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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: toms73novass ()
Date: January 13, 2019 06:13PM

Great info! thumbs up

-Tom


63' Monza Spyder Convertable (in process) MY Build Thread
65' Monza MY Build Thread
73' NovaSS 454 Big block
86' BMW 325es
98' Dodge 2500 12v Cummins Diesel with 1200 lb torque!
98' VW Jetta TDI, for daughter
01' Audi Allroad Stage 3 twin turbo

NFCC
Grand Island, NY

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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: playerpage ()
Date: January 13, 2019 08:29PM

Following

____________________________________________

Eric C. Player, Porterville, CA
Member: CORSA National, Central Coast CORSA, South Coast CORSA, and San Joaquin Valley Corvair Club
THEN: 1965 Monza 110 Canary Yellow
1967 Monza 140 Red
1966 500 110, Black
1965 Monza 110, Camaro Yellow
NOW: 1966 Corsa 180 Turbo, Blue.

"It would not have helped if I had [taken notes], as he would start a paragraph with, 'It is therefore obvious. . .' and go on from there to matters which may have been obvious to him and God but to no one else." -- Daniel B. Davis

------

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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: joelsplace ()
Date: January 13, 2019 09:30PM

Does it have a boss to add a powerjet? I would think you would need one with the turbo. I added one to a flat slide Mikuni many years ago.

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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: CoCoCo ()
Date: January 14, 2019 12:28AM

MattNall Wrote:
-------------------------------------------------------
> Slides are so much better than Butterflys!


We thought so too.
But float bowls are better still!


Paul

(hmm, picture is not showing up for some reason)
(edit two: there it is. Was still too large)



Edited 3 time(s). Last edit at 01/14/2019 12:33AM by CoCoCo.

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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: kmart356 ()
Date: January 14, 2019 07:22AM

joelsplace Wrote:
-------------------------------------------------------
> Does it have a boss to add a powerjet? I would think you would need one with the turbo. I added one to a flat slide Mikuni many years ago.

No boss for a powerjet. Here is a reference (see below) from Mikuni re: powerjet for Mikuni TM series used on 2-strokes. I do not expect to need one.

CoCoCo Wrote:
-------------------------------------------------------
> MattNall Wrote: Slides are so much better than Butterflys!
> We thought so too.
> But float bowls are better still!

Yessir, the HSR is flat slide and has float bowl. thumbs upthumbs up

Ken
'62 Spyder Coupe
Florida


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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: joelsplace ()
Date: January 14, 2019 08:14AM

I was thinking it might be a way to make it richer on boost.

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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: kmart356 ()
Date: February 03, 2019 06:20AM

Tuning update:

This part of optimization is based on previous work and the article by Robert E. Mathew for an SU carb published in 1986 Corsa Tech Guide. Robert described how the profile of the SU jet needle tapered section could be modified and reduced to increase the annular area between the needle and the fixed jet. For the HSR45, the needle and needle jet define this fuel area (as shown in diagram) that governs the fuel flow until the main jet area restricts flow. The main jet sits below the needle jet immersed in the fuel bowl.




The graph below plots the fuel area vs the needle position. The needle is straight from 0-35mm, the diameter tapers down to the smallest diameter at 65-70mm length. The tip of the needle does not lift out of the needle jet at WOT. The original needle/needle jet combo [Y-8 w_2.97] was rich on low end and lean in mid/top end. After re-reading the Mathew article a few times, I started the needle modifications and now have a more aggressive taper on the 2.98 needle (2.98v1) that combines with a smaller Y-6 needle jet to produce the solid line curve. I have another 2.98 needle and will attempt to profile that one to achieve "optimized" top curve (if further testing so indicates). The main jet clearly restricts flow at larger throttle openings. The 210 main jet was going very lean near boost so now using a drilled out 249 main jet (0.098"). The max main jet size is 0.106" which offers no restriction to annular area.winking smiley


Idle after warmup = AFR 12.8-13.2
No load at 1/8-1/4 throttle = AFR 12.5-13.2
Acceleration at 1/2 throttle = AFR 12.5
Just before boost at 3/4-WOT throttle = AFR 12.4-12.5





Another tuning modification that can be made for getting the Idle/Cruise AFR up into the 14.6-15.5 Lean Cruise range is to increase the arch of the slide cutaway for increase air flow. Testing will decide.



Ken
'62 Spyder Coupe
Florida


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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: 63turbo ()
Date: February 03, 2019 10:11AM

From the AFR's you listed, I'd say you are good to go for boost as is. Keep in mind when you go into boost, the turbo will at some point begin to demand so much air that it will overdrive the main jet, and richen the mixture, so you cant go by what the AFR'S are at wide open throttle short of boost to determine wether or not it is rich enough in boost. You might want to try your first boost test with the water/meth active, for safety, but I'd say you are good on jetting!

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car



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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: kmart356 ()
Date: February 25, 2019 04:15PM

After a few boost runs, I consulted with Kevin on the AFRs I was seeing when methanol injection activated. The custom taper on the jet needle had effectively gotten the AFRs into the happy zone during mid-throttle all the way up near WOT. The full on boost AFRs looked a little rich so I decided to install the largest size factory made 240 main jet to replace the drilled out 249. The desired results were quickly confirmed. Take a look at the diagram for the "before & after" AFRs. Green curve and green AFRs with 79*-80* air temp. Red curve was "as delivered" to compare AFRs. Seasonal tuning can now be achieved by simply raising/lowering the jet needle and perhaps a smaller main jet when the Florida summer kicks in.


The engine response is not only smoother through the entire RPM range, it seems to be more aggressive when going into boost. Rather than a build up it feels like a "surge" and the boost gauge goes up to max much quicker. I currently have the wastegate dump set at 12psi and it didn't take long to get to that point on numerous short blasts on country roads around here. The Mikuni is well mannered with no flat spots or hesitations and idles nicely at my chosen 980-1020 rpm.

Oh, the sound of the intake is really cool now as you can hear the turbine whistle during acceleration. smoking smiley



Ken
'62 Spyder Coupe
Florida


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Re: New Turbo Carb - Mikuni HSR45 smoothbore carburetor
Posted by: MattNall ()
Date: February 25, 2019 05:17PM

Luv carbs that are tuneable!

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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