High altitude and a carburator?

Whizbang · 08-11-2008, 07:45 AM

anyone know how bad altitude effects a carb. I want to drive my 82 GS out to colorado when i move, and it will using the carb to get out there. Will it make it?

Rogue_Wulff · 08-11-2008, 08:17 AM

Depending on how high you are going, you could have minor issues. The air gets thinner as you go higher, so you may need to lean it out a bit once you get there.
Sometime around 83 all 12A's came with the altitude compensator on the carb, before then, it was hit and miss. Mostly only the cars originally ordered for high altitude areas had the compensator.
If you have an aftermarket carb, you may have to drop a couple jets sizes.

Whizbang · 08-11-2008, 08:39 AM

so if i run an 83-85 carb i should be alright

Rogue_Wulff · 08-11-2008, 08:53 AM

Yeah. There is always a chance that the current carb could have the required item. I don't have a pic handy to show what the AC looks like.

Come to think of it, the AC may be removable, so you could add it, if needed.

Whizbang · 08-11-2008, 08:54 AM

alright cool. Things sound work out good then. Once i get there i am finishing my EFI conversion anyway so this is a temp. ordeal.

Rogue_Wulff · 08-11-2008, 09:12 AM

I looked thru the Mazda carb manual, and the AC is removable. 81-82 had a block off plate, unless it was designed as a high altitude car. 83-85 all had the AC.
The AC mounts on the airhorn, right by the rear secondary. Have a look at your carb, if there's a triangle shaped plate held on by 2 or 3 screws, it has the block off. If there's a big round valve attached to that spot, it has the AC.

Jeff20B · 08-16-2008, 11:15 PM

If you're at a really high altitude, you uszually need to jet your carb down one step or so. In other words, since most stock Nikkis came with 92 primary and 160 secondary jets, you're going to want to switch the pri to 91. It's a rare size but I have a nice set out of an Hitachi I'm going to use in a bit. Interestingly the secondaries can remain the same since they're only used on demand.

Rogue Wulff, I've seen the altcomp thing installed on all the Nikkis I've ever come across. And I live practically at sea level, being near Seattle and all that. It's news to me that it is optional/removable.

Rogue_Wulff · 08-17-2008, 09:20 AM

Mazda carb manual lists the alt comp as high alt only for 81-82, and shows a block-off plate as standard. I haven't actually seen one without the alt comp either, just passing along the info as published by Mazda.
As for removable, they show a gasket for it in the carb manual, so it must be removable.

RX-7 Chris · 08-21-2008, 11:17 AM

I'll help you with that carb when you move out here.

Whizbang · 09-03-2008, 08:49 AM

Quote:

Originally Posted by RX-7 Chris

I'll help you with that carb when you move out here.

sounds good to me. Going to have to see what the scale of my shear disappointment in the cars power as a i drive cross country. My friends B16 swapped civic taught me this well!

Might be opting for a 13b (s5 probably) swap. Well see what the wallet has to sway once i get myself established.

08-11-2008, 07:45 AM	#1
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	High altitude and a carburator? anyone know how bad altitude effects a carb. I want to drive my 82 GS out to colorado when i move, and it will using the carb to get out there. Will it make it? __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

08-11-2008, 08:39 AM	#3
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	so if i run an 83-85 carb i should be alright __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

08-11-2008, 08:54 AM	#5
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	alright cool. Things sound work out good then. Once i get there i am finishing my EFI conversion anyway so this is a temp. ordeal. __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

08-11-2008, 08:17 AM	#2
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	Depending on how high you are going, you could have minor issues. The air gets thinner as you go higher, so you may need to lean it out a bit once you get there. Sometime around 83 all 12A's came with the altitude compensator on the carb, before then, it was hit and miss. Mostly only the cars originally ordered for high altitude areas had the compensator. If you have an aftermarket carb, you may have to drop a couple jets sizes.

08-11-2008, 08:53 AM	#4
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	Yeah. There is always a chance that the current carb could have the required item. I don't have a pic handy to show what the AC looks like. Come to think of it, the AC may be removable, so you could add it, if needed.

08-11-2008, 09:12 AM	#6
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	I looked thru the Mazda carb manual, and the AC is removable. 81-82 had a block off plate, unless it was designed as a high altitude car. 83-85 all had the AC. The AC mounts on the airhorn, right by the rear secondary. Have a look at your carb, if there's a triangle shaped plate held on by 2 or 3 screws, it has the block off. If there's a big round valve attached to that spot, it has the AC.

08-16-2008, 11:15 PM	#7
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	If you're at a really high altitude, you uszually need to jet your carb down one step or so. In other words, since most stock Nikkis came with 92 primary and 160 secondary jets, you're going to want to switch the pri to 91. It's a rare size but I have a nice set out of an Hitachi I'm going to use in a bit. Interestingly the secondaries can remain the same since they're only used on demand. Rogue Wulff, I've seen the altcomp thing installed on all the Nikkis I've ever come across. And I live practically at sea level, being near Seattle and all that. It's news to me that it is optional/removable.

08-17-2008, 09:20 AM	#8
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	Mazda carb manual lists the alt comp as high alt only for 81-82, and shows a block-off plate as standard. I haven't actually seen one without the alt comp either, just passing along the info as published by Mazda. As for removable, they show a gasket for it in the carb manual, so it must be removable.

08-21-2008, 11:17 AM	#9
RX-7 Chris Rotary Fanatic Join Date: Mar 2008 Location: Colorado Springs, CO iTrader: (2) Posts: 132 Rep Power: 17	I'll help you with that carb when you move out here.