Well after 9 months of an insane amount of work, it is finally running and testing has begun (yes the competition is in 10 days) After the first few drives on some fairly bumpy pavement we found out that we designed a beast…. This car is a hand full to say the least and I need some advise as how to calm it down a little.

Any and every bump the car hits the front end tracks hard making it very touchy in the straights. Inherently a purpose built car will be touchy as hell with a half turn lock to lock rack, but I am wondering how I can properly increase stability in a straight line and longer sweeping corners.

The initial set up was not ideal, just wanted to get the car running under its’ own power. I ran zero toe front, slight toe in rear. My thoughts to increase stability are changing caster to 4-5 degrees. Zero toe front, 1/8 toe in rear. -2camber front, -1.5 rear. I am just wondering what you guys would suggest so that I am starting in right direction and do not waste valuable test time.

Lucky I will have access to a nice set of scales to do a proper corner balancing this week. If you guys have any questions about the car feel free to ask.

here are a few pics of the car we designed...

Edit: looks like a fellow teammate/honda-tech junky made a post about our car, so additional pics can be seen here... https://honda-tech.com/zerothread?id=1239487





-nate


Modified by Nate at 8:58 PM 5/8/2005

 

I don't have any advice towards your troubles, but that thing looks fun as hell. Whats the engine setup?

 

we run a honda CBR F3 engine. with a 20mm restictor. The engine puts out about 70hp and the car weight is 480lbs so that is about 6.8lbs/HP. It is pretty quik!

 

More Caster.
Try to increase up to 7 deg incrementally and see how it goes.
Make sure you do bump steer everytime you change it.

 

I also agree with more caster. Have you checked the bumpsteer at the current suspension settings? Is the steering wheel kicking back with the bumps? Any chance the lack of stability is from the rear steering the car? What kind of toe change does the rear suspension have with up/down travel?

 

thanks for the help guys, bump steer measurments are next on the list. Did not have time to make a proper bump steer graph today. But minimal bump steer was designed into the susp. just have to check the actual values.

-nate


Modified by Nate at 10:08 PM 5/7/2005

 

have fun competing against NC State's car this year...

i checked out their new setup the other day... wow!

 

I think the twitchiness is coming from lack of stability in the rear. The quick ratio steering and roll stiffness are just magnifying it. The 2004 car is probably just as twitchy over bumps, tho its soft spring rates probably hide it.

Align the rear, dial down the shocks, and it should calm it down.

Of course we need to get the new axles in it before we can test that....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hunter &raquo;</TD></TR><TR><TD CLASS="quote">have fun competing against NC State's car this year...

i checked out their new setup the other day... wow! </TD></TR></TABLE>

yeah some of the teams resources (money and man power) is amazing. I think we rock out with our extremely small team of 10 people, and a tiny budget.

-nate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BUJonathan &raquo;</TD></TR><TR><TD CLASS="quote">I think the twitchiness is coming from lack of stability in the rear. The quick ratio steering and roll stiffness are just magnifying it. The 2004 car is probably just as twitchy over bumps, tho its soft spring rates probably hide it.

Align the rear, dial down the shocks, and it should calm it down.

</TD></TR></TABLE>

I was thinking a problem could exist in the rear as well, but I would still try and see what you get at the front with an easy caster change before you get really into it out back.
Good luck!

 

The project looks nice. Good luck

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nate &raquo;</TD></TR><TR><TD CLASS="quote">we run a honda CBR F3 engine. with a 20mm restictor. The engine puts out about 70hp and the car weight is 480lbs so that is about 6.8lbs/HP. It is pretty quik! </TD></TR></TABLE>

Did you guys convert to FI at all?

If not, what modifications do teams generally do to the stock carbs to make them handle the type of loads these cars usually see?

edit: N/M I just looked at the picture. to me.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr Hammond &raquo;</TD></TR><TR><TD CLASS="quote">

Did you guys convert to FI at all?

If not, what modifications do teams generally do to the stock carbs to make them handle the type of loads these cars usually see?

edit: N/M I just looked at the picture. to me.</TD></TR></TABLE>

There are defiantly teams with F/I, which is not the easiest task, but we just convert the motor to fuel injection and get the car nice and tuned. The big change we made this year was to use a CVT, this is not common at all and should be interesting to see how it performs. (it is fast for sure!)

as for testing the newly adjusted suspension... we broke an axle yesterday.. lets hope we get ever thing together and tested some more by competition.

-nate

 

Do not run 0 front toe, if you have decent ackerman, start with 1/16 out, total. Going thru 0 toe on 1 wheel bumps makes for Twitchie car.

 

Also why a push-rod front and pull-rod rear? If one has a more progressive rate than the other it will be hard to tune for diff. speed corners.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">Also why a push-rod front and pull-rod rear? If one has a more progressive rate than the other it will be hard to tune for diff. speed corners.</TD></TR></TABLE>

the main reason was packaging issues. But all motion ratios were calculated and modeled for proper suspension travel. So they have the same ratio.

thanks for the advise!

-nate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nate &raquo;</TD></TR><TR><TD CLASS="quote">There are defiantly teams with F/I, which is not the easiest task, but we just convert the motor to fuel injection and get the car nice and tuned.</TD></TR></TABLE>

What made it difficult to convert to FI?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr Hammond &raquo;</TD></TR><TR><TD CLASS="quote">

What made it difficult to convert to FI?</TD></TR></TABLE>

To put the motor in the car, meet rules, and convert to fuel injection, you have to develop a 20 mm restrictor, fabricate an intake manifold, fabricate an exhuast, fabricate a throttlebody, get some fuel injectors, redo the entire fuel system, make a new wiring harness, and develop enigne maps. That's enough work to keep someone busy...

 

FI is hard cause the restrictor is before the turbo which makes problem with the seals. Cornell solves this buy spitting the turbo casing and making and extended shaft and making two seals ones that work on vacum and the others that work on boost, so there is not proble with the seals.

we used a CVT when we went to detroit two years ago (Concodia University) but we use a Polaris engine and did not have the manpower or machine tire to get a CVT on a CBR.

That is the best setup, good luck.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BUJonathan &raquo;</TD></TR><TR><TD CLASS="quote">To put the motor in the car, meet rules, and convert to fuel injection, you have to develop a 20 mm restrictor, fabricate an intake manifold, fabricate an exhaust, fabricate a throttlebody, get some fuel injectors, redo the entire fuel system, make a new wiring harness, and develop enigne maps. That's enough work to keep someone busy...</TD></TR></TABLE>

I thought everyone had to run a 20mm restrictor and 19mm for alcohol. Well you wouldn't necessarily have to develop all these parts. Why not just use pre-made ones off of a FI bike? Perhaps an F4i or 600RR or I guess really any fuel injected 600cc engine you could probably use.

You'd probably have to fab a plenum for the carbs anyways. Exhaust manifold is fabed anyways. Find a t/b to work, find injectors to work, change fuel system to meet high pressure (no biggie). Fine tuning would take some work, but converting a carburetor engine to use fuel injection, especially one that has readily available parts because it has already been done, wouldn't seem terribly difficult. I'm not trying to say I could do a better job. I understand the time consumption it would take to do this. I was more wondering what problems they incurred while doing this.

I was just wondering. When I saw CBR F3 engine, I knew they were carbed. The types of forces these cars would exert would probably give you fuel starvation problems with that type of carb set up. Which is why I asked if he switched to FI. Then I looked at the picture and noticed they did.

He mentioned it wasn't an easy task, but then said they did it, so I was wondering what complications they ran into doing so, besides the obvious fabrication points listed above. Obviously you need the parts and you need to install them, and this will be timing consuming, but were there any snags in doing so along the way?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B HATCH &raquo;</TD></TR><TR><TD CLASS="quote">FI is hard cause the restrictor is before the turbo which makes problem with the seals. Cornell solves this buy spitting the turbo casing and making and extended shaft and making two seals ones that work on vacum and the others that work on boost, so there is not proble with the seals.

we used a CVT when we went to detroit two years ago (Concodia University) but we use a Polaris engine and did not have the manpower or machine tire to get a CVT on a CBR.

That is the best setup, good luck. </TD></TR></TABLE>

Oh wow I didn't even know "Forced Induction" was allowed. I was talking about "Fuel Injection" though. Sorry for the confusion.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr Hammond &raquo;</TD></TR><TR><TD CLASS="quote">

I thought everyone had to run a 20mm restrictor and 19mm for alcohol. Well you wouldn't necessarily have to develop all these parts. Why not just use pre-made ones off of a FI bike? Perhaps an F4i or 600RR or I guess really any fuel injected 600cc engine you could probably use. </TD></TR></TABLE>

Yeah everyone has to run a restrictor, but starting from an FI bike doesn't make it any easier. The intake manifold won't work, since they're made for individual throttle bodies on a bike, and also have no provisions for a restrictor. The stock fuel injection won't work well at all, since its not mapped for a restrictor, which radically changes the characteristics of the motor. Running a piggy back has been done, but its not very sucessful, and its easier to just go to standalone. Most throttle bodies are too large for a restricted 600 cc motor. Fuel system you need to totally start from scratch, since on an F3 it needs to be adapted to work with FI, needs to be braided line, and a new fuel tank needs to be made (for packaging, size, and cornering loads). Stock header and exhaust system won't work as well, since the packaging is different. Wiring harness on the bike can literally be thrown away, since it doesnt have any of the sensors needed for the FI.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr Hammond &raquo;</TD></TR><TR><TD CLASS="quote">
You'd probably have to fab a plenum for the carbs anyways. Exhaust manifold is fabed anyways. Find a t/b to work, find injectors to work, change fuel system to meet high pressure (no biggie). Fine tuning would take some work, but converting a carburetor engine to use fuel injection, especially one that has readily available parts because it has already been done, wouldn't seem terribly difficult. I'm not trying to say I could do a better job. I understand the time consumption it would take to do this. I was more wondering what problems they incurred while doing this.

I was just wondering. When I saw CBR F3 engine, I knew they were carbed. The types of forces these cars would exert would probably give you fuel starvation problems with that type of carb set up. Which is why I asked if he switched to FI. Then I looked at the picture and noticed they did.

He mentioned it wasn't an easy task, but then said they did it, so I was wondering what complications they ran into doing so, besides the obvious fabrication points listed above. Obviously you need the parts and you need to install them, and this will be timing consuming, but were there any snags in doing so along the way?</TD></TR></TABLE>

Like you said, running carbs would take just as much work, if not more than running fuel injection. Might as well just run fuel injection.

As far as snags... just the usual problems you run into of trying to get the motor running, and working out bugs in the fuel and electrical systems.


Modified by BUJonathan at 6:12 AM 5/9/2005


Modified by BUJonathan at 6:13 AM 5/9/2005