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Can u pick up hp

General engine tech -- Drag Racing to Circle Track

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Steve.k
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Can u pick up hp

Post by Steve.k »

Can you pick up hp with increased velocity and port work with no cam change or carb size change. Head work alone. Theoretically speaking and assuming head done correctly?Working on 4valve motorcycle engine with limited cam replacement and carbs.
PackardV8
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Re: Can u pick up hp

Post by PackardV8 »

Yes, No, Maybe. With port work being the only change, it depends on how bad the OEM port and how old the engine design. Today's sickle engines don't leave much on the CAD/CAM table.
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Steve.k
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Re: Can u pick up hp

Post by Steve.k »

Thanks Bill. Here what we got from head so far.


Stock .050-53.8, .100-109.4, .150- 154.4, .200-190.5, .250- 222, .300-246.1, .350-262, .400-264. Mod. .050-55.6, .100-108.5, .150-157.9, .200-201.7, .250-238.2, .300-267.5, .350-286.4,.400-294.4. Stocl port velocity @.350 lift 269.6 modified velocity @
350 lift 284.2. So far I can pick up a little more velocity but no flow with filling in. My next move is bigger valves.

New numbers with 39mm valve .060-56.1, .100-109 9, .150-158.1, .200-201.5, .250-238, .300-267.6, .350-281, .400-296.7, .450-300.5, .500-311.2.
BLSTIC
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Re: Can u pick up hp

Post by BLSTIC »

Quote
"Here what we got from head so far.


Stock
.050- 53.8,
.100- 109.4,
.150- 154.4,
.200- 190.5,
.250- 222,
.300- 246.1,
.350- 262,
.400- 264.

Mod.
.050- 55.6,
.100- 108.5,
.150- 157.9,
.200- 201.7,
.250- 238.2,
.300- 267.5,
.350- 286.4,
.400- 294.4.

39mm valve
.060- 56.1,
.100- 109 9,
.150- 158.1,
.200- 201.5,
.250- 238,
.300- 267.6,
.350- 281,
.400- 296.7,
.450- 300.5,
.500- 311.2.

Stocl port velocity @.350 lift 269.6 modified velocity @
350 lift 284.2. So far I can pick up a little more velocity but no flow with filling in. My next move is bigger valves."
/quote

No input on your specific case, just fixing it so it's much easier to read than numbers floating everywhere. Removed quote formatting so it showed the whole table on mobile view

In general though, yes porting alone can pick up power, it's basically the same question as "Can a head swap alone make power?" and it's got the same general answer of "Yes But...". Any 1D simulator should be able to do a decent prediction of what you'll get and if it's worth it

PackardV8 - What's a "sickle" refer to?
Steve.k
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Re: Can u pick up hp

Post by Steve.k »

Thanks. I think he means motor sickle. Lol. Yes this is old 650 klr single. Big bore to 705cc. And head work. Open exh up a bit and little carb work. Debating on hot cams also.
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Re: Can u pick up hp

Post by BLSTIC »

And I thought *I* was Master of The Dad...

But IIRC those things were underpowered when they came out and didn't get any better as time went on. Being old 4v motorcycle it's almost certain the ports are too large, and the cfm to hp formula says your stock head has enough airflow for 66hp. Modded head 73. Stock actual power is 44hp...

Were I building your engine I'd be putting everything I could into a 1D simulator, putting playdough into an inlet port until cfm was restricted to my target power, simulate that and see what cams or cam timing I need.

Apparently for the 2008 model:
"There’s improved throttle response from revised ignition mapping, and revised cam timing improved high-rpm performance. A redesigned cylinder head boasts new intake porting for greater low-end torque and quicker throttle response in city traffic, as well as improved top end p speed cruising on the open road."

I mean, it *sounds* like they filled the inlet port and changed the cams, nudge nudge
Steve.k
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Re: Can u pick up hp

Post by Steve.k »

I believe the cam is the same just revised the timing. I know another guy who ported same as us only higher flow he made. And added fuel injection for 62hp on regular unleaded. I believe he did hotcam swap also.
Steve.k
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Re: Can u pick up hp

Post by Steve.k »

BLSTIC wrote: Sun Feb 09, 2020 5:54 pm And I thought *I* was Master of The Dad...

But IIRC those things were underpowered when they came out and didn't get any better as time went on. Being old 4v motorcycle it's almost certain the ports are too large, and the cfm to hp formula says your stock head has enough airflow for 66hp. Modded head 73. Stock actual power is 44hp...

Were I building your engine I'd be putting everything I could into a 1D simulator, putting playdough into an inlet port until cfm was restricted to my target power, simulate that and see what cams or cam timing I need.

Apparently for the 2008 model:
"There’s improved throttle response from revised ignition mapping, and revised cam timing improved high-rpm performance. A redesigned cylinder head boasts new intake porting for greater low-end torque and quicker throttle response in city traffic, as well as improved top end p speed cruising on the open road."

I mean, it *sounds* like they filled the inlet port and changed the cams, nudge nudge
Took your advice and opted for cams.
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Re: Can u pick up hp

Post by BLSTIC »

My advice wasn't cams, it was much more about the porting and simulation. That said, it's not like you could make much more power with the stock cams anyway
Steve.k
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Re: Can u pick up hp

Post by Steve.k »

Well if i was sticking with stock bore it would help to fill ports. However thats not the case. The guy who has pioneered filling ports on these told me porting extremely helps this motor especially with bigger bore. The cams help the midrange alot so im told. Haven’t had to many engines that didn’t respond favourably to head work.
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Re: Can u pick up hp

Post by BLSTIC »

https://www.klrchris.com/klr650-small-port-head/

Specific example, with dyno graphs, of port filing dramatically improving a 2014 KLR650, which almost certainly has a better head than yours to start with. Dudes theory of velocity is wrong in places though.

I strongly encourage you to do the maths on velocity before going much further. At worst you learn something new, at best you make more power
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Re: Can u pick up hp

Post by Steve.k »

I talked directly to chris. He is the one that told me the above.on our bench you notice our stock flow no where close to his.
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Re: Can u pick up hp

Post by BLSTIC »

Yeah i suppose I missed that. Every bench and operator is a little different, much like dynos, but not that different.

So what is the design difference between your head and his? Are the heads interchangeable, or could you copy the later model port into the early head?
Steve.k
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Re: Can u pick up hp

Post by Steve.k »

I believe chris’s head was gen 1. Mine is gen2 being a 2010.
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Re: Can u pick up hp

Post by BLSTIC »

I thought you meant old old. Never mind my ramblings then, they probably don't apply to the newer head designs. As much
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