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Characters of a single throttle body?
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DeathBySnuSnu
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PostPosted: Sat Dec 14, 2019 3:10 pm    Post subject: Characters of a single throttle body? Reply with quote

Contemplating engine ideas for autocross.

So fuel injected and a cb dry pump pump.

As I went soooooo overboard with the last project I intend to keep this one simpler.

Imagine a sub 2L engine with old style panchitos, cb high flow fuel injection end pieces, and a fabbed center section with 54mm throttle body.
How would this behave? As in will it handle more cam than a single carb. With no fuel or venturi action going on it the intake does it act different?

In the end it may even get turboed, but it will begin normally as my little girlie will be driving.
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PostPosted: Sat Dec 14, 2019 3:14 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

I run a 48 mm single on my 1679 so I think a 54mm single on a sub 2L should be fine.
Oh........definitely add a turbo...... Wink

Single TB makes linkage a piece-o-cake.
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PostPosted: Sat Dec 14, 2019 3:31 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

Yes Clone.....I am headed down the same road as your buggy.

But it will begin as normally aspirated.
Just wondering how much cam I can get away with non turbo and with air only in the upper intake.
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PostPosted: Sat Dec 14, 2019 4:06 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

I ran a 39mm throttle body off a 1.9l escort on a 1641 It ran fine but was a bit too big. It felt like I was gonna bust the seat back.

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PostPosted: Sat Dec 14, 2019 4:18 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

I am a big fan of hair driers on engines but autocross is one place you need instant torque out of the corners. About the time the turbo is starting to work nicely you are into another corner.

Unless maybe your courses are a lot bigger and faster than the ones I was involved in years ago.
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PostPosted: Sat Dec 14, 2019 4:19 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

That is nearly identical to what I am proposing.
But it would be closer to 2L......say a 90.5 x 76 or a 94 x 69.

Did you ever run a more aggressive cam?
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PostPosted: Sat Dec 14, 2019 4:32 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

I have a 50mm TB on my 1600. But I also have a turbo. I think it's a bit too big for me. I have a cam that is 430 lift and 250 duration @ 50. Drives pretty good but I can make full boost on less than 50% throttle. Mine is pretty much stock other than the cam.
Off boost it drives around just fine so you should be good to go. The cam itself is a little much for my engine but that has nothing to do with what your doing.


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PostPosted: Sat Dec 14, 2019 4:32 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

I think I only ran a W100 on that engine. I eventually went turbo with a German FI setup. But if I ever did it again I’d use the mexi setup with turbo just for packaging.
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PostPosted: Sat Dec 14, 2019 4:40 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

And yes. The turbo (if ever) would be for me mostly. I only have a year or so left with little girlie. She will be the player first.
We used to race dirt track but it became too much work for me,Wrenching, repairing bang ups, loading everything up, hauling everything. She was 12 -13 then and doing the driving and I was everything else.
This could be the last thing we do together. She is 16 now and only has one more year left at the local community college. She is planning on a scholarship and leaving this little Podunk Redneckville town/state and heading to a major college for graduate studies.

Uhhhh I digress.....

Yeah how aggressive could I cam this setup.
And if it ever gets a turbo it will have to be small insta boost.
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PostPosted: Sat Dec 14, 2019 4:41 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

Dual TB would be more responsive. The less distance you have between the tb and the heads the better. But then you have to deal with linkage and of course $$.. Pick your poison.
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PostPosted: Sat Dec 14, 2019 4:47 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

Not afraid of dual tb.....have that on my other.

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PostPosted: Sat Dec 14, 2019 5:37 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

I have a lot of cam and a 50mm single TB and big ported big valve heads on a 2276. It doesn't cruise like a stocker, but it does okay. Not a lot of vaccum signal to tune a speed density setup, so I run Alpha-N, works great. Its turbocharged, but only above 4000rpm. I think you are wasting money on the high flow ends for that setup, unless the money has already been spent. Standard ends will do just fine and should match port to your Panchitos without welding, I'd assume.
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PostPosted: Sat Dec 14, 2019 5:56 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

If this is for your autocross car stick with N/A. I've watched several people try to run turbo cars over the years including me and my 84 GTI, and it has always been flop unless it was a factory turbo car and then it was just OK. You might make it work if you ran a very small turbo like something off of a 1.3L or less but as oprn said, you need torque out of the hole and very little time is spent at full throttle with the turbo spooled up

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PostPosted: Sat Dec 14, 2019 6:10 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

I agree. For autocross I wouldn't want turbo. I would prefer power be more linear. With the turbo it comes on and begins multiplying as it builds. Hard power to read.
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PostPosted: Sat Dec 14, 2019 6:50 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

Thanks for the info on characteristics.

Also.
That may explain why they lump turbo and non together and set up groups by displacement.

So maybe I should be considering a completely different engine/combo.
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PostPosted: Sat Dec 14, 2019 7:27 pm    Post subject: Re: Characters of a single throttle body? Reply with quote

I always thought it would be cool to build a short stroke big bore. Spin it as fast as possible.
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PostPosted: Sun Dec 15, 2019 12:33 am    Post subject: Re: Characters of a single throttle body? Reply with quote

buguy wrote:
I always thought it would be cool to build a short stroke big bore. Spin it as fast as possible.


Me too. and with long rods.

But one thing comes to mind: what you described is exactly the type 4. Shorter stroke, bigger bore. But with short rods, and it's not exactly known as a high-revving engine... Think
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PostPosted: Sun Dec 15, 2019 12:54 am    Post subject: Re: Characters of a single throttle body? Reply with quote

As to characteristics, I expect it's easier to modulate the throttle flow at low openings. Volume comes so fast and so strong with 4 throttles, it can be a bit jerky.

As to cam, I don't know, but I can also imagine that a sequential injection would allow you to "stretch" the camming a little bit, whatever it is. But acoustic lengths would be pretty close to stock, no? Soooo....I don't know, but I think it's worth looking at.
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PostPosted: Sun Dec 15, 2019 6:14 am    Post subject: Re: Characters of a single throttle body? Reply with quote

FreeBug wrote:
As to characteristics, I expect it's easier to modulate the throttle flow at low openings. Volume comes so fast and so strong with 4 throttles, it can be a bit jerky.

Absolutely the case with carbs so likely the same with FI.
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PostPosted: Sun Dec 15, 2019 6:58 am    Post subject: Re: Characters of a single throttle body? Reply with quote

I agree with the sequential. Not much gain in mid/high range, but surely helps at idle and low rpms.
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