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H2OSB
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Joined: April 14, 2013
Posts: 1293
Location: Modesto, CA
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 Posted: Fri Jan 13, 2023 7:15 pm Post subject: Re: Sidewinder 'Dip' |
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Not gonna lie, it's very interesting reading the thoughts of you high end guys regarding exhaust configuration. It amazes me how much tuning can be done with this old engine design, particularly after combustion.
Thanks for making this interesting
H2OSB
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chrisflstf
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Joined: February 10, 2004
Posts: 3444
Location: San Diego
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| Posted: Fri Jan 13, 2023 7:38 pm Post subject: Re: Sidewinder 'Dip' |
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| Maybe not so much a dip as it is an advanced peak, relative to rpm? |
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Mavelotta
Samba Member
Joined: March 27, 2006
Posts: 50
Location: Monroe, Wa.
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| Posted: Mon Jan 16, 2023 10:07 am Post subject: Re: Sidewinder 'Dip' |
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| chrisflstf wrote: |
| Maybe not so much a dip as it is an advanced peak, relative to rpm? |
I believe the early peak is a benefit of the long manifold design. This peak was present with ITBs but not as high but the dip remained. The line with astricts was with 40mm dual throttle bodies, and the solid line is the single 48mm intake.
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Alstrup
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Joined: July 12, 2007
Posts: 7216
Location: Videbaek Denmark
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| Posted: Mon Jan 16, 2023 1:55 pm Post subject: Re: Sidewinder 'Dip' |
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Without knowing I´d say that the above engine has a cam in the 245-250 degree range @ 0,050". What puzzles me is that it doesnt pull more upper end with dual throttle bodies.
The lack of lower to mid rpm torque is due to the Sidewinder as is the dip.
- I assume the engine is not hooked to the dyno anymore, so this may be a test for another time. Unbolt the muffler. Then take a piece of 2" pipe and measure 22-23" (for that engine size) up and cut. Install this pipe to the flange and do a couple of pulls. I will almost bet my lunch that your afr dip decreases quite a bit. Most likely around 50-60%. If you use the dual 40 TB´s you can most likely play with the intake length until the dip is just about gone.
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Paul.H
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Joined: April 03, 2015
Posts: 613
Location: England
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| Posted: Tue Jan 17, 2023 1:33 am Post subject: Re: Sidewinder 'Dip' |
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Oh no not again 
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Alstrup
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Joined: July 12, 2007
Posts: 7216
Location: Videbaek Denmark
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Mavelotta
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Joined: March 27, 2006
Posts: 50
Location: Monroe, Wa.
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Paul.H
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Joined: April 03, 2015
Posts: 613
Location: England
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| Posted: Wed Jan 18, 2023 1:45 am Post subject: Re: Sidewinder 'Dip' |
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| Mavelotta wrote: |
| Paul.H wrote: |
| Oh no not again |
@UK Luke 72 started it 😂 |
I know and I tuned it out by increasing the intake runner length so I think the conclusion is if you can't alter the intake length then put another exhaust on.
Intake runner would be something similar in length to this set up
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modok
Samba Member
Joined: October 30, 2009
Posts: 26787
Location: Colorado Springs
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| Posted: Wed Jan 18, 2023 2:36 am Post subject: Re: Sidewinder 'Dip' |
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NICE intake. Should make power.
Really would be better with 4 throttles.
The idle and cruse may a bit unstable with all that volume.
Glad to see the dub shop getting into manifolds  |
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Mavelotta
Samba Member
Joined: March 27, 2006
Posts: 50
Location: Monroe, Wa.
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| Posted: Wed Jan 18, 2023 10:02 am Post subject: Re: Sidewinder 'Dip' |
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| Paul.H wrote: |
| Mavelotta wrote: |
| Paul.H wrote: |
| Oh no not again |
@UK Luke 72 started it 😂 |
I know and I tuned it out by increasing the intake runner length so I think the conclusion is if you can't alter the intake length then put another exhaust on. |
I wasn't arguing anything, just putting more info out into the world. The dip is to be expected with this exhaust.
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UK Luke 72
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Location: Little Britain
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Paul.H
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Joined: April 03, 2015
Posts: 613
Location: England
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| Posted: Wed Jan 18, 2023 2:18 pm Post subject: Re: Sidewinder 'Dip' |
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| modok wrote: |
NICE intake. Should make power.
Really would be better with 4 throttles.
The idle and cruse may a bit unstable with all that volume.
Glad to see the dub shop getting into manifolds |
Yes my thoughts exactly and I did have those issues with something similar I played with, it took ages to settle down to idle after closing the throttle
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| Dauz wrote: |
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Paul.H
Samba Member
Joined: April 03, 2015
Posts: 613
Location: England
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| Posted: Wed Jan 18, 2023 2:23 pm Post subject: Re: Sidewinder 'Dip' |
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| Mavelotta wrote: |
| Paul.H wrote: |
| Mavelotta wrote: |
| Paul.H wrote: |
| Oh no not again |
@UK Luke 72 started it 😂 |
I know and I tuned it out by increasing the intake runner length so I think the conclusion is if you can't alter the intake length then put another exhaust on. |
I wasn't arguing anything, just putting more info out into the world. The dip is to be expected with this exhaust. |
Did you try without the muffler ?
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| Dauz wrote: |
| I'm not trying to be a d*ck, and it may be too late for that |
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Paul.H
Samba Member
Joined: April 03, 2015
Posts: 613
Location: England
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| Posted: Tue Jan 24, 2023 2:47 am Post subject: Re: Sidewinder 'Dip' |
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Here's the intake that didn't run well. it had unstable idle ,poor throttle response and the silicon hoses caved in under vac didn't even make it to the dyno . Cross pipe is 2.5 inch
Simple solution is to use dual throttles and add turbo
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| Dauz wrote: |
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Paul.H
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Joined: April 03, 2015
Posts: 613
Location: England
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| Posted: Tue Jan 24, 2023 3:16 am Post subject: Re: Sidewinder 'Dip' |
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For dual throttles this set up allows longer runner extension but obviously the low profile throttle bodies make it a lot easier and engine bay height will limit the length of the runners. Intake on the plenum would depend on engine size 2 inch for smaller motors 2.5 inch for larger high rpm motors with 2 inch runners
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| Dauz wrote: |
| I'm not trying to be a d*ck, and it may be too late for that |
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Ohio Tom
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Joined: February 09, 2006
Posts: 1660
Location: Marshallville Ohio
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| Posted: Thu Jan 26, 2023 4:08 pm Post subject: Re: Sidewinder 'Dip' |
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| Paul.H wrote: |
Just looked up the description of the FK10
"3500 -7500 rpm , hot street mild race "
I'm not arguing with the power band but the hot street mild race is subjective and I'd put it in the full race category with power range 3500-9000rpm using some of these new 044 CNC heads and valve train withstanding.
So now there are some anomolies appearing in the curve just as the cam starts coming on - what a revelation  |
LOL.. yep.. I don't even consider 3500 "on the cam" for the FK-10... More like 4,500... |
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madmike
Samba Member
Joined: July 11, 2005
Posts: 5292
Location: Atlanta,Michigan
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| Posted: Fri Jan 27, 2023 6:52 am Post subject: Re: Sidewinder 'Dip' |
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A.Creech told me to try the FK10 on my turbo bug ,,,he was right
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Rafo67PE
Samba Member
Joined: September 25, 2019
Posts: 42
Location: Lma
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| Posted: Fri Feb 10, 2023 3:45 pm Post subject: Re: Sidewinder 'Dip' |
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2276 Type1
1 5/8 A1 sidewinder "twin tube"
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UK Luke 72
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Joined: September 07, 2011
Posts: 2867
Location: Little Britain
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bugguy1967
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Joined: January 16, 2008
Posts: 4343
Location: Los Angeles, CA 90016
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| Posted: Sat Feb 11, 2023 10:51 pm Post subject: Re: Sidewinder 'Dip' |
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Idk how I missed all this, but I've seen this dip on many engines, using different exhausts. Are we sure this isn't an intake phenomenon, like some sort of resonance issue? Maybe the air is transitioning from a low-speed flow path to a different high-speed path...high speed, as in air speed, not rpm necessarily.
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