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Picked up 2 8x4x2" Lead blocks. (52lbs). Trying to get some weight in the right places. Driver side with me in the car was about 60lbs heavier. So between this weight and my tool bag I'm pretty close now.
Popped the bumper cover off and I couldn't believe how perfectly the block fit.
With no preload on the ladder it drove right. 4 flats of preload and it almost went straight. Raised the pass spring perch until it went straight. It's a good 2" higher. So it went straight... until I turned the power up. With both wheels up it drives left hard.
No idea what will happen now. Plan to take the preload out of the ladder. Hope to get it within 100lbs front to back while getting the corners as close as I can. Then use the spring perches to balance out the rest. I'll adjust ladder preload at the track if I need to.
Cut up a door this weekend to get to the crash bar. Talk about a nasty miserable job for a lousy 12-13lbs worth of weight! Cut the ends off, then couldn't get it out of the door and had to cut it into two pieces. Got the passenger side to look forward to next weekend. JOY!
Last edited by Forcefed86; 01-26-2016 at 05:48 PM.
Complete noob at chassis tech, but some physics, so don't be cruel?
The weight transfer won't be as linear as you might guess even with the L-R weights matched unless the L-R polar center is fairly close.
My guess: the left-positioned driver in much closer F-R to the wheelbase center than the right-positioned offsetting objects (battery, ballast), which will have greater effect (rise more slowly) than his weight.
What to do about it?
T&T.
You may be able to reduce weight faster and with less effort just by eating right. lol
You've got it looking good under the hood, but man it's tight.
That was 26lbs or so with the door bars. If losing alot of weight was an option I'd do it. I'm not carrying much weight as it is at 6'4" and only 200lbs.
Don't have much chassis experience either. Just trying to get the weight on the rear wheels the same with the nose up at full travel and me in the car. I'll add or remove preload on the pass side bar as needed at the track. Think controlling the nose rise rate is the missing link to getting this chassis to hook well consistently. May have to fab something up if this doesn't work.
Think controlling the nose rise rate is the missing link to getting this chassis to hook well consistently. May have to fab something up if this doesn't work.
Double adjustable shocks enable you to control compression and rebound both.
Double adjustable shocks enable you to control compression and rebound both.
Right I get that, but the drag racing aftermarket for an RX7 is non-existent. I have double adjustables in the rear, but I'd have to fab up a way to mount a universal double adjustable shock. The Rx-7 uses a slip in cartridge assy that is part of the spindle. Figure If I go through all the trouble I'd just tube the front end.
Made it out the track this weekend. Only got 2 shakedown passes in before rain. Local gas stations keep changing the ethanol percentage on us. Picked up some 70% Wednesday and had the car pretty decently tuned. Filled up on the way to the track and must have got actual 85% ethanol. Car was crazy lean so I added a ton of fuel before the track visit. First pass 10 flat AFR with the auto tune pulling fuel the entire pass. Went 9.1 @ 156. Next pass was 10.8 AFR and 9 flat @ 158.8. Peaking at 17lbs same lazy 4lb launch. 1.46 60’. Leaving at 4lbs dead hooks and bogs, kills the ET. Takes too long to build boost leaving on 4 lbs. Air was humid and horrible.
Looking at the logs…
Leaving at 4lbs it took 1 full sec to build 11lbs.
Then the 3 second boost ramp rate. So stayed at 11lbs for 2 seconds, then took another second ramp up to 17lbs.
Was like a Sunday cruise out there. Slow launch and slow ramp rate. Car dead hooked and went nice and straight though. Hope to get an 8.5X pass this year with a more aggressive 12lb launch and 2 second ramp rate. May bump boost up to 19-20 for grins after I get the launch sorted.
Can see I pull the driver wheel an inch or so on the second video. Suspension is working for once and keeping me nice and straight.
Track rental didn’t go as planned, but made for some interesting videos. Cranked up the power on the launch from 4-9lbs and raised the 2 –step from 3400 to 3800. Ramping in boost over 2 seconds instead of 4. 1.32 60’ but it Pulls the driver side tire a good 3-4feet and tweaks the whole frame hard.
Pretty sure it’s my fault. Had some vibration after raising the rear for the larger tires. Adjusted the pinion angle per the chassis works instructions with the driver side ladder. Then adjusted the pass side ladder to a slip fit and added 2 flats of preload.
Went home last night after the track and pulled the shocks and let the rear hang. Driver side tire was touching the ground and the pass side was a good 4” off the ground! So I’m assuming I had a ton more preload on the driver side resulting in retardo crooked wheelies all day. I’m afraid of the thing after making this large of a change. But I’ll lay into it easy next visit.
Power is there though. I backed power down for the last pass of the day ramping on boost slowly again. 1.55 60’ 8.98 @ 159.9. 16lbs in 1st, peaked at 18lbs in 2nd at the end of the run.
Sometimes when leaving on way more power cars will want to wheelie. Chassis settings can help but there are times when strategically hanging some weight somewhere up front will allow you to use the power and not peddle.
Pretty sure I had the ladder bars all out of wack. I made some major adjustments. I'll have to wait until the next track outint to see, but I had a TON of preload on the driverside bar. Pretty sure this was causing it to lift the driver side much higher than the pass.
I'll bet your ladder bar adjustment will it most of the wheelie issues. Doesn't look like the car has a ton of front end travel, if it keeps doing power wheelies, tighten up the extension on the rear shocks.
Best part is Adam is competent and a quality low budget fabricator and tuner, he runs in the 8's for more time than most and his stuff does not blow up. Finally he is not a member of the engine of the month club.
01-09-2016, 07:16 PM
