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Triple Mikuni - Info Thread


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I thought it would be a great idea to start a on-going community thread on Triple Mikuni's. A place where new users and active users ( with years of knowledge ;) ) could get/give detailed breakdowns / photos / and tuning configurations for 40 / 44 phh's.

 

When I switched over from SU's, I really had no clue on what things were and how to configure them for my current setup. I would have to say that it's some what a pain to get solid information out on the web in one location or be able to find a detailed manual for specific needs. So I thought I would start this out by taking a couple photos and labeling the main pieces for tuning.

 

DISCLAIMER: I am by no means an experienced carb tuner in any way ( that's why Wolf Creek is around ;) ), mainly looking to get the topic started. It would be great if you guys could give suggestions or show off your setups and tuning info. Any suggestions for diagrams / photos labeling, let me know and ill make them.

 

mikuni_40phh_01.jpg

mikuni_40phh_02.jpg

mikuni_40phh_03.jpg

 

Based on the info I've read...

 

Factory setting for 40's are:

Main Jet 140

Main Air Jet 180

Pilot Jet 57.5

Pilot Air Jet (fixed) 140

Outer Venturi 32

Inner Venturi 12-16

Throttle Plate #165

Jet Block Assembly 5.8 - (6x2.5 & 4x1.5)

Bleed Pipe T

Fuel Needle & seat 1.5

Pump Jet 40

Idle Mixture/Pilot Screw 1.0 turns

 

Factory setting for 44's are:

Main Jet 150

Main Air Jet 200

Pilot Jet 57.5

Pilot Air Jet (fixed) 120

Outer Venturi 342

Inner Venturi 10.5-14

Throttle Plate #175

Jet Block Assembly OA

Bleed Pipe n/a

Fuel Needle & seat 1.8

Pump Jet 40

Idle Mixture/Pilot Screw 1 1/8 turns

 

Original Manual:

http://www.scribd.com/doc/60490072/Mikuni-PHH-Service-Manual

 

-------

 

Q & A Section: ( help me grow this list )

 

What fuel pressure do you run?

( based on info read 3.5 - 3.7 psi standard applications )

 

What jets do you run for an L24/L26/L28?

Mild Cam:

??

Hot Cam:

??

 

What is the timing?

Seems like 18-20 BTDC ( plug vacuum advance ) ( Correct?, that's what I'm running )

 

Do you need to use an electric fuel pump?

Most suggest running one, but this might start a post battle...haha

 

Correct afr?:

Idle: ??

2k: ??

3k+: ??

Edited by jimmyjones000
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Great idea.

I've been playing around with mine for years. Trying to learn the differences in changing jets and the effects it has on different circuits. I'm certainly getting better at it.

But, would like to know what are the optimal AFR's also.

 

I have a book that is kept in the car. It has notes on what the settings, jets are and the weather condition, then I note down the AFR's at different types of driving.

Idle, Accellerate, WOT, cruise, pump, decellerate.

 

I've also got the manual for the bolt on kit, which has pages with recommended factory settings. I'll scan it and post it up.

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Great idea.

I've been playing around with mine for years. Trying to learn the differences in changing jets and the effects it has on different circuits. I'm certainly getting better at it.

But, would like to know what are the optimal AFR's also.

 

I have a book that is kept in the car. It has notes on what the settings, jets are and the weather condition, then I note down the AFR's at different types of driving.

Idle, Accellerate, WOT, cruise, pump, decellerate.

 

I've also got the manual for the bolt on kit, which has pages with recommended factory settings. I'll scan it and post it up.

 

That would be great info! Anyone out there with some AFR info?

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Updated factory settings in the first post.

 

My jet settings via Wolf Creek:

Mikuni 40 PHH

Main Air Jet 180 ( gonna test 200 next week )

Main Jet 150

Pilot Jet 62.5 ( gonna test 65 next week )

 

70' 240z

L28/N42 mild cam

6-1 Header w/ 2.25 pipe

Electronic ignition

3.7 psi fuel pressure ( dead head - no return )

20 BTDC Timing ( no advance )

8mm plug cables

NGK BPR6ES-11

Short Stacks with mesh caps

 

Installing an AFR gauge next week, Ill post the readings when I get them. Any suggestions?

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  • 5 months later...

So since nobody has said anything about this yet I'll chime in a bit. Just fyi this is all copied directly out of Frank Honsowetz' "How to Modify Your Nissan/Datsun OHC engine".

 

-To calculate your required throttle bore size you find the square root of your displacement-per-cylinder (in cc) multiply that by your maximum rpm, divide that by 1000 and then finally mulitply that by 0.82 (to clarify, calulate the square root of your displacement*max-rpm/1000 and THEN multiply by 0.82. Best to use calc to not mess up order of operations)

 

-To calculate your main venturi size you perform the same operation as before but instead of mulitplying by 0.82 at the end you mulitply by 0.65

 

-Once you have your main venturi size you can then get a decent main jet size by multiplying the size of your venturi by 0.04 (ex. 40mm Venturi * 0.04 = 1.60mm main jet) and can also find your air correction jet by adding 0.20 to whatever size your main jet size is (ex. 1.60 Main jet + 0.20 = 1.80mm Air Correct jet)

 

Keep in mind those are whats copied from the book, and while it is a very nice book (and you should go buy it right now) it should not be taken as gospel. Nothing beats a dyno day, wideband o2 and/or a lot of patience. I also understand that writing it all out like this can be rather mind melting so if anyone wants more claridication just let me know

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