Triple Mikuni thread

[240260280z]

Do plugs indicate lean when it happens?

 

Could it be the distributor and something like a loose wire or the electronic module flaking out?

[madkaw]

99.99% sure it's fuel. haven't pulled the plugs but I'm pretty sure what I will find.

I'm running my MS which turns the pump on and off.

Not sure why it got so bad so there is much to check, but had to walk away for while. 

[madkaw]

Wow, so many different ways to do one task. Been all over looking at triple fuel line routing and it's hard to compare anything. Racetep recommends Carter fuel pump and No regulator. Some run regulator to deadhead, some regulator with return . Some say you have to have a return, others say no.

Then you throw in the variable that everyone's car runs perfect on their set up (whether it does or doesnt). Other variables like what pump they are using .

I think there is something to be said that most FI use a regulator after the injectors and use a return. I think that's the route I'm going .

[gundee]

I ran a fuel pressure test right at each carb with no return line and got 3.5 psi.

I then did the same test with the return line hooked up and got 3.25 psi.

I decided then to leave my return line hooked up. Continuous cool fuel supply that way.

 

This is without  a fuel pressure regulator of course.

Edited August 25, 2015 by lumens

[madkaw]

Time to drive .

[madkaw]

Well it wasn't terrible, but the pressure wasn't stable. At WOT pressure dropped to 2psi. Pressure was also shaky in transitional areas. Upon looking at the numbers on my fuel pump I realized that I had installed (and recommended-sorry) a pump that probably is slightly to small in volume. The rx7 pump was made for a 1.2 liter rotary and requires only 15 gph(2-4psi)

Maybe sufficient for a stock Z with SU'S , but not enough for my engine.

I have ordered a Carter p60504 to replace my pump. It's rated 4psi at 30 gph.

Reading Racetep ' s page they run Carters with 4psi and no regulator on all there set ups.

Waiting on the pump and leaving the pressure gauge in place to see the changes.

I will say that after adjusting my Holley regulator up right to 4 psi the car ran really well- EXCEPT it stumbles in transition sometimes and I can watch the wideband go lean. I'm thinking -hoping - the increased flow with help keep float levels at optimum level to combat my lean issue.

We will see

[gundee]

I am using the Facet 1105 pump. It is a dead on match replacement for the factory pump.

Using no regulator and its working perfect.

 

https://www.pegasusautoracing.com/productdetails.asp?RecID=85

[madkaw]

Looks like about the same specs as the Carter. Is it quiet?

I also went with the carter because it is in line and will package well for my tight space.

[gundee]

It actually sounds to me just like the factory one.

 

I run a stainless Magnaflow muffler and really do not even notice the pump

running while driving.

 

 

 

 

[Kennymonster]

Was doing some googling and came up on this thread again, so I thought I might as well post my updated NA setup/jetting notes for reference (the blow through turbo setup has been sold as of earlier this year, ring went bad on my old block and decided to back to the loud but slow route )

 

Now running: N42 / e88 combo, .480 / 276 cam, Mikuni 44's, .45 pump with 34mm venturis

 

Right when I had cranked the car up after the fresh motor swap running on  open header (back in July?), I retained my previous NA jetting which was

 

62.5 pilot

140 main

190 air

 

With no exhaust, this netted ~13 afr in 4th gear up top, which was great. I haven't bothered with tuning for a while, but it seems after I had finished all the exhaust and new final drive setup, I noticed it had dropped a point or so to 11 to 12 afr under WOT in 4th. Thus the tinkering again last few weekends;

 

After few different combos, I had 130 main and 180 air for a bit, which was reasonably flat except for a spike of 13.5 to 13.8 around 5 to 5.5k, seemed little bit too lean for comfort so I'm currently running 

 

62.5 

135 main

190 air

 

This setup nets 12/13 AFR from 3k to 6k, and dips down to 12 afr at 6.5k. 

 

At this time, I'm tempted to try 200 air to see if I can lean out the 6.5k to 7k range... however from my experience the air jets seldom had predictable effect on the actual curve of the AFR (verified on dyno), often times a very slight change if at all. From what I've gathered going to 37mm will net me that extra 500 rpm but at a sacrifice of low band, and probably will have to rejet everything again. I could also try going back to 130 mains and smaller air (maybe 170's) to try to address that spike, but thinking maybe slightly conservative tune is safer being 9.5:1 now for CR, and running California 91 octane most of the time in racing conditions.

 

My cruise AFR is still a bit rich with the big pilots, it was around 12/13 with the 130 mains, and 11/12 with the 135 mains - I'll be trying 60 pilots later on for the cruise/low range.

[madkaw]

Kenny,

looking at your numbers, not sure why you are trying to dial out a spike above the cam rpm specs. That profile is probably good for 6500, so if it gets a bit rich up there I wouldn't worry much.

If I remember right, the main airs adjust the final AFR by about .5 for every size. 

Also, those are big accel pumps. You are dumping a lot of fuel all at once. So the low afr's might be fuel burning off from the accel dump-heavy Toa layer. I would back off to 40's if you have them.

 

By the way folks, my car running out fuel issue was just that. See thread about Mr.gasket fuel filter

 

 

 

My current set up to date

 

65 pilots 1.5 turns

145 mains

40 accels

200 main airs

 

Third gear WOT is around 13.5

Fourth gets around 12.5

might drop back to 140 mains.

 

I need to move my wideband to other collector to check against first 3 cylinders. #6 dribbles a little fuel which might skew my AFR's.

 

Also I would add that I had a lean issue on first carb that was remedied by sanding down my insolators. The plastic insolator were not completely flat, some warpage and low spots which i believe kept the oring from sealing.

Right now motor is running fantastic.

[Kennymonster]

Yeah I'm just nit picking on the last 500 band I'm working on getting a 4.11 in there soon so probably going to spend more time up there. As for the accel pump, during the pulls I was careful to start around 3k and gradually tip in to minimize the effect, I guess the afr's pretty close to optimal for my setup except for the rich cruise, which I'll back down to 60's once my car is off the jack stands.