Cross/corner weights

[Muzz]

Hey guys im interested to know somthing reguarding crossweights.
Say there a 2 cars exactly the same, say 1000kg.
car1

300kg 300kg ----front



200kg 200kg ----rear

Car2

275kg 325kg ----front



175kg 225kg ----rear

Both cars have a cross weight of 50%, however the left side of car 2 weighs 100kg less than the right, would this be a disadvantage in handling, even though the crossweights are the same between the two cars?

[JasonGilholme]

I'd say so, but i doubt it'd be noticeable.

Most cars will look like this due to the driver being in the vehicle.

[Muzz]

Choosing an engine for a track only car, im choosing between a k20a2 or a b18c, but the way the k20 sits reversed in the (civic) engine bay looks like it put alot of its weight over the drivers side front wheel (along with the driver and seat).
Whereas the b18c seems like it would sort of counteract the weight of the driver+seat, to give a more equal left right ballence after the crossweights are set.
http://i106.photobucket.com/albums/m263/muzz1987/62.jpg
http://i106.photobucket.com/albums/m263/muzz1987/15.jpg

Id prefer to go k20, but if it reduced cornering ability, even slightly, id probably stick to the b18c. Can anyone say if the difference be noticable at all?

[MaskedAP1]

u also need to corner weight the car with the driver in, and see how the result is.
generally speaking, as long as it nears 50/50, the handling should be fine.

[Moya]

Couldn't you adjust each corner's coilovers to compensate? And I think the hp the k20 offers would make the slightly weight difference irrelavent wouldn't it?

[MaskedAP1]

play/adjust coilover setting and swap diffferent set of spring with different spring rate are nothing to do with weight, but yes, it will help for better handling if you got the right setting for your purpose.

one side note, the whole weight of a K20A or K20A2/3 plus tranny is around the same weight as B18C motor plus tranny, but the weight distribution of motor itself are different.

[aaronng]

Adjust the individual height of the coilovers so that the sum of the opposing corner weights are equal. It won't be as good as perfect weight balance, but it does help.

[Slow96GSR]

There are a few ways to set your corner weights. You can set it through the coil over by pushing up and placing weight on to the other corners. You can adjust the position of the motor. You can change where parts are placed inside the car. Also the only way to properly do it is on a set of scale pads and the driver sitting in the car. You can use sand bags but the drivers mass is spread out from the seat. On our formula cars we can set corner weights about 4 more ways but then you get in to some serious money. On the Honda just do it with the coil over and motor placement. It's the easiest.

As for will it help a cars handling? Yes, it will depend on the car, track, and driver. Also tire compounds and temps will determine what weight goes where. You are adjusting to allow or help tires grip and the car keep traction. So if the compound is stickier then you don’t need as much weight on the problem corner. It wouldn't really do much for a straight track car or a road course as much as a circle/oval track. Road courses tend to have as many lefts as they do rights, so we tend to set weight pretty even left to right or if there is a bigger need in a specific turn or set of turns we can set it up for that. We are now working with Penske for in car adjustable struts the will be affordable to all teams so that it may be legal to use on those type of cars. The IRL teams already have a system like this. Tien makes a in car adjustment system but it isn’t quite up to par or as easy to adjust in small amounts that we would need. On average ¼ turn was about 10 pound moved to the opposite corner.

If you are doing road course or circle/oval consult a Penske rep to help you decide on a system that will work for your application. If you need something for specs, like what to run in what situation, consult a race tech that does track side support or prep.

You can also Google, Yahoo, Ask Jeeves, or try the IRL site for car specs. SCCA also might have some tech pages. I can't go to far into detail about our cars as then we get in to contracts and provisions than make us keep quite.

http://www.elephantracing.com/techtopic/cornerbalance.htm

http://fmgracing.com/racing101.php

http://www.grmotorsports.com/news/012005/understanding-corner-weights.php

http://www.enjracing.com/terminology.htm

PM me for more or any more questions about car prep at tracks. We have LISTS!!! I'll also find some pics I can show you all.

Edit---> Pics!

This first one is of the front motor mount on a Formula Ford 1600 (FF1600). The hex bars connect directly to the frame with tie rod ends at the other ends. This allowed for up to 20 pounds moved from side to side, front to rear, or criss cross. It was the first one done on these cars and was more of a vision we had at the shop. Made setting corner weights so much easier and mounting the motor easier. We didn't know it would work so well. I am sure other teams have done this but not on this small of a car.

http://www.strathlan.com/CMS/images/SCCA/mainmotormount.jpg

The second pic is not one of our cars so I have a more detailed picture. It shows how the rear on these cars is set up. Pretty much the same all the way up, from the small formula cars all the way to the F1 cars. You can see that by pushing the triangle assembly with the strut the forces push the tie rods connected to the hub to push the A-arm assemblies to raise or lower the car in that corner. This will change corner weights on all sides.

http://www.strathlan.com/CMS/images/SCCA/rearsusassy.jpg

[Dylanamus]

Hey Muzz, what classes etc do you plan on competing in? The better power output of the k20a has a lot to do with more torque from the extra 200cc. Also take cost into consideration. You could do a fair bit of work to a b18c (non type R) and make it considerably better than a b18cR for a lot less than a k20a conversion. If the b18c is also going to provide better weight distribution, as well as be more financially economical and place you in a lower capacity class, I'd go with that. Not quite answering your question hey, but just thought I'd share my views :) I guess it depends on what your end goal for power is. Most people I speak to about their track cars are more concerned about saving up for changes to their handling then chasing extra power.

[Muzz]

Not quite answering your question hey, but just thought I'd share my views :)
Views are much appreciated!:)


Most people I speak to about their track cars are more concerned about saving up for changes to their handling then chasing extra power.

Yeah thats my main focus, best possible cornering ability, either engine would do fine.

[Dylanamus]

Well in that case man, my personal choice would be the b18c. For the weight distribution for one and for the financial savings aswell. You could use the money you save on the b18c to customise your gear ratios and switch in a circuit proven LSD. Sure, we all know about the technological advancements implimented in K series engines, but at the end of the day there is nothing inadequate about the b18c.

I'll honestly say that I doubt the weight distribution from the K would have a HUGE negative impact on cornering (and you could probably centralise the engine placement a bit more with some costly custom fabrication and relocating), but if your ultimate goal is NOT to build a relatively high powered engine and to focus more on perfecting the handling at whatever power output you end up with, then I say the benefit having more $$ to finance the areas you are more interested in addressing, strongly outweighs the advanrages of having a K series engine.

That's my long winded way of saying a k20a swap will probably cost you close to $20k to do properly, compared to $10k or maybe less for the b18cR. $10k is a huge premium to pay for power potential when you don't intend on fully embracing it.

I wish I was in your position haha I'll be interested to stay tuned in on your project's journey. :)

[Muzz]

yeh, great points there, at heart i know a b series is what i sould get. ks are to dam expensive, especially considering how much will be going into the chassis and suspension!

Hehe my projects journey will be long one! im 3 years away (waiting to i finish mech. engineering degree) from stripping the car to its bare bones to build up into one fast circuit machine, this is my 10 year goal! I got 3 years to plan and learn as much as i can.
Im currently designing an adjustable angled diffuser for the EK chassis, with help from johnny mac from honda-tech, who has studied fluid mechanics in aerospace engineering. Ive already designed the front splitter and airdam combo (which is also adjustable in height and rake), and am not far off from completing the lightweight underbody tray and sideskirts. Basically a complete ground effects downforce kit.

[Dylanamus]

There are a lots of people dreaming about K series when they would actually be better off with a b18c. K is like the flavour of the year - and it's definitely not just a fad: it's a damn good package, but hey even if you are loaded you should still base your financial decisions on the most cost effective way to achieve your goals.

Hey fluid dynamics is one hell of a complicated subject! I was trying to get a friend of mine who is completing his sponsorshiped PhD in aerospace engineering to help me on a similar project, but it's so much work that he'd need to dedicate months or maybe years to get it done right and well... it's not his car that would benefit in this scenario hehe

If you need another car to play dress-ups with, just PM me lol And good luck with the whole thing. Good to see you're happy to spend so much time researching and planning. One thing I've learnt is that retrospect is a biarch.

[Muzz]

Hey fluid dynamics is one hell of a complicated subject! I was trying to get a friend of mine who is completing his sponsorshiped PhD in aerospace engineering to help me on a similar project, but it's so much work that he'd need to dedicate months or maybe years to get it done right and well... it's not his car that would benefit in this scenario hehe



Yeah sure is, I had no idea how complicated it all is. I made my plans, had everything worked out, then i went and emailed my plans to Johnny mac, and found out how extreamly complex 3d air flow really is! While he is extreamly happy to help me out and answer my questions, and point me in the right direction, he has no time to actually help me out on the design (which i had to basically redo).
Designing somthing like this is to get the maximum performance out of it is extreamly hard, if not imposible without the use of a wind tunnel, and LOTS of time. I was recomended to look at different SAE case studies and designs for other similar cars and work from there to get a good working design.

Ive designed my entire kit to be completly adjustable, from the height from the ground of the splitter, the height of the front of the underbody tray, the height of the rear of the underbody tray (which also allows the rake angle of the tray to be altered), the ability to easly change the side skirts design and height, the height from the ground at the diffuser opening, and also the height at the rear of the diffuser (alowing angle change), ill also be testing a few different diffuser designs.
All i can do is test test test, until i find the optimal settings using different testing methods.

Once i find the optimal settings and diffuser design, ill redesign it and remove alot of the adjustability (keeping the ability to alter diffuser angle, and the ability to replace the sideskirts easy incase of to much scraping etc.)
Hopefully ending up with somthing like this
http://i106.photobucket.com/albums/m263/muzz1987/11.jpg

http://i106.photobucket.com/albums/m263/muzz1987/yellowcivic6mp.jpg

[Dylanamus]

Definitely exciting stuff there. Patience is a virtue (that I wouldn't have in your position hehe). I hope you log your progress in a thread with photos, CAD files, geometry calculations and a home address to where you will be storing the whole thing etc :) hehe Photos and a log would be good if the rest is asking too much :P