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I'm looking for a Weber carb guru to ask a few questions about my 13B blow-through setup that I am trying to finish up. I was previously working with a local shop, but for reasons I won’t mention here, I am in need of alternative assistance.
The engine is a S5 13BT utilizing an upgraded BNR turbo, and a turbo prepped Weber. Fuel system is a stock 20B pump, and a Mallory 4390 fpr. Ignition is provided by a distributor, a single FC leading coil, and two MSD Digital 6-Plus.
Besides what’s listed above, I know very little about what else is required to get this engine running. I do not have previous knowledge or experience with carburetors. That said, I am very interested, and willing to learn. I have a good amount of time, and money already invested in this project so I’d like to see it through before just going to efi which is something I’m personally more familiar with.
The main points I’m focusing on right now are:
What fuel filters should I be running?
How the heck does this ignition system work?
I’d appreciate any support or advice y’all can impart.
What fuel filters should I be running?
How the heck does this ignition system work?
Regards,
Edward
for the fuel filter, i'm not sure what fuel pressure you're going to end up with, but if its less than 10psi, the stock filter is fine. if you're running more, i would suggest an EFI style filter, or at least a metal body filter (if you look up a filter for a 79-81 Rx7, the parts store will have a metal one that fits)
no sure how your ignition system works! i can see for the leading, the distributor would/could trigger the MSD box, which fires the FC coil to the leading plugs, this part is good. not sure how your trailing is set up, but it should go through the cap, and should have its own coil. the MSD box is ok, but probably overkill.
Also make sure that your return line is properly sized. I have heard that running a fuel injection style of pump (20B) in a return system at very low pressures is not ideal for the pump or the setup. What year is your car? The GSL-SE's came with a larger return line. Most FB's I think just have a tiny 0.25" return line that can't flow enough. With a small return line your fuel pressure will be way too high.
You want to make sure your return line can handle the flow, especially I bet that 20B high pressure pump will want to flow a lot of fuel, and for your carb you will need to regulate it down to only 4PSI.
Have you seen others having long term success running a 20B pump for a carb'd application?
I would also look into a much higher flow capacity fuel filter. Any non-stock fuel pump you run with a return setup will want to flow a lot of fuel. I made this mistake on my setup and initially used a fuel filter meant for a "post fuel press regulator" location, where fuel flow is a lot less (only what the engine burns...).
I think you will want a higher capacity "pre pump" style of filter.
I would also look into a much higher flow capacity fuel filter. .
i did some fuel system testing recently, and the stock fuel filter had no trouble flowing 1500cc/ 30 seconds, which is a LOT.
my concern with the stock carb filter is that, being plastic, probably can't handle pressure over say 10psi (stock is 2.75), so higher pressure would warrant an EFI style filter
So I didn't specify in my original post, but the car is a 2nd gen race car. I went out to the garage to look at it again (probably had been about 6 months since I had even looked at it) and verified a few things.
It has a FC trailing coil, (NOT a leading coil).
There's a stock 2nd gen fuel filter.
The distributor is locked.
As the car is a FC, (previously running an EFI engine) all of the fuel lines under the car are OEM.
First thing I want to address is the ignition system, I had done some searching here on the forum and had previously thought my engine builder might have set me up with a 2GCDFIS, but as I verified that the coil is a trailing and not a leading, this can't be the case. So I did some more searching and found a few pictures of setups that are supposed to be similar to mine.
Would be nice to be able to edit my original post, but I'll just post the pictures below.
First up are pictures of my car as it sat several months ago:
Secondly, here is a picture of a setup that my car was patterned after (same engine builder):
Looks like Rob from rotaryshack was working on it. Why didn't he finish the job?
My suggestion is to take it to a shop and just pay them to get it running. Hit up eddyrenown on Instagram he does all my builds and understands carbs setups.
Looks like Rob from rotaryshack was working on it. Why didn't he finish the job?
My suggestion is to take it to a shop and just pay them to get it running. Hit up eddyrenown on Instagram he does all my builds and understands carbs setups.
I'm not against taking the car to a shop, but it's definitely my last resort. Especially given that I'll be racing the car without track support, I want to learn as much as possible about how this engine setup works.
Prior to this build I had never looked at a distributor or taken the time to learn how they work. I did some research and believe I might be on the right track.
Any idea why the engine builder would have used this setup?
because you bought it? the FC coils are big, reliable and cheap. strong ignition is good, hence the MSD boxes, although i'm not sure why you have the DIS4's instead of the 6AL, the DIS4's are expensive, no?
because you bought it? the FC coils are big, reliable and cheap. strong ignition is good, hence the MSD boxes, although i'm not sure why you have the DIS4's instead of the 6AL, the DIS4's are expensive, no?
Hell yeah they were expensive! At the time of purchase I was just blindly buying what I was told to buy the engine builder, lol, my fault for not knowning what’s what. My real question was why I was set up with this standard type of ignition system, instead of a “direct fire” type. Does this conventional type of ignition offer any advantage over direct fire?
Also, if you have a minute, could you please look at my video and tell me if I’m on the right track?
because you bought it? the FC coils are big, reliable and cheap. strong ignition is good, hence the MSD boxes, although i'm not sure why you have the DIS4's instead of the 6AL, the DIS4's are expensive, no?
Btw, they're not DIS-4, but Digital-6 Plus. Not sure why I have these rather than the cheaper model though.
