Triple Mikuni thread

[LeonV]

Good point guys. Honestly, I didn't think my wrap job would do anymore then keep the extreme heat from the header away from the bottom of the intake and keep the fuel charge a bit cooler. The wrap is only on the bottom half of each runner, and I believe there will still be plenty of heat in the intake.

I also thought I have searched and found guys that have run a heat shield all the way up against the head, so this would be different?

I would also consider the length of my intake runners-2"- maybe. Now how long are the VW runners. Just think how far the Mikuni pumps spray fuel-direct injection!! Not sure if any pooling is going to happen on this intake.

I was actually worried more about heat transfer from the intake to the carbs.

Besides-you know how long it took to make those weird patterns to wrap around that intake-they're staying-

Not saying that you'll get pooling, but what you will have is a tau layer. The tau layer gets bigger as runner temp drops. This necessitates enriching the mixture.

As far as heat transfer to the carbs from the intake, do the Mikunis not have an insulator between the intake and carbs? This is pretty universal in the carb world.

[madkaw]

Two good days and I got my new rear main seal in and got my motor back in the car. Things really couldn't have gone much better----or could they.

I in stalled pilot air jets-#60's in my Mikuni's and it really didn't help much. THe car would start great using the starter(enrichnent) engaged, but wouldn't idle or run worth a dam without it.

I started it up and BOOM, rock steady idle around 1500rpm, no spittting, sputterring, coughing, just smooth great sound-but my AFR wouldn't hardly come off 18. Now if I blip the throttle the car revs up nicely--atleast I got the accelerator pumps working good--the wideband will finally come off 18 and drops briefly into the 14 range.

I ran a range of adjustments on my NEW pilot screws with no avail. It acts like there is not nearly enough fuel for primary functions. I did get the engine up to temp and pulled a spark plug and it was colorless. I had cleaned the plugs during all this work and they looked new before this start up. Well they still looked new and showed no color.

Pilot air jets need to be bigger yet because of my vacuum log

[madkaw]

Well I see it's been a week since I posted, so I will update. Talked to Todd and he sent me 62.5's and 65's for the pilot jets. Meanwhile I took all vacuum possibilities out of the equation by removing my vacuum log and any else vacuum. Todd once again was a bit adamit about just getting out and driving the car to shake it down. I told him I see no possible way it is coming out of the garage running like this-falling on it's face.

Todd did get me the jets in quick fashion as he always does, he really does do a great job of doing business!

I threw in the larger jets(65's) right off the bat thinking I was way small anyway, but they didn't make a large impact. Still wouldn't even idle at 1 turn out on the pilot, it took more like 2 and it would still fall on it's face about the same rpm. So now I'm really wondering what's going on. How much am I going to ahve invested in jets before I get this right?

So with nothing else much to try I looked at my jet collection and realized I had a set of larger main air jets that came with the carbs-200 main airs. I'm desperate so I throw them in and what do you know, it was much better. The stumble now moved up the rpm band by almost double and it wouldn't fall as hard on it's face. Logically, I don't know what I've done, since I thought the main air jets were not part of this equation-or are they.

I will say that one of the brief moments my O2 sensor was working it looked like the idle AFR was between 12-13,( with the 65's) but the damn thing is so flakey I don't know if I trust it. It's another thing to throw money at I guess.

I'm kind of missing my SU's right now

[Zedyone_kenobi]

I wish there was a correlation between Webers and Mikuni's. Right now I have just about got my WEbers running perfectly. Still not happy with my linkage from the pedal to the throttle lever, but other than that, I am a jet away from dead nuts on. If there was a comparison chart we could cross reference. But the variables are so infinitely diverse, then it may be impossible.

[madkaw]

This might be old news to those of you that play on Hybridz, but I , or should I say Todd, figured out my issue. My CAI box backing plate was covering up the float bowl vents, so it was cutting off the fuel to the carbs.

I drove her today and she drove alright. My jetting is still off.

Right now I have

200 main air jet

60's pilots

140 mains

When my O2 sensor was working it showed

14.5 at cruise and sounded great

13+ at idle, but the O2 sensor is more erratic at idle

WOT I was 16+-waaayyy to lean

On the horn with Todd now.

Pic of my CAI that is almost finished except for a good polish. Todd very much liked the CAI and it's got him thinking

[Travel'n Man]

Very "cool" cold air intake box!

[madkaw]

Beautiful day here in Bloomington Indiana-high 70's and not much humidity

Current set up is;

pilots are 62.5's at 1.5 turns out. The engine is happiest at this point. NO hesitation or bobbles and AFR's hovering around 14. The engine idles best here and restarts the easiest. The 65's semed too rich and made my wideband go crazy-whic is usually an indication that my mixture is taking big swings.

Main jets are 155 and main air are 180. Since my O2 doesn't like big swings it is a bit more difficult to diagnose the main side. Plenty of power, but maybe more is available.

Accelerator pumps; went back with the 40's and the engine likes it. There is no bobble when bipping the throttle or heavy tip-in. With the 47's the engine sounded like it was drowning in fuel.

Back to more R&D

[steve91tt]

Great news! Sounds like you are starting to enjoy the Mikuni goodness.

[madkaw]

I thought I would show what I did for making the fuel enrichments work on my Mikuni's. Most people probably disconnect this system and it is probably wise if you are racing your car. It does make starting the engine very easy.

It's just a simple cable pull on the enrichment levers that has two settings-full rich and half rich. You pull the levers to open the enrichment and turn the key, no pumping the gas-infact the manual says not to pump the gas or even touch the throttle. It has worked for me without a flaw. It brings the car to a high idle with the right mixture to keep the engine running. It doesn't seem to dump a lot of fuel in there either-according to my spastic O2 gauge.

I didn't get any cable or linkage with the carbs so I went down to the local Autozone and picked up a choke cable kit. It worked out well using the existing hole from the stock choke cables. As far as mounting the pull knob-I always wondered what I would mount in that open space on my dash

[surfer.tech]

^ is that the choke?

[madkaw]

Basically!

[Zedyone_kenobi]

That is quite nifty! I like the innovation there buddy.