VisualEchos

Lets say you have a car that runs a [B]15.4-second

silvs2knvb

What kind of car, a lot of turbo cars kick but off the line and die top end, some do the exact opposite, it depends a lot on the car itself.

mxt_77

Sounds like the sticky tires are getting you off the line quicker (which lowers the split-time for your 1st 1/8th mile), but the intake/exhaust/boost controller didn't actually increase your power at all, therefore your 2nd 1/8th mile split-time didn't get any quicker.

However, you may have also lost power... since your 1/8th mile is faster your MPH at the end of the 1st 1/8th mile should be higher, which should cause you to finish your second 1/8th mile faster, too.

BTW.. with the times you listed, I hope that this turbocharged car we're talking about is a Saab or something... 'cuz 14.1 is what a stock S2000 should run... not a turbocharged one.

ultimate lurker

Sounds like you picked up plenty of midrange, but not much high rpm hp with your mods. If you're still on the stock turbo/intercooler, its likely that you're hurting for flow at high rpms. You probably did gain 20-30 hp (or more) through the midrange. That, combined with sticky tires, will get you out of the hole and through the first couple of gears quicker.

But, if you have flow restrictions, once up top you're not making much more power than before. Depending upon your gearing and shiftpoints, you may operating at rpms that haven't seen much in the way of power gains. Perhaps you should try lower shiftpoints in the higher gears and see if that helps (dyno plots would help you identify shift points as well).

This is all speculation, and trap speeds would help further I.D. your issues.

UL

VisualEchos

Thanks for the replies guys.

The car is an '89 Mitsubishi Starion ESiR.

Stock HP is 150 (at the wheels), torque is about 210. With a 1st generation Eclipse MAS + K&N filter, a full 3" exhaust, and an EVC set to 15 psi the numbers are 210 HP and 278 torque, quite an improvement.

The stock 60 ft time is about 2.2, with sticky tires and the mentioned mods it becomes 2.0. Stock 8th mile time is 10.2, with the mods 8.9. Stock

wannabuy

The gain in the first half may be added because of the cars gearing. You may see a better gain in the front from the 1st and 2nd gear pull then the 3rd gear pull isn't as strong as you get to 1-1 ratio of fourth. My S pulls way harder in the first two gears and third does not pull as hard. This is due to the gearing of the first two gears. I like to race people from a first or second gear roll because of the advantage tot he gear and the VTEC powerband. So when you drag you see a bigger gain with the first two gear ratios and less from the third or even the fourth gear ratio by the end of the track.

modifry

Drag racing is all about the start and first half (or less) of the race. That's where you are going the slowest and where your time will be be affected most if you make improvements.

You have the answer in your post and didn't notice it. You spent almost 3/4 of your run (time-wise) in the first 1/8 mile. If you make the car faster you would expect to see the biggest gains in the area you spend the most time - the first half. You only spent 4 seconds in the second half of the race, so you will see less improvement there.

Some other things to think about :

If you let off the gas for the last 100 feet of the track, your ET will hardly change at all. (try it)

If you let off (don't floor it) for the first 100 feet you will lose a bunch of time, easily a second or more.

At the start of the race it takes you 2.2 seconds to go 60', at the end of the race it only takes you .4 seconds to cover the same ground. So if you go 10% faster both places, you gain .22 seconds in the first 60', but only .04 seconds in the last.

.

wannabuy

That sounds way better.

Fongu

Some more basic stuff to consider.

The start of a drag is usually traction limited, i.e. getting the tires to hookup to put all the power down. If you get sticker tires that improves the beginning of the run more than the end.

Basic physics, acceleration = force / mass. There is the forward thrust from drive tires. There is also a "backward" air resistence force (There are other forces too, but air comes to mind). Wind resistence increases with the square of velocity, so more wind resistence the faster you go. There is more wind resistence at the end of the run because the car is going faster, so less improvement in acceleration at the end of the run. (Disclaimer: I don't know how significant this is in a drag race, it requires some math, but there is a reason for the term "wind resistence limited"

VisualEchos

Coolness, thanks for the replies, you guys rule!