1/4 mile gearing (and grip)

by **galapogos01** » March 10th, 2011, 9:20 am

Bit of a question for those with a bit more 1/4 mile experience.

Last time I had the EF out I had two major probs - one being traction off the line (street tyres, full pressure, shit LSD), the other being the car shifting into 4th before crossing the line.

The car has 18" wheels (25.4" tyres). It has a BTR and 3.9 diff gears.

It seemed to get to about 4500rpm (from memory, might have been higher) in 3rd before upshifting. In 4th it didn't seem to gather much more speed. It's still making plenty of power at 4500 in 3rd and the AFRs are good etc. It seemed to shift into 4th a bit too early IMO. I don't know how strong 4th gear is in a BTR but I don't imagine they are built to push 200 odd rwkw.

Is anyone else with a BTR getting into 4th down the 1/4 mile? I'm guessing not many people have 3.9s with boost as most need load for the turbo so run taller gears.

Im looking at 26" tyres to help with this but that will only be marginal. I may also be able to edit the upshift tables in the ECU to hang onto 3rd longer. I haven't checked this yet.

Thoughts?

by **ClassicAU** » March 10th, 2011, 9:23 am : **galapogos01 Likes this post**

Why can't you just stick the shifter into 3 and leave it Jase? That's what I did in my old AU 220 to get the quickest time.

by **galapogos01** » March 10th, 2011, 9:29 am

Hadn't thought of that :oops:

Wonder if it'd redline 3rd... anyone know if 3rd is 1:1 in a BTR?

I'm hoping for a 13.5 next time I go out. Less weight, more grip. Considering going to the AFF day.

EDIT: it is. Based on http://www.prosystemsracing.com/calculate.html I should be doing 118mph at 6000rpm with 26" tyres. No chance of that trap speed so sounds like i'll be fine in 3rd!!

by **EFFalcon** » March 10th, 2011, 9:37 am

3rd should be 1:1

by **ClassicAU** » March 10th, 2011, 9:41 am

Haha, nice one!

Yeah, it worked for me fine in the auto 220, I think I pulled like 98mph for a 14.6 best time leaving it in 3rd. Can't remember getting near red line, but it was also stock 3.45s as well. I actually found that was better than manually shiting up the gears too.

by **galapogos01** » March 10th, 2011, 10:15 am

Thanks gents.

Manually upshifting for me often results in limiter bouncing. I think sticking it in 3 will be the go.

Looking forward to going back to the strip

Any other techniques for getting it out of the hole quicker? My 60fts varied hugely from run to run. I'm hoping the slicks help with that.

by **Dansedgli** » March 10th, 2011, 10:30 am

Are you going proper slicks or et radials?

Let me know when your going next and I'll come too.

by **galapogos01** » March 10th, 2011, 10:38 am

Looking at the ones gil got off Sinan. ET drag slicks he says. tbh, I have NFI what the difference is.

Will either go to the AFF day or maybe a test & tune before then... thinking the AFF day would be good to see some decent cars.

by **Dansedgli** » March 10th, 2011, 10:42 am

They are proper slicks.

Should drop your times by a fair bit if you can launch on more boost.

by **galapogos01** » March 10th, 2011, 10:51 am

I hope it can do a decent skid with them... and that I don't break shit!

by **EFFalcon** » March 10th, 2011, 10:52 am

i'd be worried about the diff, didnt it start singling at heathcote last time?

by **AaronEF8** » March 10th, 2011, 10:58 am

with technique, that'll change with slicks fitted. Maybe try flashing the stall on the second yellow so the suspension isn't fully loaded when you take off. And do a bigger burnout.

by **galapogos01** » March 10th, 2011, 11:02 am

Yeah it did. It was partly my fault as I was starting burnouts with one wheel in the pit and one out. Since then it's been OK, singles occasionally tho. Dunno if I should try changing the oil.

I don't really want to spend a grand rebuilding it then take it to heathcote and thrash it... prefer to see how I go. If it singles more it's not the end of the world, just wont get the best time possible.

by **Parfrey** » March 10th, 2011, 11:24 am

won't slicks be a bit of overkill? might actually cost you time?
+1 for keeping it in 3rd, quicker than using 4th and 4th in a btr isn't very tough, i would recommend no WOT in 4th ;-)

by **galapogos01** » March 10th, 2011, 12:54 pm

Why do you think it'd cost me time? What would you recommend instead?

I had big trouble getting it to hook up. I couldn't launch with any boost or stall, and had to feather the pedal a lot to get a clean start. Granted I was running street tyres (Kumho KU31s) at street pressure (40psi) but if I had that much trouble launching I want to make sure it's gonna grip before I go back. It's got a 3k stall and 3.9s.

I'm posting here for advice so im all ears

There was something like 0.4s between my best 60ft and the one that got me a 13.8!

by **iCER** » March 10th, 2011, 12:59 pm

WOT + 4th gear == SMASHING the gbox. Its how all BA BTR owners keep smashing them. I redline 3rd gear to about 6600rpm now which should get me over the line.

As everyone says, stay in 3rd. you need to be going around 200km/h to go to 4th. Thats a 10/11sec pass.

by **NUT347** » March 10th, 2011, 1:40 pm

How big are the slicks Jason?

If they are slightly taller then your wheels you should get a bit more out of 3rd. But defently done use 4th... rev 3rd for as long as possible!

The slicks should help your situation considering the size of your converter. Do what Aaron said aswell, flash it late so the suspension doesnt tighten up so much.

Also, dont let to much air out of the slicks on your first run, flatter tyres give more traction but cost time because you have to drag them

Thy them on 22oddpsi first, then do a medium skid and see how you go, if it bakes up again drop the pressure a bit and do a medium skid again.

Try not to bake up to much on the skid, i remember reading somewhere you suffer from heat soak.

by **Parfrey** » March 10th, 2011, 1:49 pm

lol icer, i busted 2 and it wasn't from wot in 4th.. and show me how he can do 200kmh in 3rd with 3.9 diff gears? but i get your point.

Well i guess it probably wont cost much time, but i dont see the point running big ass full slicks on a car that should be ok with normal sized semi slicks. just means more weight/drag/rolling resistance. I spose it will cure the traction problems so thats what your really after

I remember what waveman's el was like with a 3k stall and 3.23? gears lol

loved a skid. Don't be afraid of playing with the pressures either, can make a big difference.

by **AaronEF8** » March 10th, 2011, 2:14 pm

slicks can cost time if you run massive ones on a slow car due to the extra friction.
Remember you'll need matching front tyres to run slicks. I'd say dropping the pressure on your tyres to about 28psi will make a fair difference.

A rule of thumb is 1 tenth off the 60' = 2 tenths off the ET.

by **galapogos01** » March 10th, 2011, 2:39 pm

The slicks I was looking at are 26". Current tyre OD is 25.4". Either way I shouldn't hit 6 grand in 3rd as im miles from an 118mph pass!!!

Thanks for the tips on the launch... but now im wondering whether I need the slicks? It really struggled to hook up when I went. I couldn't get out of the hole cleanly at all with the 9psi pulley. Why would I need front tyres to match? Only if theyre radials right? These arent radials... and if I run a good pressure they shouldn't sap much power, right?

Maybe I should just get some grippy 15" stockies at 20-odd psi... I just want to get a good clean time with the current setup. It's got more in it than a 13.8.

by **Dansedgli** » March 10th, 2011, 2:55 pm

Rear tyres need to match the front. Those ones are cross ply tyres so you'll need front runners.

If heathcote is fussy anyway

by **AaronEF8** » March 10th, 2011, 2:57 pm

running a bag slick (as opposed to a radial) will make it worse, the rear will wonder a fair bit and push the front side to side, pointing the front wherever the back wants. Think running stockies on the back and 18's on the front, but 10 times worse. There's some funny vids of it on youtube.
I don't think heathcote care, but everywhere else won't let a car run with a mix of radials and ply-type tyres.

Some decent 15" tyres should do the trick, but in saying that, I believe heathcote isn't consistant with grip levels, and racing in June will be fastest just as the sun goes down. Warm (compared to 10am) track and no frost.

by **galapogos01** » March 10th, 2011, 3:13 pm

Really? Lucky I asked. I CBF getting matching front tyres.

Haven't run stockies on the back before. I guess i'll be looking for drag radials or decent stockies.

by **holmsy** » March 10th, 2011, 3:16 pm

i had some semi's last year at heathcote that wer pretty much at the end of their life.
and i had no issues with traction at all.
i had 1 run where i did a very small burnout and it did kick a little bit on change into 2nd but other then that they just stuck every time.

by **Dansedgli** » March 10th, 2011, 3:17 pm

Get some et street radials in as wide will fit.

They held on well in that other au I had launching on 8 or 9 psi. I ran 275/17's.

by **holmsy** » March 10th, 2011, 4:07 pm

255/60/15 fit well in my ef. and wer fair tall.

by **Mr_4.0** » March 10th, 2011, 5:48 pm

My ef was shifting into 4th before the line so I just held it in 3rd. Crossed the line just over 5200rpm I think.

by **iCER** » March 10th, 2011, 9:23 pm

yep, use et streets. that is enough. Running full drag slicks, you NEED front runners, else risk death!!!

by **Mr. CVE** » March 10th, 2011, 9:34 pm

radials on the back and front, or rag tyres all round.
Have you considered converter slip ?

we have run 10.9 on a 235 radial

by **galapogos01** » March 11th, 2011, 5:58 am

Yeah, ill be passing up the slicks as I didn't realise I'd need front runners.

Just need to find a pair of 2nd hand et streets or similar. I'm only going to use em for a few runs.

When you say 10.9 on radial, do you mean street or drag radials? And what do you mean about converter slip?

by **Dansedgli** » March 11th, 2011, 7:00 am

Are gill's ones drag radials or cross ply?

If they are drag radials they might be alright. You wouldn't need front runners from what I understand.

Cve would be talking about the et street radial.

by **holmsy** » March 11th, 2011, 7:23 pm

while we are talking about tyres.
has anyone used the Good Year Drag Radial Eagle SS http://www.vpw.com.au/productgroup.asp? ... GrpID=4547
or even better compared them to the mt street radials. ??

they are of similar style and price. (maby a little dearer)

by **Duffman** » March 11th, 2011, 9:58 pm

galapogos01 wrote:Yeah, ill be passing up the slicks as I didn't realise I'd need front runners.

Just need to find a pair of 2nd hand et streets or similar. I'm only going to use em for a few runs.

When you say 10.9 on radial, do you mean street or drag radials? And what do you mean about converter slip?

he means have you alowed for convertor slip when you calculate your rpm though the traps

by **JUSTXR8** » March 12th, 2011, 8:27 pm

If it was my car run a wide street tyre and let it down heaps 10 15 psi, one of my cars has cut a 1.9 60foot from a street tyre, but you could not stall it and jump on it other wise it would fry the tyres for 3 gears :doh:

With slick, if you whare to run a ET radial you dont need front runners even if it cuts flat 10s or faster, but in saying that you dont need front runners either till your faster then 12.5 on a andra track, and heathcote is not. They will let you run what ever you like ive run 11s there at almost 120mph with no front runners with full slick and they never even looked at me, calder on the other hand

by **Michael (HYPOEB)** » March 12th, 2011, 9:46 pm

Just out of curiosity why are front runners so important?
Also Calder are not as strict as alot of people make out. They say you need a tail shaft loop at anything under 14 seconds and i was running 13's all day without one and they didnt say anything,My front seat was loose aswell and they said just tighten it up and my bolts holding my battery down in my boot were loose and he told me just to tighten them up aswell.

There realy not tha bad..

by **Mr. CVE** » March 13th, 2011, 12:27 am

We are trying to fix Calder to ensure it is safer for everyone.
and make them log people so when they come back they have fixed their previous issues.

My coupe ran 13's with slicks and radial fronts.
I took my commodore out once the same way and it was so all over the track, they thought I had a broken axle !

slicks and radial = bad

by **justa6** » March 13th, 2011, 8:49 pm

i've got 235 60 15 mt et street's and they are unreal, you won't need anymore then that.

by **Mr_4.0** » March 14th, 2011, 12:15 am

What do 235 15 inch mt cost ya??

by **justa6** » March 14th, 2011, 6:24 am

$ 264. each on vpw. and should of wrote et street readial, so no need for front runner's. i had 19's front 15's rear, ran straight all day. put them down to 18psi and i almost bet with 200kw you can't spin them.

by **Mr. CVE** » March 14th, 2011, 8:30 am

we went 10.9 in a xy ute with 235 radials.

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