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Old 02-18-2010, 12:52 PM   #241
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Quote:
Originally Posted by Braineack View Post
With that said, I elaborate on my simplification:

Longer runners will increase torque in lower RPMs because they have a lower resonant frequency. Coupled with the fact that the length and combination of typically smaller OEM diameters help increase the air velocity.

Shorter runners will increase torque in higher RPMs because they have a higher resonant frequency. Further exaggerated by the shorter length and combination of typically larger diameters promote higher air flow rates, however hinder low-end performance due to this same fact.

It's all a compromise.
Totally agree, I wasn't trying to start a pissing match. I wonder if a slightly larger plenum and slightly longer runners might helped with the resonance buzz on your Frankenintake.
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Old 02-18-2010, 12:58 PM   #242
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Quote:
Originally Posted by sn95 View Post

The lump of torque in a specific spot is probably only achievable if you simultaneously tuned intake runner, cam and exhaust header length to that spot.
This serves to further illustrate why you do not want to make your runners too short.

Our motors (cam profiles, heads, and intake manifold) were tuned for mid-rpm torque. It gets very complex, and we are only changing one of those variables. We can not expect to run completely in the opposite direction and expect it to work well.

I would consider any runner length <8" worthless on a motor with a stock head. If you have a '99 head, +1 valves, solid lifters, Integral cams, port and polish, and plan on making nothing but gobs of high rpm power you may consider going shorther than this.

Remember that the OEM manifolds are 13-16" runners, and generally produce good torque between 3500-5500rpm. We are simply trying to augment the torque curve above this, or massage that power up the range a little bit. We can not completely change these characteristics without tuning every variable just right.


EDIT: I'm agreeing her, just felt like making a point.
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Old 02-18-2010, 12:58 PM   #243
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my plenum was 4" x 13 x 4" = 163 CI = 2.6L = 165% larger than displacement and had 6" runners.



Now, just look at JayL's last dyno. Nothing but gains above 5.5K, he has like 4" runners.






The idea of this Honda IM is a compromise between an extreme top end IM and the **** stocker while maintaining the integrity of the mt.net community's inherent need to be as cheap as possible.
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Old 02-18-2010, 12:59 PM   #244
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is there anybody of you that might have theory on intake manifold?

I would like to learn more about these

thx
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Old 02-18-2010, 01:32 PM   #245
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Default Still not convinced on short runners

I'm still leery of going too short on intake runners unless you are running an all-out drag car that can effectively launch and hook at over 5,000 RPM and never go below 5K until you shut-down past the traps. If you are driving mostly on the street, the combo that yields highest avg tq/avg hp from 3,000-7,000RPM is going to be hard to beat. If you are road racing on a high speed circuit, highest avg tq/avg hp from 4,000-7,500RPM. I think people spend way too much time trying to get the highest peak tq/hp numbers without considering how much time the engine operates outside of that peak.
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Old 02-18-2010, 01:37 PM   #246
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preaching to the choir.
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Old 02-18-2010, 02:05 PM   #247
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^The really interesting thing to me in that last dyno though is that the high flow intake (that one would assume is more a dyno queen with the short runners) actually made a lower peak TQ number, yet a much better TQ band. Not a doubt in the world that it would demolish the stocker in any form of racing save for tractor pulling or racing with a CVT transmission.

Cant read too much into it as thats abviously not the setup that everyne is running, but the point that yu can make is that OEMs are most certanly NOT above going for a peak number for marketing. Honestly within the bounds of driveability my bet is that OEMs will be MORE prone to a peak number than the average enthusiast these days.
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Old 02-18-2010, 04:02 PM   #248
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Quote:
Originally Posted by Sparetire View Post
^The really interesting thing to me in that last dyno though is that the high flow intake (that one would assume is more a dyno queen with the short runners) actually made a lower peak TQ number, yet a much better TQ band. Not a doubt in the world that it would demolish the stocker in any form of racing save for tractor pulling or racing with a CVT transmission.

Cant read too much into it as thats abviously not the setup that everyne is running, but the point that yu can make is that OEMs are most certanly NOT above going for a peak number for marketing. Honestly within the bounds of driveability my bet is that OEMs will be MORE prone to a peak number than the average enthusiast these days.
Yeah, the problematic part is that there is no comparison between a high flow intake with 10" runners vs. the high flow intake with short runners. I'd bet that an intake with 10" runners which flows the same CFM as the short runner intake will make lower peak torque and have a lower/better tq band than the short runner equivalent.
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Old 02-18-2010, 04:28 PM   #249
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Old 02-18-2010, 05:17 PM   #250
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+1 on the Phillip Smith books. His "The Design and Tuning of Competition Engines" is a good prequel to "Scientific Design of Exhaust & Intake Sytems".

The Desktop Dyno books are pretty basic and somewhat limited as reference works as is the current Dynosim manual. You really need to to step up to the Dynomation5 manual (http://www.motionsoftware.com/downlo...sersManual.pdf ) to get into full wave action modeling.
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Old 02-18-2010, 05:40 PM   #251
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Quote:
Originally Posted by Sparetire View Post
(that one would assume is more a dyno queen with the short runners).
Actually it's a street driven 11 second car. (hit 10 seconds yet?!?) Good guy, great build. Dyno queen is not a phrase I would ever use in regards to JayL's car. He drags. He's not looking for low end power. Purpose built is the term I would use.
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Old 02-18-2010, 09:04 PM   #252
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^Bingo. But the manifold looks like it would be a dyno queen focused rig, and it really isnt, which is cool.

SN95 makes a good point though that we dont have a plot from a long runner version of the same unit. It could well be even better in terms of overall TQ band.

I have some reading to do.
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Old 02-22-2010, 04:56 PM   #254
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Originally Posted by Full_Tilt_Boogie View Post
Im not sure who did this but Ive had these pics on my computer for a while now. Im pretty sure the manifold was for a GSR (B18C1), and that a BP flange mated to it pretty easily.







hey dose anyone have a shot of this manifold on the motor? and if possable some measurements of it?
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Old 02-22-2010, 04:59 PM   #255
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I forget who was the one that did that. Possibly 'eliminator'?
Anyone remember?
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Old 02-22-2010, 06:08 PM   #256
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Read the 1st page again. The Honda boards don't like the VictorX but do like the PerformerX. VictorX sucks for performance under 8000 rpms. PerformerX is the Edelbrock that would work better for our cars powerband.
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Old 02-22-2010, 09:15 PM   #257
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I have a shot of one of those on a motor.
Ric @ Racing mazda done the one I used to have

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Old 02-22-2010, 09:26 PM   #258
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When it's all done and installed, it looks a lot like the BEGI cast intake, and we know that works.
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Old 02-22-2010, 09:35 PM   #259
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When it's all done and installed, it looks a lot like the BEGI cast intake, and we know that works.
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Old 02-22-2010, 10:08 PM   #260
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So why is BEGI working on a new design then?
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