Looking for some help figuring out what’s going on with my wife’s dragster. The 60’ slowed up a lot and it looks like it’s a horsepower or maybe converter problem. It still has good MPH so I don’t think anything is up with the engine itself but it’s not putting the power to the ground at the beginning of the track. The engine RPM graphs are now drastically different at the hit and I’m trying to figure out why.
Attached are graphs of two runs, one from three weeks ago when things were good and one from today. Time slips are on the picture. The tuneup is the same for both runs. This is a 555 with a Ron’s terminator, 39 nozzles 76 pill. I’ve had this engine in my car for years and using the same tuneup so it should be very close. 4.10 rear gear 1.80 low. Tires have 67 runs on them. One thing I did notice is the graph when the engine is on the two step isn’t as smooth as it was. I don't know details on the converter that's in the car currently as it came with the car and (used to be) very consistent so we've never had it cut open. Not sure if it has a sprag but it was originally made by Coan.
Any thoughts? Click the picture for a larger version.
September 27, 2020, 12:57 PM
Mike Rietow
Ohms test the spark plug wires.
September 27, 2020, 01:24 PM
183N
Thought about plug wires as they are a couple years old (and I’ll ohm them out as soon as it cools off, just got back from a first round win in both cars), but would it run good up top if it had a bad wire?
Incrementals show the slow 60 foot carries over in to the 60-330. 660-1320 mph gain is actually better on the "slow" run which means no plug wires have fallen off. Shift on time, right? ACC is a math channel→Engine RPM/DS RPM? What is the recording rate for RPM (how many data points per second)? What do the plugs look like? Weather conditions show it should have been .007 slower on the "slow" pass. I don't know MFI but LEAN will cause a significant change in power on alcohol without much change on the big end. Maybe call up Ron's and ask if it's possible that your system can go lean under 6000RPM. (convertor helper stuck on?) A WBO2 would really help diagnosing something like this.
September 27, 2020, 02:12 PM
Mike Rietow
Take that # 2 spark plug wire and bend and twist it as your doing the testing... See if the number goes to the moon.
Check a few or all the wires like that.
If the number goes to moon on most or all, when you twist or bend them, the wires are bad.This message has been edited. Last edited by: Mike Rietow,
September 27, 2020, 03:26 PM
183N
quote:
Originally posted by 183N:
quote:
Originally posted by Rick!: Incrementals show the slow 60 foot carries over in to the 60-330. 660-1320 mph gain is actually better on the "slow" run which means no plug wires have fallen off. Shift on time, right? ACC is a math channel→Engine RPM/DS RPM? What is the recording rate for RPM (how many data points per second)? What do the plugs look like? Weather conditions show it should have been .007 slower on the "slow" pass. I don't know MFI but LEAN will cause a significant change in power on alcohol without much change on the big end. Maybe call up Ron's and ask if it's possible that your system can go lean under 6000RPM. (convertor helper stuck on?) A WBO2 would really help diagnosing something like this.
Yes shifting on time. ACC is the g meter not a math channel, RAT is the math channel for DS/RPM. I added that to the graph and posted it below. It doesn't seem to work properly early in the run, if I divide the numbers it doesn't give me the same answer as the math channel does.
Engine RPM was only 100 samples per second - yes I realize that's not much and I just raised it. 4 magnet collar on the DS. Plugs look normal. About 30 or 35 runs on them. Can't hurt to put a new set in for next week but again I'd think I'd see that at the finish line...
We're definitely not lean with this combination. Like I said before I've had this combination in my car for many years. And also earlier this year we did richen it up in her car and it lost MPH so the tune should be pretty close. No converter helper/leanout on her car.
September 27, 2020, 07:50 PM
Rymo
Broken sprag
Ryan Fasano
2014 Byron Overall Track Champion Byron's actual elevation is 730' because that matters more than winning anything ever....
September 27, 2020, 08:05 PM
jenavet
just thinking outloud but we had a dragster,similar problem and it was the fuel filter
September 28, 2020, 11:31 AM
ts393c
quote:
Originally posted by jenavet: just thinking outloud but we had a dragster,similar problem and it was the fuel filter
I had this same problem on my injection years ago too. Fuel filter was stopped up.
September 28, 2020, 12:07 PM
Stickshifter_55
I would like to see the fuel pressure graph...... and check the filter.
quote:
Originally posted by ts393c:
quote:
Originally posted by jenavet: just thinking outloud but we had a dragster,similar problem and it was the fuel filter
I had this same problem on my injection years ago too. Fuel filter was stopped up.
These spark plug wire ohm readings look very good. The longer the wire the larger the ohm reading . The coil must be very close to the distributor, look at the low ohm reading.
Look at the interior of the distributor cap and verify the carbon center ball is present.
Maybe some bad methanol? Or nozzels being slightly restricted? Pump fuel filters ? Barrel valve?
September 28, 2020, 03:40 PM
pentastarrail
Looks fuel related to me. Also looks like the weather got worse on the second run. Maybe a bit on the fat side?
Man was not built to fly ... That's why he built HEMI's
Frank Zeffiro ALIAS -- BIG KAHUNA
September 28, 2020, 05:04 PM
183N
I sent my graph to Justin @ FTI to see if he thought it could be a converter thing. He wrote back "Does this car have a starting line enhancer?"
Pretty sure he nailed it. Looking at the graphs now it looks like it just wasn't wide open, then after it left G force/vibration helped open the blades all the way so it acted the same after that.
The fuel filter was cleaned in June and there was hardly anything in it as is usually the case when I clean them. It's interesting Mike & ts393c having similar problems and it being the filter, I would think that would show up in the mph too.
