Jeff20B

So I'll need at least 50 GPH for 450 HP at 6.1 PSI, is what I'm understanding. A single carb is prefered.



I used 3/8" line on the 20B at stock rail pressure of 43.5 PSI, and it flows like Niagra Falls, but since this project is carbed, should I use 1/2" line? I think I'd prefer 3/8" now that I think about it (easier to bend, easier to find locally etc).



The Carter 100GPH pump comes with 1/2" fittings and should handle 1/2" hardline just fine. The 72GPH pump has 3/8" fittings. I have both of these pumps sitting here. I also have the Holley 4.5 to 9 PSI (dual outlet) pressure reg. Which pump should I use?



The only things missing at this point are the fuel cell and hardline.



Having access to both pumps at the moment, should I err on the side of abundancy and go with the 100GPH unit? We'll definitely get a fuel cell. So how about 3/8" line for easier installation?



Still worried about 3/8" line at 6PSI though...



Oh, Lynn, this is the type of carbs I want to get for this project. IDA http://www.racingbeat.com/resultset....rtNumber=16601

Jeff20B

Just need to correct something above. In the second sentence where I said a single carb is prefered, it is incorrect. A single fuel pump is prefered.

Lynn E. Hanover

This is a 13B, or 20B?



450 HP from a carbed 13B may be a bit hopefull. The problem is that even through a large needle seat set there is a limit to how much fuel you can get into the float bowl at even 6 PSI. You could rig up a test for total fuel flow using water. Sit the carb with the float blocked in the lower range, over a bucket.

Pressurize a strong container of water to 4 or 5 PSI to replicate fuel pressure.



Get out the stop watch and turn on a valve to allow water to flow through the carb. Can you get close to 45 or 50 GPM?



This is where injection really starts to shine. With 45 to 100 PSI of fuel pressure, there just is no limit to the HP it can support. Need more fuel? add more injectors.



Lynn E. Hanover

Jeff20B

It will be a peripheral port 4 rotor based on 12A parts with two Weber 48mm IDAs. Racing Beat says a proper 12A (2 rotor) peripheral port will make around 270HP peak at rather high RPM. We don't need that kind of peaky power. We'd prefer a more streetable smaller peripheral port; somewhere closer to around 400-450HP (200-225HP per 2 rotors) with a max RPM of around 8k.



I know, I know, what's the point in going peripheral if you don't wind it up there... Well, the NSU engines had small peripheral ports and peaked at 7k. With 4 rotors and small ports, I think this engine will be able to do 400-450HP and keep it below 8k.



We could get away with slightly more muffling than the big p-port guys making driving it on the street closer to reality. The owner already has a track-only race car so he was looking at making this for the street. I am working toward that goal. I just need to know which diameter hardline to use and which model Carter pump to install.

j9fd3s

i dont see how you could go wrong by going too big....

Jeff20B

Thanks to a confirmation from Evil Aviator, yes 1/2" hardline is the correct diameter to use when going carbed at these power levels. If it was fuel injected, 3/8" would have been ok.

Lynn E. Hanover

I ran a Carter pulling from each rear corner of the cell and then joined those lines into another single carter to run 14 pounds of pressure to the regulator, to get it back down to 6 PSI. I found that I didn't need the third pump so long as I installed new Carters for each season. It could squirt fuel over the roof of my house, so I figured that would be enough. It would probably work fine for you as well. It won't hurt a thing to use 1/2" ID fuel line up to the engine. It is just more difficult to string it out and make it look good. I see no actual advantage over it once the ID of the hose is close to the ID of the pump outlet fitting.



That is one interesting project. A real well built 12A Pport can do 310 HP but it needs to be well over 10,000 RPM. The 400 HP at 8,000 should be a piece of cake. I have enough pieces left to build maybe two more of them.



Lynn E. Hanover

j9fd3s

thats a funny mental picture.....



it would be funny to write the manual for that.



"the fuel delivery pipe should be aimed at approximately 70-80 degrees from horizontal. with the fuel pump on the stream should go well over a house that is 60' deep and 45' tall, if not then replace the pump"



mazda would include a graph of delivery pipe angle vs distance

Jeff20B

My original estimate was 400hp at 8k. Sammy at MarvelSpeed quoted 425 to 450hp if I used his ports. Evil Aviator figures power levels will be up to that level as well. Now you've chimed in with your positive outlook too. I'm as confident in this project as I was with the 20B, which worked out as expected. Now all that's left is to do it to it.



Lynn, you should build yourself a 4 rotor. I can offer details on the parts I'm using. Maybe we can swap ideas.