Home | Register | Login | Contact Us

 
Auto Math
Classifieds
Forum
Gallery
Games
Garage
Tech Articles
Utilites
 
FAQFAQ    SearchSearch    RegisterRegister    Log inLog in    Log in to check your private messagesLog in to check your private messages    Forum Subscriptions1/4 Mile Table 

New Best 1/4 mile ET and 60' time!
Goto page 1, 2, 3  Next
 
Post new topic   Reply to topic    SMOKEmUP.com Forum Index -> Drag Racing
View previous topic :: View next topic  
Author Message
GrandSportC3
Moderator


Joined: 11 Jul 2003
Posts: 1231
Location: Lakeland, FL
32443.62 points


1968 Chevrolet Corvette

PostPosted: Sun Jun 18, 2006 12:44 pm    Post subject: New Best 1/4 mile ET and 60' time! Reply with quote

Went to the Bradenton track this morning for Fathers Day Runday Sunday.
I was running too rich in the hot weather and before I went to the track, I went on my primary jets from 84 to 82 and gave it a try. I was also experimenting with my rear suspension and set my QA1's to 8 clicks.
My first run was far from perfect but it was a new best ET (10.943 @ 121.76 mph) with a 1.531 60' time..(tires were probably about 6+ inches off the ground on that pass) The smaller primary jets definetely helped to get the A/F leaner at launch (power-braking). I shifted too late into 3rd gear and hit the rev limiter at 7000 RPM and shifted too far and got for a second into overdrive.. It was still good enough for my new best.. I'm sure that a 10.8x would've been possible on a perfect run. The A/F was still too rich (11.9 - 12.2) during that pass (had the camera pointed at the A/F gauge and tach).
Re-jetted the carb and went on the secondary side from 88 jets to 86 jets and made another run. (I also set my QA1's to 9 clicks). The 60' time was down a little bit (by a 1/100 of a second and my ET was down a 1/100 of a second too. However, the launch seemed less bouncy in front with the QA1's set to 9 clicks. The engine was also misfiring once at about 6000 RPM on my 2nd pass..
The A/F was still too rich (12.1 - 12.3) during that pass. I didn't have any smaller jets with me, so I went home.. I do want to get the A/F close to 13.1.. I'm still far from that and there's a lot of power to be gained from getting the A/F ratio correct.

Does any of you carb experts have any idea on how small I should go with my jets to get close to 13.1 A/F?

The temperarure on my second pass was already in the 90's with very high humidity. The DA on my first pass was about 2900 and 3200 on my 2nd pass.. 10.95 in a DA of 3200 ain't bad.. That's definetely a mid 10 second car in cold weather..

Here are the time slips of todays runs (I was a little too quick at the light on pass # 2 Laughing )

Back to top
View user's profile Send private message
clay
Moderator


Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Sun Jun 18, 2006 5:14 pm    Post subject: Reply with quote

Good going!!! That's running in that kind of weather!!! Around here it's pretty much the same - mid 90's with a heat index of 104 or so - in other words miserable. I haven't really found a lot of power with jet changes, about what you are experiencing - a few hundreths or so. Mine runs better being too rich according to popular belief and the Innovate, but it runs better mph's and just all around feels better so I just kind of look at that and use the Innovate to check for repeatability and what AFR I need to shoot for in the future. Clay
Back to top
View user's profile Send private message
GrandSportC3
Moderator


Joined: 11 Jul 2003
Posts: 1231
Location: Lakeland, FL
32443.62 points


1968 Chevrolet Corvette

PostPosted: Sun Jun 18, 2006 5:32 pm    Post subject: Reply with quote

clay wrote:
Good going!!! That's running in that kind of weather!!! Around here it's pretty much the same - mid 90's with a heat index of 104 or so - in other words miserable. I haven't really found a lot of power with jet changes, about what you are experiencing - a few hundreths or so. Mine runs better being too rich according to popular belief and the Innovate, but it runs better mph's and just all around feels better so I just kind of look at that and use the Innovate to check for repeatability and what AFR I need to shoot for in the future. Clay


The main change for me was the 60' time.. The smaller primary jets raised my A/F when power braking and I came out of the hole harder...
I'll drop the primary jet size even more and will also go with smaller secondary jets. I want to work my way up to A/F of at least 12.7 - 13.1
I've seen a lot of gain on the dyno with jet changes... Some power can be found with jet changes..
Back to top
View user's profile Send private message
Big Dave
Moderator


Joined: 04 Dec 2005
Posts: 2662
Location: Tampa Florida
120504.72 points



PostPosted: Mon Jun 19, 2006 7:36 am    Post subject: Reply with quote

Are you compensating the smaller jet changes with corresponding increases in the power valve or just letting it go lean?

Big Dave
Back to top
View user's profile Send private message
GrandSportC3
Moderator


Joined: 11 Jul 2003
Posts: 1231
Location: Lakeland, FL
32443.62 points


1968 Chevrolet Corvette

PostPosted: Mon Jun 19, 2006 8:40 am    Post subject: Reply with quote

Big Dave wrote:
Are you compensating the smaller jet changes with corresponding increases in the power valve or just letting it go lean?

Big Dave


I'm not doing anything to the power valves... Why would it go lean??
I monitor the Air Fuel ratio during the entire pass and it's consistently within .2 - .3.. It never turns lean, even after stepping down 2 jet sizes on primary and secondary jets. I might eliminate the power valves completely at one point. I really don't need them for racing. I'm also playing with the thought of going with a Dominator 1050 carb... Will see...
Back to top
View user's profile Send private message
GrandSportC3
Moderator


Joined: 11 Jul 2003
Posts: 1231
Location: Lakeland, FL
32443.62 points


1968 Chevrolet Corvette

PostPosted: Mon Jun 19, 2006 9:08 pm    Post subject: Reply with quote

Just did the calculation for the corrected ET (sea level) of my 2nd pass:

Density Altitude 3200 (feet)
Uncorrected ET 10.95 (sec)
Uncorrected MPH 122.49 (mph)

--------------------------------------------------------------------------------

Corrected ET 10.527
Corrected MPH 127.5
Back to top
View user's profile Send private message
cutlass389
Member


Joined: 29 Apr 2006
Posts: 268
Location: NC
8544.62 points


1978 Oldsmobile Cutlass

PostPosted: Tue Jun 20, 2006 7:25 am    Post subject: Reply with quote

Those are awesome numbers with conditions like that. I can only dream of such things.
_________________
"It may be ugly, but it's SLOW"
Back to top
View user's profile Send private message
GrandSportC3
Moderator


Joined: 11 Jul 2003
Posts: 1231
Location: Lakeland, FL
32443.62 points


1968 Chevrolet Corvette

PostPosted: Tue Jun 20, 2006 8:46 am    Post subject: Reply with quote

cutlass389 wrote:
Those are awesome numbers with conditions like that. I can only dream of such things.

I worked my way down to those numbers over the years...

My first pass ever with that car (with the old 383) was 12.49 @ 113 mph on street tires...
Within a year, I got the car to run mid 11's (best was 11.67 @ 119.79 mph with the 383 and my Tremec TKO 5-speed).
With the 406 and some more upgrades, I went a best 11.05 last year in a DA that was less than 1000. After the rebuild (after one season of racing), we jacked up the compression from 11.6:1 to 12.8:1 and now the car is running 10.90's with DA's in the 3000 range and it should run mid 10's with sub 1000 DA's... We don't see too many days with DA's below 1000 here in Florida... Sad
I'm planning a trip in October or November to Englishtown to race there on a Sunday.. Maybe there would be even negative DA's and mid to low 10's could be possible.. My goal right now is to get the car to run 10.70's in DA's of 3000 or higher. My next mod will be a lightweight battery (- 20 lbs) and Aerospace Components front brake kit (- 45 lbs of rotating mass)
The front brake kit alone usually gets racers well over one tentsh off their ET's, so I think that 10.70's are possible in hot weather and low 10's should be possible in fall if I'm racing up north.. Low 10's would be awsome for a naturally aspirated small block powered Vette...
Back to top
View user's profile Send private message
cutlass389
Member


Joined: 29 Apr 2006
Posts: 268
Location: NC
8544.62 points


1978 Oldsmobile Cutlass

PostPosted: Tue Jun 20, 2006 6:36 pm    Post subject: Reply with quote

That's true, numbers like that don't just happen right out of the box. I was stuck in the 9's (1/8mi) for a year and a half but now routinely turn low 8's. I guess what I meant about dreaming is that my "end" goal is very low 12's (1/4mi) NA to stay out of rollbar range. With limited resources, (no trailer or truck) I dream realistically.
_________________
"It may be ugly, but it's SLOW"
Back to top
View user's profile Send private message
GrandSportC3
Moderator


Joined: 11 Jul 2003
Posts: 1231
Location: Lakeland, FL
32443.62 points


1968 Chevrolet Corvette

PostPosted: Tue Jun 20, 2006 8:00 pm    Post subject: Reply with quote

cutlass389 wrote:
That's true, numbers like that don't just happen right out of the box. I was stuck in the 9's (1/8mi) for a year and a half but now routinely turn low 8's. I guess what I meant about dreaming is that my "end" goal is very low 12's (1/4mi) NA to stay out of rollbar range. With limited resources, (no trailer or truck) I dream realistically.


Racing was a lot cheaper for me when I drove to the track, raced, and then drove back home.. I did this even when the car was running mid 11's... Only got the trailer when I switched to the 406 and race gas..
Back to top
View user's profile Send private message
cutlass389
Member


Joined: 29 Apr 2006
Posts: 268
Location: NC
8544.62 points


1978 Oldsmobile Cutlass

PostPosted: Tue Jun 20, 2006 8:41 pm    Post subject: Reply with quote

With gas like it is, I'm glad/ashamed to be able to race on 87 octane. Obviously not a max effort, but my chart says it's best of 7.97 is roughly 12.5 while the more typical 8.15 is approx. 12.7.
_________________
"It may be ugly, but it's SLOW"
Back to top
View user's profile Send private message
GrandSportC3
Moderator


Joined: 11 Jul 2003
Posts: 1231
Location: Lakeland, FL
32443.62 points


1968 Chevrolet Corvette

PostPosted: Wed Jun 21, 2006 11:27 am    Post subject: Reply with quote

cutlass389 wrote:
With gas like it is, I'm glad/ashamed to be able to race on 87 octane. Obviously not a max effort, but my chart says it's best of 7.97 is roughly 12.5 while the more typical 8.15 is approx. 12.7.


That's pretty good on 87 octane!! Cool
Back to top
View user's profile Send private message
cutlass389
Member


Joined: 29 Apr 2006
Posts: 268
Location: NC
8544.62 points


1978 Oldsmobile Cutlass

PostPosted: Thu Jun 22, 2006 10:04 pm    Post subject: Reply with quote

Pulls 15" at idle(700 rpm in drive) and has EGR, cats, and charcoal canister to boot.
_________________
"It may be ugly, but it's SLOW"
Back to top
View user's profile Send private message
GrandSportC3
Moderator


Joined: 11 Jul 2003
Posts: 1231
Location: Lakeland, FL
32443.62 points


1968 Chevrolet Corvette

PostPosted: Fri Jun 23, 2006 6:37 am    Post subject: Reply with quote

cutlass389 wrote:
Pulls 15" at idle(700 rpm in drive) and has EGR, cats, and charcoal canister to boot.


what's does the car weight?
Back to top
View user's profile Send private message
cutlass389
Member


Joined: 29 Apr 2006
Posts: 268
Location: NC
8544.62 points


1978 Oldsmobile Cutlass

PostPosted: Fri Jun 23, 2006 8:17 am    Post subject: Reply with quote

I just did it and if the scale is accurate, it weighed 3100 with an almost a full tank. Therefore I'm guessing 3000 dry w/out me.
_________________
"It may be ugly, but it's SLOW"
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    SMOKEmUP.com Forum Index -> Drag Racing All times are GMT - 5 Hours
Goto page 1, 2, 3  Next
Page 1 of 3

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
Home | Contact Us | Automath | Cam Files | Dyno Search | Forum | Garage | Picture Gallery | Reaction Timer

Copyright 1997-2018 SMOKEmUP.com All rights reserved.
Advertising Info     Disclaimer     Privacy Policy