SuzukiSavage.com - Tuning intake and exhaust

diamond jim

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Tuning intake and exhaust
05/17/09 at 08:40:07

I've been researching more on intake tuning and exhaust tuning.

I found these formulas for exhaust tuning:

For diameter:
d^2=SxRPMxD^2 /108,000

d is pipe diamater
S is the stroke
D is the piston diamater
^2 means squared

For length:
L=TxV/ N

L is pipe legnth
T is camshaft timing in crankshaft degrees
V is speed of wave in exhaust pipe(1,700)
N is RPM desired (500 RPM below peak)

Are any of you familiar with these formulas? I'm trying to improve my knowledge of pulse wave tuning and how it can shift the powerband up and down.

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PTRider

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Re: Tuning intake and exhaust
Reply #1 - 05/17/09 at 08:53:34

Which rpm peak do you wish to tune for?
6500 engine red line?
5400 rpm power peak?
3400 rpm torque peak?

(My guess would be for the power peak.)

Your local library might be able to get you a copy of Scientific Design of Exhaust and Intake Systems, Third Edition, Phillip Smith and John Morrison, Bentley Publishers, ISBN-13:978-0-8376-0309-4. Ask the library for an inter-library loan to borrow the book from another library. Or, buy it for $30. Or PM me and I'll lend you my copy.
http://www.bentleypublishers.com/automotive-engineering/Scientific-Design-Exh...

By the way, Smith and Morrison say that optimizing the intake is about half as effective as optimizing the exhaust.

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verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 29042 L.A. California Gender:	Re: Tuning intake and exhaust Reply #2 - 05/17/09 at 09:34:30 So running a few numbers... d=rpm x .000469009259 inches 1.41 @ 3k 1.88 @ 4k 2.35 @ 5k 2.81 @ 6k The ID of the pipe is some where around 1.75 So we are tuned for peak torque.
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diamond jim

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Re: Tuning intake and exhaust
Reply #3 - 05/17/09 at 09:43:16

I'll look at the college library. Here's a great read:

http://bmwmotorcycletech.info/InExTuning.htm

Also, my M50 pipes have the same ID as the LS650. It is known for it's torque as well. I cut one of my M50 stock pipes and use the header for quick bolt on testing when working on the S40. It's about 24" long but for basic stuff (see if the engine still starts and runs kinda stuff) it beats installing the entire S40 exhaust as mine is now a full one piece setup.

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marshall13

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Re: Tuning intake and exhaust
Reply #4 - 05/17/09 at 10:08:42

verslagen1 wrote on 05/17/09 at 09:34:30:

So running a few numbers...
d=rpm x .000469009259 inches
1.41 @ 3k
1.88 @ 4k
2.35 @ 5k
2.81 @ 6k
The ID of the pipe is some where around 1.75
So we are tuned for peak torque.

why do i end up with a 1.75-1.8 inch pipe as the id for 6500? 3.76x6500x14.376/108000= 3.2 which is the square of a number between 1.75 and 1.8.... where did i mess up? i come up with 1.75-1.8 inch pipe @ 63.5 inches for the optimum 6500 rpm pipe....

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verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 29042 L.A. California Gender:	Re: Tuning intake and exhaust Reply #5 - 05/17/09 at 10:16:05 oops I forgot to take the square root. d^.5=rpm x .000469009259 inches 1.19 @ 3k 1.37 @ 4k 1.53 @ 5k 1.68 @ 6k 1.75 @ 6500 So we are tuned for peak HP
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diamond jim

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Re: Tuning intake and exhaust
Reply #6 - 05/17/09 at 10:21:07

Regarding the intake, there are inevitably trade-offs for the sake of noise, harness, vibration, ease of maintenance and more often packaging. While the engineers worked to optimize the package as much as possible, there are some areas of improvement present. The six inches in front of the carb, IMO, is one of the biggest areas for improvement and the biggest bang for the buck. It, too, is effected by pressure pulses like the exhaust just in reverse. Getting both sides to match across the broadest rpm range is my goal.

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marshall13

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Re: Tuning intake and exhaust
Reply #7 - 05/17/09 at 10:27:23

verslagen1 wrote on 05/17/09 at 10:16:05:

oops I forgot to take the square root. Embarrassed

d^.5=rpm x .000469009259 inches
1.19 @ 3k
1.37 @ 4k
1.53 @ 5k
1.68 @ 6k
1.75 @ 6500

So we are tuned for peak HP

ahh, much more similarity now...lol i got 1.2@152 inch length for 3k, 1.55@84.6 for 5k, and 1.75@63.5 for 6500.... what's the overall length of your longshot system, Jim?

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marshall13 Senior Member Offline the first step is to admit your ignorance Posts: 301 Fort Lauderdale FL Gender:	Re: Tuning intake and exhaust Reply #8 - 05/17/09 at 10:29:37 want to see some rediculous numbers? input metric figures with the inch formula... rofl, i got a 9 inch pipe id for 6500 rpm using metric... kinda was a clue that i made an error....rofl
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verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 29042 L.A. California Gender:	Re: Tuning intake and exhaust Reply #9 - 05/17/09 at 11:13:38 d'jims longshot is much easier to figure out than the stock can due to the infernal baffeling.
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marshall13 Senior Member Offline the first step is to admit your ignorance Posts: 301 Fort Lauderdale FL Gender:	Re: Tuning intake and exhaust Reply #10 - 05/17/09 at 11:21:43 verslagen1 wrote on 05/17/09 at 11:13:38: d'jims longshot is much easier to figure out than the stock can due to the infernal baffeling. yeah, the roundabout path to the atmosphere once the gas leaves the headpipe is quite the mystery.... im guesstimating the headpipe at roughly 30" length.... think im close?
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diamond jim

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Re: Tuning intake and exhaust
Reply #11 - 05/17/09 at 18:02:48

marshall13 wrote on 05/17/09 at 10:27:23:

verslagen1 wrote on 05/17/09 at 10:16:05:

oops I forgot to take the square root. Embarrassed

d^.5=rpm x .000469009259 inches
1.19 @ 3k
1.37 @ 4k
1.53 @ 5k
1.68 @ 6k
1.75 @ 6500

So we are tuned for peak HP

ahh, much more similarity now...lol i got 1.2@152 inch length for 3k, 1.55@84.6 for 5k, and 1.75@63.5 for 6500.... what's the overall length of your longshot system, Jim?

It's 62" long. Pipe diameter is 1.75".

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marshall13

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Re: Tuning intake and exhaust
Reply #12 - 05/17/09 at 18:24:29

diamond jim wrote on 05/17/09 at 18:02:48:

marshall13 wrote on 05/17/09 at 10:27:23:

verslagen1 wrote on 05/17/09 at 10:16:05:

oops I forgot to take the square root. Embarrassed

d^.5=rpm x .000469009259 inches
1.19 @ 3k
1.37 @ 4k
1.53 @ 5k
1.68 @ 6k
1.75 @ 6500

So we are tuned for peak HP

ahh, much more similarity now...lol i got 1.2@152 inch length for 3k, 1.55@84.6 for 5k, and 1.75@63.5 for 6500.... what's the overall length of your longshot system, Jim?

It's 62" long. Pipe diameter is 1.75".

ok, so you're redline tuned... ill bet one of those dr650 9.5:1 pistons and Lancer's second grind bumpstick would add quite the afterburner to your ride.... but id really love to see what just tuning your spark would do.... the factory curve has got to be way conservative....

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diamond jim

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Re: Tuning intake and exhaust
Reply #13 - 05/17/09 at 18:34:52

I think it's about 9" longer than the stock can. Is the stock muffler ID 1.75"? Seems like it's 1.5". What rpm is the stock exhaust tuned to?

Also, with the lower compression of these engines isn't the spark already advanced a little as compared to a higher compression engine? If it could be advanced, would the line between power gains and increased heat be narrower on this engine than others? I'm familiar with advancing the spark on older engines with some compression loss to maintain but not advancing solely for performance gains. I must rely on y'alls expertise in that regard.

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marshall13

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Re: Tuning intake and exhaust
Reply #14 - 05/17/09 at 18:50:53

diamond jim wrote on 05/17/09 at 18:34:52:

With the lower compression of these engines isn't the spark already advanced a little as compared to a higher compression engine? If it could be advanced, would the line between power gains and increased heat be thinner on this engine than others?

higher compression can take more advance, usually, assuming a suitable fuel.... heat is controlled by jetting it rich enough it runs cool, that's what the plug exam tells you... you wouldnt be able to advance it as much as watercooled lung of the same size, but ill bet you could massage a few more ponies just by tweaking the curve... of course, the first step would be to put a CDI unit in it... the stock box isnt CDI, i thought it was, it makes the most sense, but it isnt... check the wiring diagrams... the coil is hooked to the 12v system... cant do that with a CDI, it can only be hooked to the box, or you get a high voltage spike frying all the diodes in the bike... so the iggy on this beasty is closer to a ford TFI (like a late 80s mustang)... unfortunately, adjustable CDI boxes cost a grand, or so.... though ill bet one could find a reasonable CDI spark intensifier used at a swapmeet... you'd still have the stock curve, but a way hotter spark... your perceived results from the kamikaze are actually more impressive with the pipe math... your power should be way low in the bottom end, and it isnt....

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