Went to the track (BOP) saturday

[Ttype83]

Have alot of fun and saw some very clean/nice cars. GS/2 GNX's, a old 68 or 69 Fastback mustang, tempts...A ton of GN's.

I got 4 runs in, could have done more but was having problems so didn't want to press my luck. Left on 0 boost, with 7 psi max at 3/4 throttle.

1 2 3 4
R/T 1.340 1.450 1.340 1.307
60' 2.581 2.418 2.479 2.612
330 7.212 6.956 7.001 7.534
1/8 11.239 10.765 10.890 11.481
MPH 59.54 66.26 63.54 63.02
1000 14.856 14.042 14.268 14.820
1/4 17.847 16.849 17.129 17.634
MPH 75.01 80.18 78.71 80.19


As you can see from my R/T I'm a consent slow
I was able to hit stock times on my 2nd run with only 3/4 Throttle.
On every run the car fell on it's face, mostly when I tried to push it passed 3/4 throttle and 7 psi. On the last run I put the cold air kit on and it fell on it's face right at lauch and with only 5 psi. It wasn't able to push passed 5 psi untill after the 1000' mark as you can see by my ending MPH (same as my best time) I was the only carbedhotair slug there ....I parked my car at the end of a row of GN/Ttype's...Man I thought I got a pic of that
Still had a great time
Jim

 

[pat83t]

Man you need to cut some better lights. . Those e.t.'s are about what I was running when I went down. Since then I found what was slowing me down alot. My cat. was clogged. Pretty clean now though. You could pass a golf ball through there. Now just some fine tuning and I should be killing those times. It was pretty clogged up.

 

[fc227]

Did you adjust the secondary so they open more than stock? I ran into the problem you described because I had Too much carb.

 

[Ttype83]

Originally posted by fc227
Did you adjust the secondary so they open more than stock? I ran into the problem you described because I had Too much carb.

Yes fred it was like that, but I adjusted back before I went to the track. I tried readjusting to open more on the last run and it fell flat on it's face off the line. Still VERY happy, all runs with out opening it up. I should beable to hit the 14's once I get this stumble worked out. I think it's weak spark, I have a good coil but have not changed the module. How knows how old it is and would give me weak spark under load. It would be a bad idea to change the 02 sensor out either, it's been in for almost two years now...oppps.

Hey pat, ya I'm slow....I was to busy looking around at all the car, trying to stage, build boost all at the same time and couldn't keep my mind on the tree. Kind of like deer fever. Spending 23 years off of the track is to long of a time.

 

[pat83t]

Yeah I know what you are talking about. When I went to woodburn I think I did more drooling there than I do at most car shows. Our e.t.'s, 60', 1/8th mile, and 1000's are all about the same but my r/t's were like .6's and .7's. We are pretty evenly matched for cars, you should come back up here next summer for Turbo Thunder IV. Then I won't be getting beat so bad. I just waved as the I/C cars went by.

 

[b4black]

I'm glad you had a great time!!! You never know where your car really stands until you run at a drag strip. Your times look just like my first time out.

Stumble eh? Well we certainly have something in common. Winter's coming here, so I'm probably done for awhile. Maybe you can figure it out down there where it's warm, so I'll be ready come spring.


You should watch your oxygen sensor with a digital multimeter. It's easy. Just unhook the O2 sensor connection, and reconnect it with a end of 18-ish gauge wire pinched inside. Then run this to the passenger compartment and hook the DMM to it and any ground. Watch the output in real time. You'll be able to tell if the sensor's bad or if you see the erractic reading's like I do at WOT. A ~$20 DMM from radio shack is better than all those expensive Air/Fuel gauges.

What plugs/gap did you go with?

I was really leaning toward weak spark, but now that the new coil did nothing, I'm thinking along the lines of what Fred just said. Time to learn more about the ol' Qjet.

Did it launch hard? Would it spin with more than 0 psi? Those aren't bad 60's, but that's an easy place to make up time.


THE MORE GUYS/CARS WE HAVE AT THE TRACK, THE MORE WE CAN HELP EACH OTHER OUT!!

 

[Ttype83]

Re: Re: Went to the track (BOP) saturday

Originally posted by b4black
Stumble eh? Well we certainly have something in common. Winter's coming here, so I'm probably done for awhile. Maybe you can figure it out down there where it's warm, so I'll be ready come spring.

Well it's already to cold now for the cold air kit, I'll work on it .


What plugs/gap did you go with?

Autolite 666 gaped @ .45 I have AC 43's to go in, almost installed them before.

I was really leaning toward weak spark, but now that the new coil did nothing, I'm thinking along the lines of what Fred just said. Time to learn more about the ol' Qjet.

It still could be, when was the module changed? And I think Fred is right too. More like a combination of the two.

Did it launch hard? Would it spin with more than 0 psi? Those aren't bad 60's, but that's an easy place to make up time.

Yes it launch nice on the first three, I could have pushed it to 3 psi launch I think on my stock 14" tires. On my second run I launched with 0 psi but pushed for 7 psi when let it run at 5 psi for the the second half.


THE MORE GUYS/CARS WE HAVE AT THE TRACK, THE MORE WE CAN HELP EACH OTHER OUT!! [/B]

Yes, that's for sure It easy to figure out what is going on when you have more running at the track.

Pat with your RT's you toast me But it would be nice to run with another carbed car. Heard of a guy that's running a 8.?? 1/8 mile north of me. I think that's were I'm going to try to do more runs at.
Jim

 

[Turbo-Rich]

GO JIM

Glad you had a good time man!
You will be in the 14's before ya know it.
Specially if you can use that 3#'s at launch &
not fall flat like ya were.
Were you using any traction devices?
What was your timing set at?
Anyway, I'm sure glad I own a G-tech.
Going to the track with a blind tune up & trying to dial your car in in 3 or 4 runs is a real PITA.

 

[fc227]

IMO, I would still try closing that carb a little more. My car bucked stumbled at WOT but ran great at 3/4 throttle. When I had Too Much carb. It even did it do me with the Holley carb on the car. Thats way I had to limit the secondarys on the 780 Holley to only open about half way. Just my opinion, but it sounds like what happening to you is the same that happened to me. There could be other causes, But since that was adjusted I would double-check that first. IMO.

 

[b4black]

Jim, you mentioned you bent the the seconary air valve stop tab out of the way and then put it back. Did you ever adjust the air valves spring tension so they open easier?

What Fred is saying is making sense to me. These carbs are rated at a max CFM of 750. If they were used on big blocks, then they must be made smaller to work on little ol' V6's. The stop tab and sring tension is how they do it (I think).

Maybe more spring tension or shimming the stop will work.


From "Turbochargers"
In gerneral, a high-output turbocharged engine requires the same or even less carburetor capacity than a high-output NA engine. For example, a NA '71 Olds 350 used a 725 CFM Qjet. When Rajay turbocharged the car, the got best results with a single Holley 600 cfm four barrel"

From "Rochester Carburetors"
CFM = CID X Max RPM X volumetric efficiency / 3456
= 231 X 5000(?) X 80% / 3456
= ~270 CFM

When the air vlaves open 100% (90°) the CFM is 750.
When the air vlaves open 50% (45°) the CFM is 590.

 

[Ttype83]

T-Rich, Thanks Dude...wish you and the family could have made it too. Larger tires have been moved up on the want list Wife even wants them.

Fred, Yes that is the first think that I will look at when I get back home (in Charleston,SC untill tomorrow night) Laptops are great.

Rich, Yes that was one of the first mods that I did last year. It almost has no tenstion on it....Met to chage it back when I pull the airhorn off 2 weeks ago and forgot That's the second thing I will fix) Those 2 things have been on my mind since. I bent the tab back on the last run and that's when it boged off the line.
But at the 1000' mark I pushed it harder again and the 4 barrel opened up and it started to pull hard again..hess the same MPH at the end.

Jim

 

[hot79sport]

Question, Pat83T

you said your cat was plugged, did it slowly accumulate, or did it clog rapidly?

 

[unboostedV6]

Rich, that formula for required carb cfm works great for N/A cars, but that 80% VE come up a little short when a turbo is in the picture...Just for giggles - an intercooled '86-87 car at 15 psi, assuming the air charge comes down to ambient temperature(not!), would have a VE of 200% and need a carb capable of flowing ~670 cfm at 5000 rpm. GB

 

[unboostedV6]

Additionally, the turbo will create a much larger pressure drop across the carb, whether it's blow thru or draw thru, than the 4 barrel flow standard of 28 in H2O. This will tend to reduce the rated CFM requirement. GB

 

[pat83t]

Re: Question, Pat83T

Originally posted by hot79sport
you said your cat was plugged, did it slowly accumulate, or did it clog rapidly?

Actually my old turbo seal gave up about a year and a half ago and everytime the turbo would spool it would throw oil out the tailpipe. That is what clogged my cat so fast. I replaced the turbo then but not the converter so it just clogged more and more. Can't clog now though. Not unless you can clog a 3" hole.
It was the original from 83 though so who knows what kinda shape it was in.

 

[b4black]

Originally posted by unboostedV6
Rich, that formula for required carb cfm works great for N/A cars, but that 80% VE come up a little short when a turbo is in the picture...Just for giggles - an intercooled '86-87 car at 15 psi, assuming the air charge comes down to ambient temperature(not!), would have a VE of 200% and need a carb capable of flowing ~670 cfm at 5000 rpm. GB

Additionally, the turbo will create a much larger pressure drop across the carb, whether it's blow thru or draw thru, than the 4 barrel flow standard of 28 in H2O. This will tend to reduce the rated CFM requirement. GB

I knew the 200% VE thing, and always assumed a turbo car would need a bigger carb, so I was surprised to read in "Tubrochargers" that a turbo needs the same or less CFM than a NA engine. Your second statement explains why (thanks Greg!). I wonder if I could see this pressure drop by tapping a vacuum gauge between the carb and turbo?

I tried something to confirm what Fred said about too much carb. I bent the tab out of the way to let the secondary air valves open more. Stumble got worse. Now I know my problem, thanks Fred!


A bit of irony between what I always heard about the carb being the weak spot on our turbo cars because they can't be made big enough or rich enough. This year I found out my carb is TOO big and TOO rich.

 

[pat83t]

Hey Rich, didn't you say you were looking for a 4.1L?? http://www.turbobuick.com/forums/showthread.php?s=&threadid=62744
If not just ignore me for my stupidity. Not sure how close to Ohio you are.

 

[b4black]

Thanks for the link.

Well it says it can be driven, but 6+ hours may be a little long for a $150 car. I really would like to find a 4.1 car to use as a winter beater and then pull the motor in the spring.

 

[pat83t]

Sorry didn't realize it was that far away. I will keep looking.