Heading to test and tune this evening and I made a change that I haven't tried before. I thought it might be fun to take guesses.

68 Barracuda 3550lbs best ET with the current combo is 10.44@126.41 done a couple of weeks ago, it actually spun a little bit on that run and had been .02 faster to the 60 that day but this worked out to be the best run of the day.

418" small block W2 10:1 big solid roller. TTI headers with 3.5 collectors through a 3" exhaust system with 3" cutouts open not to far from the collector.

This week I made some 3.5" collector extensions that are 12" long, longer might have been ideal but my driveway sucks and I wasn't sure they would have made it.

So at todays test and tune I will run it full open exhaust with no exhaust system at all. The exhaust system was 60lbs and the air is likely going to be 500ft more than when I ran a few weeks ago.

Just for fun, what do you think the results will be? It sounds soooo much better than it does with the exhaust dumps open, and I am also sure my neighbors will appreciate the exhaust system more now.

I have seen Freiburger comment that 3.5 exhaust always does better than 3" anytime he has tested it.

I would love to see a 10.2 anything but I fell that may be optimistic. This is of course accounting for the weight loss of the exhaust in that gain.

Also, this combo will remain unchanged at least through this year so I am trying easy and low dollar things that might help just for fun. I think next is E85, it will be an easy test since the car is EFI and setup for flex fuel already, it will be just drain fill, and keyboard work.

I'm going with 10.33. Mufflers vs. no exhaust would be more dramatic for sure but since you were already running it with the cutouts open I don't think the change will be that dramatic. Good luck tonight!!!

Best of luck with it...I am sure you will make improvemnets. Ill be blowing through there sometime in the early morning tomorrow on the way to Columbia MO then back later Saturday. Hope the weather aint crappy but looks like I am bringing the cold with me from out here in the frigid west coast.

So, the new cam is showing promise after all??

After I restricted the oil to the rockers I went back to thinner oil and a lower oil level like I would have run with the old cam. It appears to have responded well to that and has been very close to the old cams performance. It might have even run better had I packaged the best 60ft of the day with the best ET but you know how that goes. It at least shows enough promise that I don't want to take it out lol.

Thanks, it sounds way nastier than a 10:1 91 octane combo should so I am pumping my numbers up based on that alone lol.

I would appreciate it if you could come through this afternoon with some cooler air for test and tune. Safe travels!

Well in anticipation of Al bringing in the cold front we are under a wind advisory. The conditions will be crap and it would be smart if they make us run 1/8th mile. I don't mind bracket racing 1/8th mile but I prefer 1/4 mile for test and tune. With the weather looking much better next Friday we are going to call it off and try then.

I don't envy Al having to tow through this wind!

It is really windy, lights are flashing from time to time as power lines smack together.

Be careful Al!

10.35, I'll bet the exhaust benefit will be weight only. I'm not acounting for weather as it's an unknown.
Doug

My dad keeps a log of all my runs with weather conditions, when it gets closer to next weeks TNT I will update with ETs from similar weather.

I know we're a ways off but your Friday weather forecast looks to be stellar right now!

My old pump gas Duster (517 C.I. BB) ran 7.01 in the 1/8 mile with the three inch complete exhaust system hooked up with the old style Magnaflow 14x7x3.0 muffs mounted behind the rear end dumping at the rear bumper. I remove that system and with identical weather and density altitude at the same time the next morning it ran 6.98 in the 1/8 mile with .2 MPH faster I think the weight loss was the reason for that gain.
I have seen dramatic improvements at the track in the 1/4 mile by removing a 2 1/2 inch exhaust system with a set of the old Thrush Corvair turbo muffs with the 2.5-inch tail pipes exiting in front of the rear tires with no other changes. That car was a stock stroke 440 bracket motor making maybe 500 HP, it ran a best of 12.23 at 109.6 MPH with that system on the car, it ran 11.39 at 117.6 MPH with it removed That surprised the heck out of me, I was sure it hadn't ran that much faster until I ran it again in the other lane 45 minutes later and it ran 11.41 at 117.7 MPH, that was at the old L.A.C.R track in Palmdale, CA back in the mid 1990s. The left side of that track was right at .03 ET slower, different, than the right side

After tweeking the jetting, I'd guess it will show almost .1 quicker!

The car is fuel injected so the jetting is automatic lol. It can just as much as 5% on its own if needed during a run.

An automatic, and Fuel Injection. Might as well put A/C, and cruise control in it. LOL!

I can deal with the heat just fine but I wouldn't mind some cruise control on drag week lol.

I guess you can hang your feet our the window while going down the road...

I picked up a solid 0.2 going from 3" to the bumper to 3.5" x-pipe dumping at the axle. I'm going to be optimistic and say 10.29 because I'm rooting for your 10.2x

I am jealous...we just had or tracks open this weekend...with ice in the burnout box...

Weather is looking good, good chanced we will have a really good match for the weather from my earlier trip this year.

I am hoping the lanes run smooth tonight. I have a half tank of the finest 91 octane and we are trailering the car so If the lanes stay pretty clear I will wear this thing out if I find progress in engine or chassis tuning.

Nothing to add, except for wishing you and your Dad have a great time. 👍

Thank you sir.

Good luck! If I were a bit closer I'd come watch.

Good luck!!!

Well I guess I brought bad juju on myself making this post. It has been a very long time and hundreds of passes since my car hasn't run right and tonight I broke the record. Never got one good pass in.

Every single thing we can check checks out but it is falling on its face right when the G-force would probably be peak. It falls on its face sputters a little then takes off. Went a best of 10.96@126.85 with a 1.84 60ft. Shook everything we could down at the track but this wouldn't go away. The 02 sensor was also acting up but we disabled its ability to make any changes and the problem still persisted. The 02 sensor was old so it might have just been its time.

Open collectors vs having any kind of exhaust on the car did do some things I wouldn't thought of. I had to make some pretty drastic changes to the idle control valve. It didn't need near as much air valve open to idle at the target RPM.

To make sure it wasn't a lean bog I added a good amount of fuel both to the map and to the "accelerator pump" and it didn't really change anything, maybe made it worse.

The problem can't be duplicated on the return road so I think something is loose somewhere. I built this EFI controller my self so maybe it has cracked a solder joint or something after 8 years of trouble free performance. The best air I saw was around 800ft and I bet we won't see that again until the fall.

I'll get a new 02 sensor and put the exhaust system back on and see if I can shake this problem down then maybe try again.

That’s a frustrating trip to the track, ugh. At least it came home in one piece!

Do you measure/log fuel pressure?

Yes, I have had some trouble with the SD card so I was using my laptop to log. It takes a slower sample rate but it logs everything. Fuel pressure it rock steady, same for battery voltage, those were the first two things I checked.

Looking over logs this morning I do see it had a sync loss like it missed one tooth right when this event happened. However, its only in one log, the other logs are clean. I also logged a tooth counter on the last run. I have that posted over on the megasquirt forum because I get lost in that stuff. Caveman understand air fuel, caveman understand horsepower, caveman get lost in data not related to those things lol.

Little update on this. I finally made it back to the track last weekend. The only thing I changed was that I put the exhaust system back on the car. The car ran perfect and the data logs never missed a meat. It even ran a little faster than last time I had it in crappy July air.

My conclusion is that the open exhaust was scrambling the guts on my home built EFI system. I relocated it to the bottom of the dash for better access and a friendlier environment. I plan to try the collector extensions again before we make the haul to drag week.

Another thing I have learned is that the exhaust dumps don't matter(not a big surprise) near as much since I removed the tailpipes from the car. Even running without the dumps the car was .03 faster than last time it was out in similar air where the exhaust dumps were open.