My time, need help understanding.

[Wink]

Okay, I am a P plate el xr6 driver.

Best time I have done is a 14.301 at the moment. Though in a few months time, me reaching 14 flat should be accomplished.

Though here is my question.

I average a 14.4 at 95-96mph at the 1/4

Though 2 runs I did, I did a 14.4 at 89-90mph at the 1/4

I don't understand. I get a slower mph though still maintain the same time?

I'm aware reaction time does not effect 1/4 time, though seems a few people I ask what the go is happening, they seem to say it was because of my reaction time.. I just nod an move on.

I am getting 2 seconds flat 60' on street tires so I don't think it's my launch..

Any help please?

[Ivan]

Could be down to gear changes.

Ian

[Psi-Pop]

Can you post up the slip? Should be able to see where your going faster.

[capriv8]

Wheel speed at the launch can affect mph, ie wheel spin can result in higher mph with same or slower et. In your case the opposite may have happened.
You may have hooked up really well then loaded the engine slightly.
I just wish to add good luck with achieving your goals with ETs. Its a fantastic side to drag racing to continually develop a car and see the results on the track.

[JG33RD]

Have you thought of converter slip also, is the rpm over the line the same?

[Wink]

Sorry, I should of stated it's a T5 manual.

I will type down the slips as I don't use photobucket.

60' - 2.055
330 - 5.913
1/8 - 9.171
MPH - 75.63
K/mh - 121.72
1000 - 11.953

1/4 - 14.301
MPH - 96.23
K/mh - 154.87

60' - 2.137
330 - 5.974
1/8 - 9.229
MPH - 75.63
K/mh - 121.71
1000 - 12.013

1/4 - 14.412
MPH - 90.31
K/mh - 145.34

[Wink]

I also run 24 - 26psi in Federal 595's though they were very bald.
245 / 50 R16

I launch at 3,000rpm an it's straight clutch dump.

I did have axle tramp issues, though lowering the tyre pressures seemed to of fixed it for now. Rare occasions I do wheel spin off the line.

I also change each gear just under 5,500rpm. Thinking maybe I should try changing at 5,000 instead or?

[Road Games]

Here's my example mate...

14.0 was changing at 6000rpm (4spd auto)

14.2 was changing at 5500rpm..



Rev it harder depending on the combo i would suggest for more mph, clutch finess will bring your ET down...

HTH.

[JG33RD]

Was the slower mph on the latter runs? Your 60 is nearly a tenth slower which shows on the 14.4 but the mph to the 1/8 is the same, maybe you fried the clutch a bit and is slipping in the top end although I would have thought more so on launch.

[Wink]

Thanks for all your input.

I get 2.1xx 60's when I axle tramp or wheel spin.

I don't feel any clutch slip in the top end.. That I can notice anyway. I replaced the clutch a few months ago, went to a Valeo clutch kit an reckon it's better then my old exedy clutch kit..

XR6menace, are you running semi slicks or street tyres?

I just couldn't understand the slower mph but still maintained the same times. I will have to up my rev limiter to 6,000 an see what happens I suppose..

[Psi-Pop]

Will there be much in moving the limiter? Is the motor still making power there?

A set of drag radials will help the launch consistency but might end up hurting the clutch.

The addiction has started. lol

[Road Games]

On those two passes mate 275/40x17"s ET's

[Giant]

if your MPH is down it also means your power is down. It maybe to do with heat and ECU retarding timing. You could try a cooler thermostat and a longer gap between runs.

[Wink]

If my power was down, how come it still ran the same time consistancy?

I have set my timing to 30 degree's advanced after tricking the computer by earthing out the pins. I have a powerbond pulley an that is how I know the degree's, still no pinging yet.

I know my lifters are a bit buggered, I think they are seizing. As after some drag times, my lifter/s are really bad an ticking very loudly. It also causes my car to shudder, sounds and feels very similiar to a miss in the engine. I also ran a compression test.

1 - 175
2 - 175
3 - 175
4 - 175
5 - 155
6 - 150

So hopefully my lifters at the rear of the head has caused the lower compression readings.

I have new lifters an a jp high volume oil pump ready to put in it, I just have big issues sealing the sump on the damn thing.

Thanks again for your input fellas.

[Giant]

MPH & Racing weight can give you a fairly accurate HP figure. 0.1 diff is not the same time its a reasonable gap over the 1/4

[Work Horse]

Not sure which track you race at.

If you lift your foot at the end of the track, before crossing the terminal speed trap it will lower your speed without affecting your ET.

On some tracks the terminal speed trap has a sensor before and after the finish line. The average of the two readings is your speed across the line. If on one run you accelerate through the last trap and on the next run back off before you cross it your speed will change but your ET will not.

This could be an explanation.

[dieseltrain79]

Probably a bit of clutch slip . Although i would expect to see more of en ET drop from 5mph .

However if your just backing off right at the end , this effects mph, but not much ET As Work Horse mentions .

[Wink]

Ah yes, makes a lot of sense to what you said Work Horse. I am racing at Willowbank drag strip, in Brisbane qld.

I guess I will just keep at it, an I will find out about the speed traps. As that is probably what it is now, as I am pretty certain I am not having clutch slip that I am aware of. Otherwise I would imagine it slipping from my hard launches.

Thanks everyone!

[Road Games]

Willowbank runs down hill definately run it out the backdoor mate...

We are lucky to have such an awesome track up here...

[Giant]

Did the time trap tip solve the problem?