Why does my non-turbo have a boost compensator on the IP?

Hey all,

I have a 92' supercustom with a 3L. Anybody know why my injection pump has the boost compensator on it? I thought they were for adjusting fuel amount for turbo's. Anybody else have a boost on their 3L?

I was having crazy smoke above 7000ft and was hoping it was an altitude compensator, but maybe I could adjust for smoke with the boost? Anyone have experience messing around with these?

Can you post a photo of your IP with the compensator circled? I get smoke up in the mountains as well, though if I back off the pedal a bit it will usually go away. It seems like the IP is over-fueling for the amount of air that can be taken in. I thought that the IP had an altitude compensator as well to dial back the fuel at lower atmospheric pressures, maybe mine's not working correctly, or mine doesn't have an altitude compensator. Haven't looked closely at the IP in a long time.

I don't have a good photo but this link is the exact one - same part number. The boost the sitting on top of the IP, the thing with the dome. The altitude compensator IP's have almost the same top, but if you look at the top of the dome, there's what looks like a cross indented on it.

https://page.auctions.yahoo.co.jp/jp/auction/q432333129


I was around Bryce Canyon and my smoke was so bad and it was such a dog on hills. I know non-turbo's smoke in thin air but it seemed really bad.

I've heard they used to have little aftermarket air scoops for the air intake but I can't find any/they probably don't make much difference.

Messing with ECT mode and overdrive does seem to help at least.

That's interesting about boost vs altitude module. In my service manual, it shows the altitude module with the cross pattern you mentioned:



Your van might be a candidate for deleting/blocking off your EGR system. Doing that on my van got a lot of my smoking issues sorted out, and resulted in a lot more available power. I think my EGR valve was malfunctioning and really messing up the fuel/O2 mixture. I have a post on the forum with some photos of the process.

Heading off to poke my head in the engine bay and see which module I have...

...and mine has the boost module as well. Now to figure out where that vacuum line goes that attaches to the top!

I haven't tracked the vacuum line yet, but I wonder if it just ends in a filter cap and just reads the ambient air pressure. If it was clogged I could see how a drop in pressure at altitude might keep the compensator from dialing back the fuel a bit.

I found a couple YT videos online of how to tinker with the macro/micro settings on the boost compensator:

Here's a link to a Japanese auction for the little air scoop you had mentioned. I've seen it go on sale for decent discount 1-2x a year

https://buyee.jp/item/yahoo/auction/t772898040?lang=en

I'm seeing on some Hilux forums that the vacuum line on the boost compensator connects to the intake manifold, which makes sense, and is probably the case on the Hiace as well. That could mean that it's even more likely that it could be clogged up due to PCV and EGR interactions gunking up the manifold. When I blanked off my EGR system I got a peek into the intake manifold and it's definitely got some buildup in it:

Ah nice, those are interesting vids about the boost. So it is essentially adjusting the fuel/air ratio then right? Similar to changing the jet size in a carb? So if it's overfueling in the mountains you could turn down the boost to get more air into your mix?

That air scoop is funny! Can't believe you found one. I was gonna make something rough out of sheet metal or something just to see if it did anything to test in the mountains.

I have my EGR solenoid disconnected but have blanked yet.

Just found this doc that answers alot of pump questions I was having. Super useful!

https://fdocuments.in/document/repair-denso-pumps.html

Awesome find! I've been poking around the engine bay, sussing out the vacuum routing, and I think that I'm going to pull the vacuum line off the intake manifold, just above the EGR gas inlet, and see if something is clogged. If it is, it's possible the lower atmospheric pressure at altitude isn't registering against the boost compensator, and could result in over-fueling. If I had a shop space I would pull the whole manifold and clean it and the ports out, but one thing at time