Ivan@AMS

Yes, with poor boost control, your boost (load) can change from gear to gear. Put a NA car on a dyno and do runs in each gear and you will see very little change in HP.

9sec9

iTrader: (2)

As a matter of fact, with Trent and I BOTH watching my car be dyno in 3rd gear, we saw the number BELOW 500 whp. Then, same tune, same day, same dyno the car Jumped to 526 or so as soon as David went to the 4th gear pull. Maybe the dynos are different in Chicago.

9sec9

iTrader: (2)

Using that analogy, you would be saying that every person dynoing their car at a certain boost level and doing a 3rd gear pull would be overshooting their tuned boost when their on the track. If a person tunes to 3rd gear and disregards what the boost does in 4th, they've missed the boat completely. Then, if they did go to 4th for the final tune (just to see where the boost was) they would need to tune for the higher boost. If they tuned for the higher boost, they would more than likely post that figure as their 'Peak number' since it would be higher. Not too many people would fall back to a lower peak number when talking about what their car made.

Ivan@AMS

Like I mentioned. If you have poor boost control, you boost can change gear to gear. Like I also mentioned, spool time will change.

I ran a dyno for 6 years at the last shop I worked at and run the dyno at AMS on a fairly regular basis. Thats 10 years and thousands of cars........

I would be happy to put my NA 240sx on the dyno tomorrow and make some pulls and show you what I mean.

Your statement that a dyno pull should be done in a 1:1 gear is not correct. Your statements about gear leverage and stuff has no bearing.

It makes no difference to HP unless its doing funky stuff with your boost.

Ivan@AMS

It seems that dyno your using has some funky readings based on the numbers from the Wilson intake test. I would attribute that to the dyno you were on. Try a Dyno Jet maybe?

RazorLab

iTrader: (8)

I'm going to have to agree with this.

On our mustang, if you do the proper synch in each gear, and have good boost control the HP will be VERY close. The peak torque number will go up a tad because the boost hits sooner in the RPM range.

If you *do not* synch the car for the 4th gear pull (and it is synched for 3rd still), then I have seen the numbers change.

Here is an example from our mustang dyno:

3rd gear, roller speed synched for 3rd gear at 3,000 rpm:



4th gear, roller speed synched for 4th gear at 3,000 rpm:



See above.

9sec9

iTrader: (2)

Wow, mechanical advantage IS a factor. I guess I'm going to have to re-learn everything that I know about gears, why we use gears and what their 'mechanical advantage' is when we use them. A gear was designed to do more work with less force over a longer period of time. Some things don't change, regardless of the number of years of experience. Let's stay on my 'correction'. Your statement said I was incorrect with 'numbers' being higher in a 4th gear pull. You stated that the 3rd gear to 4th gear difference was minimal. Regardless, first of all, of the reason WHY the 4th gear number is higher, whether through boost, or less mechanical advantage ( I would actually say BOTH), the fact remains that 4th gear will ALWAYS give higher numbers than 3rd, provided that 4th is closer to a 1:1 ratio. Are you saying that you dispute that fact?

2highpsi

iTrader: (15)

Would the fact the a dynojet is not load bearing have something to do with it not being affected much by gear?

Ivan@AMS

I am not sure what you are trying to say.

You should always tune for the highest load your car will see. Tuning the car in a lower gear does put less stress on the motor / drive train and its a good thing to do to get the tune close. Making a pull in higher gears afterwards is needed to check and tweak the tune. Making pulls through all gears is also a good idea. Making pulls and tuning during actual driving (drag strip) is the best.

As far as setting boost is concerned. Yes, higher load has the potential to create more boost. With closed loop boost control and a proper WG system its not as big of an issue.

Of course a person is going to post their best dyno chart.

9sec9

iTrader: (2)

Not sure, but EVERY book I have and every post I've read by many tuners such as Ford's own race teams have stated that ALL dyno pulls are to be done in the gear that is closest to 1:1. I have a tendency to believe that, since I've observed differences in 3rd and 4th gear pulls and these professional teams have reasons for stating that. I would tend to listen to their advice. Razorlab, I hear what you're saying, my only comment on that would be then, Why would the statement be made that most pulls are done in 3rd gear then, if they were both of equal value? I think that AMS has successfully hijacked another thread that had nothing to do with them or their car. It has to do with Trents car. I'll always keep an open mind to being corrected. I can handle that, since I'm not all knowing. What I don't keep an open mind on is how someone continues to create havoc in a Buschur oriented thread that just happens to be getting attention. Maybe it's a habit that should be broken. I wonder what Dynojet and Mustang recommend for doing dyno pulls?

9sec9

iTrader: (2)

And which gear do you think that their best dyno chart was made in? 3rd or 4th?

RazorLab

iTrader: (8)

I personally prefer to do the bulk of a tuning session in 3rd gear as 4th gear is longer, espically on the 03-05 5spd evos and it ends up creating a shiat ton of heat over the tuning session. This could be my style of tuning though as I just keep doing pulls without cool down because a large bulk of my customers us their evos for circuit use and they go WOT lap after lap after lap so I like to beat up the evos on the dyno like they would out in real life.

I do check tunes in 1st through 4th though. I had a thread I created earlier this year that touched on different gears and loads, etc. I think I remember you posting in it as well. I believe it was called "mustang load = street load?" or something like that.

I have data in that thread that shows pretty close to the same load in different gears. A foot note to this would be that I use ecu-controlled boost which has error correction that works quite well to keep the tuned boost within it's tuned parameters, no matter the gear, etc.

I can tell you that if you synch the rollers to the rpm in the gear you are going to do the pull, and resynch it if you change gears then your power should be very close, at least this is what I have seen a ton of times on our mustang dyno.

Ivan@AMS

Here is what you need to understand about Dynos. They read roll TQ and then calculate HP from that. The TQ that you see on your dyno chart is NOT the TQ that the dyno measured. This is ALSO calculated. You create THOUSANDS of lbs of TQ at your wheels and the dyno calculates that reading back to 1 ft from the center of your crankshaft. The mechanical advantage is taken out of the equation by the dyno.

How do you figure 1:1 ratio is the proper transmission gear to be in when there are hundreds of different final drive ratios?

The added gear friction of the higher load of 4th gear will probably reduce the HP number on a dyno slightly over third gear. If you are seeing higher numbers in 4th gear (besides in spool up) then your boost is going up or your dyno is broken.

There is always the possibility that on a MD dyno with RPM done off of wheel speed that tire growth is a factor in messing up the charts..... another thing to think about.

Ivan@AMS

Exactly my point. Thanks for sharing.

David Buschur

iTrader: (53)

Yes, I'd like it if 9sec240 found somewhere else to give his dyno input again. I can report the posts if needed. A thread was closed/locked/deleted in the AMS section today that I went in to defend myself and Jarrod by request of AMS. Go somewhere else Ivan.

The MD you worked on was obviously having problems, you haven't had a good thing to say about it yet. The Dynojet's are junk, I owned on, hated it. You guys have one at AMS so it is the best............

Mustang Dyno suggests dyno'ing in the gear that is closest to 1:1.

The power goes up in each higher gear (except maybe overdrive as I only tried it once and it didn't work well at all, might have something to do with mechanical advantages of gearing.)

If I dyno a car in 1st gear the power sucks, 2nd it sucks but not as bad, 3rd it gets close to where it should be and 4th the power goes up again to what we usually post.

I would say 90+% of the charts I post are posted from the 4th gear pull.

My RS however, is usually only 3rd gear. I have stuck with 3rd gear in my car because when I was doing all the intake testing I didn't want to load the car so long and hard in 4th gear for hundreds of runs. I did all those baselines in 3rd and have just kept dyno'ing the car in 3rd since then.

The boost going up is NOT why the power goes up. The boost varied on Tom and Trent's runs less than 1 psi.

Just because the Wilson intake testing smoked the AMS intake manifold doesn't mean the dyno numbers are "funky". What kind of crap statement is that.

Go away already, stay away.