So there is a fair bit to update here especially for those not on Facebook.
After breaking the front uni a necessary evil was having a new tailshaft made with bigger yokes and unis (Hardy Spicer 21R I think). The old tailshaft (which was actually a 3" 1 piece shaft I found at the wreckers in an R31!) weighed 6.5kg and the new one 10kg. While I was under the car I pulled the box and the clutch, and also figured while I have the money I'd finally get a steel flywheel so forked out for a very nice NPC one which has the capacity to take a 250mm clutch if needed. The old clutch had some wear but was only 2 years old so that went back in. My brother had a RB20det box he wasn't going to use so bought that off him and swapped the bellhousing over. There was really 'nothing wrong' with the FJ box apart from the usual sometimes dodgy synchros and just general noise - the output shaft splines had only the slightest of twist, but the RB box is supposedly better so it went in and only weighed about 1kg more with the L bellhousing.
After seeing the A/F readout from the gopro footage last time it looked like it was going a touch lean up top which I figured was the injectors maxing out (havent been able to data log for years but I know the duty cycle is right up there). I changed the fuel filter (prob 7 years old
) and removed a checkvalve I'd previously installed at the fuel pump because its all I could do to help the apparently marginal fuel system.
Well even though the static fuel pressure hadn't changed it must have been dropping up top because next time at the drags it was quite rich and costing lots of power, it averaged over a full A/F ratio richer and was only running 120mph even though I was taking fuel out. Still, got it to hook up to a 1.59 60' and ran 11.40.
Back home I rethought the fuelling strategy, and also changed the wastegate spring (still had a 10psi spring in it!) to 17psi because it never seemed to want to make over 25psi, figuring the wastegate was simply cracking open. Because I make the exhaust 'leak' at the drags by bolting a spacer in the dump pipe flange, the fuelling and boost parameters are quite different than on the street. Wastegate duty cycle dropped from 42% to 14% for the same boost with the new spring so it made a big difference and expected to have plenty of headroom for boost next time.
Also from seeing how the car would spin the right tyre on launch I put 1 then 2 turns of pre-load in the right upper rear control arm to try to get a straighter launch.
So back at the track last Wednesday, a checkout pass confirmed the fuelling was much closer, still only 25psi boost. But all night I was wasting passes because the geabox wouldn't let me into 3rd in the burnout plus for some reason I managed to change from 2nd to 5th! on 2 passes which I've never ever done before
Also was cranking wastegate duty cycle into it and not showing much boost change, only up to 27psi.
For the last pass I cut my losses and just did an angry 2nd gear burnout, concentrated on the launch and gear shifts and it went 1.67 to 60', slipped the clutch a bit through 2nd and ran 11.18@124.2.
We quickly hopped it back around for another pass with hopefully more boost and finally a little more timing in the higher rpm but the lanes were closed
After getting home I noticed the front bearing on the turbo is noisier (its 11 years old and has never had water cooling hehe) but it suddenly clicked that maybe the bypass/BOV (which is just a stock plastic EVO9 one given me by a friend) has been leaking above 25psi, especially as the pressure drop across the intercooler rises - explains why its so hard to make higher boost and meaning that going crazy with the wastegate duty cycle would have oversped the turbo and lead to hurting the bearing. The extra hot air recirculating into the compressor (plumback) wouldn't have helped power either
I'd thought about getting a decent BOV years ago but a proper 38mm dual port is $400
Video of the 11.18
https://www.youtube.com/watch?v=Gv8247Qp_TI
11.40 incar
https://www.youtube.com/watch?v=9a2yskd0u2A