18RC Air Pump Function?

[flemlux]

Hi Everyone,

I'm just wondering if anyone knows what the actual function is of the air pump thats on the front of an 18R-C motor? It is driven by a belt from the motor and pumps fresh filtered air from the air cleaner into the inlet manifold via a solenoid looking thing that I think is vacuum controlled. I have removed the pump and blocked off both ends of the hose with detrimental effects to economy and power. The little power the motor produces was literally halved once i had removed the pump and blocked off the hoses and my fuel economy was so bad, i may aswell buy shares in BP!

Put the pump back on today and re connected the hoses and hey presto, power and fuel economy back.

Why is this ridiculous looking pump so important for the engine to run efficiently and why haven't i seen it on any other carby fed car from the same era that has anti pollution gear?

[CELICASUPRA7M]

my 21rc had one, i binned it and it made no noticeable difference.

[thechuckster]

Its an emissions thing, fwiw the 5ME uses on to pump air into the exhaust to help combust any unburnt fuel.

[fixeruperer]

i thought it was just to pump air into the exhaust so it would pass emission's.

why make it use less fuel, when you can just pump more air into the reading haha.

[flemlux]

Yeah i've seen other air pumps on other engines that pump fresh air into the exhaust manifold but this on pumps it into the inlet manifold and if i remove it, it uses more fuel and the engine has has less power? Can't get my head around it! I can't even find an exact "official" decription on what it does exactly, looked in the haynes manual and even looked in the 18R toyota workshop manual!

[thechuckster]

My haynes manual for Celica 71-85 has the EGR and Air Injection info on pages 6-12 to 6-13

note: the air-pump should connect to the exhaust via a 1-way valve. If the pipe you disconnected did actually go to the intake, then it was the EGR.

The two manifolds are joined (exhaust gas heat is used to get the space under the carbi warm quickly (it aids in ensuring fuel has/is evaporating in the air-stream going to combustion chambers).

[flemlux]

My haynes manual for Celica 71-85 has the EGR and Air Injection info on pages 6-12 to 6-13

note: the air-pump should connect to the exhaust via a 1-way valve. If the pipe you disconnected did actually go to the intake, then it was the EGR.

The two manifolds are joined (exhaust gas heat is used to get the space under the carbi warm quickly (it aids in ensuring fuel has/is evaporating in the air-stream going to combustion chambers).

airpump0ha.jpgairpump24ea.jpg

I have included photos that show exactly where the air pump is pumping the air. It clearly shows it is being pumped straight into the inlet manifold. I have had a look in the section 6-12 and 6-13 of the haynes manual and it is very vague on how air injection systems work. Besides the fact that the diagrams are of a different engine, not an 18R (you can tell from the basic layout) and that the haynes manual has been so far useless to me, it contradicts what these photos show and what I am looking at when I look in my engine bay. The EGR is a separate pipe which I can see is actually at the centre of the manifold

Thanks for clearing up why the 2 manifolds are joined at the base of the carbi. I always wondered why that was!

If anyone out there can tell me how this particular air pump works and its benefits/uselessness, I would really appreciate it. I am due to leave on the 2012 Sh1tbox Rally in 4 days and I would really like to know a bit more about this system before I go.

[thechuckster]

The manual diagrams are for an 21R but it should do the same thing. The piping suggests it's recently been changed/replaced?

I cannot imagine why the pump would be shoving extra air into the intake manifold - it would be unmetered and fuck with fuel-air mixtures. Am impressed that the motor has been tuned to need some wacktactularness.

If you just plug up the hose (shove large ball bearing down it, leave everything intact) going to runner #4 does it still run like arse?


Will go thru my photo collection to see if I have any engine pics of my old RA40 before I stuffed the turbo in it. It was originally a stock 18R.

[thechuckster]

Found this pics in the http://www.toymods.org.au/forums/faq...am-thread.html

Figure 55


A diagram further down suggests the big valve behind the air pump is a ABV - Air Bypass Valve?

Do you know what car this motor came out of?

My recollection of these air pumps is that they were to help with unburnt fuel, this looks like either running lean to assist EGR (provide more air to assist in burning of unburnt fuel in exhaust gasses) or running leaner on trailing throttle or something else that I have no idea about.

[flemlux]

That diagram shows exactly where all of the pipes are going on mine. Yeah its got me stumped on why it would be leaning it out. It must have the mixtures adjusted to compensate for the extra air being forced in the manifold because when i plugged the pipe that goes into #4 runner, it ran like absolute shite!

The motor was a donor motor from a 1981 Corona but it had been recently reconditioned not long before I bought the car to get the motor. The anti pollution vaccum piping is as complete as i've ever seen on one of these motors with only 1 or 2 hoses going nowhere that I have "ball bearinged" The rocker cover says it's an 18R-C but i wouldn't be surprised if the carbi and pump was from an 18R-U as titled in that diagram you posted.

It does sound like it's compensating for the EGR by using fresh air but strange that I cant seem to find a description on why they have set it up this way?

[thechuckster]

Does it also run like arse if you just remove the belt driving the air pump?

[flemlux]

If i remove the belt it doesn't run as bad as blocking off the hose but it doesn't run as well as if it's all connected up and running. It actually seems to use more fuel if I block it off or remove the belt which is odd!

[thechuckster]

many lolz there - an emissions device from the early 80's that actually made your car run better

[TERRA Operative]

Can you ditch it and get the carby retuned? Not having the system connected is probably throwing your mixtures way out, the carby could be tuned to be rich to compensate for the extra air or something.

[CELICASUPRA7M]

basically you've discovered your motor is supercharged! put a smaller pulley on and see if it goes faster!