[Che]

Seeing i'm pretty new to Suzuki I'm not too sure the ins and outs of the Aisin carb (on a 1990 Sierra).

How is the second throttle plate controlled? Is it vacuum operated, mechanical, or some other method? I got no idea at this point in time, but need to know for my own sake.

Can anyone locate the control for me? I just converted to LPG, and can strip back the carb to a basic throttle body, but the secondary is still functional - don't want to lose it's operation.

[Santos]

Its vacuum operated, its got a vacuum actuator on the same side a the throttle body (big brass UFO Thing)

[royce]

in your case with it doing no metering you could probably adapt it to opening mechanically

[Santos]

might be easier to ge an Older nikki/aisin/mikuni carbthat aready has mechanical linkages and 28mm/32mm throats

[dank]

I had a nikki twin barrel carby from some old van on my sierra with a mechanical secondary and bigger primary and secondarys, had same bolt pattern as the aisin carb but the inlet manifold had to be opend up to accept the bigger throats on the carby which is no problem with a dremel and about 2 hours time!

It went a shit load harder and you could really feel when the secondary kicked in..fully adjuistable...

[31zook]

bet your new motor does better then a carby upgarde dank

[Che]

Does anyone know the throat size of the Aisin carb, or what size afermarket throttle body i'd need on a Sierra running LPG? My gas system is up and running now and it's pretty darn good as it is with the Aisin, but I want to screw together as efficient a system as I can. There's not a single page on the entire internet dedicated to LPG performance, so it starts here with me I guess.


I think there's a difference in manifold pressure on the intake side since switching fuels too - this is especially noticeable when i'm running around the hilly Brisbane hinterland at 90 - 100kmh. On a flat highway, the Sierra is capable of 125 now (never got that speed on petrol) and the low down torque and power increase of LPG is immediately noticeable, but at speed in the hills it struggles where it never did on petrol. I can't explain this.


Like has been mentioned, I think I have to work out how to open the second throttle plate mechanically, or get rid of it altogether (in the form of another throttle body). There's still a lot of junk in the carb (ie - jets, float bowl, lines), so maybe a dedicated throttle would be more suited? LPG is already cheap, maybe going this option will make it even more efficient / cheaper to run...



Any suggestions?