Twin Turbo Tune Diary
Sunday
4 March 2001
Idle and cruise temp was around 710.
Gradual acceleration felt strong to 5psi then starts to pop and
slow down.
Hard acceleration temp was around 1100.
Spark plug gap was 28 thou, plugs were black but still clean.
Some had grey/white electrode tips.
Fuel pressure set at approx. 9psi
Front jets = 82
Rear jets = 94
Timing = 28 degrees
It's not easy keeping an eye on all those guages
Wednesday
7 March 2001
No EGT
Same Fuel pressure, plug gap, jets
All plugs were black and slightly wet, because of idle and cruise
Timing = 24 degrees
Idle mixtures were slightly increased
Float levels were slighlt increased
Again gradual acceleration had to be used, as it backfired and
splatted on hard, instant acceleration (50cc sec pump to be
fitted to try and fix)
Pulled hard and stayed at 7psi and 5000rpm if acceleration
gradual.
Sunday
11 March 2001
No EGT
Increased fuel pressure to 11psi
Timing = 24 degrees
Same jets, plug gap
Float levels set to just spilling out of sight plug hole
Moved pump cam screw to position 2 on front and back
Instant hard acceleration causes slight delay, than boosts and
pulls with a slight pause around 4500-5000
Boost up is significantly harder, louder and quicker.
Slight increase in idle mixtures, enough to set a good idle
(which is slightly high when engine is hot)
Sunday
18 March 2001
No EGT
Installed clear-view sight plugs, adjusted rear float level
slighlt higher than front
After mucking around with the car all day Saturday, when it came
time to go for it's maiden voyage that night, it idled rough,
vibrated in drive and would not go under load. Spark plugs was
the thought, but at 10pm on a Sat night, we would have to wait
til morning. Sunday morning installed the new you-beaut NGK B7FS
plugs as recommended by JR and Ben, but it still wanted to carry
on, so we went jet-skiing to have a think about things. Upon our
return, and check of the fireing order, it was discovered some
dickhead (re: me) had put the number1 and 3 spark plug leads on
the wrong plugs. Doh!
This fixed, a quick blast around the block (during which time J
Marie was introduced to the sneezing car), produced better
results but still found hesitation and slight popping under
initial acceleration. Upon return and a lift of the bonnet,
visual inspection showed that the exhaust manifolds were red hot,
and engine temp was in the 'you don't want to know' area.
Still a bit lean we think.
Ben and I reminiscing over those bloody plugs and leads.
Friday
23 March 2001
Cruise temp was around 700
Hard acceleration temp got to 1050
Cruise temp at the end of the night reached 1025 at 2200rpm and
60kmh
Installed 50cc pump in secondarys
Front jets = 94
Back jets = 99
Timing = 24 degrees
PV block off in back, 4.5 in front
Plugs are black and sooty but not fouled, surprising considering
the amount of fuel.
Performance = All good!
Still a slight pause and occasional backfire midrange, will take
a look at fuel pressure, flow and a possible leak at the boost
reference port on the regulator.
Saturday
24 March 2001
No EGT
Installed 50cc pump in primarys
Same jets, timing and plugs
Adjusted float levels and idle mixtures
All problems solved...or so we thought. After installing the
other 50cc accelerator pump in the front, the test drive provided
more wheelspin than we've had so far, no pause in acceleration
and a bloody awesome drive. So we took it out for a cruise to the
local hangout, where engine temp seems to rise above 180 just as
we get to wherever it is we're going, and just keeps going up
until it is switched off. Bonnet vents and another pair of
electric fans will hopefully solve that problem. But on the way
home, a quick stab began as it did earlier in the night, but
produced a backfire and pause like the car had done previously
before the front 50cc pump had been installed. Now this got us
thinking that there is no way that this thing cannot be getting
enough fuel, after all it had run beautifully earlier in the
night, and then Ben came up with the suggestion that after all
the cruising around, underbonnet temperatures had heated up the
air intake pipes and fuel lines to the point where the intake
charge was too hot and the backfire occured as a result of it
leaning out. Evidence to support this could come from the fact
that when we got home (20min journey) the intake pipes are too
hot to touch, the fuel lines to the carby are very warm as is the
swirl pot in the boot as well as the change in cruise EGT's
reported the night before. Next project is cooling the charge and
the engine bay.
Sunday 29 April 2001
Finally found out what was wrong with the bloody thing. At the beginning of the month, we had it running beautifully, then 2 days later, it wouldn't start. Played with it for two weeks. Had the dizzy checked, perfect. Tried coils, leads and plugs, perfect. Although, the plugs were full of fuel, so we thought I had a leaky carby. Pulled it apart and put new gaskets in. Checked power valves to see if one of the big back fires had destroyed it, and to be safe put a block off in the front as well, so it was blocked front and back to eliminate a leaky power valve problem. Pulled the float levels down so that it couldn't possibly be leaking from too high a float level and set fuel pressure at 6psi. Still wouldn't start.
Put one of Ben's carbys on and with a little playing with the timing it started and ran. Quickly put my carby back on, it starts first go and two days later runs the doors off a pissy little rotarty, and spins the tyres through third.
Yet, another couple of days later it carried on like it did a month earlier. Lifted the carby up with the fuel lines connected, and without any pumps on or throttle movement, it was leaking like a sieve from the secondary butterflies. You can't see it from the top though. So she was boxed up and sent back to the carby shop for fixing, hoping to be back by the end of the week.
In the meantime, I've rubbed the bonnet back where the paint blistered above the passenger side manifold, and used the grinder to shave a couple of mil off the pipe. Hopefully that won't happen again. Ordered a set of bonnet vents to try and extract some of the engine bay heat and installed a cool can in the boot to try and chill the fuel a bit. I wanna race very soon.
Tuesday 5 June 2001
Been a while since an update, mainly due to uni taking up most of my time. Done a few things, mainly the addition of a air bleed valve to enable us to run more boost. We thought it was worth a try since we already had about as much fuel as we could in the carby (94, 99 jets, 50cc pumps etc.) and the thing was running real fat. Over-rich we thought, so a few more pound of air might even things up a bit and maybe eliminate that terrible backfire mid-range, not to mention increase power a bit. Well, did she ever. JR adjusted the valve to where he thought we might get about 10psi, and I gave her a hit. Boost went straight to 15psi, no popping, backfires or other nasty noises and she went HARD! Still heaps of black smoke out the back, but I prefer that to the blue and white stuff I was getting about a month ago.
My only real drama now still revolves around cooling the thing when out cruising. Took the group A scoop off today before test driving and it made one hell of a difference. Carb hat was cooler, pipes weren't glowing red and I was able to give it shit and sit at the lights without it coughing coolant everywhere. Next trial is a modified hornet scoop that is in the pipeline to try and feed cold air on to the hat and over the engine.
Images shown on these pages are courtesy of Ben Jack and J Marie Wallbank photographic studios.