I've been going down to the track as much as I can to get more seat time, and just wanted a little information.

Granted powerband, weight, and traction are all differentiating factors between the two, but I was wondering why, from a technical standpoint, do N/A cars trap lower speeds and post lower times then say a turbo car at the same mph?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by a1320addict &raquo;</TD></TR><TR><TD CLASS="quote">I've been going down to the track as much as I can to get more seat time, and just wanted a little information.

Granted powerband, weight, and traction are all differentiating factors between the two, but I was wondering why, from a technical standpoint, do N/A cars trap lower speeds and post lower times then say a turbo car at the same mph?</TD></TR></TABLE>

Comes down to average power/torque and powerband and weight is a big factor. Traction is definately an issue to. This used to really puzzle the hell out of me, NA VS Turbo weird

Drive a High HP car, instant torque and pretty linear, turbo laaag then BAM starts pulling like a freight train.

 

Terry, thanks for the reply. The whole scenario definently confuses me. Weird.

 

i think traction plays a big part on why NA cars are so quick...and HP makes the turbo cars so fast...oh yea and weight of course for NA cars

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostfed.com &raquo;</TD></TR><TR><TD CLASS="quote">Drive a High HP car, instant torque and pretty linear, turbo laaag then BAM starts pulling like a freight train. </TD></TR></TABLE>

A wise man once told me, "If it pulls like a freight train, that's not necessarily a good thing considering a freight train moves really slow."

In reponse to your question, Joel, Jeff's all motor car runs 11.7-11.8 at 113-114mph in a 2180lb chassis (with driver). Gearing and power to weight plays a huge role in how fast the car is. We have customers that are street racers (not that we encourage it) weighing in at the 2100lb level with turbo setups on stock motors running mid to low 11's. They trap much higher than people making the same power in heavier cars. They E.T really well because the cars are setup well and it also helps when you have a good driver behind the wheel. If you took your setup and put it in a super light chassis, you'd probably be surprised at how easily your car would get into the 11's. Power to weight is a huge deal.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Andrea &raquo;</TD></TR><TR><TD CLASS="quote">Power to weight is a huge deal.</TD></TR></TABLE>

tell me about it Andrea

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Andrea &raquo;</TD></TR><TR><TD CLASS="quote">Power to weight is a huge deal.</TD></TR></TABLE>

Indeed. That, and traction are the two largest deciding factors on how quick/fast a car is.

 

Gearing as Andrea said is a BIG part of it. Keep in mind an All Motor that runs the same time a Turbo car does in the 1/8th usually runs a slower time in the 1/4 because of gearing and the the top end charge that the turbo car has.

Another example is this, back when I had a Drag 3 kit on my Si, I used to run consistent 7.7 1/8 mile times and 11.9 1/4 mile times, a Domestic car would run the same 1/8 mile BUT usually .2 seconds slower in the 1/4, top end charge of a Turbo Honda and I am sure gearing as well. Ever heard those ProMod cars SCREAM to the 1/8 then just sound like they coast the 1/4? Again average power vs Peak power and gearing PLUS weight

 

With the 270whp motor, we went 12 flat at 112 with 22 inch slicks and 5.02 FD.. then we changed final drives to a 4.3 and slicks to 24.5 and car went 11.9 at 113.. so now we are thinking we overslicked it and have to go back to 23 inch for the 4.3 or go to 25 inch with a 4.7, lol

So yeah gearing and slick size is key because you want to cross the line as you are maxing out your gear... So us crossing the line at 7600, is not as fast as crossing the line at 8500 with the same tranny etc...

We are new at this, so we are learning though

 

Thanks everyone for the replies. Definently no more confusion.

Andrea, great quote about the freight train..

 

You have to match your tq output from one gear to the next, 1st gear makes the most tq, and 5th makes the least. If you switch 1st gear near your peak hp rpm, you lose tons of tq at the beginning of 2nd gear, unless you switch 1st gear at least 750 rpms or more past your peak HP rpm, then the tq outputs will be much closer.

That's why there is no benefit to running a bigger turbo and less boost, because your moving your peak hp point higher in the rpms, unless you increase more engine speed in 1st and 2nd gear to match the tq output of the next gear, but you sacrifice engine life depending how high you go.

Same goes for NA combinations. If you have two 2000 pounds cars, one having 200hp peak, and the other having 240hp peak, both can still trap at 114mph.

Most combinations you see have their peak hp rpm at their rev limit, which only slows you down. That's why trap speed is not an indication of HP, especially peak hp.

I.

 

Power, Weight, GEaring and power band