Analyze These Performance Changes

Background: My car has a Vigilante 3600 converter, 4.30 gears and 29” slicks. Earlier this year I was getting 1.51 60fts, although, I’ve had some 1.50s and 1.48s in the past. In typical air at our local track my car was running 11.10s at 120 MPH. Recently my 60fts have been in the high 1.50s (1.57s-1.59s) and also somewhat inconsistent. So, I decided it is time to make some changes and adjustments to my car to improve the weight transfer on the launch in hopes of getting consistent 1.50, 60ft times.

With all the weight reduction, the back of the car appeared to be too high (2 ½”+ gap, slick to wheel well). So the first change was to replace the rear springs and reduce rear the static ride-height by about 1 ½”. I also changed the pinion angle from 3 to 2 degrees.

Next was to lighten the front end with a new tube K-Member and A-Arms (-60 to 70 pounds). Also, the front QA1 coil-overs were reset to “0” and adjusted down ½” on the front ride-height.

Here are the track results following the changes, which are somewhat puzzling. The DA at the track was around 4000 and most car's 60ft times were off about .05 to .07 and ¼ mile ETs 2 tenths slow (at a minimum), along with a few MPH slow at the trap.

With all the changes my 60ft times were unimproved at 1.57s, but very consistent now. Everyone said the weight-transfer looked good with the car (lifting the left front about 9”). My ¼ mile ETs were 11.35s, typical for the air conditions (2 tenths slow due to air).

Now here’s the kicker. All my trap MPHs are now over 123+ MPH, with the last run at 124+! “WOW!” Also, in bad air and everyone else was way down on MPH due to the air.

So, where did all that trap MPH come from? Did reducing the ride-height by 1 ½” add 3 to 4 MPH?

WD

i was going to take a stab at it but its over my head. Sorry bud, best of luck.

Re-check your pinion angle, first. It may have been somewhat "bound" and your "new angle" is freeing this up.

Did you get your convertor restalled for the new race weight? It doesn't sound like it.

If you re-did your front shock settings maybe the car is recovering better after the launch and the front is "porposing" less and scrubbing less forward momentum?

I'm curious, what rear springs did you swap to?

Re-check your pinion angle, first. It may have been somewhat "bound" and your "new angle" is freeing this up.

Did you get your convertor restalled for the new race weight? It doesn't sound like it.

If you re-did your front shock settings maybe the car is recovering better after the launch and the front is "porposing" less and scrubbing less forward momentum?

I'm curious, what rear springs did you swap to?

The pinion angle was checked with a high-tech digital instrument. So, I'm sure the pinion angle was correct previously (-3 degrees) and currently at -2. I don't think 1 degree could make that much difference.

The car weight without driver is now down to 3240 and I don't think the converter would be a major issue. It seems to be working well flashing it off the line.

I've had two different sets of rear springs in the car the past two weeks. The ones in the car now are Eibach Drag Packs that have been cut-down and reworked by a spring shop locally. I goal was to reduce the rear ride-height by 1-1/2".

WD

Maybe the car being lower, not getting air under it so it helping a little.

1 degree could free up quite a bit but I would guess maybe .5 mph or so.

The wt. sure helps alot too. for better MPH.

Where does your converter flash?

Its odd the 60' didn't improve, is it possible you think its lifting too much?

Mine was pulling up hard, but when I got it just barely pulling them the 60' picked up 2 tenths

Maybe the car being lower, not getting air under it so it helping a little.

1 degree could free up quite a bit but I would guess maybe .5 mph or so.

The wt. sure helps alot too. for better MPH.

Where does your converter flash?

Its odd the 60' didn't improve, is it possible you think its lifting too much?

Mine was pulling up hard, but when I got it just barely pulling them the 60' picked up 2 tenths

One of my friends watched me leave every round and said it looked good. Only lifting about 9 inches at the most and that it looked very controlled (according to him). Also, I didn’t feel a hard bounce as it came down.

The recent weight reduction was only the K-member and A-Arms (maybe 70 pounds at most off the front).

Again, with my changes I was expecting better 60fts along with an ET improvement. The huge trap MPH increase is a really big surprise. It can't be a fluke either; I had three 123+ MPH in a row and then one 124. And other racers were below their typical trap MPH with the air conditions.

WD

The trap speed could be an effect of lowering the the ride height. The height of the long nose while going thru the traps can sometimes trip the sensor rather than the tire.
We had a couple of years at or local track where one lane showed about 3 mph faster than the other with the 60' and et being the same. Figured that it had to be that the sensor 60' from the end was tripping on the tire like it's supposed and the final sensor was tripping on the body to showing that the car covered that 60' faster and that's how mph is calculated.

The easiest and least high tech way to measure pinion angle, angle finder on face of cylinder head write that number down, angle finder on rear cover write that number down and subtract the 2 numbers. I know you know this but others may want to know. I still can see a full mph from this especially if the driveshaft is a touch too long and you didn't realize it.

70-100 lbs can change things up quite a bit with a tight convertor like you have don't under estimate loosing this weight. I can see you not picking up much sixty foot because the convertor is not working as hard if that make sense. Maybe try another technique for leaving. I can also see the mph increasing some because the convertor will be more efficient in getting the slippage taken care of quicker.

I just noticed you said on your first post you said your cars 60' were getting inconsistant, I would pull it out and have it re-done especially since you bracket race. You could have a sprag going bad or bent fins or ???? I'd be willing to bet that this is your issue.

What does "reworking" mean when you had them cut them down? How does this spring rate compare to your last pair? I wouldn't discount this as part of the reason why your cars sixty foot didn't pick up. The last time I tested rear springs they all had the same ride height, however they definately didn't produce the same 60'

The trap speed could be an effect of lowering the the ride height. The height of the long nose while going thru the traps can sometimes trip the sensor rather than the tire.
We had a couple of years at or local track where one lane showed about 3 mph faster than the other with the 60' and et being the same. Figured that it had to be that the sensor 60' from the end was tripping on the body and the final sensor was tripping on the tire like it's supposed to showing that the car covered that 60' faster and that's how mph is calculated.


Unless his car rode with the height of an old gasser or there is an extreme dip in the track the beams are higher at the end of a track than at the 60' clocks, IHRA/NHRA made this adjustment x years ago. His ET would increase to correct???

The trap speed could be an effect of lowering the the ride height. The height of the long nose while going thru the traps can sometimes trip the sensor rather than the tire.
We had a couple of years at or local track where one lane showed about 3 mph faster than the other with the 60' and et being the same. Figured that it had to be that the sensor 60' from the end was tripping on the tire like it's supposed and the final sensor was tripping on the body to showing that the car covered that 60' faster and that's how mph is calculated.

Yes, the down-track photo-electric cell beams and center-track reflector cones are at 6 inches above the track surface. Therefore, the beams often trip on the car body down-track, rather than the tires. Additionally, 4th Gen F-Bodies often have an issue with the front air-dam (spoiler) tripping the down-track timing beams “intermittently” due to the like-of cross-sectional area. However, my car has a fix installed to prevent that anomaly from occurring and ensure my times are consistent.

Check-out this photo and the black-tab in the center of my air-dam (I've thought of everything). Also, I couldn’t find anything in the NHRA rulebook that said the tab was illegal. Additionally, I had the same trap MPH in both lanes, so that indicates there wasn’t a glitch with the timing beams and cones (a track-lane issue).

WD

http://shutter15.pictures.aol.com/data/pictures/17/008/5E/DB/F7/1C/pzlcTUPFSVWIn-81yg6dktv1+6vONid40300.jpg

I just noticed you said on your first post you said your cars 60' were getting inconsistant, I would pull it out and have it re-done especially since you bracket race. You could have a sprag going bad or bent fins or ???? I'd be willing to bet that this is your issue.


My Vig 3600 is only a few months old and has a minimal number of runs on it. From all indications it appears to be working well and flashing to its rated stall. While my 60ft times were not great this past weekend, they were very consistent. And, most people at the track also had slow 60fts.

In two weeks I'll be racing at another track (which has just been resurfaced by Penhall) and that will give me a good compairson to the times at the local track(60fts, ET and MPH).

I also plan to adjust the front QA1s down another 1/2 inch and see if that adds even more MPH.

WD

If they become inconsistant at this new track then I'd say you have a convertor issue. Age of a convertor has nothing to do with its state of health, we've broken convertors in a weekend after installed.

Your car should be a solid consistant low 1.5 to high 1.4 sixty footer no matter what the air/track/whatever. I wouldn't settle for anything less even if it comes with a few mph.

Put a metric or a turbo 350 and a good convertor behind that beast, you'll be a low 10 second player for sure.

I have a question if you don't mind. Have your rpms at the finish line changed at all?

I have a question if you don't mind. Have your rpms at the finish line changed at all?

No, I can't see any real change in trap RPM (6580 RPM). And, it always has been completely "maxed-out" on RPM at the stripe w/ the 4.30 gears.

WD

No, I can't see any real change in trap RPM (6580 RPM). And, it always has been completely "maxed-out" on RPM at the stripe w/ the 4.30 gears.

WD

Never mind then. I new I was shooting blanks as usual, and you confirmed it. Good luck and hope you figure it out.

Interesting.Im guessing the ride height.

Interesting.Im guessing the ride height.

The 70 pounds off the front probably helped some, but the only logical explanation is the reduced ride-height which greatly improved the aerodynamics at 100+ MPH. And, that is something for everyone with 4th Gen F-Bodies to keep in-mind.

The only other possibility is something crazy happening with the converter.

Not to leave good-enough alone, today I adjusted the front QA-1 coil-overs down to reduce the front-end ride height by another inch (27" front wheel well height).

WD

http://shutter13.pictures.aol.com/data/pictures/26/007/1D/BA/1E/0B/Ed7N8CSFyXYpt5qjXxRXFztIP5twFNDv0300.jpg

mmm

WD did it pick up anymore?

Also how is your alignment set? And what front tires?

I was just going to get the sportsmans for the heavier cars..... But my a-arms are sliding around, I need to weld the washers. I'm going to lower mine some more now

Also are you using a 275 spring?

WD did it pick up anymore?

Also how is your alignment set? And what front tires?

I was just going to get the sportsmans for the heavier cars..... But my a-arms are sliding around, I need to weld the washers. I'm going to lower mine some more now

Also are you using a 275 spring?

I haven't been to the track after lowering the front another inch (no race this weekend). And next week's race (Big-Bucks out of town) will be 1/8 mile, so I can only evaluate my 60fts and 1/8 mile ET and MPH. :think:

I just had the front end aligned by the local drag race guru (Pro-Mod guy) who has a high-tech alignment shop, so he knows how to set it up correctly. The front tires are Goodyear 26" front-runners,

I can't remember the number on the QA-1 coil-over springs, but they are the softest ones.

My A-Arm adjustments haven't slipped yet (knock-on-wood). I marked them with a silver Sharpie and they are OK after a two-day race.

WD

http://shutter11.pictures.aol.com/data/pictures/24/006/37/AB/9D/15/1epYqtY0DhYPlVrwn3jNGlGcmGFlmsUQ0300.jpg

I like to break it down to hp gain. At this level every .1 ET reduction or MPH improvement is worth about 10 hp. You picked up 30 to 40 hp woth of improvement with the additional mph (120 to 123/124).

The near 100 lbs weight reduction is where 10 hp came from.

Mdacton just hit it on the rest of the improvement while you verified it; front end alignment. All of the fast guys align the front end at some optimized setting to avoid scrubing speed. Your buddy didn't get to pro-mod level by overlooking this important detail.

I agree a good front end alignment is king however the car did not pick-up ET and its sixty foot did greatly improve or improve at all, with the weight reduction (close to 80 lbs) the moving of the initial mass would have been greater (improving 60'), and the car would have been able to move itself down the track easier (improving both ET and MPH).

There was no mention of this alignment in any previous post but I can see a little ET increase and maybe 2mph.

Well who has any alignment specs on one of these?

I did mine and ran 1/16 toe in
5* caster (was told to run as much as possible)
And 0* camber..... but after the a-arms slipped I have - camber now bottoms are pointed in.....

I agree a good front end alignment is king however the car did not pick-up ET and its sixty foot did greatly improve or improve at all, with the weight reduction (close to 80 lbs) the moving of the initial mass would have been greater (improving 60'), and the car would have been able to move itself down the track easier (improving both ET and MPH).

There was no mention of this alignment in any previous post but I can see a little ET increase and maybe 2mph.

This is what snows me. In my experience I have never picked up mph with a simular 60 foot that didn't net me some et gain.

I think the caster was set to -.005 (left & right), not sure about the camber.

I hope when I adjusted-down the front-end another inch it didn't mess-up the camber mid-point. What do you think? I can also call David at the alignment shop Monday and see what he thinks.

And, yes. After I installed the new K-member and A-Arms it had to have a complete front-end realignment.

WD

This is what snows me. In my experience I have never picked up mph with a simular 60 foot that didn't net me some et gain.

I agree, the 3+ MPH gain really doesn’t seem logical with no ET improvement. Again, the DA was at 4000 + and some change, the worst of the year so far and everyone's 60ft times were down a few numbers (hundredths).

However, I have a stack of time slips from two days and everyone is 123 + MPH (except one). Here are some of the actual MPHs; 123.69, 123.40, 123.40, 123.18, 122.98, 123.28.

WD

With the DA being so high the MPH is generally the first thing that suffers, that tight convertor still is number one in my book.

With the DA being so high the MPH is generally the first thing that suffers, that tight convertor still is number one in my book.

If the 60fts don't improve at the out-of-town track this coming weekend, I'll do a converter swap. I have another Vig (3200) that I can have re-stalled possibly to 3800, or maybe 4000.

WD

is it possible, that the lower ride height and lower weight could help the converter be more efficient at the top end?

do you know if the converter is locking, or is it a locking converter?
I'm in no way an expert but the lack of 60' improvement is puzzling

if you attained the consistency you were looking for why change the converter? unless you want to be faster in class

is it possible, that the lower ride height and lower weight could help the converter be more efficient at the top end?

If that were the case then the ET would have improved too.

Hey Warren how are your R/Ts? Did they change?

I was thinking about this the other night. I may be out in left field but follow me ;) IF you are popping the car straight up out of the lights faster. So even if the car is 60ft faster it is not showing because you tripped the lights sooner simular to deep staging but with out the penalty on the top end.


Just a thought ;)

My R/Ts are .100 faster on juice then N/A ;)

W, that combination of yours would love more stall and most likely be more consistant. The increased ET would also more often make you the "hunter" instead of the "hunted".

W, that combination of yours would love more stall and most likely be more consistant. The increased ET would also more often make you the "hunter" instead of the "hunted".

That is a really good feeling when you let them out-of-the-gate first, then run them down and the win-light comes on in your lane! :D

Also, when they're trapping around 100+ MPH and I'm coming up on them at 123+ MPH. A really great rush! Hey, I knew there was a reason I'm doing this, much more exciting than golf or fishing!

Last year at an out-of-town race I was paired-up with some dip-$hit in a Trail-Blazer dialed in at 17.80 and me at 11.20. I waited "for------ever" for the tree to start, and I cut a great light and came by him at about 50 MPH at the stripe and got the win. :lol:

FYI. At our local track, 13.99 is the minimum dial for No-E. Which I think is the right thing to do. Just how long can a converter stay stalled-up? Ouch!


WD

I dialed an 11.99 year sago at super chevy.....and the car I raced was a GTO I never looked but I thought he broke til I was about 2 feet from the stipe.....he dialed a 7.60....My car blew over about 2 feet :lol: I broke out by 2 thou he broke out by 1 thou.....threw the laundry in my face and put my ass on the trailer :lol:

I dialed an 11.99 year sago at super chevy.....and the car I raced was a GTO I never looked but I thought he broke til I was about 2 feet from the stipe.....he dialed a 7.60....My car blew over about 2 feet :lol: I broke out by 2 thou he broke out by 1 thou.....threw the laundry in my face and put my ass on the trailer :lol:

Dang, at 7.60 with a door-slammer that guy could be running with the Pro-Mods! I bet his MPH was in the 170s. Ouch!

WD

Dang, at 7.60 with a door-slammer that guy could be running with the Pro-Mods! I bet his MPH was in the 170s. Ouch!

WD

I think it was faster than that.....

There is a quick 8, 10.5" shootout this weekend. I'm going to run in that...just t&t. But there should be some cool stuff there.

There is a quick 8, 10.5" shootout this weekend. I'm going to run in that...just t&t. But there should be some cool stuff there.

Good luck with the T-n-T this weekend (don't break anythink) and let me know what you run.

WD

Good luck with the T-n-T this weekend (don't break anythink) and let me know what you run.

WD

Now you went and put the whammy on him, (don't break anything). Or is this like the acting profession, (break a leg)?
Question, does a front end alignment that helps at the track have any negative effects on the street?

With skinny tires, not much except a little extra tire wear to the insides. With big tires, more tire wear and it will not corner as well.

With skinny tires, not much except a little extra tire wear to the insides. With big tires, more tire wear and it will not corner as well.

Thank you.

At our local track, 13.99 is the minimum dial for No-E. Which I think is the right thing to do. Just how long can a converter stay stalled-up? Ouch! WD

I race the street tire shootout at a local track and the turtles are in the 22 second range. So I taught myself to wait a little above idle 'till my forst yellow comes on then stall up and leave on the 3rd. No way I'm ataying stalled up for 11 seconds.:mad:

Any up dates on this?

It ran 122.4 MPH and low 11s this past weekend in really bad air (4200 D/A). And, I'm enjoying the MPH increase. Also, the weight transfer on the launch is working well with the new K-Member and front-end weight reduction.

WD

http://shutter14.pictures.aol.com/data/pictures/23/004/67/F7/31/71/bB2vXK4Z3opYaF7vih7RmCnjb8H1q-fC0300.jpg

Yes, the down-track photo-electric cell beams and center-track reflector cones are at 6 inches above the track surface. Therefore, the beams often trip on the car body down-track, rather than the tires. Additionally, 4th Gen F-Bodies often have an issue with the front air-dam (spoiler) tripping the down-track timing beams “intermittently” due to the like-of cross-sectional area. However, my car has a fix installed to prevent that anomaly from occurring and ensure my times are consistent.

Check-out this photo and the black-tab in the center of my air-dam (I've thought of everything). Also, I couldn’t find anything in the NHRA rulebook that said the tab was illegal. Additionally, I had the same trap MPH in both lanes, so that indicates there wasn’t a glitch with the timing beams and cones (a track-lane issue).

WD

http://shutter15.pictures.aol.com/data/pictures/17/008/5E/DB/F7/1C/pzlcTUPFSVWIn-81yg6dktv1+6vONid40300.jpg


Could you show where you got this mounted at. I take it that its at least 6 inches off the ground? Whats the length also. How did you mount this also. Pics would be great. We race also bracket race. Sorry:) for all the ?s

It ran 122.4 MPH and low 11s this past weekend in really bad air (4200 D/A). And, I'm enjoying the MPH increase. Also, the weight transfer on the launch is working well with the new K-Member and front-end weight reduction.

WD

http://shutter14.pictures.aol.com/data/pictures/23/004/67/F7/31/71/bB2vXK4Z3opYaF7vih7RmCnjb8H1q-fC0300.jpg

Congrats

I'm out-of-town on a business trip this week (in Kansas City). When I get back I'll take some photos of the tab and how it's mounted to the air-dam.

FYI. The down-track timing cones (60ft, 330, 660, 1320, Etc.) are approimately 6" above the track surface. Therefore, any front body-part (in front of the front tires) that is 6", or lower will trip the down-track photo-electric cells.

For example; most Super-Comp dragsters have a nose that extends about 18" in front of the front tires and is about 2" off the surface. That nose will always trip the down-track timing.

WD

http://shutter07.pictures.aol.com/data/pictures/25/002/3E/FF/F8/50/zyM3Ap5KKciLeUuOviKaME-y6XGCl6Pp0300.jpg

Thanks looking forward to the photos. I never thought about that as far as the Dragsters.Learn something new everyday i guess