Been doing some reading on street tuning and decided do take that route when the time comes.

What I'm trying to gauge is the amount of open road that one needs to do a full street tune (i.e. WOT idle up to redline in gear x,y,z). I think that those of you who do quarter-mile racing would have a better feeling for this than others.

The reason I'm so concerned is that I live in an urban town, and I don't think there are many open roads around here... so I was going to factor in the cost of towing my car elsewhere or having everything assembled at another location.

As a sidenote: anyone out there have video of a street tune? Also, I would like to hear success and/or failure stories of those who street tuned; in particular, those who street tuned first and went to a dyno later. It would be interesting to hear from anyone who ran into cops or had some other problem while street tuning. Thanks for your help.

 

I usally go near my house where there is like a 3 mile open strech of road.. I make one pass at like 10 mph over the speed limit as to see if there are any cops taking radar there.. If you do get stopped doing 55 in a 45 you have a good chance of talking your way out of it.. Your not getting away with 100 in a 45 .. I find the best way to tune is a 3rd gear pull..

 

same here. I go at night to an open 4 lane strech of rt1. check for cops and then do 3rd gear pulls up to redline. Also check 4th up to redline once too, but thats kinda risky i guess. It works out perfectly becasue there is an exit right by my place so I can just shoot off the exit, burn a new chip, and go try it out with less than 5min of non productive driving.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bailhatch &raquo;</TD></TR><TR><TD CLASS="quote">Also check 4th up to redline once too, but thats kinda risky i guess.</TD></TR></TABLE>


Why is it risky to do it in 4th gear? Takes to long to reach redline, therefore higher chance of getting pulled over?

 

i think it would be kinda risky in 4th because at what mph do alot of cars meet redline in 4th...120ish...

 

OPEN ROAD.. if a cop pulls you over jsut tell him you were tunning your 400+whp street car.. He will understand..

 

There are 2 interstates that interesect near my house. both of which have long entrance ramps. I just go down the ramp up to the next exit and back again. plenty of room, no down time.

 

Hate to jack my own thread, but... this is related.

Does anyone know what the RPM variation is with time under WOT, for a given gear (assuming that tires are not spinning) and car? I was thinking that you could calculate the distance traveled under WOT acceleration for a given gear and car (weight, power/torque, tire diameter, gear ratio) by relating gearing and car variables to engine speed and power. To do this calculation, I'd have to have dyno data for a similar car to the one I'd be using (since the engine power changes with RPM). It would be enlightening to do the calculation, neglecting air resistance and among other things...

So what I'm thinking is that

1. get RPM variation with time
2. convert 1. into tire rotational acceleration
3. convert 2. into tire rotational velocity
4. convert 3. into a translational velocity
5. find the time it took for you to travel at the max speed in given gear (i.e. for LS trans, standard wheels, 4th gear ~= 110 Mph)
6. convert 4. into translational distance
7. find the distance which correponds to the time you picked off from 5.

What do you guys think? It would be interesting to have you guys measure the distance on your odometers and compare that to a calculated value for distance. Before I get out there with my car, I want to find a road with an appropriate distance of open stretch.

It would also be interesting to compare actual vs. theoretical quarter-mile times and speeds with this approach by computing one displacement curve and velocity curve per gear and then accounting for the gear changes by using the final value of displacement and velocity for the current gear in the subsequent gear (of course, the theoretical value would yield faster times, since what I proposed assumes perfectly sticky tires, instant gear changes, and no air resistance--and probably some other things I forgot to note). Just a thought....


Modified by mdpalmer at 8:42 PM 8/11/2004


Modified by mdpalmer at 8:43 PM 8/11/2004


Modified by mdpalmer at 8:44 PM 8/11/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bailhatch &raquo;</TD></TR><TR><TD CLASS="quote">same here. I go at night to an open 4 lane strech of rt1. check for cops and then do 3rd gear pulls up to redline. Also check 4th up to redline once too, but thats kinda risky i guess. It works out perfectly becasue there is an exit right by my place so I can just shoot off the exit, burn a new chip, and go try it out with less than 5min of non productive driving.</TD></TR></TABLE>

rt1 where????

 

i have a big "square" section of country roads that i do my tuning on..each of the roads have a decent straight section so i make a pull, adjust then turn on the next road, do a pull, adjust, turn on the next road..ect.ect...i usually do it all in 3rd then a couple pulls in 4th to make any minor adjustments..there no good roads around me that are flat/straight enough to do a pull from 3000-7500rpms in 4th gear on.

just make sure that if you keep doing pulls on the same road that there isnt people out in their yards or anything that would call the heat on ya

 

If there are no good spots around to do decent pulls,
then why not just concentrate on the part throttle tuning for the time being
until you have a chance to get to a decent spot. Just have to keep out of boost
I know i couldnt

 

Does it matter if the road youre tuning on is up a hill or should it be flat road?

 

Hmm... that sounds like a plan, but I wonder wha tthe drivability is like when you slam on the throttle. Does anyone know what the rationale is behind street tuning in 3rd and fourth gear almost exclusively? It seems that a lot of people do this.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tgreaves &raquo;</TD></TR><TR><TD CLASS="quote">make one pass at like 10 mph over the speed limit as to see if there are any cops taking radar there.. If you do get stopped doing 55 in a 45 you have a good chance of talking your way out of it.. Your not getting away with 100 in a 45 </TD></TR></TABLE>

lol, or you could just buy a good radar/laser detector. If you plan on driving fast on public roads, this will assuredly pay for itself. I cheaped out for years, without ever getting pulled over, then got a $400 ticket (doing 67 in a 35, even though it's a 4 lane semi-rural highway). Luckily, I saw the flashing lights and slowed down, since I had just topped out 3rd.

A good trick I use is to find a long, steep on-ramp or hill, then you can do 2nd/3rd gear pulls, and it will take as long as a 4th gear (or longer!) but you won't be going ungodly fast at the end. You get more data points, and don't have to worry (too much) about getting a ticket, or killing someone

 

So uphill is better?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tgreaves &raquo;</TD></TR><TR><TD CLASS="quote">

rt1 where????</TD></TR></TABLE>

well it goes from the Florida keys to central Maine. I'm in southern maine. mad imports, err i mean trucks.

 

Try industrial/warehouse areas at night.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mdpalmer &raquo;</TD></TR><TR><TD CLASS="quote"> I was thinking that you could calculate the distance traveled under WOT acceleration for a given gear and car (weight, power/torque, tire diameter, gear ratio) by relating gearing and car variables to engine speed and power. </TD></TR></TABLE>

Two answers-
1) Get a g-tech, it figures out power by acceleration

2) Sure, you can do it, as long as you can ignore wind (or estimate it).

force = mass times acceleration
work = force times distance
power = force times distance divided by time.

Unfortunately, your resolution would have to be REALLY small in order to make a curve out of it, otherwise your power will be an average from, say, 6000-8000 RPM. Also, you'd have to add in what the force/power subtracted by wind is. MAYBE if you're datalogging and can get an excel spreadsheet /csv with RPM and elapsed time, you could make a nice power curve. We could pretend to know how wind affects it too.

Just because I'm bored, I'll figure out how to calculate your power based on acceleration (speed vs. time, or RPM vs. time)

Let's assume your 3rd gear is 8000 RPM and goes to 80 MPH.
(EDIT: If you know your gear ratios, wheel diameter, you can calculate this. But observation is just as good. You need to convert RPM to speed either way.)

Let's also assume your car + gas, driver is 2800 lbs (1270 kg)

80 MPH (statute miles) equals 128.748 Kilometers per hour, or 35.76 m/s

First, find the acceleration.

(For a stupid example, let's say data point 1 is at time 0.00 and RPM 7000, and data point 2 is at time 0.90 and RPM 8000). (side note, this turned out to be a rather realistic example.)

1) convert RPM to meters per second
8000 RPM = 35.76 m/s (from above assumption that it is 80 MPH).
7000 RPM = 7000/8000 * 35.76 = 31.29 m/s

2) use change in speed to calculate acceleration
35.76-31.29 = 4.47 m/s (change in speed)
0.90 - 0.00 = 0.90 (change in time)

4.47/0.9 = 4.967 m/s^2
Hey, this is about 0.5G's in acceleration at the top of 3rd, sounds like a fast car so far!!

3) Use acceleration to calculate force
f=ma
f = 1270 kg * 4.967 m/s^2
f = 6307 kN (kilonewtons?)

4) Use force and speed to calculate work.
work = force times distance.
distance = Vi * T + 1/2 at^2
(initial velocity times time, + 1/2 acceleration times time squared)

distance = 31.29 * .9 + 1/2 (4.967)(.9^2) = 32.18 meters

work = 32.18 m * 6307 kN = 202986 kilojoules?

5) Use work to get POWER (finally)

power = work/time
power = 202986/.9= 225540 kilojoules/sec

That's 302.454 WHP - wind!


**** that was a long post, enjoy! If you don't think you can repeat this, give me:

1) comma separated values with time and RPM (or preferably speed)
2) your (est.) speed at a particular RPM
3) your (est.) weight of your car.

and I might have time to churn you out a spreadsheet. I might even get you a graph!

-Chris
ccfries@yahoo.com

 

Wow, that was a long post! There are a few things I want to mention:

1. I was asking for the distance traveled under WOT from xxxx rpm to yyyy rpm in a given gear + car NOT the power required to accelerate a given car from xxx Mph to yyy Mph

2. <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ccfries &raquo;</TD></TR><TR><TD CLASS="quote">

Two answers-
1) Get a g-tech, it figures out power by acceleration

</TD></TR></TABLE>

Hmm... didn't think about that. Good idea. I heard those devices are not trustworthy (yeah, yeah, it's some rumor I am perpetuating... so sue me)

3. <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ccfries &raquo;</TD></TR><TR><TD CLASS="quote">

2) Sure, you can do it, as long as you can ignore wind (or estimate it).

</TD></TR></TABLE>

I mentioned this in my post. The point of my (as yet undone) calculation was to get an OOM (order of magnitude) type of result (i.e. is it something like 0.5 mi or maybe more like 5 mi?) and compare that to what the guys are actually seeing when they go out... sort of a "just for the hell of it" kind of thing... the other stuff about quarter miles and such is more of that kind of thinking. I'd imagine that the calculation I want to do would be an OOM better than the one you've done here. But hey, I'm a big dummy and I don't know anything anyway!

4. <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ccfries &raquo;</TD></TR><TR><TD CLASS="quote">

force = mass times acceleration
work = force times distance
power = force times distance divided by time.

</TD></TR></TABLE>

That's correct. But there's a caveat for our case (in the problem I wanted to consider): the force (and thus the acceleration) is changing with time. That's why I wanted to get data points from someone's dyno run. In mathematical terms, work is the integral of force over some distance and power is a derivative of work with respect to time. We'd have to compute these things numerically to get the answer I want.

5. <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ccfries &raquo;</TD></TR><TR><TD CLASS="quote">

4) Use force and speed to calculate work.
work = force times distance.
distance = Vi * T + 1/2 at^2
(initial velocity times time, + 1/2 acceleration times time squared)

distance = 31.29 * .9 + 1/2 (4.967)(.9^2) = 32.18 meters

work = 32.18 m * 6307 kN = 202986 kilojoules?

</TD></TR></TABLE>

The formula for distance you've applied assumes a constant acceleration... not what I wanted to do.

6. <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ccfries &raquo;</TD></TR><TR><TD CLASS="quote">

**** that was a long post, enjoy! If you don't think you can repeat this, give me:

</TD></TR></TABLE>

Yes it was!! Thank you for answering. If you don't agree with me, or you just don't understand what I was thinking, I'd be more than willing to discuss further.

 

I think you should first tune part throttle and then work on the WOT, because if you do WOT first, and part-throttle later, WOT values will change.

 

I would say get on a turnpike where is less chance of a cop being there.

 

Hmm. Sounds good, but I don't know what a turnpike is. Can you define it for me? Thanks for the suggestion.

 

Sounds like a good idea. But you live in LA; have you found a good spot with a long enough strectch for you to do WOT runs in 3rd and/or 4th gear?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mdpalmer &raquo;</TD></TR><TR><TD CLASS="quote">1. I was asking for the distance traveled under WOT from xxxx rpm to yyyy rpm in a given gear + car NOT the power required to accelerate a given car from xxx Mph to yyy Mph
</TD></TR></TABLE>

You can't get that, unless you can integrate your torque curve (force) over time

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mdpalmer &raquo;</TD></TR><TR><TD CLASS="quote">4.

That's correct. But there's a caveat for our case (in the problem I wanted to consider): the force (and thus the acceleration) is changing with time. That's why I wanted to get data points from someone's dyno run. In mathematical terms, work is the integral of force over some distance and power is a derivative of work with respect to time. We'd have to compute these things numerically to get the answer I want.

</TD></TR></TABLE>

If you have enough data points (say, from a datalog) you don't have to worry about that. You would be essentially doing the integral as your dT approaches zero.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mdpalmer &raquo;</TD></TR><TR><TD CLASS="quote">If you don't agree with me, or you just don't understand what I was thinking, I'd be more than willing to discuss further.</TD></TR></TABLE>

Yeah, I know what you're getting at... but I don't think you'll have the precision to make any sort of power or distance judgement without a log. Even the distance travelled would have to be a guesstimate unless you have an equation to represent your torque curve (and the force of wind).


Someone posted in the Type R forum (I think) that they used a g-tech to get their 1/4 mile time, and it was within .1/.2 of what they expected.

Ah well, good luck! Maybe you can use a GPS to get your data


Edit: Turnpike is a tollway, generally.

 

I just used about a 1/4 mile and 2-3 gear pulls.