I've seen onfire make a reference to that fact that we should go for a 12.7:1 AF on a Dynojet because it's similar to 13:1 on the street. I'd like to see validation of this since I am seriously considering buying an hour of dyno time at FLP.

My ideal is go have 13:1 at the track.

 

Everybody I talk to that seems to be "in the know" says the same thing. Dyno load is less than the street. Shoot for about .4 less than what you want.

I myself am shooting for a 12.1 on the dyno which I am told by numerous people will be about 12.5 on the street. Supposed to be just right for FI.

 

I can't/won't say what an ideal AF ratio is on a Dynojet, but I will concur that the engine does not see the same load on the rollers as it does in the "real" world (unless you have about a 2500lb. car). I may be off on the weight, but you get the idea...

 

Well JULIO at CARTEK seems to know EXACTLY where to target your A/F in relation to DYNO and TRACK...

Glad he's tuning and buildin my LS6 Setup <img src="gr_grin.gif" border="0">

JS

 

I'm not sure if it is standard, but I believe it was said that our local dynojet drums are set up to duplicate a vehicle weight of 3,000#.. our cars would be under more load when moving themselves, versus moving the 3000# rollers..

also factoring in is wind resistance.. which puts more and more load on the car the faster it goes.

 

Thx guys, let's see some validation of this.

JS, wow, that was very helpful.

 

When I was talking with the dyno operator while he was strapping my car down he said the drums weight 1600 lbs each. At 3200 lbs we wouldn't we too far off. Something else to look at is how much the increased air changes the A/F ratio. The increased flow seems like it would lean out the mixture some.

 

John just call Julio
I'm sure he will lend an ear...

Wasnt trying to sound Cocky.
But u sure took it that way...

I gotta rember PSJ = SENSITIVE <img src="gr_grin.gif" border="0">

Just kiddin John

Joel

 

Via Autotap my 02s were low .800 on the dyno and .880 on the street.

 

[quote]
Well JULIO at CARTEK seems to know EXACTLY where to target your A/F in relation to DYNO and TRACK...
<hr></blockquote>

Sure he does. That must be why the only Cartek cars that run good are the ones that they race themselves.

Anyway shoot for 12.7-12.8:1 on the dyno, which should get you near 13.0 at the track, but remember every combo is different. Don't be afraid to play with the tuning at the track.

 

JS, I am trying to cut down on my legendary amount of fone calls I used to make.

Any more opinions?

 

First of all, never question onfire....heh,heh,heh,...lol.....John,email Dave Inall...about a year ago we traded emails on dynojet a/f vs track load a/f when I was thinking about buying a wideband o2 sensor...Dave was very helpful and has done dynojet vs track vs engine dyno a/f tests....two things I firmly believe...1. dynojet doesn't replicate track load so a 12.7 is actually around a 13.1 2. make sure the sensor is placed before the cat if you use cats.....food for thought...how many seconds does it take you to accelerate from 50 mph to 130 mph on a 4th gear (3rd auto)dynojet run vs 50-130 on the street....quite a bit different!

 

[quote]Originally posted by onfire:
<strong>First of all, never question onfire... hehe, hoohoo, haha... Food for thought... How many seconds does it take you to accelerate from 50 mph to 130 mph on a 4th gear (3rd auto)dynojet run vs 50-130 on the street... Quite a bit different!</strong><hr></blockquote>

That is a very good point, I would then expect to be more lean on the street since there is much more load. More work for the injectors too.

 

[quote]Originally posted by onfire:
<strong>John, email Dave Inall...about a year ago we traded emails on dynojet a/f vs track load a/f when I was thinking about buying a wideband o2 sensor...Dave was very helpful and has done dynojet vs track vs engine dyno a/f tests</strong><hr></blockquote>

You mentioned Dave Inall, for the rest of the people that don't know, he is the Incon Turbo guy. You have to approach a forced induction car totally different than an N/A car. A forced induction car that uses an FMU will go all over the place on a dyno. I have seen combinations go 13.3:1 on a dyno, then drive immediately to the track and run so rich that they popped and sputtered all the way down the track. $400 wasted on a day's worth of dyno tune only to go slower. Boosted combinations are very much load sensitive and the fuel curve is usually very sensitive as well when an FMU is used. That's just one of the many reasons I don't care for an FMU. Match the injector to the targeted power level and run it 1:1. <img src="gr_grin.gif" border="0"> But that's just me.

A dyno is just a way of getting a ballpark figure of how everything is working together. On a car that is N/A, it doesn't matter a ton if the car is 12.8:1 or 13.1:1 on the dyno. Keep in mind, your fuel/air will more than likely not be a constant while you're making a pass down the 1320 unless you are using an aftermarket fuel management system with wideband correction capabilities such as the Speed Pro SEFI8LO for examble. Tuning a car is all about looking at every variable and knowing where to pull fuel, add fuel and adjust timing tables. If you're tuning a car to drag race, the tuning should be done at the track. Dynos are nice for comparison's sake but they are not a concrete way of making a car run the numbers. Also, be weary of anyone telling you to make a car run X fuel/air ratio. No two cars are exactly the same, they will all like something a little different. Keep in mind that not all wide bands are created equal, what reads 13.1 on one is not always the same on another. Electronic gadgets are great but what matters is how long it takes to get from the starting line to the finish line. The bottom line is, keep an open mind and don't be afraid to try new things.

<img src="gr_tounge.gif" border="0">

 

My .02c's:

My car (stock) runs leaner the faster it goes.
First gear gets the same AutoTap 02's, but by the time I go through the lights, it's about 0.05 leaner than the dyno.

 

Bernie is dead on. Turbo cars are *very* sensitive to load. Not only does your a/f ratio change, but your boost curve does also. Even dynos which have the ability to hold the car at a certain rpm will not mimic the trac since transient fueling conditions are not the same as static.

But as has been pointed out, even NA cars will vary their a/f ratio. From what I understand the inertial load of the dyno is equivalent to a 2800lb vehicle. As you put more load on the engine your a/f ratio's will lean out. This is why McRat sees leaner conditions at higher velocities; he is in a different gear, and so has a greater load on the engine.

The dyno is a tuning aid, but it should be kept convservative; the agressive changes should only be made at the track/in operating conditions.


Chris

 

Terry last time I checked didnt CARTEK have the quickest and fastest H/C C5 in the COUNTRY? 11.16@123+

What about the COUNTLESS 11.7 or better C5 H/C cars that roll outta Cartek?Or is that a miirage too.

Oh thats right it RELLY was YOUR MMS STAGE 9000 400RWHP Monster that could only muster a 12.2? BWAHHHH BWAHHH BWAHHH


Terry its time for your meds
Mental illness must be tuff

I waiting to hear how much money u make a yr and how great u r and how many F-bodies u had and how u blah blah blah....


JS
Lets just wait and see what I run Terry

 

Cartek is ok, they are no better or worse than any of the other new comer fly by night LS1 performance shops (Thunder Racing, More performance, Jay Fisher Racing, etc)

[quote]
Oh thats right it RELLY was YOUR MMS STAGE 9000 400RWHP Monster that could only muster a 12.2? BWAHHHH BWAHHH BWAHHH
<hr></blockquote>

Actually it ran 11.3 (note: quicker than your car)… but on motor it ran 12.2 with a 2.0 60' time, and it was a "stage 1" setup. Heads cam only cost $1500 brand new (no lip service discount like Cartek is giving you). I was happy with the setup, I spanked Z06's left and right at my local tracks. <img src="gr_images/icons/wink.gif" border="0">

[quote]
I waiting to hear how much money u make a yr and how great u r and how many F-bodies u had and how u blah blah blah....
<hr></blockquote>

You're the one that keeps bringing that up.

 

[quote]Originally posted by Terry Burger:
<strong>Cartek is ok, they are no better or worse than any of the other new comer fly by night LS1 performance shops (Thunder Racing, More performance, Jay Fisher Racing, etc) <hr></blockquote></strong>

terry, wtf are you talking about?? <img src="images/icons/confused.gif" border="0"> i have bought a ton of stuff from both more and thunder for MANY years now and have been more than pleased and will continue buying my parts from them. <img src="images/icons/rolleyes.gif" border="0">

[ December 21, 2001: Message edited by: wickedZ ]</p>

 

Just for the hell of it i'll chime in. My car seems to run the best @ 13.4 a/f. with no kn.