Ok, here is the situation. Ran 12.7-12.8's at 106-107 MPH at the end of last year with just a 4# lower, chip, and K&N filter. I had dynoed at that time at 398 rwhp. In January, had the blower ported by Apten and before I installed, got a reburn. I dynoed afterwards at 415 rwhp. A little lower than I expected, but ok. Went to the track and ran worse times, but the weather was a little warmer. I can deal with the ET's due to the weather...

Then at WFC, I finally got dyno tuned and put down 417 rwhp in an enclosed trailer with the hood down and no fan blowing on the motor in 100% HUMIDITY! Pretty crappy dyno conditions to say the least.

So last weekend I ran at the Midwest SVT Challenge and my ET's got somewhat better, but I am only trapping at 104ish??? My horsepower is indicative of at least a 107 mph trap speed, but I have not seen that MPH since BEFORE installing the ported blower.

I can't figure out why I have lost so much MPH at my current power level. Suggestions

 

I had the same problem. Last year trapped at 107mph and this year trapping at between 102-104mph? I did get a reburn but I am waiting till I go to the same track as I did last year to see if its the tune. I find that Lightnings are very dependant on a lot of factors and a 3mph change is not out of the ordinary.

However, given the fact that you are now running a ported blower I would have thought that your MPH would at least stay close to last years when you have a bad day.

 

I can't see the correlation between the HP and MPH in my case. Unless the blower is less efficient??? Doesn't add up and I can't figure it out

 

Are the mph figures measured the same between the different tracks?

Reason I ask is that I've been to some po-dunk 1/8th miles tracks who cheat thier lights a little to make them appear to be a little bit better track than some of the others in the area.
Rich

 

any other changes like slicks, or suspension mods.

The reason I ask is last year I trapped at a little over 124, but this year with better ET's I only trap at 122

The only change I made was in my suspension and better slicks.

Last year even with my race program and running more boost I could only 60' at 1.61 seconds.

This year with the new suspension/slick, and only running my street chip I was able to improve my 60' times to 1.501. Even running less boost and timing the improvement in 60' times dropped me over a tenth of a second. However with the better 60' times my mph slowed down 2 mph.

So if you improved the way either you or your truck launches, and reduced your 60' times your Et's will improve while the MPH will be less.

Edit I just looked at your gallery and saw this picture


New slicks I see what happened

 

I'm at work and have to deal with web sence blocking so I can't help with the slips right now, but same here Bro
12.8 @ 106, then later had 12.7's at less MPH.

On juice the 11.98 was at 113.98 MPH,
yet after the Ported Eaton (me the Wasp, and Gator the Apten)
WE BOTH RAN SLOWER ET'S
(And Gator was Dyno tuned before hand too)
Seems to be a pattern developing ???


BUT I will say my 12.0 at Cecil last month was at 113.5 MPH, so it does appear I lost ET, yet gained MPH (hence power) ? I should mention (it was very hot and sunny that day, and I was on pump gas so I can't blame the lost ET on the Ported Eaton, nor expect the numbers I got on that "oh so wonderful" cool fall day I ran the 11.98 "on pure racing fuel"

As said sooooooo much plays a part in a L's ET, many jump up and down as much as a full 1/2 second on any giving day

 

Also if you spin your tires off the line you will loos ET and pick up MPH

If you hook good(don't spin) you will pick up ET but loose mph.

Like Rob 0 said there are a lot of factors.

 

Same track...I only run at one track

 

Don,

I don't have the slicks anymore. I am currently running F1's again. This past weekend I was running 1.9-2.0 60 fts and last year 1.8-1.9 when I ran consistent 12's. So if I actually hooked worse last weekend, why did my MPH go down? According to your theory? +/- 1 MPH would make sense to change a little, but I have lost 2.5-3 MPH consistently the two times I have been to the track since the port job and am cutting very comparable 60 ft times. ET's are also suffering!

 

well then I don't know
something must be off in your tune.

 

I got my nittos back LOL!!!! (they were in the back of my truck at the cage place) so whenever you want to try them let me know.....

sorry I wasn't at the track this weekend....... but everclear was calling!!!!!

 

I was dyno tuned in hotter, more humid conditions to the same HP and came out a few horsies higher than I did before the dyno tune in cooler weather. So the HP is the same if not a little higher now. My shift points are set at 5,500 also.

 

Timing has a lot to do with mph. If the pcm is pulling timing for any reason, your mph will drop considerably. I remember adding boost and losting mph on my Eaton. If you get a race file, lock your timing and use race gas. That will allow for more consistant mph and ET's.

 

BINGO
This run was done with the most aggresive tune I ever had
and a simple open filter single chip, full weight, schitty track, hot day, and a 4lb pulley
(my first 12 back in 02)


Perfect example, MUCH MUCH better track, diff program,
added well over 1k in mods (Polished Accu Fab) JLP Box/New Filter, cool air induction lines, 6lbs of pulley in stead of 4, diff bars,
etc...



I think my prob's at Cecil this yr were heat and timing related
also, I even juice it with 18 degrees of timing, but my guess is the computer was pulling timing. When I ran the 11 in the mid 50's
I'm sure the computer was allowing much more timing.

Hey it's like anything I guess, you change one thing, and now you have to change another. It seems to be happening to me too,
LOTS OF US ???

But again I seem to have a decent MPH for my Mods, so now I just need to figure out what happen to that 2/10th's

 

I'll have to ask my tuner whether it can be pulling timing. When I had it dyno tuned, I saw the Excel spreadsheet with all the values. I was running 18 degrees throughout the pull and pegged at 21 degrees at one point