Port velocity and engine performance. - Suzuki Z400 Forum : Z400 Forums
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post #1 of 227 (permalink) Old 02-12-2012, 09:31 PM Thread Starter
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Port velocity and engine performance.

I have some new info for the gear heads

I've become further compelled to learn everything I can about 4 stroke engines for what ever reason. I'm not even really sure why anymore. I just bought a new book. "Performance Automotive Engine Math" by John Baechtel. The title pretty much gets me out of describing it any further.

In the book, there is a formula for figuring out port velocity. I also taught myself how to run Microsoft Excel today and I made a calculator for this. I will post it if I can figure out how. (Maybe someone can help me with that)

I started crunching numbers based on my 470 build which I dynoed last year, the numbers I was coming up with was suggesting that I was way too small on my porting and carb size. So I called suzukiray to discuss this with him, and he confirmed it and made a few suggestions.

12.5:1 470 (94mm x 67.6mm) +1 (37mm) intake valves +1 (30mm) exhaust valves, web 539+6/539 cams, 40FCR (which I knew was too small), custom header, and dyna for relevant mods. Here's the chart.




We have come to the realization on this board that these big bore strokers are needing quite large cams to breathe, and they are not giving up low end to get it. Mine certainly follows that trait. The porting is responsible for this. Information I have been finding has suggested that ideal peak port speed falls somewhere between 300-360 feet per second. With my setup as dynoed, it was beyond that by 7000rpm. (This is with a 90% volumetric efficiency correction factor also which should be generous for this type of engine) You can see it on the torque curve. With cams this size, it should be pulling hard beyond 10k, and it's not. The induction just can't handle as much air as this thing is trying to move. By 10k, it's trying to move the air at 521ft/sec.

I'm absolutely certain there is more power in this thing by porting it bigger. I'm going to see if I can find a HSR 45mm carb for it too. I will most likely lose some low end doing this, but I have smaller cams sitting around if I need them too, and if nothing else, for the sake of learning, I'm all about doing this! I can always go back to what I had


Now for the sake of discussion, I also believe I could also taper bore the FCR to 43mm and port to that size, and not lose a bit of useable power. Just pure gain on the high end.


I will try to find a way to post that calculator, but this is completely open for discussion if anyone has any questions, comments, or just wants to tell me I'm wrong, or an idiot.
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post #2 of 227 (permalink) Old 02-12-2012, 09:37 PM
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I'm all ears still thinking bout those megas sitting on the shelf with some larger valves!

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post #3 of 227 (permalink) Old 02-12-2012, 09:41 PM
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Idiot, It won't work. Nobody else is doing it!! This thread will be awesome. I will converse tonight.

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post #4 of 227 (permalink) Old 02-12-2012, 09:58 PM Thread Starter
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Quote:
Originally Posted by rcfan View Post
I'm all ears still thinking bout those megas sitting on the shelf with some larger valves!
I remember when we were talking about your build way back when. Do you still want to keep wicked low end? I don't see why they should hurt it at all. If you keep the ports/carb smallish, you will keep your low end for sure. I'd say you can pick up quite a bit all the way across the board.



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Idiot, It won't work. Nobody else is doing it!! This thread will be awesome. I will converse tonight.
What is this TRX450R.ORG???
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post #5 of 227 (permalink) Old 02-12-2012, 10:09 PM
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Originally Posted by CFM-Z440 View Post
I remember when we were talking about your build way back when. Do you still want to keep wicked low end? I don't see why they should hurt it at all. If you keep the ports/carb smallish, you will keep your low end for sure. I'd say you can pick up quite a bit all the way across the board.





What is this TRX450R.ORG???
With the way I have it geared and the Rekluse set up! Im willing to give up some more tq, infact I picked up another head that needs a journal repaired,that I was thinking about really opening up with plus one intakes and stock exhaust, but reading what mr! Ltz horsepower god! U lol Says I'm thinking oversized exhaust too!

03 Athena bbk,k.w.springs,port&polish,dyna prog, web540-540, Procircuit fullsystem ,39mmfcr, custom airbox intake built by me w/400ex tube and +4hotrods, Rekluse clutch, Elka LT shocks, burgaurd+2 a-arms, Protaper bars, ASV levers, ODI grips, AC propeg nerfs, ATV foreplay? +1 1/4swinger, Maxxis razor2S, black hyper wheels, Houser plus 1 stem, HID conversion, modded yamaha parking brake, G-force axle, and a woodsrider129 rotorgaurd and quick change clutch cover!
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post #6 of 227 (permalink) Old 02-12-2012, 10:16 PM
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I can't wait to see how this is going to turn out!


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post #7 of 227 (permalink) Old 02-12-2012, 10:22 PM
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Sredrum's prices
Bored FCR's 41mm,41.5mm,42mm and 42.5mm 125.00 shipped

FCR bored to 43mm 200.00 shipped

and it go's up from there.

i would like to see some flow numbers .
i have Ron's flow numbers some were and i have 2 heads setting at a bench getting ready to flow .
i also have flow numbers from a stock head some were

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post #8 of 227 (permalink) Old 02-12-2012, 10:46 PM Thread Starter
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Quote:
Originally Posted by rcfan View Post
With the way I have it geared and the Rekluse set up! Im willing to give up some more tq, infact I picked up another head that needs a journal repaired,that I was thinking about really opening up with plus one intakes and stock exhaust, but reading what mr! Ltz horsepower god! U lol Says I'm thinking oversized exhaust too!

Ha, I don't know if I'd go THAT far. I'm just an infected gear head. Yeah, if you're going +1, I'd do it on the exhaust side too. I'm looking into the potential for a +2 exhaust setup.
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post #9 of 227 (permalink) Old 02-12-2012, 10:52 PM
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Chuck, bore your carb to a 44. You won't lose bottom. I know I didn't. This engine is quite big enough to take it. Also, I told you so on the cams. Bigger is better in these engines. Mine will pull to the 10,800rpm limit, but not real hard. Prolly to 10,500 pretty hard. I also had a small port job. It's not small anymore by any means. I wish I could send you my head do you flow it. Id be interested in seeing what it would do.

OCTOBER 2009 QOTM

2012 QUAD OF THE YEAR

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64.33hp 41.57tq
+10mm stroker, 96mm ice cube
Hsr 48mm carb, big custom webs, ported and welded head, titanium valves, titanium wrist pin. A few more things.

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post #10 of 227 (permalink) Old 02-12-2012, 10:52 PM Thread Starter
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Quote:
Originally Posted by cataway View Post
Sredrum's prices
Bored FCR's 41mm,41.5mm,42mm and 42.5mm 125.00 shipped

FCR bored to 43mm 200.00 shipped

and it go's up from there.

i would like to see some flow numbers .
i have Ron's flow numbers some were and i have 2 heads setting at a bench getting ready to flow .
i also have flow numbers from a stock head some were

Feel free to post em if you can find em. I might eventually have some numbers, but I don't know just how fast I can get my flow bench calibrated.
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post #11 of 227 (permalink) Old 02-12-2012, 11:00 PM Thread Starter
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Originally Posted by kfxguy View Post
Chuck, bore your carb to a 44. You won't lose bottom. I know I didn't. This engine is quite big enough to take it. Also, I told you so on the cams. Bigger is better in these engines. Mine will pull to the 10,800rpm limit, but not real hard. Prolly to 10,500 pretty hard. I also had a small port job. It's not small anymore by any means. I wish I could send you my head do you flow it. Id be interested in seeing what it would do.

I'm going to try to find a Mikuni HSR 45. It's a bolt on, and leaves room to go bigger yet. The carb is meant for big v-twins. It's the newer bigger better version of the HS40 I used to run.

You can send me anything you want for a flow test. I kind of touched on it in my last post, but I don't know exactly when or if I will get it calibrated. I will be able to compare it to a stock head, or my stuff. I will be able to compare to stock and modified TRX450R heads too.
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post #12 of 227 (permalink) Old 02-12-2012, 11:06 PM
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It depends on if I have time or not. I actually have another head on the way I could duplicate the port job and send it to you.

OCTOBER 2009 QOTM

2012 QUAD OF THE YEAR

KFX525 (Kfx/Ltz400)
64.33hp 41.57tq
+10mm stroker, 96mm ice cube
Hsr 48mm carb, big custom webs, ported and welded head, titanium valves, titanium wrist pin. A few more things.

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Last edited by kfxguy; 02-12-2012 at 11:17 PM.
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post #13 of 227 (permalink) Old 02-12-2012, 11:09 PM Thread Starter
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Works for me. I've got more projects going right now than I have time, but the flow bench is pretty much at the top of the list.
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post #14 of 227 (permalink) Old 02-13-2012, 12:04 AM
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Now for the sake of discussion, I also believe I could also taper bore the FCR to 43mm and port to that size, and not lose a bit of useable power. Just pure gain on the high end.
i was thinking about this myself. i think it would be a very high strung combo, with a very powerful mid. perfect for race apps. or it could suck balls

i would like to see the calculator for sure.
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post #15 of 227 (permalink) Old 02-13-2012, 12:08 AM
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i dont understand any of the numbers or half the lingo but i love these threads. especially when cfm and kfxguy get to going back and forth. hey Chuck, is there a book or site that i can read on to get up to speed on the basics of what your talking about? not necessarily that math book you speek of yet but something a little more basic about flow,porting, all that good stuff. im a self taught mechanic and this is a bit over my head but would like to learn more. thx and good luck
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