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Hitachi HT 18S-2S turbo /weber 48DCO/2SP

Any type of technical questions or info

Moderators: KillerRx4, orx626

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Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#1 Post by licence » Fri Mar 24, 2017 11:32 am

Question : Is a weber 48DCO/2SP suitable for turbo use ? or will it blow back into fuel bowl ?
I have a Hitachi HT 18S-2S turbo with with exhaust bracket for RX7 13B 80-85,
The engine has a extend pollished port with 53 engine hrs since rebuild by Aktins Rotary.
What is a safe boost pressure for the RX713B ? 7lbs , 12lbs ?
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Re: Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#2 Post by bumpstart » Fri Mar 24, 2017 11:48 am

i would implore that if you want to run boost , dont cut a corner and use an ECU and a CAS
for power, and reliability and a boost in economy at cruise
im not sure how that goes with redundancy and your legalities for airworthy
( i suspect there needs to be some sort of failsafe secondary ecu )

any carb can be made for boost by putting it all inside a boost box so that reference air is pressurised too and with a fuel pressure reg rated 1 :1 with pressure inside the box / inlet

boost wise even high compression motors will run low boost given a 12at boost retard dizzy ( or ecu control )

if lacking that dizzy then a fully locked dizzy at a slightly retarded setting can be made to work up to 6-8 psi before you would need to radically alter the base timing


when the going is hard, don't retard, remember your lubrication
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Re: Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#3 Post by KYPREO » Fri Mar 24, 2017 12:12 pm

^^^ what bumpstart said. Use ECU for fuel delivery and ignition.

The other problem with running a Hitachi HT-18S-2S (factory FC Rx-7 turbo) in your application is boost control. In an aircraft application no doubt you will have a very free flowing exhaust. Series 4 turbo Hitachi turbos have a single entry turbine with twin-scroll and puny single port wastegate. These struggle to hold down boost in factory form once you move away from the restrictive factory fitted exhaust. The series 5 type have the twin entry turbine with better twin wastegate flaps. They can still have issues with boost spike/creep, but tend to control boost a lot better.


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Re: Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#4 Post by licence » Sat Mar 25, 2017 9:51 am

Thank you both for your input,unfortunately i already bought the turbo off Gumtree, $350, looks like it might have to be used as a door stop in the shed!!



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Re: Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#5 Post by bumpstart » Sat Mar 25, 2017 11:24 am

turbo is a worthy idea, particularly in something dealing with altitude compensation, but blow thru carbs have plenty of compromises .

best to wait and pounce on injection perfection manifolds and injectors suit your block and a decent ecu, CAS and efi fuel pump . do it well


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Re: Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#6 Post by licence » Sat Mar 25, 2017 11:57 am

Sounds good, what is cas mean ? not up with abrievated words



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Re: Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#7 Post by licence » Sat Mar 25, 2017 12:06 pm

Opps, Abbreviated. What about the hollow floats in the carby bowl,will they crush under 5 or 7lbs pressure ? They are the black plastic type, might have to inject them with foam or something similar ?



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Re: Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#8 Post by bumpstart » Sat Mar 25, 2017 12:24 pm

licence wrote:Opps, Abbreviated. What about the hollow floats in the carby bowl,will they crush under 5 or 7lbs pressure ? They are the black plastic type, might have to inject them with foam or something similar ?
CAS-= crank angle sensor // usually for early engines, donated from an FC rx7

brass floats may have trouble with crush. plastic are usually urethane filled and OK . dont really think 6 pounds is an issue here


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Re: Hitachi HT 18S-2S turbo /weber 48DCO/2SP

#9 Post by licence » Tue Apr 18, 2017 10:30 pm

I discovered the RX7-13B engine in the gyro copter is a 6 port. When removing the carby & inlet manifold to install the cast turbo exhaust manifold & turbo. I thought the 4 inlet manifold tubes was a 4 port ? so does this discovery add extra power to the engine than a 4 port? And what year where the 6 ports introduced? I've been using Racing Beats tuning chart for the 4 port. The 6 port is quite a bit different. Fly & see.



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