Mikuni HSR45 x 6 with ITG filters

Would love to get some more info on this set up - if you or anyone has anything they can share?

DSI uses that setup, maybe reach out to them.  Also some guys in japan, but I heard its harder to tune.  

They use a dcoe adapter you can buy and can bolt to any L6 triple intake.  

31 minutes ago, duffymahoney said:

DSI uses that setup, maybe reach out to them.  Also some guys in japan, but I heard its harder to tune.  

They use a dcoe adapter you can buy and can bolt to any L6 triple intake.  

Thanks!

I’ll try DSI

its definitely not a mainstream set up but has a lot of potential. I’ve tried my best “google-fu” but to much gets lost in translation to get any info on the few people in Japan running it.

Thinking about it running some HSR 42s on an L28. 

5 minutes ago, duffymahoney said:

 

Thanks! I’ve sent DSI a message and will try and call them this week.

There is a shop is Australia- MikuniOZ- who I think helped with this set up pictured gonna try and give them a call to.

Very hard to determine sizing for these carbs- I’ve seen someone running a hot l24/l28 on two 42s or 45s- and then I’ve seen an A15 running four 45s!

You haven’t mentioned from what I see information on the engine you are working with.

40 minutes ago, Yarb said:

You haven’t mentioned from what I see information on the engine you are working with.

Sorry- F54/P79 L28 at the moment- stock as far as I know, but gonna pull the valve cover to check the cam and maybe scope the pistons- running SUs. Having some fueling issues after long pulls (or highway on ramp through the gears) It was swapped into my 240 before I bought it- but the Z has a full MSA header and exhaust plus poly bushings all around, and upgraded brakes. So some one at some point did some work to the car so I need to check the engine out further.

I have another spare F54/p79 engine I’ll plan on refreshing and maybe bumping the compression a little and street cam later on but not looking for a crazy build.

Would love Mikuni 44 phh but they are very expensive now. Thought about OERs but haven’t gotten and response from them and have read mixed reviews on them. Had trouble with webers in the past on my 510. So that where these Mikuni HSRs come in. Easy access to Jets and replacement parts. I know that running 6 is overkill but the siren song of ITBs is calling, and it’s something a little different.

The dual HSR carbs is proven on a zcar.  Simple, cheap and run like hell.  

"Having fueling issues afyer long pulls"

Makes me wonder if your float bowls are set a little low or your fuel pump is weak?

8 hours ago, duffymahoney said:

The dual HSR carbs is proven on a zcar.  Simple, cheap and run like hell.  

Definitely a simpler fall back- just trying to find some more info out on running the rack of 6

1 hour ago, Patcon said:

"Having fueling issues afyer long pulls"

Makes me wonder if your float bowls are set a little low or your fuel pump is weak?

Fuel pump, filters and at least soft lines- will blow out the hard lines- are on the list.

I’ve done some basic tuning of the SUs - and the car drives pretty well other then the fuel issue after a prolonged pull- but not super happy with what the afrs and just not stoked on the SUs. That why I am looking at triples or maybe a rack of 6  Mikunis as such.

Well looks like DSI is not doing them or doesn’t want to. I sent them a note before calling and just got a response that “they are not able to help”

I would say those carbs aren't for the faint of heart and will end up being spendy by the time you are done.  Get some mikuni 40s off Yahoo japan and never look back.

Or go ITB.  Which can be done sort of cost effectively:) 

50 minutes ago, duffymahoney said:

I would say those carbs aren't for the faint of heart and will end up being spendy by the time you are done.  Get some mikuni 40s off Yahoo japan and never look back.

 

Or go ITB.  Which can be done sort of cost effectively:) 

I am considering PHHs but a think 44s would be better. There is a nice set on eBay right now with a new Harada manifold- but they are $4300 plus shipping and additional jets for tuning. That’s 5k pretty easy.

Was just trying to figure out some other options. 

35 minutes ago, Demo243 said:

I am considering PHHs but a think 44s would be better. There is a nice set on eBay right now with a new Harada manifold- but they are $4300 plus shipping and additional jets for tuning. That’s 5k pretty easy.

Was just trying to figure out some other options. 

Ebay is a rip off for mikunis.  Yahoo japan is or craigslist will be your best bet.  If you have a stock 2.8, the 40s are more then plenty.  

https://page.auctions.yahoo.co.jp/jp/auction/l1109952099

20 minutes ago, duffymahoney said:

https://page.auctions.yahoo.co.jp/jp/auction/l1109952099

Will be interesting to see where they finish from there. Do you buy them directly or are you using a broker for purchases out of Japan?

5 minutes ago, Patcon said:

Will be interesting to see where they finish from there. Do you buy them directly or are you using a broker for purchases out of Japan?

Can't buy direct to the US, so you have to use a broker or a person in Japan. 

Would be very interested to hear the negative feedback on The OER carburetors. When you reference DSI are you speaking of Datsun Spirit in Manassas Va.

Running a stock motor anything over 40 is too large IMO. You are talking 150bhp.

36 minutes ago, Yarb said:

Would be very interested to hear the negative feedback on The OER carburetors. When you reference DSI are you speaking of Datsun Spirit in Manassas Va.

Correct Datsun Spirit in VA - I’ve heard he stopped doing them because of cost, but that was when PHHs were more reasonable. I also heard he has an issue with V-Performance the other US HSR person who has a very poor track record per the forum’s…

OER issues I’ve heard of have been poor casting in the last few years, machining issues, lots of machining chips throughout the carb (basically requiring a clean and rebuild before install). Their direct correspondence with me has been poor. Sent a few messages and finally got one response today about 2 weeks later. I worry about future parts availability as well. Their price is right - especially right now with the YEN… but all that makes me nervous.

34 minutes ago, Yarb said:

Running a stock motor anything over 40 is too large IMO. You are talking 150bhp.

Per all the calculators and L28 seems to be right on the edge. Could go either way. And with plans to eventually build another engine I would go 44/45s to future proof it. I also think back to talking with the late Todd Walrich when I got the Mikunis for my L20b in my 510 and he said 44s no questions for the L20b- which is slightly larger cylinder size…- but he was a big fan of choking the bigger carb down and I never had any drivability issues.

Choking it down I think is where I’m really I’m really stuck on these HSRs since there is no way to do that… so are 42s better since they are smaller or 45s for for more upper end. I’ve read they do well in single cylinder applications since that’s basically what they were designed for big low rev’ing Harleys. CFMs are pretty close 213 for the 42mm and 237 for the 45mm - @ 12” of water… so trying to convert that to 1.5” of Hg which is what I think a Weber DCOE is typically measured at- I’ve read 418 @ 1.5”Hg I think for both barrels? So divide that by 2 to 209. I lost my calculation but I think I figured that the 45mm was 277 converted to 1.5”Hg.

All this is probably way over thinking it and complicating it… And I should just pony up for some PHHs or roll the dice on some OERs with Weber jets.

Also I’ve never been one to just do things the easy way… ie in my KA swap in the 510 I had a custom oil pan made instead of the standard crossmember flip and new swaybar. I also decided to run my Mikunis on it which required hunting down and manifold and figuring out ignition and what not. 

So I’m not opposed to the challenge of HSRs just trying to get some info from people who have ran them.

Edited December 4, 20232 yr by Demo243

I think the HSRs are sweet, it's just a rare swap, that will come with its own issues.  But by all means, do it and report back.  

What was OER’s response that you received 2 weeks later? Thanks 

Edited December 5, 20232 yr by Yarb

28 minutes ago, Yarb said:

What was OER’s response that you received 2 weeks later? Thanks 

First I asked them about Mikuni jet compatibility; since I was considering using their jets instead of Weber and had been told mikuni jets would fit- the answer is no they wont

“Mikuni genuine main jet cannot be used for OER products.
2. Only Mikuni genuine Air Jet 40φ can be used for OER
3. All OER Jet can be used for Mikuni”

I had better luck with a quick response, responding back to that email asking if they had any jetting recommendations for an L28 as a starting point.

To which they gave me the linked their product page and what jets come stock and said 

“Jetting and other settings will vary depending on your vehicle, engine condition, climate, environment, and the features you require.

Please enjoy the setting through trial and error!”

I can’t really fault them to their response to the jetting suggestions but I had heard they could help. 
 

So they is some communication there. Just not ideal- but also not too surprising considering the language barrier.

1 hour ago, duffymahoney said:

I think the HSRs are sweet, it's just a rare swap, that will come with its own issues.  But by all means, do it and report back.  

I’ll definitely keep everyone posted- and if I go with 6 I’ll probably start a thread on it so there is hopefully some long term info on it.

really wish I could get in touch with one of the few people who have done it.

But I’m thinking 6 42s should do it and hopefully be ok.