PinkRacer

*Also posted in 1st Gen Forum*

I did a search, but came up with a bunch of different ideas, and I'm wondering if someone has a concrete answer.

We have a 13B 6-Port from a 1990 RX7 (S5) that we're putting in our race chassis to finish out the season (race car is an '86). Engine is completely stock, no porting done to it whatsoever. Car has RB header and full RB dual exhaust.

Car is all set up for carbed set-up with a proper fuel pump, pressure regulator, etc.

I have 2 carbs at my disposal: a 45DCOE with Racing Beat manifold (where the top half hooks on the OEM lower half), and I have a 51IDA with Racing Beat Manifold (built for our full Bridge 13B 4-port -- WAAAAAAAAAAY too big).

I would like to put the 45DCOE on the stock junkyard engine we're putting in the car while the race engine gets fixed up. I have a variety of jets and things at my disposal. The carb has 40mm chokes in it right now and a 300 needle valve (I also have a 225 at my disposal). I have F8, 11 and 16 e-tubes.

What would be a good jetting set-up for this application? Just needs to get us through a couple race events.

Main:
Air:
Idle:
E-tube:
Acc. Pump Jet:

j9fd3s

iTrader: (3)

here's my $2...

start with the idle fuel and then idle air, if you do it without the main jet stack in the carb, you can isolate each jet/air/em tube, which takes the "magic". out of tuning the carb. a wideband O2 speeds things up.

i listed these in the order to tune em. hopefully you have enough pieces around that this isn't a $1000 carb...

needle; use the 300. fuel pressure? somewhere between 3.5 - 4.5

chokes; 40 is probably on the small side, it'll have good midrange. probably work really well with the stock engine and quiet exhaust

idle jet: seems like a 65 is a good start, 60 or 70 might work too, depends on what you have around.

idle jet holder/air; the IDA's come with a 120 hole and it does seem like a 100 is better. on the IDA its simple to solder shut and drill as needed. i know the dcoe its in the jet

E tube; i would start with the F8. after you get the main jet and air, go back and try different ones

main jet; you will probably be in the 180-200 range.

main air, i'd start with the smallest you have, 130 is in the ball park, once the main jet is right, then play with the airs.

PinkRacer

Thanks for the starting point! We got the engine in last night and running, started up 2nd time turning over. Not bad for an engine that has sat for at least 2 years in a parts car, and has over 183,000 miles on it!

I have dual O2 sensors to a custom gauge package, so it gives me an idea of where we're at ratio-wise.

I have a 190 main and 210 air in it right now. I'm going to take down the air jet a bit. I have a 65 idle in it, but it seems to be running really rich at idle, so I may lean that out a bit.

I have F11 e-tubes in it right now, but I'll give the F8's a try. Just takes a little trial and error.

j9fd3s

iTrader: (3)

yes basically, thats the magic. if you separate each jet/air/em tube's function, then it really is just trial and error.

try setting the idle timing around TDC, and you should be able to get it to idle in the high 12's low 13's

Craiger

iTrader: (1)

Hey, I have been helping ToySport with this project.

Unfortunately, their timing has no vaccum advance, so we have to set the timing around 20-25 BTDC for wide open throttle. There is very limited options for the timing that they'll be running. We didn't hook up the timing light last weekend when we ran it for a few minutes, but we'll likely look at this next time we work on it.

When we ran it last weekend, it sounded like it was idling richer than 10.0:1 AFR, with the idle at about 1200RPM. We'll probably leave the idle speed around there, and just lean out the mixture.

Hopefully we'll get at it again this weekend and see what we can come up with.

Craig

j9fd3s

iTrader: (3)

take the main stack jet assembly out, and go drive the car. it becomes really obvious what the idle jets do. i'd say try all the idle jets you have, or at least the biggest and smallest.

then put the mains back in, with the richest e tube, and smallest air, and play with the main fuel jet. the etube controls how fast/slow the main jet starts working, and the air is similar, so get the AFR close, and then if you need to fix any lean spots or rich spots use the air or e tube as needed.

the main jet test is kind of fun, go drive it, put it in 4th@1000rpm, floor it and watch the wideband. you should see a lean spike, then it'll go rich from the accelerator pump shot, and then its running ONLY from the main jet.

i've been tuning my P port like this, and its taken FOREVER, but there really isn't a better way. i have gotten the p port to idle @1000, run 14.5:1 afr cruising, and be pretty tame all around...