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View Full Version : Lunching then bogging, (Drag Strip)



JACTcoupe
08-02-2009, 01:16 PM
OK so I want down to the strip and Every time I lunch it pulls real hard then nose dives. The RPM drop then run back up. ITs a stock 5speed car. Is this normal? If i ride the clutch a lil it doesn't do it as bad. It does have a duel Friction clutch. And I was run slicks, it does it to with street tires. And the fastest I have run is a 9.95 in the 1/8th. And that was with slicks.

Young-SC-Owner
08-02-2009, 02:07 PM
Heatsoak is what id say

Ira R.
08-02-2009, 05:31 PM
When the car bogs down after a shift it generally means you let the rpm's fall off too far when you made the shift. You need to keep the rpm's up between shifts in order to maximize the engine's ability to remain in the power band. By slipping the clutch you were allowing the rpm's to comeback up again before fully engaging the clutch, so essentially you kept the rpm up during the shift. Just still not enough.

You don't say what rpm you are shifting at and you don't say what rpm the car was at when it bogged down but I bet it was pretty low. Even during normal driving shifting into second and letting the rpm drop to say 1200 rpm will make the car bog down.

In other words you need to shift quicker ;)

Ira

JACTcoupe
08-02-2009, 08:32 PM
I dont have the problem when I shift. When I shift 2nd I would bark the tires(even the slick). Its when Im coming off the line. I could rev like 3-4000RPM,and even higher and let the clutch out and it would pull very hard then the car just nose dives. RPM Drop low like I did shift to early. then it runs back up. But if I came out the hole, and road the clutch just a bit. Keeping some of the load off the motor. It would still do it but not no where near as bad...

Ira R.
08-02-2009, 11:04 PM
I dont have the problem when I shift. When I shift 2nd I would bark the tires(even the slick). Its when Im coming off the line. I could rev like 3-4000RPM,and even higher and let the clutch out and it would pull very hard then the car just nose dives. RPM Drop low like I did shift to early. then it runs back up. But if I came out the hole, and road the clutch just a bit. Keeping some of the load off the motor. It would still do it but not no where near as bad...

Breaking the tires loose in 2nd doesn't have anything to do with this. If you come off the line and the nose just dies that almost sounds as if you are hitting the rev limiter. What rpm are you at when it happens. Riding the clutch off the line just makes the engine take a little extra time to reach the same rpms then if you dumped the clutch so it may seem that it isn't happening as badly.

Ira

XR7 Dave
08-02-2009, 11:17 PM
You are going to have to slip the clutch a little to get it off the line without bogging. It's a bit of a delicate step trying to get it right. If you get it right the car will be significantly quicker, but its a hard thing to do consistently.

JACTcoupe
08-03-2009, 12:42 AM
Breaking the tires loose in 2nd doesn't have anything to do with this. If you come off the line and the nose just dies that almost sounds as if you are hitting the rev limiter. What rpm are you at when it happens. Riding the clutch off the line just makes the engine take a little extra time to reach the same rpms then if you dumped the clutch so it may seem that it isn't happening as badly.

Ira
NO it doesn't not hit the rev limiter. Ok lest say there is a wagon with 200pounds in it, and your on a bike. the bike is tide to the wagon with like a 3-4ft rope. Your as close to the wagon as possible. THen you take off as fast as you can. The Rope tightens and suddenly you have 200lb of dead weight your trying to move. You slow down and then you slowly speed back up. Thats how my car feels. Now I pretty much just answered my own question. But I thank that best describes what going on.





You are going to have to slip the clutch a little to get it off the line without bogging. It's a bit of a delicate step trying to get it right. If you get it right the car will be significantly quicker, but its a hard thing to do consistently.

OK so this is normal? I was thanking that. but was not sure. I am very new to drag racing and saturday was only my 3rd time at the track. And this bogging feeling was killing my times. And I have never had this happen on the street.

Thank for the help you guys. I guess this was kinda a newbe question!

neverfastenough
08-03-2009, 01:12 AM
heres a couple 13/12 sec sc's both 5spds. If you listen to the launch they both bog a bit. Its tricky not to, im still trying to find that happy spot and slipping the clutch right. Lots of practice.

http://videos.streetfire.net/video/Thunderbird-SC_644025.htm

Mike8675309
08-03-2009, 01:03 PM
OK so this is normal? I was thanking that. but was not sure. I am very new to drag racing and saturday was only my 3rd time at the track. And this bogging feeling was killing my times. And I have never had this happen on the street.

Thank for the help you guys. I guess this was kinda a newbe question!


On the street your tires spin, on the track they stick. The bogging is from the RPM change as the tires hook vs the inertia of trying to move the heavy car when you released the clutch. An auto has a torque converter that slips, the manual ties the tires directly to the crankshaft of the engine. Getting a clean launch, and not wrecking your clutch in the process is what makes drag racing a 5 speed more challenging.

BlackbirdSc94
06-01-2010, 04:06 PM
Ok so under normal driving conditions on the street, what rpms and how should you launch to not damage the clutch. Also if im trying to aviod wheel hop is there a certian rpm for that.

My speedos broken too so does anyone know what rpm is 35 45 and 50 mph in the gear they pull hardest and the "overdrive gear"

Is it normal to get on the gas at 1200 to 1500 rpms and feel a slight shudder in the steering pedal and shift nob, just had my clutch serviced and the motor and trans mounts done and Im wondering if its related to that or is this just something that these cars do since I bought the car with those problems. Only thing is I dont recall it doing that before I had the car worked on even needing new mounts

You guys are gonna start calling me the revival king if I keep finding these old threads

Mike8675309
06-02-2010, 10:00 AM
Start a new thread about your shudder. it's not normal.

to avoid wheel hop, don't spin your tires. if the tires don't spin, they won't hop.

when driving on the street you don't usually call it launching. Thus you use whatever RPM and clutch position is necessary to move the vehicle from a stop.

Whenever my speedo has not worked I pretty much just go and drive the car down a road with other people and pace them. Then I call that the RPM. You can try this calculator if you want: http://golenengineservice.com/calc/calcrpm.htm

old_coot
06-02-2010, 10:26 AM
Learning to drag race is learning what compromises to make in order to get the best time slip----letting air out of the slicks usually ends up gettting a better 60 foot time but slows the car on the big end....pumping the slicks up allows them to spin more at the line slowing the 60 foot time down but allows them to roll easier on the big end so you mile-per-hour better and make up time on the big end....you need to play with air pressure so you get a decent launch but allow it to spin enough to minimize the bog.....this is what makes racing fun.........................Dan

BlackbirdSc94
06-03-2010, 02:02 PM
oh and will not pushing the pedal to the floor damage the clutch, cause itll shift after like a inch or two of travel. I usually go half way down though

David Neibert
06-03-2010, 02:22 PM
oh and will not pushing the pedal to the floor damage the clutch, cause itll shift after like a inch or two of travel. I usually go half way down though

No it won't hurt it. BTW, what's a "steering pedal" ?

David

old_coot
06-03-2010, 02:40 PM
No it won't hurt it. BTW, what's a "steering pedal" ?

David

I'm just guessing, but I think there is a comma missing between those words.....Dan

David Neibert
06-03-2010, 02:59 PM
I'm just guessing, but I think there is a comma missing between those words.....Dan

Dan,

I thought it might be drifting lingo for gas pedal, but the missing comma makes more sense.

David

BlackbirdSc94
06-07-2010, 02:56 PM
Dan,

I thought it might be drifting lingo for gas pedal, but the missing comma makes more sense.

David

definitly missing th comma, I think its a engine issue, its become a sometimes thing and when the car dosnt do it she pulls hella hard, its like you go the flu and your chest is congested, then you cough and breathings a bit easier. Its like the car just goes easier when its not shuddering and the shudder only happens inbetween 1500 and 2000 rpms under gas but the dash shakes the shift knob shakes so does the steering wheel and I feel it in the pedal too

Ira R.
06-07-2010, 04:18 PM
definitly missing th comma, I think its a engine issue, its become a sometimes thing and when the car dosnt do it she pulls hella hard, its like you go the flu and your chest is congested, then you cough and breathings a bit easier. Its like the car just goes easier when its not shuddering and the shudder only happens inbetween 1500 and 2000 rpms under gas but the dash shakes the shift knob shakes so does the steering wheel and I feel it in the pedal too

That almost sound like your in too high a gear for the rpms. Is this happeneing only in 1st when you first start out? Andis it happening regardless of how hard or soft you release the clutch?

Ira

.

BlackbirdSc94
06-08-2010, 09:29 AM
That almost sound like your in too high a gear for the rpms. Is this happeneing only in 1st when you first start out? Andis it happening regardless of how hard or soft you release the clutch?

Ira

.

sometimes it happens in first too not often though, but in the mornings when its cool and the cars just warmed up a bit she runs great under the same conditions, I can have the car in third doing 25-30 mph. I dont know cause my speedos not working but I pace people. Anyway the car will be at like 1500 rpm and when I ease in on or hit the gas hard she just goes smoothly and stronger.

When its running funny the car will have the shudder and be slightly slower to pick up speed but after you get past 2k she pulls and accelerates smoothly.

Then sometimes itll be running smoothly and Ill go to speed up while doing like 35-45mph and shell take off but then its feels like a sputter but the sputter isnt a bog down but like a small extra burst of power. It only seems to do that after Ive been driving for a while or its real hot out

Dirtyd0g
06-08-2010, 12:25 PM
My ranger has a steering pedal. When you get it broke loose more throttle turns harder and less throttle turns less.
Alan