

Idle jet is supposed to be a 65f9, but I drilled it to see what would happen. After that I thought I needed a richer idle jet and ordered a 65f6. That didn't help, so i went back to my modified one, and it runs better.

The jets as they came on the car were:

190 main
165 air correctors
f11 emulsion tubes
60 pump jets
65f9 idle
4.5 Aux Venturis
40mm Venturis
200 seat and needle

I got to the current jet setup by using this page: Weber 45 Dcoe Carburetor Which states that you start with the main jet value being your venturi size multiplied by 4.

All of the carb changes only helped the car start more easily and reliably.

I verified that the MSD ignition was installed properly using this page: Mazspeed's First Generation Rx-7 Club Page

I also clipped both the red and blue wire underneath the black cap since my msd is a 6al and this is a feature which lets you select your cylinder configuration. The page above claims you need to set it up for a 4 cylinder engine.

I verified that my fuel pump flowed enough fuel by following the specified flow rate in the haynes repair manual. I've replaced both fuel filters, set my fuel pressure regulator to the lowest setting.

The problem here is that I don't think I understand fuel systems enough. My gauge tells me my fuel is at 6psi, but me and my friend tried gravity feeding it with some fuel line and a hopper. The gauge then said it was at 2 psi. It still died on wide open throttle. I'm not even sure if this gauge is accurate, or how this regulator works. I've followed all of the instructions to install it.

I can drive the car, it pulls fairly hard up until 3k RPM, where it bogs and backfires. I can shift, and get up to 3k in the next gear.

I also use premix, I use 1oz of 2 stroke per gallon of fuel.

I've searched up and down this forum, as well as google. I've searched through other car forums for users experiencing the same thing. I work during the day and go to class as well, so I barely have time to call shops around the area and when I do, they have no idea what I'm talking about, are rude, or don't have any experience with carbs or rotaries. I just recently found out Atkins rotary is actually not too far from where I live so I'm going to make time tomorrow morning to call them up and ask if they have any insight.

I'm at a loss. I have three possible conclusions:

The venturi is too large for this engine, and it needs to be smaller.
One of the apex seals are fried.
I'm missing something.

Can anyone help me out here?

Don't be afraid to poke and prod my methods and brain, I'm sure I forgot to list something here.

If you're located in the Puget Sound area in Washington state, I'd be more than happy to compensate you for your time (cash or food) if you want to come over and check it out yourself.

 

welcome to the board.

my thoughts (in no particular order):

1. double-check your timing and wire placement
2. check which module is in the 6AL
3. don't trust the pressure gauge, trust what the car/engine tells you
4. i suppose some may say the 45 is too small, but i have seen them work on 12As
5. what are the plugs telling you?
6. check your compression
7. how is your pump wired?

start with checking those items and see if you get any more pointed direction.

 

I've gotta agree with diabolical1 on this, it really sounds like an ignition timing issue.

 

Thanks for the welcome

Re-did my timing according to the repair manual. Would the haynes repair manual be incorrect on the timing procedure?

How would wire placement affect the engine? Do you mean how things are wired in the bay?

I've been running 8000rpm, tried 7000 and 6000, as well as none. No difference.

Judging by how it made no difference when we gravity fed it vs regular fuel pump I'm guessing it's not a fuel issue. It could still be my float levels.

I've searched DCOE on the forums, and I get tons of results from people running the same carb on engines they've streetported themselves. And the thing is, if a carb is too small or large, then it's a matter of CFM of air that the carb can flow, and what the engine needs, right?

Totally forgot to check this! I will tomorrow morning.

I've done the "Whoosh" test and it's consistent. Could I use a regular engine compression tool?

What do you mean by this? My pump works correctly.

A small update: I ordered some 28mm chokes to see how the engine would react on an extreme end. They came in today and I popped them in, and my engine doesn't die anymore! It stumbles, but doesn't die. It's night time so I can't disturb my neighbors. I'll test it in the morning.

I also ordered a wideband so I'll be getting that on friday.