79 RX7 LS 5.3 Turbo. (8.93 @ 153mph)
05-03-2015, 12:07 PM
#301
9.0 vid from earlier in the day...
No clue, it's never been on corner scales. I'm sure that would make all the difference in the world. It's just a matter of time and money. I'd like to get the upper FWD ladder mounts accessible before heading to a chassis shop. That way they will have the adjustability they need at teh ride height I'd like.
do you know where the instant center is? and squat / anti squat geometry?
I have an excel spreadsheet that you could use to calculate that stuff, if you don't already have it.
send me a PM with your address and I'll mail it. I used it to design and build a triangulated 4-link in my truck.
Doug
I have an excel spreadsheet that you could use to calculate that stuff, if you don't already have it.
send me a PM with your address and I'll mail it. I used it to design and build a triangulated 4-link in my truck.
Doug
No clue, it's never been on corner scales. I'm sure that would make all the difference in the world. It's just a matter of time and money. I'd like to get the upper FWD ladder mounts accessible before heading to a chassis shop. That way they will have the adjustability they need at teh ride height I'd like.
05-03-2015, 07:42 PM
#303
Sold my turbo today.
Pulled the turbo. Then figured I'd clean/paint/polish it for the buyer.
Everything looks good right?
When I pulled the exhaust housing off to paint it, I found the aft blades were damaged.
Not sure what happened or how long I've been running the turbo this way.
Did pretty good for being damaged!
I'm assuming one of the old motors sent something through it and I never noticed. 
05-04-2015, 08:32 AM
#304
TECH Resident
You can measure the suspension pickup point heights and lengths of the bars and input those in to the spreadsheet. It will allow you to determine the force vectors on the rear end. This will allow you to optimize your setup without as much trial and error. In my experience, just 1/2" different height on one of the pickup locations, I found when designing mine, made a huge difference in the handling characterisistics in terms of rear steering (from bumps), and load on the suspension from acceleration and deceleration. All these attributes are basically at odds with each other.
The spreadsheet just has you inputting coordinates and it will calculate instant center, squat / anti squat, etc.
Here's an example of the spreadsheet input / output form.
http://www.zukikrawlers.com/albums/F...lts2.sized.jpg
And here's a quick article which explains it much better than I can. http://www.how-to-build-hotrods.com/tuning-4-link.html And this one is just a very simple guide. You could read for days.
The spreadsheet just has you inputting coordinates and it will calculate instant center, squat / anti squat, etc.
Here's an example of the spreadsheet input / output form.
http://www.zukikrawlers.com/albums/F...lts2.sized.jpg
And here's a quick article which explains it much better than I can. http://www.how-to-build-hotrods.com/tuning-4-link.html And this one is just a very simple guide. You could read for days.
05-04-2015, 09:19 AM
#305
You can measure the suspension pickup point heights and lengths of the bars and input those in to the spreadsheet. It will allow you to determine the force vectors on the rear end. This will allow you to optimize your setup without as much trial and error. In my experience, just 1/2" different height on one of the pickup locations, I found when designing mine, made a huge difference in the handling characterisistics in terms of rear steering (from bumps), and load on the suspension from acceleration and deceleration. All these attributes are basically at odds with each other.
The spreadsheet just has you inputting coordinates and it will calculate instant center, squat / anti squat, etc.
Here's an example of the spreadsheet input / output form.
http://www.zukikrawlers.com/albums/F...lts2.sized.jpg
And here's a quick article which explains it much better than I can. http://www.how-to-build-hotrods.com/tuning-4-link.html And this one is just a very simple guide. You could read for days.
The spreadsheet just has you inputting coordinates and it will calculate instant center, squat / anti squat, etc.
Here's an example of the spreadsheet input / output form.
http://www.zukikrawlers.com/albums/F...lts2.sized.jpg
And here's a quick article which explains it much better than I can. http://www.how-to-build-hotrods.com/tuning-4-link.html And this one is just a very simple guide. You could read for days.
05-04-2015, 09:34 AM
#306
TECH Resident
I see, bet you still can apply some principals. Ladder bar is simpler than 4 link as the front pickups are the instant center (when viewed from the side. (I think).
CG can be estimated. I read something that said CAM bore on a lightweight V8 powered car is CG height. Obviously, that is making some big assumptions.
Doug
CG can be estimated. I read something that said CAM bore on a lightweight V8 powered car is CG height. Obviously, that is making some big assumptions.
Doug
05-07-2015, 11:18 AM
#307
LS1Tech Co-Founder
iTrader: (34)
forcefed, a local chi guy is building a car like yours, could you email me your email so i can share with him? i'm sending him a link to this build thread too.
my email john@motorsports-media.com
my email john@motorsports-media.com
05-07-2015, 11:30 AM
#308
With the rear separating like that, you have too much anti-squat. You can get away with lowering the car more, which will bring the instant center forward and lift the front more than the rear. Ladder bar cars induce a ton of anti-squat naturally, so without mounting point adjustments, you can only use ride height to compensate. I would drop it down 1/2" and see how it hits. then go down in 1/4" increments until it starts kicking the tires off, then go back up to the last height it worked at
05-07-2015, 11:59 AM
#309
With the rear separating like that, you have too much anti-squat. You can get away with lowering the car more, which will bring the instant center forward and lift the front more than the rear. Ladder bar cars induce a ton of anti-squat naturally, so without mounting point adjustments, you can only use ride height to compensate. I would drop it down 1/2" and see how it hits. then go down in 1/4" increments until it starts kicking the tires off, then go back up to the last height it worked at
I made a few adjustments before heading to the track on Sunday. Dropped the shock mounting points down one notch and lowered/leveled out coil overs. (had a numbch of preload in the pass side coil over. This dropped it about 1.25”. I run a pan-hard bar so I don’t know if using un-level spring heights to adjust the launch is even a bad thing. I’m told it shouldn’t matter, but it irked me.
When I got to the track it pulled right again pretty good. So I added a flat of preload in the right bar until it quit pulling right. (took 3 flats) Still seemed to be topping out strut on my last pass. So I added 3 clicks on the aft shock "bump/compression" ****. We'll see how that goes next time. Waiting on the turbo to be repaired so I'll be down for a while. Trying to decide how much I should compress the springs at ride height. I’ve heard you want as much as 2/3 compression to “Store energy”. So my 12” spring should be sitting at 8” or so at ride height?
Would probably cheaper/easier to just stick a 33x14 tire under it instead of tearing into the ladder mounts and taking the car to a chassis shop. It will raise the car up and fill out the wheel well better too.
Thanks
06-24-2015, 09:56 AM
#312
Went to the track Saturday night with the new turbo. Installed a new cam as well. It trapped the exact same MPH at 15-16lbs as it did previously. Back pressure on average was only 3-4psi lower with the larger 87/96 wheel installed.
Went with a Howards 224/224 @ 113. .610 lift. Car pulls to 6500 now and is more responsive out of boost. No noticeable difference other wise. New cam doesn't' have any noticeable lope. (@ 950 rpm anyway.) Cranking compression did jump up almost 20psi. This could also partly be due to all the plugs being out of the motor and higher cranking RPM.
Air was pretty bad and it was crazy crowded. "Midnight drags" 10pm to 3am! Only got 3 runs in. 2 at 15lbs creeping to 16ish and 1 run at 20 that spun out of the hole and at half track. First 2 runs were almost identical 9.2X @ 150. Car feels no stronger.
Basically traps the exact same at the same boost level as the old turbo.
Got a few cell phone vids.
This was the last 20psi run. Looks like it picks up the driver wheel a little, settles back down, then picks up the wheel again. Also went from 4200 to 4500 on the 2-step here.
These are the 9.2x runs. 4200 2-step and 4-5lbs launch.
Went with a Howards 224/224 @ 113. .610 lift. Car pulls to 6500 now and is more responsive out of boost. No noticeable difference other wise. New cam doesn't' have any noticeable lope. (@ 950 rpm anyway.) Cranking compression did jump up almost 20psi. This could also partly be due to all the plugs being out of the motor and higher cranking RPM.
Air was pretty bad and it was crazy crowded. "Midnight drags" 10pm to 3am! Only got 3 runs in. 2 at 15lbs creeping to 16ish and 1 run at 20 that spun out of the hole and at half track. First 2 runs were almost identical 9.2X @ 150. Car feels no stronger.
Basically traps the exact same at the same boost level as the old turbo.
Got a few cell phone vids.
This was the last 20psi run. Looks like it picks up the driver wheel a little, settles back down, then picks up the wheel again. Also went from 4200 to 4500 on the 2-step here.
These are the 9.2x runs. 4200 2-step and 4-5lbs launch.
06-25-2015, 01:30 PM
#316
LS1Tech Co-Founder
iTrader: (34)
Nice updates.
Do you use a boost controller? I think at your vehicle weight with as much tire as you can run, you could shorten the ramp rates and bring the boost in quicker to go after some 8.5's.
Do you use a boost controller? I think at your vehicle weight with as much tire as you can run, you could shorten the ramp rates and bring the boost in quicker to go after some 8.5's.
06-25-2015, 02:15 PM
#317
I’m sure your right. I bought the wheel speed sensor over a year ago and have been too lazy to wire/figure it out.
Irks me a little to have to ramp in boost on a race track though. You’d think with a 12/29 slick on a “good” track surface with a “good” suspension setup I’d could dump boost in as quickly as possible. Guys making twice the power I am on 275 radials. Weight distribution I’m sure plays a big part. This chassis would be great for a 10.0 car. I’m fighting against myself trying to make it an 8 sec car.
Irks me a little to have to ramp in boost on a race track though. You’d think with a 12/29 slick on a “good” track surface with a “good” suspension setup I’d could dump boost in as quickly as possible. Guys making twice the power I am on 275 radials. Weight distribution I’m sure plays a big part. This chassis would be great for a 10.0 car. I’m fighting against myself trying to make it an 8 sec car.
06-25-2015, 08:51 PM
#319
8 Second Club
06-26-2015, 08:29 AM
#320
I mis-read your original post… thought you were suggesting I add progressive control. I do not run any progressive control at this time. I had it hooked up on the old 5.3 setup for street driving, but I always ran “all out” at the track.