Tweaks Re-build thread

[gorgonheimer]

hey charlie, hows school going?

[Advancedynamix]

Babe was a dark blue 89, and I sold her too. About 6 months ago another enthusiast, also from San Diego, became Babes proud owner. Not to worry though, I have 2 more Festivas. One (88L) is getting a B6D swap in the next couple months. The other (89 L) will be getting the full fledged track car treatment. I had to thin the herd. It was hard to sell Tweak and Babe, but I have new visions and couldn't justify changing either of those cars since they were perfect as they sat. I'll post new build threads for Pedro (88 L) and Virginia (89 L). They are twins, both white with red hockey stripes. I'm doing a good twin and evil twin theme. If the good twin has twice the factory HP, what will the evil twin have? hahahaha (evil laugh).

[Team Lightning]

I remember a black one, and seems like another one. Maybe......

[TominMO]

Wow, I for one am shocked to see her go to someone else. Jerry, I bet he does have other plans for a Festy--I believe he has two more.

[Team Lightning]

Charlie, is anything to replace Tweak in the pipeline?

[Advancedynamix]

Thanks guys! I never really left, but things sure have slowed down around here.

Well, in my typical better late than never style, I'll update this thread a bit.
I sold Tweak to a good friend of mine in San Diego almost a year ago. Tweak was pretty much built exactly as I had planned. After my victorious race weekend, I decided it was best to sell the car while it was still fresh, rather than abuse it another season and prove nothing. The current owner had it inspected by the California Air Research Board (CARB) team of engineers and it was officially given the CARB stamp of approval. Tweak may be the only legally documented CARB approved B6t Festiva. The door sticker now reads DOHC 16v Turbocharged 1.6L! This may be one of my most proud accomplishments, as the CARB engineers are not easy to impress. The entire inspection facility was abuzz while Tweak was under the microscope and it not only passed the first time, it left an impression with the engineers about Festivas. Since then, Tweak has lived the easy life in sunny southern California. I get frequent pictures from the new owner and I have the option to drive her whenever I am in the S.D. area.

[shadetree]

^ Yea x 2...

[nitrofarm]

Good to see you back Charlie Happy Holidays !

[Damkid]

To add my little bit of experience towards LSD in a festiva, my festiva sucks under WOT around a corner and was easier to handle with the open diff, however my straight line traction was improved with the LSD

[Advancedynamix]

so youre telling us that the limited slip differential is only needed in cars that have absurd chassis flex. in your theory, no lsd is needed if you can get both your tires to stay on the ground an equal amount?

LSD is a good way to cover up improperly set up chassis. I prefer to set up a car with an open diff, until it's perfect, then add an LSD if I feel it's beneficial. Sometimes it isn't. With 180hp, the Festiva doesn't gain anything from an LSD on a road coarse if it's set up well. I believe an LSD would have actually hurt my lap times in this car. I often intentionally spin the inside tire to get the car into the power before settling the chassis ( similar to slipping the clutch on a motocross bike). Additionally, like Nitrofarm said, certain limited slip differentials become a hindrance in corners.

Also, a side note. Not all chassis flex is bad. In fact, most chassis flex helps a car to maintain traction. Bad chassis flex is the kind that points the wheels in the wrong direction or destroys the car. The Festiva has just the right amount of good flex.

[Advancedynamix]

Hey Charlie, I am joining this conversation late, sorry. To re-affirm, that is a beautifully clean engine and engine bay, and very interesting ideas on where the chassis twist comes from and how to strengthen it. I have debated that with friends who ice race these chassis many times, as to how best to improve the front suspension.
But I have a question, in the video you re-posted. There is a segment with the Miata following you where you go into a fast, wide sweeper, I think it might be the end of the front straight, but I could not tell for sure. The video shows at least 2, if not 3, sequences of the rear end starting to come out, you catching it, maybe getting a touch of understeer, then the rear comes out again to start the cycle a second, and maybe even a third time.
The same cycle happens to me ice racing in the fast sweepers, enter, apex, then understeer-oversteer-correct, oversteer-correct two or three times. It is not so pronounced in other chassis I have raced so I put it down to the short wheel base. But are there things you have done to the spring rates and shocks specifically to reduce this effect. At least, things you are willing to talk about?
With the ice racer, the suspension still needs to be soft, though stiffer than stock, as the rear stock spring rate is scary low when racing, it just bounces and oscillates way too much. (I put Festi fronts in the rear to stiffen it a bit) Anyhow, my point is, the actual rates are not going to be the same as yours, but the front to back ratio, or the corner weight ratios might be similar, to reduce the effect.
Of course, better driving is always indicated, but any chassis tips in this regard are very welcome.

Sorry, I missed this question. The multiple mid corner pivots are caused by throttle input and lift. To tune this, you shouldn't use spring rate, but instead the shock valving. That wide high speed carousel is tricky because I've got the valving set up to work well in the tighter sections of the track so I've got to dance it a little on the high speed stuff. It blows my mind how easy this car is to control on the edge. I bet they are a lot of fun on the ice tracks.

[nitrofarm]

so youre telling us that the limited slip differential is only needed in cars that have absurd chassis flex. in your theory, no lsd is needed if you can get both your tires to stay on the ground an equal amount?

I think what he saying is he is hoping that he will be able to get enough traction with the contact patch he is running. LSD's really don't work well in high speed corners,you get bad over steer.But Charlie will fill us in in I'm sure.

[bhearts]

My next roadrace setup will have a tubular front end with trailing links and no front sway bar. I'd like to put 250 ft.lbs to the ground with an open diff.

so youre telling us that the limited slip differential is only needed in cars that have absurd chassis flex. in your theory, no lsd is needed if you can get both your tires to stay on the ground an equal amount?

[Icedawg]

Hey Charlie, I am joining this conversation late, sorry. To re-affirm, that is a beautifully clean engine and engine bay, and very interesting ideas on where the chassis twist comes from and how to strengthen it. I have debated that with friends who ice race these chassis many times, as to how best to improve the front suspension.
But I have a question, in the video you re-posted. There is a segment with the Miata following you where you go into a fast, wide sweeper, I think it might be the end of the front straight, but I could not tell for sure. The video shows at least 2, if not 3, sequences of the rear end starting to come out, you catching it, maybe getting a touch of understeer, then the rear comes out again to start the cycle a second, and maybe even a third time.
The same cycle happens to me ice racing in the fast sweepers, enter, apex, then understeer-oversteer-correct, oversteer-correct two or three times. It is not so pronounced in other chassis I have raced so I put it down to the short wheel base. But are there things you have done to the spring rates and shocks specifically to reduce this effect. At least, things you are willing to talk about?
With the ice racer, the suspension still needs to be soft, though stiffer than stock, as the rear stock spring rate is scary low when racing, it just bounces and oscillates way too much. (I put Festi fronts in the rear to stiffen it a bit) Anyhow, my point is, the actual rates are not going to be the same as yours, but the front to back ratio, or the corner weight ratios might be similar, to reduce the effect.
Of course, better driving is always indicated, but any chassis tips in this regard are very welcome.

[nitrofarm]

Gomez has nice pics of his and specs too.

X2 Gomez spelled it out in Black and White very nicely,no secrets.