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Thread: Jeff Green Impala
03-28-2017, 01:58 AM #31
Private question came up "Why is the MPH so high for no better ET than you are posting?"
Good question!! It is again because of the weight. Because the car is so heavy it takes far more HP to move it. So if it leaves at 1.2 60 foot times than it takes 400 HP more than a car that's even 1000 pounds lighter that also leaves at a 1.2 60 foot. That HP difference won't show up at the starting line because of the weight being much more. But when you get the weight moving that HP now shows up big time in the MPH at the other end of the track. So heavy cars will always need more MPH for the same ET a much lighter car requires. You do this long enough and I can almost tell you want a car weighs just by it's ET to MPH in a quarter mile. This is also why it will need to be in the 170's MPH to have any chance of even a high 7 in the Impala, because of it weighing almost 4600 pounds.
I'm a story guy and the best one I have to explain this was maybe the closest race I ever had. The other car was a 69 Camero with a big block and we were side by side the entire track until just about the 1000 foot make. All the sudden he just let off and I couldn't figure out why he did that. I had no idea why that was so you just go back to the pits and continue on. Soon enough a guy came over, that I did know, and said "you know that Camero you just ran, that was my uncle. As I started to tell him that was the best race I had ever had until he let off. He smiled and said "He didn't let off". My response was yes he did, he had to have!! He said his uncle came back and said " That dam Impala went 155 MPH" because he had the other side of the time slip. That was the best example of what happens when the other car runs out of HP or really torque. The power needed to move my much heavier car only makes it equal the lighter car until the much higher power takes over on the big end of the track. That's why the MPH is so high for the ET.
My joke has always been if you're not ahead of me at the 1/8 mile then your not going to catch me, that's been the case so far as I have never been passes in the big end of the track other than by a rail. And I still have hope at the 1/8 even if they are ahead of me because my power will show up. Guys got to have hope.
Or could be labeled as more reasons not to run a heavy car!! I really don't like going that fast as I'm very aware of how bad it will be if anything goes wrong.
Last edited by Jeff Green; 03-28-2017 at 02:02 AM.
03-28-2017, 12:32 PM #32LTX Member
- Join Date
- Jan 2017
- 1995 Roadmaster
- Quad Cities
You'll also see high mph for the ET on cars that don't 60' very well, like fwd street cars. I remember racing vs. a stock looking civic hatchback that ran 13.70ish at like 118 mph. I think he was doing the one wheel peel past the 660' mark lol. Another that comes to mind was an early 2000's Regal GS that was turbocharged - went 11.20ish at around 128 mph.
Friend of mine used to run Stock Automatic Truck class, he was limited to factory specs on the motor and used some sort of a cheater cam that still complied with the rules. He always found it funny that he had to add weight to go faster (less tire spin), used to put steel plates in boxes attached to the rear of the bed (~4k pound late 70's Dodge Ram). AFAIK his last record setting run was 13.13 at 98 mph, powered by a 'stock' 318 that he said only made 75 psi on a cranking compression test.
Very cool 'outside the box' Impala build sir, keep up the good work.
04-10-2017, 10:08 PM #33
Went to Bowling Green for the first test of the year. 1.3 sixty foot with a 3.7 330 foot and coasting to a 6.5 1/8 mile at 70 MPH. Best part of those numbers was the 3.7 330 mark. Needs to be 3.5 or better to feel good but pretty sure I had let off before the 330 based on the MPH for the 1/8. Glad I did let off as still showing lean on cylinder #1 so add more fuel. Also had an issue with the tranny sticking in first gear so that ending the day without a second test pass to see how the added fuel looked on the wide band.
Still work to do but happy overall as the car seems to like leaving at 1.3's better than 1.2's as no issues on the launch. Really wouldn't want the front end any higher than the 1.3's are leaving at. Lot's of changes over winter to the motor setup and they all seemed to work. But until it makes it the entire length of the track with no issues then it's far from saying it's all good. But get the fuel correct and it's good to the 330 at this point and most likely past the 1/8. Even with a full pass then it moves to reliability. Carried the front wheels out and I never had to correct the car at all, perfectly straight.
Last edited by Jeff Green; 04-10-2017 at 11:00 PM.
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04-25-2017, 01:25 AM #34
One step forward, two steps back.
Went to ORP two weeks ago with the following changes, added fuel to the launch and added fuel across the board above 5000 based on it showing lean on #1. Figured the others weren't far behind.
Car fell on it's face on the launch like a 2.6 sixty foot so that was the answer for where the fuel needed to be. Rolled into the throttle and it took off. But took out the #1 piston before the 1/8.
What I learned from that, and looking at everything in the motor, was it's still way lean across the entire motor. It wants a bunch more fuel above 5000. Intake valves say it and it even burnt some of the 2400 degree header coatings off. That's not paint out of a can but the same coatings the top fuel teams use here in Indy on their header tubes. It micro welded several of the top tool steel rings also. It all says too lean.
Positives: It only stuck aluminum to the cylinder and head. So a little acid cleaned it up like new. One new piston for #1 and four more for the micro welded damaged ring lands, new rings in all and one exhaust valve in #1. Added 26 pound larger injectors and a small bump on the fuel pressure. It wants a bunch more fuel and that means more power. Times were junk but I was racing a S10 pickup that ran a 9.2. Once I rolled into the throttle I was catching him like a rail. It's not a time slip but you can get an idea where you are at from little bits of data.
Negatives: The way I have to do this is a little tricky and to do so junks my tune up. 5000 plus at WOT will be there but it's like starting over on everything below that. My eight channel wide band may be useless at this point also. I'm working with a additive chemical company to come up with a way to make this run on unleaded. This is making the wide band numbers not what you think they should be and pushing them off the scale. So it may be back to old school with using the leak down gauge to know if your hurt anything and base your fuel adjustment off of that and what the motor parts are telling you. You can't read the plugs as they look like you just pulled them out of the box. Even the micro welded ring lands showed no signs of an issue on the plug straps.
Back to the track this Wed. and see where it is. As long at it runs above 5000 with no issues then the rest is just tuning below to get it back where it was. Get the top end right and the bottom should be easy, at least you're not going to hurt the motor doing the bottom.
Last edited by Jeff Green; Yesterday at 01:19 AM.