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| LS4 / F40 swap - fieroguru (Page 90/216) |
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fieroguru
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SEP 06, 06:34 AM
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Heading out to the LS Fest in the next hour.
Should have a good interstate run (Bowling Green is 2.5 hrs away) to check the interstate mileage with the open loop tune and the taller rear tires. Today I have to tech in and should get a few runs at the autocross and 1/4 mile.
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Trinten
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SEP 06, 06:58 AM
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fieroguru
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SEP 06, 11:17 PM
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The trip down the car averaged 29mpg again... breaking the 30 mpg mark is looking to be difficult.
On the first day of LS Fest, I was able to do ten 1/4 mile runs and six passes on the autocross track. Overriding theme is the car has too much power/not enough traction.
On the drag strip, I started out going though the water box, quickly nixed that idea as I would launch quicker w/o any pre-launch burn out. I also started out launching the car right off idle in 1st gear... Doing this I would still spin at the top end of 1st, which was hurting my ET and MPH. So I started launching in 2nd gear... slower out of the hole, but resulted in my quickest ET and mph of the day. Even launching in 2nd gear, wheel spin still happens as I feed it more throttle... need better and wider tires.
The major issue with 1/4 mile performance is the 2-3 shift... its like the syncro locks me out of the gear and I have to hold/apply pressure to it for well over 1/2 second for it to slide into gear and commence with the run. I am shifting at the same RPM (about 7k) but the 1-2 and 3-4 shifts both happen relatively quick. I adjusted the throttle follower torque to pull more torque so it would close faster early on with the tune. So its possible the engine is now dropping RPM too fast and passes up the RPM of the 2-3 gear shift before I get the shifter pushed up and over. The 1-2 shift has a larger RPM drop and the shifter is pulled straight back so there is more time to grab second and its a quick shift being pull straight back. The 3-4 shift is also quick... so I think I can just pull the shifter back quicker than forward and to the next gate over. So tonight I will tweak the throttle follower in the 4500-7K range to see if it helps the 2-3 shift by dropping RPM less quickly.
Best time of the day was 12.896 @ 114.10 mph... I know the car has more in it if I can get it to hook and speed up the 2-3 shift.
The 6 runs on the autocross were all steps towards a better time. 1st run I DNF'd as I missed the first cross over turn and the announcer came over the intercom "your going the wrong way"... 2nd run was 57.089 where I spun out on the back stretch, then 44.908, 44.784, 42.699, and 42.294. The best time of the day was in the 36 second range, so my times suck! I run the course in 2nd once I take off in 1st, but traction in 2nd gear is easily overcome in the straight line, let alone going around a corner, so less throttle lets the car go faster.
The car really needs a driver mod, wider stickier tires especially in the rear, and fix the 2-3 shift issue... but its been fun flogging the car!
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Will
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SEP 07, 11:14 AM
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Sounds like a blast. I need to take a Northstar to LS fest to clean up! 
What tires are you running?
The F40 has triple cone synchros 1st and 2nd, with doubles in 3rd and 4th. It's not surprising 1-2 is very quick. Test drives of the Saab in which the F40 debuted said that the test drives could shift gears as fast as they could move their arms.
You're not trying to shift clutchlessly, are you?
I've gone 12.86 @ 106, and have seen 11 sec timeslips with 112-114 traps, so traction is definitely the order of the day for you.
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fieroguru
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SEP 07, 08:41 PM
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| quote | Originally posted by Will:
Sounds like a blast. I need to take a Northstar to LS fest to clean up!
What tires are you running?
The F40 has triple cone synchros 1st and 2nd, with doubles in 3rd and 4th. It's not surprising 1-2 is very quick. Test drives of the Saab in which the F40 debuted said that the test drives could shift gears as fast as they could move their arms.
You're not trying to shift clutchlessly, are you?
I've gone 12.86 @ 106, and have seen 11 sec timeslips with 112-114 traps, so traction is definitely the order of the day for you. |
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Its been a fun yet tiring last couple of days.
The rear tires are 245/50/16 BFG G-force Comp 2s, the fronts are 205/50/16 kuhmos
My tweak with the throttle closing speed didn't do much, still having issues engaging 3rd with the clutch pressed. If I hold pressure on it, it will eventually engage, but it just takes way, way, way too much time. I will have to do some more testing when I get home to see what can be done to improve it.
Only made 2 more 1/4 mile passes today and they were both mid 13's at 108 due to spinning at the launch and the super slow 2-3 shift. I would have had 1 more round be we were in the elimination rounds - where you do 3 back to back passes and can not open the hood without being disqualified. After I picked up my slip for the 2nd pass, when I tried to leave I couldn't access 1st or 2nd. So I dropped out of competition and limped the car in 3rd gear all the way back to the autocross pits where my tools were. The C-clip for the shifter cable had fallen off allowing the cable sleeve stop to fall out of place. Luckily the c-clip was still on the transmission, so I just bent it in to make it fit tighter and slid it back into place...
The autocross side was a little better as I got 4 more runs in and was able to get down to a 40.982 as my best time. The best times were in the 35 second range, so I wasn't competitive (not that a fiero will ever be), but at least I was able to make some improvements.
I am waiting for some in car videos of the autocross and 1/4 mile runs to upload...
Only event on Sunday is a 3S.... Speed, Steer, Stop... full throttle bast to the end of the autocross track, turn 180 and come back and stop within a 20 x 30 box.
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Trinten
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SEP 07, 10:31 PM
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Sorry you had such trouble with getting into 3rd! At least you didn't lose the clip.
Personally I thought 40 seconds (compared to 35) was pretty competitive, but that's just me.
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fieroguru
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SEP 07, 11:14 PM
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Jims88
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SEP 07, 11:19 PM
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Best time of the day was 12.896 @ 114.10 mph... I know the car has more in it if I can get it to hook and speed up the 2-3 shift
That is still an impressive run!
Would a Posi-Traction differential of some kind make a difference?
When I did a search on the value of a positraction unit for a Fiero, it seems they're mixed opinions on the benefit it could provide?
In a transverse arrangement do both wheels hook up evenly, without a posi?
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fieroguru
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SEP 08, 06:14 PM
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| quote | Originally posted by Jims88:
Best time of the day was 12.896 @ 114.10 mph... I know the car has more in it if I can get it to hook and speed up the 2-3 shift
That is still an impressive run!
Would a Posi-Traction differential of some kind make a difference?
When I did a search on the value of a positraction unit for a Fiero, it seems they're mixed opinions on the benefit it could provide?
In a transverse arrangement do both wheels hook up evenly, without a posi? |
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Right now I hook & spin the rear wheels as a pair, so adding a posi wouldn't do much at the moment. If I get to the point of doing one wheel burnouts or spinning the inside tire around a turn, then maybe a posi would be in order.
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fieroguru
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SEP 08, 06:44 PM
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The 3S competition was a handful... Here is a picture of the course (2 cars run side by side, then turn opposite directions. Then switch sides and the average time for both decides the winner - bracket elimination):
During the practice rounds I started with a 16.623 for my 2nd time (spun out at the end for the first one and didn't get a card). Then ran a 15.957, 15.945, 15.926, and my last round was 15.230. The pro cars were running 13's, so it wasn't terrible. Tires, tires, tires...
I say it was a handful because I launched in1st, shifted to 2nd about 6000 rpm (at rev limit in 1st at 1/3 the way to the turn), WOT in 2nd, off the throttle, on the brakes, downshifting to 1st, tight turn (which I had to do 1 handed if I didn't get the shifter into 1st gear in time), give it hell in 1st, shift to 2nd and blip on/off the throttle as I went around the cones, then on the brakes again and stopping in the box.
There were only 62 cars there today and I was in round 1 of the eliminations. Got beat, packed up my stuff and went home to the A/C! Time to kick back and relax for a few hours!
I filled up once I got to LS fest, then put 120 miles on the car before filling up to head home. During those 120 miles, there were:
37 mile True Street Cruise... right before the 3 back to back 1/4 mile runs (no opening of the hood post cruise or between runs).
12... 1/4 mile passes
10... autocross passes
8..... 3S event runs
Used 11.2 gallons in that 120 miles, so it was drinking like a V8 with a 10.7 mpg average for that tank. Haven't filled up to check the return mileage yet.
I am please to say that in all my autocross and 3S rounds, I never tagged a cone, so for the most part the car went where I wanted it, just took A LOT of steering wheel and throttle work.
Overall it was a blast! I beat the piss out of the car and besides the C-clip falling off, it was issue free from a reliability standpoint. I got to hang out with J Gunsett and his son, did a heads up LS4/F40 vs LS3/F40 on the strip, even lined up against his son in his camaro for 1 run as well, I learned a lot about the car, found some areas that need further work, learned some of the details of how the event was ran, so when I go back next year I can do better.
Now I need to get back to Vince's car![This message has been edited by fieroguru (edited 09-08-2013).]
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