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Hitachi tuning and modifications... part deux!


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6 replies to this topic

#1 GeneralDisorder

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Posted 30 March 2008 - 09:33 PM

Please read my first installment to this Hitachi series here:

http://www.ultimates...ead.php?t=86141

When we left our hero in the last episode, he had removed the AAV system, and the thermo-valve that controls the air supply for the mixture ports.

Now lets discuss the choke system :dead:.

This system is just silly. It has:

1. Electric choke heater.
2. Choke idle-up cam system (increases idle speed with the choke on).
3. Mechanical choke pull-off (pulls the choke open with throttle movement).
4. Vacuum choke pull-off (pulls the choke open with manifold vacuum).
5. Vacuum choke pull-off limiter (pulls the choke closed with orificed vacuum).

:eek:

The Weber's seem to do fine with only the first 3. This whole vacuum system is basically unnecessary. Good chance it leaks too.

Furthermore, the mechanical choke pull-off is adjustable. This is most excellent because it allows us to compensate for the removal of the vacuum pull-off system. Lets see some pics:

In the below pic, #1 is the choke pull-off vacuum pot. Go ahead and disconnect it - there is no need to plug the ports on it. #2 is the manifold vacuum supply port. Plug that sucker.

Posted Image

Below you can see under the passenger side of the air cleaner - #4 is the port for filtered air to the thermo-vacuum valve, and #3 is the valve itself. Remove any lines to them, and plug the air cleaner port. There is no need to plug the themo-valve.

Posted Image

Remember to make any necessary adjustments to the idle and mixture after doing this. I noticed my idle smoothed out a bit more with the removal of this pot. It probably leaks, or the thermo-valve leaks. Either way I had to adjust my mixture and idle speed again.

I've had mine this way for about a week. I did have to adjust the choke a bit, but other than that you really can't tell it's gone. I haven't adjusted the choke pull-off on mine, but I may do that soon. I'll update this with a picture of the pull-off adjustment bolt, and any changes I made to my stock adjustment.

The good thing about this mod is that it really only affects your COLD idle. If you get the settings all messed up, once the choke pulls off it will be normal again. Adjusting the choke, and adjusting the mechanical pull-off should be enough to compensate for the removal of this system. Much like a Weber, you may have to re-adjust things seasonally. The complicated thermo-vacuum pull-off system is designed to make seasonal adjustment unnecessary, but at this point the system has leaks, and a questionable thermo-valve. Better to dump it and adjust it to your needs in my opinion.

GD

#2 Durania

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Posted 30 March 2008 - 10:03 PM

I have a Weber and when 86BRATMAN was down the other day, he showed me that if you remove this thing, you get a sweet boxer rumble out of it. Since you are on the subject of extra Hitachi junk, what is the harm in running with out this thing, only effect I noticed was a sweet sound.

Posted Image

#3 GeneralDisorder

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Posted 30 March 2008 - 10:17 PM

I have a Weber and when 86BRATMAN was down the other day, he showed me that if you remove this thing, you get a sweet boxer rumble out of it. Since you are on the subject of extra Hitachi junk, what is the harm in running with out this thing, only effect I noticed was a sweet sound.


:eek: Jesus - you people are dangerous. Tell him to think before he does things, and not to do anything to your vehicle till he understands what it is he's doing.

That is the air intake for the Air Suction Valve. The plastic peice you are refering to is known as a "silencer" and is a muffler of sorts as it keeps the exhaust noise from getting into the engine bay.

If (more likely WHEN) the ASV's reed valve fails, as they are very prone to doing, raw exhaust fumes will be allowed into your engine bay. Although the silencer wouldn't prevent this, it and it's connection the filter box prevents foreign objects from entering the reed valve assembly, and subsequently the exhaust and the catalytic converter. Removing it both opens the possibility of sucking in stuff that will adversely affect the matrix of the cat, and definately shortens the life of the reed valve.

If you remove the reed valve assembly, and install a quarter in the valve body then put it back on you will have effectively plugged the system. It can't fail when plugged in that fassion. It doesn't make "cool noises", but if you want those do it right and replace the muffler with a straight pipe.

GD

#4 Durania

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Posted 30 March 2008 - 10:45 PM

I only ran it like that for about 5 minutes is why I was asking. It sounded cool but that was it.

Thanks GD.

#5 TeamCF

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Posted 01 April 2008 - 01:17 AM

Thanks for these Hitachi help posts.
Went and did everything mentioned so far tonight. Plus replaced a few old lines. (made sure to check for the metering inserts)
Everything runs good and is looking so much simpler underhood. :banana:

#6 smelly_cat

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Posted 07 August 2008 - 05:25 PM

I finally did some of this. On pics 1 and 2 , I have 2 vacumn pull off things in stead of one. The hose that goes out from No1 goes into a vac pull off then a hose from that goes to a 2nd pull off. I capped it.


I think I have more power and the idle is definitely smoother. I had to tap the pedal alot to get the idle down to 700. I'm gonna run it hard tomorrow. I need to adjust the mech choke probaly and see if the mixture is off. SC

#7 GeneralDisorder

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Posted 07 August 2008 - 06:58 PM

I finally did some of this. On pics 1 and 2 , I have 2 vacumn pull off things in stead of one. The hose that goes out from No1 goes into a vac pull off then a hose from that goes to a 2nd pull off. I capped it.


Yeah - that would be the '84+ style pull-off. It's basically the same just has two pots instead of a single pot with two ports.

GD




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