vectraTBO

Hello guys, my first post here so please be gentle

I'm from Finland and I drive with FWD -89 Opel Vectra sedan. I have been struggle many years with traction on 1/4mile. I have been searching 10s pass but it seems to be very difficult for me. Maybe you guys can give me some advice because you have some crazy FWD cars here!

My best 60ft time is 1,818s with M/T ET Drag 22x8-15. At that time the slicks were 6 years old! With this tire the car went 11,037s/207,83kmh on 1/4mile(2013). In the end of the track engine went to the rev limiter. The engine made 544hp/587nm on dyno by the crank. Since that I've been hunting 10s pass.

So I changed bigger tires. M/T ET Drag 24,5x8-15(5 year old tires). Whit these the best 60ft was 1,9-2,2s. Best 1/4mile 11,232s/224,17kmh.

After that I made changes to the engine. It made 615hp/672nm on the dyno(crank). But still no results on the 1/4mile. I even went back to the smaller 22" tires but there where no traction at all.

Then I bought new tires, same M/T ET Drag 24,5x8-15. With these the best 60ft was 1,897s. In the same pass car went 11,006s/226,83kmh. This was first pass with the new tires. Since that the times starts to go worse.

After that I tuned the engine more. It made 641hp/735nm on the dyno(crank). With that power the car went 11,242s/226,71kmh at the 1/4mile. 60ft +1,9s. Few passes went also to the rev limiter with trap speed 229kmh. I use full power only in 4th gear, otherwise the tires are slipping too much. I have different/smaller boost in other gears(DIY boost by gear).

It feels like the tires are spinning all the time and I have no traction at all. So what should I do? I've been thinking bigger tires(26x10-15)? I Also have been thinking new springs because I dont have glue to the spring rates now? They are just some lowering springs.

Car specs: All steel chassis with Lexan side windows, 1180kg with driver, 641hp/735nm at the crank, some lowering springs with yellow Koni Sport, 24,5x8-15 M/T ET Drag with best ET 11,006s/226,83kmh.

Best ET:

joe b

From the video it seems you are running too much air in your slicks . Try and lower them down to around 6.5-7 psi . Also do a 3rd gear burnout for a couple of seconds . Preload it and you should be able to get into the 1.7x range if not better . That should be enough for a 10 second pass ..

vectraTBO

Ok. I have about 20 psi pressure on tires and I know it's too much. I have tried to drop it but then the front starts to shake badly. Do you think that the 24,5x8-15 tires are good for this power level or should I go bigger? What kind of spring rates you guys use?

joe b

I have no idea why it would shake badly . I personally run 24.5X9X13 . I run them on a 2680lb Integra . I can usually keep my 60ft times in the 1.6x range . I top out at 149mph at the end of the quarter mile with minimal vibration but no shaking .

vectraTBO

With lower tire pressure the front shakes only in start. 1.6x 60ft would be a dream come true for me My car weight is 2600lb with driver. 26x10-15 tires would mean big modifications for me and I dont want to fit them if I dont have to.

bauergold

Nice car!

You definitely need to air down the tires more. I like running my 24.5 inch slicks around 7psi.
Is the car wheel hopping when you air them down?

JDMarv

lower tire pressure should work!! when i first went out i started at 9psi and worked my way down .5psi at a time.. so far the car likes 7psi the most lol.

vectraTBO

Thanks! Yes the wheel hopping would be the right word. I have tightened the front shocks and it helps a little for that. Or should I give the engine more boost/power in the start?

joe b

More power if your wheel hopping .

vectraTBO

Ok. Lower tirepressure and more power to start. Also stiffer rear springs?

weedburner

Your clutch is hitting the tires way too hard. It takes a balance of clutch slipping and tire spin to produce a maximum amount of thrust with a minimum amount of engine bog. The clutch and how it slips during launch is what controls that balance.
...Not enough clutch slipping, either the engine bogs or the tires spin too much and lose their thrust potential.
...Too much clutch slipping, the tires stay stuck but the clutch gets smoked.
I don't know how what clutch you have or how much slipping it can take, but adding some clutch slip during launch would certainly improve your 60'.

vectraTBO

Ok. So I guess the tires aren't the problem at now. I Have Sachs SRE clutch cover and five paddle sintered plate. I Haven't try to slip it much yet. Maybe I have to try.

weedburner

bauergold

I would also do the burnout in 3rd gear. You'll get a lot more wheel speed and heat up the tires better.

vectraTBO

Ok. Clutchtamer would be the only option for me because I have clutch with cable. I have to think about it.

In the first video the burnout gear is 2nd. In the second video it is 1st. There is not a big difference between 1st and 2nd. Maybe I have to try 3rd gear.

In Finland we dont have many FWD drag racers so the knowledge is hard to find. Everybody want's to drive with RWD.

bauergold

Definitely try a 3rd gear burnout and really low tire pressure. 7-8psi is usually what my car likes.
My car on stock suspension doing the above will get 1.6 60fts.

Let me know how it works and we can go from there.
RWD is way better but we can make FWD cars work pretty well.

vectraTBO

Ok. Here in Finland is winter now. The first racing days are after couple of months. I will report the results immediately when I have them

Thanks for the advice again for everybody!

bauergold

Good luck with the car! Looking forward to the results.

vectraTBO

Hi again!

There where some events on last weekend. 10s pass was really close. 1,825s 60ft was the best but in that pass I have some problem with 4th gear and I have to pump the pedal three times. That is why the trap speed drops to 216kmh. Without the problem that pass would be 10s.

Weekend best was 11,033s/227,76kmh:


And below is these two passes:



Tirepressure was 8-9psi. I didnt manage to do third gear burnout because there where too much grip on the track. And I dont have antilag system because hydraulic lifters.

On next weekend there is new events

vectraTBO

Finally got the 10s pass




60ft was not good in that pass, still 10s time. My first gear is pretty short and the shift time is a little before the 60ft. I thinks that explaines why I cant go better 60ft times.