Larger airbox for big motors....fact or fiction?

[Steve S]

The point to take away is that displacement........as far as tuning length..........is a variable only in Helmholtz and in the table comparing the 1299 to the 1397 there are other variables at work, including camshaft duration and timing.

[Steve S]

This is organ pipe:

a sound pressure wave originates as the piston starts its decent and travels to the end of the stack and returns to the valve head wioth the goal of timing the return just as the valve is about to close. Example for 12,000 RPM

60/12000=.005 seconds= time for one engine rotation

.005*230/360=.00319 seconds of valve open time from TDC to valve closing at 50* ABDC

.00319*1116*12=42.7 inches of sound pressure wave travel during valve open period

42.7/4= 10.7" for second harmonic.........42.7/6= 7.1 for third harmonic.

There are several variations on this calc but do not vary that much. Again, displacement is not in the equation.

[PetriK]

Yes - agreed, displacement alone does not require intake manifold length changes - at least by all the tuning models. The interesting thing here is that how did Suzuki come up to intake lenght of 9.85" for stock engine (all short stacks, longs are about 1" longer ?)

From spec we know the following:
Power : (Claimed) 178hp / 132Kw @ 9800rpm
Torque: (Claimed) 138Nm @ 10200rpm

If I recall correctly the peak RPM many formulas is the Torque peak not hp peak. Anyway using this information 84000/10200=8.35"  we know that it is not the Simplified Chrysler formula that the Suzuki engineers used... as this formula would give us much shorter intake than what we have in the bike today ?

btw. sorry to the original poster to hijack this thread to discuss about all the intake components...

[PetriK]

Yes, organ pipe model gives 12.9" or 8.13" for stock engine if valve closing at 43degrees. (I am a bit unsure of the closing point.), but not the one the suzuki engineers used for this engine (at least directly for peak power).

[Busa Quick]

. The interesting thing here is that how did Suzuki come up to intake lenght of 9.85" for stock engine (all short stacks, longs are about 1" longer ?)
.

 You may know this but, they split the stack lengths to get some of their power at a lower rpm range and some at the higher rpm range. In a sense they made a cheap version of what Yamaha is doing with the R1 and R6. Also, as you found while cracking the ECM the fuel and spark maps were worked out to tune the bike to the different length stacks. If they would have gone with one length of stack we would have had more power in a certain range but, it would have been a more narrow band.


Mark

[Steve S]

Exatly Busa.

And unfortunately, we do not know Suzuki's design goals or their induction models.

We can get close but the tricky part is handling diameters, flares and eliptical shapes........and making assumptions about the speed of sound as a function of temperature.

http://www.sengpielaudio.com/calculator-speedsound.htm

[PetriK]

I would like to slightly disagree about the purpose of the dual stacks. We are seeing those also in gixxer racing version, but not seeing those in bikes where the stacks are in open air ... a more likely reason could be the fact that the belmouths are too close to each other and hence generate turbulence distracting the air intake (as described in Pretoria paper). The reason for map differences may be partially to compensate that but also to run the middle cylinders colder. The possible reason for the flap inside the box may be because of increasing the size of the hemholtz box - and hence some air filters may perform better because those affect the resonance differently than some others. A lot of uncertainities...

About the suzuki goals - not knowing those is not the preveinging further tuning the busa. Varying degree of different velocity stacks has been trialled out and always the short ones have yielded best results - but so far I have not heard anyone trying to go shorter than current airbox practicly allows. There has been attempts to run the engine without airbox, but as we know based on theory and practise that this approach will reduce the power.

Please convince me with some facts not to cut the intake port shorter in an attempt to have the peak power at around 10500-11000rpm with 1397 including a slightly larger airbox - otherwise the head will be processed on monday just for the sake of trying out something new

[396]

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[gazza414]

Good to see you having a go Petri with the data you have it is fair to say the trend is shorter and larger in the box...also why not run no air filter?

CrazyBill a year or more ago ran gixxer1000 t/b's on his or a customer's Busa..in order for that to work they "relocated" the CL distance of the port to port distance......so thats an issue in itself , however the t/b's from a gixxer 1000 or the like may be shorter...they also have 2 injectors which could be beneficial?

all the best with your project....and I bet you wish you had an engine dyno now!!!!

[PetriK]

I keep hearing that running without the airbox reduces power. Again, it will depend on YOUR specific combination. I know for a fact that one combination makes more power without the factory airbox than with it.

Would be very interested in to know more about the engine specs of that ...

CrazyBill a year or more ago ran gixxer1000 t/b's on his or a customer's Busa..in order for that to work they "relocated" the CL distance of the port to port distance......so thats an issue in itself , however the t/b's from a gixxer 1000 or the like may be shorter...they also have 2 injectors which could be beneficial?

Yes - wish for more tools and more accurate data from previous experiments. For example, my friend tested gixer TB:s and removed the secondaries, in his combination taking the secondaries axle off reduced the power ;-o? Therefore we disregarded that option. Also reshaping the internal surface of TB:s reduced power in his combination. On the other hand we ran a set of gixer TB.s in Yamaha YZ 1K engine without airbox installed in Minicooper, that made very decent power. Slightly modded Busa with very big bellmouths (appr 2.5") and std airbox has made the best power so far I have seen, but those bellmouths reduced the internal diameter of the TB so it could have been because of increased velocity in the TB rather than the bellmouth design itself. On side car class with Gixer engines they are running airboxes which are ram air only, not with plenum - on top of the European level. Busa has only 9L airbox, the ZZR1400 has 17Liters airbox, even that is still not perfect and can be improved with simple modifications for a bit more modified ProStock bikes - we know that from the dyno. None of these things were not known for sure before trying these out in real world. So everyone chooses what works for them ... based on trial and error.

The funny thing is that with computer aided modelling so far with three different sw models all are indicating gains with shortening intake and enlarging the airbox. Here on this board I have not heard anyone voting for this - just nay:s ?

Based on this conversation I gather that shortening the intake port and enlargening the airbox for 1397 with extended RPM/reflashed ECU has not been tried out for real before - or ?

[Jonny Hotnuts]

btw. sorry to the original poster to hijack this thread to discuss about all the intake components...

For me this entire thread has turned into some of the most interesting reading I have seen in a long time.

I am thinking now that if I had time and money I would like to f- around with the idea of a tunable 2 chamber airbox that would use a vacuum actuator to change the box volume based on rpm.

Speedweek is only 4 months away……
The car still needs a skin on the nose and the new 1507 installed…..
Not enough hours in the day and I want a magical airbox…..

[396]

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[396]

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[PetriK]

I am thinking now that if I had time and money I would like to f- around with the idea of a tunable 2 chamber airbox that would use a vacuum actuator to change the box volume based on rpm.

What Ive seen the plenum does not need to be in shape of the box, e.g. porshe has patented a plenum design were the plenum is in shape of tubes which are opened and closed for a certain RPM area. That design is freely avail from e.g. freepatentsonline.com, sorry dont recall the number. As you may know the busa Flapper valve can be reprogrammed to open / close at any RPM so it allows various designs to be used. Ford is using variable lenght manifolds, i.e. one straight tube and another curved longer tube. There is enormous amount of info avail just by reading the patents from this area.

car

Car as a car or car as a sidecar ?

This one http://www.paivarintasidecar.fi/bike.htm is running a straight ram air box without a plenum. Last season they ended Superside (world champ) no.2 so I do agree that a closed airbox design is not always needed . And no epoxy was used in porting of this gsxr1000 head ... btw and ot, the gixer head looks so small compared to busa when next to each other. Also the pistons are so tiny ... I wonder what is the actual volume of gixer normal airbox, have not really paid any attention to that earlier.

[Jonny Hotnuts]

car before run


car in impound




Pics of the car today.
We had a serious handling issue last year preventing us from going faster than 130.
THis year we are running a no compromises 1507 (turbo motor next year) and decided to stretch and narrow the cars front to the class limits. 4 months till speedweek and you can bet it WILL be done

[PetriK]

That one looks really nice one ! Must be a rush to ride Looks like something that could do wheelies as there is virtually no weigth in front until air pressure starts to push it down.

About the airbox position if that is the one on top of the car - reminded me about airfoil design. The airfoil inlet is usually put in to the place where the pressure is highest, very close to the nose to generate maximum pressure to the intake. Never at the back half of the wing where the air is turbulent and generating lift. On that sidecar the airbox intake is put into the place where the pressure is at peak if you look at the design when covers are on.

[gazza414]

Petri, how will go about evaluating if the shortened inlet tract has or has not been beneficial ? or a uselfull or useless exercise?

[PetriK]

Petri, how will go about evaluating if the shortened inlet tract has or has not been beneficial ? or a uselfull or useless exercise?

Today I started to build the airbox for increased volume and better fit for shorter manifold, added volume seems to be around 0.6L. Regarding that I am a bit worried about glassfiber sticking to the plastics well enough. I am not only dropping the stack area but also reshaping the air entry area based on some flow analysis with a 700cfm blower and air speed gauge. Not very scientific design, but just believe that both airbox intakes should be directed upwards a bit more separately.

The head will be machined early next week for -0.40 shorter intake port. Engine will reassembled some time late next week or weekend. Then tuning and dynoing for another week. We shall know in a couple of weeks.

I will know if its usefull by hitting the calculated figures, the difference is so big - around 5-6hp putting 1397 almost on par with 1464. I have two desktop dyno modeled reference engines with known real dyno data to compare the results with (1397 and 1464). If its useless will be using all long stacks or possibly the Factory pro stacks instead of all shorts, if its usefull will be cutting additional 0.20" from the short stacks. We already know that all longs and factory pros will not give more peak power with higher rpm on alike engine configurations based on earlier testing.

Of course to be absolutely sure a more scientific approach would be needed - but this is the best I can come up at this moment so additional suggestions are appreciated as always.

[Jonny Hotnuts]

Regarding that I am a bit worried about glassfiber sticking to the plastics well enough

De-glaze the plastic by using an abrasive brush, flap wheel or grinder of some sort. The epoxy will stick fine to the plastic if you do this.

I am interested in pictures......

[Busa Quick]

Regarding that I am a bit worried about glassfiber sticking to the plastics well enough

De-glaze the plastic by using an abrasive brush, flap wheel or grinder of some sort. The epoxy will stick fine to the plastic if you do this.

I am interested in pictures......

 +1

 A wire brush wheel on a electric drill will leave a nice tooth for the fiberglass to grab.


Mark

[PetriK]

First  - thanks to DF to confirm that the original intake port lenght I measured is propably the correct one. Then after finding the thread of Experimental TB project thead on the mods section the brains started to work again... http://www.suzukihayabusa.org/forum/index.php?topic=128350.0

If we put the discussion of which method is best for calculating the total intake lenght aside (went through many of the speedtalk postings of it too, and could not find a definite answer exept many using pipemax) and just stick to pipemax calculated results, this is what all this sparks off as an outcome of a thinking process.

The intake TB bottom is 4.7"+0.46" from the valve. That is 7th harmonic for 7800rpm and 5th harmonic for 10800rpm. Now if that distance is shortened by 0.4" then that is 7th harmonic of 9800 and 5th harmonic for 11550.

If we assume that it was partially intentional for Suzuki engineers to leave the TBs so that the waves are reflected back from the bottom of the TB then as this engine is supposed to run up to 11500 the induction path when shortening the port with 0.4" will put the induction harmonics in sync with the new RPM targets.  This also may partially explain why varying stack lenghts have not yielded estimated results as the wave reflection point is the bottom of the TB? This may also partially explain why the TBs which are drilled from the bottom to +2mm larger diameter will work better with some engine configurations due to less wave reflection surface ?

Maybe too far fetched - but just something that occured into the mind.

[Jonny Hotnuts]

What would the wave be reflecting off of?......I could see it being the back of the butterfly at idle but at WOT there is no surface to reflect from.....

The 1/8" lip on the bottom half of the back side of the TBs that I shaved off certainly would not reflect a pulse wave, and the taper of the TB would cancel reflecting waves.

I must admit that I wish I had a reason that Suzuki (or Keihin) opted to have a large transitional difference on the backside of the TB into the intake boot, while the rest of the intake track is dead smooth. My logic says that there is no way that a transitional gap would help HP and should cause a separation of the boundary layer and would hurt HP…..but there was some REASON it was there even if I can’t understand what it is.


BTW:
I will post a pic of the finished TBs soon.

[gazza414]

After building such a sweet V8 Busa , do you think these engineers lost sight of looking at the design for the airbox ?



on song

[PetriK]

After building such a sweet V8 Busa , do you think these engineers lost sight of looking at the design for the airbox ?

I like the redish colour on the exhaust...

Unfortunately the picture of the plenum does not clearly indicate the design. But it looks to me that they have dual TB:s before the plenum. That restricts the plenum size and design as to keep the throttle response good the volume of the plenum can not be as high as with an airbox before the TB:s. There is a few quite good articles in freepatentsonline.com about plenum design particularly for V type engines which I am sure everyone buildling this kind of engines has looked into. Running the two separate engines in sync is also setting special demands to the engine control unit - wondering which approach they have taken.

The other interesting thing is the exhaust. Looks like they are using tapered pipe about 50cm (19"-20") and then 4-1 collector. When simulating different exhausts with EAP, so far I have found nothing that wins the 4-1 design with a megaphone.

Gazza - do you know these guys to get more specs just for curiosity ?

[Jonny Hotnuts]

http://www.jakelatham.com/radical/projects/engine_conversion/2008.03.11_done1.jpg

http://www.jakelatham.com/radical/projects/engine_conversion/2008.03.11_done2.jpg

Check out this busa airbox.
As of last night I purchased 25 square of CF to build an airbox for my car (just going to skin the outside of a glass box so it looks like CF!).

One reason is that we have determined that an airbox with larger volume should help HP. THe second reason is because if I can make the box wider and lower than the current busa box I can extent the sheet metal engine cover to loose some of the low pressure area behind the rear window of the FIat.....and this should help aeros without looking like I am trying too hard to change flow or alter "contour".