1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

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Old 03-18-06, 10:59 AM
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Just for the sake of discussion/argument/to be different, etc...

I want to put my 13B in my FB. I'm going to carb it.

So, just for the sake of absurdity/fun/whatever, a thought dawned on me... Why not use motorcycle carbs? They have 1300 cc motorcycle engines, there's a wrecking yard around here with plenty of bikes, could those carbs work?
Old 03-18-06, 11:02 AM
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i would say any carb can work on any engine. but the question is are those carb going to supply enough fuel to run this engine, and can they be jetted sufficiently to provide this engine with enough fuel, the answer to that in my opinion is no. but what the hell give it a try if you can find them cheap why not.
Old 03-18-06, 11:25 AM
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What was that one guys name? Mackenzie71 or some ****.....

I think he had an NA supra running twin motorcycle carbs (there was a thread about it a long time ago) He just fabed an intake iirc.

Long time ago but I remember thinking it was an interesting idea. bike carbs are nearly free and very plentiful.
Old 03-18-06, 11:51 AM
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iirc isn't the 13b actually over 2000cc's in reality?
esp in air/fuel consumption?
Old 03-18-06, 11:59 AM
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It's about 5000cc's in the fuel consumption department...
Old 03-18-06, 12:00 PM
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Originally Posted by 13b4me
It's about 5000cc's in the fuel consumption department...
ah nice...so be drivin 5.0's eh..and it's not a Ford..woot
Old 03-18-06, 12:01 PM
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It's more about how much power than engine capacity, you'll only get as much power as per 14.7 to 1 ratio of fuel to air, so if less fuel than the car can use you'll get less power, once its tuned to the correct ratio.

However there are many motorcycles putting out more than 200 hp.
Old 03-18-06, 12:58 PM
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Originally Posted by aussiesmg
It's more about how much power than engine capacity, you'll only get as much power as per 14.7 to 1 ratio of fuel to air, so if less fuel than the car can use you'll get less power, once its tuned to the correct ratio.

However there are many motorcycles putting out more than 200 hp.
Yeah, how about 4 Hayabusa carbs?
Old 03-18-06, 01:01 PM
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Busas are injected.
Old 03-18-06, 01:46 PM
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I thought the older Busa's were carbed... Like early-mid 90's... ?
Old 03-18-06, 01:54 PM
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There was no busa back then (1300R)

There was the GSXR1100R with four mikunis though.............

Last edited by Alex-7; 03-18-06 at 01:58 PM.
Old 03-18-06, 02:09 PM
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On the old Toyota 4AG motors, Keihin FCR motorcycle carbs (41mm flat slide) are a popular swap. I've seen them on set-ups making around 200hp, and could probably support a 13B, the biggest problem would be fabbing a manifold/linkage. They're a bit pricey, but you may be able to find a cheap used set.

Old 03-18-06, 05:10 PM
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Originally Posted by RE Matsuda
On the old Toyota 4AG motors, Keihin FCR motorcycle carbs (41mm flat slide) are a popular swap. I've seen them on set-ups making around 200hp, and could probably support a 13B, the biggest problem would be fabbing a manifold/linkage. They're a bit pricey, but you may be able to find a cheap used set.

That's what I'm talking about. Good ****.
Old 03-18-06, 09:36 PM
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Go to the www.rotaryaviation.com site and look up some of the archives that Tracy wrote for Kitplanes magazine in the mid-'90s. For the first 850 hours on his 13B-powered RV4 sport plane he used three Mikuni motorcycle carbs that he had to properly jet for his CFM needs. Cost was minimal but it took him a while to fine-tune the set-up, mostly via trial and error.
Old 03-18-06, 10:32 PM
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Originally Posted by Aviator 902S
Go to the www.rotaryaviation.com site and look up some of the archives that Tracy wrote for Kitplanes magazine in the mid-'90s. For the first 850 hours on his 13B-powered RV4 sport plane he used three Mikuni motorcycle carbs that he had to properly jet for his CFM needs. Cost was minimal but it took him a while to fine-tune the set-up, mostly via trial and error.
Actually, scratch that--- those pages are no longer on his site. You'd have to scare up the October, 1995 issue of Kitplanes to read about it.
Old 03-19-06, 02:36 PM
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I LOVE MIKUNI'S. I would LOVE a twin MIKUNI set up. Is there no manifold for twin Mikunis?

I am intrested in this. I am poor so poor people mods that work are what makes my car work.
Old 03-19-06, 02:59 PM
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Originally Posted by no_name
I LOVE MIKUNI'S. I would LOVE a twin MIKUNI set up. Is there no manifold for twin Mikunis?

I am intrested in this. I am poor so poor people mods that work are what makes my car work.
Uh, Tracy Crook used an aerosol hairspray can cut into three pieces (along with some lengths of fuel filler neck hose) for his original "intake manifold" on his sport plane.

It worked just fine, but he gave up 20 hp by tying the two center (primary) intake ports together rather than giving them separate runners. These ports were fed by the center Mikuni while the outside (secondary) ports were fed by the two outside carbs. (Tracy has since switched to a much more effective and sophisticated fuel injection system using an ignition controller of his own design).

You'd probably do well not to duplicate this particular example though. I'd buy an existing Webber or Delorto manifold. I'd then fab an adapter out of aluminum or composite. Screw the adapter onto the ends where the carbs are to be mounted, then simply bolt the carbs to it.

Last edited by Aviator 902S; 03-19-06 at 03:02 PM.
Old 03-19-06, 04:25 PM
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COOL. If I do wind up doing something like that ( using a Delorto manifold) I will see how everything works and come up with a cheapo way lol.

Thanks
Old 03-19-06, 05:56 PM
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Dual sidedrafts seemed to make more sense than a huge downdraft (IDA), because they'd theoretically make the same high-end power but much better low-end and all around drivability.

I remember there was a thread a long time ago about a dual sidedraft set-up, someone had pics of a manifold, it wasn't wrap-around style but rather just a straight-out the side set-up. I'll try and find the thread again and/or the pics.

On the note of making a cheap manifold, you have to remember alot of motorcycles simple use heavy rubber tubing to connect the carbs/throttles to the intake, and they usually take more abuse then cars.
Old 03-19-06, 06:04 PM
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Here's some pics of a set-up, looks like there's room for a longer manifold for better bottom-end, as long as you use short velocity stacks:



Old 03-19-06, 08:01 PM
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Whose is that? That's awesome.
Old 03-21-06, 05:00 PM
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non-wraparound, tripple and dual:


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