what is the CFM on a stock 81 rx7 nikki
09-14-05, 08:09 AM
#3
Nikki-Modder Rex-Rodder
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313 cfm.
They are the same.
The bigmouth airhorn doesn't make a difference, even when the venturis are opened up to a flow of 465. (It was a suprise to us, too.)
They are the same.
The bigmouth airhorn doesn't make a difference, even when the venturis are opened up to a flow of 465. (It was a suprise to us, too.)
09-14-05, 08:59 AM
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I think the 84-85 is something like 288 cfm. Really terrible.
I may be mistaken. Carl does all our flow testing.
Keep in mind that the 288 gets exceeded by a RAM effect @ high RPMs with a modded Nikki. Otherwise you wouldn't realize the difference @ anything over 7000 rpm. But since the velocity is much stronger in a modded Nikki, the VE goes up, and you can make power @ 8500 rpm even with an 84-85 manni.
A ported manni will make the velocity work for the carburetor instead of the energy being wasted trying to stuff the engine. A free flow ahead of a strong velocity will make getting up to the rpm limit much faster. A ported stock manni will also allow you to rev right on up to 9+K, if your engine is built for it.
Even at 10K RPM, you're not maxing the flow of a 465 Sterling Carb. Carl has been working on a porting configuration that is reproduceable for relatively inexpensive production.
What he can't accomplish in port size, gets accomplished as much as possible in port profile.
It is completely scientific, and a careful compromise. The stock manni is so restrictive that simply hogging it out will be an improvement. But it will not be the optimal improvement.
I may be mistaken. Carl does all our flow testing.
Keep in mind that the 288 gets exceeded by a RAM effect @ high RPMs with a modded Nikki. Otherwise you wouldn't realize the difference @ anything over 7000 rpm. But since the velocity is much stronger in a modded Nikki, the VE goes up, and you can make power @ 8500 rpm even with an 84-85 manni.
A ported manni will make the velocity work for the carburetor instead of the energy being wasted trying to stuff the engine. A free flow ahead of a strong velocity will make getting up to the rpm limit much faster. A ported stock manni will also allow you to rev right on up to 9+K, if your engine is built for it.
Even at 10K RPM, you're not maxing the flow of a 465 Sterling Carb. Carl has been working on a porting configuration that is reproduceable for relatively inexpensive production.
What he can't accomplish in port size, gets accomplished as much as possible in port profile.
It is completely scientific, and a careful compromise. The stock manni is so restrictive that simply hogging it out will be an improvement. But it will not be the optimal improvement.
Last edited by Sterling; 09-14-05 at 09:03 AM.
09-14-05, 07:40 PM
#6
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i think if its completely cleaned and rebuilt, like brand new basically, its closer to 300cfm (313cfm i think was the official maximum number from someone flow bench or sumthing)
09-14-05, 10:07 PM
#7
Rx7Carl and Sterling have this number.
I think ApG Spaz got it at 313, but I could be wrong.
Jon
Edit: and of course once I merged the threads, this was answered by Sterling before I posted this! Oy Vey!
I think ApG Spaz got it at 313, but I could be wrong.
Jon
Edit: and of course once I merged the threads, this was answered by Sterling before I posted this! Oy Vey!
Last edited by vipernicus42; 09-15-05 at 03:24 AM.
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09-14-05, 11:36 PM
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sweeet thanks and ughhh is there any difference in the 81 rx7 nikki and the rx2 nikki ??
and my rx2 nikki is jetted for a 13b im not sure what size jets though but how much gain can i estimate thanks
and my rx2 nikki is jetted for a 13b im not sure what size jets though but how much gain can i estimate thanks
09-15-05, 12:17 AM
#9
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you could possibly see a loss of power if it's jetted for a 13b. it's impossible to say off the bat, you need to get it on there and play with some other jets. see what works best. usually all you will need on a stock port n/a 12a is maybe a jet size up on the primaries. no need to touch the secondaries.
09-15-05, 01:16 AM
#11
More flow for cheap???
You can get a bit more performance by using the carb from the 13b in a RX-4/Cosmo/REPU from the mid to late 1970s. I have a street ported 12a with a RB header and I dynoed 130HP to the wheels using this carb, peak power at 7,000, which is 1,000 higher than stock.
There are actually two version of this carb, 74-75 and 76-78, both the same size and I have never noticed any difference in performance. There were a few RX-3s produced using these carbs, but the intake manifolds are quite rare. I made an adapter to the 12a manifold. Been driving it since 1998, 30,000 miles with no problems. Runs very well, cold or hot. I even hooked up the cruise control.
There are actually two version of this carb, 74-75 and 76-78, both the same size and I have never noticed any difference in performance. There were a few RX-3s produced using these carbs, but the intake manifolds are quite rare. I made an adapter to the 12a manifold. Been driving it since 1998, 30,000 miles with no problems. Runs very well, cold or hot. I even hooked up the cruise control.
Last edited by stilettoman; 09-15-05 at 01:20 AM.
09-15-05, 02:25 AM
#12
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Does the FB REALLY dyno that high with just RX4 carb headers and a Streetport? What manner of streetport is this?
Maybe my power estimates for my FB aren't too far off anyway!
Maybe my power estimates for my FB aren't too far off anyway!
09-15-05, 02:36 AM
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sweet thanks well ill see how it runs ill just go around ******* with it .. any suggestions on where to get any new jets .. and anyone run a spacer ?? if so where can i get one thanks
09-15-05, 03:29 AM
#18
Alright alright....
I cleaned up the mess.
Personally, I can't wait to see what the finished Sterling/Carl Intake *system* will look like. Ported manifold, ultimate nikki, perhaps even that Carl-patented funnel-intake-canister-mod thingy?
Ooh... this will rock.
The only thing I can really see as being an advantage to the older carbs is that they'd be easier to rebuild/harder to screw up because they'd have alot less emissions CRAP on them.
Personally, since I've got the Mazda carb manual for the '84-'85, I don't mind rebuilding them and just scrap the e-stuff anyway.
Jon
I cleaned up the mess.
Personally, I can't wait to see what the finished Sterling/Carl Intake *system* will look like. Ported manifold, ultimate nikki, perhaps even that Carl-patented funnel-intake-canister-mod thingy?
Ooh... this will rock.
The only thing I can really see as being an advantage to the older carbs is that they'd be easier to rebuild/harder to screw up because they'd have alot less emissions CRAP on them.
Personally, since I've got the Mazda carb manual for the '84-'85, I don't mind rebuilding them and just scrap the e-stuff anyway.
Jon
09-15-05, 06:55 AM
#19
Nikki-Modder Rex-Rodder
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The older carbs are much easier to rebuild, as Vipernicus said, because of the lack of emissions crap.
But the 13b carbs are truly beautiful pieces of workmanship when compared to the 12 Nikkis. The only problem is that the venturis are not easily removed for modification, and they are the same diameter as the stock 12a Nikki. They do flow much better due to better profiling.
But the 13b carbs are truly beautiful pieces of workmanship when compared to the 12 Nikkis. The only problem is that the venturis are not easily removed for modification, and they are the same diameter as the stock 12a Nikki. They do flow much better due to better profiling.
09-15-05, 10:06 PM
#20
"Does the FB REALLY dyno that high with just RX4 carb headers and a Streetport? What manner of streetport is this?"
I did indeed get 130 HP to the rear wheels, consistent for three runs, ran it up to 9,000 once just to see where it ran out of breath. Pulls strongly up to 8,000. That was with the CAT removed and a stock muffler. It was TOO LOUD. I have been running it lately with an aftermarket cat and a more restrictive muffler, don't know what the power is now, but noticeably less. When I am in a hurry, I drive my other one, which has a Ford V8.
The porting is as follows: very mild cleanup and smoothing of the primary ports and intake runners, moderate porting of the exhaust and full street port of the secondary ports using the Racing Beat template. The idle is lumpy, much like a "cammy" street rod because of the very light aluminum flywheel, but the driveability is excellent. I have ported several this way, but all the others were 13b. All of mine were built as daily drivers, one in a GLC, a couple in a REPU.
I can't find the email, but the guru at Racing Beat answered a question I asked some time back, and if I remember correctly, he said the stock 12a carbs were 310 - 315 cfm and the RX-4 carb was 345 cfm. In any case, the difference is very noticeable. I always shorten the coil spring in the secondary actuator, and I plug the hole in the bleeder fitting and redrill it with a smaller hole. This will make the secondaries open earlier and more smoothly. Can't remember what size hole I used, but much smaller than stock.
www.cardomain.com/ride/646433
I did indeed get 130 HP to the rear wheels, consistent for three runs, ran it up to 9,000 once just to see where it ran out of breath. Pulls strongly up to 8,000. That was with the CAT removed and a stock muffler. It was TOO LOUD. I have been running it lately with an aftermarket cat and a more restrictive muffler, don't know what the power is now, but noticeably less. When I am in a hurry, I drive my other one, which has a Ford V8.
The porting is as follows: very mild cleanup and smoothing of the primary ports and intake runners, moderate porting of the exhaust and full street port of the secondary ports using the Racing Beat template. The idle is lumpy, much like a "cammy" street rod because of the very light aluminum flywheel, but the driveability is excellent. I have ported several this way, but all the others were 13b. All of mine were built as daily drivers, one in a GLC, a couple in a REPU.
I can't find the email, but the guru at Racing Beat answered a question I asked some time back, and if I remember correctly, he said the stock 12a carbs were 310 - 315 cfm and the RX-4 carb was 345 cfm. In any case, the difference is very noticeable. I always shorten the coil spring in the secondary actuator, and I plug the hole in the bleeder fitting and redrill it with a smaller hole. This will make the secondaries open earlier and more smoothly. Can't remember what size hole I used, but much smaller than stock.
www.cardomain.com/ride/646433
