Supercharging again...

[SHEEL]

HI all,
just updating on the progress.
It's FINISHED!!
i mounted everything up using the 32/36 downdraught weber already set up on my gem, routing the piping straight to a custom stainless plenum that fits where the air filter used to directly on top of the carb. a BOV was plumbed into the back of the plenum venting to atmo. fuel presssure is an issue in this set up tho, to do the set up properly i had to fit an early model gem electronic fuel pump to my tank feeding to any sort of fuel injection fuel pump, i used a VL commo one. a surge tank can also be set up at this stage if u like.
However, the required feul pressure to a wber is aroun 4 PSI at the needle and seat, and a VL commo pump pushes about 15 to 18 PSI which would normally blow straight through the needle and seat and flood the carby. In order to prevent this u must purchase a rising boost regulator. as far as i know there is only one type availabe which is the malpassi unit and it unfortunatly retails for around $200. ouch. i forked out but if any one else has any other cheaper methods feel free to enlighten me.
what this unit does is reduces the fuel press down to an adjustable level. obviousely we want that level to be 4 PSI then it senses the boost and adjustsso that the fuel pressure is slightly higher than the boost pressure to prevent boost pushing back through the fuel bowl into the lines. OK.
So I put the whole setup on and set the timing to around 6 degrees and fired her up. initially there werer heaps of boost leaks, so i pulled it apart and blocked them off one by one. the main leak was down through the top plate of the carb through the choke linkage. to rectify this i removed my choke and filled the hole with a piece of cork gasket and some high temp silicone. sounds dodgy i know but i did't want to weld the hole up so the choke can be reconnected if i want. also there were some leaks in my plenum so i had to put a few more welds on it.
so with that done i put it back on the car and tried again.
this time aorund it was much better. no leaks and running ok. I then took it for a drive and it didn't really drive well, which was no surprise coz i hadn't really tuned it at all yet. but this is the method i'm using to get it running initially , trail and error. when its running better i will dyno it.
ok so from my dirve i discovered a few things, it had a massive flat spot on acceleration, this was because the feul press was not set properly yet and the carby was flooding, also it was pinging at high revs so rejetting the secondary jet was in order.
so i went and bought myself a feul press guage and hooked it up and set the pressure to 4 PSI on idle, using the fuel press guage u can also see the pressue rise with boost so its very handy to monitor the reg.
next i rejetted the carb. i found my carb had a 135 primary jet and a 140 secondary, i first upsized them both but then my idle went shitty. and after a few attemptsi found the best combo was to leave the origional primary jet coz at low engine revs the is virtually no boost. then upsize the secondary so that when u give it gas and the boost rises. there is plenty of fuel there to match. my jet combo is now a 135 primary and a 155 secondary. also note in a weber for those who dont know there a fuel jets and air jets. i'm talking about the fuel jets here they are found inside the fuel bowl whilst u can see the air jets lookig down the top of the carby near the venturi.
Ok so after all that i've got the car runnin sweet as with only one more problem. when i had a v belt pulley made i used a pulley the same size as the toyota unit. it only makes around 4 to 5 PSI. this where i'm up to at this stage and using the info supplied by paul in "the lowdown on s/chargers" i'm going to measure the correct size pulley to run around 10 to 12 PSI. i'll update here in a few weeks after i've had the car on the dyno. It goes really well on just 5 PSI, probably would run a mid 15 sec quarter i feel. so i'm really keen to see what it will do on 10 PSI.
probably will just blow up knowing my luck!!!
pics avail. as soon as adam or joe post them in the galleries... showcars / Daniels TF, ( the tiger mica one)
thats all for now.
SHEEL out.
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