I just installed a 3.5 in 3 out x and no real tuning and went to the track first time run was about .15 slower than a few weeks ago and the weather was a whole lot better.So thinking maybe with the increased scavenging effect it was lean so jetted up 2,well slowed .05 more.So went down three from my initial setting and picked up .07 from the first pass.Eliminations had started so I couldn't adjust anymore.I was curious if anyone else had installed an x and just gone pig rich like that? I am still about a tenth off so I will have to do some more tuning.

Did your old exhaust have a 3.5" exhaust? Could the lost in performance be attributed to the change in exhaust pipe size?

for what its worth. I have a 502, dynomax ceramic coated headers 3" in/out dr. gas x pipe and 3" blowmaster mufflers. And am extremely pleased with it and I'm going to try different mufflers next year.

Your car sounds pretty impressive from the signature

ttt

you didn't say what you had before you made the change. No exhaust at all? Dumps? What size? etc.

I have heard that the X will "over scavange" the engine. You'll get a harder "pull" and really suck the mixture through. No hard numbers to prove this as I've only seen an X on 1 vehicle and we didn't really tune it the way it should have been.

Jeff

Before heresay settles into anybodys thoughts on the X-pipe remember that it is very successfully used in NASCAR/superspeedway cars. Like anything else a usually teriffic performance mod can be done all wrong. At this point we have no idea of the exact configuration of Pat's original exhaust, or if his weather station showed the same conditions as on previous passes.

Thomas

Previously was straight 3.5 into ultra flows dumping at the axle.I don't believe it has really been a big performance killer,rather, I just found it odd that it had such an effect on my air/fuel mixture.It is just very rich,like I stated eliminations had begun and didn't have time for further tuning.The weather was much cooler and less humid than anything we have had all year.My original intention was to jet up for the weather change,when I did it slowed more.I started 88 square went to 90 square as I usually do in comparable weather.I then went 86 square and picked up .15 and was still over a tenth off of where I should be.Barring an air bleed problem,I don't think it should be a problem to get it to run where it should.I don't have an egt probe or air/fuel meter so I just jet for mph.Maybe it was always rich and just ran best that way.I will not abondon it regardless,I find it to be rather unique sounding and incredibly smooth.Perhaps a chassis dyno is in the future,I have always been curious to see what it puts down to the wheels and get some tuning done as well,try some other plugs,timing, maybe another carb.

Please keep us posted as to what you find out. If you ever get to the chassis dyno, they will have a wideband O2 sensor. You will see exactly what the A/F ratio is doing. If your starting a pool for the HP numbers, put me down for 620RWHP.

Andrew

Well, as it happens I am heading to the dyno this afternoon,$75 for 3 pulls.Curiosity has got the best of me,I need to know what is going on,and for the price I can't beat it.Results soon to come.

I found my combination to be lean once the X was installed. If memory serves, I had to jet up 3 sizes in the front and 2 sizes out back.

Well, back from the chassis dyno,bad news I suppose,my air/fuel mixture was dead on 13:1from idle to 7k,so I guess that the 3" on the back side of the x is just too small and hurting flow.If anyone is curious 536.7 hp@ 6700 and 537.8ft/lbs @4600 at 40* timing at 38* lost 30+ hp and torque,went to 42* and was 528.8 hp and 566.8 ft/lbs.Now who want's to buy my exhaust???
I will put the old back on and try to sell this one and move up to the 3.5 x 3.5 graemlins/angry.gif

Pat,
Thanks for the heads up! graemlins/thumbsup.gif
I'm making a mental note of your findings.

Did you account for air/track conditions for before & after runs? That could easily make up a large part of the performance difference assuming the air/density altitude was worse.

I would not change the exhaust before doing some more on track runs.

Actually yes the runs with the x were with 1500 ft better of altitude.Last time out with straight pipes 6.50 @ 103 with da of 2700 ft. This weekend with x best was 6.54 @ 101.5 with a da of 1100 ft.I am not saying it doesn't work, rather I am undersized.I will stick with it until I can come up with the cash to do it again,or sell this one.Likely with Christmas coming it will be a while.Next chance I have for a tnt I will try to do some back to back tests.

Pat, first of all, congrats on some VERY impressive RWHP #'s. Those are some stellar numbers. I'm curious why you didn't uncork the exhaust on the dyno? Seems like that would have shown rather quickly of the new exhaust system was restricting flow. Do you intend to leave the timing at 42 degrees? Remind me what single plane intake you're running? I wish I could offer some advice on the x-pipe here, but I have neither an x or h pipe on mine. 3.5" collectors into 3" reducers into Straightline Performance mufflers and 3" Torque Tech tail pipes.

Again, congrats graemlins/thumbsup.gif

Ken, like a dork I put it on to where it just about has to be on a lift to get it off,if I could get it off without much effort I would have.The intake is a team g dominator intake with a 4150 adapter on it.I tried several intakes over the years and this one just worked the best.Most people don't speak to highly of it.the next best was a vic jr slower by about .08,performer rpm was .15 slower.I would like to test the dart oneday but they are big money and I don't know anyone who has one to let me play with.I think I will try it at 42 deg. I think the 9 hp loss would be well worth the 30 ft/lb gain.I think the canfields are capable of making a little torque :D All in all I really like the exhaust,just not to happy with the loss.

Ok, back to back with new exhaust 10.73,10.74.Put old stuff back on 10.32 8 consecutive rounds.

OUCH!!!! :confused:

OUCH!!!!
Agreed!! Ken, I tried the 42* thing as well,no difference so I put it back,no sense running that much lead for no gain.

Thats 40 total right Pat???......