been struggling with low mph for about 2 yrs now. I cant really figure out why my mph is so low. Car dynoed 456 whp I believe that was uncorrected and maybe 445 corrected. Several people have tried to figure out why its so weak past the 1\8. It has strong 60' heres my run from last night:
1.432 - 60'
4.343 - 330'
6.826 - 660'
99.00 - 660’ mph
8.969 - 1000'
10.789- 1320'
122.48- 1320’ mph
Last week it ran 10.81@124.08 which was the fastest mph ever. before that 123.11 was it. Some of my theories were that the converter was keeping mph down because of slippage but stock converter best mph was 121.25(and no under hood changes have been made) so it actually improved alot with the higher stall. I thought maybe the convertible top might be the culprit but I see other verts running better MPH. Its not the DA because I have run in everything from 3000DA to 1100DA. The car weights 3465ish with me in it( weighed it Sunday) It seems to go rich from 1\8 to 1\4. Some people have mentioned that the timing pods could perhaps be off but I would think that IRP would have a consistent routine in setting them up.....and my car has always had weak mph ... even stock. I'm running 28 degrees timing all the way down the track with no KR. I haven't lowered it because my experience from all my other cars has showed a loss of mph with less timing. I also havent raised it because I hear 28 is pretty high for a ls3 headed LS2. Anyone have input on this? I know ET wins races but I'm sure just about everyone here will agree that while this thing runs great to the 1\8 that its just plain weak in 3rd gear. My logs show that I run the whole last 1\8 in third gear. 60' times are BETTER than I could've hoped for but if I can find the missing mph I might have found the missing HP that might help the first 1\8 as well. I'm open to theories and opinions and past experiences from all of you

 

the only other thing i can think of is the converter isnt locking or the trans is sliping in third gear

 

sounds like a job for vararam

 

Even with the MPH, the ET is very nice.

Edit - Wow, just saw that it's a vert and has a pretty high raceweight...drop some pounds and that car will fly.

 

Is there a possibility that fuel pressure might be going up as the RPM stays higher for a steady time in 3rd gear? anyone know if I can log fuel pressure in HP tuners?

 

I am still learning on my car but Friday i put down a 6.9 1/8 mile @108 mph with a 1.79 60'. This Friday we will data log each pass to see what the car is doing. Any suggestion as to what I should be looking for? Mike at Century built my trans and tuned it. I know I also have a new engine but I can tell my trans works much better. He runs the line pressure at 259psi and I no longer have any slop or weak shifting. It is a progressive tune so when the wife drives the car it feels factory but once you go past 40% power it starts the shift harder and harder. My converter does not lock up under full power but it does lock it 6th gear. I run a PTC converter. I also shallow stage.

 

Nice time and run !! I have exactly the opposite problem, but dont have the experience and knowlege you do to figure it out. Stock converter and ran a 128 mph but only 11.5 et. I guess I need to get my 60 down like yours.

 

Not sure if its any heavier than other power top verts. I weigh 170. I weighed it sunday at the nmca/lsx race in Indy. with the check gauges message because I was about to run out of fuel it weighed 3405. I put 8 gallons of shell 93 in it when I raced it. the 3475 is an estimate because I didn't have my laptop and cables etc in the car for the 3405 weight

Crow with that 1\8 mph when you get that thing figured out you might be knocking on 9s

Real canuk you need to throw a yank converter in there. My best time stock converter and 3.15 grs was 11.69 now with yank and 3.42 10.78 (and I know there is more in it)

 

I dont know the weight of my car. Its a power top vert. I weight 200, I dont remove anything from the car and the eforce adds weight too. My 128 mph run was with half a tank of fuel. STock wheels which are heavy also. I dont see how the difference could be weight. Horsepower maybe ??

 

I am going for broke tomorrow night. I will either be a hero or a zero. 12psi in the back tires, john force burn out and hold on. I will either get traction or put paint on the walls as I go down track.

 

crow what tires are you running?. I have 275 40 17 hoosier DRs
last night at 20psi I had 1.440, 1.432, 1.440, 1.449 60's If you are running these Im not sure 12 psi will do it. You can run too low a pressure and the contact patch will "cup" into the tire and have less traction

 

315/35-18 toyo TQ proxy drag radials on 18x10.5 wheels.

 

i doubt it would go higher even with a boosta pump,

 

It could be the timers at the track if it's been that way all along, have you ran it anywhere else? How many miles on the valve springs and what CAI are you running? Congrats on the new best it sure moves out well!

 

it has always trapped low. When it was stock my best was
12.93 @108.02 when my friends 05 coupe went 110.25 .
then I did exhaust and vararam and started tuning a lil and it ran
12.27@114.5 which I thought was respectable for the changes.
Then I went L92\L76 and and cam and springs it went 11.69@121.25(best)kinda weak mph but it was stock gears and converter.
I put 3.42 gears(had 3.15 factory) and a yank 3400 it went 11.23@ 121.6
then ss4000 yank and it went 10.78@ 122.5 1.432 60' (last week went 10.81@ 124.08 1.450 60')
It has a vararam
I noticed yesterday that my front tires were BALD badly on the inside 2 inches or so(both of them). Maybe excessive negative camber or maybe a ton of toe out. I now need new tires before I can run it again. Not sure if this could scrub off 2-3 mph at the 12x speeds. Anyone have info on that???
Let it be known that my best 60' of all before gears and converter was 1.901(dead hooking) and now I have been 1.432.... over 4 1\2 tenths the first 60'!!!

 

with that info i believe the alignment is the problem, find a place that can do a 1/4 alignment

 

The scan will give big clues.

If your MAP is lower than say .99 or .98 you've got an intake restriction.

You can log transmission slippage too, I'd suggest you do that. I'm not an automatic guy but I've seen it scanned. Subfloor would know what to tell you to scan for that.

 

my map dances around 95-96kpa in 1st n 2nd then it dances 96-97kpa in 3rd gear. It probably hits 98 twice in the whole run for a msec. I just looked and it idles at 59-61

 

Thats a little low. Mine is .99 to .101 with my vararam. .60 at idle.

What kind of air cleaner do you have?

 

I think its the stock vararam one.... green if I remember right. If I had that high of a map it would almost be boost! lol

heres a pic of the worst of the 2 front tires. Kinda scary that you cant see it while on the car
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