[Flavio]

After a lot of tries I cannot get a better time than 13.43s for the 1/4 mile, most of the time I run about 13.8s or even worse. My best trap speed is around 115mph, which I think is okay. I have a BPU Supra.
Above times were measured with two (heavy) persons, almost a full tank of gas and some stuff in the car. I estimate the weight of the car to be around 4200lbs.

My question is how do my 19" wheels & tires influence the ET time negatively. I think they are a lot heavier than the stock 17" wheels. If I switch to 17" rear drag radials, how much would my time improve and would it make launching the car also easier? If it would be worthwile I will go for it, if only for bragging rights, saying I can do the 1/4 mile in 12.5s or so.
What if I run alone with an alomost empty tank of gas, the car weight would be around 3900lbs, how much would that save me in ET?

Bear in mind that these times are not actually measured at a drag strip but with a G-Tech Pro and a Blitz Multi Speed Turbo Timer (calibrated to +/- 1 km/h with a handheld GPS).

When I use the standard formulas for calculating RWHP I get more than 500RWHP (based on trap speed) and 343RWHP (based on ET). How realistic are these formulas? If I average them I get 424RWHP, which sounds right for a BPU Supra with a lightened flywheel or are these formulas unrealistic anyway?

Flavio

[ July 09, 2001: Message edited by: Flavio ]

 

[Chucky Doll]

Your 19's are slowing the car down period. How the hell does your car weigh 3900lbs? Do you weigh 400+? Your cars weight is also a factor.

 

[Flavio]

I know the 19"s are slowing the car down, but I would like to know how much?

My car registration papers say my car weighs 1606kg + 120kg (I am a big guy) + 50kg (gasoline) + 10kg (stuff) is 1786kg = 3937lbs. This is with standard wheels!

Those 12.5s or better times, how much do these cars weigh?

Flavio

[ July 09, 2001: Message edited by: Flavio ]

 

[Chucky Doll]

I dont know the conversion b/c we dumb americans are on a different metric system. But the Supras weigh 3400-3500lbs from the factory. With 17's and Drag Radial your times should drop a good .3-.5 seconds at least. Is your car a stick or auto?

 

[Flavio]

Originally posted by Chucky Doll:
<STRONG>I dont know the conversion b/c we dumb americans are on a different metric system. But the Supras weigh 3400-3500lbs from the factory. With 17's and Drag Radial your times should drop a good .3-.5 seconds at least. Is your car a stick or auto?</STRONG>

6-speed

Flavio

 

[Chucky Doll]

Yeah use Drag Radials and dump the clutch at a high rpm. Remember you have to pay to play. Also did you buy the 2-Step Rev limiter yet? I saw one this past Saturday launch, the damn thing looked like a Jet.

 

[Chucky Doll]

The guy is running 19" tires which is barely any rubber to begin with so deflating the tires will kill those things quick. Flavio buy drag radial and put them on your factory 17" wheels. From what I understand GTech time is correct within .1 but the mph is off a good amount. Go to the track and loose the passenger.

 

[Flavio]

Thanks guys, I guess I'll have to get some drag radials. Any other brands besides BF Goodrich and Nitto (not available outside USA unfortunately) you can recommend? 275/40R17 is the preferred size I guess?

Flavio

 

[Chucky Doll]

Sorry I've personally only used the Nittos but switched to the BFG comp T/A DR's. I think hoosier makes DR's can you get those?

 

[Steve Jarvis]

I ran a 12.601 @ 115.45mph in my Supra on street tires with a 2.17 60' (not great). He is not any where near getting out of his setup what is available. It is very easy to throw parts at something to go fast, but if you haven't developed the skills of found out the incorrect information you are getting (which I feel is the case in this instance) than the parts aren't going to help. Trust me, take it to the track before you go buying more parts.

Reducing the air at the dragstrip will help lengthen his contact patch (which is what you need for straight line traction). He doesn't have the air pressure he would need to protect the car from potholes, but he shouldn't be hitting potholes on the dragstrip anyways.

Later, Steve

 

[Chucky Doll]

I'm not going to argue back and forth with you Steve. Fact DR's will lower his time. Fact launching a Supra with 19" wheels is hell. Fact I stated before that the G-Tech was not 100% accurate therefore he should go to the track. His 12 second times are there but it's traction thats killing him.

 

[Steve Jarvis]

I was not contradicting your statements or arguing with you. I agree with what yours saying. I was only trying to get him to find out what incorrect information he's getting before moving to the next level. I would agree that traction seems to be the biggest part of his problem, except he is running even slower ET's than a really poor launch would net with that mph. Again a bad 60' of 2.4 seconds should have still netted him a 12.9 second et with a 115 mph trap. A 2.4 second 60' should be atainable even with a 19" wheel package. If you assume the G-Tech is off 3 tenths that should still give him a G-Tech time of 13.2. This is quite a bit off of the 13.43-13.8 seconds he is seeing. Basically I don't think he needs to upgrade his tires to run 12's if that is his goal. He only needs to go to the track (which you agree with). If he still wants to buy some 17" wheels with drag radials, than yes he will run even quicker.

Later, Steve

 

[Chucky Doll]

Steve I agree. Flavio you should run your car at the track b/c the mph you are reporting should infact be in the 12's so work on your 60' times and go from there. Good luck.

 

[TimZ28]

115 MPH is good for low 12s with average driving. Power-wise I'd put the car around 370-380 RWHP. Definitely not 425... that would be good for 120-121 trap speeds.

Get some Nitto DRs and utilize the power you are making. High 12s at 115 would be nothing top brag about even if you did do it.

Tim

 

[Steve Jarvis]

You don't need dragradials to improve your times. If your running 115 mph you should be able to break into the 12's on street tires. Your car probably weighs in the 3,500 to 3,600 lbs. range with a full tank of gas. Add two passanger @ 400-500 lbs. for a total weight of about 4,000 lbs. Your heavier 19" wheels are not going to make that much of a difference. Your running a decent mph so your power to weight ratio is alright, you just need more traction and quicker shifts. I would try letting the air down to about 25psi, shifting at redline in all gears (even though 6,500 is better for 2nd and 3rd), make sure you leave the car in 4th until the end of the 1/4 mile, and shift as fast as possible. You should also go to the track. I know the G-Tech is about 3 tenths of a second slower than an actual 1/4 mile. You will also be able to see your 60' times so you can understand when you are improving. Basically you have enough mph to run a 12 second run with a 2.3+ 60' time even with 2 people in the car and a full tank of gas. To run the times you were running you would have to have gotten a 3.0 second 60' time. This is not very likely. My guess is that your mph is wrong or the et is wrong. Basically get to a track so you can see what the reality is.

Later, Steve

 

[SurMkiv]

Supras has too much power when turbos are online..stupid gtechs can't handle it..I ran the same times on gtechs 13.5 13.7..but beat cars running 12.5..explain that?
I think the gtech accuracy has alot to do with traction and suspension. It will probrably give you more accurate times with a stiff suspension. just my experience..I took my gtech, turned it sideways , placed it in front of the rear tire,..rev my Sup..and burnt it to crisp.

 

[KERR]

my dynoed 402 at the wheels and 410tq. i always run mind 13.s but my trap speed are 115+ but then again i have also gone 12.6 @113 when there was traction compound on hte ground.

 

[Rviscosi]

The gtech ET is accurate as long as it is mounted properly and you run on a level road. The problem is the gtech reads a higher trap speed than the dragstrip due to the 60 ft. or so long trap averaging your speed at the dragstrip. Flavio is not actually getting a 115 mph drag strip trap speed, at the dragstrip he would be getting a 110 mph trap speed. I have verifyed this by running my car with the gtech at the dragstrip and it was within .02 sec but read 5 mph high. It will be tougher than you think based on this. Definitely lose the passengers and I took an easy .4-.5 sec. off my ET's with dr's, but then again I'm not a good clutch slipper.