Dominic Sorresso

Guys,

Finally got an opportunity to test and tune over at Byron Dragway in Byron, IL. Weather started out rainy but stopped by the time we got to the track. Took several hours for track to dry out and because of that there weren't too many people out. So when it came time to race, we got quite a few runs in. I ran straight street radials at 35 psi. Downside is I didn't time as well as I did with my 7747 last year. 13.37 v 13.54. However, my trap speed increased from 102.1 v 104.75. And since there were fewer people there, the car had little time to cool down, so many of the runs were done with CTS at 212+. One other indicator of higher top end power is that this time, I needed to shift into 4th gear probably somewhere around the 1000' mark. No other way around it. With the 7747, I was going through the traps in 3rd. This is with 3.45 gears and a ZF-6 trans.
Here are the stats for my 105mph run v last year:


EBL 7747
60' 2.208 2.146
1/8 8.847 @ 82.95 8.657 @ 84.09
1/4 13.54 @ 104.75 13.33 @ 102.06

And yeah, I got an EBL datalog that Bob has already discussed with me. Motor was running lean out of the hole annd maybe a bit lean at the top. I'll get that fixed.

DM91RS

Kool...........got an EBL 1/4 mile graph?

Grumpy

The poorer 60', and an additon shift explain the slower ET.
The higher trap speed shows you were in fact making more HP.
A .1 incease in the 60, can show up as a .15-2. in the guarter.

Dominic Sorresso

Bruce/DM,

Here's what the datalog plot looks like. BTW, this shows how damn close RBob's 1/4 mile calc is to the real thing. You can see where its lean out of the hole. Bob also made me aware that if I am using ethanol (10% in IL) I should be shooting for a lower AFR in PE to be safe. Any input you guys want to provide is most appreciated. I am thinking I may have gone with a spark plug 1 heat range too hot. I was using an AC 41-629 and stepped that up to a 41-630. That's equivalent to an Autolite 3924 or NGK FR-5 and going a bit hotter. In any case, I could definitely feel that the motor was running much stronger at the top end than last year. It felt like it was still pulling through the traps. Both Bob and I think there's more left in the motor with the right tune.

Bruce,
Based on your Rule of Thumb, if I was able to get the 60' down to 1.9, I should be able to break into the 12s? Wouldn't be bad for a stock block 350 Xfire.

Grumpy

I'd plot the AFR, vs timing before I considered it as being *too lean*.
I'd also get an EGT guage. When you trying to wring the most out of a combo, you can get into generating just too much heat.

Yep, just as stock as my Black Brick...

Dominic Sorresso

Bruce,

Would you explain further about plotting AFR v SA? What should I be looking for? Most, if not all, of the Knock counts took place while in first gear. Looking at the graph, that's where the lean spots were also. Timing at that point was in the high 20's to low 30s. Bob and I checked the VE table and saw that I had lower VE% at 100kPa and(< 2000rpm) than at the same rpm but lower kPa. These were areas that hardly ever get logged so I never really paid attention to them. Well in my case, this area turns out to be important for that crucial 60' time. I guess I am learning a lesson here about how critical those first few tenths are and how they multiply at the big end of the track.

"Yep, just as stock as my Black Brick... "

elkabong

Congrats...... I hope I have similar success.

Grumpy

A WB by it's self is no gurantee of what the actual AFR is. Remember timing can effect the AFR, as far as a WB goes. If you see *it* being lean when there's alot of timing, then your AFR might be off. It's easy get trapped by WB reading, you still need to make sure lean is in fact lean....
Not to mention in running an EGT if you see temp dips, you might be into trace detonation. Again, a K/S by it's self is no absolute about detonation.

The higher the state of tune, the less forgiving it is.

The flat black car is admittedly not stock....
Just think of it, as a GN but 1,000# lighter.... <G>

Dominic Sorresso

Bruce,

Regarding the effect of timing on AFR, I have seen that several times. A 1d increase in advance made a .5 change in AFR.

liquidh8

great to hear dominic, I took my wagon to atco a few months ago w/ebl and got a 13.6, but @ 98 mph, I obviously have more tuning to do to get the traps up, the 60 ft I think was a 2.2 also, with a noticable bog off the line. Good luck and get that puppy in the 12's. Now, If i get time to fix the n20.....

Dominic Sorresso

liquid,

I took a look at my plugs after racing and found that #8 was running very rich. Black soot. So I have been trying to determine what the cause of that was. At first I thought it was oil fouling, but it was drier than that. Checked compression and that was right there with the other cylinders I checked. Checked plug wire. Ohmd out at 88 like the other ones. I swapped the injector back to the rear TB. I think that's the culprit because it was spraying almost directly onto the throttle plate and not the bore.
Next time I am also going to hook the fan up to EBL. I am using the stock fan switch and that doesn't kick on till 225F. So most if not all of the runs I did were in the 205+ temp range. Motor definitely likes temps in the mid 180s to 190, max 200. I think that cost me. Also, been playing with the tune again and found that I can pick up an additional 1mph/sec. if I drop the WOT AFR to about 12.6. At the track it was running in the low 13s. I like to use the Dump Log in EBL and see the how the car accelerates every second thru the WOT run. I usually do this from a 3rd gear punch coming off an entry ramp.

ben73

Dom,

FWIW, and I know every combo is different, but I raced mine last week and tried leaning it at WOT from 12.5-12.8 to 12.8-13.0 and it went 4mph slower right away! Iput that fuel straight back in :-) I also remember whem it was on the dyno, there was only something like 6-8hp gained by leaning from ~12.0's to 12.5..

liquidh8

Hopefully you'll get the richness figured out, I think using the EBL for fan control would help also. My Taurus fan is hooked up to the EBL so I had a good 195d engine temp, but inlet air temp was 120d or so, I ran it in the end of july. I was stiffling hot and bad humidity. Keep tuning and keep us posted. At least your are getting faster. The military has kept me bust the past few weeks so no tuning for me, or driving it for that matter.

Dominic Sorresso

Ben,

I think your experience and mine are spot on. Interesting that our results appear to be similar even tho you're using the Xram and me, the modded Xfire. As the AFR gets richer, the car accelerated at a slower pace. I would expect it to slow down as I get into the 5000rpm range and above, but it will nose over pretty quickly if its running too rich or too lean. In the mid 12s AFR, MAP dropped only from 98kPa to 96 thru the entire run and it was still accelerating at 5-6mph/sec rather than 4mph/sec in previous runs. Over the course of a 13 sec race, that could mean a significant improvement in trap speed.
Maybe someone like RBob or Grumpy would chime in on their experience. I started playing with 12.6 AFR because RBob told me I should compensate for the 10% Ethanol mix (corn syrup) we use here in the Midwest USA. In fact, I have Stoich set at 14.3 in EBL just for that reason.