MikeCapon
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| posted on 29/1/08 at 02:00 PM |
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BEC sumps and airboxes
As a complete kit car novice but with some experience of using bike engines in competition, particularly with sidecars there a couple of things
I'm having trouble understanding. Perhaps someone may care to enlighten me.
1 Everyone (except dry sumped motors) seems to be using the standard bike sump. In the F1 sidecars we race we use a custom wet sump which is about
20mm thick and hence enables us to drop the motor right down, maybe 60-70mm lower. The handling advantages are obvious and at the same time, we carry
a little more oil than the standard sump with no surge problems (we use a baffle plate inside).
2 The airbox on the motor has proven to be critical to its performance. Any leaks in the airbox or feed pipes completely kill the driveability,
throttle reponse and the power output of the motor. You guys all seem to be using stone-age type foam filters hanging out in the open, often requiring
bonnet cut-outs. Can you see how these two subjects are related? Has anyone run a real airbox and what are the results.
PS Dyno runs can be a little misleading as there is no ram-air effect or cold air rushing in to keep the intake charge temperature down.
What do you think?
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Phil.J
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| posted on 29/1/08 at 03:12 PM |
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I would never run a standard bike sump in a car for the reason you state ie a lowline sump enables you to get the engine much lower in the chassis
with a very positive effect on handling.
The bike air boxes in my experience seem to have no measurable effect on performance if the mixture is corrected. Even when set up optimally I believe
a ram air system is only worth around 1-1.5hp which is secondary to the packaging problem on a road car.
[Edited on 29/1/08 by Phil.J]
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Hellfire
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| posted on 29/1/08 at 03:23 PM |
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Most bike engines require a modified sump when fitted in a BEC, basically to reduce the overall engine height and at the same time give reasonable
ground clearance. This is usually done by cutting down and re-welding the original sump pan.
The original airboxes do generally give better performance over a foam filter but again, it isn't always possible to fit the airbox under the
bonnet, therefore people resort to foam filters and a rejet/remap.
In most BEC's you are unable to reach the speeds necessary to see the effects and benefits of a ram air system.
PS - Most professional dyno's I've seen do feed a cold air supply to the rad.
Phil
[Edited on 29-1-08 by Hellfire]
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nitram38
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| posted on 29/1/08 at 03:28 PM |
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On my Motaleira, I am running a standard airbox as I have been told that they are designed around the airflow and do affect the performance.
On a 7 this is not practical for two reasons, one being height and the other orientation of the engine.
I have my engine facing forwards and I have ducted the inlet to the airbox via 2 X 3" hoses and 2 X NACA ducts mounted each side of the car.
Hopefully this will help with a bit more "ram-air".
I also agree that rolling roads do not provide moving cold air into the airbox in relation to speed, but then neither will the sva man when he does
the emmissions test.
For these reasons I am fitting a power commander (injection) and an Innovate lambda gauge kit.
This will give me the option of an sva map and the ability to "live tune" the engine while driving.
PS. I also have some R1 sump baffles to fit 04-08 engines
[Edited on 29/1/2008 by nitram38]
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smart51
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| posted on 29/1/08 at 03:46 PM |
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If you take the airbox off and fit a foam filter, you need to rejet the carbs or remap the fuel injection to suit. It will then run just fine.
The tuned airbox resonates at a frequency chosen by the designer (usually around 1/3 of max revs). This extends the usable range of the engine or
fills in a gap in the torque curve. Factory airboxes do restrict airflow a bit at high revs, at least my 98 R1 box does.
I made my own airbox, tuned to smooth the sudden increase of torque that occurred at 5000 RPM. It works beautifully. I jetted the carbs up from 132
stock to 150 during a rolling road tuning session. The guy said it now makes 152 BHP.
A foam filter, correctly fueled, will give more top end power, without airflow restrictions, but will generally give a bit less torque in the 4000 -
5000 RPM region.
Foam filters are loud. Airboxes slightly less so.
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MikeCapon
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| posted on 29/1/08 at 04:04 PM |
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This is the type of airbox I'm talking about. As you can see its not huge and believe me it really works. In terms of max hp its probably only 10
or so hp but the driveability is so much better its not true. The airbox is fed by 2 NACA ducts abd 75mm ducting. Same as nitram.
What is really important is a complete seal from NACA duct to airbox. These photos are of the box under developement. The final design of the box
itself was the same but with another system to marry the ducts in the bodywork with the airbox.
As for the foam filters being more powerful I believe that this is the same as taking the baffle out of your moped exhaust when you're 16. It
seems faster because it's making more noise, but most of all, the mid range is so rough that when it eventually runs clean it seems to give a
real kick.
[img][/img]
[img][/img]
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athoirs
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| posted on 29/1/08 at 04:28 PM |
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Hi
That’s a very small air box! I am sure it works well - are there any photos of it so we can see how they have baffled it?
Of course you have to think also about the exhaust design as well. Most for us have not got the time and money for optimum performance but any advice
or input is much appreciated as I am sure there was a lot of development work there.
I mean a sidecar is just a bec with three wheels!
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MikeCapon
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| posted on 29/1/08 at 04:36 PM |
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Yes it is small but I promise you that it works. Why do I always find myself saying that? The interior is without baffles. The very latest box for
which have no photos yet is about 20% greater volume and works even better. Again no baffles. The only other thing we have added are two more NACAs
nearer the front of the body work in cleaner air. The bike in the photos has won three French championships and a GP. I realise you guys don't
want the last 0.1HP but it's good to follow principles that are proven for particular types of motor.
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Hellfire
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| posted on 29/1/08 at 04:48 PM |
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That's a very neat looking airbox. Have you designed and built it yourself?
Phil
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athoirs
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| posted on 29/1/08 at 04:59 PM |
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Oh just one other question, Does it have a filter and is so what type Oh thats two questions ah well..
I agree with using best principles.
[Edited on 29/1/08 by athoirs]
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Puk
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| posted on 29/1/08 at 05:05 PM |
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Hi Mike - can I ask you a question about the R1 sumps that you mentioned? How does their design differ from sump as supplied by Yamaha - is it merely
cut and shut to reduce its depth, or is anything more done to restore the oil volume?
Cheers,
Chuk
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
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MikeCapon
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| posted on 29/1/08 at 05:12 PM |
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Thanks Phil, We made this airbox but pretty well copied the constructor's airbox. To be honest, with the standard bodywork there's not a
lot of choice in terms of shape and volume. Our new airbox has modded bodywork to go with it and is around 20% bigger in terms of volume. We also now
have the space to fit a second row of injectors spitting straight into the bellmouths.
Er, no there is no filter. You see it was just one question! For a road car a filter would be nice sandwiched between a two part airbox leaving the
greater part of the volume between the filter and the bellmouths.
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MikeCapon
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| posted on 29/1/08 at 05:17 PM |
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Hi Chuk,
These pics and most of my experience is of Suzuki 1000 GSXR motors but the R1 would be pretty much the same. The sumps we use are machined from solid
billet and simply replace the original part. We win back oil capacity because the OE sump has a deep "valley" with oil and pick up near
the bottom. We carry oil for the full width of the sump and that works for us!
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Jon Ison
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| posted on 29/1/08 at 05:30 PM |
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The knocked together ally air box that was a get me by until something better came along worked so well on the dyno its still there 5 1/2 years
later.
Personally I wouldn't go foam filter either, people that seem to know tell me they don't work well particulary on bike engines, and
trumpet socks ? Filter next to nothing and hinder power ?
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smart51
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| posted on 29/1/08 at 05:39 PM |
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quote:
Originally posted by MikeCapon
The airbox is fed by 2 NACA ducts abd 75mm ducting...What is really important is a complete seal from NACA duct to airbox.
As for the foam filters being more powerful I believe that this is the same as taking the baffle out of your moped exhaust when you're 16.
Foam filters give more top end BHP than a stock airbox as measured on before / after tests on rolling roads. It is not illusory.
As for your airbox, I suspect it is the NACA ducts that are giving much of your benefit. The airbox, together with the seals, merely stop all the
good work of the ducts being lost.
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MikeCapon
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| posted on 29/1/08 at 05:41 PM |
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Bike engines seem to enjoy breathing cool, stable air. Foam filters don't do that and as for trumpet socks they filter very little and block
very quickly. Once blocked there is every chance that the motor will eat its own socks! Eugh. The only use for socks apart from putting on your feet
is in sandy conditions where a sock (Sandstop)over the filter element keeps the sand out, or tries to.
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itiejim
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| posted on 29/1/08 at 05:45 PM |
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My car has a foam filter sat on top of the carbs, it really is an awful affair, it's so close to the bonnet that the foam actually gets squashed
to fit under.
I really need to make a decent fibreglass airbox - so any design tips would be appreciated!
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smart51
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| posted on 29/1/08 at 05:54 PM |
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quote:
Originally posted by itiejim
I really need to make a decent fibreglass airbox - so any design tips would be appreciated!
Look for posts by me when I made mine.
tips:
put bell mouths on all your intakes (carbs and airbox)
make sure there is at least 1 and better 1.5 times the carb diameter between the bell mouth and the wall of the box.
get the volume of the box vs length of inlet pipe vs diameter of inlet pipe right if you want the box to work well.
I found that a box inlet pipe of 3.5 times the area of each carb had no restriction effect on air flow but that smaller inlet pipes did affect the top
end.
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ChrisGamlin
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| posted on 30/1/08 at 07:36 PM |
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quote:
Originally posted by MikeCaponThese pics and most of my experience is of Suzuki 1000 GSXR motors but the R1 would be pretty much the
same.
The R1 (pre 2004 anyway, not sure on later engines) are a little trickier to shorten the sump because the cast pickup pipe sits at an angle, so you
can't shorten it without also changing the position of the pickup away from the middle of the sump. Im sure its still do-able but it would need a
custom pickup fabricating from scratch I'd think.
Chris
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